Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 261156

Area Forecast Discussion
National Weather Service Paducah KY
555 AM CST Sat Nov 26 2016

Issued at 555 AM CST Sat Nov 26 2016

Updated aviation discussion for 12Z TAFs.


.SHORT TERM...(Today through Monday night)
Issued at 215 AM CST Sat Nov 26 2016

Main forecast concern in the near term is getting the low stratus
out of here today. Then we turn our attention to the next storm
system slated to bring our next chance of precipitation Sunday
night into Monday night. Forecast confidence is relatively high
through the period with good overall synoptic model agreement.

The back edge of the solid stratus deck had reached western
Illinois early this morning. However, patches of stratus have
redeveloped across portions of southeast Missouri where clearing
took place Friday evening. While not exact, the NAM12 and RAP13
appear to have the best handle on this sky cover via 925mb
moisture, so will follow closely for the sky cover forecast today.
Consequently, a trend towards more sunshine is expected from west
to east today as the surface ridge of high pressure passes by and
shifts low level winds to the southwest by afternoon. Temperatures
today will likely be several degrees cooler in eastern versus
western portions of the area with the lingering cloud cover.

Dry and generally mild conditions are expected tonight into Sunday
as the upper level ridge progresses east into the Mississippi
Valley. With clear skies and light winds, tonight will be quite
chilly as temperatures drop into the upper 20s and lower 30s. On
Sunday, high clouds will already be on the increase ahead of the
next storm system, but conditions should remain dry. Expect a
good rebound in temperatures with highs in the upper 50s.

Upper level energy forecast to enter the western U.S. today 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 Sunday night 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. We also have enough consistency in model forecasts of
instability--albeit still minimal--to support the mention of
thunder Monday afternoon and Monday evening. The precipitation is
expected to quickly come to an end Monday night as drier air works
in from the west.

.LONG TERM...(Tuesday through Friday)
Issued at 215 AM CST Sat Nov 26 2016

Below average confidence through most of the long term period due to
lack of model agreement.

The long term period starts off with a closed H5 low and associated
surface low centered over Minnesota so the region is under troughing
from the surface up through the mid levels. From the upper low a
huge long wave trough extends southward into the southern plains. In
addition, a cold front expected to cross the region Monday into
Monday night should be south and east of our region. Weak surface
high pressure over the high plains attempts to move toward the
southern plains.

Due to the deep southwest flow aloft being parallel to the
aforementioned frontal boundary, it is forecast become quasi-
stationary south and east of our area Tuesday night, at least
according to a couple of models.

From late Tuesday night through Wednesday night is where models lack
agreement. In response to impulses of energy in the southwest flow
aloft, the ECMWF induces a surface low/wave on the boundary and
develops overrunning precipitation over the southeast third of our
CWA through Wednesday morning. During this period the GFS is fairly
progressive and doesn`t show any precipitation in this period, but
attempts to develop overrunning precipitation just to the south and
east of our CWA Wednesday night. The Superblend looks more like the
ECMWF, but also shows overrunning precipitation over the eastern
fourth of our CWA Wednesday afternoon. With time would not be
surprised if we don`t pull POPs out of Wednesday altogether.

From Wednesday night on rising heights aloft and surface high
pressure spreading eastward across the deep south should keep the
region dry through the rest of the period.

Temperatures start off the period above normal, then remain
near normal through the rest of the period.


Issued at 555 AM CST Sat Nov 26 2016

Early morning satellite indicated the persistence of MVFR stratus
over much of the area east of a KMVN-KPAH-KCEY line. West of there,
stratus was much more sporadic. Interestingly, the back edge of the
stratus over Illinois appeared to be expanding westward while that
over Missouri was building eastward--likely driven by flow around
the 925mb high. Both models that have a decent handle on this low
level moisture, the NAM12 and RAP13, continue to indicate the
stratus should gradually erode from west to east as the day
progresses. However, it may be mid afternoon before KEVV and KOWB
see much clearing.

Where the sky cleared, patchy IFR-MVFR fog formed in southeast
Missouri. This should dissipate through mid morning. More MVFR fog
development is possible after midnight tonight. Otherwise, winds
will be light through the period.




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