-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KAKQ 140035
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
835 PM EDT MON MAY 13 2013

.SYNOPSIS...
CANADIAN HIGH PRESSURE WILL BUILD INTO THE REGION TONIGHT INTO
TUESDAY BRINGING UNSEASONABLY COOL TEMPERATURES...BEFORE SLIDING
OFF THE COAST BY TUESDAY NIGHT. MUCH WARMER TEMPERATURES WILL
RETURN WEDNESDAY AND PERSIST INTO THE UPCOMING WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
THE LATEST VISIBLE SATELLITE IMAGERY SHOWS AN EXTENSIVE CU/SC FIELD
SPREADING NW-SE ACROSS THE AREA AHEAD OF A POTENT VORT MAX/PV
ANOMALY DIVING SE ACROSS THE ALLEGHENY PLATEAU. THE REGIONAL RADAR
MOSAIC INDICATES NUMEROUS LIGHT ECHOES ACROSS THE REGION.
HOWEVER...VERY LITTLE IS REACHING THE GROUND DUE TO A VERY DRY WELL
MIXED BOUNDARY LAYER. HI-RES DATA CONTINUES TO INDICATE THE
POTENTIAL FOR A FEW LIGHT SHOWERS AS A WEAK SURFACE TROUGH SWINGS
THROUGH THE AREA. GIVEN THIS...ISOLATED POPS WILL BE MAINTAINED
THROUGH 00Z.

THE NEXT ISSUE WILL BE THE POTENTIAL FOR FROST AND RECORD LOWS EARLY
TUE MORNING (SEE CLIMATE SECTION) AS A 1025MB SURFACE HIGH BUILDS
INTO THE AREA. THE BEST POTENTIAL FOR FROST WILL BE ACROSS THE
PIEDMONT AND S-CENTRAL VA AS THESE LOCATIONS WILL HAVE THE BEST
POTENTIAL TO BECOME CALM LATE TONIGHT. FARTHER EAST...THERE SHOULD
BE ENOUGH MIXING/LIGHT CAA TO INHIBIT FROST. A FROST ADVISORY HAS
BEEN ISSUED FOR RURAL LOCATIONS OF THE PIEDMONT AND S-CENTRAL VA. IT
IS SOMEWHAT MARGINAL...BUT HAVE DECIDED TO RAISE THE HEADLINE GIVEN
THAT IT IS MID-MAY (AS OPPOSED TO MID-APRIL) AND THE GROWING SEASON
IS UNDERWAY. FOLLOWED CLOSER TO THE COOLER MAV GUIDANCE (WHICH
PERFORMED BETTER THIS MORNING) AND THIS INDICATES LOWS IN THE MID
30S OVER THE PIEDMONT AND S-CENTRAL VA...WITH MID/UPPER 30S FOR THE
NORTHERN NECK TO LOWER MD EASTERN SHORE...AND UPPER 30S TO MID 40S
FARTHER SE.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
THE HIGH SLOWLY DRIFTS OVER THE AREA TUESDAY AND THEN OFFSHORE
TUESDAY NIGHT. 850MB TEMPS REMAIN AROUND -2 TO -3 ST DEV BELOW
NORMAL SO HIGHS WILL REMAIN COOL...BUT SHOULD BE SLIGHTLY MILDER (~
-1.5 ST DEV) DUE TO MORE SOLAR INSOLATION (MAINLY 65-70). HIGH
CLOUDS SHOULD BEGIN TO INCREASE DURING THE AFTERNOON AS MID-LEVEL
RIDGING ENCROACHES FROM THE WEST. SIGNIFICANT WAA IS EXPECTED
TUESDAY NIGHT AS MID-LEVEL RIDGE QUICKLY BUILDS IN. THERE IS A
DECENT AMOUNT OF MOISTURE WITHIN THE 800-500MB LAYER RESULTING IN
CONSIDERABLE CLOUD COVER. LOWS WILL BE MUCH MILDER RANGING FROM THE
UPPER 40S TO LOW 50S.

WAA SHIFTS BELOW 800MB WEDNESDAY RESULTING IN MUCH WARMER
TEMPERATURES. ADDITIONALLY SURFACE DEWPOINTS RISE WITH SW LOW-LEVEL
FLOW. 850MB TEMPERATURES RISE TO ~16-18C BY LATE AFTERNOON AND THIS
SHOULD HELP TEMPERATURES TO AND RANGE FROM THE UPPER
60S/LWR 70S ALONG THE IMMEDIATE COAST...TO 75-80 IMMEDIATELY
INLAND...TO THE MID 80S ALONG/W OF I-95. THE ONLY CAVEAT TO THE
WARMING TREND COULD BE IF CLOUD COVER DOES NOT BREAK (POSSIBLE IF A
BOUNDARY WERE TO DEVELOP).

