Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 221958
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
258 PM CDT Tue Apr 22 2014

.SHORT TERM...(Tonight through Thursday night)
Issued at 258 PM CDT TUE APR 22 2014

Cool dry advection is ongoing across the area today, and the last
of the cu have just about pushed to the southeast. North winds
have been gusting up to 20 mph at times today.

Surface high pressure will nose southward into the area tonight,
and the gradient will relax. However, am not sure whether the
winds will become calm for any prolonged period overnight. With
dewpoints forecast to be well into the 30s and clear skies,
the potential exists for temperatures to drop into the upper 30s
if winds are calm. This brings up the possibility of frost.
Guidance generally keeps temperatures at 40 degrees or in the
lower 40s, so confidence is not great enough to mention even
patchy frost at this time.

Raw model guidance is much more agressive than statistical
guidance in returning low-level moisture across the area on
Wednesday. With easterly low-level winds forecast, decided to lean
heavily toward the statistical guidance, which takes RH`s in the
east down to near 30%. With relatively light winds, this should
not be a major concern for fire weather.

Southeast winds will increase Wednesday night, which should result
in a rather mild night. Generally went above guidance for lows
Wednesday night.

Our next storm system is still on track to move through the area
Thursday afternoon and evening. The guidance has been rock solid
on this timing for a few days now, so the main question now is
coverage. We will be on the southern edge of the mid and upper
level storm system and it will be approaching rather quickly. This
will not allow much time for southerly return flow of moisture
into the area. A look at 12Z NAM and GFS soundings across the area
indicate that moisture and instability will be lacking, and may
struggle to get together along or ahead of the front. However, figure
that the forcing will be strong enough to overcome the lack of
moisture and instability to generate scattered to numerous
thunderstorms along and ahead of the front.

The wind field will be impressive from the surface to 3km, with
enough SRH to support rotating updrafts. The problem is the mid
and upper level flow is relatively weak, resulting in weak storm-
relative flow. This could lead to outflow dominated storms, and a
tug of war between the tendency for rotating updrafts and outflow
dominated storms. A few storms may briefly approach severe limits
with damaging downburst winds the main threat. However, would not
expect a persistent severe threat with any individual storms.
Figure the main convective zone will run north to south right
through the middle of the area at 00Z Friday.

Will leave a small PoP in the far east after 06Z, but it may be
out of the area by then. Certainly should have nothing left by 12Z
Friday.

.LONG TERM...(Friday through Tuesday)
Issued at 258 PM CDT TUE APR 22 2014

At the beginning of the period weak high pressure at the surface and
rising heights aloft should be enough to keep things dry Friday and
Friday night. According to the Canadian model, precipitation
chances make their way back into the CWA on Saturday as a frontal
boundary sags southward into the lower Ohio valley. During the same
time period the GFS and ECMWF show no discernible surface boundary
and an intensification of the upper ridge to our west thus keeping
the precipitation at bay a little longer. Decided to go with the
majority and not bring precipitation into our area on Saturday.

Saturday night a storm system begins to take shape over the central
plains. Depending on which model solution you buy into, this will
either keep the aforementioned frontal boundary in the area or lift
a warm front northeast toward our CWA along with a slight weakening
of the upper ridging.  Either way it should provide better
precipitation chances for our area, it`s just that the orientation
of the precipitation will vary per model solution.

Precipitation chances increase even more Sunday, Sunday night, and
into Monday as the aforementioned system begins to move out of the
plains and keeps an E-W quasi-stationary frontal trough/boundary
across our CWA. Model solutions still a bit different on track and
placement of the upper level and surface features with the
approaching system, but precipitation chances should be elevated
regardless.

As the surface low and associated front with this system slowly push
across our area Monday night, precipitation chances may diminish
from west to east. Hard to say how things are going to pan out on
Tuesday. The ECMWF shows a huge dry slot and higher pressure being
pulled into our area keeping it dry while the GFS shows a pinwheel
effect and drags precipitation along and north of the low southward
back across the CWA. Either scenario looks feasible so decided to go
with chc POPS area wide. No doubt these later periods will need to
be adjusted as we draw closer to the event.

Temperatures will remain above normal through Monday but should be
below normal on Tuesday.

&&

.AVIATION...
Issued at 1213 PM CDT TUE APR 22 2014

VFR conditions expected at all sites through the period. Northerly
winds at 10-12 knots gusting up to 20-22 knots will become light
and variable after 01Z, then pick back up out of the northeast aob
10 knots after 15Z.


&&

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

$$

SHORT TERM...DRS
LONG TERM...JP
AVIATION...JP






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