Area Forecast Discussion
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FXUS62 KKEY 171844
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
245 PM EDT THU APR 17 2014

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST IR
IMAGERY OVERLAID WITH MODEL STREAMLINE ANALYSIS AS OF 200 PM THIS
AFTERNOON...DEPICT THE AXIS OF A NARROW YET SHARP UNSEASONABLY DEEP
FULL LATITUDINAL TROUGH POSITIONED FROM MINNESOTA FROM TO CENTRAL
TEXAS. AN ENERGETIC SOUTHERN BRANCH OF THE JET STREAM ROUNDS THIS
FEATURE FROM ACROSS OLD MEXICO TO ACROSS THE GULF HEADING TOWARDS
FLORIDA...WITH A LARGE MCS (MESOSCALE CONVECTIVE SYSTEM) ON THE
RIGHT ENTRANCE REGION NOW OVER THE NORTHWESTERN GULF OF MEXICO. WELL
TO THE NORTHEAST OF THAT...A 1040 MB PLUS COLD SURFACE HIGH IS
PARKED OVER NORTHERN MAINE...BUT A SURFACE FRONTAL BOUNDARY BISECTS
CENTRAL FLORIDA...MUCH CLOSER TO THE KEYS.

.CURRENTLY...AS OF 200 PM...SKIES HAVE BECOME MOSTLY SUNNY WITH ONLY
A FEW SHOWERS ACROSS THE FLORIDA STRAITS...AND ONLY ONE OR TWO HAVE
MOVED ACROSS THE KEYS SO FAR AFTER THE NOON HOUR. THE MESOSCALE HAS
BEEN THWARTED SOMEWHAT THIS AFTERNOON AS WINDS HAVE BECOME MODERATE
AND THIS IS INDICATIVE OF THE LARGE SCALE MSLP GRADIENT...GIVEN THE
AFOREMENTIONED EXCEPTIONALLY STRONG HIGH OVER NORTHERN NEW ENGLAND.
C-MAN STATIONS. TEMPERATURES OVER THE ISLANDS ARE IN THE MIDDLE 80S
WITH DEWPOINTS ON THE LOWER 70S. C-MAN STATIONS ALONG THE REEF ARE
EASTERLY BETWEEN 10 AND 15 KNOTS...BUT GUSTY.

.SHORT TERM FORECASTS...TONIGHT THROUGH SATURDAY...ALL MODELS BRING
THE SHARP TROUGH AND ASSOCIATED CONVECTION ACROSS THE NORTHERN GULF
TONIGHT THROUGH THE PERIOD...WITH MODELS GENERALLY AGREEING THAT A
SURFACE LOW WILL BE ACCOMPANIED BY THE FORMATION OF A MIDDLE LEVEL
CYCLONE WHEN THIS SYSTEM REACHES THE EAST CENTRAL OR NORTHEASTERN
GULF OF MEXICO. BUT EXACT IMPLICATIONS OF THIS SCENARIO TEND TO BE A
LESS PREDICTABLE SCENARIO AND THUS CONFIDENCE IS UNUSUALLY LOW WITH
THESE EVENTS.

AS OF THIS AFTERNOON...THUNDERSTORMS HAVE DEVELOPED ALONG THE
SEABREEZE BOUNDARY OVER EXTREME SOUTH FLORIDA...AND I WOULD NOT BE
SURPRISED IF OUTFLOW MOVED ACROSS THE FLORIDA BAY AND BOTH NEARSHORE
AND OFFSHORE GULF WATERS THIS EVENING. THEREAFTER...MID AND UPPER
LEVEL HEIGHT FALLS AND ASSOCIATED WEAK LARGE SCALE LIFT WILL ALLOW
FOR ANY LEFTOVER SCATTERED BOUNDARIES FROM THIS EVENING THAT MANAGE
TO COLLIDE OVERNIGHT TO BECOME REINVIGORATED AS SHORT LIVED ISOLATED
SHOWERS AND THUNDERSTORMS. THEN DURING FRIDAY AND FRIDAY NIGHT...ALL
MODELS DEVELOP LOW PRESSURE AND MOVE IT NORTHEASTWARD FROM THE GULF
FRIDAY NIGHT...TO ACROSS NORTHERN FLORIDA ON SATURDAY...EXITING BY
SATURDAY AFTERNOON. AMPLE MOISTURE IN THE LOWER TO MIDDLE LEVELS
WILL FLOW INTO THE DEVELOPING SYSTEM...AND MODEL FORECAST SOUNDINGS
INDICATE THAT STORM MOTION IS MARGINALLY FAVORABLE FOR ANY CUBAN
CONVECTION TO WORK ITS WAY NORTHWARD DURING FRIDAY AND FRIDAY NIGHT.
GIVEN THESE UNCERTAINTIES...WILL ONLY INDICATE A LOW TO MID CHANCE
FOR SHOWERS AND THUNDERSTORMS ACROSS THE ISLANDS FRIDAY AND FRIDAY
NIGHT. BY SATURDAY MORNING...VERY DRY AIR IN THE MIDDLE LEVELS WILL
FILTER AROUND THE DEPARTING CYCLONE...WHICH WILL NOT ALLOW FOR ANY
SHOWERS...DESPITE INSTABILITY...SO HAVE REMOVED POPS FROM SATURDAY
AFTERNOON.

