Area Forecast Discussion
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FXUS62 KKEY 261913
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
315 PM EDT THU MAR 26 2015

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST IR
IMAGERY AS OF 200 PM OVERLAID WITH MODEL STREAMLINE ANALYSIS DEPICTS
THE AXIS OF A DEEP LATE WINTER SEASON POSITIVELY TILTED TROUGH AXIS
EXTENDING FROM ONTARIO SOUTH SOUTHWESTWARD TO WEST TEXAS. DOWNSTREAM
OF THAT FEATURE...SOUTH FLORIDA AND THE FLORIDA KEYS REMAIN BENEATH
THE NORTHERN EXTENSION OF A DEEP AND WARM ANTICYCLONE LOCATED OVER
THE WESTERN CARIBBEAN SEA...BUT MIDDLE LEVEL...500 MB HEIGHTS ARE
SLOWLY FALLING AT THE KEYS RELATIVE POSITION TO THE APPROACHING
TROUGH. TO THE NORTHWEST OF THE KEYS...200 MB UPPER DIVERGENCE IS
LOCATED WITH INCREASED MID LEVEL PVA(POSITIVE VORTICITY ADVECTION)
(AT 500 MB) JUST SOUTH OF THE NORTH CENTRAL GULF COAST. AS SUCH
VISIBLE SATELLITE IMAGERY DETAILS THE SOUTHEASTWARD MOVEMENT OF A
LARGE OUTFLOW WITH LIGHTNING OVER THE NORTH CENTRAL GULF OF MEXICO

AT THE SURFACE AND IN THE LOWER TO MID LEVELS...SURFACE TO 700
MB...LATEST AVAILABLE SATELLITE IMAGERY OVERLAID WITH MARINE AND
LAND SURFACE OBSERVATIONS AND ANALYSIS AS OF 200 PM...DETECT A 1028
MB ANTICYCLONIC RIDGE FROM THE CENTRAL TO SOUTH PLAINS. A SURFACE
COLD FRONTAL BOUNDARY IS FROM THE OHIO VALLEY TO JUST OFF THE TEXAS
COAST...WITH CLUSTERS OF STRONG TO SEVERE STORMS ACROSS THE
NORTHEASTERN AND NORTH CENTRAL GULF OF MEXICO...AND ANOTHER CLUSTER
FROM OFF OF LOUISIANA TO JUST AHEAD OF THE FRONT

.CURRENTLY...SKIES ARE MOSTLY SUNNY ACROSS THE ISLANDS. TEMPERATURES
HAVE WARMED INTO THE MIDDLE 80S WITH DEWPOINTS IN THE MID 70S. THE
PREFRONTAL TROUGH/AND ASSOCIATED MCS ACROSS THE NORTH CENTRAL GULF
IS RESULTING IN STRONGER WINDS THAN ANTICIPATED...BLOWING 15 KNOTS
AND GUSTY ACROSS ALL OF THE WATERS...EXCEPT 19 KNOTS AT SOMBRERO KEY
LIGHT...SIGHTED HIGHER ABOVE THE WATER...WITH WINDS NEAR 15 MPH AND
GUSTY ACROSS THE KEYS. RADAR IS FREE FROM ANY SHOWERS ATTM.

.SHORT TERM...A LATE SEASON BREECH OF COOLER AND DRIER AIR WILL MOVE
ACROSS THE KEYS AND ADJOINING WATERS LATE TOMORROW NIGHT. ALTHOUGH
THE AIR BEHIND THE ACTUAL SURFACE FRONT WILL BE ACCOMPANIED BY MUCH
DRIER YET SLIGHTLY COOLER AIR...WHICH WILL LAST FROM SATURDAY THRU
THE MIDDLE OF NEXT WEEK...WE EXPECT THAT WINDS WILL COME DOWN THIS
EVENING A BIT...WITH GENTLE SOUTH BREEZES EXPECTED LATE THIS EVENING
THROUGH FRIDAY MORNING. SOME SHOWERS MAY ARRIVE LATE TONIGHT GIVEN
ENOUGH LOWER LEVEL CONFLUENT FLOW AHEAD OF A PREFROTNAL SYSTEM BUT
MAIN ACTION SHOULD ARRIVE DURING FRIDAY. GIVEN INCREASE IN
POPS...HAVE RAISED POPS FOR THE SECOND HALF OF TONIGHT

