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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 120752
AFDLWX

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

.SYNOPSIS...
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HIGH PRESSURE WILL BUILD TOWARD THE REGION TODAY THROUGH
TUESDAY...BRINGING DRY AND CHILLY CONDITIONS FOR THIS TIME OF YEAR.
HIGH PRESSURE WILL MOVE OFF THE COAST DURING THE MIDDLE AND LATTER
PORTION OF THE WEEK...ALLOWING FOR A RETURN OF WARM AND HUMID
CONDITIONS.
-- End Changed Discussion --
&&

.NEAR TERM /THROUGH TONIGHT/...
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CURRENT ANALYSIS SHOWS A COLD FRONT OVER LOWER SOUTHERN MARYLAND AND
THE VIRGINIA PIEDMONT EARLY THIS MORNING. UPPER-LEVEL LOW PRESSURE
IS TRACKING THROUGH THE GREAT LAKES WHILE CANADIAN HIGH PRESSURE
BUILDS OVER THE CENTRAL CONUS.

A FEW SHOWERS EARLY THIS MORNING ARE MOVING ACROSS THE VIRGINIA
PIEDMONT AND SOUTHERN MARYLAND NEAR THE COLD FRONT. THESE SHOWERS
ARE EXPECTED TO MOVE OFF TO OUR EAST ALONG WITH THE COLD FRONT BY
SUNRISE. A NORTHWEST FLOW BETWEEN THE DEPARTING COLD FRONT AND
SURFACE HIGH PRESSURE OVER THE CENTRAL CONUS WILL ALLOW FOR DRIER
AND NOTICEABLY COOLER CONDITIONS. BREEZY CONDITIONS ARE ALSO
EXPECTED DUE TO A DEEP MIXING LAYER FROM THE COLD ADVECTION.
NORTHWEST WINDS WILL GUST FREQUENTLY BETWEEN 20 TO 30 MPH. THE DRIER
AIR WILL ALLOW FOR PLENTY OF SUNSHINE...BUT MAX TEMPS WILL STILL BE
ABOUT 5 TO 10 DEGREES BELOW CLIMO...RANGING FROM THE 40S IN THE
MOUNTAINS TO THE MID AND UPPER 60S NEAR WASHINGTON AND BALTIMORE.
DID LEAN THE TEMP FORECAST CLOSER TO THE MAV GUIDANCE...WHICH
IS A BIT WARMER THAN OTHER GUIDANCE. THE MAV HAS PERFORMED BETTER
OVER THE LAST COUPLE DAYS AND A DOWNSLOPING FLOW ALONG WITH PLENTY
OF SUNSHINE FURTHER ENHANCES THE THOUGHT BEHIND LEANING TOWARD THE
MAV.

CANADIAN HIGH PRESSURE OVER THE CENTRAL CONUS WILL BUILD EAST TOWARD
OUR AREA TONIGHT WHILE AN UPPER-LEVEL TROUGH AXIS BUILDS OVERHEAD IN
RESPONSE TO THE UPPER-LEVEL LOW TRACKING THROUGH EASTERN CANADA.
NORTHWEST WINDS AHEAD OF THE SURFACE HIGH WILL CAUSE UNUSUALLY
CHILLY CONDITIONS FOR THIS TIME OF YEAR. FROST/FREEZE HEADLINES ARE
A CONCERN FOR LOCATIONS ALONG THE MASON-DIXON LINE AND ALONG/WEST OF
THE BLUE RIDGE MOUNTAINS. A FREEZE WATCH IS IN EFFECT FOR THE
ALLEGHENY AND POTOMAC HIGHLANDS. MIN TEMPS MAY DROP INTO THE 20S
ACROSS THESE AREAS. FOR OTHER LOCATIONS NEAR THE MASON-DIXON LINE
AND ALONG/WEST OF THE BLUE RIDGE MOUNTAINS...MIN TEMPS WILL BE IN
THE LOWER TO MIDDLE 30S. HOWEVER...ADVISORIES/WARNINGS HAVE NOT BEEN
ISSUED WITH THIS SHIFT DUE TO UNCERTAINTY WITH THE GRADIENT WIND.
WINDS MAY BE JUST STRONG ENOUGH TO PREVENT WIDESPREAD FROST...
DESPITE THE CHILLY CONDITIONS. ACROSS THE METRO AREAS...MIN TEMPS
WILL RANGE FROM THE MID AND UPPER 30S IN THE NORTHERN AND WESTERN
SUBURBS OF WASHINGTON/BALTIMORE TO THE MIDDLE 40S IN DOWNTOWN
WASHINGTON/BALTIMORE.
-- End Changed Discussion --
&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
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AN AMPLIFIED H5 TROF AXIS PIVOTS ACRS CWFA MON. MDL SNDGS SUGGEST
ATM WL BE MIXED UP TO ABT H7...W/ STEEP LAPSE RATES BLO THAT LVL...
AND NEARLY SATD AT THE LCL. FCST WL FEATURE CLDS INVOF TROF /AN EWD
XTNSN OF STCU IN APLCHNS AT DAYBREAK/...AND 15-20 KT WND GUSTS. FULL
MIXING WUD YIELD 25 KT ACRS THE N...BUT AM CONCERNED THAT THE CLDS
WL IMPEDE THAT OCCURENCE. AM ALSO GOING ON THE COOLER SIDE OF MOS...
WHICH IS CLIMATOLOGICALLY COOL ALREADY. CHO-DCA-BWI SHUD SEE MAXT OF
60F...BUT MID-UPR 50S WEST OF THERE AND SOME 40S IN THE APLCHNS.

