GOES-16 IFR Probabilities in AWIPS

Visible Imagery and GOES-16 IFR Probability Fields, 2202 UTC on 29 November 2017 (Click to enlarge)

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing

GOES-16 IFR Probabilities can now be displayed in AWIPS.  This site has included the product for several months now.  The imagery above, however, is from AWIPS, showing a toggle between Visible GOES-16 Imagery (with and without observations of ceiling heights and visibilities), MVFR (Marginal Visible Flight Rules) Probabilities, IFR (Instrument Flight Rules) Probabilities and LIFR (Low Instrument Flight Rules) Probabilities.  GOES-16 IFR Probability fields are Bayesian and have been trained using about 2 months’ worth of GOES-16 Data.  The LDM data feed will be providing data once GOES-16 Data are flowing again, sometime between 14 December and 20 December, when GOES-16 is on station at 75.2 º W Longitude.

GOES-16 IFR Probability, 0642-1137 UTC on 30 November 2017 (Click to enlarge)

Dense Fog covered parts of Florida early on 30 November, and the animated GOES-16 IFR Probability field, above, shows the benefit of GOES-16’s routine 5-minute temporal cadence:  the motion of the fog field is well-captured, and it’s straightforward to use the field to estimate the onset of IFR conditions.  The Advanced Nigthtime Microphysics RGB for the same time period is shown below, and that product does not well indicate the widespread nature of the reduced ceilings and visibilities over northern Florida.

GOES-16 Night-time Microphysics RGB, 0642-1137 UTC on 30 November 2017 (Click to enlarge)

Screen Capture for http://www.weather.gov at 1148 UTC on 30 November 2017 (Click to enlarge)

Dense Fog Advisories were widespread over the southeastern US on the morning of 30 November, as shown by the screen capture above, from 1148 UTC 30 November. The toggle below shows IFR Probabilities and the Advanced Microphysics RGB for 1147 UTC on 30 November.  The 10.3 µm – 3.9 µm Brightness Temperature Difference (BTD) for the same time shown at the bottom. Evidence of multiple cloud decks is apparent in the image. Such mid- and high-level clouds result in an ambiguous signal as far as fog detection goes in both the BTD and in the RGB. IFR Probabilities give a consistent signal in those regions that relies on Rapid Refresh Model output suggesting low-level saturation is present.

GOES-16 IFR Probabilities and the GOES-16 Advanced Microphysics RGB at 1147 UTC on 30 November 2017 (Click to enlarge)

GOES-16 Fog Brightness Temperature Difference (10.3 µm – 3.9 µm), 1147 UTC on 30 November 2017 (Click to enlarge)

Dense Fog Advisories over Memphis

Dense Fog Advisories were issued over Memphis and adjacent portions of the mid-south on Tuesday morning, 7 November. (Click here for a 1230 UTC screen capture from the Memphis National Weather Service webpage). The Advisory text is at the bottom of the post.

GOES-16 Brightness Temmperature Difference field (10.3 µm – 3.9 µm) from 0502 through 1252 UTC on 7 November 2017 (Click to enlarge)

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing

GOES-R IFR Probabilities are computed using Legacy (Operational) GOES (GOES-13 and GOES-15) and Rapid Refresh model information; Preliminary IFR Probability fields computed with GOES-16 data are available here. IFR Probability fields based on GOES-16 will be available via LDM Request when GOES-16 becomes operational as GOES-East (currently scheduled for some time between 11 and 20 December 2017).

The animation above shows the GOES-16 Brightness Temperature Difference Product (at every 10 minutes, rather than the typical 5-minute temporal cadence of GOES-16 over the continental US) during the night on 7 November.  In the default color enhancement shown, clouds made up of water droplets are show up as cyan and blue whereas higher clouds are black.  Note also the effects of increasing solar reflectance at the end of the animation:  the brightness temperature difference is switching sign as increasing amounts of 3.9 µm radiation are reflected off the clouds.

It could be difficult to use the animation above, alone, to heighten situational awareness of a developing region of fog because of the confounding effects of higher clouds.  Additionally, infrared satellite imagery is challenged to detect cloud thickness:  are the stratus clouds detected (cyan/blue in the enhancement) mid-level, low-level or both?

