Small Craft Advisory 128, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
335 PM EDT MON MAY 28 2012

.SYNOPSIS...
HIGH PRESSURE REMAINS OVER THE MID-ATLANTIC THE REST OF TODAY AND
TONIGHT. A COLD FRONT WILL APPROACH THE REGION TUESDAY BEFORE
CROSSING THE REGION TUESDAY NIGHT OR WEDNESDAY. HIGH PRESSURE
RETURNS THURSDAY. LOW PRESSURE MAY IMPACT THE AREA LATE IN THE
WEEK AND INTO THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
SFC HIPRES REMAINS OVER THE WRN ATLANTIC THIS AFTN. HOT AND HUMID
CONDITIONS WILL CONTINUE THIS AFTN UNDER THE INFLUENCE OF A STRONG
UPPER RIDGE AND SLY RETURN FLOW AROUND THE SFC HIGH. A HEAT ADVISORY
REMAINS IN EFFECT FOR THE I-95 CORRIDOR. HEAT INDICES ARE GENERALLY
IN THE MID 90S IN THE ADVISORY...WITH DMH BEING THE HIGHEST /A HEAT
INDEX OF 100F/.

DEVELOPMENT OF A DIURNAL CU FIELD HAS BEEN DELAYED A BIT COMPARED TO
RECENT DAYS WITH A STRONGER CAP IN PLACE. ABSENCE OF A SHORTWAVE
TROUGH/MCS...SFC BOUNDARY OR ANY ORGANIZED LIFT COMBINED WITH A
STRONGER CAP CASTS WILL LIMIT COVERAGE OF TSTMS THIS AFTN. SIMILAR
TO THE PAST FEW DAYS...DIFFERENTIAL HEATING HAS LEAD TO THE
DEVELOPMENT OF ISO SHOWERS/STORMS OVER THE MTS. MODIFIED RAOB
SOUNDING SHOWS MODERATE AMOUNT OF INSTABILITY DEVELOPING...SO A
CONDITIONAL THREAT OF PULSE STRONG TO SVR STORMS EXISTS. WITH WEAK
STEERING FLOW...STRONGER CAP AND ABSENCE OF FORCING VIA TERRAIN
CIRCULATIONS...CHANCE OF ANY STORMS IMPACTING THE NRN PIEDMONT...SRN
MD AND DC IS LOW THE REST OF TDA.

TSTM ACTIVITY IN THE MTS SHOULD DIMINISH AFTER SUNSET WITH THE LOSS
OF DAYTIME HEATING. A MUGGY NGT IS IN STORE FOR THE REGION...
PARTICULARLY IN THE CITIES. OVNGT LOWS RANGE FROM THE MID 60S IN THE
HIGHLANDS TO MIDDLE 70S IN THE URBAN CORRIDOR.
&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
ON TUE...HEIGHT FALLS WILL OCCUR OVER THE MID-ATLANTIC REGION AS THE
UPPER RIDGE SHIFTS EAST OF THE AREA AND AN UPPER TROUGH APPROACHES
FROM THE GREAT LAKES/OH VLY REGIONS. AS A COLD FRONT ADVANCES EWD
THRU THE MIDWEST...MODELS HAVE BEEN PERSISTENT ON THE DEVELOPMENT OF
A PRE-FRONTAL TROUGH NEAR THE BLUE RIDGE ON TUE. THE CLOUD COVER MAY
HOLD OFF ERY IN THE DAY...ESPECIALLY EAST OF THE MTS. MRNG SUNSHINE
WILL YIELD MAX TEMPS THE UPPER 80S TO NEAR 90F AND A MODERATELY
UNSTABLE AIRMASS BY THE AFTN. HI-RES MODELS SHOW DEVELOPMENT OF
CONVECTION ACROSS THE HIGHER TERRAIN AND FARTHER EAST NEAR THE
PRE-FRONTAL TROUGH DURING THE AFTN. GIVEN THE MAGNITUDE OF SFC-BASED
INSTABILITY EXPECTED AND INCREASING WIND FIELD ALOFT WITH THE
APPROACH OF THE UPPER TROUGH...SOME STORMS WILL HAVE THE POTENTIAL
TO BECOME SEVERE. BASED ON 12Z GUIDANCE...THE SETUP FOR SVR WX
APPEARS TO BE MORE FAVORABLE OVER THE NWRN CWA...WHICH RESIDES
CLOSER TO THE BETTER SYNOPTIC FORCING.
&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
COLD FRONT EXPECTED TO BE MAKING ITS WAY ACROSS THE REGION TUESDAY
NIGHT. LIKELY POPS CONTINUE ACROSS CWA. ALTHOUGH SURFACE-BASED
INSTABILITY IS EXPECTED TO DIMINISH WITH LOW-LEVEL INVERSION
OVERNIGHT...FORECAST SOUNDINGS INDICATE ENOUGH INSTABILITY ALOFT FOR
POTENTIAL ELEVATED THUNDERSTORMS AHEAD OF THE FRONT. LOW TEMPS
GENERALLY IN THE LOW 70S AHEAD OF THE FRONT AND IN THE LOW 60S
BEHIND IT...POSSIBLY IN THE UPPER 50S ATOP THE WV RIDGES.

