AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
348 AM EST Thu Nov 8 2012

…First FROST of the season expected tonight…

.NEAR TERM [Through Tonight]…
Cooler weather continues to remain entrenched across the region
with the LIKELY first frost of the season coming tonight.
Observational data from 00 UTC Thursday and throughout the morning
hours continues to show a strong cold/dry ADVECTION pattern AS the
upper TROUGH across the Eastern CONUS lifts northeast into New
England. At the surface, HIGH PRESSURE back across the MID
Mississippi Valley will shift southeastward into the Southern
Appalachians by the evening. With this particular synoptic SET up,
temperatures will not warm that much today despite full sunshine.
In fact, highs will not be that dissimilar to Wednesday`s values
that were only in the mid 60s.

The big story in the near term is with temperatures Thursday NIGHT
into Friday morning. Clear skies, and CALM winds will support
excellent radiational cooling overnight. The latest guidance has
trended a little colder than the inherited forecast down into the
lower 30s in some spots. With this cooler shift and UPSTREAM
observations showing the incoming airmass quite cold will trend
the inherited forecast down a degree or two. T/TD spreads are
around 3 or 4 degrees MAX overnight. With all this in mind, it
looks to be more than cold enough for areas of frost to develop
by daybreak on Friday. In fact, it wouldn`t be entirely
surprising to see a FEW spots hit the freezing mark (the MAV
guidance at TLH is 33 – which usually indicates some of the
normally colder areas in the Florida Big Bend should hit 31-32).
Because of the ISOLATED and conditional nature of freezing
temperatures, will not be issuing any FREEZE products at this
time. However, will have frost mention in the forecast products
and let the day shift define the area of the frost ADVISORY that
will almost certainly be issued later today.

From a purely climatolgical standpoint at Tallahassee, there`s
around a 70 percent CHANCE of a frost by November 9th and around a
30 percent chance of a freeze by November 9th. The record LOW for
Friday at Tallahassee is 21 set back in 1976.

&&

.SHORT TERM [Friday Through Saturday]…
No real sensible weather throughout the short term period.
Temperatures will begin to slowly warm on Friday as ridging aloft
builds across the Southeast. With the RIDGE amplifying on
Saturday, temperatures will return to above NORMAL values with
highs in the upper 70s. Low temperatures during the period will
moderate enough to prevent any frost concerns on Friday night.
Even warmer overnight temperatures are expected Saturday night.

&&

.LONG TERM [Sunday through Wednesday]…
The deep layer ridge over the Southeast on Sunday will break down
as a weakening cold FRONT moves southeast across the forecast area
Monday night and Tuesday. The GFS and ECMWF both show this system
getting “stretched” out in the deep layer MOISTURE/QPF fields, as
the associated 500 MB HEIGHT falls remain north of our region.
With this weakening, the max POP for is only 30%. The front is
likely to stall across central FL Wednesday as a frontal wave
begins to develop in the western Gulf of Mexico, so this may not
be a “clean” frontal passage. The above-average temperatures
(especially daytime highs- which will be well into the 70s) ahead
of the cold front Sunday and Monday will give wave to near average
temperatures behind the front Tuesday and Wednesday.

&&

.AVIATION [Beginning 06Z Thursday]…VFR conditions will continue
through the period at all of the terminals, with very light winds
overnight, much lighter N-NW winds on Thursday, followed by near
calm conditions Thursday night. With the SFC Ridge building in, no
additional CLOUD cover is expected through the next 24 hours.

&&

.MARINE…While the much cooler and drier AIR that is still rushing
in over the Marine Area is helping to maintain the Small Craft
Advisory over the western two-thirds of the Coastal Waters, the
pressure GRADIENT is starting to weaken as the High Pressure Ridge
approaches from the northwest. This Ridge will allow winds and SEAS
to subside steadily throughout the day, with much lighter offshore
winds by this afternoon. Light northeast then easterly winds will
continue through Friday, with 10 to 15 KNOT winds expected by Friday
night and Saturday as they veer to the southeast. Winds and seas
will increase further by the latter half of theĀ  weekend, as the
High Pressure system moves eastward off the U.S. Eastern Seaboard,
and a new Cold Front approaches from the west. This will likely
result in a period of at least cautionary conditions over the
waters.

&&

.FIRE WEATHER…With very dry air moving into the region today, low
afternoon relative humidities and high ERCs will result in Red Flag
Conditions across Leon and Wakulla counties in the Florida Big Bend.
With very similar conditions expected on Friday, and potentially
higher ERCs over parts of the Florida Panhandle, will issue a Fire
Weather WATCH for a larger area. Over our Georgia and Alabama
counties, afternoon relative humidities may drop below 25% on
Friday, but durations should be brief.