Area Forecast Discussion
Issued by NWS Paducah, KY
FXUS63 KPAH 301938
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
238 PM CDT Thu Oct 30 2014
.SHORT TERM...(Tonight through Saturday night)
Issued at 236 PM CDT THU OCT 30 2014
The late morning forecast discussion update addressed the overall
character of the Freeze Watch for the weekend. From a Watch
perspective, did not make a distinction between freeze (32F to
28F) and hard freeze (mainly associated with temperatures below
28F) duration, but the net effect is that the eventual Freeze
Warning issuance will be to end the growing season. The only
caveat is whether we will experience a brief winter warm up which
could cause the germination of cool season plants. For now the
probability of a warm up is extremely low and not addressed in the
freeze watch product.
Most of the effective forcing associated with the approaching
cold front remain at mid and upper levels (generally between
6kft-20kft AGL). However, despite the drier air at lower levels.
mid-level moisture and lift should be sufficient to produce a very
narrow band of surface-based precipitation. Radar coverage of
precipitation will likely remain greater than surface coverage through
at least 5 pm CDT, but as the lower atmosphere cools, saturation
will increase at a greater rate leading to better chances of precipitation
reaching the surface through the evening hours.
There will be at least a 2 to 4 hour delay following the surface
front before the post frontal surface wind gradient kicks in
across the area. This gradient will remain dominant in advance of
the high through at least 5 to 6 pm CDT Friday. After that time
the wind gradient will slowly relax from southwest to northeast.
Most of the cooling going into Friday night will be dominated by
cold air advection, while most of the cooling Saturday night will
be associated with the conversion of air mass and more ideal
radiational loss, especially at night.
Trends the last 48 hours have been toward a 1-2 degree lowering of
minimum temperatures over the weekend. Therefore, anticipate a
switch toward a freeze warning within the next 6 to 15 hours for
our forecast area.
.LONG TERM...(Sunday through Thursday) Issued at 149 PM
CDT THU OCT 30 2014
We start off Sunday morning with the ending of the headline Freeze
Watch and cool start. The air mass will start modifying again, as
the surface high shifts east, and southerlies return coincident
with upper ridging/heights rising. Despite the cold start, we
should still see about a 25 degree diurnal rebound. And then we
climb back into the 60s Monday.
This sets the stage for the incoming storm system. Superblend
paints a broad swath Pop seemingly a little early...Monday night.
We tried to refine this pop to mainly the Ozarks of Semo, then
spread it over the remainder of the FA Tuesday. We also heightened
pops a little Tuesday, and Tuesday night, as the likely event is
signaling categorical. And similarly, we trimmed west to east end
pops Tues nite-Wed, to hopefully hit the specific trending a
little better than the blend. This includes the accompanying
thunder chance mention.
After the post frontal cooldown, conditions return to seasonal for
Issued at 236 PM CDT THU OCT 30 2014
With the approach of the cold front, most ceilings will remain in
the VFR category through the first 18 hours of the forecast
period, given that most of the ceilings will likely remain at or
above 4-6kft AGL. Given the short temporal and spatial probability
of seeing surface-based precipitation, left a mention of showers
as vicinity showers. This may have to be addressed with the 00z
issuance as the lower atmosphere cools.
IL...FREEZE WATCH from late Friday night through Sunday morning FOR
MO...FREEZE WATCH from late Friday night through Sunday morning FOR
IN...FREEZE WATCH from late Friday night through Sunday morning FOR
KY...FREEZE WATCH from late Friday night through Sunday morning FOR