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000
FXUS63 KPAH 250454 AAC
AFDPAH

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PADUCAH KY
1154 PM CDT Thu Apr 24 2014

.UPDATE...
Issued at 1145 PM CDT THU APR 24 2014

Updated the aviation discussion for the 06Z TAF issuance.

&&

UPDATE Issued at 928 PM CDT THU APR 24 2014

Updated forecast to account for precipitation trends. A large area
of showers and thunderstorms continues to spread across the forecast
area this evening. The entire region should have experienced a good
soaking rain by midnight. Also kept higher rain chances over the
northern 1/2 to 2/3 of the area late this evening through the early
pre-dawn hours Friday to account for greater elevated instability
associated with the passing mid level trough. With the low levels
slow to moisten up and deep layer shear lacking, severe storms have
not materialized. The threat has all but ended at this time, though
an isolated strong storm still cannot be completely discounted.

&&

.SHORT TERM...(Tonight through Saturday night)
Issued at 320 PM CDT THU APR 24 2014

Finally have some lower 50s surface dewpoints spreading into
southeast Missouri as of 19Z. It has taken most of the day, but
mid to upper 50 dewpoints seem reasonable for much of the area
ahead of the storms late this afternoon and this evening.
Instability is still meager at best, and the forcing associated
with the mid/upper-level trough will be the main instigating
factor for this event.

The HRRR has been fairly consistent through the day at bringing
the first of the showers and storms into Ripley and Carter
counties around 22Z, and to the Mississippi River by 00Z. It
appears as though the convection will become more organized as it
moves east over the remainder of the region through 06Z.

Model soundings indicate impressive 0-3KM SRH values, certainly
enough to support rotating updrafts, but the forcing is likely to
result in a linear event. So, would expect wind damage to be the
main concern with some minor potential for a brief tornado or two
with mesovortices or embedded supercell structures. Not sure just
how much severe weather there will be, given the struggling
moisture and instability. This may result in a better severe
threat across southeast Missouri and west Kentucky, where the
better low-level moisture will be located.

The 12Z models are in reasonable agreement that there will be some
wrap-around showers late tonight across the northeast half of the
area, as the main mid/upper trough moves through the region. The
showers may last through sunrise, especially in the Owensboro
area. Increased Pops to likely levels for this activity.

The 12Z models leave little to debate for Friday through Saturday,
but they do diverge a bit in the location of the weak frontal
boundary by 12Z Sunday. The GFS brings the boundary into the Tri
State area, while the NAM keeps it northeast of the area. It
basically stalls out, and takes on the look of a warm front, and
the models are dry through 12Z Sunday, so it will not make much
difference.

As for temperatures, will lean to the warm side of guidance for
lows tonight through Saturday night, and for highs on Saturday.
Guidance has cooled things down a few degrees for highs Friday, so
decided to blend the consensus of 12Z guidance with the previous
forecast.

.LONG TERM...(Sunday through Thursday)
Issued at 320 PM CDT THU APR 24 2014

During the day Sun, a large scale, deep low pressure system will
approach the PAH forecast area from the west, as agreed on by the
GFS/ECMWF ensemble means. Individual deterministic runs of the med
range models began to differ with the details after Mon (Day 6), but
agreement on the mid level and sfc features was not bad for that
time frame.

Some time on Sun morning, a warm front ahead of the system will
begin its trek nwd across the region. This, combined with divergence
aloft, deep moisture advection and instability, will result in
plentiful tstm activity west of the MS River, and scattered tstms
east of the MS River. Sun night/Mon/Mon night, showers will be
nearly a sure thing, with the best chance of tstms during the day
time hours. Due to multiple rounds of deep moist convection, and the
slower movement of the overall system, heavy rainfall amounts are
possible. Wind shear increases aloft Mon, and with available
instability, severe weather is possible into the evening.

From Tue through Wed night, pcpn chances are forecast to gradually
wane as the nearly stacked low pressure system wobbles through the
Midwest. The last signal for instability tstms appeared to be Tue.
There could be a resurgence of showers Thu as energy wraps around
the back side of the vast mid/upper low, as it possibly begins to
depart.

&&

.AVIATION...
Issued at 1145 PM CDT THU APR 24 2014

MVFR cigs/vsbys with or without VCTS/TSRA possible through 15-16Z...
otherwise VFR. Best chances for TSRA at KCGI/KPAH between 06-09Z
and between 09-14Z at KEVV/KOWB. Gusty southerly winds at 10-12
knots gusting up to 18-20 knots will veer around to the southwest
during the night with speeds slightly decreasing, veer around to
the northwest between 11-13Z aob 15 knots, then variable aob 5
knots after 00Z.

&&

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

$$

SHORT TERM...RJP
LONG TERM...DB
AVIATION...JP