Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 041440
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1040 AM EDT MON MAY 4 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OFF THE CAROLINA COAST THROUGH TONIGHT.
A COLD FRONT OVER THE UPPER MIDWEST WILL PUSH SLOWLY SOUTH...STALLING
ACROSS THE MID ATLANTIC THROUGH MIDWEEK. HIGH PRESSURE IS EXPECTED
TO RETURN TO THE REGION LATE IN THE WEEK WHILE LOW PRESSURE
DEVELOPS SOUTH OF FLORIDA AND MOVES SLOWLY UP THE SOUTHEAST COAST.

&&

.NEAR TERM /TODAY/...

SFC HIGH PRESSURE CURRENTLY OFF THE CAROLINA COAST WILL PUSH
OFFSHORE TODAY...SETTLING TO THE EAST BY TONIGHT. AS THE REGION
REMAINS ON THE WESTERN PERIPHERY OF THE HIGH...S-SW FLOW WILL BE
PERSISTENT. WAA ON THIS FLOW WILL RESULT IN A GOOD WARM UP FOR THE
AREA...WITH MOST OF THE AREA REACHING THE 80S...THE EXCEPTION
BEING THE HIGHER ELEVATIONS OF THE POTOMAC HIGHLANDS.

ALL MESO MODELS SUGGESTING ISO PCPN DEVELOPMENT OVER THE FAR
SOUTHWESTERN CORNER OF THE CWA LATE IN THE DAY/DURING THE
EVENING...WITH THE SUGGESTION OF A SFC TROUGH EXTENDING ACROSS
EASTERN WV. HAVE INCLUSION OF LOW END SLIGHT CHC POPS TO ACCOUNT FOR
ANY DEVELOPMENT THAT MAKES IF OVER THE RIDGE LINE. ANYTHING THAT
DOES FORM WILL BE VERY LIGHT IN NATURE AND SHORT LIVED.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...

ANY LINGERING PCPN THIS EVENING WILL QUICKLY DIMINISH WITH LOSS
OF DAYTIME HEATING. DRY WX THEN EXPECTED THRU MOST OF THE NIGHT.
LOW PRESSURE TREKKING THRU SOUTHERN CANADA WILL DRAG ITS
ASSOCIATED COLD FRONT CLOSE TO THE REGION TONIGHT...WITH THE FRONT
STRADDLING PA BY 12Z TUES. WILL INTRODUCE POPS AROUND DAYBREAK
NEAR THE MASON-DIXON LINE OF WESTERN MD TO ACCOUNT FOR THE FRONTS
PLACEMENT AS WELL AS A WEAK SHORTWAVE/VORT MAX EXPECTED TO MOVE
THRU TUES MORNING.

THE COLD FRONT NUDGES SOUTH DURING THE DAY...EVENTUALLY STALLING
JUST SOUTH OF THE MASON-DIXON LINE THRU TUES NIGHT. NEAR ZONAL FLOW
SETS UP ALOFT...SO EXPECTING ANY PCPN DEVELOPMENT TUES TO BE
CONFINED NEAR THE FRONTAL BOUNDARY WITH THE BEST SFC CONVERGENCE.
HAVE CHC POPS IN OVER NORTHERN AREAS...TAPERING OFF TO THE
SOUTH...WITH POTENTIAL FOR SOME AREAS OF THE PIEDMONT TO REMAIN DRY
THRU THE PERIOD. WITH HIGHS PUSHING INTO THE 80S YET AGAIN...AND SW
FLOW INJECTING IN MORE MOIST AIR...MINIMAL INSTABILITY IS PSBL.
SHEAR AND LAPSE RATES ARE ON THE WEAKER SIDE...BUT ENOUGH WITH THE
INSTABILITY TO TRIGGER AN ISO TSTM. SO WILL HAVE THUNDER MENTION FOR
TUES AFTN. WITH THE LOSS OF DAYTIME HEATING...WILL KEEP THUNDER
MENTION OUT FOR TUES NIGHT. POPS DECREASE SECOND HALF OF TUES
NIGHT.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...