IFR Probability fields can screen out regions of mid-level stratus, regions that are not so important from the point of view of transportation.  This is because Rapid Refresh Model output is used as a predictor in the statistical model underlying IFR Probability fields.  If the Rapid Refresh Fields do not show low-level near-saturation, the IFR Conditions are less likely.

Consider, for example, the animation below of IFR Probability fields computed for GOES-13 data.  At the beginning of the animation, the fields clearly distinguish between regions where dense fog is occurring near Memphis, and where mid-level stratus is more common (over northern Mississippi).  As dawn approaches, reports of fog become more widespread over Mississippi — but the product has given a timely alert to how conditions might differ over a short region that was not possible with the single brightness temperature difference product alone.

GOES-13 IFR Probability fields, hourly from 0315-1215 UTC on 7 November 2017 (Click to enlarge)

GOES-R IFR Probabilities are available via an LDM feed to National Weather Service Offices. At present, IFR/Low IFR and Marginal IFR Probabilities (and Cloud Thickness) fields that are sent are those created by the operational GOES-East Satellite, GOES-13.  IFR Probability Products based on GOES-16 are being produced now, however, and are available here. The short animation below shows a behavior similar to the product based on GOES-13, but GOES-16 has far better temporal and spatial resolution!  Click here for a toggle between GOES-13 IFR Probabilities, GOES-16 Brightness Temperature Difference Fields, and GOES-16 IFR Probabilities at 0715 UTC.

When GOES-16 is operational as GOES-East, currently scheduled to occur between 11 and 20 December 2017, the LDM feed will supply GOES-East IFR Probabilities computed with GOES-16 data.

GOES-16 IFR Probabilities, 0402-0557 UTC on 7 November 2017 (Click to enlarge)

Suomi NPP flew over the region at 0740 UTC on 7 November, and there was ample illumination to see the clouds. Multiple cloud decks and levels are apparent below.

Suomi-NPP Day Night Visible Imagery (0.70 µm) Near-Constant Contrast Product, 0741 UTC on 7 November 2017 (Click to enlarge)

URGENT – WEATHER MESSAGE
National Weather Service Memphis TN
1228 AM CST Tue Nov 7 2017

…A Dense Fog Advisory is in Effect for Portions of the Midsouth
including the Memphis Metro Area…

ARZ036-048-049-MSZ001>004-007-008-TNZ088>090-071500-
/O.EXT.KMEG.FG.Y.0025.171107T0700Z-171107T1500Z/
Crittenden-St. Francis-Lee AR-DeSoto-Marshall-Benton MS-Tippah-
Tunica-Tate-Shelby-Fayette-Hardeman-
Including the cities of West Memphis, Forrest City, Marianna,
Southaven, Olive Branch, Holly Springs, Ashland, Ripley MS,
Tunica, Senatobia, Bartlett, Germantown, Collierville, Memphis,
Millington, Somerville, Oakland, and Bolivar
1228 AM CST Tue Nov 7 2017

…DENSE FOG ADVISORY NOW IN EFFECT UNTIL 9 AM CST THIS MORNING…

* VISIBILITY…Less than one-half mile.

* TIMING…Through 9 AM CST Tuesday.

* IMPACTS…Dense fog will most commonplace outside of the
Memphis urban center and near bodies of water. Travel may
become difficult due to limited visibilities.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

A Dense Fog Advisory means visibilities will frequently be
reduced to less than one quarter mile. If driving…slow down…
use your low beam headlights…and leave plenty of distance ahead
of you.

&&

$$

JAB

GOES-16 IFR Probability with Dense Fog in the Upper Midwest

GOES-16 IFR Probability fields, 0932-1157 UTC on 23 October 2017 (Click to animate)

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing.

Dense Fog developed over the upper Midwest on Monday morning, 23 October 2017, and Advisories were issued as shown below.  GOES-R IFR Probabilities are now being created using GOES-16 data, those data are now available at this link.  The uniformity of the IFR Probability fields shown above over WI suggest that high-level clouds are present, and the GOES-16 satellite could not therefore view the fog/stratus near the ground: only Rapid Refresh data were used to create GOES-R IFR Probability values.

GOES-R IFR Probability fields available to NWS Field Offices via LDM are still being computed with GOES-13 and GOES-15 data.  When GOES-16 becomes operational as GOES-East at 75.2º W Longitude, planned for December, IFR Probabilities available through the LDM will be created with GOES-16 and GOES-15 data. The switchover will happen when GOES-16 becomes operational.