WINDS WILL CLOCK TO WEST AGAIN AND INCREASE DURING FRIDAY
AFTERNOON...AND WE ANTICIPATE A LINE OF STRONGER SHOWERS...SOME WITH
LIGHTNING...TO MOVE ACROSS THE KEYS DURING THE AFTERNOON. EXACT
TIMING IS TRICKY WITH THESE TYPES OF SYSTEMS. LATEST NUMERICAL
STATISTICS COMBINED WITH THE SYNOPTIC SCENARIO IN PLACE DO SUGGEST
THAT ELEMENTS OF A PRE FRONTAL TROUGH WILL ARRIVE DURING THE
AFTERNOON. HIGH TEMPERATURES WITH SOUTHWEST WINDS WILL BE ABOVE
NORMAL...EXPECTED TO REACH THE MIDDLE TO UPPER 80S WITH HI HUMIDITY.
AGAIN...MODELS USUALLY HAVE TROUBLE WITH THESE TYPES OF
SYSTEMS...BUT GIVEN SUDDEN INCREASE IN AVAILABLE MOISTURE...MODEL
FORECAST PWAT BETWEEN 1.50 AN 2.00 INCHES AND ASSOCIATED
INSTABILITY WITH THE APPROACHING LARGE SCALE TROUGH...500 MB
TEMPERATURES AROUND -12C. SO HAVE INCREASED POPS INTO THE LOW LIKELY
CATEGORY FOR TOMORROW AFTERNOON. THIS IS CLOSER TO THE OLDER OUTPUT
FOR THE ECMWF MOS.

IN TERMS OF EXPECTED CONDITIONS. DO EXPECT DUE TO SOME FAST MOVING
SHOWERS. LOOKS LIKE THE MAIN THREAT WILL BE SOME WIND GUSTS IN
EXCESS OF 35 OR 40 KNOTS AND DEFINETLY SOME LIGHTNING...AS WELL AS A
SHORT PERIOD OR TWO OF MODERATE TO HEAVY RAINFALL DURING THE
AFTERNOON AND EVENING.

SHOWERS AND THUNDERSTORMS WILL END FROM NORTHWEST TO SOUTHEAST
DURING FRIDAY EVENING...HOWEVER...THERE REMAINS SURFACE TO 700 MB
MOISTURE IN THE COLUMN IMMEDIATELY PRECEDING THE SURFACE FRONTAL
BOUNDARY EXPECTED TO MOVE ACROSS THE KEYS BY MIDNIGHT. SO HAVE GONE
WITH HIGH CHANCES FOR SHOWERS DURING FRIDAY EVENING. STRONG COOL
HIGH PRESSURE OVER THE UPPER MIDWEST ON SATURDAY WILL SLIDE TO THE
CAROLINA COAST ON SUNDAY...THENCE MOVE INTO THE WESTERN ATLANTIC
DURING MONDAY...WITH A WEAKER RIDGE JUST NORTH OF THE KEYS TUESDAY
THROUGH THURSDAY. HI TEMPERATURES ONLY IN THE MID 70S SATURDAY AND
SUNDAY AND UPPER 70S ON MONDAY WILL STILL BE BELOW NORMAL...WITH NO
CHANCES FOR MEASURABLE RAINFALL. TEMPERATURES WILL RETURN TO NORMAL
FOR THE MIDDLE AND LATER PARTS OF NEXT WEEK. WILL KEEP OUT RAIN
CHANCES STILL BECAUSE INDICATIONS ARE THAT THE AIR WILL BE TOO DRY.

&&

.MARINE...GENTLE TO MODERATE WINDS EXPECTED THIS EVENING AND THE
FIRST HALF OF FRIDAY. SMALL CRAFT WILL NEED TO EXERCISE CAUTION
ACROSS ALL WATERS FRIDAY AFTERNOON...AND A SMALL CRAFT ADVISORY IS
LIKELY FOR FRIDAY NIGHT THROUGH SATURDAY ACROSS ALL
WATERS...POSSIBLY SATURDAY NIGHT. A SMALL CRAFT ADVISORY WILL STILL
BE IN EFFECT FOR THE FLORIDA STRAITS FOR SUNDAY THROUGH POSSIBLY
MONDAY...WITH CAUTION CONDITIONS ELSEWHERE. THE WEEKEND WILL NOT BE
FAVORABLE FOR RECREATIONAL BOATING.

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL AT THE ISLAND TERMINALS
OVERNIGHT. SURFACE WINDS WILL BE OUT OF THE SOUTHEAST NEAR 10 KNOTS
AND GUSTY...TURNING SOUTHWEST TOMORROW MORNING.


&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  74  84  70  74 / 30 60 50 -
MARATHON  74  88  69  75 / 30 60 50 -

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...NONE.
&&

$$

PUBLIC/MARINE.........FUTTERMAN
AVIATION/NOWCASTS.....11
DATA COLLECTION.......CHESSER

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