Area Forecast Discussion
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000
FXUS62 KKEY 010854
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
454 AM EDT MON SEP 1 2014

.DISCUSSION...
OBSERVATIONS/TRENDS -- AN APPRAISAL OF DOPPLER RADAR BASE
REFLECTIVITY TRENDS INDICATES A GRADUAL INCREASE IN CONVECTION CELL
COVERAGE ACROSS THE FLORIDA KEYS AND ADJOINING COASTAL WATERS SINCE
ABOUT MIDNIGHT. MOST CELLS HAVE ATTAINED ONLY MODEST DEPTH/INTENSITY
WITH FEW LIGHTNING STRIKES DETECTED. MOTION VECTORS HAVE AVERAGED
ABOUT 100/16KT. THE CURRENT LARGE-SCALE ATMOSPHERIC REGIME IS
DOMINATED BY A DEEP SUBTROPICAL RIDGE EXTENDING FROM THE CENTRAL
NORTH ATLANTIC TO THE SOUTHEASTERN UNITED STATES. A DEEP AND
CONDITIONALLY UNSTABLE EASTERLY CURRENT PREVAILS ALOFT OVER THE
SERVICE AREA...WITH RICH MOISTURE IN THE BOUNDARY LAYER. MEAN LOW- TO
MID-TROPOSPHERIC MOISTURE...POTENTIAL BUOYANCY VALUES...AND
CONVECTIVE INHIBITION ENERGY HAVE BEEN FLUCTUATING OVER THE LAST FEW
DAYS...WITH VARIATIONS PRIMARILY DUE TO EVOLVING MOMENTUM AND
MOISTURE CONVERGENCE IN THE BOUNDARY LAYER.

CUMULUS SKIES HAVE BEEN PREVALENT DURING THE LAST FEW DAYS...AND IT
IS NO DIFFERENT EARLY THIS MORNING. CURRENTLY...MOST KEYS ISLAND
COMMUNITIES ARE REPORTING AIR TEMPERATURES AROUND 84-85F...WITH
DEWPOINT TEMPERATURES AGAIN IN THE MID 70S...YIELDING 400 AM HEAT
INDICES IN THE LOWER 90S. EAST WINDS HAVE DROPPED A FEW MILES PER
HOUR DURING THE LAST 24 HOURS...AS AN EVOLVING TROPICAL WAVE MOVED
WESTWARD OVER THE YUCATAN PENINSULA.

FORECASTS -- THE LARGE-SCALE ANALYSIS AND EXPECTED PATTERN EVOLUTION
OFFER NO SIGNIFICANT DEVIATIONS FROM PROGNOSTIC REASONING OF THE LAST
SEVERAL FORECAST CYCLES. IT SEEMS APPARENT THAT AT LEAST SCATTERED
COVERAGE OF SHOWERS/STORMS IS A GOOD BET FOR THE NEXT SEVERAL
PERIODS...AND 12-HOUR MEASURABLE RAIN CHANCES ARE APPROACHING THEIR
YEARLY CLIMATOLOGICAL PEAK OF AROUND 35 PERCENT. A WEAK...WESTWARD-
MOVING UPPER-TROPOSPHERIC COLD-CORE CYCLONE...CURRENTLY EVIDENT IN
GEOSTATIONARY SATELLITE MOISTURE CHANNEL ANIMATIONS JUST EAST OF THE
BAHAMAS...WILL MAINTAIN INTENSITY DURING THE NEXT 24-36 HOURS BEFORE
WEAKENING AND ELONGATING RAPIDLY AS IT APPROACHES SOUTHERN FLORIDA
TUESDAY NIGHT OR WEDNESDAY. ITS WEAK AND SHALLOW NATURE SUGGEST THAT
ITS INFLUENCE ON SENSIBLE WEATHER MAY BE SOMEWHAT FLEETING AND
UNCERTAIN LOCALLY. FOR NOW...WE ARE STAYING THE COURSE WITH A SLIGHT
INCREASE IN PRECIPITATION/THUNDER PROBABILITIES BEGINNING WEDNESDAY.
MOREOVER...WE MAINTAIN THE ELEVATED RAIN CHANCES THROUGH THE FORECAST
HORIZON.
&&

.MARINE...
SMALL CRAFT ADVISORIES WERE DISCONTINUED SUNDAY EVENING. HOWEVER...
SMALL CRAFT CAUTION HEADLINES REMAIN APPENDED TO ZONES COVERING THE
LOWER STRAITS OF FLORIDA AND EXTREME SOUTHEASTERN GULF OF MEXICO
INCLUDING DRY TORTUGAS/REBECCA SHOAL CHANNEL. EAST BREEZES SHOULD
SLACKEN A LITTLE FURTHER TONIGHT BEFORE SETTLING INTO THE BEAUFORT
FORCE 4 RANGE FOR A FEW DAYS...11-16 KNOTS. WINDS AND SEAS WILL OF
COURSE BE HIGHER AND MORE VARIABLE IN AND NEAR SCATTERED SHOWERS AND
THUNDERSTORMS.
&&

.AVIATION...
THERE WILL BE A CHANCE FOR SHORT LIVED MVFR/IFR CONDITIONS AT THE
EITHER ISLAND TERMINAL DUE CONTINUED ROBUST EAST SOUTHEAST LOW LEVEL
FLOW. THE REASON FOR THE MODERATE WINDS IS A COMBINATION OF AN UPPER
LEVEL TROUGH EAST OF THE BAHAMAS...AND ONE MOVING THROUGH THE MID
WEST...WILL TIGHTEN THE GRADIENT AROUND THE SUBTROPICAL RIDGE
PRODUCING 15 TO 20 KNOTS. THERE IS ENOUGH INSTABILITY NEARBY TO
IMPLY THAT ANY BOUNDARY COLLISIONS MAY BE ALL THAT IS NEEDED FOR
THUNDERSTORMS. 15 TO 20 KNOTS.
&&

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

$$

PUBLIC/MARINE.........KASPER
AVIATION/NOWCASTS.....BWC

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