Near Term [Through Tonight]...
Water vapor imagery this evening shows a stream of upper level
moisture across the area, but the 00z KTAE sounding reveals a
layer of extremely dry air between about 830-600 mb.
Therefore, although area radars show some light echoes in the Gulf streaming northeastward, this precip is not likely to hit the ground for
several more hours until the dry layer moistens.
The hi-res guidance does show this eventually happening late tonight with scattered light precip towards dawn, but this may be a bit
overdone given the magnitude of the dry layer seen in the
The previous forecast showed only a 20 PoP for light showers late tonight over portions of the area, and this still seems reasonable.
With high clouds streaming into the area, the forecast is also on the warmer side of guidance tonight for low temperatures, and very few changes were made.
Short Term [Thursday Through Saturday]...
The large scale pattern commences on Thurs with a slow moving
positively tilted trough over Srn most Plains into Desert SW and
another trough over Ern most Great Lakes and NE states.
A series of short wave troughs will translate quickly EWD across CONUS and periodically increase lift across local region.
The initial one, albeit weak passes to our north during the day.
Another Srn stream shortwave will become largely cutoff from strong WLYS aloft over SW TX and begin to drift Ewd. This leaves SE region under weak quasi-zonal flow with hint of moistening SW flow by sundown...with increasing high clouds aloft.
At the surface, high centered to our NE and another high pressure centered near Mid-MS Valley with ridge Swwd to Srn Plains and NEWD to TN/OH Valleys.
The combination of high to our ME yielding NELY low level flow and passing impulse to our north will yield M/Cloudy skies and a small chance of rain mainly Ern counties closest to departing shortwave.
Forcing too weak for any Tstms.
In wake of shortwave, local airmass will dry out briefly as reflected in model soundings. i.e. GFS TAE with 1.09 inch PWAT at 12Z Thurs decreasing to 0.71 inch PWAT at 00Z Fri.
The airmass will begin to moisten again Thurs night.
Above Srn stream trough is forecast to deepen across SE TX thru MO/AR on Fri and across ArkLaTex on Sat with closed low developing at base.
Srn stream shortwave moves further Ewd across Nrn Gulf thru Sat. In
response, plume of deep layer moisture to our west increasingly
being pulled Newd with swath of isentropic generated low level
moisture (from Gulf front see below) increasingly encroaching
across Ern gulf Ewd across coastal counties and into Wrn Atlc.
By Fri, local upper flow becomes more SWLY atop cool NNE flow and
along with deeper moisture profile (PWATS increasing to above 1
inch), Q-G forcing and increased divergence increase ahead of this
trough with a corresponding increase in PoP.
Models diverge on strength of trough, position of shortwave and Nwd/Ewd extent of moisture plume.
However, enough confidence to increase rain chances on Fri into Fri night, especially along and south of a line from Valdosta to Cape San Blas, as isentropic lift from lifting warm front increases.
North of this line it will probably be too dry for rain on Friday. Even where rain is possible, we expect it to be too stable and the forcing too weak for Tstms. Our QPF and PoP remain low.
On Sat, uncertainty in forecast with respect to timing and intensity
of fairly strong shortwave moving Ewd across Gulf plus GFS/ECMWF
show surface wave developing in Cntrl Gulf on warm frontal
Boundary likely lifts Nwd from Srn to Cntrl FL Peninsula by end of day as wave lifts newd along it and this should provide additional source of moisture especially if it interacts with passing shortwave.
Stronger GFS brings front Nwd overland and if this solution verifies, heavy rain and tstms likely.
For now will favor weaker ECMWF solution keeping front closer to coast and not mentioning Tstms.
Overall, guidance points to high rain POP with highest chances Srn third of forecast area.
Area PWATS increase to 1.5-1.7 inches but total QPF less than 2 inches for event so will not mention any flooding concerns at this time.
Expect 0-20% NW-SE POP gradient on Thurs, 0-40% NW-SE gradient Thurs night thru Fri, then 30-50% and 40-60% N-S gradients Fri night and Sat respectively.
Temp forecast tricky as passing impulses and assocd clouds could wreak havoc on forecast highs and lows.
For now...Highs Thurs and Sat mid-upper 50s north to mid 60s SE Big
Bend, and on Fri upper 50s to low 60s.
Lows Thurs night from mid 30 SE AL to mid to upper 40s SE Big Bend, Fri night from upper 30s N to low to mid 40s S.
Long Term [Saturday Night To Wednesday]...
Latest guidance continues shows upper trough and assocd shortwave should advance east of the region before sundown Sun with assocd front passing just south of Big Bend.
Surface wave should exit NE FL/SE GA on Sat night with some trailing moisture.
This translates to a continued high rain POP Sat night into Sun morning before rain ends from NW-SE with departing disturbance.
Locally heavy rain possible into Sun if upper/lower features set up (see short term discussion above).
In its wake, it appears that the upper level pattern will become very progressive, with a couple of fast moving shortwave trofs moving through the region during rest of period.
At surface, in wake of front, ridge will briefly stretch from east coast S then SW into NW Gulf.
However, a shortwave will move across on Mon kicking another albeit weak cold front across bringing a very small chance of rain. In its wake high pres moves quickly across GA Mon night and SC on Tues so expect a reinforcing shot of cooler temps especially at night with a wetter airmass returning Wed, Jan 1.
Will go with 40-70% NW-SE POP gradient sat night, 20-50% on Sun,
otherwise nil pops.
Lows Sat night from 40 N to low 50s S, Sun night upper 30s N to low-mid 40s S dropping Mon and Tues nights to low-mid 30s.
Highs Sun 60 N to 69 S, Mon 58 to 65, Tues 56 to 63 and Wed 60
Just some minor tweaks to the previous package, but it is now clear that solid isentropic lift is now taking place across the terminals in the MVFR layer, so expect MVFR Cigs to dominate the Tafs for most of this cycle.
Improving conditions back to VFR are likely to occur from W to E later in the day on Thursday, even though this may be a short lived
proposition, as moisture begins to return from the east and then
west for the end of the week and upcoming weekend.
So, we may just see brief periods of favorable flying conditions, before another soaking rain hits the region before the New Year begins.
Moderate northeast winds are likely to continue for the next several
days as a series of high pressure systems develop to our north.
Then...a weak low will develop in the western gulf then lift northeast across ne gulf.
Expect winds to increase to likely exercise caution offshore Fri into Sat before decreasing to light to moderate in its wake.
Divided CWF into nearshore and offshore to account for higher winds..seas and POPs offshore.
Humidity will continue to moderate through the rest of the week.
Red flag conditions are not expected.
The Apalachicola River at Blountstown is expected to remain in minor flood stage through the weekend with releases from Woodruff Dam.
The Kinchafoonee Creek`s crest near Dawson has been revised
downward again and is forecast to just barely reach minor flood
stage late Thursday night and drop below minor flood stage on
The Choctawhatchee River at Caryville may briefly touch minor flood stage on Friday, but that remains uncertain.
Early projections on rainfall this weekend are in the 1-2" range.
This should help to keep rivers elevated for the next several days.
Preliminary Point Temps/PoPs...
Tallahassee 46 60 42 60 42 / 20 20 20 20 40
Panama City 46 60 46 61 45 / 10 10 10 10 40
Dothan 39 57 37 60 40 / 10 10 10 0 30
Albany 42 57 37 58 39 / 20 20 10 10 30
Valdosta 45 58 41 59 42 / 20 20 20 20 50
Cross City 50 66 47 61 45 / 10 20 40 40 60
Apalachicola 49 61 49 61 48 / 20 20 30 20 40