UPR TROF ADVANCES TO ATLC CST MON NGT AS SFC HIPRES BLDS. WL HV A
SETUP THAT SUPPORTS CLR SKIES AND DCPLG WNDS...FVRBL CONDS FOR RADL
COOLING. THAT PUTS WRN CWFA AT A GREATER RISK FOR FROST/FREEZE. USED
BIAS COR MAV AS A STARTING PT FOR MIN-T...BUT DID ADJUST CLIMO-FVRD
AREAS DOWN FM THERE. SINCE IT/S THE LATE 4TH/ELY 5TH FCST PD...WL
KEEP MENTION OF HAZARD IN JUST HWO ATTM.

SFC HIPRES CONTS TO BLD ATOP CWFA TUE...FOR A QUIET AND MILDER DAY.
WL BE RECIPIENT OF H8-7 WAA IN THE AFTN...AND HV ADDED SOME CLDS TO
GRIDS IN RESPONSE TO THE MSTR INCREASE AT THAT LVL...SPCLY W OF
BLURDG.
-- End Changed Discussion --
&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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EURO AND GFS IN PRETTY GOOD AGREEMENT THROUGH THE UPCOMING WEEK. TUE
NIGHT INTO WED THE MID LEVEL WARM FRONT PASSES ENE THRU THE REGION.
SHOULD BE DRY BUT 850MB TEMPS RISE FROM THE SINGLE DIGITS TUE EVE TO
THE MIDDLE TEENS BY WED EVE. THAT IS QUICKLY FOLLOWED BY A SMALL
500MB TROF THAT DEVELOPS A WEAK LOW OVER THE REGION WITH A TRAILING
COLD FRONT LATE THU INTO FRI. A SMALL AREA OF SLIGHTLY COOLER HIGH
PRESSURE TRIES TO NOSE IN FROM THE MIDWEST FOR SAT.
-- End Changed Discussion --
&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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NORTHWEST WINDS WILL GUST AROUND 20 TO 25 KNOTS BEHIND A COLD FRONT
THROUGH THIS AFTERNOON. WINDS WILL DIMINISH TOWARD SUNSET. VFR
CONDITIONS ARE EXPECTED THROUGH TONIGHT.

OUTLOOK...
MON-WED...VFR. GUSTY NW WNDS MON AFTN IN THE METROS AND MRB.
WED NGT-THU...LCL RESTRICTIONS PSBL INVOF SHRA/TSRA.
-- End Changed Discussion --
&&

.MARINE...
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NORTHWEST WINDS ARE EXPECTED BEHIND A COLD FRONT THROUGH TONIGHT. A
SMALL CRAFT ADVISORY IS IN EFFECT TODAY FOR THE WATERS. THE SMALL
CRAFT ADVISORY CONTINUES THROUGH TONIGHT FOR THE MARYLAND CHESAPEAKE
BAY SOUTH OF SANDY POINT AND THE LOWER TIDAL POTOMAC RIVER SOUTH OF
COBB ISLAND.

LINGERING NLY CHANNELING IN THE MID BAY ELY MON MRNG. RATHER DP
MIXING PSBL MON AFTN...BUT WNDS W/IN THAT LYR OVER THE WATER NOT
QUITE OVERWHELMING. SEE STRONG POTL FOR 15 KT GUSTS. A FEW HIER
GUSTS W/IN REALM OF PSBLTY...BUT HV OPTED TO CAP AT 15 KT ATTM.

FLOW DIMINISHES MON NGT-TUE AS HIPRES BLDS. RTN FLOW WED-THU...SHUD
PRIMARILY BE 10 KT OR LESS.
-- End Changed Discussion --
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE.
MD...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR
     MDZ501.
VA...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR
     VAZ503-504.
WV...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR
     WVZ501-503-505-506.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530-
     531-535-536-538-539-542.
     SMALL CRAFT ADVISORY UNTIL 9 AM EDT MONDAY FOR ANZ532>534-537-
     540-541-543.
-- End Changed Discussion --

&&

$$
SYNOPSIS...LASORSA
NEAR TERM...LASORSA
SHORT TERM...HTS
LONG TERM...STRONG
AVIATION...LASORSA/HTS
MARINE...LASORSA/HTS