Severe Thunderstorm Warning 143, NWS Wakefield, VA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
746 PM EDT TUE JUN 28 2011

.SYNOPSIS...
A COLD FRONT CROSSES THE MID ATLANTIC TONIGHT. HIGH PRESSURE
BUILDS IN FROM THE WEST WEDNESDAY...AND SETTLES OFF THE SOUTHEAST
COAST LATER IN THE WEEK. A STRONG UPPER LEVEL RIDGE OF HIGH
PRESSURE BUILDS INTO THE REGION NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A WARM AND HUMID AIRMASS REMAINS IN PLACE OVER THE FORECAST AREA
THIS AFTERNOON. SCATTERED THUNDERSTORMS HAVE QUICKLY DEVELOPED
ACROSS WESTERN AND CENTRAL VA BETWEEN 18 AND 19Z. A MORE ORGANIZED
LINE IS IN THE EXTREME WESTERN PORTION OF THE STATE CLOSER TO THE
LEADING EDGE OF A COLD FRONTAL ZONE...WITH LESS ORGANIZED ACTIVITY
FARTHER EAST. ANY THUNDERSTORMS THIS AFTERNOON INTO THIS EVENING
COULD PRODUCE STRONG WIND GUSTS AND HAIL...AND SPC HAS INCLUDED MOST
OF THE AREA TO A SLIGHT RISK FOR SEVERE STORMS. PW ON THE 12Z KWAL
SOUNDING WAS 1.7 IN...AND THE LATEST PW ANALYSIS HAS VALUES OF 1.7-2
IN...SO THIS COMBINED WITH A WEAK WIND PROFILE WILL PRODUCE A
POTENTIAL FOR VERY HEAVY RAIN IN ANY SHOWERS OR STORMS. 1 HR FFG IS
MAINLY AROUND 3 IN/HR FOR MUCH OF THE AREA...SO FLOODING IS NOT
EXPECTED TO BE A MAJOR ISSUE. ALTHOUGH LOCALIZED NUISANCE LOW-LYING
AREA/POOR DRAINAGE FLOODING COULD OCCUR.

THE COLD FRONT MOVES INTO THE REGION TONIGHT AND SLOWS DOWN AS THE
UPPER TROUGH AXIS LAGS TO THE WEST. THERE APPEARS TO BE A DECENT
CHANCE OF RAIN FOR THE EASTERN ZONES OVERNIGHT...ALTHOUGH THOSE
AREAS HAVE MANAGED TO AVOID RAIN RECENTLY...SO WILL TRY NOT TO BE
TOO OPTIMISTIC. THE STRONG TO SEVERE POTENTIAL SHOULD DIMINISH THIS
EVENING. LOW TEMPERATURES SHOULD ME MILD (UPPER 60S W TO MID 70S SE)
WITH CLOUDS AND SHOWERS.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
THE COLD FRONT SLOWLY MOVES OFF THE COAST WEDNESDAY MORNING. MODEL
SOUNDINGS AND TIME-HEIGHT CROSS-SECTIONS SUGGEST SHOWERS...AND
POSSIBLY A THUNDERSTORM COULD LINGER OVER SE PORTIONS MAINLY EARLIER
IN THE MORNING. ELSEWHERE...DRIER AIR WILL FILTER IN FROM THE
NORTHWEST...WITH PARTLY CLOUDY CONDITIONS GIVING WAY TO MAINLY CLEAR
CONDITIONS. AN ISOLATED SHOWER OR THUNDERSTORMS COULD PERSIST
IMMEDIATELY NORTH OF THE ALBEMARLE SOUND WITH DRY AIR OVERSPREADING
LINGERING LOW-LEVEL MOISTURE. HIGH TEMPERATURES WILL RANGE FROM THE
MID TO UPPER 80S WITH LOCALIZED LOW 80S ALONG THE IMMEDIATE ATLANTIC
COAST.

NW FLOW ALOFT WILL PREVAIL WEDNESDAY NIGHT THROUGH FRIDAY OVER THE
MID ATLANTIC AS A STRONG UPPER RIDGE BUILDS OVER THE MISSISSIPPI
VALLEY AND AN UPPER TROUGH LINGERS OVER ATLANTIC CANADA. AT THE
SURFACE...HIGH PRESSURE WILL BUILD INTO THE REGION WEDNESDAY NIGHT
AND MOVE OFF THE COAST THURSDAY NIGHT...WITH A LEE-TROUGH
POTENTIALLY SETTING UP OVER CENTRAL VA FRIDAY AS THE SURFACE HIGH
SETTLES OFF THE SOUTHEAST COAST. A WEAK IMPULSE IN THE NW FLOW MAY
BRING OCCASIONAL PASSING CLOUDS LATER THURSDAY NIGHT INTO FRIDAY
OTHERWISE...THE SKY SHOULD BE MAINLY CLEAR. DEWPOINTS WILL BE QUITE
COMFORTABLE FOR LATE JUNE AS AFTERNOON READINGS SHOULD FALL INTO THE
MID 50S TO AROUND 60...WITH VALUES SLIGHTLY HIGHER FROM VA BEACH
AREA TO THE NORTHERN SHORE OF THE ALBEMARLE SOUND.

