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 250845
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
445 AM EDT MON MAY 25 2015

.DISCUSSION...
AN UPPER-LEVEL COMPOSITE ANALYSIS THIS MORNING SHOWS A DEEP LAYER
MEAN ANTICYCLONE CENTERED OVER THE WESTERN NORTH ATLANTIC OCEAN JUST
EAST OF THE FLORIDA PENINSULA. THIS SYSTEM IS EXPANSIVE...WITH
RIDGING EXTENDING FROM NEW ENGLAND TO THE CARIBBEAN...AND FROM THE
CENTRAL ATLANTIC TO THE CENTRAL GULF OF MEXICO. AN ASSOCIATED BROAD
SURFACE HIGH PRESSURE CELL IS CENTERED NEAR BERMUDA WITH A RIDGE
EXTENDING WESTWARD TO THE LOWER MISSISSIPPI RIVER VALLEY. THE FLORIDA
KEYS LIE WITHIN A TRADE-WIND FLOW REGIME ALONG THE SOUTHERN FLANK OF
THE SURFACE HIGH. THE RESIDENT AIR MASS IS MARITIME TROPICAL...WITH
WEAK TO MODERATE CONDITIONAL INSTABILITY AND WEAK CONVECTIVE
INHIBITION. DATA FROM BOTH THE KEY WEST SUNDAY EVENING RADIOSONDE
BALLOON AND SUBSEQUENT SATELLITE-DERIVED SOUNDINGS INDICATE A VERY
MOIST SUBCLOUD LAYER...WITH CONSIDERABLE DRY AIR ALOFT. HOWEVER...
WEAK CONVECTIVE INHIBITION...AND A BOUNDARY-RICH CONFLUENT NOCTURNAL
LOW-LEVEL FLOW HAVE LED TO A PROLIFERATION OF SMALL SHOWERS WITH
ISOLATED THUNDERSTORMS EARLY THIS MORNING...MOVING QUICKLY WEST-
NORTHWESTWARD...AND AFFECTING SOME ISLAND COMMUNITIES. CURRENTLY...
AIR TEMPERATURES ARE NEAR 80F AT MOST ISLAND STATIONS...WITH
DEWPOINTS HOLDING STEADY IN THE MID 70S. EAST WINDS ARE BLOWING NEAR
15 MPH WITH GUSTS NEAR 20 MPH OVER LAND.

FORECASTS -- A SWATH OF RICHER MOISTURE OVER THE BAHAMAS...EVIDENCED
IN MIMIC-TPW IMAGERY FROM THE UNIVERSITY OF WISCONSIN CIMSS GROUP IN
PARTICULAR...IS TRANSITING WESTWARD AND WE HAVE THE BULK OF THIS
RICHER MOISTURE ARRIVING IN THE SERVICE AREA TONIGHT...COINCIDENT
WITH A WIND SURGE AND FAVORED NOCTURNALLY ENHANCED CONFLUENT FLOW
REGIME. THEREFORE...WE HAVE FLIP-FLOPPED THE 30/20 RAIN CHANCES
PREVIOUSLY INDICATED FOR TODAY AND TONIGHT...RESPECTIVELY.
THEREAFTER...TRENDS IN UPSTREAM SATELLITE OBSERVATIONS AND NUMERICAL
WEATHER PREDICTION OUTPUT INDICATE SIGNIFICANT DRYING ALOFT WITH SOME
STABILIZATION AS WELL AS THE DEEP LAYER MEAN ANTICYCLONE TRANSPORTS
AIR OF CONTINENTAL ORIGIN SOUTHWESTWARD INTO THE KEYS. THEREFORE...
WE HAVE ADJUSTED RAIN CHANCES DOWNWARD DURING THE TUESDAY-WEDNESDAY
TIME FRAME...AND REMOVED THUNDER. THEREAFTER...LARGE-SCALE SUBSIDENCE
MAY SLOWLY WEAKEN...WITH CLIMATOLOGICAL WEATHER REGIME EXPECTED.
&&

.MARINE...
SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR THE STRAITS OF FLORIDA
TODAY...AND LIKELY BE EXPANDED TO INCLUDE ALL ZONES BY TONIGHT. AN
EXPANSIVE HIGH PRESSURE SYSTEM WILL PERSIST OVER MUCH OF THE WESTERN
NORTH ATLANTIC...TO THE SOUTHEASTERN UNITED STATES FOR MUCH OF THE
UPCOMING WEEK. THIS SETUP WILL MAINTAIN FRESH EAST BREEZES ACROSS
FLORIDA KEYS COASTAL WATERS TODAY THROUGH FRIDAY.
&&

.AVIATION...
VFR WILL PREVAIL AT THE EYW AND MTH TERMINALS TODAY. BRIEF MVFR
CIGS/VIS ARE POSSIBLE EARLY THIS MORNING AT BOTH TERMINALS DUE TO
QUICKLY MOVING RAIN SHOWERS. EASTERLY WIND GUSTS WILL FREQUENTLY
APPROACH 20 KNOTS. THESE EASTERLY REGIMES FAVOR NOCTURNAL INCREASES
IN SHOWER CHANCES. THUS...SHOWER CHANCES WILL DECREASE AFTER
SUNRISE...ONLY TO INCREASE TONIGHT AFTER 00Z.
&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  88  81  88  81 / 20 30 10 10
MARATHON  91  81  91  81 / 20 30 10 10
&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...SMALL CRAFT ADVISORY IN EFFECT FOR GMZ052-GMZ053-GMZ054-
     GMZ055-GMZ072-GMZ073-GMZ074-GMZ075.
&&

$$

PUBLIC/MARINE.........KASPER
AVIATION/NOWCASTS.....CLR
DATA COLLECTION.......CLR

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.