NWS Tampa released a good discussion:
000
FXUS62 KTBW 200109
AFDTBW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
809 PM EST THU FEB 19 2015
.UPDATE...
VERY TRICKY TEMPERATURE FORECAST OVERNIGHT. 925MB TEMPERATURES ARE
ABOUT AS COLD AS THEY ARE GOING TO GET. THAT SAID...THEY DON`T
RISE MUCH BETWEEN NOW AND SUNRISE FRIDAY MORNING...MAYBE 2 OR 3
DEGREES CELSIUS. THIS IS UNLIKELY TO HAVE A BIG IMPACT ON SURFACE
TEMPERATURES SINCE WE CERTAINLY WILL NOT MIX TO 925 OVERNIGHT. RAW
MODEL GUIDANCE...PARTICULARLY OUR LOCAL WRF MODELS...ARE NOT AS
COLD AS MOS GUIDANCE. MOS GUIDANCE WILL DO BETTER IN TRUE
RADIATIONAL COOLING ENVIRONMENT WHILE RAW MODEL OUTPUT WILL OFTEN
BE BETTER WHEN THE BOUNDARY LAYER REMAINS MIXED.
LETS GET ONE THING OUT OF THE WAY NOW. THE PATCH OF RATHER DENSE
CIRRUS MOVING ACROSS CENTRAL FLORIDA WILL NOT IMPACT OVERNIGHT
LOW TEMPERATURES. THE BACK EDGE WILL BE MOVING AWAY FROM OUR AREA
BY 9 PM OR SO...WITH CLEAR SKIES RETURNING TO THE REGION.THE NORTHWESTERLY WINDS WILL GRADUALLY SHIFT TO THE NORTH AND
NORTHEAST. OVERNIGHT. WE WILL SEE VERY LITTLE INFLUENCE FROM THE
WARMER GULF AWAY FROM THE IMMEDIATE COAST.
D
EW POINTS ARE GOING TO PLUMMET ONCE THE WINDS SHIFT. EXPECT TO
SEE DEW POINTS BETWEEN 10 AND 15 DEGREES TOWARD SUNRISE...EVEN
LOWER OVER THE NATURE COAST.
LOW TEMPERATURES UPSTREAM FROM US LAST NIGHT WERE IN THE MID TEENS
TO MID 20S.
THE MAIN NEGATIVE FACTOR FOR VERY LOW TEMPERATURES IS THE WIND.
THE HIGH CENTER WILL BE WAY TO THE NORTH TONIGHT...OVER KENTUCKY.
NORMALLY THIS WOULD KEEP A RATHER TIGHT PRESSURE GRADIENT OVER THE
REGION WITH A GOOD NORTHEASTERLY RETURN FLOW. BUT IN THIS CASE...
THE AIRMASS IS COLD ENOUGH THAT WE WILL SEE A RIDGE EXTENDING
SOUTHWARD ACROSS THE STATE AS COLD AIR DRAINAGE BEGINS. THIS
SHOULD RESULT IN AN EARLY DECOUPLING OF THE ATMOSPHERE THIS
EVENING FOLLOWED BY A GRADUAL INCREASE AGAIN AS THE COLD AIR
DRAINAGE TAKES OVER.TAKING ALL OF THIS INTO ACCOUNT...LOW AREAS AWAY FROM THE COAST
WILL BE ESPECIALLY SUSCEPTIBLE TO VERY COLD TEMPERATURES TONIGHT.
WHILE URBAN AREAS AND RIDGES MAY REMAIN JUST ABOVE FREEZING...
INLAND LOW AREAS COULD EASILY FALL THROUGH THE MIDDLE 20S. OUR
BIGGEST CONCERN IS OVER THE NATURE COAST WHERE WINDS COULD GO CALM
FOR SEVERAL HOURS TOWARD MORNING. SHOULD THIS OCCUR...WITH CLEAR
SKIES AND LOW DEW POINTS...TEMPERATURES WOULD FALL INTO THE MIDDLE
TEENS.
THIS ALSO LOOKS LIKE A GOOD SETUP FOR A VERY COLD MORNING AROUND
ARCHBOLD IN HIGHLANDS COUNTY. WOULD NOT BE SURPRISED TO SEE PARTS
OF SOUTHERN HIGHLANDS COUNTY DOWN TO NEAR 20 DEGREES OR SO...BUT
THIS WOULD ONLY BE OVER A VERY SMALL AREA OF THE COUNTY.
SOME MINOR TWEAKS WERE MADE TO THE FORECAST...BUT I HAVE NOT
TOUCHED OUR TEMPERATURE FORECAST AT ALL. OUR 8 PM FORECAST
TEMPERATURES ARE JUST ABOUT RIGHT ON CURRENT OBSERVATIONS. ZONES
WILL BE UPDATED TO REMOVE HEADLINES OF EXPIRED ADVISORIES.
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