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000
FXUS62 KMFL 170609
AFDMFL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
209 AM EDT FRI MAY 17 2013

.AVIATION...
VFR CONDITIONS WILL DOMINATE INTO THE WEEKEND. OCSNL 3-6KFT
CIGS...ESPECIALLY DURING THE AFTERNOONS. THERE MAY BE ISOLATED
SHOWERS THIS AFTERNOON...BUT PROBABILITY IS TOO LOW TO WARRANT
MENTION IN TAFS ATTM. EAST WINDS EARLY THIS MORNING OF 5-10 KT
WILL INCREASE A BIT DURING THE DAY...THEN DIMINISH DIURNALLY THIS
EVENING.

&&

PREV DISCUSSION... /ISSUED 240 PM EDT THU MAY 16 2013/

DISCUSSION...
HIGH PRESSURE REMAINS IN CONTROL OF THE WEATHER...WITH DRY LOW AND
MID LEVEL AIR ACROSS THE REGION. DEWPOINTS REMAINED IN THE LOW 60S
ACROSS THE REGION...WHICH WAS MAKING FOR A VERY PLEASANT MIDDLE OF
MAY AFTERNOON FOR SOUTH FLORIDA.

A SHORTWAVE ACROSS THE MIDDLE OF THE COUNTRY WILL MOVE EAST AND
WEAKEN TONIGHT INTO FRIDAY. A STRONGER SHORTWAVE MOVING INTO THE
NORTHEAST WILL ALSO MOVE EAST. THIS WILL CAUSE HIGH PRESSURE OVER
THE WESTERN ATLANTIC TO WEAKEN AND SHIFT EAST AS WELL...WITH FLOW
VEERING TO THE SOUTHEAST. THIS WILL ALLOW FOR DEEPER LOW LEVEL
MOISTURE TO BEGIN MOVING NORTH FROM THE CARIBBEAN AND WESTERN
ATLANTIC. PWATS WILL INCREASE TO AROUND NORMAL (1.3-1.5 INCHES)
ACROSS THE REGION AND EVEN SLIGHTLY ABOVE NORMAL ACROSS DEEP SOUTH
FLORIDA. DEWPOINTS WILL INCREASE TO THE MID 60S TO AROUND 70 ACROSS
DEEP SOUTH FLORIDA. THERE WILL STILL BE A CAP IN THE LOW/MID
LEVELS...BUT RAIN CHANCES WILL SLOWLY BEGIN TO INCREASE.

A LARGE UPPER RIDGE WILL STRETCH FROM TEXAS THROUGH THE NORTHERN
PLAINS AND INTO CANADA ON SATURDAY...AND THE SHORTWAVE OVER THE
SOUTHEAST WILL GET BLOCKED AND BEGIN TO PUSH TO THE EAST AND
SOUTHEAST. A WEAK SHORTWAVE IS EXPECTED TO MOVE ACROSS SOUTH FLORIDA
IN THE WEST TO NORTHWESTERLY FLOW ALOFT AROUND THE RIDGE...AND
HEIGHTS WILL FALL ACROSS THE REGION. 500MB TEMPS ARE FORECAST TO
COOL TO AROUND -10C. WITH NEAR TO SLIGHTLY ABOVE NORMAL MOISTURE IN
PLACE...EXPECT SCATTERED SHOWERS AND THUNDERSTORMS TO DEVELOP ALONG
THE SEA BREEZE BOUNDARIES...ESPECIALLY ACROSS THE INTERIOR. STORM
MOTION WILL BE ALMOST ZERO AS FLOW AT THE SURFACE IS OUT OF THE
EAST...FLOW AT 850MB WILL BE LIGHT AND FLOW ABOVE THAT LEVEL WILL BE
OUT OF THE WEST TO NORTHWEST. SO HEAVY RAINFALL IS POSSIBLE WHERE
STORMS DEVELOP. SIMILAR CONDITIONS ARE EXPECTED ON SUNDAY...EXCEPT
STORMS ARE EXPECTED TO CONCENTRATE ACROSS THE INTERIOR AND TOWARDS
THE GULF COAST.

