Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 271736
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1136 AM CST Sun Nov 27 2016

.SHORT TERM...(Today through Tuesday night)
Issued at 350 AM CST Sun Nov 27 2016

Main forecast concern in the near term is dense fog potential
early this morning. Then we turn our attention to the next storm
system slated to bring our next chance of precipitation tonight
into Monday night. Forecast confidence is relatively high through
the period with good overall synoptic model agreement.

Starting with this morning, areas of fog have developed across
much of the region. For the most part, visibilities have generally
remained in the 3 to 5 mile range. However, visibilities over
southern Missouri have dropped to 1/4 mile at both West Plains and
Poplar Bluff. As a result, we will be issuing a Dense Fog Advisory
for the westernmost 6 counties west of a line from Greenville to
New Madrid. More counties may be added if needed later on.

Once the fog burns off by mid morning, sunshine will become
increasingly filtered by high clouds on the increase ahead of the
next storm system. Dry conditions are expected through the day
with high temperatures reaching the mid to upper 50s.

Upper level energy currently over the southwestern U.S. is forecast
to generate the development of a deep low pressure system over the
Upper Midwest by Monday. Increasing moisture and lift coincident
with a strengthening southwesterly flow pattern will result in an
increasing potential for showers from west to east tonight and
Monday. Rainfall totals with this initial round of rainfall should
average no more than one or two tenths of an inch through early
Monday.

The bulk of the rain event is expected to occur from late Monday
morning through Monday evening as a strong mid level shortwave
rounds the base of the central U.S. trough and streams into the
Mid Mississippi Valley. Blended model guidance continues to
suggest the potential for 1 to 2 inches of rain across much of the
forecast area, with locally higher totals possible. This could
lead to the formation of standing water on roadways and in low
lying areas.

Enough elevated instability also exists to warrant at least a
slight chance mention of thunderstorms Monday and Monday evening.
The strength of wind fields aloft and resultant strong low level
helicity values is at least some cause for concern. However,
forecast MUCAPE values remain rather weak, so much of the focus
for severe weather should remain south of the immediate forecast
area.

The precipitation is expected to quickly come to an end Monday
night as drier air works in from the west. Tuesday still looks dry
and unseasonably warm with low pressure parked over the Upper
Midwest and the region still in southwest flow. For that matter,
highs Tuesday are forecast in the lower to mid 60s.

.LONG TERM...(Wednesday through Saturday)
Issued at 350 AM CST Sun Nov 27 2016

Confidence in the long term a little higher due to slightly better
model agreement.

At the beginning of the long term period a short wave ejecting
northeast out of a huge long wave trough centered over the central
US will induce a low/wave on a frontal boundary just to the south
and east of our CWA. This scenario (forcing through the column) will
tap into a stream of deeper moisture from the Gulf and produce
overrunning precipitation mainly over the southeast third of the CWA
Wednesday into Wednesday evening.

Late Wednesday night into Thursday should be dry as the front and
upper troughing move off to the east. This puts our region in zonal
flow aloft with the Gulf moisture cut off as high pressure at the
surface overspreads the area.

Beyond Thursday an interesting pattern develops across the country.
As the aforementioned upper troughing continues to shift eastward, a
short wave diving almost due south across the western US is forecast
to deepen into a cutoff low by 12Z Friday along the NV/UT border.
The low is forecast to continue moving southward and expected to be
over the Baja Peninsula by the end of the period.

This scenario puts our region between the two systems, consequently
there are no frontal boundaries, zonal flow aloft with little to no
upper level energy, very little moisture to work with, and high
pressure at the surface. All of this translates to little to no
chances for precipitation through the end of the period. Will have
to monitor subsequent model runs closely for any synoptic changes.

Temperatures the first couple of periods are near normal, then drop
to below normal through the rest of the period.

&&

.AVIATION...
Issued at 1136 AM CST Sun Nov 27 2016

Considerable high clouds will persist through the end of the day,
with an average south wind 6 to 12 kts. Will see cigs gradually
lower tonight, especially after midnight, with the chance of
showers moving in after 06z, continue through Monday morning. Cigs
will gradually lower to MVFR most areas, possibly pockets of IFR
especially after 12-15z. Winds will pick up late tonight, with
gusts over 20 kts likely some areas. The winds will continue gusty
into Monday morning.

&&

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

$$



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