Dense Fog in Illinois, September 12, 2020

Area Forecast Discussion
National Weather Service Paducah KY
308 AM CDT Sat Sep 12 2020

.SHORT TERM...(Today through Monday night)
Issued at 308 AM CDT Sat Sep 12 2020

A warm and murky night is unfolding across the region. Nearly
every observation site is reporting either fog, low stratus, or
combinations thereof. East-northeast winds of 5 kts or less have
prevented the formation of dense fog, but the potential is there
for some isolated dense fog to develop, especially around
daybreak. Will need to monitor trends for a possible SPS issuance
later this morning.

Unsettled weather is finally back after an extended dry spell.
We are following two features that will bring convection to the
forecast area. The first is a cold front that extends across the
Mid-Missouri River Valley south to the Texas Gulf Coast. The other
feature is a slug of tropical moisture that is advecting north
through the Mid-South. Timing wise, the front and the associated
precipitation will move into our SE MO and SW IL counties by mid-
afternoon into the evening. The tropical moisture will surge into
W KY and SE MO around the same time, and convection will blossom
and spread NE as a weak disturbance within the mid-level
traverses the Ohio River.

While instability is limited and mid-level lapse rates are meager,
there could be an isolated gusty thunderstorm late this afternoon
into the evening in SW IN, NW KY, or north of Route 13 in S IL,
where stronger shear exists thanks to the passing mid-level trof.
Locally heavy rain could occur as well, but given the antecedent
dry conditions, flooding should not be an issue.

On Sunday, the precipitation axis will shift to W KY and SW IN as
the surface cold front slowly clears the region. By 0z Monday, the
front and rain should be clear of the forecast area. Dry and more
comfortable air will arrive Monday as high pressure shuffles
south from the Upper Midwest. Can't rule out a stray shower Monday
in our far southeast counties with the front lingering nearby,
but confidence isn't high enough to include at this time.

High temperatures today will climb into the middle to upper 80s,
cooling a bit into the lower 80s for Sunday and Monday. Tonight's
low temperatures will only fall into the upper 60s to lower 70s.
Sunday night will be much more conformable with the less humid
airmass in place, in the upper 50s to lower 60s.

.LONG TERM...(Tuesday through Friday)
Issued at 308 AM CDT Sat Sep 12 2020

Will begin the long term with surface high pressure extending from
the nern U.S. westward back across the upper Ohio Valley. This
should bring generally dry and seasonably cool conditions Tuesday as
low level winds remain easterly in direction. Also, at this time, a
tropical area of low pressure that will likely be a strong tropical
storm or a hurricane, will be approaching the northern Gulf Coast
somewhere between the FL Panhandle and the Louisiana coastline.

Right now it is looking as though most of the effects from this
system will be shunted off to our south (over the se U.S.) as our
mid level winds become more northwesterly with time and a surface
front presses through the region later Thursday or Thursday night.
Ahead of the front, humidity and sct shower/thunderstorm chcs will
be on the increase Wed, and esp Thu, as a mid level trof approaches
from the northwest.

Once the front pushes farther south on Friday, we should see a
change to rainfree and much less humid conditions as Canadian high
pressure dips southeast into the Great Lakes region and

&&

.AVIATION...
Issued at 1154 PM CDT Fri Sep 11 2020

Main concern is the potential for development of low stratus and fog
through the early morning hours. The low levels remain moist, and
patches of stratus have continually formed early tonight. One patch
of ifr cigs between kpah and kevv at 04z is moving northward.
Looking at high resolution model guidance, the probabilities of ifr
conditions are highest in srn Illinois and se Missouri. The kcgi and
kmvn tafs will include a few hours of ifr around sunrise.

Whatever stratus and fog exists early Saturday will burn off rather
quickly, followed by sct to bkn cumulus. Some convection will likely
form in the afternoon ahead of a cold front. This will be handled
with vcts at some taf sites, however the timing and coverage of
storms will become more clear in later issuances.

Winds will be east near 5 kt, becoming south early Sat and southwest
by midday Sat.

&&

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

SHORT TERM...DWS
LONG TERM...GM
AVIATION...MY

Hazardous Weather Outlook
National Weather Service Paducah KY
427 AM CDT Sat Sep 12 2020

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-
100-107>112-114-130930-
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-
427 AM CDT Sat Sep 12 2020

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

.DAY ONE...Today and Tonight

Patchy dense fog is possible through mid-morning. Refer to the
Special Weather Statement for details.

Scattered to numerous thunderstorms are forecast this afternoon
and tonight. Locally heavy rain, isolated gusty winds, and
lightning are the main hazards.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Scattered thunderstorms are forecast Sunday, mainly across
southwest Indiana and western Kentucky. Locally heavy rain and
lightning are main hazards.

Isolated to scattered thunderstorms return to the forecast
Wednesday into Thursday night. Severe storms are not expected.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

Special Weather Statement
National Weather Service PADUCAH KY
425 AM CDT Sat Sep 12 2020

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-
100-107>112-114-121400-
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-
Including the cities of Mount Vernon, Fairfield, Albion,
Mount Carmel, Pinckneyville, West Frankfort, McLeansboro, Carmi,
Carbondale, Murphysboro, Herrin, Harrisburg, Shawneetown,
Jonesboro, Vienna, Golconda, Elizabethtown, Cairo, Mound City,
Metropolis, Fort Branch, Petersburg, Poseyville, Evansville,
Boonville, Rockport, Hickman, Clinton, Bardwell, Wickliffe,
Paducah, Mayfield, Smithland, Benton, Murray, Marion, Eddyville,
Cadiz, Princeton, Morganfield, Dixon, Madisonville, Hopkinsville,
Henderson, Owensboro, Calhoun, Greenville, Elkton, Perryville,
Marble Hill, Cape Girardeau, Jackson, Piedmont, Van Buren,
Doniphan, Poplar Bluff, Bloomfield, Sikeston, Charleston,
and New Madrid
425 AM CDT Sat Sep 12 2020

...Patchy Dense Fog This Morning...

Travelers this morning across the region should be alert for
patches of fog, some dense, along your route.

Be sure to utilize low beam or fog headlights while driving. Be
sure to leave enough distance between yourself and those on the
road around you, should you need to change lanes or stop.

The fog should gradually lift and dissipate by mid-morning.

Snyder