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000
FXUS61 KLWX 131927
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
327 PM EDT MON MAY 13 2013

.SYNOPSIS...
AN UPPER TROUGH WILL MOVE EAST OF THE REGION TONIGHT WHILE SURFACE
HIGH PRESSURE BUILDS OVER THE REGION. THE HIGH WILL MOVE OFFSHORE
TUESDAY AFTERNOON THROUGH EARLY WEDNESDAY AS A WARM FRONT
ADVANCES NORTHEASTWARD INTO THE MID-ATLANTIC STATES. A COLD FRONT
WILL APPROACH THE REGION LATE WEDNESDAY...BUT STALL OUT THROUGH
THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH TUESDAY/...
SFC HIPRES JUST WEST OF THE APPALACHIANS WILL CONTINUE TO BUILD EWD
TOWARD THE ERN SEABOARD TNGT. LATEST WATER VAPOR SATELLITE LOOP
SHOWS AN UPPER LOW OVER QUEBEC WHILE A VORT MAX ROTATES TOWARD THE
BASE OF THE UPPER TROUGH AND ACROSS THE MID-ATLANTIC REGION THIS
AFTN AND EVE. DEEP MIXING IS OCCURRING DURING THE PEAK HEATING HRS
AS COLD POOL ALOFT ASSOCIATED WITH THE TROUGH MOVES IN. EVEN WITH
STEEP LOW- AND MID-LVL LAPSE RATES...MOISTURE IS SCARCE /SFC
DEWPOINTS IN THE 20S/ AND INSTABILITY IS WEAK. BASED ON LOCATION OF
BEST LIFT/MOISTURE...POPS ARE HIGHEST OVER THE MTS...CENTRAL VA AND
LWR SRN MD...BUT STILL ONLY 30 PERCENT. SPRINKLES POSSIBLE ELSEWHERE.
GIVEN INVERTED V SOUNDING...SHOWERS CAPABLE OF TRANSPORTING 30-35
MPH GUSTS DOWN TO THE SFC.

THE CENTER OF THE HIGH WILL SHIFT EWD TOWARD THE POTOMAC HIGHLANDS
OVNGT. THIS PATTERN FAVORS THE BEST RADIATIONAL COOLING CONDITIONS
TO OCCUR ACROSS THE WRN HALF OF THE CWA. THE FREEZE WATCH HAS BEEN
UPGRADED TO A WARNING WEST OF THE BLUE RIDGE AND A FROST ADVISORY
WAS ISSUED FOR THE COUNTIES ALONG THE BLUE RIDGE. FARTHER EAST
TOWARD I-95...WILL HOLD OFF ON A FROST ADVISORY SINCE THERE IS DOUBT
THAT WINDS DECOUPLE FULLY WITH RESIDUAL CAA AND THE HIGH STILL
BUILDING IN FROM THE WEST.

HIPRES MOVES OFFSHORE TUE AFTN...RESULTING IN A LGT RETURN FLOW
DEVELOPING OVER THE AREA. WAA LATE IN THE DAY WILL PROMOTE WARMER
TEMPS TDA THAN YDA...ALTHOUGH INCREASING CLOUD COVER WILL LIMIT THE
EXTENT OF WARMING A BIT. MAX TEMPS TUE GENERALLY IN THE 60S.

&&

.SHORT TERM /TUESDAY NIGHT/...
ONE LAST COOL OVERNIGHT PERIOD ON TUE NIGHT...MORE OF A
TRANSITION - U40S - FROM THE NEAR-FREEZING TEMPS AND THE
CONSIDERABLY DIFFERENT AND WARMER OVERNIGHT LOWS STARTING WED
NIGHT.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
A FAST-MOVING AND LOCALIZED UPPER VORT WILL ACCELERATE OUT OF THE
UPPER MIDWEST LATE TUE INTO WED...WHILE THE LARGER UPPER TROUGH IS A
BLOCKADE IN ITS EWD PROGRESS. THE INCOMING VORT WILL BE DISPERSED
EARLY WED...HAVING LITTLE EFFECT ON THE MID ATLC REGION BUT HELPING
TO OPEN A CLEARER PATH FOR THE NEXT SYSTEM TO PROGRESS AS IT MOVES
TOWARD THE NORTHEAST. FAST OF THE HEELS OF THE EARLY WED UPPER LEVEL
FEATURE WILL BE A POTENT BUT RELATIVELY SMALL SYSTEM THAT WILL SLIDE
ACROSS THE US/CANADIAN BORDER TUE/WED. FAST UPPER FLOW WILL TAKE THE
SRN STREAM PORTION OF THE SYSTEM OVER THE GREAT LAKES DURING THE
DAYTIME HRS...W/ THE REMNANT CONVECTION SLIDING ACROSS NY/PA AND THE
NRN TIER OF OUR CWA LATE WED/EARLY THU. A NEAR 10 DEG INCREASE IN
TEMPS IS EXPECTED ON WED AFTN FROM THE PAST COUPLE OF DAYS. INSTEAD
OF BEING AROUND 10 DEG BELOW AVG FOR THIS TIME OF YEARS...WE`LL
REACH DAILY HIGHS AROUND 10 DEG ABOVE AVG FOR THE SECOND HALF OF THE
WEEK AND INTO EARLY NEXT WEEK.

