NATIONAL WEATHER SERVICE TALLAHASSEE FL
516 AM EDT Fri Apr 4 2014
Near Term [Through Today]...
Conditions have been quite interesting across the Tri-State area
overnight, as a small but stubborn "bubble ridge" of high pressure
over SE portions of the region has lead to slightly cooler and less
cloudy conditions over the FL Big Bend.
With low level conditions also moistening, an area of Dense Fog has formed over the FL Big Bend, and a Dense Fog Advisory has been issued from Leon and Wakulla counties eastward until 14 UTC this morning.
Elsewhere across the region, SE-S winds have remained a bit elevated with milder and more humid conditions, resulting in some light fog but generally more widespread low CIGS.
Expect the fog and these CIGS to slowly lift today, but widespread clearing does not appear likely at this time.
Therefore, for temps and high temps, went with a blend of the CAM
guidance with the previous package, resulting in slightly cooler
temps across the board today.
Highs should range from the lower 70s along the immediate coast, to the upper 70s to lower 80s inland, with a few middle 80s over eastern sections of SC GA and the Suwannee River Valley of the FL Big Bend where some clearing could take place before the day is through.
Also, by later this afternoon, some convection could develop across the NW 1/3 of the region as a weak squall line to our NW gradually approaches, but maximum rain chances should be limited to 30-40 percent.
Short Term [Tonight Through Sunday]...
As mentioned in the near term discussion, there may be some
showers and thunderstorms in the northwest half of the area this
The 00z operational GFS is more aggressive with QPF overnight, while the convection resolving WRF models, 00z ECMWF, and 00z NAM show a noticeable decreasing trend in QPF by the evening hours.
Forcing will be getting weaker with time, and there is a fair amount of consistency between various 4km WRF runs, indicating a sizable decrease in updraft velocities in storms near the NW part of our area around 00-02z.
Therefore, we expect that some scattered showers and storms will move into the area tonight, but that intensity and coverage should quickly diminish around or just after sunset.
There is a small chance of a strong storm or two in the evening, and steep mid level lapse rates could support some hail in stronger storms.
The front is expected to stall on Saturday across some part of the
area, and consensus seems to be roughly from PAM-TLH-VLD by 18z.
To the southeast of the stalled front, the NAM and GFS suggest
MLCAPE around 500-1000 j/kg with about 40 knots of shear, so some
stronger storms can`t be ruled out.
It should be a fairly warm day, with mid-70s north of the front, and low 80s south.
From Saturday Night into Sunday, the surface front will remain
somewhat stationary or drift slowly north.
As a trough digs into Texas, low-level mass response over the Gulf coast region will contribute to the gradual development of a broad 25-40kt southerly low level jet.
Increased isentropic ascent north of the surface front should lead to a band of rain and embedded thunderstorms.
The mesoscale details will ultimately determine where this band of
moderate to heavy rain ends up, but current model consensus places
it very near the northern edge of our forecast area.
Based on this, we trended PoPs up to the "likely" range (60-70%) in those areas from Saturday Night into Sunday, with a more restricted
diurnal temperature range (lows in upper 50s, highs in low 70s).
Long Term [Sunday Night Through Friday]...
The aforementioned warm front will move north of the forecast area
Sunday night as the western CONUS trough (and associated cold
front) approach from the west.
The GFS and ECMWF forecast a pre-frontal squall line to traverse our region late Sunday night through early Monday afternoon.
Although SBCAPE values may not be very high (around 500 J/kg), strong Q-G forcing, 0-6 km bulk shear magnitudes of 50-60 kt, and 0-1 km bulk shear magnitudes of 30 to 40 kt suggest that some of the storms within the squall line could be severe, with damaging winds and/or isolated tornadoes.
Although the cold front be past our region Monday night, clouds and at
least a slight PoP will linger into Tuesday night as a strong short wave rounds the base of the broader long wave trough developing over the eastern CONUS. (Sound familiar)?
Fair weather is expected for the remainder of the week, although temperatures will be below average.
As mentioned above, Dense Fog has formed at TLH in response to the weak Sfc ridge, and this fog is expected to linger beyond sunrise before slowly lifting.
Elsewhere at the terminals, a mixture of fog and low cigs has combined to produce widespread IFR to LIFR conditions which will be slow to recover to MVFR levels by early this afternoon.
A brief period of VFR conditions will be possible at the Taf sites later this afternoon, before deteriorating aviation rules return to all of the sites once again by this evening.
This will likely be the pre-cursor to yet another night dominated by widespread IFR to LIFR levels which should gradually return to all of the terminals.
Also, with a slowly approaching, but weakening squall line, added a convective tempo late today at DHN, and may consider the same possibility slightly later at ABY.
Relatively benign winds and seas are expected over the coastal
waters through early Sunday, despite some longer period swell that
will keep wave heights around 2-3 feet for the next 24 hours or
An increase in winds will arrive later Sunday as a cold front approaches.
SCEC winds seem quite likely, with advisory level winds of 20+ knots also possible.
Winds should veer to the northwest and decrease behind the front on Monday.
Increasing low level moisture and rain chances will preclude any
fire weather concerns at least through Tuesday of next week.
Two rivers remain in minor flood stage.
The Choctawhatchee River at Bruce will continue rising but stay in minor flood stage, cresting late tonight.
The Apalachicola River at Blountstown is still in minor flood stage and should fall below flood stage late tonight.
The next period of rain across the region will arrive Friday night
and continue periodically through Monday, with heavy rain at
For the Friday night through Monday period expect widespread totals from 2 to 3 inches with locally higher amounts likely.
This additional rainfall will cause rises on already full rivers and tributaries next week.
In particular the basins of the Choctawhatchee, Apalachicola, and Ochlockonee will likely be affected.
For the latest river stages and forecasts, please visit:
Preliminary Point Temps/PoPs...
Tallahassee 79 63 80 62 80 / 10 30 50 30 30
Panama City 73 64 76 64 73 / 20 30 50 30 40
Dothan 80 60 76 60 72 / 40 40 40 60 70
Albany 81 62 77 59 72 / 20 30 40 50 60
Valdosta 84 63 80 60 81 / 10 30 50 30 30
Cross City 79 60 81 59 82 / 0 10 30 20 10
Apalachicola 72 65 74 64 73 / 10 30 50 30 30
FL...Dense Fog Advisory until 10 AM EDT this morning for Coastal
Dixie-Coastal Franklin-Coastal Jefferson-Coastal Taylor-Coastal Wakulla-Gadsden-Inland Dixie-Inland Franklin-Inland Jefferson-Inland Taylor-Inland Wakulla-Lafayette-Leon-Liberty-Madison.