AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
315 PM EST Mon Jan 16 2012

SHORT TERM [Tuesday through Wednesday NIGHT]...The short term
period will be encompassed by a frontal passage. The cold FRONT in
question currently stretches from eastern Ontario to northern
Missouri, and then arcs westward through southern Kansas. A
frontal wave developing along the front in the central Plains is
expected to grow into a surface low as a low amplitude upper level
TROUGH ejects into the Plains. The rapid CYCLOGENESIS in the Great
Lakes and up the ST. Lawrence Seaway, along with the progressive
zonal flow aloft, should help drive a cold front into the Gulf
Coast region late Tuesday Night and early Wednesday.

Tuesday: Despite some gradually increasing CLOUD cover, especially
above 10,000 feet, it still looks like a pretty warm day. There is
good agreement amongst the NAM, GFS, and GEM that 850mb TEMPS will
SURGE up into the +13C to +14C RANGE. Even if the TEMPERATURE
profile in the low-levels ends up being closer to the moist
ADIABATIC lapse rate, it would still LIKELY result in highs in the
low-to-mid 70s. The southeastward progression of POPS was delayed
relative to previous forecasts, and it wouldn`t be entirely
surprising to see most of the area staying dry prior to 00z Wed.
There may be a FEW showers in the THETAE ADVECTION MAX near the
coast, as is hinted at by our local 4km WRF-ARW, but confidence is
not high enough to portray that scenario yet.

Tuesday Night: The cold front finally pushes into our area. Timing
differences on the 16.12z SET of models are much less than in
previous model runs. For this forecast package, we used ENSEMBLE
approach. SREF and GFS Ensemble means have roughly the SAME timing
with the front entering our Alabama zones (NW corner of our area)
around 06z Wednesday, and reaching a TMA-TLH-AAF line by 12z.
Likely PoPs were included behind the front on Tuesday Night, where
the bulk of the PRECIPITATION will occur. ISOLATED THUNDER was
included as well, with MUCAPE 200-400 j/kg and equilibrium level
around -25 to -30C. For temperatures, we used a non-DIURNAL trend
as they will likely be almost steady ahead of the cold front for
much of the night.

Wednesday: As the front quickly exits the area, precipitation
should come to an end. It will be a cooler day with highs closer
to seasonal normals (low-to-mid 60s). Light FREEZE possible for
Wednesday Night.


&&

.LONG TERM [Thursday through next Monday]...Extended forecast
period will begin Thursday with a rather unamplified upper level
pattern across the CONUS, consisting of broad riding over the
inter-mountain west and broad troughing over the eastern half of
the nation. Wednesday`s cold front will be well to our south by
Thursday morning with high pressure building in from the north in
its WAKE. Some slight disagreement among the global guidance suite
as to the position of the surface high, with the GFS building the
CENTER overhead, and the the ECMWF/Canadian showing the high
center up over the Carolinas. The GFS would be a colder solution
Wednesday night, as the high position would favor a better
radiational cooling setup. Will not deviate much from the MEX
numbers for now which bring the normally colder inland spots down
into the lower 30s. A solution closer to the EC/Canadian will
lower the potential for significant coverage of subfreezing temps.
Overall pattern becomes quite zonal in nature for Friday with just
a weak shortwave riding the flow across the central portions of
the country. Influence of this energy will hold off until Saturday
providing a dry and warm final day of the workweek. Friday should
see highs well into the 60s to around 70 degrees away from the
immediate coast, where onshore flow off the cooler shelf waters
will hold temps in the lower/mid 60s.

GFS/ECMWF do not agree on the evolution of shortwave energy by the
time it arrives here in the SE part of the CONUS. GFS is very
progressive, passing the energy over us, and off the SE coast by
Saturday evening. The GFS solution has very little, if any, surface
REFLECTION associated with this energy, and only a CHANCE of a few
showers. ECMWF is slower and stronger with its shortwave. This
solution does show a surface reflection/front moving into our
northern areas Saturday night. For now did not choose to follow this
solution which would keep SHOWER chances in the forecast Saturday
night. In fact, will continue to follow the GFS pattern through the
early portion of next week, as the ECMWF becomes somewhat
questionable. GFS keeps our area with a general southerly low level
flow underneath a zonal to ridged upper level pattern. This would
suggest above NORMAL temperatures for Sunday and Monday. Can not
rule out a few isolated showers embedded with the southerly flow,
however a generally dry forecast will also be shown.


&&

.MARINE...The descending ASCAT pass at 1914z showed much of the
coastal waters (except the two eastern nearshore segments) with
15-20 KNOT winds. In fact, there were some values around 20kt in
our western offshore zone. Both of the buoys just outside our
marine zones were reporting 17-19kt winds, so the scatterometer
data is probably pretty accurate. Thus, winds have been slower to
decrease than models have indicated. The "Small Craft Exercise
Caution" headline will be continued into Tuesday morning for all
but the two eastern nearshore segments. Although the central
segments may see winds decrease briefly in the evening, they are
expected to increase once again after midnight. After a brief
lull, there are likely to be SCEC conditions again late Tuesday
Night and early Wednesday as the cold front comes through. With
respect to sensible weather, we added patchy FOG to the nearshore
zones from 18z Tuesday to 18z Wednesday where RH was above 85% in
the forecast GRIDS. This timeframe encompasses a surge of higher
dewpoints in the 60-62F range (compared with observed water temps
of 58F and 56F at Panama City and Apalachicola respectively).


&&

.AVIATION [through 18z Tuesday]...Mid and upper clouds will
continue to impact area terminals into Tuesday. However,
prevailing conditions are expected to remain VFR. There is some
possibility of brief MVFR conditions at KECP and KDHN after 12z
Tuesday.


&&

.FIRE WEATHER...Relatively moist onshore flow will continue into
Wednesday ahead of an approaching cold front. This will keep
HUMIDITY values well above critical levels, as well as provide some
RAINFALL late Tuesday into Wednesday. Much drier AIR will push in
behind the front for Thursday with humidity values dropping into the
20s for much of the region.