Screenshot of NWS webpage from Sullivan, WI at 1200 UTC on 23 October 2017. Dense Fog advisories are in place from SW Wisconsin to NE Wisconsin. Note also the Radar imagery showing departing showers. (Click to enlarge)

Resolution and Fog Detection in the mountains of the Appalachia

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing.

Clear skies and light winds allowed for the development of Radiation Fog over parts of West Virginia and surrounding states early on Tuesday 17 October 2017, and IFR conditions were widespread (Source).

GOES-16 and GOES-13 both monitored this event, and toggles between the two brightness temperature difference fields, from 0315, 0415 and 0615 on 17 October, are shown below.  The better spatial resolution (and better precision) of the GOES-16 ABI is apparent in the imagery:  At 0415 UTC, GOES-16 is detecting river fog in many valleys in West Virginia and Kentucky, and is better resolving the detected fog over the Allegheny River in northwest Pennsylvania.  By 0615 UTC, the fog is also detected by GOES-13 — meaning it has increased in size so that the GOES-13 pixel size can detect it.  GOES-16 had a lead time of about 1-2 hours on GOES-13 in this case!

GOES-13 and GOES-16 Brightness Temperature Difference Fields, 0315 UTC on 17 October (Click to enlarge)

GOES-13 and GOES-16 Brightness Temperature Difference Fields, 0415 UTC on 17 October (Click to enlarge)

GOES-13 and GOES-16 Brightness Temperature Difference Fields, 0615 UTC on 17 October (Click to enlarge)

At present, GOES-R IFR Probabilities are created using GOES-13 data (or GOES-15 data for the western United States).  As might be expected, the GOES-R IFR Probabilities also lagged the GOES-16 Brightness Temperature Difference field in alerting to fog.  The short animation below shows values hourly from 0315-0615.  Very small IFR Probabilities are present at 0315 and 0415 — because, in part, the GOES-13 Imager cannot resolve the developing Fog/Stratus (and the Rapid Refresh model lacks the horizontal resolution to reproduce what is happening in narrow river valleys).  By 0515, and 0615 especially, GOES-R IFR probabilities are suggesting that a region of fog is likely.

One other thing to note:  There is a small signal in the brightness temperature difference field at 0315 UTC, above, in northwest Ohio in both GOES-13 and GOES-16 imagery.  There is no corresponding signal in the IFR Probability field.  The conclusion is that this is mid-level stratus that is not affecting surface visibility or ceilings.

GOES-R IFR Probabilities, hourly from 0315-0615 UTC on 17 October 2017 (Click to enlarge)

GOES-R IFR Probabilities, supplied via an LDM feed to National Weather Service Offices, will use GOES-13 (or GOES-15) imagery until GOES-16 is operational at 75.2 degrees West Longitude.  When GOES-16 is operational, GOES-R IFR Probabilities will use GOES-16 data, and that data will flow through the LDM.  In the meantime, GOES-16 IFR Probabilities can be viewed at this site.

Fog returned the following morning.  Link.

The GOES-16 Version of GOES-R IFR Probability

GOES-R IFR Probability fields computed using GOES-16 Data and Rapid Refresh Model Output, 1042 UTC on 3 October 2017 (Click to enlarge)

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing

The suite of GOES-R IFR Probability products are now being computed using GOES-16 data, with a 5-minute temporal cadence over CONUS.  Products include IFR Probability (above), Low IFR Probability, MVFR Probability and Cloud Height.  These products are only available for now at http://cimss.ssec.wisc.edu/geocat ;  however, work is progressing to have the fields available through an LDM feed.  The GOES-R IFR Probability fields computed using Legacy GOES (GOES-13 and GOES-15) continue to flow to the National Weather Service via the LDM.

IFR Conditions in Pennsylvania and Oregon

GOES-16 Brightness Temperature Difference (10.3 µm – 3.9 µm) at 0912 UTC on 2 October 2017 over the Mid-Atlantic States (click to enlarge)

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing.