AN UPPER LEVEL LOW WILL TRY AND DIG INTO THE NORTHERN PLAINS ON
MONDAY...BUT ITS PROGRESS WILL GET BLOCKED BY THE RIDGE OVER THE
EAST COAST AND THE LOW OVER CANADA EAST OF HUDSON BAY. WEAK
TROUGHING WILL TAKE PLACE OVER SOUTH FLORIDA DUE TO THE SHORTWAVE
GETTING TRAPPED UNDER THE RIDGE. SO 500MB TEMPS WILL COOL BACK TO
-10 TO -11C FOR MONDAY AND TUESDAY...WITH SCATTERED SHOWERS AND
THUNDERSTORMS RETURNING TO THE REGION EACH DAY. THE UPPER
LOW/SHORTWAVE OVER THE NORTHERN PLAINS WILL FINALLY PUSH EAST ON
WEDNESDAY...AND THE RIDGE WILL FLATTEN AND PUSH SLIGHTLY EAST AS
WELL. SO THE FLOW IS EXPECTED TO SHIFT TO THE SOUTHEAST...AND DEEPER
TROPICAL MOISTURE WOULD THEN PUSH ACROSS SOUTH FLORIDA. THE MODELS
DIFFER SOMEWHAT ON THE STRENGTH OF THE TROUGH OF LOW PRESSURE
BRINGING THE DEEPER MOISTURE. THE GFS BRINGS DEEP MOISTURE ACROSS
THE REGION WEDNESDAY INTO NEXT WEEKEND...WITH PWATS INCREASING TO
1.7-1.9 INCHES. THERE WOULD BE A THREAT OF HEAVY RAIN EACH DAY IF
THIS OCCURS. THE ECMWF IS STRONGER AND SHARPER WITH A TROUGH OF LOW
PRESSURE OVER THE BAHAMAS. THIS COULD ACTUALLY KEEP THE DEEPER
MOISTURE OFFSHORE...WITH MORE TYPICAL AFTERNOON AND EARLY EVENING
SHOWERS AND STORMS ALONG THE SEA BREEZE BOUNDARIES. TEMPERATURES
WILL REMAIN CONSISTENT EACH DAY...WITH HIGHS IN THE MID TO UPPER 80S
EAST AND UPPER 80S TO LOWER 90S GULF COAST. LOWS ARE EXPECTED TO BE
IN THE LOW TO MID 70S FOR THE COASTAL AREAS AND 60S ACROSS THE
INTERIOR.

MARINE...
THE WINDS WILL BE EASTERLY AT 10 TO 15 KNOTS TONIGHT INTO FRIDAY
BEFORE DECREASING TO 10 KNOTS OR LESS THIS WEEKEND FROM THE
SOUTHEAST DIRECTION. THIS WILL KEEP THE ATLANTIC AND GULF WATER
SEAS AT 2 FEET OR LESS THROUGH THE WEEKEND. SO...BOATING
CONDITIONS SHOULD BE GOOD THROUGH THIS WEEKEND OUTSIDE OF ANY
SHOWERS THAT DO DEVELOP OVER SOUTH FLORIDA WATERS.

FIRE WEATHER...
THE RELATIVE HUMIDITY OVER SOUTH FLORIDA WILL REMAIN ABOVE THE 35
PERCENT CRITICAL VALUE THROUGH THE PERIOD. HOWEVER...THE INTERIOR
AND WEST COAST METRO AREAS COULD FALL DOWN INTO THE UPPER 30S
FRIDAY AFTERNOON.

&&

.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH  85  73  85  73 / 20 20 20 20
FORT LAUDERDALE  86  76  86  76 / 20 20 20 20
MIAMI            86  75  87  75 / 20 20 20 20
NAPLES           87  71  88  71 / 20 20 20 20

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...NONE.
GM...NONE.
&&

$$

DISCUSSION/MARINE/FIRE...54/BNB
AVIATION/RADAR...23/SK