AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
623 AM EDT Thu Nov 1 2012
.NEAR TERM [Through Tonight]…
Updated at 0625 EDT:
A weak surface trough combined with weak upper level shortwave
support have generated light showers, both offshore and closer to
the coast this morning. Just recently, the showers generated
over land have started to reach the ground despite the relatively
dry boundary layer. With the southward motion of the features
expected to continue, expect the threat for showers to shift
offshore by early to mid morning with only a very slight chance
for a shower near the Forgotten Coast into the afternoon. With the
passage of the surface trough, high pressure will build into the
region and combined with the subsidence aloft will dry things out
rather quickly. With heights gradually increasing today, expect a
slightly warmer afternoon than yesterday with highs peaking in the
middle 70s area wide. Overnight, lows will be ever so slightly
warmer than this morning. Expect middle 40s to be common inland,
with middle 50s likely along the coast.
.SHORT TERM [Friday Through Saturday]…
The gradual warming trend will continue into the weekend as the
mean flow becomes more zonal, continuing the rising heights. Above
average temperatures are expected both Friday and Saturday as
lower to middle 80s are expected to creep back into the picture.
Overnight lows will moderate through the 50s, eventually
increasing to above normal levels, into the middle 50s by Saturday
night. No rain is expected through Saturday.
.LONG TERM [Saturday Night through Wednesday]…
There is good agreement among the latest GFS and ECMWF model runs in
transitioning the 500 mb long wave pattern from that of a fairly
zonal pattern over the weekend, to a fairly amplified trough over
the Southeast U.S. by early next work week. This means that our
forecast area will at least have a chance of rain…something that
has been lacking lately. (Although climatologically, October is our
driest month of the year, so the past few weeks have not been that
unusual). The window for rain will be Sunday and Monday, as a cold
front passes through the region. Although there appears to be
sufficient deep layer moisture, Q-G forcing, and instability for
scattered showers (and even a few thunderstorms), the vertical wind
profile and thermodynamics do not appear favorable for an organized
severe storm threat. (November is typically when we begin to be more
vigilant about the threat of severe storms, since the Gulf Coast
severe storm season generally goes from November through March).
A secondary (and fairly impressive) short wave is forecast by both
model runs to translate quickly through our area on Tuesday, but
neither the GFS nor ECMWF MOS carry PoP much above 10%, perhaps
because the initial system scours away much of the deep layer
moisture. Temperatures on Sunday will be well above average (by
about 10 degrees for highs), then return to near average Tuesday and
Wednesday behind the cold front, with Monday being a transition day.
.AVIATION [Beginning 10Z Thursday]…
Updated at 0625 EDT:
The short wave approaching our forecast area this morning has helped
produce more rain than previously forecast, resulting in brief
periods of MVFR vis/cigs at KECP and KTLH. Recent radar trends and
high-res NWP output indicate that these SHRA will taper off from
west to east through mid morning, followed by VFR conditions and
fair weather. Winds will be NW 5 to 10 KT this afternoon, becoming
light by sunset.
Winds will begin to settle today as high pressure builds in over
our coastal waters. Calm winds and seas will continue through
Monday, when a weak cold front could bring a slight enhancement.
With plenty of dry air still in place, and a favorable combination
of winds & mixing heights, we upgraded our Fire Weather Watch to a
Red Flag Warning for all of our FL zones today. Admittedly it will
be marginal in some areas (like Franklin & Dixie Counties), but
there is too much uncertainty to leave anyone off at this point. It
appears that the humidity will be a little above FL`s critical
threshold for Friday, so no watch/warning will be issued.
Since there has been no heavy rain in our region for several weeks,
and since rain is unlikely for the next several days, river stages
will remain below action levels.