Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 120757
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
357 AM EDT Sun May 12 2013
.NEAR TERM [Today]...
As of 07 UTC, the area radars were devoid of any rain although an
initial weak surface cold front was still approaching our area. The
front`s position at that time appeared to be right near the
northwest corner of our forecast area. The air mass ahead of the
front was still characterized by mid-60s dewpoints. Mid-level clouds
have prevented much fog development despite light winds. With both
global and high-resolution models failing to generate any additional
precipitation through at least 14 UTC ahead of the front, we opted
for a dry forecast through that time. There will still be a small
chance of an isolated shower or two ahead of the cold front in the
southeast part of our area from the late morning into the afternoon.
High resolution guidance appears to be very consistent on the idea
of this being relatively shallow convection with weak updrafts.
Therefore, the forecast only includes rain showers at this time,
with thunderstorms not mentioned. PoPs were capped at 20%. Highs
today will be warmest in the southeast, ranging from mid-80s there
to upper 70s in the northwest.
.SHORT TERM [Tonight through Tuesday]...
The peak of the anomalously deep longwave 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.
.AVIATION [Through 06 UTC Monday]...
Mid level clouds appear as though they might clear prior to 12 UTC
and the lower levels of the atmosphere are still quite moist across
the area. This could support the development of some low stratus or
fog around daybreak. Statistical guidance is very aggressively
portraying LIFR CIGS, but this seems unlikely. For now we have
included general MVFR or high-end IFR CIGS at most of the terminals
prior to 14 UTC. The outlook is VFR thereafter.
The pressure gradient was very flat this early morning, despite the
approaching cold front. This will change later tonight however as
the pressure gradient tightens considerably behind a 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 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 / 10 0 0 0 0
Albany 80 50 75 47 80 / 10 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