.THEN FOR SATURDAY AFTERNOON THRU SUNDAY NIGHT...VERY DRY AIR IN THE
MID LEVELS WILL COME IN SATURDAY AFTERNOON THROUGH SUNDAY
NIGHT...THOUGH STRONG SUN AND BREEZY CONDITIONS ARE EXPECTED...WINDS
WILL CLOCK FROM NORTHWEST TO NORTHEAST BY SUNDAY NIGHT...WITH MOSTLY
CLEAR SKIES AND LOWER HUMIDITY. TOTAL COLUMNAR MOISTURE WILL BE
BETWEEN ONE HALF AND ONE INCH...WITH NIL RAIN CHANCES.

EXTENDED...MONDAY THROUGH THURSDAY...MID AND UPPER PATTERN WILL BE
MOSTLY ZONAL/WEAKLY CYCLONIC. MUCH WEAKER SURFACE RIDGING WILL BUILD
IN OVER FLORIDA BEHIND THE BREEZY/NEAR BREEZY CONDITIONS FROM THE
WEEKEND. HAVE MAINTAINED DIME POPS THROUGH THE WEEK...ALTHOUGH
BOUNDARY LAYER MOISTURE IS ONLY EXPECTED TO ONLY INCREASE TO BETWEEN
1.00 AND 1.25 INCHES...GIVEN A VERY LIGHT NORTHERLY TO EASTERLY
PROFILE UNDER STRONG INSOLATION.

&&

.MARINE...SMALL CRAFT WILL NEED TO EXERCISE CAUTION AS WINDS
INCREASE TO BETWEEN 15 AND 20 KNOTS ACROSS ALL WATERS ONCE AGAIN
THIS EVENING AND EARLY FRIDAY MORNING...BEFORE WINDS AND SEAS LET
DOWN APPRECIABLY AS THEY CLOCK AROUND FRIDAY THROUGH SATURDAY
MORNING. SMALL CRAFT ADVISORIES ARE NOT PRESENTLY ADVERTISED ACROSS
HAWK CHANNEL AND THE FLORIDA STRAITS BUT ARE POSSIBLE THROUGH
TOMORROW MORNING.WINDS AND SEAS WILL LIKELY BE HIGHER IN AND NEAR
ANY SHOWERS AND THUNDERSTORMS...ESPECIALLY WITHIN CUBAN OUTFLOW
BOUNDARIES THAT ARE POSSIBLE FRIDAY AND FRIDAY NIGHT.
WINDS AND SEAS WILL INCREASE ONCE AGAIN BEHIND THE DEPARTING LOW
PRESSURE SATURDAY AND SATURDAY NIGHT...WITH CAUTIONS LIKELY ON ALL
WATERS SATURDAY NIGHT AND SUNDAY...AND THE POSSIBILITY OF SMALL
CRAFT ADVISORY CONDITIONS AGAIN THROUGH THIS TIME. WINDS AND SEAS
SHOULD LET DOWN EARLY NEXT WEEK.

&&

.AVIATION...
VFR CONDITIONS WILL CONTINUE AT BOTH THE KEY WEST INTERNATIONAL AND
MARATHON ISLAND TERMINALS THROUGH 03Z. EXPECT OUTFLOW FROM MAINLAND
SEA BREEZE TO CROSS THE GULF SIDE WATERS...PRODUCING SIMILAR RESULTS
TO LAST EVENINGS THUNDERSTORM ACTIVITY. SURFACE WINDS WILL BE EAST
TO SOUTHEAST NEAR 10 KNOTS...BECOMING GUSTY IN AND AROUND
THUNDERSTORMS.

&&

.CLIMATE...
ON THIS DATE IN KEYS WEATHER HISTORY...THE RECORD MINIMUM
TEMPERATURE IN KEY WEST WAS IS 62 DEGREES ON APRIL 17TH. THIS
OCCURRED TWICE...ONCE IN 1873 AND THE LATEST IN 1987. TEMPERATURE
RECORDS FOR KEY WEST DATE BACK TO 1872.

&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  76  84  75  82  72 / 30  30  40  20  -
MARATHON  76  87  75  84  72 / 30  30  40  20  -

&&

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

&&

$$

PUBLIC/MARINE/GRIDS....DAF
AVIATION/NOWCASTS......FJ/BWC
DATA COLLECTION........CLR

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