Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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000
FXUS62 KTBW 310718
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
318 AM EDT THU JUL 31 2014

.SHORT TERM (TODAY AND TONIGHT)...
THE PRECIPITABLE WATER FROM YESTERDAY EVENINGS 00Z TBW SOUNDING
WAS 1.31 COMPARED TO MFL SOUNDING OF 2.32. MOISTURE IS STILL DEEP
ENOUGH OVER AND OFFSHORE OF LEE COUNTY WHERE WIDELY SCATTERED
SHOWERS AND STORMS CONTINUE TO DEVELOP.

TODAY WILL BE THE LAST OF THE ABNORMALLY DRY DAYS...AND EVEN THEN
THAT WILL ONLY BE FROM ABOUT HILLSBOROUGH/POLK COUNTIES NORTHWARD.
THE UPPER-LEVEL TROUGH TO OUR WEST WILL SHARPEN UP A BIT TODAY
ALLOWING THE ATLANTIC RIDGE TO BUILD BACK TOWARD THE SOUTHWEST. THE
DIFFUSE FRONTAL BOUNDARY OVER SOUTH FLORIDA WILL BEGIN TO EDGE
NORTHWARD DURING THE AFTERNOON...WITH SHOWERS AND THUNDERSTORMS
LIKELY DEVELOPING ALONG THE LEADING EDGE OF HIGHER MOISTURE
CONTENT. WE COULD SEE SOME LOCALLY HEAVY RAINS TODAY FROM EASTERN
CHARLOTTE AND LEE COUNTIES NORTHEASTWARD THROUGH HIGHLANDS COUNTY.

WITH THE NORTHWARD ADVANCEMENT OF THE REMNANT FRONTAL BOUNDARY
TONIGHT...EXPECT TO SEE SHOWER AND THUNDERSTORM ACTIVITY LINGERING
UNTIL AT LEAST MIDNIGHT...AND POSSIBLY LONGER. MOST FAVORED AREAS
FOR EVENING SHOWERS WILL BE FROM LEE COUNTY NORTHWARD THROUGH POLK
COUNTY. SINCE MUCH OF THIS AREA WILL HAVE EXPERIENCED RAIN ALREADY
DURING THE DAY...I WOULD NOT EXPECT COVERAGE TO BE ALL THAT
EXTENSIVE. DEEP-LAYERED RIDGING WILL HAVE NOSED IN ACROSS
SOUTH-CENTRAL FLORIDA BY FRIDAY MORNING RESULTING IN A RETURN TO
MORE TYPICAL SUMMER-TIME CONDITIONS.

.MID TERM (FRIDAY AND SATURDAY)...
LONGWAVE PATTERN FOR THE END OF THE WEEK WILL REMAIN UNCHANGED WITH
A DOMINANT WESTERN RIDGE AND A PERSISTENT (SOME MIGHT SAY STUBBORN)
EASTERN CONUS TROUGH. GENERALLY SPEAKING ANY MEASURABLE SYNOPTIC
INFLUENCE FOR LIFT ASSOCIATED WITH THIS TROUGH...ALONG WITH THE MAIN
ASSOCIATED BELT OF WESTERLIES ALOFT WILL REMAIN TO OUR NORTH AND
NORTHWEST THROUGH THE PERIOD. WHILE THE REMAINDER OF THE EASTERN
CONUS IS UNDER THIS TROUGH...THE FLORIDA PENINSULA WILL SEE MORE
INFLUENCE FROM AN UPPER RIDGE THE EXTENDS FROM THE WESTERN
ATLANTIC...SOUTHWEST OVER THE PENINSULA INTO THE SOUTHEAST GULF OF
MEXICO.

