Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 121408
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1008 AM EDT Sun May 12 2013
.NEAR TERM [Through Tonight]...
As of 14Z, area radars were still quiet. The lead cold front
extended from near VLD to near AAF. The air mass ahead of this
front is still characterized by mid to upper 60s dew points. There
will still be a small chance of an isolated shower or two ahead of
this lead cold front in the southeast part of our area, although
we have postponed any shower development until the afternoon. High
resolution guidance appears to be very consistent on the idea of
this being relatively shallow convection with weak updrafts.
Therefore, no thunderstorms are forecast at this time. PoPs remain
capped at 20%. Highs today will be warmest in the southeast,
ranging from mid-80s there to upper 70s in the northwest. Very few
changes were necessary to the grids this morning other than the
aforementioned slight delay in shower development.
.SHORT TERM [Monday Through Tuesday]...
The peak of the anomalously deep long wave trough over the eastern
CONUS will be Monday afternoon, when the trough`s axis will extend
from eastern Canada to the northeast Gulf of Mexico. 500 mb heights
are then forecast to rise nearly 100 meters over our forecast area
by Tuesday afternoon. With an extremely dry column and sinking air
aloft, clouds (other than a few high, thin CI) will be difficult to
come by. Our low temperature forecast for tonight is slightly
warmer than the MOS consensus, as MOS frequently goes too cold
immediately behind a cold front (when the winds don`t go calm and
mixing prevents rapid cooling). Highs will "only" reach the mid to
upper 70s on Monday, which is closer to what we would expect in
late March. We think the "coldest" morning will be on Tuesday, as
a high pressure ridge becomes centered over northwest FL. The
tightly-clustered MOS consensus calls for record lows in the mid
40s at our normally coldest sites, away from the coast and cities.
This includes the Tallahassee airport. A warming trend will begin
Tuesday as highs reach 80 degrees.
.LONG TERM [Tuesday Night through Saturday]...
The period will begin with an upper level trough pulling away to
the northeast and short wave ridging building in from the west.
The upper ridge axis will reach our zones on Wednesday and then be
shunted to the east by the next trough that will impact the area
late in the week. The GFS is more diffuse than the Euro with the
energy in this system and also more progressive. At the surface,
high pressure will drop south across the area on Tuesday and then
remain in place just south of the area through the period. This
ridge will work to hold off any would be shower activity until
Friday and Saturday when a front will approach from the north.
Look for 20-30 PoPs on those days. Max temps will be near normal
(mid 80s) through the period. Overnight lows will be a bit below
normal Tuesday night and then return to normal after that time.
[Through 12Z Monday] The IFR conditions observed at TLH and ECP
at TAF issuance (and the MVFR at VLD) will all lift/scatter to VFR
by 13Z...14Z at the latest. After that, VFR will then prevail
through through the remainder of the TAF period.
The pressure gradient remains rather loose this morning, despite
the approaching cold front. This will change later tonight however
as the pressure gradient tightens considerably behind a second cold
front. It will be close, but the NWP guidance wind speed consensus
keep our sustained winds a knot or two below advisory levels (20
KT). Winds and seas will subside a bit on Monday, but then
increase to exercise caution levels again Monday night.
A drier air mass is expected over much of the area today except the
Florida Big Bend, with RH possibly reaching the low 30s in some
areas. However, this will not be sufficient to meet any red flag
criteria. On Monday, red flag conditions cannot be ruled out,
particularly over Florida. There remains some uncertainty on winds
and ERC levels, but RH will be low enough. Red flag conditions seem
unlikely in Alabama and Georgia due to KBDI and fuel moisture
Rainfall totals on Saturday were minuscule, so we don`t expect any
hydrology issues for the next several days.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 83 54 78 45 80 / 10 0 0 0 0
Panama City 81 58 78 56 78 / 10 0 0 0 0
Dothan 79 50 74 50 82 / 0 0 0 0 0
Albany 80 50 75 47 80 / 0 0 0 0 0
Valdosta 85 53 76 46 79 / 10 0 0 0 0
Cross City 83 59 78 45 80 / 20 10 0 0 0
Apalachicola 81 59 76 52 76 / 20 10 0 0 0