Flooding in Illinois, March 15 to 31, 2021

Area Forecast Discussion
National Weather Service Paducah KY
513 PM CDT Sun Mar 14 2021

.UPDATE...
Issued at 505 PM CDT Sun Mar 14 2021

Updated Aviation discussion for 00Z TAF Issuance.

&&

.SHORT TERM...(Tonight through Tuesday)
Issued at 310 PM CDT Sun Mar 14 2021

H50 short wave energy will eject northeast into the Mid MS River
Valley tonight, bringing an associated surface warm front with it.
A rather large band of showers ahead of these features will push
from west to east across the forecast area during the overnight
hours and into Monday morning. It appears right now that most of
the instability (and thus thunder chances) will be limited to
areas just to our south in TN. Rainfall totals still look to be
on the order of a half inch to an inch by the time the system
exits Monday afternoon.

Much warmer air, along with drier conditions, will move in in the
wake of the warm front Monday afternoon through Tuesday, as the
flow aloft becomes more zonal. Warmest temps Monday afternoon will
be over se MO/wrn KY, where precip will end earliest and some
sunshine may return.

.LONG TERM...(Wednesday through Sunday)
Issued at 310 PM CDT Sun Mar 14 2021

he long term forecast is primarily focused on the midweek system
that will bring showers late Tuesday through Thursday along with
thunderstorm activity Wednesday and Wednesday night. Confidence in
the overall system is moderately high while confidence in strong to
severe storm potential is low.

A well-organized vertically-stacked low pressure system is expected
to emerge from the Four Corners region into the Oklahoma
Panhandle/Northern Texas Tuesday night. As this system moves
eastward into Oklahoma late Tuesday night, Gulf moisture will
increasingly be steered northward towards the front of the low
rather than across the Deep South. Winds across the Quad State have
shifted a bit more southeasterly rather than southerly this model
cycle, which has resulted in a slight shift downward in
temperatures. Nonetheless, highs in the upper 60s and dew points
well into the 50s will provide an adequate moisture source for storm
activity.

Model ensembles continue to be clearly separated into two main
groups, though the structure is a bit more aligned leaving timing
the key differentiator. The GFS ensemble skews earlier with the
primary shower/storm activity during the day Wednesday. The NAM is
in decent agreement with the GFS. The ECMWF and Canadian ensembles
are slower, delaying the strongest storm potential until Wednesday
evening/night. The NBM plays this in between and the forecast agrees
with setting the primary storm potential to Wednesday afternoon-
evening hours. However, NBM PoPs for Wednesday through Wednesday
night were quite low, below the 25th percentile, so PoPs were raised
to the likely range for a larger area and longer duration.

SPC continues to highlight this Wednesday event, now in the Day 4
outlook. The primary focus of severe weather potential is definitely
further south towards Mississippi and surrounding states. With
decent shear, instability, and moisture the ingredients are there,
but whether everything comes together this far north is a different
matter. The shift towards southeasterly rather than southerly winds
into the Quad State may suggest a less northward extent of strong to
severe storms compared to model runs from yesterday. Rainfall
amounts are forecast to be on the order of an inch but locally
higher amounts in thunderstorms, and fairly high soil moisture
levels from recent rains, may lead to some localized issues.

The low pressure system will track across the southern half of
Missouri Wednesday through Wednesday night, crossing the Quad State
Thursday. On Thursday, we will be in a more stratiform rain area of
the system with thunderstorm activity unlikely. Winds will shift to
the northwest by the end of the day behind the low. Dry weather
returns Friday through the weekend as a ridge builds into the area.

High temperatures in the upper 60s to near 70 Wednesday will drop to
the 50s afterwards. Lows in the mid-40s to near 50 Tuesday/Wednesday
night will similarly fall to the 30s by the end of the week.

&&

.AVIATION...
Issued at 510 PM CDT Sun Mar 14 2021

MVFR-VFR bases may show temporary improvements early this evening,
but will deteriorate again tonight on the approach of the next
weather system. It will ultimately genesis a line of showers that
will restrict vsbys to MVFR, and may include thunderstorms
capable of locally heavy rain restricting cigs/vsbys temporarily
to IFR. After its passage late tonight, a gradual improvement back
to MVFR, then VFR conditions is expected. Bases may even scatter
in the west in the afternoon, but could linger in the east, even
with cigs, thru the entirety of the planning phase hours.

&&

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

&&

Hazardous Weather Outlook
National Weather Service Paducah KY
315 PM CDT Sun Mar 14 2021

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-
100-107>112-114-152015-
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-
315 PM CDT Sun Mar 14 2021

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

.DAY ONE...This Afternoon and Tonight

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Thunderstorms are possible late Tuesday night through Wednesday
night. While heavy rain and lightning are expected to be the primary
hazards, there is some potential for strong to severe storms.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated a this time.