SYNOPTIC FEATURES BECOME SOMEWHAT COMPLICATED WEDNESDAY. REMNANTS OF
BERYL ARE EXPECTED TO MOVE UP THE EAST COAST ALONG THE CAROLINAS
WHILE WEAK SURFACE HIGH PRESSURE TRIES TO NOSE INTO SRN VA. TUESDAY
NIGHT/S COLD FRONT MAY EITHER STALL OVER THE AREA...OR PUSH OFFSHORE
WHILE ANOTHER WEAK COLD FRONT DEVELOPS OVER THE APPALACHIANS AND
APPROACHES. FORECAST AT THIS POINT REDUCES POPS OVER MUCH OF THE
REGION FOR A WHILE WEDNESDAY...WITH SLIGHT CHANCE OVER THE ENTIRE
REGION WEDNESDAY AFTERNOON FOR POTENTIAL SHOWERS REDEVELOPING WITH
THE FRONTAL BOUNDARY.  AIRMASS REMAINS WARM/MOIST...BUT SLIGHTLY
COOLER/DRIER THAN TUESDAY. HIGHS GENERALLY IN THE MID 80S ACROSS THE
REGION.

FRONTAL BOUNDARY EXPECTED TO MOVE OFFSHORE BY THURSDAY
MORNING...USHERING IN A DRIER AIRMASS AS HIGH PRESSURE MOVES
INTO THE GREAT LAKES AND ADVECTS CANADIAN AIR INTO THE EASTERN
CONUS. NORTHERLY...SOMETIMES GUSTY WINDS EXPECTED THROUGH THE DAY
WITH HIGHS RANGING FROM THE UPPER 70S TO LOW 80S.

NEXT PRECIP EVENT LIKELY THURSDAY NIGHT THROUGH FRIDAY NIGHT OR SATURDAY
WHILE STRONG LOW PRESSURE DEVELOPS OVER THE MIDWEST AND MOVES ACROSS
THE MISSISSIPPI VALLEY INTO THE GREAT LAKES...DRAGGING A COLD FRONT
ACROSS THE REGION.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
SCT CU FIELD WILL DEVELOP DURING THE MID AND LATE AFTN. LATEST
MESOANALYSIS AND HIRES MODEL GUIDANCE INDICATES THAT AFTN
CONVECTION OVER THE HIGHER TERRAIN MAY NOT REACH THE TERMINALS. KEPT
TSRA OUT OF ALL TAFS FOR THIS AFTN AND EVE. WILL STILL NEED TO
MONITOR FOR A STRAY STORM MAINLY IN VICINITY OF MRB/IAD/MRB.

PERIODS OF SUB-VFR POSSIBLE AT THE TERMINALS LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING WITH SHOWERS/FOG AND A POTENTIAL TSTM OR TWO.
GENERALLY VFR WED...WITH OCCASIONAL SHOWERS PSBL. VFR WED NIGHT AND
THURSDAY. PERIODS OF SUB-VFR WITH SHRA/TSRA LIKELY FRI-SAT.

&&

.MARINE...
SLY WINDS ARE INCREASING THIS AFTN. A FEW OBS IN THE MAIN STEM OF
THE MD CHSPK BAY HAVE BEEN GUSTING TO 15 KT. DEVELOPMENT OF
NOCTURNAL JET AND SLY CHANNELING WILL ALLOW FOR 20 KT GUSTS BY THIS
EVE ACROSS SRN AND CNTRL PORTIONS OF THE MD CHSPK BAY AND THE LOWER
TIDAL POTOMAC RVR. SCA IN EFFECT FOR THESES ZONES THRU THE TNGT
PERIOD.

WINDS BELOW SCA LVLS TUE MRNG. SLY WINDS INCREASE AHEAD OF A COLD
FRONT TUE AFTN. HAVE CAPPED WINDS JUST BELOW SCA THRESHOLD
ATTM...BUT LATER SHIFTS MAY NEED TO ISSUE A SCA FOR PORTIONS OF THE
MD CHSPK BAY.

MARGINAL SCA POSSIBLE TUESDAY EVENING AS A COLD FRONT APPROACHES THE
WATERS. AT THIS POINT...FORECAST FALLS SHORT OF SCA CRITERIA WITH
GUSTS MOST LIKELY TO BE OCCASIONAL FOR A FEW HRS. SCA CONDS POSSIBLE
THU OVER SRN CHES BAY AND TIDAL POTOMAC AS THE REMNANTS OF BERYL
PASS EAST OF THE WATERS. SCA POSSIBLE AGAIN FRI-SAT WITH A FRONTAL
BOUNDARY APPROACHING.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...HEAT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR DCZ001.
MD...HEAT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR MDZ004>006-
     009>011-013-016.
VA...HEAT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR VAZ042-050>057-
     501-502.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT TUESDAY FOR ANZ532>534-537-
     540-541-543.

&&

SYNOPSIS...JRK/KS
NEAR TERM...JRK
SHORT TERM...JRK
LONG TERM...KS
AVIATION...JRK/KS
MARINE...JRK/KS

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