Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 202123
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
323 PM CST Thu Nov 20 2014

.SHORT TERM...(Tonight through Saturday)
Issued at 202 PM CST THU NOV 20 2014

Surface High pressure, currently ridging from the Upper
Mississippi river valley, southward and eastward into the
Commonwealth, will gradually slide to the east and over the middle
Ohio river valley enroute to the Delmarva area by Saturday.

As this occurs, warm and moist air transport will commence, with
satellite showing ample cloudiness from srn AR to the Gulf Coast.
The models actually develop and bring in some warm air
overrunning pcpn as early as tmrw pm, at which time it should be
all liquid. It then spreads this chance across the remainder of
the FA and continues it into/thru Saturday, in a generally warm
sector environ.

As a result, Pops, temps, and winds, will be on the gradual
increase thru the short term ptn of the forecast.

.LONG TERM...(Saturday Night through Thursday)
Issued at 322 PM CST THU NOV 20 2014

Main focus for this forecast package will be 1) the approaching
convective system late Saturday night through early Monday, and
the 2) the Thanksgiving Day weather.

Dealing with the greater travel impact issue for Thanksgiving Day
first, decided to lean toward the GFS/GFS Ensemble solution for
PoPs/Weather. The GFS/GEFS solution keeps the western ridge
further north and places the northeast edge of the WFO PAH
forecast area in cyclonic flow. This should keep most of the
significant forcing/moisture/cold air advection closer to the
Great Lakes. Therefore, with the exception of a transient shower or
flurry early Thanksgiving Day, it should be dry and seasonable for
the holiday.

The main concern for this extended forecast package will be for
Sunday. The closed low over West Central Texas Saturday evening,
becomes increasingly negatively tilted as it moves across Texas
into Arkansas by 12z Sunday. The GFS/GEFS appears to be more
consistent with the transition of this system. Given the climatic
northeast creep of the model guidance with time, the greater
likelihood of this system accelerating developing northwest is
not out of the question with time. Made some spatial adjustments
to the 12z deterministic guidance to address this potential,
mainly in the PoP/Weather type/QPF fields.

Agree with the earlier midnight shift that there is some potential
of a few strong storms across the Southeast Missouri Delta/Boot
Heel region, then further east across the Land Between the Lakes
and the Southern Pennyrile. The first time period of concern runs
in the 12z-18z time frame (6am-noon) on Sunday. The strong storms
would be associated with the passage of the warm front, and would
likely impact the Southeast Missouri Delta region. The second are
shows up during the afternoon time frame 18z Sunday-00z Monday
over the Pennyrile Region of West Kentucky. During this time,
0-3km shear, low-mid level lapse rates, and mid-level drying would
support stronger and deeper updrafts. The main limiting factor for
both time periods would be mixed layer/most unstable CAPE
remaining at or below 100 J2/K2. If anything this scenario, would
place any convection in a minor to moderate low CAPE, high shear
category. CIPS analogs for the Sunday time period are most similar
to late November in 1988, when more tornadic/severe storms were
reported in North/Central Mississippi. NAEFS/GFS/GEFS
anomalies/percentages associated with the Sunday convection
suggest a significant variation in the mean sea level pressures
over Southeast Missouri. This would suggest a greater potential
for deeper and further north translation of convection into the
WFO PAH forecast area. Added a differential mention of
thunderstorms into the forecast, with the highest PoP for
thunderstorms across the Southeast half of the WFO PAH forecast
area. High temperatures forecast are within 3 degrees below the
CIPS analog of low to mid 60s (e.g. 65 at Paducah for November
1988). Will likely make an adjustment to the Hazardous Weather
Outlook to reflect the potential for isolated strong storms along
and roughly south of a line from Dexter MO to Greenville KY.

&&

.AVIATION...
Issued at 202 PM CST THU NOV 20 2014

VFR cigs will be incoming late tonight-tmrw as high
pressure moves east and the next storm system begins to take shape
and approaches, setting the stage for a wet weekend forecast.


&&

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

$$

LONG TERM...Smith






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