Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 220108
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
708 PM CST Fri Nov 21 2014

UPDATE...
Issued at 708 PM CST Fri Nov 21 2014
Updated aviation discussion only.

&&

.SHORT TERM...(Tonight through Sunday night)
Issued at 100 PM CST FRI NOV 21 2014

A weather system will take shape and move in with a wet forecast
as we head toward and into/thru the weekend.

Satellite currently shows clouds invading the southern FA and
advancing slowly northeastward, their stream sourced from deep
layered moisture over the Gulf and extending into east Tx. Surface
dew points were already approaching 30 in the southwest, and
will be continuing toward the peak in the 50s on Sunday.

In addition, the warming/moistening environ is also destabilizing
with time, and is supportive of thunder inclusion in the forecast
by Sunday. That is when the parent Low lifts from the lower MS
valley and over our Region, spiking pops at near certain. It will
drag a cold front thru Sunday night, as it lifts off and out with
its source moisture.

Todays highs in the 40s will climb toward and even into the 60s
this weekend, while lows make a corresponding rise.

.LONG TERM...(Monday through Friday)
Issued at 206 PM CST FRI NOV 21 2014

This extended forecast period covers the departure of the weekend
system and transient disturbances in the cyclonic flow around mid-
week, just prior to Thanksgiving day.

The last couple of deterministic runs of the GFS/ECMWF/GEM
numerical guidance rotate the main 500 mb low from the Dakotas
into eastern MN and IA by the beginning of the extended period.
This generates a positively tilted channeled vorticity, as well as
tightly focused baroclinic forcing/lift on the southeast side of
the trough. This effectively leads to a chance of rain extending
through the day on Monday.

Minor ridging aloft and behind the trough support dry/cold air
advection Monday night through Tuesday night. The mid-and upper
level forcing serve to stall, deepen/sharpen, and elongate a mean
trough from the Great Lakes southwest toward the southern tip of
Texas. From a sensible weather standpoint, this interim period
will only serve to reinforce colder thicknesses/temperatures
already in placed across the WFO PAH forecast area and little else.

The issue of concern for travel on Wednesday will be the
timing/orientation/intensity of a minor shortwave rotating down
the back side of the trough by 12z Wednesday. The eastward
translation of the trough axis and the building of the western
U.S. ridge should limit the overall impact with light shower
activity across the area through Thursday morning (Thanksgiving).

Interim runs of the numerical model suite have been attempting to
flatten and retrograde the main low across the eastern U.S.
However, these solutions are more of an outlier. Decided to keep
the better signal of the building ridge and drier weather for most
of Thanksgiving Day and into the holiday weekend.

&&

.AVIATION...
Issued at 708 PM CST FRI NOV 21 2014

Sfc winds are expected to shift to the south overnight. Cigs should
lower to the MVFR range mainly in the wrn half of the region in the
evening hours, before rebounding to VFR overnight. Rain showers
moving ne this evening are expected to remain light and should not
restrict vsbys. Srly winds will strengthen on Sat, gusting to around
20 kts by late morning. Some widely scattered showers may affect
parts of sern MO/swrn IL during the day.


&&

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

$$

LONG TERM...Smith







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