Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 152318
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
518 PM CST Mon Jan 15 2018

.UPDATE...
Issued at 518 PM CST Mon Jan 15 2018

Extending the winter weather advisory until midnight for southern
portions of southeast Missouri and extreme southern Illinois.
A couple of moderate to heavy bands of snow will stream across
these areas into early evening.

&&

.SHORT TERM...(Tonight through Wednesday night)
Issued at 227 PM CST Mon Jan 15 2018

Snow bands continue to move across the southern third of our
counties, with patchy light snow across all but our far
north/northwest counties. Will be removing portions of southern
Illinois along and north of Route 13 and Perry county Missouri
from our northern advisory as of 21z. Amounts of 2 to 4 inches
are common east of the Mississippi so far, with isolated higher
amounts, with 1 to 2 1/2 inches west of the Mississippi. Expect
to see some additional minor accumulations across portions of
southeast Missouri and areas along the Ohio River for the next few
hours, with a bit more accumulation possible across southern
portions of west Kentucky into the evening. We will gradually be
chipping away at our advisories as snow tapers off. HRRR and RAP
hint at some snow lingering in our far southeast counties after
06z, but for now will keep the southern advisory ending at that
time.

Surface observations show the front through most of our counties.
Colder air is right behind, with temperature drops of 4 to 7
degrees already at several sites in our northern counties.
Overnight lows will drop into the 0 to 10 above zero range. Winds
will stay up in the 6 to 10 kt range overnight, and this puts wind
chills in the -5 to -15 range. Wind chill advisory for southwest
Indiana, most of southern Illinois and portions of northwest
Kentucky for -10 to -15 looks good and will not make any
adjustments. Conditions will remain pretty unpleasant into
Tuesday with highs only in the teens and winds chills only
"improving" to the above zero single digits.

An upper level trof will move across our area Tuesday into Tuesday
night. This may squeeze out some flurries across mainly northern
portions of the PAH forecast area Tuesday afternoon into Tuesday
evening. Lows Tuesday night will again be in the single digits,
but generally light winds will prevent wind chills from being an
issue.

Surface high pressure will move to our south on Wednesday, and a
shift to south to southwest winds late Wednesday into Wednesday
night will begin our "warm up", with highs Wednesday in the less
miserable lower to middle 20s, and lows Wednesday night in the 8
to 14 degree range.

.LONG TERM...(Thursday through Monday)
Issued at 227 PM CST Mon Jan 15 2018

The extended forecast period will start with the building upper
level ridge and blocking surface ridge across the entire Gulf Coast.

A small circulation rotating around the western side of an eastern
Pacific/Pacific Northwest U.S. trough is forecast by both the 12z
deterministic GFS and ECMWF to persist through a narrow high
amplitude ridge and develop lee side cyclogenesis as it moves
southeast into western Texas early Thursday. Numerical model
guidance has this low stalling out and closing off on Friday, as a
split zonal flow develops just to the north of it into the Plains.

A broader amplitude eastern Pacific trough (forecast west of the
previous Pacific Northwest trough on Thursday) will carve out a low
to moderate amplitude shortwave along the path of the previous Texas
low as it weakens and shears out over the southeast U.S.

The net effect of the shortwave trough as it moves from the southern
Rockies and into the southwest U.S. by Saturday will be to enhance
broad southwesterly flow (and persistent warm advection) into the
WFO PAH forecast area, while opening up a moisture channel from the
Gulf of Mexico. The initial stages of the moisture advection and
temperature advection will take place early Friday.

This transition to southwesterly flow aloft will increase
thicknesses, increasing daily minimum and maximum temperatures, with
both low and high temperatures remaining above the freezing mark
starting Friday.  The ECMWF is a little more aggressive with the
rise in temperatures, by as much as three degrees, compared to
regionally blended model guidance.  At this point, given the amount
of thermal energy needed to melt and evaporate snow cover and snow
melt, combined with cloud cover, plan to leave slightly cooler
temperatures in place. Regardless, temperatures 10 to 15 degrees
above normal will be expected into the weekend and early next week.

At the end of the extended forecast period, a cold front is expected
move through with more copious rainfall amounts and cooler
temperatures (not anything like last week). However, uncertainty on
rainfall amounts and timing precludes any significant focus on any
water (i.e. flooding) concerns at this time.

&&

.AVIATION...
Issued at 1132 AM CST Mon Jan 15 2018

Banded snow from the initial round of convective activity should
move out of the KPAH/KEVV/KOWB areas by 20z-22z, with KCGI dealing
with MVFR conditions during the same time period.

As the main axis of instability and lift rotating around the upper
trough continues to work south and southeast, conditions should
improve to VFR conditions until at least 09z Tuesday. Cold air
stratus/stratocumulus will work back into each of the TAF
locations with brief MVFR visibilities due to some light snow/snow
flurries. Gradient winds will be strong following the passage of
the convection this afternoon, so increased wind speeds and gusts
associated with the frontal passage.


&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory until 6 PM CST this evening for ILZ088-
     089.

     Wind Chill Advisory from midnight tonight to 11 AM CST Tuesday
     for ILZ075>078-080>091.

     Winter Weather Advisory until midnight CST tonight for
     ILZ090>094.

MO...Winter Weather Advisory until 6 PM CST this evening for MOZ086-
     087-100.

     Wind Chill Advisory from midnight tonight to 11 AM CST Tuesday
     for MOZ076.

     Winter Weather Advisory until midnight CST tonight for
     MOZ107>112-114.

IN...Winter Weather Advisory until 6 PM CST this evening for INZ081-
     082-085>088.

     Wind Chill Advisory from midnight tonight to 11 AM CST Tuesday
     for INZ081-082-085>088.

KY...Wind Chill Advisory from midnight tonight to 11 AM CST Tuesday
     for KYZ007-010-013>016-018>020.

     Winter Weather Advisory until midnight CST tonight for
     KYZ001>022.

&&

$$

UPDATE...RST
SHORT TERM...RST
LONG TERM...Smith
AVIATION...Smith


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