Dense Fog in Illinois, August 22, 2020

Area Forecast Discussion
National Weather Service Paducah KY
1230 AM CDT Sat Aug 22 2020

.UPDATE...
Issued at 1230 AM CDT Sat Aug 22 2020

Updated aviation discussion.

&&

.SHORT TERM...(Tonight through Sunday night)
Issued at 223 PM CDT Fri Aug 21 2020

Our trof with tropical origins continues to lift northward through
the Lower Mississippi and Tennessee River Valleys. Thunderstorm
activity associated with this trof so far today has been confined
to locations near the TN border. However, we anticipate that
convection will spread north into parts of southeast MO, southern
IL, and southwest IN through the afternoon into early evening.
With minimal shear and weak midlevel rates, not anticipating
anything in the way of severe convection. However, locally heavy
rain could cause isolated minor flooding issues. Thunderstorm
coverage will wane tonight with the loss of diurnal heating.
However, have maintained slight to chance POPs overnight over much
of western KY, which will be closer to the trof axis.
Additionally, with moisture advecting northward into the region,
fog will be an issue overnight. The greatest fog potential appears
to be over southeast Missouri and adjacent areas along the
Mississippi River.

On Saturday, convection will blossom again as the trof moves north
through the Lower Ohio Valley. Highest POPs (in the chance to
likely range) will stretch north from the KY Pennyrile into
southwest IN, with POPs decreasing going to the west. Our far
west/northwest counties will see little to no precipitation.
Again, we are not anticipating anything in the way of severe
weather, but locally heavy rain and isolated flooding are
possible. We'll dry out Saturday night as the trof exits to the
northeast and stay that way Sunday through Monday as high
pressure over eastern TN exerts its influence.

Overnight lows will fall into the middle to upper 60s. High
temperatures Saturday will be driven by clouds and precipitation.
Locations in southeast MO and southwest IL will climb into the
middle 80s. Places in western KY and southwest Indiana will see
highs in the upper 70s to lower 80s. Southerly return flow around
the surface high pressure to our east will bring a return of late
summer heat and humidity on Sunday and Monday. High temperatures
on Sunday will reach the upper 80s...followed by upper 80s to
lower 90s on Monday.

.LONG TERM...(Monday through Friday)
Issued at 223 PM CDT Fri Aug 21 2020

The Bermuda high and Western U.S. high are effectively squeezing out
the weak trof of low pressure still lingering down into/across the
Lower Ohio River Valley as we begin the long term on Monday. By Day
2 (Tuesday), a surface high has centered over the Tennessee River
Valley, as the Central U.S. ridge of high pressure becomes dominant.
These 2 features work in conjunction to produce an increasingly
hot/dry forecast through the mid/late week for us. We'll exceed
climo norms for temps/humidity, with 90s returning to the forecast
highs and dew points hovering around 70.

By days 4-5 (Thursday-Friday), we see a more active northern jet
stream eat into the strength of the aforementioned upper level
ridging so dominant over the Central U.S. It may be enough to drop a
weak front or boundary down into the Mid Mississippi River Valley,
but more interesting will be the first fetch of tropical/influence
moisture coming our way from now named TD14. Current model timing
suggests humidity/pops will be on the increase as its remnants move
in/up the Mississippi River Valley by late Friday (and into the
weekend). We might push the low 1 inch range of total qpf (by 00Z
Saturday) in our far southeast, if current modeling pans out.

&&

.AVIATION...
Issued at 1230 AM CDT Sat Aug 22 2020

Spotty IFR/LIFR cigs are expected mainly over western KY overnight,
and IFR/LIFR vsbys in fog are currently forecast near sunrise for
the western TAF sites where clouds should be less common. MVFR/IFR
vsbys are possible near sunrise for the eastern TAF sites.

Little shower activity is expected across the region until perhaps
late morning Sat in the east. VFR conditions should mostly prevail
Sat, but mainly eastern parts of the region will have scattered
convection around in the afternoon, along with the most clouds.
Winds will continue to be light and quite variable through the 24
hour TAF period outside of tstms.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

SHORT TERM...DWS
LONG TERM...DH
AVIATION...DB

Hazardous Weather Outlook
National Weather Service Paducah KY
226 PM CDT Fri Aug 21 2020

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-
100-107>112-114-221930-
Jefferson-Wayne IL-Edwards-Wabash-Perry IL-Franklin-Hamilton-
White-Jackson-Williamson-Saline-Gallatin-Union-Johnson-Pope-
Hardin-Alexander-Pulaski-Massac-Gibson-Pike-Posey-Vanderburgh-
Warrick-Spencer-Fulton-Hickman-Carlisle-Ballard-McCracken-Graves-
Livingston-Marshall-Calloway-Crittenden-Lyon-Trigg-Caldwell-
Union KY-Webster-Hopkins-Christian-Henderson-Daviess-McLean-
Muhlenberg-Todd-Perry MO-Bollinger-Cape Girardeau-Wayne MO-Carter-
Ripley-Butler-Stoddard-Scott-Mississippi-New Madrid-
226 PM CDT Fri Aug 21 2020

This Hazardous Weather Outlook is for portions of southern
Illinois, southwest Indiana, western Kentucky, and southeast
Missouri.

.DAY ONE...This Afternoon and Tonight

Scattered non-severe thunderstorms are expected, especially this
afternoon and this evening over western Kentucky, southwest
Indiana, southeast Illinois, and the Missouri Bootheel. Lightning
and locally heavy rainfall will be the main concerns.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Scattered non-severe thunderstorms are expected again on Saturday,
especially over western Kentucky, southwest Indiana, southeast
Illinois and the Missouri Bootheel. Lightning and locally heavy
rainfall will be the main concerns.

A chance of thunderstorms returns to the forecast Thursday and
Friday, with locally heavy rain and lightning as the primary
hazards anticipated.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

DWS/DH