Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 222303
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
503 PM CST Tue Jan 22 2019

.UPDATE...
Issued at 441 PM CST Tue Jan 22 2019

Updated for 00z aviation only.

&&

.SHORT TERM...(Tonight through Wednesday night)
Issued at 312 PM CST Tue Jan 22 2019

Main weather concerns for tonight will be...1) the potential for
minor overland flooding with snowmelt and forecast rainfall
over part of the WFO PAH forecast area that saw 4 to 9 inches of
snow over the weekend, and 2) strong wind and wind gusts overnight
ahead of the cold front moving through the region on Wednesday.

A secondary concern was the potential for a wintry mix of
precipitation on the tail end of the rain shield moving along and
ahead of the cold front. At this point in time, the loss of deep
layer moisture will reduce the measurable accumulations of any snow
and/or ice to next to nothing on Wednesday. Given the short zone
of transition to deeper layer colder air, there could be a brief
and low chance for freezing rain (less than 1 hour), but the main
focus will be from rain to brief snow before the precipitation
ends altogether.

There are no plans to issue any winter weather advisory for the
WFO PAH forecast area for Wednesday. A Special Weather Statement
will be issued to reflect the potential for black ice development
in the wake of the departing rain shield on Wednesday, as well as
the colder temperatures Wednesday night.

A Flood Watch was issued for parts of the WFO PAH forecast area
that saw the heaviest snowfall this weekend, covering a narrow
band of counties across southeast Missouri, southern Illinois, and
a small part of southwest Indiana. Temperatures since 15z (9 am
CST) this morning have already risen above freezing, initiating
snowmelt across that area. Virga and light rain showers have
already developed early this afternoon over southeast Missouri and
southern Illinois. This rainfall is forecast to increase in
coverage from southwest to northeast toward sunset with
moderate rain expected to move from southeast Missouri and
southwest Illinois after 7 pm CST. Anticipate approximately one
half to three quarters of an inch of rain to fall across the snow
cover in the Flood Watch area. Although this would be minimal for
even marginal flood scenarios, but the combination of latent heat
release from the rain, soil moistures of 65 to 85 percent of
capacity, combined with ambient melting of the snow cover, should
accelerate runoff this evening and overnight and could lead to at
least advisory level flooding of low-lying and flood prone areas.

A wind advisory is also in effect tonight. Gradient winds alone
due to the tightening pressure gradient should generate sustained
winds 20 to 25 mph with higher gust between 30 and 35 mph tonight.
The potential for downward momentum of winds from showers and
heavier rain and rain showers could help raise wind gusts near 40
mph or higher, tapping into 50 knot plus winds within the surface
to 1km layer. The RAP and GFS seem similar in the depiction of
the potential for mixing through that layer tonight.

.LONG TERM...(Thursday through Tuesday)
Issued at 312 PM CST Tue Jan 22 2019

Thursday continues to look dry as another weak front comes through
during the morning hours. Strong cold air advection will commence
later in the day and make for a chilly night Thursday night into
Friday morning. A strong pressure gradient will set up as this caa
sets in which won`t settle down until late Friday morning when high
pressure settles overhead. Temperatures late Thursday night into
early Friday morning will only be in the low to mid teens, with
single digits likely up along the interstate 64 corridor. Even
though winds will eventually taper off after sunrise Friday, they
will still be high enough to create wind chills down to zero to
possibly as low as eight degrees below zero, especially up north,
late Thursday night into Friday morning. This will be into the wind
chill advisory territory, so we will need to closely watch that.
High pressure moves east through the day on Friday and we actually
acquire a southerly component to the wind. But since we start out so
cold, high temperatures will only be able to rebound into the upper
20s to lower 30s on Friday.

A surface low pressure system which will be in the north central
Plains at the start of the period, will move southeast during the
day. While we may see an increase in clouds as this approaches, the
bulk of the deeper moisture will be situated to our north. However,
it appears our northern tier counties may see a glancing blow from
this system which may produce a few snow showers up near the I-64
corridor by Friday afternoon into Friday evening.

As we head into the weekend, this large scale upper trough does not
seem to be moving much and we continue to be dealing with embedded
disturbances traveling through this upper pattern and their
reflection at the surface, which continues to be difficult to time.
Case in point is Saturday, which has been troublesome for the past
few days now. GFS/ECMWF and the GFS ensemble mean indicates another
upper wave rotating down across the area but the ECMWF continues to
indicate a moisture starved system while the GFS paints some minor
QPF. The GFS has been pretty consistent between model runs on this
disturbance and even though the ECMWF has consistently indicated a
more dry solution, we will maintain our chance PoPs for now for the
Saturday afternoon through Saturday evening time frame.

Right on the heels of that system, yet another lobe of energy
rotates through on Sunday and may bring more light precipitation to
at least parts of the area Sunday morning. Then we should have some
time to dry out a bit. Model consensus improves greatly for early
next week. There is a strong signal for a potent system to impact
the area by Monday. We will see an increase in precipitation chances
Monday afternoon and lasting into Monday evening/overnight as a
strong cold front moves through. At this time, this system has the
potential to bring some snow to the area Monday night. Dry but much
colder weather is then expected in the wake of the system on
Tuesday.

Temperatures will be on a bit of a roller coaster ride for late
week, weekend and early next week. After some pretty cold weather on
Friday, it looks like temps will be rebounding over the weekend and
into Monday. Highs on Monday will top out in the 40s but then
temperatures will crash behind a strong cold front and bring us back
down to below normal for Tuesday.

&&

.AVIATION...
Issued at 441 PM CST Tue Jan 22 2019

Carried llws for most of the overnight hours at all sites. Start
bringing down vfr cigs to mvfr. Also bring in predominant rain
between 00z and 03z. Finally bring cigs to ifr cigs into the area
after 12z Wednesday. Finally start to clear rain chances from
south to north Wednesday afternoon. However keep a wintry mix in
the EVV and OWB. Also have a gusty winds through the overnight
hours. Then start losing the gusts after 12z.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory until 7 AM CST Wednesday for ILZ075>078-080>094.

     Flood Watch from 9 PM CST this evening through Wednesday morning
     for ILZ077-078-081>086-088.

MO...Wind Advisory until 7 AM CST Wednesday for MOZ076-086-087-100-
     109>112-114.

     Flood Watch from 9 PM CST this evening through Wednesday morning
     for MOZ076-086-087-100-107>109.

IN...Wind Advisory until 7 AM CST Wednesday for INZ081-082-085>088.

     Flood Watch from 9 PM CST this evening through Wednesday morning
     for INZ081-085.

KY...Wind Advisory until 7 AM CST Wednesday for KYZ001>022.

&&

$$

UPDATE...KH
SHORT TERM...Smith
LONG TERM...CW
AVIATION...KH


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