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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 122131
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
531 PM EDT SUN MAY 12 2013

.SYNOPSIS...
-- Changed Discussion --
SURFACE HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH
TUESDAY...WITH AN UPPER LEVEL TROUGH CROSSING THE MID-ATLANTIC ON
MONDAY. SURFACE HIGH PRESSURE WILL MOVE OFF THE COAST TUESDAY
NIGHT AND PERSIST OFF THE SOUTHEASTERN COAST INTO FRIDAY.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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HIGH PRES MOVG INTO THE RGN. SKIES SHOULD BE GNRLY CLR OVRNGT.
WINDS WILL MIX IN MOST PLACES WELL INTO THE OVERNIGHT. FIRST
THOUGHT WAS TO TAKE A FROST ADVISORY TO THE NRN/WRN BALT- WASH
SUBURBS...BUT WITH MIXING TEMPS SHOULD STAY UPR 30S OR HIGHER.
WENT WITH A FROST ADVISORY FOR WEST OF THE BLUE RIDGE. FREEZE
WARNING FOR THE HIGHLANDS...THOUGH CLOUDS WILL PERSIST WELL INTO
TONIGHT.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
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SIGNIFICANT SHIFT IN FORECAST FOR MONDAY AS UPR TROUGH WILL PRODUCE
STRATOCU CLOUDS SIMILAR TO WHAT IS OVER THE OHIO VALLEY THIS
AFTERNOON. THEREFORE RAISED MOST OF THE CWA TO AROUND 70 PERCENT
SKY COVER (MOSTLY CLOUDY) BY THE AFTERNOON. CUT DOWN ON
TEMPERATURES AND WINDS WITH LESS INSOLATION...MOST AREAS WILL
STRUGGLE TO TOP 60F TOMORROW. ADDED SOME ISOL SHRA FOR SRN HALF OF
THE CWA WHERE THE VORT MAX IS PROGGED TO GO THROUGH. ADDED
SPRINKLES FOR NRN MD WHERE LESS DOWNSLOPING OCCURS IN NWLY FLOW.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
UPPER TROUGH AXIS WILL PASS THRU MON EVE BEFORE THE TROUGH MOVES OFF
THE ERN SEABOARD LATE MON NGT AND TUE. GOOD RADIATIONAL COOLING
SETUP FOR MON NGT WITH THE SFC HIGH BUILDING OVERHEAD. AN UPPER JET
STREAK APPROACHING FROM THE NW MAY BE ACCOMPANIED BY CI OVNGT...BUT
IMPACTS ON TEMPS SHOULD BE MINIMAL. MIN TEMP FCST BASED OFF A BLEND
OF BIAS-CORRECTED MOS-MAV GUIDANCE...WHICH HAVE THE HIGHEST
VERIFICATION SCORES FOR MIN TEMPS IN RECENT. ISSUED A FREEZE WATCH
FOR ALL COUNTIES WEST OF THE BLUE RIDGE. BASED ON CURRENT FCST...
FROST ADVISORIES MAY BE NEEDED FARTHER EAST TO ABOUT I-95.

UPPER RIDGE AND SFC HIPRES OVERHEAD TUE EVENTUALLY MOVES OFF THE
SOUTHEAST COAST TUE NGT AND WED. A WARM FRONT WILL MOVE THRU DURING
THIS TIME. WINDS BACKING TO SLY NEAR THE SFC AND TO WLY ALOFT WILL
YIELD STRONG WAA /12Z GFS SHOWS H8 TEMPS AT IAD INCREASING FROM -2C
TUE MRNG TO 17C BY WED EVE/. DUE TO ISENTROPIC LIFT FOLLOWED BY A
RETURN OF MOISTURE...CLOUDS AND POSSIBLY LIGHT SHOWERS OR SPRINKLES
MAY ACCOMPANY THE WARM FRONTAL PASSAGE ON WED.

A WEAK SHORTWAVE TROUGH THAT IS FCST TO TRACK EWD INTO THE SRN
PLAINS ON WED MAY BREAK DOWN THE ERN CONUS RIDGE THU AND FRI AS IT
MOVES OVER THE MID-ATLANTIC REGION. CHANCES FOR SHOWERS AND TSTMS
INCREASE LATE IN THE WEEK WITH THE APPROACH OF THE TROUGH. ABOVE
NORMAL TEMPS WILL PERSIST THRU THE WEEKEND.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
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VFR CONDS TNGT AND MON. GUSTY NW WINDS UP TO 25 KT THRU SUNSET
THIS EVE...WITH PERHAPS 20 KT LATE MONDAY AFTERNOON UNDER AND UPR
TROUGH.

HIPRES IN CONTROL THRU MIDWEEK RESULTING IN VFR CONDITIONS. A WEAK
DISTURBANCE APPROACHES THU/FRI. GENERALLY VFR DURING THIS TIME
ALTHOUGH SHOWERS/STORMS MAY TEMPORARILY/LOCALLY RESTRICT CIGS/VSBYS.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
SOLID SCA LVL WINDS BEING XPRNCD ON THE WATERS INTO THE EVENING
BEFORE SLOWLY DROPPING BELOW SCA CRIT BY 4 AM. DELAYED SCA FOR
MONDAY DUE TO CLOUD COVER AND UPR TROUGH AXIS IN THE LATE
AFTERNOON/EVENING. WENT FOR NRN WATERS /NORTH OF NORTH BEACH AFTER
3PM...THEN EXPAND TO MAIN STEM...ERN TRIBS...LOWER TIDAL POTOMAC
FOR THE OVERNIGHT AS WIND VEERS NLY WITH CHANNELING.

WINDS DIMINISH MON NGT AS HIPRES BUILDS IN. WARM FRONT MOVES THRU
WED...WHICH MARKS THE ONSET OF SLY FLOW. GIVEN DEEP MIXING...GUSTS
TO 20 KT POSSIBLE DURING THE DAY WED.
-- End Changed Discussion --

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE.
MD...FREEZE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY MORNING
     FOR MDZ003-501-502.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT MONDAY FOR MDZ501.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR MDZ003-502.
VA...FREEZE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY MORNING
     FOR VAZ025>031-503-504.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT MONDAY FOR VAZ503-504.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR VAZ025>031.
WV...FREEZE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY MORNING
     FOR WVZ050>053-055-501>506.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT MONDAY FOR WVZ501-503-505-
     506.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR WVZ050>053-055-
     502-504.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT MONDAY FOR ANZ530>534-537-
     539>541-543.
     SMALL CRAFT ADVISORY FROM 3 PM MONDAY TO 6 AM EDT TUESDAY FOR
     ANZ532-540.
     SMALL CRAFT ADVISORY FROM 6 PM MONDAY TO 6 AM EDT TUESDAY FOR
     ANZ533-534-537-541-543.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ535-
     536-538-542.
     SMALL CRAFT ADVISORY FROM 3 PM MONDAY TO 2 AM EDT TUESDAY FOR
     ANZ530-531-539.
     SMALL CRAFT ADVISORY FROM 3 PM TO 6 PM EDT MONDAY FOR ANZ538.
-- End Changed Discussion --

&&

$$
UPDATE...JACKSON
PREVIOUS DISCUSSION...ABW/JRK