The images above show the GOES-16 Brightness Temperature Difference at the same time at two places over the United States: The mid-Atlantic States (above) and Oregon and surrounding States (below).  The ‘Fog’ Product, as this Brightness Temperature Difference is commonly called, in reality identifies only clouds that are made up of water droplets — that is, stratus.  A cloud made up of water droplets emits 10.3 µm radiation nearly as a blackbody does. Thus, the computation of Brightness Temperature — which computation assumes a blackbody emission — results is a temperature close to that which might be observed.  In contrast, those water droplets do not emit 3.9 µm radiation as a blackbody would.  Thus, the amount of radiation detected by the satellite is smaller than would be detected if blackbody emissions were occurring, and the computation of blackbody temperature therefore yields a colder temperature, and the brightness temperature difference field, above, will show clouds made up of water droplets as positive, or cyan in the enhancement above.

The River Valleys of the northeast show a very strong signal that suggests Radiation Fog is developing over the relatively warm waters in the Valleys.  The Delaware, Hudson, Mohawk, Connecticut, Susquehanna, Allegheny, Monongahela, and others — all show a signature that one would associate with fog.  A signal is also apparent from southern New Jersey southwestward through the Piedmont of North Carolina.  Would you expect there to be fog there as well, given the signal?

The State of Oregon at the same time shows a very strong signal in the ‘Fog’ Product.  A clue that this might be only stratus, and not visibility-restricting fog, lies in the structure of the clouds — they do not seem to be constrained by topographic features as is common with fog.

GOES-16 Brightness Temperature Difference (10.3 µm – 3.9 µm) at 0912 UTC on 2 October 2017 over Oregon and adjacent States (click to enlarge)

GOES-R IFR Probabilities are computed using Legacy GOES (GOES-13 and GOES-15) and Rapid Refresh model information; Preliminary IFR Probability fields computed with GOES-16 data are available here.  These GOES-16 fields should be available via LDM Request when GOES-16 becomes operational as GOES-East.

GOES-R IFR Probability Fields use both the Brightness Temperature Difference field (10.7 µm – 3.9 µm) from heritage GOES instruments and information about low-level saturation from Rapid Refresh Model output.  The horizontal resolution on GOES-13 and GOES-15 is coarser than on GOES-16 (4 kilometers at the sub-satellite point vs. 2 kilometers), so small river valleys will not be resolved.  (It is also difficult for the Rapid Refresh model to resolve small valleys).

GOES-R IFR Probability fields at 0915 UTC, along with 0900 UTC surface observations of ceilings and visibility (Click to enlarge)

The IFR Probability Fields, above, show some signal over the river valleys of the northeast; that signal is mostly satellite-based, but the poor resolution of GOES-13 means that fog/stratus in the river valleys is not well-resolved. Still, a seasoned forecaster could likely interpret the small signals that are developing to mean fog is in the Valleys.  (And restrictions to ceilings and visibilities are certainly reported in the river valleys of the Mid-Atlantic and Northeast)   IFR Probabilities are also noticeable over southeast Virginia, although widespread surface observations showing IFR Conditions are not present.  (Such observations are somewhat more common near sunrise, at 1130 UTC).

IFR Probabilities are much less widespread over Oregon, with most of the signal over western Oregon related to the topography.  In this example, IFR Probabilities are ably screening out regions where elevated stratus is creating a strong signal for the satellite in the Brightness Temperature Difference field.

Dense Fog over Missouri and over Alabama

GOES-R IFR Probability Fields, Hourly from 0215-1315 UTC on 19 September 2017 (Click to enlarge)

GOES-R IFR Probabilities are computed using Legacy GOES (GOES-13 and GOES-15) and Rapid Refresh model information; GOES-16 data will be incorporated into the IFR Probability algorithm in late 2017

Dense fog developed over Missouri on Tuesday 19 September and Dense Fog Advisories were issued. The animation above shows the hourly development of GOES-R IFR Probability fields; values increased from northern Missouri to southern Missouri as dense fog developed, first north of I-70, then south into the rest of the state. The morning of 19 September was mostly devoid of mid-level and high-level clouds over Missouri (exception: west-central Missouri starting after 0900 UTC), and that kind of night means that traditional methods of fog detection work well. The brightness temperature difference field between the shortwave Infrared and the Longwave Infrared (3.9 µm and 10.3 µm on GOES-16, 3.9 µm and 10.7 µm on GOES-13) shows the fog development.

