Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 241139

Area Forecast Discussion
National Weather Service Paducah KY
639 AM CDT Wed Apr 24 2019

.SHORT TERM...(Today through Friday night)
Issued at 319 AM CDT Wed Apr 24 2019

The interplay between the mesoscale positive tilt trough axis
stretching from northeast IA to the OK panhandle and the
approaching closed low moving through TX/LA/Lower Mississippi
Valley today through Thursday will impact the coverage and timing
of precipitation for the WFO PAH forecast area.

Current precipitation is moving along and north of the surface to
700 mb warm frontal zone across central IL at this time. Embedded
vorticity expelled from the closed low will work along the east
east side of the MO/KS trough axis this morning. The weakly
enhanced lift and ageostrophic forcing will interact with the
surface based theta-a convergence over the southeast Missouri
foothills to enhance surface lift into isolated showers and
thunderstorms along western sections of southeast Missouri shortly
after daybreak. The combination of a narrow plume of deeper layer
moisture (already aided by a pre-existing pool of near 60
dewpoints at the surface) and broad lift from the trough/vorticity
will slowly expand the shower and thunderstorm activity across the
remainder of southeast Missouri and into the southwest half of
Illinois by mid-morning. By late afternoon, as the main zone of
lift bisects the WFO PAH forecast area from southwest to
northeast, nearly all of the region will see a good chance or
better for showers and thunderstorms.

Where there is repeated convection, anticipate some areas may see
one quarter to four tenths of an inch this afternoon and through
this evening. With the loss of daytime heating, updrafts may be
subdued overnight with rainfall amounts remaining one to two
tenths or less. The highest QPF (forecast rainfall amounts) are
likely to occur Thursday afternoon and evening, as enhanced
deformation zone rainfall develops as the closest pass of the
closed low over the Lower Mississippi Valley. Rainfall amounts of
four tenths to locally three quarters of an inch will be possible,
especially over parts of the WFO PAH forecast area along and east
of the Mississippi River. The timing of this rain may cause some
ponding of water in low-lying areas, the the total QPF and
antecedent rainfall coverage. At this time, even WPC has only a
Marginal coverage for excessive rainfall forecast for Thursday
over southern sections of west Kentucky. If anything, may see the
potential for an urban/rural areal flood advisory in locations
with repeated convective activity Thursday afternoon.

As the trough axis and low center move east of the area late
Thursday night, rain chances will diminish quickly with dry
weather on Friday.

Leaned closer to GFS guidance for Max/Min temperatures in the
short term, allowing for the impact for rain and cloud cover.

.LONG TERM...(Saturday through Wednesday)
Issued at 319 AM CDT Wed Apr 24 2019

The 00Z medium range guidance is in decent agreement in moving an
upper-level disturbance through the Upper Midwest Saturday and into
the Great Lakes Saturday night. This will drag a cold front through
our area Saturday night and leave dry surface high pressure in
control of the region Sunday.

Guidance is not in as good agreement in QPF ahead of the front
Saturday, and the general trend seems to be headed toward a drier
solution. The forcing is meager at best and is relatively short-
lived. With dry air over the region initially, and only weak return
flow ahead of the front, much of the area should remain dry with a
small chance of some light rain, mainly across the northern half of
the area.

The cold front Saturday night is likely to come through the entire
region dry. Instability is hard to find and the low-levels will be
dry with little moisture return expected given surface ridging along
the northern Gulf coast.

As we head into next week, guidance is indicating that a pattern
shift will take place. By next Wednesday, we should have a trough
west/ridge east pattern, putting our region on the fringe of
stronger southwest flow aloft. The primary surface boundary should
eventually get established to our northwest.

We should see winds begin to turn around from the southeast on
Monday, and a warm front of sorts may allow for some shower
development mainly over the northern half of the region during the
day. This activity should exit the area Monday night, leaving the
entire area firmly in the warm sector.

Look for Tuesday and Wednesday to be warm with increasing humidity
and gusty south to southwest winds. The models seem to have a
perpetual Day 7-8 PoP as they attempt to push convection southeast
off of the front, but this is likely overdone. The initial PoPs for
next Wednesday are likely too high.


Issued at 639 AM CDT Wed Apr 24 2019

Gradual Lowering of VFR ceilings expected by afternoon at most TAF
locations with the pockets of convective activity (showers and
thunderstorms) and associated ceiling reductions.

After 06z Thursday, ceiling reductions to MVFR category will occur
as the coverage of convection ahead of the cold front impacts each
TAF site from northwest to southeast acros the area.




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