Area Forecast Discussion
Issued by NWS Paducah, KY

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436
FXUS63 KPAH 210008
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
708 PM CDT Sun May 20 2018

.UPDATE...
Issued at 708 PM CDT Sun May 20 2018

Updated aviation discussion.

&&

.SHORT TERM...(Tonight through Tuesday night)
Issued at 312 PM CDT Sun May 20 2018

Main convective line moving through southern Illinois and the delta
region of west Kentucky being supported by 2500-5000 j2/kg2 LAPS
surface based CAPE stretching from the Mississippi River near New
Madrid, then arcing northeast into northwest Kentucky south of
HEHR and KOWB at 20z. Updraft/cold pool flow balance is episodic
with parts of the line seeing gust front extension ahead of the
line.

Cleared a few counties from Severe Thunderstorm Watch behind the
line of thunderstorms. There will be a few hours of boundary
layer stabilization before the flow returns southerly across the
area, priming the pump for later tonight into Monday over western
sections of southeast Missouri and southwest Illinois.

Although there is some timing issues for the resumption of new
showers and thunderstorms behind the current line of convection,
both the RAP and CMC model guidance suggest new convection will
fire back further west into Missouri and slowly work east back
into our area overnight and during the day on Monday. Channeled
vorticity in the southwest flow aloft will help to maintain
periodic lines of showers and thunderstorms from Monday night into
Tuesday, with the main activity shifting east with the front.

.LONG TERM...(Wednesday through Sunday)
Issued at 312 PM CDT Sun May 20 2018

Fairly high confidence of an unseasonably warm pattern Wednesday
through Friday with little if any precipitation coverage most of the
time. A nearly stationary mid/upper level high pressure ridge will
be the main weather influence through the lower and mid MS River
Valley through that time frame, with little low level
forcing/triggers. Expect daily highs well into the 80s each
afternoon. Temps will cool back into the 60s at night.

As we head into next weekend, a system over the northern Gulf of
Mexico is expected to drift slowly north into the southern Gulf
Coast states. At the same time, a mid level trof and associated weak
surface front should be working east/southeast toward the Ms River
and lower OH river Valleys. This would lead to increasing
shower/thunderstorm chances on Saturday into Sunday, especially
during the heat of the day. Conditions should also remain quite warm
and humid through the weekend. It will be interesting to see how
well, if any, the two systems can merge into one deep elongated trof
by that time.

&&

.AVIATION...
Issued at 708 PM CDT Sun May 20 2018

The stabilization of the atmosphere due to diminishing shower and
tstm activity will yield VFR cigs across the region into the
overnight hours. However, short-lived MVFR cigs are expected to be
associated directly with scattered shower/tstm activity that will
eventually pop up again during the 00Z TAF period. Best guess is
that this scattered activity may occur mainly late in the night/
early Sun morning north of the OH River, and in the late afternoon
mainly east of the MS River. Winds outside of tstms will be light
and variable overnight, picking up to less than 10 kts out of the
south-southwest after daybreak. Winds just off the surface will
lessen the likelihood of significant fog formation.

&&

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

$$

SHORT TERM...Smith
LONG TERM...GM
AVIATION...DB



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