AT THE SURFACE...MAIN RIDGE AXIS WILL BE WELL TO OUR NORTHEAST OVER
THE WESTERN ATLANTIC...WITH AN INVERTED TROUGH AXIS/SURFACE
REFLECTION ASSOCIATED WITH THE TROUGHING ALOFT EXTENDING FROM THE
NORTHERN GULF COAST TO THE CAROLINA COAST. THIS FAIRLY COMPLEX
PATTERN SHOULD RESULT IN A SE/ESE LOW LEVEL SYNOPTIC FLOW ACROSS THE
MAJORITY OF THE PENINSULA. THIS SOUTHEAST FLOW WILL BECOME MORE
DEFINED OVER TIME AND LIKELY HELP SET UP AN ACTIVE PERIOD OF DIURNAL
THUNDERSTORMS...ESPECIALLY ON SATURDAY WHEN THE FLOW WILL BE
STRONGEST. SYNOPTIC FLOW WITH AN EASTERLY COMPONENT IS THE FAVORED
FLOW FOR ENHANCED SEA-BREEZE CONVERGENCE AND CONVECTIVE COVERAGE
ALONG THE FLORIDA WEST-COAST WITH A BIAS TOWARD LATE DAY/EVENING
STORMS. THAT BEING SAID...SATURDAY DOES NOT LOOK LIKE AN OVERLY WET
DAY...AS WE WILL LIKELY SEE FAIR WEATHER FOR MUCH OF THE DAY IN ANY
ONE LOCATION...HOWEVER THOSE PLANNING OUTDOOR ACTIVITIES FOR THE
SECOND HALF OF THE DAY SHOULD HAVE THUNDERSTORM CONTINGENCY PLANS AS
WELL. THIS IS KIND OF TRUE FOR MOST DAYS IN THE SUMMER AROUND THESE
PARTS...BUT WITH THE EASTERLY FLOW...THE LATE DAY COVERAGE OF STORMS
HAS A BETTER CHANCE OF BEING NUMEROUS IN NATURE.

TEMPS ARE LOOKING SEASONABLE WITH MAINLY LOWER 90S FOR HIGHS AND 70S
FOR LOWS. MAY SEE A FEW UPPER 60S FOR PORTIONS OF THE NATURE COAST
EARLY FRIDAY MORNING...BUT INCREASING MOISTURE BY THE WEEKEND SHOULD
PREVENT ANY STATIONS FROM DROPPING BELOW 70 SATURDAY MORNING.

&&

.LONG TERM (SUNDAY THROUGH NEXT WEDNESDAY)...
SYNOPTIC PATTERN PORTRAYED BY BOTH THE GFS AND ECMWF FOR THE SECOND
HALF OF THE WEEKEND BECOMES MORE MESSY AND ILL-DEFINED. UPPER TROUGH
OVER THE EASTERN CONUS TENDS TO DIP A BIT FURTHER SOUTH OVER THE
NORTH-CENTRAL GULF OF MEXICO. THE RESULT OF THIS IS TWO-FOLD.
FIRST...THE UPPER RIDGE RETREATS BACK TO THE EAST A BIT AND LEAVES
OUR REGION IN A WEAKLY DEFINED ZONE TO THE EAST OF THE MAIN TROUGH
AXIS...AND ALSO THE GFS/ECMWF BOTH SHOWS SOME WEAK SURFACE TROUGHING
DEVELOPING OVER THE EASTERN GULF OF MEXICO. THIS WEAK SURFACE TROUGH
MAKES THE PRESSURE PATTERN MESSY AT THE SURFACE AND MAKE PREDICTING
THE DOMINANT LOW LEVEL FLOW DIRECTION MUCH MORE DIFFICULT. ONE THIS
IS CLEAR ON BOTH THE GFS/ECMWF...AND THAT IS THAT THERE REALLY IS
NOT ANY NEGATIVE FACTORS FOR HIGH COVERAGE OF THUNDERSTORMS ON
SUNDAY. PLENTY OF COLUMN MOISTURE IN PLACE...AND LITTLE TO NO UPPER
LEVEL SUPPRESSION. WILL SHOW HIGHER THAN CLIMO RAIN
CHANCES...ESPECIALLY IN THE AFTERNOON AND SLIGHTLY COOLER TEMPS IN
ANTICIPATION OF MORE CLOUD COVER.