Note that the IFR Probability field, above, does not show fog dissipating around sunrise. That’s in contrast to the Brightness Temperature Difference field below. As the sun rises, the amount of solar radiation at 3.9 µm that is reflected off the clouds increases; this changes the brightness temperature difference from positive (cyan in the color enhancement shown) to negative (grey or black in the enhancement shown).

GOES-16 has better spatial resolution than GOES-13; thus, the small valley fogs that can develop in the rugged (ish) terrain of southern Missouri are resolved in GOES-16, but not in GOES-13. When GOES-R IFR Probability is created using GOES-16 data (slated to begin in late 2017), the resolution improvements in GOES-16 will migrate to IFR Probability fields.

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing.

GOES-16 Brightness Temperature Difference (10.3 µm – 3.9 µm), hourly from 0412 to 1112 UTC on 19 September (Click to enlarge)


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On 20 September, Dense Fog developed over Tennessee and Alabama, leading to the issuance of Dense Fog Advisories. The GOES-R IFR Probability field, below, shows good agreement between high probabilities and reduced ceilings/visibilities.

GOES-R IFR Probability Fields, Hourly from 0415-1315 UTC on 20 September 2017 (Click to enlarge)

As on the 19th over Missouri, top, this was a night with relatively few middle- and upper-level cloud decks. On such nights, the GOES-16 Brightness Temperature Difference field can capably identify regions of stratus (it’s up to a human to decide if the stratus deck extends to the surface; on this night, much of the stratus did). The 2-hour animation of Brightness Temperature Difference, below, highlights two particular strengths of GOES-16: Better spatial resolution that allows small valleys to be sampled correctly, and good temporal resolution (every 5 minutes vs. every 15 minutes for GOES-13) that allows superior monitoring of the cloud evolution with time. Note that the rising sun is eroding the GOES-16 Brightness Temperature Difference signal by the end of the animation below.

GOES-16 Brightness Temperature Difference (10.3 µm – 3.9 µm), hourly from 1002 to 1202 UTC on 20 September (Click to enlarge)

The Brightness Temperature Difference field (10.3 µm – 3.9 µm) is a key component to the Nighttime Microphysics Red/Green/Blue Composite. As the toggle below shows, the Brightness Temperature Difference field overwhelmingly controls the region identified by the RGB as one with a potential for fog.

Fog over southwest Lower Michigan

GOES-R IFR Probability Fields, 0330-1430 UTC on 14 September 2017 (Click to animate)

GOES-R IFR Probabilities are computed using Legacy GOES (GOES-13 and GOES-15) and Rapid Refresh model information; GOES-16 data will be incorporated into the IFR Probability algorithm in late 2017

GOES-R IFR Probability fields (From this site, but also available via LDM feed in AWIPS), above, show the development of dense for over Lower Michigan, leading to the issuance of advisories. IFR Probabilities on this morning remained fairly low over the relatively warm late Summer waters of Lake Michigan. There is also a noteworthy gap in Fog of unknown origin from Grand Rapids Michigan southwestward to Lake Michigan as fog forms on either side of that line. This is especially evident around 0845 UTC; the gap subsequently fills in as fog becomes more widespread.

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing

GOES-16 also viewed the fog field, from the top of the cloud deck, as shown below in an animation (courtesy of Nathan Jeruzal the National Weather Service Grand Rapids Office) of the Brightess Temperature Difference field (10.3  µm – 3.9  µm) for two hours before sunrise on 14 September 2017. A still image at 1117 UTC suggests that fog over Grand Rapids’ city limits was not widespread, perhaps due to slight warming in the city due to an Urban Heat Island that would reduce the relative humidity.

At the end of the animation, there is a consistent change in signal over eastern Michigan, from cyan indicating low clouds/stratus to grey, indicating no cloud, because of increasing amounts of reflected solar radiation at 3.9 as the Sun rises. The GOES-R IFR Probability field animation at top suggests that the fog persists through sunrise.

GOES-16 Brightness Temperature Difference fields (10.3 µm – 3.9 µm), 0947-1142 UTC on 14 September 2017;  City outlines are denoted in Yellow (Click to enlarge)

Dense Fog over the central Mississippi River Valley

GOES-16 Brightness Temperature Difference field (10.3 µm – 3.9 µm) from 0417 to 1357 UTC on 28 August 2017 (Click to animate)

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing.