THE LEFTOVER PORTION OF THE COLD FRONT FROM THE WED STORM SYSTEM
WILL BE FORCED TO STALL NEARLY RIGHT ALONG THE I-70 CORRIDOR OF THE
UPPER MIDWEST FROM WED-TO-FRI. THIS WILL SET-UP THIS REGION FOR
CONVECTION EACH AFTN...TAPERING OFF OVER THE CNTRL APLCNS. WE`LL
HAVE LOW CHANCES FOR SHOWERS/TSTMS THU AND FRI FROM THE PORTION OF
THE BOUNDARY HOVERING OVER THE AREA...BUT FAVORABLE SVR WX
PARAMETERS WILL BE MARGINAL - INCLUDING INSTABILITY...FORCING...LL
CONVERGENCE AND SHEAR.

MED RANGE GUIDANCE INCLUDING THE GFS/NAM/EURO ALL IN GOOD AGREEMENT
ON THE SYNOPTIC-SCALE DYNAMICS FOR OUR AREA THRU FRI. ON BOARD W/
THE NAM`S DEPICTION OF THE LATE WED FEATURE...THOUGH THE EURO/GFS DO
SHOW THE TAIL END OF THE COLD FRONT SLIDING ACROSS OUR NORTH BUT IN
LESS DETAIL. THE NEXT WX-MAKER ON THE SCOPE WILL LIKELY BE ANOTHER
POTENT STORM SYSTEM OVER THE NRN PLAINS SUN/MON THAT MODELS SHOW AS
BECOMING MORE COMPLEX AS IT MOVES TOWARD THE EAST EARLY NEXT WEEK.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
VFR CONDITIONS TDA...TNGT AND TUE. W-NW WINDS GUSTING TO 20-25 KT
THIS AFTN WILL DIMINISH TOWARD SUNSET. LGT WINDS OVNGT AND TUE.

THE COLD FRONT WILL ARRIVE LATE WED NIGHT...STALLING ACROSS THE
REGION FOR THU AND EARLY FRI. THE STALLED BOUNDARY WILL
POTENTIALLY GENERATE SCATTERED SHOWERS/TSTMS DURING THE AFTN HRS
ON THU AND FRI.

&&

.MARINE...
WIDESPREAD SCA CONDITION OCCURRING THIS AFTN. A FEW SPRINKLES OVER
POSSIBLE OVER THE WATERS UNTIL ABOUT SUNSET. N-NW CHANNELING DOWN
THE BAY WILL KEEP WINDS HIGHER TNGT. SCA IN EFFECT FOR THESE
PORTIONS OF THE WATERS THRU THE OVNGT.

WINDS WILL DROP OFF ON TUE...EVEN DURING THE AFTN HRS AS HIGH
PRESSURE DRIFTS OVERHEAD AND MOVES OFFSHORE. WINDS WILL THEN SWITCH
TO SLY OVERNIGHT AND INTO EARLY WED. SLY CHANNELING WILL BEGIN W/
THE HIGH OFF THE COAST AND A COLD FRONT MOVING IN FROM THE WEST. SCA
CONDITIONS WILL LIKELY RETURN FOR THE DAYTIME HRS ON WED...SUBSIDING
AFTER THE FRONT ARRIVES AND STALLS OVER THE AREA FOR THE LATTER HALF
OF THE WEEK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...FREEZE WARNING FROM 2 AM TO 8 AM EDT TUESDAY FOR MDZ003-501-
     502.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT TUESDAY FOR MDZ004-005.
VA...FREEZE WARNING FROM 2 AM TO 8 AM EDT TUESDAY FOR VAZ025>031-
     503-504.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT TUESDAY FOR VAZ036>040-
     042-050-051-501-502.
WV...FREEZE WARNING FROM 2 AM TO 8 AM EDT TUESDAY FOR WVZ050>053-
     055-501>506.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT TUESDAY FOR ANZ532>534-537-
     540-541-543.
     SMALL CRAFT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR ANZ535-
     536-538-542.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT TUESDAY FOR ANZ530-531-539.

&&

$$
SYNOPSIS...JRK
NEAR TERM...JRK
SHORT TERM...GMS
LONG TERM...GMS
AVIATION...JRK/GMS
MARINE...JRK/GMS