GOOD AGREEMENT BETWEEN THE GFS/ECMWF THAT THE UPPER RIDGE WILL THEN
BUILD BACK OVERHEAD DURING THE MIDDLE PORTION OF NEXT WEEK...AND
STRENGTHEN. AFTER ANOTHER ACTIVE CONVECTION DAY ON MONDAY WITH ABOVE
CLIMO RAIN CHANCES...TUESDAY LOOKS TO BE THE TRANSITION DAY AS THE
INFLUENCE OF THE UPPER TROUGH ON OUR WEAKER BEGINS TO DISSIPATE.
WEAK LITTLE TROPICAL IMPULSE CURRENTLY OVER THE CENTRAL ATLANTIC IS
SHOWN BY BOTH GUIDANCE MEMBERS TO SLIP IN UNDER THE BUILDING RIDGE
TOWARD THE BAHAMAS BY LATER MONDAY OR TUESDAY...BUT AT THIS POINT
LOOKS TO HAVE LITTLE TO NO IMPACT ON OUR REGION AS THE UPPER FLOW
THEN FORCES THE ENERGY NORTH AND THEN NORTHEASTWARD AWAY FROM THE
CONUS. THE BIGGER STORY BY THE MIDDLE AND LATER PORTION OF NEXT
WEEK (ASSUMING THE PATTERN FORECAST BY THE GFS/ECMWF VERIFIES) IS
THAT A STRONG RIDGE CENTERED OVER THE PENINSULA WOULD SUGGEST SOME
HOT TEMPERATURES...AND THE SUPPRESSIVE FACTORS AND WARM TEMPS ALOFT
WOULD BE RATHER HOSTILE TOWARD DEEP CONVECTION. WILL SHOW TEMPS A
BIT WARMER THAN GUIDANCE BY WEDNESDAY AND RAIN CHANCES LOWER THAN
GUIDANCE AS CLIMO WILL BE PLAYING A SIGNIFICANT INFLUENCE ON THESE
MOS NUMBERS THIS FAR INTO THE FORECAST PERIOD.

&&

.AVIATION...
MOST TAF SITES WILL REMAIN VFR THROUGH AT LEAST 16Z TODAY. WE COULD
SEE PATCHY SHALLOW GROUND FOG AT LAL AND/OR PGD FOR A COUPLE OF
HOURS THIS MORNING...BUT CONFIDENCE TOO LOW TO INCLUDE IN TAFS.
FMY...RSW...AND PGD MAY SEE SOME BRIEF IFR CONDITIONS AFTER 16Z IN
SCATTERED THUNDERSTORMS.

&&

.MARINE...
WEAK WIND FLOW WILL REMAIN OVER THE COASTAL WATERS THROUGH THE
WEEKEND WITH WIND DIRECTIONS AND SPEED BEING DICTATED BY SEA
BREEZE/LAND BREEZE CIRCULATIONS EACH DAY/NIGHT. A WEAK SURFACE
TROUGH WILL APPROACH THE WATERS FROM THE SOUTH ON SUNDAY AND MOVE
SLOWLY NORTHWEST THROUGH THE WATERS DURING MONDAY. WINDS MAY BECOME
MORE SOUTHERLY DURING MONDAY BUT NO SIGNIFICANT INCREASE IN SPEED IS
FORECAST AT THIS TIME. SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS COULD IMPACT THE WATERS BEGINNING ON SUNDAY AND
CONTINUING INTO MONDAY.

&&

.FIRE WEATHER...
MIXING HEIGHTS WILL REACH UP TO 6000 FEET OVER THE NATURE COAST
WHERE DRY AIR WILL REMAIN IN PLACE TODAY. DEEP ENOUGH MIXING COULD
RESULT IN LOWER THAN FORECAST DEW POINTS THIS AFTERNOON RESULTING IN
A FEW HOURS OF RELATIVE HUMIDITIES NEAR OR BELOW 35 PERCENT. RED
FLAG CONDITIONS ARE UNLIKELY TODAY.

MOISTURE WILL RETURN FROM SOUTHEAST TO NORTHWEST ON FRIDAY WITH NO
FIRE WEATHER ISSUES EXPECTED THROUGH THE FIRST PART OF NEXT WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  92  76  92  77 /  10  10  40  30
FMY  93  75  92  76 /  50  20  60  30
GIF  94  74  93  75 /  20  20  60  40
SRQ  91  74  91  76 /  10  10  40  30
BKV  94  68  93  72 /  10  10  50  30
SPG  92  78  92  79 /  10  10  40  30

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GULF WATERS...NONE.

&&

$$

SHORT TERM/AVIATION/MARINE/FIRE WEATHER...JILLSON
MID TERM/LONG TERM/DECISION SUPPORT...MROCZKA





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