GOES-16 Brightness Temperature Difference fields (10.3 µm – 3.9 µm), above, show the development of stratus clouds (made up of water droplets) over the Plains during the morning of 28 August 2017.  The Brightness Temperature for 10.3 µm is warmer than that for 3.9 µm during the night because cloud water droplets do not emit 3.9 µm radiation as a blackbody but those same cloud water droplets do emit 10.3 µm radiation more nearly as a blackbody would.   The conversion from sensed radiation to brightness temperature does assume blackbody emissions;  thus, the 3.9 µm brightness temperature is cooler where clouds made up of small water droplets exist.  The animation above shows stratus clouds developing over Missouri and adjacent states.  Dense Fog Advisories were issued near sunrise for much of the region (see image at bottom of this blog post) and IFR Conditions were widespread.

The animation above shows a positive signal over the western High Plains from Kansas northward to North Dakota. (Click here for the view at 1132 UTC on 28 August).

GOES-R IFR Probabilities are computed using Legacy GOES (GOES-13 and GOES-15) and Rapid Refresh model information; GOES-16 data will be incorporated into the IFR Probability algorithm in late 2017

How did GOES-R IFR Probability fields capture this event? The animation showing the fields every 30 minutes from 0215 through 1345 UTC on 28 August 2017, below, shows the development of High Probabilities in the region where Dense Fog was observed. There is a signal along the western High Plains, but it has low Probability; a conclusion might be that thin stratus has developed but that the Rapid Refresh model does not suggest that widespread low-level saturation is occurring. As the sun rises, the signal over the western High Plains disappears. Click here for a toggle between the GOES-R IFR Probability and the GOES-16 Brightness Temperature Difference field at 1115 UTC.

GOES-R IFR Probability fields, 0215-1345 UTC, 28 August 2017 (Click to enlarge)

Screen Capture of http://www.weather.gov at 1300 UTC on 28 August 2017 (Click to enlarge)

Dense Fog over Missouri

GOES-R IFR Probability Fields, and surface reports of Ceilings and Visibilities, hourly from 0315 to 1315 UTC on 15 August 2017 (Click to enlarge)

GOES-R IFR Probabilities are computed using Legacy GOES (GOES-13 and GOES-15) and Rapid Refresh model information; GOES-16 data will be incorporated into the IFR Probability algorithm in late 2017

IFR Conditions and Dense Fog developed over southeastern Missouri during the early morning on 15 August 2017, leading to the issuance of Dense Fog Advisories. GOES-R IFR Probabilities, above, showed increasing values as the ceilings lowered and visibilities dropped.  The IFR Probability fields over southern Missouri and northern Arkansas (and Kansas and Oklahoma) have the characteristic uniformity that arises when Rapid Refresh data alone are used to drive the IFR Probability values.  In these regions, high clouds (associated with convection over Arkansas) are blocking the satellite view of lower clouds.

Such high clouds will make it difficult for a satellite-only product to identify the regions of clouds.  For example, the Brightness Temperature Difference field below (10.3 µm – 3.9 µm) from GOES-16, color-enhanced so that low clouds are green and that cirrus (at night) are purple) shows widespread low cloudiness at the start of the animation, including some obvious river fog over Missouri (river valleys that are not well-resolved with GOES-13), but developing convection over Arkansas eventually prevents the view of low clouds.

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing

GOES-16 Brightness Temperature Difference field (10.3 µm – 3.9 µm), hourly from 0312 to 1312 UTC on 15 August 2017 (Click to enlarge)

Because the Brightness Temperature Difference field (helpfully called the ‘Fog’ Channel Difference in AWIPS) is challenged by high clouds in viewing the low clouds, RGB Products that use the brightness temperature difference field are also similarly impeded by high clouds.  Consider, for example, the stations in southern Missouri shrouded by the cirrus shield.  IFR Conditions are occurring there and a strong signal of that appears in the IFR Probability fields.

GOES-R IFR Probability computed with GOES-13 and Rapid Refresh Data, GOES-16 Fog (10.3 µm – 3.9 µm) Brightness Temperature Difference and GOES-16 Advanced Nighttime Microphysics RGB, all near 1115 UTC on 15 August 2017 (Click to enlarge)