Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KKEY 031900
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
300 PM EDT SUN MAY 3 2015

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST
AVAILABLE IR IMAGERY AS OF 200 PM OVERLAID WITH MODEL STREAMLINE
ANALYSIS CONTINUES TO DEPICT MAINLY ZONAL MID AND UPPER FLOW ACROSS
THE WESTERN AND CENTRAL CONUS WITH BROADLY CYCLONIC FLOW ACROSS THE
EASTERN UNITED STATES AS WELL AS THE GULF OF
MEXICO...BAHAMAS...EXTENDING INTO THE NORTHWESTERN CARIBBEAN SEA.
THE SOUTHERN BRANCH OF THE JET CONTAINS THE HIGHEST MAGNITUDE OF MID
AND UPPER WINDS...WITH 75 TO 100 KNOTS AT 250 MB MIGRATING FROM
MEXICO AND CENTRAL AMERICA BUT DECELERATING TO NEAR 50 KNOTS ACROSS
CUBA...SOUTH FLORIDA AND THE KEYS. AT 500 MB....A SIMILAR
DECELERATION IS OBSERVED SYMPTOMATIC IN THE DEVELOPMENT OF A MIDDLE
LEVEL TROUGH/LOW PRESSURE SYSTEM OVER THE CENTRAL GULF.
ADDITIONALLY...SHOWERS AND THUNDERSTORMS ARE DEVELOPING ATTM IN SITU
AT THE POSITION OF THE TROUGH NORTH OF BAHIA HONDA.

AT THE SURFACE AND IN THE LOWER TO MIDDLE LEVELS...SURFACE TO 700
MB...AS OF 200 PM...THE NEAR 1025 MB CENTER OF A STRONG ANTICYCLONE
IS LOCATED OVER THE WESTERN ATLANTIC OCEAN EAST OF SOUTH CAROLINA. A
SURFACE TO 850 MB TROUGH IS ANALYZED ACROSS THE EASTERN GULF OF
MEXICO AT AROUND 86 WEST...AND THERE IS BROAD LOWER PRESSURE ACROSS
THE NORTHWESTERN CARIBBEAN SEA. ALL OF THIS IS GENERATING HEALTHY
SURFACE TO 850 MB WINDS IN THE BOUNDARY LAYER ATTM.

.CURRENTLY...SKIES ARE MOSTLY SUNNY ACROSS THE ISLANDS AND
SURROUNDING WATERS...EXCEPT KEY WEST RADAR IS DETECTING NEW ISOLATED
SHOWERS MOVING WEST SOUTHWESTWARD TOWARDS THE UPPER KEYS ATTM.
MIDDLE LEVEL DRY AIR HAS THWARTED DEVELOPMENT ON THE SOUTH FLORIDA
MAINLAND. TEMPERATURES ARE IN THE LOWER 80S WITH DEWPOINTS IN THE
LOWER TO MID 60S ACROSS THE ISLANDS. C-MAN STATIONS ARE REGISTERING
WINDY CONDITIONS...FROM THE EAST BETWEEN 20 AND 25 KNOTS AND
GUSTY...WITH ISLAND SENSORS NEAR 20 MPH AND GUSTY.


.SHORT TERM...LARGE SCALE MODELS...TONIGHT THRU TUESDAY WEDNESDAY
NIGHT. ALTHOUGH MODELS CONSISTENT WITH INDICATIONS IN A RETURN TO A
WETTER PATTERN AGAIN TONIGHT THROUGH THE MIDDLE OF THIS WEAK...THEY
HAVE BEEN STRUGGLING WITH THE EXACT TIMING OF THE BOUNDARY LAYER
MOISTENING GIVEN THE AFFECTS OF THE STRONG LOWER LEVEL
CONVERGENCE...BUT ATTM THE MIDDLE LEVEL TROUGH IS DEVELOPING ACROSS
THE EASTERN GULF. SO WINDY CONDITIONS WILL CONTINUE ACROSS THE
ISLANDS THROUGH AT LEAST MONDAY NIGHT...WITH WINDS LETTING DOWN
AFTER MIDNIGHT AS THE SURFACE RIDGING OVER THE WESTERN ATLANTIC
MOVES FARTHER TO THE EAST. A WEAK RIDGE MORE TYPICAL OF MAY SETTLES
JUST NORTH OF THE ISLANDS TUESDAY THROUGH THE REST OF THE WEEK.

