Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 251123
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
623 AM CDT Sun Oct 25 2020

.UPDATE...
Issued at 616 AM CDT Sun Oct 25 2020


Updated Aviation discussion for 12Z TAF Issuance.


&&

.SHORT TERM...(Today through Tuesday Night)
Issued at 246 AM CDT Sun Oct 25 2020

Clouds will persist today and tonight given the abundant moisture
firmly in place and the lack of any subsidence/stronger high
pressure influence. Cannot rule out the possibility of some light
lingering precip but will keep below mentionable values for now.
Temps will not warm a lot today but still a few degrees more than
yesterday given the lack of any precip and lessening cold air
advection.

The much advertised deep mid/upper level low pressure system is
still forecast to drop south into the Four Corners region by late
Monday and then into TX Tuesday night. This will yield a
southwesterly flow for our region and along with an inverted surface
trof setting up just to our west tonight and Monday will yield
increasing rain chance beginning tomorrow morning NW of a line from
about Dexter MO to Fairfield IL. This is a bit slower per most model
solutions. The over-running of the warmer air aloft over the cooler
air near the surface will set up a corridor of rain over southeast
MO and southern IL, although the amounts now appear to be somewhat
less, probably averaging 1/2 to 1 inch NW of a POF-MWA line, with
lesser amounts elsewhere to the southeast, including little to no
rainfall over western KY especially toward the southern Pennyrile.
Tomorrow afternoon through Tuesday morning is the most favorable time
frame for the greater rainfall. Will end rain chances Tuesday
afternoon and keep a dry forecast through Tuesday night, other than
some minimal rain chances late Tuesday night near the AR and TN
borders as low pressure approaches from the southwest.

Max temps will remain well below normal through the period with
highs mostly in the lower to mid 50s through Tuesday. Lows will be
closer to normal with values mostly in the 40s.

.LONG TERM...Wednesday through Saturday
Issued at 246 AM CDT Sun Oct 25 2020

The main topic in the longer term period will be an upper level
closed low and its progression from mid to late week. Models have
been doing better lately as far as consistency of the timing of this
low although there are still differences. At the start of the
period, The upper level low will be situated over southern
Arizona/southern Texas panhandle. Rain should be invading the area
throughout the day on Wednesday as this upper low moves toward the
Red River Valley and moisture surges northward and deepens with
time. The GFS and several of the GFS ensemble members and the GEFS
mean shows precipitation moving in as early as Wednesday morning,
The latest operational ECMWF keeps the morning rain free except for
maybe the far southern areas. However, many of the ensemble members
hint at the precipitation arriving in the morning, therefore the
going NBM PoPs for Wednesday morning look good. We will keep the
going trend of steadily increasing PoPs throughout the day and into
the evening hours with the approach of the upper low with likely
POPs by Wednesday night. This will probably need adjustment over
the next few days especially if the faster GFS is correct, i.e. we
could need higher PoPs during the day on Wednesday instead. Highs
on Wednesday should reach well into the 60s for many locations as
low level temperatures rise. Given the temperature anomalies from
the ECMWF ensembles, the best chances for warmer temps will be
across western KY.

By 12Z Thursday, the upper low will be positioned either in Oklahoma
or Arkansas. Scattered rain showers will likely be ongoing and
continue for much of the day on and off as the upper low moves
through. There may be a brief dry period as a dry slot moves in but
more scattered rain showers should commence shortly afterward as the
low moves overhead Thursday afternoon and evening. However, this far
out, chance type PoPs will be what is forecast with fine tuning work
to be done as we get closer to the event. Depending on the speed of
the system, we should see PoPs dwindle through the overnight hours.
Well all is said and done, we could end up seeing a little over 2
inches out of this system from 12Z Wednesday through 12Z Friday.
Given PWs max out at 1.5 to 2 inches, this seems reasonable. In
addition, the GEFS is indicating at least a 40% probabilities of
over 2 inches of rain for parts of west KY, which is where the
higher PWs are forecast to set up. The ECMWF ensemble mean is not
indicating it being that wet and actually focuses the higher QPF
chances further north. Too far out in time to know where the heavier
bands may set up but this should come into better focus as we obtain
a better handle on the overall evolution of this system.

All indications are that the precipitation should be done with by
12Z Friday, resulting in a fairly nice day and highs in the mid to
upper 50s. Some very dry air will move in from 850mb on up and low
level moisture will eventually lessen with time so a very nice
weekend is expected with temperatures close to 60 degrees.

&&

.AVIATION...
Issued at 623 AM CDT Sun Oct 25 2020

Vertical moisture profiles still suggest little/no break in the
restricted bases thru the forecast period. Expect MVFR cigs to
continue through the forecast period with some occasional low VFR
cigs. Some drizzle or sprinkles will remain possible today at
KEVV, KOWB and KPAH although the chances are low enough to exclude
in the TAFs. Winds will average NE at 5-8 knots, but will back to
a more northerly direction tonight.


&&

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

$$

UPDATE...RS


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