Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 111052
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
652 AM EDT Sat May 11 2013
.NEAR TERM [through This Afternoon]...
Updated at: 650 AM EDT
The overall progression of the weather elements in the near term
appears to be on track. The HRRR and RAP continue to perform best
with the position and timing of upstream convective activity. We
still expect rain and some thunderstorms to gradually spread into
the western part of our area around 16 UTC, and then affect the rest
of the area through the remainder of the afternoon. The best chances
for rain still appear to be in the Florida Panhandle and Big Bend,
and the immediate adjacent row of counties in south Georgia. Thus,
no major changes were made - although the thinking with respect to
severe weather potential has changed slightly.
Objective analysis continues to show a pseudo-warm front or surface
pressure trough from just off the Louisiana coast to near our
offshore buoy (42039). This is supported by a noticeable thetae
gradient and wind shift offshore. Not surprisingly, this is also the
zone where the strongest convection has been developing upstream.
Given the current position of the mesoscale boundary offshore, we
may see the most intense storms today focused over the coastal
waters. This is a theory that is supported by recent high-resolution
model runs, with strongest average updraft strengths over the Gulf.
Therefore, most of our land areas could just see some general rain
showers with some embedded thunderstorms.
However, we still have to be wary of several scenarios that could
bring stronger thunderstorms to our land areas. First, the boundary
could surge north into the Florida Big Bend, which would support an
isolated severe weather threat in our Florida zones east of the
Apalachicola River. Second, the eastern part of our area could
receive greater insolation and heating ahead of the advancing cirrus
shield from the upstream convection. This could support a ribbon of
greater instability east of a line from AAF-ABY, and scattered
storms could develop in the weakly capped environment as large scale
forcing increases ahead of the advancing mid-level MCV associated
with the current convection near coastal Louisiana. Either way, the
situation still seems to indicate a threat for isolated strong or
severe storms - but mainly in southern and eastern areas.
.SHORT TERM [Tonight through Monday]...
The 00 UTC NWP guidance continues to forecast an unusually deep
longwave trough over the eastern CONUS Sunday and Monday. The PoP
will decrease from northwest to southeast Sunday as dry air
advection develops. The highest PoP, 30-40%, will be from
Tallahassee southward and eastward tonight and Sunday, with the PoP
decreasing below 10% Sunday evening. The core of the cooler and
drier airmass won`t reach our forecast area until Monday. Highs on
Sunday will be in the lower 80s, but only in the 70s (below average)
Monday. Lows on Monday morning will be in the 50s (also below
average). The low humidity and relatively breezy conditions on
Monday will make it feel quite pleasant for mid May, when it usually
begins to get warm and humid.
.LONG TERM [Monday Night through Friday]...
Deep layer ridging will build into the region for the middle of the
week followed by a low amplitude trough late Thursday into
Friday. There will be a slight to low end chance of rain on
Friday, otherwise the extended period will be dry. The week will
begin with below normal temperatures and gradually moderate to
seasonal levels by Thursday. The coldest temperatures will be
Tuesday morning when upper 40s to around 50 degrees are forecast.
.AVIATION [Through 12 UTC Sunday]...
Updated at: 650 AM EDT
Mid-high level cloud cover has cleared out, leading to some patchy
fog and low stratus across the area around sunrise. This is most
established at DHN and ECP where CIGS are near or below airport
minimums. Elsewhere, flight categories should remain in the MVFR or
IFR range. Fog and low stratus should generally lift by mid morning.
Rain will spread into the area from west to east, first affecting
DHN and ECP around 16 UTC. There may be a few thunderstorms, but
confidence was not high enough to include in a prevailing group.
Scattered storms would be most likely between 18-00 UTC at TLH and
VLD. Low CIGS may develop again tonight. For now kept things MVFR.
Aside from the increased rain chances, weekend boaters will be
treated to low winds and seas (outside of scattered thunderstorms).
This will change Sunday night as the rather strong area of high
pressure builds across the Southeast behind a cold front, causing
winds to increase to 15 to 20 KT. These offshore winds may remain at
exercise caution levels through Tuesday morning.
Wetting rains are expected over a good portion of the area today.
Drier air will arrive behind a cold front on Sunday Night with very
low RH for May expected on Monday. Despite the minimum RH around
25%, other fuel-dependent red flag criteria may not be met. Thus,
while red flag conditions seem somewhat uncertain, there is high
confidence that Monday will be a breezy, dry day with high
The 00 UTC WPC 5-day rainfall accumulation forecast continues to
show our between one half and one inch over our forecast area,
mainly this weekend, and with the highest totals west of
Tallahassee. None of the experimental hydrologic ensembles forecast
minor flooding for our river forecast points over the next several
days. The maximum of maximum 6-hour QPF amounts from the various
Convection Allowing Models (CAM), a worst case scenario, show
isolated narrow bands of 3-4 inches. Neither the area coverage or
magnitude of these values would indicate enough of a threat for a
flash flood watch for today`s rain.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 83 66 82 53 80 / 70 40 30 10 0
Panama City 77 67 81 57 78 / 70 40 20 10 0
Dothan 81 63 79 50 78 / 70 40 10 0 0
Albany 85 64 81 50 76 / 60 40 10 0 0
Valdosta 86 64 81 52 77 / 70 40 30 10 0
Cross City 84 66 82 57 80 / 40 30 40 10 0
Apalachicola 79 67 79 59 76 / 60 30 30 10 0