AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
500 AM EDT Thu Jul 5 2012
SYNOPSIS and Short Term (through Saturday)...
Although POPS ended up being a little higher (~20%) on the 4th of
July than we expected last NIGHT (especially over the FL Big Bend
and Panhandle and SE AL), the early start to the CONVECTION
certainly payed dividends for those with outdoor plans for the
afternoon and evening hours, AS most of the activity was over with
before the majority of the 4th of July festivities and fireworks
were underway. Given the fact it was very difficult to make an
accurate deterministic FCST until nearly the very last moment, we
believe the situation worked out quite well.

As has been anticipated for the past several days now, as the Upper
Level RIDGE which brought our region the recent Heat Wave builds
further off to our NW over the Plains, the N-NW FLOW from the Upper
TROF Axis will setup across the CWA today and bring with it more
UNSETTLED conditions. This will LIKELY consist of Sea Breeze induced
showers and storms heading inland from late this morning into the
afternoon hours, with possibly more organized convection pushing
southward from later in the afternoon and evening. Whether or not we
see a well organized MCS develop this evening or tonight is still
uncertain at this time, but even with a favorable pattern in place
for MCS development, it is quite possible that convection earlier in
the day could sufficiently stabilize the ATMOSPHERE and limit later
activity from forming.

On Friday, while earlier in the week it appeared very likely that
the Trof along the Gulf Coast would remain well established with
another very unsettled day, it now appears that the GFS, NAM, and
ECMWF all want to break it down a bit earlier than previously
expected. Nevertheless, we will still carry 30-40% PoPs in the
afternoon, but HIGH TEMPS appear poised to return to the middle 90s
away from the coast.

By Saturday, the Upper Level Pattern is expected to become even more
diffuse, which should favor Hot and Humid conditions with mainly
afternoon Sea Breeze induced showers and storms. At this time, have
reduced PoPs to 20-30% from N to S across the CWA.

&&

.LONG TERM [Saturday Night through next Thursday]...There is fairly
high confidence in the overall evolution of the synoptic pattern
over the CONUS from Sunday into Tuesday. Models are in fairly good
agreement in this timeframe, with the 05.00z runs of the operational
GFS and ECMWF showing 500mb heights within 10m of each other over
most of the area east of the continental DIVIDE. The large, strong
upper-level ANTICYCLONE will develop westward into the Intermountain
West, while a SHORTWAVE TROUGH currently evident on water vapor
loops over British Columbia should eventually dig into the Great
Lakes on the backside of the retrograding ridge. This process should
carve out a broad trough over the eastern CONUS. Much of the
MID-upper level HEIGHT falls, and strongest JET stream winds, should
be well off to the north near the Canadian border. Therefore, the
northern portion of the trough should be fairly progressive while
the southern extent could linger over the Southeast. The amplifying
trough from Sunday into Monday should be accompanied by a cold FRONT
pushing south through the Ohio River Valley and into the Southeast.
HPC and many of the global models then stall the front somewhere
near or just north of our area for the remainder of the week, with
an ill-defined upper level trough axis situated west. This would
place our area in increasingly deep southerly flow, a pattern that
favors unsettled weather and increasing MOISTURE.

Overall, not many changes were made to the extended forecast. PoPs
for Sunday and perhaps Monday should continue to be dictated more by
sea-breeze effects. Therefore, the PoPs Sunday-Monday remain a blend
of sea-breeze CLIMATOLOGY and HPC Guidance. With more sporadic CLOUD
cover well out in advance of the front, highs were kept a little
warmer (mid 90s away from the coast). For Tuesday into Thursday,
there should be increasing influence from synoptic-scale forcing
mechanisms. This will likely result in more cloud cover, higher RAIN
chances, and slightly cooler temperatures. Highs were nudged down
into the lower 90s closer to climatological normals.

&&

.Marine...A continuation of the typical summertime pattern of light
winds and LOW SEAS appears to be in the cards for the bulk of the
Coastal Waters Forecast, although an Upper Level Trough approaching
from the north will increase the chances for showers and
thunderstorms over the Marine Area for today and Friday.

&&

.AVIATION...[through 06z Friday]...
Mid-level cloud cover had quickly dissipated early tonight, and
satellite and surface observations show that areas of FOG and low
CIGS are beginning to SET in, particularly further west. IFR will be
possible closer to SUNRISE, but for now we conservatively only took
TLH and VLD down to MVFR given that fog seems to be developing more
off to the west. Some brief reductions close to airport minimums
can`t be ruled out at some of the other terminals (DHN, ABY, ECP) -
and this has already been observed recently at DHN. While SCATTERED
afternoon thunderstorms are expected, confidence in timing is low.
Right now the thinking is that earlier activity (prior to 20-21z)
will be concentrated closer to ECP in the western FL Panhandle, and
the other terminals may be affected more in the late afternoon or
early evening. For now, just VCTS was included.

&&

.FIRE WEATHER...No fire weather concerns are anticipated for today
or Friday as relative HUMIDITY should remain above 40%. Some
interior areas of the Florida Panhandle may see relative humidity
approach 35% on Saturday, but critical fire weather conditions are
not currently anticipated. Increasing moisture and rain chances are
on tap for the following week.