AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
411 AM EST Wed Nov 14 2012

.NEAR TERM [through Tonight]…
Shallow northeasterly FLOW below a lingering frontal INVERSION (AS
sampled by surface observations and RADAR VWPs) continues across
the Southeast region. The moist northeast flow in the lowest 1km
has aided the PROPAGATION and development of a STRATUS layer into
our forecast area from coastal Georgia and South Carolina. The
vast majority of BUFR forecast soundings from the operational
forecast models, as well as individual SREF members, indicate that
the shallow, moist layer near the surface will persist through the
day as the flow in that SAME layer pivots to the ENE/E. In fact,
the SREF TEMPERATURE and dewpoint profiles below 2km show very
good agreement today, deviating mostly less than 2C from the
ENSEMBLE MEAN. Therefore, it is not surprising that the SREF and
NARRE ensemble probabilities of a CLOUD CEILING less than 3000 FT
at 18z today are over 80% over much of our forecast area. Putting
it all together, confidence has increased that we will see a
stratus layer persist through tonight, which should restrict the
DIURNAL temperature RANGE and keep highs today from the MID-50s
along our northern border, to the mid-60s in the I-10 corridor.

Meanwhile, increasing southerly flow just above the frontal
inversion in advance of a digging SHORTWAVE TROUGH should lead to
increasing isentropic ascent across the area today. In general,
guidance POPS have increased over the past several model runs.
The majority of the 4km WRF runs (local and NCEP) develop fairly
WIDESPREAD showers late in the morning and through the evening.
Thus, PoPs were trended up. In the weather GRIDS, the showers
were paired with patchy DRIZZLE wording north of I-10 today. Model
forecast soundings show some slight UVV coincident with the
saturated layer (stratus) in these areas. Overall, a cool and
CLOUDY day is expected with occasional light drizzle or showers
developing by late morning.

&&

.SHORT TERM [Thursday Through Friday]…
The OUTLOOK” onClick=”return popup(this, ‘notes’)”>OUTLOOK for the end of the work week is for slightly cooler
than NORMAL temperatures to prevail, with drier weather and a bit
more sunshine. The northeast flow in the lowest 1km AGL” onClick=”return popup(this, ‘notes’)”>AGL appears
LIKELY to continue, and it could anchor a cooler LOW-level AIR
mass in the area. Differences arise in the forecast soundings,
with the GFS dissipating the frontal inversion and the NAM
maintaining it with the potential for low stratus to linger into
Friday. Although that is a possibility (and would lead to cooler
temperatures than are currently forecast), the uncertainties led
us to opt for a blended consensus at this time.

&&

.LONG TERM [Friday NIGHT through next Wednesday]…
The large scale longwave pattern that commences the period is
highlighted by trough with axis just off West Coast, and split flow
over East half of CONUS with ridging over NRN states, and troughing
over SRN states with low becoming CUTOFF from nrn branch of JET
stream over WRN KY. At surface, strong HIGH over NRN PA with RIDGE
axis SWWD across entire Gulf region.

During the rest of the period, pattern becomes highly amplified.
Several shortwave over upper Midwest dive SEWD and deepen trough
over SE region THRU the weekend. Then the EURO and GFS diverge with
former placing cutoff low near Gulf Coast and thus wetter solution
and latter shows low across CNTRL Appalachians and drier solution so
overall confidence regarding latter part of extended not high. For
now will blend but lean towards drier solution. So trough and assocd
low pivot into TN Valley early SAT then REACH” onClick=”return popup(this, ‘notes’)”>REACH NRN GA late Sat
providing a little upper MOISTURE, but its impact will be mainly
clouds and over our NRN counties. Then low slowly lifts offshore by
early Mon allowing strong ridging to expand EWD into Gulf region
keeping local area on west or dry side of trough with dry N/NE flow
aloft. Then trough gets nudged NEWD with quasi-zonal flow aloft into
Wed.  At surface high PRESSURE will move ENE and be reinforced over
New England with ridge holding firm thru Tues. At same time,
amplified trough near Cuba combines with Conus trough to induce
CYCLOGENESIS off Carolina Coast beginning Sat night. The combination
of strong New England high and Carolina low will reinforce offshore
flow over NE Gulf before low retreats NEWD allowing some Gulf
moisture return on Wed.

Forecast continues to be mostly dry one and will go with NIL POPS
except for WDLY SCT shwrs on Wed. MIN TEMPS will hover slightly
below CLIMO until rising to climo Tues night. With strong NLY flow
dominating extended period, expect MAX temps to run several degrees
below normal for mid-November. AVG inland min/max is 45/70 degrees.

&&

.AVIATION [Beginning 09Z Wednesday]…
MVFR with OCNL IFR cigs will linger thru most of the period as
moist northeast flow persists and low stratus becomes trapped
under inversion. Isentropic lift will generate some showers or
more likely occasional drizzle or sprinkles around the area, with
CAM/WRF/local confidence tool all show best CHANCE at KABY, and
lesser chance at KDHN and KVLD mainly after 16z. For now will
include -DZ at KABY, elsewhere the chance did not appear quite
high enough to include in the TAFs at this time.

&&

.MARINE…
The strong offshore flow appears to have peaked around 05-06z and
has since fallen to just below 15 knots. Therefore, the FEW hours
of SCEC conditions over most of the waters have generally abated,
and the headline has been removed with the most recent CWF
issuance. Offshore flow will continue through the entire CWF
period (through Sunday) with some SCEC conditions possible during
some of the overnight periods – particularly around the weekend.

&&

.FIRE WEATHER…
Strong high pressure will build north of the region through
Thursday. this will yield persistent low clouds and a cooler and
more moist airmass over the region. This will maintain relative
humidities well above critical levels as well as low mixing heights
and dispersions. The airmass will begin to dry out on Friday with
red flag humidities possible over the weekend, especially across the
inland Panhandle.

&&

.HYDROLOGY
Light RAIN or drizzle is expected over portions of the area over
the next 24 hours, but total RAINFALL is expected to be limited.
QPF should be less than 0.4 inches across the area, and therefore
no significant fluctuations in river levels are forecast.