NATIONAL WEATHER SERVICE TALLAHASSEE FL
315 AM EDT Sat Jun 28 2014
Near Term [Through Today]...
The main story for today is that conditions should be basically a
repeat of yesterday, except with slightly hotter temperatures.
With deep layer ridging, and a low-level anticyclone centered basically
right over the forecast area, we expect the hot weather with
suppressed convection to continue.
With upper level heights increasing today and negative vorticity advection in the mid-upper levels, it is not too surprising that hardly any models generate any QPF in our area today.
Some of the 4km WRF runs, initialized around 00Z, do show some isolated thunderstorms in the far western and far eastern parts of our area; a 15% PoP has been included in these areas to account for that potential, but most locations should stay dry and mostly sunny through the day.
With respect to temperatures, models show a slight increase in
low-level temperatures and thicknesses in the 24-hour period ending
at 00Z this evening.
The observed 850mb temperature on our 00Z sounding at Tallahassee yesterday evening was 18.6C, and most models increase this to between 19-20C today.
Therefore, we expect highs to be slightly warmer than yesterday when many locations hit the mid-90s.
In fact, historically when we get 19-20C 850mb temperatures with deep mixing in June it correlates well with highs around 99-100 at TLH.
We expect upper 90s to near 100 degree highs today in the
southeast half of our area - especially at TLH and VLD - with mid
90s in the northwest half.
Some heat indices in the upper 90s to around 100 are possible over much of the area.
The highest heat indices (101-103) may be over parts of the Florida Panhandle and Big Bend in the late morning and early afternoon (10 AM to 2 PM), where higher dewpoints and temperatures are more likely to coincide before the sea breeze pushes inland and/or dewpoints mix down too much.
Short Term [Tonight Through Monday]...
Deep layer ridging will prevail across our forecast area through the
period...with above-average 500 mb heights.
The GFS & ECMWF forecast 850 mb temperatures to continue to be well-above average over our area (generally 2 to 2.5 standard deviations above climo), which means hot daytime temperatures in the upper 90s to around 100 deg.
Fortunately there will be enough boundary layer drying to limit heat index values below 105 deg, but it will still be uncomfortable for most warm-blooded animals.
The 1000-700 mb mean wind will be north to northwest near 10 KT, which (as we observed on Friday) will pin most of the Northwest FL sea breeze front at the coast until late afternoon or early evening.
Additionally, the boundary layer drying will depress SBCAPE values to less than 1000 J/kg, which is abnormally low for this time of year.
The suppressed sea breeze front and relatively poor thermodynamics
will keep PoPs at 20% or less.
Long Term [Monday Night Through Saturday]...
The period begins with Gulf ridging shifting Nwd to over SE region and remains in place until beginning to erode late Tues or early Wed as a Nrn stream longwave trough moves Ewd into east half of Conus and then deepens Swd progressively weakening ridge.
At the surface, latest guidance shows that above deepening longwave
trough advances swd into gulf coast states.
This shifts high over N/Cntrl Gulf Wwd while GA Coastal low then shifts further ESE into Atlc, rather then SWWD over land by Tues.
This would favor intensification of low with NHC forecasting a 30% chance of tropical development out thru 5 days.
Forecast confidence not high, as much (rain,clouds/ temps)depends on development of trough aloft and this low.
ECMWF continues to amplify trough noticeably more than GFS which would favor more active convection.
Best scenario is that on Wed, mid trough deepens ESE to Atlc coast and begins to absorb low shifting it ESE towards Bahamas with no area tropical development and steering flow returning to SW.
Passing impulses will enhance Gulf seabreeze yielding a wet pattern.
By Fri, longwave trough begins to lift Newd with return to at or below
climo type weather.
POPS 30-40% on Mon and 30-50% Tues thru Thurs, then 30% on Fri.
Period will be quite warm with highs in the mid to upper 90s with a few spots approaching 100 degrees each day thru Thurs.
Highs on Fri in the low to mid 90s. Lows generally in the low to mid 70s.
VFR conditions will prevail with generally mostly to partly sunny skies.
Afternoon coverage of thunderstorms is expected to be too limited to include in any TAFs at this time, but an isolated thunderstorm will still be possible - particularly at VLD, ECP, and DHN.
An area of high pressure will remain centered southwest of the FL
Panhandle, providing light northwest winds and low seas across the
The exception will be during the afternoon & early evening hours, as strong daytime heating of the land will cause the winds to increase and become west to southwest near the coast.
Despite deep mixing with very high mixing heights over the next
several days, red flag conditions are not expected.
Afternoon minimum RH should be below normal for this time of year, but should not meet red flag thresholds.
All but one river forecast point were below local "action" stages, and this is likely to continue into at least early next week.
Although heavy rain is almost always possible during the summer
months, we expect any heavy rain to be very localized and unlikely
to significantly affect local river stages.
Preliminary Point Temps/PoPs...
Tallahassee 98 72 99 73 99 / 10 0 10 10 20
Panama City 94 77 94 78 94 / 10 10 10 10 20
Dothan 96 73 98 73 99 / 10 10 10 20 20
Albany 96 73 99 73 99 / 10 10 10 20 20
Valdosta 100 72 101 72 101 / 20 10 20 20 30
Cross City 97 73 96 73 96 / 30 10 20 20 30
Apalachicola 94 76 92 78 93 / 10 10 10 10 20