HIGH TEMPERATURES THURSDAY SHOULD BE IN THE LOW TO MID
80S...FOLLOWED BY MAXIMA IN THE UPPER 80S TO LOW 90S FRIDAY. MORNING
LOW TEMPERATURES THURSDAY AND FRIDAY SHOULD RANGE FROM THE UPPER 50S
TO LOW 60S IN INLAND RURAL LOCATIONS TO THE MID TO UPPER 60S IN
URBAN AND COASTAL LOCATIONS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
NO MAJOR CHANGE IN THINKING FOR THE HOLIDAY WEEKEND INTO EARLY NEXT
WEEK. UPPER LVL LONGWAVE PATTERN FOR THE MEDIUM RANGE TIME FRAME
CONTINUES TO BE CHARACTERIZED BY BROAD UPR LVL RIDGING OVER THE
CENTRAL/SOUTHERN PLAINS BUILDING EAST TO A POSITION OVER THE
SOUTHEASTERN US FOR HOLIDAY WEEKEND INTO ERY NEXT WEEK...EVENTUALLY
BECOMING DISLODGED/SHUNTED BACK SW BY STRONG SHORTWAVE ENERGY
TRAVERSING CENTRAL/EASTERN CANADA. THIS WILL TRANSLATE TO VERY
WARM/HOT CONDITIONS FOR THE HOLIDAY WEEKEND INTO EARLY NEXT
WEEK...WITH TEMPERATURES SLOWLY MODERATING BACK TOWARDS SEASONAL
VALUES TOWARDS THE MIDDLE OF NEXT WEEK.

GENERALLY BENIGN/DRY CONDITIONS FRIDAY NGT-SAT COURTESY OF HIGH
PRESSURE OVER THE OHIO VALLEY WL GIVE WAY TO INCREASING (MAINLY
DIURNALLY DRIVEN) RAIN CHCS BY SUN/MON AS RIDGE BUILDS EAST W/
RESULTANT SURFACE FLOW VEERING TO BECOME S-SW BY SUNDAY/MONDAY.
DESPITE CONTINUED WARM/DRY AIRMASS IN PLACE...STRONG INSOLATION/LLVL
INSTABILITY AND THE PRESENCE OF A WEAK LEE TROUGH COULD WELL PROVIDE
A FOCUSING MECHANISM FOR TYPICAL SCT AFTN CONVECTION SUNDAY AFTN/EVE
AND ONCE AGAIN ON MONDAY AFTN. WEAK COLD FRONT WL BE SHUNTED SOUTH
BY MIDWEEK...BUT HAVE KEPT POPS SLIGHT CHC OR LESS FOR NOW.

FOR TEMPERATURES...TEMPERATURES EASILY INTO THE MID 90S INLAND
(U80S/NR 90 AT IMMEDIATE COAST) OVER THE HOLIDAY WEEKEND...YIELDING
HEAT INDICES IN THE 100-103 RANGE SAT/SUNDAY. TEMPERATURES DO
EVENTUALLY MODERATE BACK INTO THE UPR 80S-LOWER 90S TOWARDS THE
MIDDLE OF NEXT WEEK. EARLY MORNING LOWS TO GENERALLY RANGE THROUGH
THE 60S.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
SFC TROF AND SLOW MOVG COLD FRONT PUSHING THRU THE REGION THIS
EVENING. STRONG SHOWERS AND TSTMS AFFECTING CENTRL AND NRN VA
AHEAD OF THE FRONT. FRONT EXPECTED TO MOVE THRU RIC AFT MIDNIGHT
AND PUSH INTO CENTRL NC DURING EARLY MORNG HRS. HOWEVER BNDRY
MAY STALL NEAR THE SE VA/NE NC BORDER. TSTMS WILL LIKELY PERSIST
FOR PORTIONS OF THE CWA INTO THE LATE EVENING AND PSBLY AFT
MIDNIGHT. WNDS WILL SHFT FROM SW-W-N WITH FROPA. GRADUAL CLEARING
DURING THE OVERNIGHT AS WX DIMINISHES AND FRONT MOVES EAST.

OUTLOOK...VFR CONDITIONS AND DRY WEATHER WILL PREVAIL WEDNESDAY
AFTN THROUGH SATURDAY.

&&

.MARINE...
LIGHT SW FLOW CONTINUES THROUGH TNGT AHEAD OF A WEAK COLD
FRONT...WHICH WILL DROP ACROSS THE WATERS LATE TONIGHT/EARLY WED
MORNING. THE TIGHTENING GRADIENT AHEAD OF THIS FRONT WL ALLOW FOR
MODEST INCREASE IN WINDS LATER THIS AFTN/EVENING AND OVERNIGHT.
GIVEN WATER TEMPS IN THE UPR 70S...THINKING IS THAT SHALLOW
OVER-WATER INSTBY SHOULD SET THE STAGE FOR A MARGINAL/BRIEF SURGE
(MARGINAL SCA CONDITIONS) OVER CHES BAY EARLY WED MORNING.
THEREFORE...HV HOISTED SCA OVER THE CHES BAY FOR JUST BEFORE SUNRISE
WED MORNING THROUGH MIDDAY...WITH SUB-SCA (I.E. NO HEADLINES)
CONDITIONS EXPECTED OVER THE COASTAL WATERS. BOATING CONDITIONS TO
BECOME MORE TRANQUIL BY THURSDAY...WITH S-SW FLOW AND PLEASANT
BOATING CONDITIONS EXPECTED THROUGH THE FIRST HALF OF THE HOLIDAY
WEEKEND.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 1 PM EDT WEDNESDAY FOR
     ANZ630>632-634.

&&

SYNOPSIS...AJZ
NEAR TERM...AJZ
SHORT TERM...AJZ
LONG TERM...MAM
AVIATION...MAM/JEF
MARINE...MAM

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