AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
733 AM EST Wed Jan 16 2013

…The end of our unusually warm weather is in site, with periods of
rain today into Thursday followed by much colder and drier air…

.NEAR TERM [Through Tonight]…
Our Region will still be in the Warm Sector today, as the strong
Upper Level ridge to the east of the Bahamas will keep the eastward
progress of the developing shortwave over TX to a minimum for one
more day. However, the colder and drier air associated with the Sfc
Cold front is running a bit out ahead of the shortwave, and this is
causing areas of rain to develop over northern and western portions
of the region early this morning, and the PoPs will be significantly
higher further to the north and west throughout the day today. This
rainfall should keep Maximum Temps in the mid 60s to lower 70s to
the N and W, while we will see one more very warm day in the mid to
upper 70s (with a few lower 80s) off to the south and east. By
tonight, this shortwave will have cutoff from the flow over eastern
TX and western LA, before it starts to accelerate eastward. This
will bring increasing rain chances to the entire area tonight, with
significantly cooler air filtering in to the N and W. Lows temps
tonight will span a nearly 20 degree spread, ranging from around 40
over parts of SE AL, to near 60 across the eastern 1/3 of the CWA.

&&

.SHORT TERM [Thursday Through Friday]…
The best rain chances area-wide will be on Thursday morning as the
Upper Low and associated Sfc Cold front sweep through the region. In
fact, the 00 UTC Global models are in very good agreement with a
slightly faster solution than their 12 UTC counterparts, so we expect
decreasing rain chances during the afternoon (possibly even lower
than the current fcst if this trend continues), with no measurable
precip left by Thursday night. Also, with the much cooler air moving
in as well, temperatures are not expected to rise much from the
morning lows, with Highs only ranging from the mid to upper 40s over
much of SE AL to the lower to middle 60s over the SE FL Big Bend. It
will become quite breezy as well, with W-NW winds reaching 15 to 20
mph with higher gusts. This will set the stage for a mostly clear
and cold night for Thursday night into Friday morning, with low
temps near freezing. With Sfc winds remaining elevated along with
high soil moisture, believe a widespread light freeze is unlikely at
this time. Friday should be a mostly sunny and cool day, with Highs
ranging from the Mid 50s to the Lower 60s.

&&

.LONG TERM (Saturday through next Tuesday)…
The latest GFS and ECMWF are in good agreement in forecasting large
500mb height falls over the CONUS (east of the Rockies) early next
week, coupled with plenty of very cold arctic air at the surface.
Saturday through Monday our temperatures will be near average, with
lows in the 30s and highs in the 60s. By Monday night or early
Tuesday, however, an arctic cold front may pass through our forecast
area, setting up a 24-hour period of strong cold air advection. As
is often the case this far out, there are model differences
regarding the details of how cold it could get here, but we have
plenty of time to watch.

&&

.AVIATION…
[Through 12z Thursday] Low cigs across the warm sector are creating
IFR to LIFR conditions early this morning across most of the TAF
sites with KVLD near the eastern edge. Areas of rain are expected to
affect KDHN and KECP through the period, eventually expanding
eastward. An improvement to MVFR cigs is expected during the day
for most areas with a quick dropoff back to IFR around sunset. The
exception is KVLD, which is expected to improve to VFR during the
day.

&&

.MARINE… Winds will be light to moderate out of the South out
ahead of the Cold front today, before shifting to the Southwest then
West from West to East across the Coastal waters late tonight and
Thursday morning. These winds are expected to quickly ramp up to
strong Small Craft Advisory levels on Thursday (with possible Gale
Force gusts), with winds and seas remaining elevated well into
Friday. Offshore winds should finally drop below headline levels on
Friday night.

&&

.FIRE WEATHER…
Abundant low level moisture is expected through Thursday with drier
air moving in behind a cold front on Friday. It now appears as
though relative humidity values will fall below 35 percent across
portions of northwest Florida on Friday afternoon. High dispersions
are also forecast for Friday afternoon, but ERC values are less than
20 over a large portion of the area so red flag conditions are
uncertain.

&&

.HYDROLOGY…
Despite the possibility of heavy rains upstream (well north and
northwest of our forecast area), the latest NHP guidance does not
show significant rises in our rivers this upcoming week. Over our
CWA, Storm Total Rainfall is expected to range from 0.25″ to 0.50″
over the SE half of the region, to between 1″ and 1.5″ over the NW
half.