Flash Flood Watch 5, NWS Lincoln, IL

Area Forecast Discussion
National Weather Service Lincoln IL
639 AM CDT Mon May 18 2020

.SYNOPSIS...
Issued at 257 AM CDT Mon May 18 2020

A large and slow moving upper level low pressure system, will
dominate the weather pattern across the area for the today through
Tuesday. This will produce cloudy skies, scattered rain showers,
and cooler than normal temperatures.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 257 AM CDT Mon May 18 2020

Early morning surface map indicated 1005 mb low pressure over
southern Lake Michigan. A cold front extended south into western
Indiana. West winds behind the front were advecting 50s dew
points into central IL. Water vapor imagery and UA data showed a
deep closed 500 mb low over southeast IA. The circulation around
this feature covered much of the Midwest. Latest radar scans
showed scattered showers associated with the upper low were
entering the far northwest CWA, while a few post-frontal showers
were exiting the far southeast CWA.

Short range models are in good agreement tracking the upper low
southeast across the area today and into far southern IL by late
tonight. This will result in low overcast, scattered showers, and
seasonably cool temperatures. QPF is expected to be on the light
side, mainly below one tenth inch. Steep low level lapse rates and
relatively low freezing levels below 700 mb will support a few
hundred J/kg of CAPE. So a few thunderstorms are possible and
added slight chance of thunder to the grids 17z-00z. Cold air
funnels are often seen under such a strong upper low, but unless
any breaks in the cloud cover can develop this looks unlikely.
Otherwise high chance showers will be dominant with best coverage
during the afternoon. Highs to reach the lower 60s of most of the
area, with some mid 60s in eastern IL. Low clouds remaining in
place tonight will limit diurnal temp drop to the low/mid 50s.
Showers should diminish during the evening and only have slight
chance overnight.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 257 AM CDT Mon May 18 2020

The upper low is forecast to continue shifting southeast into
central TN by late Tuesday night. With an omega block developing
to the north over the Great Lakes, and a separate area of upper
ridging developing off the east coast in the wake of a tropical
system, the upper low is expected to stall over TN through
Wednesday. Due to the wide circulation around the low, this will
keep us in cyclonic flow through mid-week, resulting in cloudy
skies. Scattered, again mainly diurnally driven showers will be
around the area Tuesday. This activity should sink farther south
on Wednesday, with chance pops across far southeast IL.  As the
low gradually fills and heights rise, temperatures will moderate
towards seasonal norms through mid-week.

For Thursday into Friday the omega block shifts east, allowing
the low to drift back north through the Ohio Valley and towards
the southern Great Lakes. The feature will be much weaker by this
time, but still able to generate some scattered showers or storms,
possibly as far west as eastern IL. There is some model spread on
the location of the low and associated precip at this time.

As we head into the weekend, a longwave trof digging into
the Rockies will amplify downstream upper ridging from the Plains
into the Mississippi River Valley. This will induce southwest
flow and tap into the thermal ridge that has been building over
the Plains, pushing temperatures several degrees above normal.
Models are quick to shift upper level energy northeast into the
area for continued thunderstorm chances, though if the upper
ridge holds this could keep the more active weather to the west
through much of the weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 638 AM CDT Mon May 18 2020

MVFR cigs are expected at all sites most of the period. However,
PIA and BMI are currently lower, below 1kft but should improve in
a few hours to MVFR. CMI is VFR but should drop at 13z to MVFR
like the rest. Scattered showers have already moved into the area
and will have BMI and PIA as -shra this morning, before becoming
VCSH late morning. All sites will be VCSH late morning through
afternoon and early evening as cold upper level low kicks off some
scattered showers over the area. These should dissipate toward
sunset. With upper level and sfc low pressure area over central
Illinois, winds will be lighter. Expecting southwest winds this
morning but then becoming northwesterly to north in the evening
for SPI/DEC/CMI. PIA and BMI will see winds become northwest this
afternoon and then northerly this evening.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 7 AM CDT this morning for ILZ051.

&&

SYNOPSIS...25
SHORT TERM...25
LONG TERM...25
AVIATION...Auten

Hazardous Weather Outlook
National Weather Service Lincoln IL
353 AM CDT Mon May 18 2020

ILZ027>031-036-037-040-041-047-049-050-190900-
Cass-Fulton-Knox-Marshall-Mason-Morgan-Peoria-Schuyler-Scott-
Stark-Tazewell-Woodford-
353 AM CDT Mon May 18 2020

This Hazardous Weather Outlook is for portions of central
Illinois and west central Illinois.

.DAY ONE...TODAY AND TONIGHT...

Isolated thunderstorms are possible this afternoon.

Moderate river flooding will continue on the Illinois River for
the next several days.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY...

Scattered thunderstorms are possible this weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated through tonight.

ILZ038-042>046-048-052>057-061>063-066-190900-
Champaign-Christian-Clark-Coles-Cumberland-De Witt-Douglas-Edgar-
Effingham-Logan-Macon-McLean-Menard-Moultrie-Piatt-Shelby-
Vermilion-
353 AM CDT Mon May 18 2020

This Hazardous Weather Outlook is for portions of central
Illinois, east central Illinois and southeast Illinois.

.DAY ONE...TODAY AND TONIGHT...

Isolated thunderstorms are possible this afternoon.

Minor river flooding will continue along much of the Sangamon
River for the next few days.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY...

Scattered thunderstorms are possible this weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated through tonight.

ILZ051-190900-
Sangamon-
353 AM CDT Mon May 18 2020

...FLASH FLOOD WATCH IN EFFECT UNTIL 7 AM CDT THIS MORNING...

This Hazardous Weather Outlook is for portions of central
Illinois.

.DAY ONE...TODAY AND TONIGHT...

Isolated thunderstorms are possible this afternoon.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY...

Scattered thunderstorms are possible this weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated through tonight.

ILZ067-068-071>073-190900-
Clay-Crawford-Jasper-Lawrence-Richland-
353 AM CDT Mon May 18 2020

This Hazardous Weather Outlook is for portions of southeast
Illinois.

.DAY ONE...TODAY AND TONIGHT...

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY...

Scattered thunderstorms are possible this weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated through tonight.

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