Special Weather Statement, NWS Tallahassee, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
330 PM EDT Thu May 31 2012

.SYNOPSIS...
Surface analysis shows ridging over the northern plains and a surface
low located over northern Ark. with associated cold front
extending into eastern Texas and warm front extending over Tenn.
The 12z sounding showed good lapse rates, dry air aloft, and
plenty of CAPE to kick off thunderstorms this afternoon. As the
cold front pushes east, it will bring with it a more favorable
synoptic scale environment for thunderstorms tomorrow.

&&

.NEAR TERM...(REST OF TODAY AND TONIGHT).
Showers and thunderstorms are continuing to develop along the
seabreeze front which is currently pushing inland. With CAPE values
up over 2000 J/KG, thunderstorms have shown the potential for hail
and gusty winds. Better forcing due to an upper level trough will
continue to move into the area over the afternoon and evening.
Hi-res guidance also suggests that a MCS could form and move into
the area over the late night hours. Therefore, we have raised POPS
to around 30 percent for the overnight, in the event that some
isolated thunderstorms continue to linger. Temperatures are already
into the 90s and max temps should reach into the mid 90s this
afternoon. Tonight southwesterly flow and additional cloud cover
from an approaching system will keep minimum temperatures a bit
warmer than yesterday.

.SHORT TERM...(FRIDAY THROUGH SATURDAY NIGHT).
Model guidance is in good agreement through the short term period.
Strong upper level wave across the Upper Mississippi River Valley
will drop into the Ohio Valley on Friday afternoon as a surface low
pressure area moves quickly northeastward up the Western
Appalachians. This will push a cold front across the Southeast and
into the Mid Atlantic through the first part of the short term
period. Thereafter, the models are in good agreement with an overall
trough-type pattern across the Eastern CONUS through the remainder
of the period, yielding dry and somewhat cooler conditions than
we've seen for the last couple of days.

Friday...Some uncertainty here at the first part of the day. A
couple of the hi-res guidance members indicating early morning MCS
activity will be ongoing across our western zones at daybreak. While
this can't be ruled out ahead of the surface frontal boundary, it
looks more likely scattered showers will develop late morning and
spread eastward ahead of the cold front. As the trough and cold
front move eastward, the overall environmental flow will strengthen.
This stronger flow combined with decent instability from mid morning
Friday into Friday afternoon, will increase the potential for
organized severe storms, particularly across Southern Georgia and
perhaps into portions of North Florida, which should be ahead of the
cold front from 15z to 21z. As the cold front sweeps through, the
potential for strong to severe storms will come to an end. Opted for
forecast pops about 10 to 15 percent higher than MOS given the good
agreement with the timing of the afternoon storms in the models.

Saturday...Drier conditions will overspread the region in the wake
of the cold front. Guidance is in good agreement that a mid level
impulse will move through the region within the large scale trough
creating some mid level cloudiness on Saturday. The lack of any
substantive return flow off the Gulf of Mexico will prevent the
development of any showers and thunderstorms.

Temperatures throughout the period will begin to trend cooler and
potentially drop below normal on Saturday. The guidance splits a bit
with respect to low temperatures on Saturday morning with a few
sites dropping into the upper 50s behind the cold front. This seems
a little bit extreme given how much of the cooler air behind the
system looks to be transported into the Ohio Valley and not deep
into the South. So stayed on the warmer side of the guidance in this
portion of the forecast.

.LONG TERM...(Sunday through Thursday).
It appears to be a fairly uneventful extended fcst for much of the
upcoming period, despite the persistent presence of an upper level
trof down the U.S. Eastern Seaboard. Sfc High Pressure should help
keep conditions warmer and drier than normal for Sunday and Monday,
before a shortwave trof becomes better established over the SE U.S.
and dampens out the Sfc Ridge or forces it southward into the Gulf
of Mexico. With NW Flow aloft, this may open us up for potential MCS
development from the north on Tue-Thu, in addition to an increase in
the more typical afternoon and evening sea breeze induced showers
and thunderstorms. The GFS, ECMWF, and Canadian are all in fairly
good agreement with the general synoptic pattern, so will plan on
showing gradually increasing PoPs beginning on Tue. Cloud cover will
ultimately determine Max Temps through the period, but we should at
least begin with above normal values, with perhaps a slow
convergence back towards Climo by the end of the period.

&&

.AVIATION...Primarily a VFR forecast for the first few hours of the
TAF cycle. Shower and thunderstorm activity will affect the DHN and
TLH terminals through about 21z. Expect much of the convective
activity to diminish greatly after sunset. Another round of fog
appears possible, but only at VLD where IFR conditions are
indicated. Given the uncertainty with timing of incoming convective
precip will hold off mentioning thunderstorms in the 18z TAFs, but
this will likely be needed in the next set issued later this
evening.

&&

.MARINE...A cold front will move through the waters on Friday
resulting in winds shifting to more of an offshore component. High
pressure will move into the marine area by Saturday resulting in
decreasing winds and seas throughout the rest of the weekend.

&&

.FIRE WEATHER...On Friday, an approaching cold front will bring
increasing chances for showers and thunderstorms which will keep the
relative humidity above critical levels. The next opportunity for
red flag conditions will come when drier air arrives behind the cold
front on Saturday. At this time, red flag criteria is forecast for
the inland portions of the Florida Panhandle and Big Bend due to a
combination of low relative humidity and high values of the energy
release component. A watch or warning will likely be issued by later
shifts.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   71  88  65  89  66 /  30  60  30  10   0
Panama City   75  86  70  87  69 /  30  50  20  10   0
Dothan        72  87  61  89  65 /  30  60  10  10   0
Albany        70  86  62  88  64 /  30  60  20  10   0
Valdosta      71  87  64  87  64 /  30  60  40  10   0
Cross City    70  87  69  88  66 /  20  50  40  10  10
Apalachicola  76  86  70  86  68 /  20  50  30  10   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
AL...None.
GA...None.
FL...None.
GM...None.

&&

Long Term...Gould
Synopsis/Near Term...Walsh/Camp
Rest of Discussion...Godsey