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000
FXUS61 KLWX 121437
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1037 AM EDT SUN MAY 12 2013

.SYNOPSIS...
HIGH PRESSURE WILL BUILD TOWARD THE REGION TODAY THROUGH
TUESDAY...BRINGING DRY AND CHILLY CONDITIONS. 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.

&&

.NEAR TERM /THROUGH TONIGHT/...

LOW PRES OVR ONTARIO AND HIGH PRES BLDG IN FM THE MS VLLY IS
CAUSING COOL CYCLONIC FLOW IN THE MID ATLC. INSTABILITY CU WL
CONT TO FORM THRU LATE AFTN AND THEN SKIES WL GO CLR.

HIGH PRESSURE WILL BUILD E TONIGHT. NORTHWEST WINDS AHEAD OF THE
SURFACE HIGH WILL CAUSE UNUSUALLY CHILLY CONDITIONS FOR THIS TIME
OF YEAR. FROST/FREEZE IS 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. 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.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
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.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
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.

&&

.MARINE...
GUSTY NORTHWEST WINDS 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.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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.

&&

$$
UPDATE...WOODY!
PRVS...BJL/HTS