Red Flag Warning 24, NWS Tampa Bay, FL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
230 AM EDT TUE MAY 17 2011

.SHORT TERM (TODAY THROUGH THURSDAY)...
AN UPPER LEVEL LOW REMAINS OVER THE MID ATLANTIC STATES
THROUGHOUT THE SHORT TERM PERIOD. TODAY...THE LOW CONTINUES TO
SHIFT SOUTHWARD AS A STRONG SHORTWAVE IS RIDING AROUND THE BASE
OF IT. THIS SHORTWAVE GETS ABSORBED INTO THE LOW BY THIS
AFTERNOON BUT WITH THE SOUTHWARD SHIFT...EXPECTING ANOTHER COOL
DAY TODAY WITH TEMPERATURES RUNNING ABOUT 5 TO 7 DEGREES BELOW
NORMAL. COOLER AIR ALOFT PROVIDING SOME MODERATE INSTABILITY
ACROSS THE AREA AND THIS HAS LED TO SOME ONGOING LIGHT
RAINSHOWERS MOVING ONSHORE OVER SOUTHWEST AND SOUTH-CENTRAL
FLORIDA THIS MORNING. THIS ACTIVITY SHOULD BE DIMINISHING TODAY
AS DRIER AIR MAKES ITS WAY INTO THE AREA FROM THE NORTH...BUT
STILL LOOKING FOR A 20% CHANCE OF RAIN FOR AREAS GENERALLY SOUTH
OF TAMPA BAY UNTIL THIS EVENING. ALSO ENOUGH INSTABILITY OVER
SOUTHERN COUNTIES TO CALL FOR THE MENTION OF SOME ISOLATED
THUNDER THIS AFTERNOON WITH SURFACE TEMPS GETTING UP INTO THE MID
80S.

ON WEDNESDAY AND THURSDAY...THE CENTER OF THE UPPER LOW SHIFTS
BACK TO THE NORTH AND WEAKENS. WEAK SURFACE HIGH PRESSURE SHIFTS
IN OVER THE SOUTHEASTERN U.S. DURING THE PERIOD WHICH WILL HELP
TO BRING SOME DRIER AIR IN OVER THE PENINSULA. STILL MAY SEE SOME
CLOUD COVER EACH DAY WITH THE COLDER AIR ALOFT...BUT THIS WILL
ALSO BE CLEARING BY THURSDAY AS WE START TO WARM BACK UP AS THE
TROUGH SHIFTS UP INTO THE NORTHEASTERN U.S. AND A RIDGE
STRENGTHENS OVER THE WESTERN GULF COAST STATES. THIS WILL
TRANSLATE INTO A MARKED WARM-UP OVER THE AREA ON THURSDAY
AFTERNOON WITH TEMPERATURES GETTING BACK UP TO NEAR-NORMAL.

.LONG TERM (THURSDAY NIGHT THROUGH MONDAY)...
AN UPPER LEVEL RIDGE OVER THE MISSISSIPPI VALLEY AND A LOW ALOFT
THE UPPER OHIO VALLY SLOWLY TRACK EAST. THE RIDGE REACHES THE SE
U.S. EARLY SUN AS THE LOW SLIDES OUT OVER THE OPEN ATLANTIC.
MEANWHILE AT THE SURFACE HIGH PRESSURE RIDGES ACROSS FL FROM THE
ATLANTIC. UP TO THIS POINT THE GFS AND ECMWF HAVE BEEN IN FAIRLY
GOOD AGREEMENT BUT THEN DIVERGE MON. THE GFS CONTINUES MOVING THE
UPPER LOW EASTWARD AS THE UPPER RIDGE FLATTENS OVER THE REGION
AND THE SURFACE RIDGE REMAINS ACROSS FL. THE ECMWF HOLDS THE
UPPER LOW OFF THE EASTERN SEA BOARD WITH A BOUNDARY...SUGGESTING
SOME RAINFALL... SAGGING IN FROM THE NORTH AS THE SURFACE RIDGE
MOVES SOUTH. FOR NOW WILL FAVOR THE DRY GFS THROUGH OUT THE
PERIOD AND MAINTAIN A RAIN FREE FORECAST WITH TEMPERATURES
RUNNING AROUND TO JUST ABOVE NORMAL.

&&

.AVIATION...
BKN CIGS THIS MORNING...MVFR FOR TPA/PIE/SRQ BUT VFR AT FMY/RSW.
WDLY SCT SHRA MOVING ACROSS WEST CENTRAL FL NOT EXPECTED TO
IMPACT THE MAIN TERMINALS. CLEARING BEGINS LATE MORNING AS
WESTERLY WINDS BECOME GUSTY AND CONTINUE THROUGH THE AFTERNOON.

&&

.MARINE...
A SURFACE LOW REMAINS OVER THE CAROLINAS TODAY WHICH WILL
CONTINUE THE NORTHWEST WINDS OVER THE EASTERN GULF WATERS. SPEEDS
HAVE BEEN RUNNING BELOW GUIDANCE FOR THE MOST PART BUT ARE
EXPECTED TO INCREASE IN THE MID TO LATE MORNING AS THE SURFACE
LOW SHIFTS BACK TO THE WEST SLIGHTLY. FOR NOW...IT LOOKS LIKE
WINDS SHOULD REMAIN JUST BELOW EXERCISE CAUTION CRITERIA TODAY
AND WILL LEAVE HEADLINES OUT OF THE FORECAST WITH THIS MORNING'S
ISSUANCE. WINDS WILL BE LIGHT (AROUND 10KTS OR LESS) ON WEDNESDAY
AND EVEN LOWER ON THURSDAY AS A HIGH PRESSURE RIDGE SHIFTS IN
OVERHEAD. THIS WILL ALLOW A SEABREEZE TO DEVELOP ON THURSDAY
AFTERNOON NEAR THE COAST.

&&

.FIRE WEATHER...
EXPECT ANOTHER DAY SIMILAR TO YESTERDAY AS FAR AS RELATIVE
HUMIDITIES GO. CLOUD COVER WILL REMAIN OVER THE AREA TODAY AND
TEMPERATURES REMAIN COOL SO RELATIVE HUMIDITIES ARE NOT EXPECTED
TO DROP BELOW 35 PERCENT OVER MOST OF THE AREA. ONLY EXCEPTION IS
UP IN LEVY COUNTY WHERE ENOUGH DRY AIR COULD FILTER IN EARLY TO
DROP RH'S TO JUST UNDER 35% FOR ONE TO THREE HOURS. COMBINED WITH
BREEZY 20FT WINDS...HAVE DECIDED TO ISSUE A RED FLAG WARNING FOR
LEVY COUNTY. EXPECT LOWER HUMIDITIES ON WEDNESDAY AND THURSDAY FOR
AT LEAST FOUR HOURS...SO WILL MONITOR ERC VALUES FOR POSSIBLE RED
FLAG ISSUANCE BOTH AFTERNOONS.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  79  63  81  64 /  10   0   0   5
FMY  85  66  84  65 /  20   5   0   5
GIF  82  58  83  60 /  10   0   0   5
SRQ  80  63  79  62 /  20   0   0   5
BKV  81  49  80  49 /  10   0   0   5
SPG  76  66  78  69 /  10   0   0   5

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 7 PM EDT THIS
     EVENING FOR LEVY.

GULF WATERS...NONE.

&&

SHORT TERM/MARINE/FIRE WEATHER...23/MCNATT
LONG TERM/AVIATION...09/RUDE