CDFNT WL CONT TO SAG INTO THE CWFA WED...WHICH WL PROVIDE SRN
CNTYS WITH A BETTER CHC AT SEEING PCPN. HWVR...THE FNT WL BE
BUMPING INTO THE H5 RDG...SO NOT ONLY WL SRN PROGRESS BE SLOW BUT
ALSO SUSPECT THERE WL BE A WEAKENING TREND. THEREFORE WL NOT BE
GOING W/ POPS HIER THAN CHC. SUCH A BAROCLINIC ZONE IN A SUMMER
AMS WL YIELD A LTL INSTBY...BUT THAT WL BE UNDERCUT BY ELY SFC
FLOW. AM KEEPING SCHC THUNDER IN GRIDS BUT DO NOT BELIEVE ANY
STORMS WL BE A REALLY BIG DEAL. TAPERED MAXT BACK A PINCH DUE TO
THE MARITIME INFLUENCE... BUT TIMING OF NOT JUST THE FNT BUT ALSO
THE WINDS AND ANY PCPN WL UNLIMATELY DETERMINE THE MAXT OUTCOME.

FNT LOOKS TO WASH OUT THU...W/ RDGG MAINTAINING ITS INFLUENCE THRU
SAT. DRY FCST. TEMPS ON THE WARM SIDE...AND REFLECTS ADTL WARMING
DAILY. THERE WL BE MORE CLDS ON THU DUE TO RESIDUAL MSTR...BUT WL
BE PTSUN AT WORST FOR CENTRAL VA/SRN MD. OTRW...MOSUN-SUNNY THRU
THE PD. NEXT FNT MAY ARRIVE BY SUNDAY.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...

VFR CONDITIONS FOR THE TAF PERIOD.

INCRSG CHC OF SHOWERS AND MAYBE AN ISO TSTM ON TUES...MAINLY AFTR
18Z FOR ALL SITES EXCEPT KCHO.

LCL FLGT RESTRICTIONS PSBL INVOF SHRA WED...OTRW VFR THRU THE END OF
THE WEEK.

&&

.MARINE...

SUB-SCA CONDITIONS THIS MORNING. INCRSG SLY FLOW TODAY SHOULD
RESULT IN ENOUGH OF A CHANNELING EFFECT TO PRODUCE GUSTS TO 20
KTS FOR THE CHESAPEAKE BAY AND LOWER TIDAL POTOMAC WATERS. SCA IN
EFFECT FOR THESE ZONES BEGINNING THIS AFTN FOR THIS. FOR
TONIGHT...WINDS EXPECTED TO DIMINISH TO SUB-SCA OVER THE NORTHERN
CHESAPEAKE BAY...AND THEN THE LOWER TIDAL POTOMAC BY TOMORROW
MORNING. WILL CONTINUE SCA FOR THE MID CHESAPEAKE ZONE THRU TUES
MORNING...WITH PSBL EXTENSION INTO TUES IF WINDS ARE SLOW TO SHIFT
TO A WEST COMPONENT. SUB-SCA CONDITIONS ALL WATERS FOR TUES NIGHT.

ELY FLOW BHD A CDFNT DROPPING SLOWLY SWD WED. MAY HV A BRIEF
SURGE IN WIND SPDS...BUT MIXING SHUDNT BE THAT GREAT. WL BE
CAPPING WINDS AT 15 KT. AFTER THAT...WINDS WL BE ON THE LIGHTER
SIDE ONCE AGAIN /AOB 10 KT/ UNDER A RIDGE AXIS.

&&

.CLIMATE...
THE WARMEST AIR MASS OF THE YEAR SO FAR IS MOVING OVER THE AREA
FOR THE FIRST HALF OF THE WEEK. BELOW IS A LIST OF THE LAST TIME A
HIGH TEMPERATURE OF 85 DEGREES OR HIGHER WAS OBSERVED.

SITE..LAST 85+ DEGREE DAY...
DCA...SEPTEMBER 27TH 2014...
BWI...SEPTEMBER 11TH 2014...
IAD...SEPTEMBER 11TH 2014...
CHO...SEPTEMBER 21ST 2014...
DMH...SEPTEMBER 11TH 2014...
HGR...SEPTEMBER 6TH 2014....
MRB...SEPTEMBER 21ST 2014...

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 8 PM EDT THIS
     EVENING FOR ANZ538-539-542.
     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO NOON EDT
     TUESDAY FOR ANZ534-543.
     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 2 AM EDT
     TUESDAY FOR ANZ540-541.
     SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 2 AM EDT
     TUESDAY FOR ANZ531>533.
     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EDT
     TUESDAY FOR ANZ537.

&&

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


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