GIVEN THE TRENDS JUST MENTIONED AND THE FORECAST SOUNDINGS...AM
INTRODUCING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS VERY LATE
TONIGHT AND FOR MONDAY...BUT THE INSTABILITY INCREASES MORESO MONDAY
NIGHT AND TUESDAY & MODELS ARE RATHER WET. SO WILL CARRY LIKELY POPS
FOR BOTH MONDAY NIGHT AND TUESDAY. ALTHOUGH THE LOWER LEVEL SPEED
CONVERGENCE DISAPPEARS ON TUESDAY...THE SYNOPTIC SCALE LIFT DUE TO
THE 500 MB TROUGH AND STRONG SURFACE HEATING...DEEPER MOISTURE IN
THE LOWER TO MID TROPOSPHERE...PAIRED WITH IDEAL WIND DIRECTION AND
SPEEDS...ALL SUPPORT EXCELLENT CONDITIONS FOR MESOSCALE
CONVECTION...WITH CUMULUS/TOWERING CUMULUS LINES AND SOUTH FLORIDA
CONVECTION MOVING SOUTHWESTWARDS AND COLLIDING WITH KEYS BOUNDARIES.
MAY NEED TO RAISE POPS FOR TUESDAY EVENING BUT WILL CARRY HIGH
CHANCE POPS FOR NOW FOR TUESDAY EVENING. ON WEDNESDAY AND WEDNESDAY
NIGHT...LOOKS STILL WETTER IN THE BOUNDARY LAYER BASED ON THE
FORECAST SOUNDINGS AND THE PROFILE SUPPORTS ABOVE NORMAL CHANCES
GIVEN IDEAL LIGHT TO GENTLE NORTHEAST WINDS.

FOR THURSDAY THROUGH SUNDAY...WEAK RIDGING CONTINUES NORTH OF THE
KEYS AND DESPITE SLIGHTLY LESS MOISTURE IN THE BOUNDARY LAYER...WITH
PWAT AROUND 1.50 INCHES...WILL KEEP RAIN CHANCES AT 30% WHICH IS
SLIGHTLY ABOVE CLIMATE...BUT THEN HAVE RETURNED POPS TO ISOLATED
SHOWERS FOR THE WEEKEND SATURDAY THRU SUNDAY AS ITS FAR OUT AT THIS
POINT.

&&

UNTIL 12Z/4TH...THE BEST CHANCE FOR A MVFR ENCOUNTER WILL BE EARLY
MONDAY MORNING...OTHERWISE...VFR CONDITIONS ARE ANTICIPATED AT THE
KEY WEST AND MARATHON TERMINALS. DESPITE TYPICAL SHORT SPELL WIND
SURGES AND LULLS...MOSTLY EAST WINDS OF BETWEEN 13 AND 18 KNOTS WITH
GUSTS OF 24 AND 28 KNOTS CAN BE EXPECTED AT THE ISLAND AIRPORTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  74  83  72  83 / 30 50 60 70
MARATHON  74  84  73  83 / 30 50 60 70

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 6 PM EDT MONDAY FOR GMZ031>035-
     042>044-052>055-072>075.

&&

$$

PUBLIC/MARINE.........FUTTERMAN
AVIATION/NOWCASTS.....APA
DATA COLLECTION.......VICKERY

VISIT US ON THE WEB AT WEATHER.GOV/KEY

FOLLOW US ON FACEBOOK AND TWITTER AT...

WWW.FACEBOOK.COM/NWSKEYWEST
WWW.TWITTER.COM/NWSKEYWEST



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.