LATER WEDNESDAY AFTERNOON/WEDNESDAY NIGHT...A BELT OF 850-700MB
LAPSE RATES > 7.5C/KM PASSES OVER THE REGION. MLCAPE VALUES ARE
AROUND 1200-1600 J/KG (GFS) AND 1600-2000 (NAM) ALONG WITH A SURFACE
WARM MOIST THETA-E AXIS. GIVEN THIS...THERE WILL BE A CHANCE OF
THUNDERSTORMS ESPECIALLY OVER THE NE DURING THE LATE AFTERNOON AND
EVENING. MUCH OF THIS WILL ULTIMATELY BE DICTATED BY UPSTREAM
ACTIVITY IN WNW FLOW.

A SIMILAR SCENARIO SETS UP THURSDAY. HOWEVER...CHANCES MAY BE A
LITTLE HIGHER AS A THETA-E BOUNDARY DROPS DOWN FROM THE N. HIGHS
SHOULD RANGE FROM THE LOW TO MID 80S...WITH LOCALLY COOLER READINGS
ALONG THE IMMEDIATE ATLANTIC COAST.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
SFC HIGH PRESSURE AND UPPER LEVEL RIDGING DOMINATE THE WEATHER
PATTERN...WHICH WILL PUMP AN INCREASINGLY WARMER AIRMASS INTO THE
MID ATLANTIC REGION THU NIGHT THROUGH THE WEEKEND AND INTO EARLY
NEXT WEEK. A FRONT WILL MOVE OFF THE CAROLINA COAST THU NIGHT AND
PRECIP WILL COME TO AN END FROM NW TO SE. SFC HIGH PRESSURE RETURNS
FRI AND SLIDES JUST OFF THE EAST COAST FRI NIGHT...BECOMING
RELATIVELY STATIONARY INTO EARLY NEXT WEEK. MEANWHILE...UPPER LEVEL
RIDGING OVER THE CTRL U.S. THU NIGHT IS EXPECTED TO SHIFT OVER THE
MIDWEST ON SAT...THEN MOVE OVER THE MID ATLANTIC REGION ON SUN. THE
RIDGE AXIS PASSES OVER THE AREA EARLY MON AND MOVES JUST OFF THE
COAST BY MON EVENING. IF THIS INDEED HAPPENS...MON COULD BE THE
HOTTEST DAY IN THIS STRETCH OF WARMER TEMPERATURES. THE
CAVEAT TO THIS IS THAT UPPER TROUGHS HAVE A TENDENCY TO SLOW THEIR
EWD PROGRESSION AS THEY DIG SWD AND THE UPPER RIDGE AMPLIFIES. IF
THIS HAPPENS...THEN THE PASSAGE OF THE RIDGE AXIS AND THE SUBSEQUENT
WARMEST TEMPERATURES COULD BE DELAYED UNTIL TUE. MAX TEMPERATURES
SHOULD EXPERIENCE A BRIEF COOL DOWN INTO THE LOWER-MID 80S FRI
BEHIND THE EXITING BOUNDARY...THEN WARM AGAIN (POTENTIALLY INTO THE
UPPER 80S) BY THE END OF THE WEEKEND. VARIOUS MODEL SOLUTIONS HAVE
DIFFERENT TIMING REGARDING SHORTWAVE FEATURES AND SUBSEQUENT
RAINFALL (MORE ON THIS IN THE NEXT PARAGRAPH)...SO WILL BE
CONSERVATIVE WITH THE WARM-UP FOR NOW. LOW TEMPS WILL GENERALLY BE
IN THE UPPER 50S TO MID 60S. DEWPOINTS WILL ALSO BE RISING INTO THE
60-65 DEGREE RANGE AND WILL CREATE SOMEWHAT HUMID CONDITIONS
THROUGHOUT THE EXTENDED PERIODS.

IN ADDITION TO VARIOUS TIMING OF SHORTWAVE FEATURES/PRECIP AMONG
LONG RANGE MODELS...THE WEATHER PREDICTION CENTER (WPC...FORMERLY HPC)
INDICATES THAT A PERSISTENT/STATIONARY FRONTAL BOUNDARY WILL BE
DRAPED W TO E FROM THE OHIO VALLEY TO/ALONG THE MASON-DIXON LINE THU
NIGHT INTO EARLY NEXT WEEK. THE COMBINATION OF THIS BOUNDARY WITH
THE AFOREMENTIONED SHORTWAVES WILL MAKE AFTN/EVENING SHOWERS AND
STORMS POSSIBLE EACH DAY.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
MID LEVEL CLOUDINESS ASSOCIATED WITH A SHORT WAVE TROUGH WILL CLEAR
OFF TOWARD MIDNIGHT AS THE TROUGH MOVES OFFSHORE. NW WINDS WERE
ALREADY DIMINISHING AS OF 23Z AND VELOCITIES WILL GENERALLY RUN AT 5
KNOTS OR LESS OVERNIGHT. THE ONLY EXCEPTION WILL BE AT ORF WHERE
INFLUENCE FROM THE BAY WILL KEEP WINDS A BIT STRONGER. THERE IS NO
THREAT FOR FOG WITH DEW POINTS RUNNING SEVERAL DEGREES LOWER THAN
FORECAST TEMPERATURES.

NAM BUFR SOUNDINGS INDICATE MORE MID LEVEL CLOUDINESS ON TUESDAY. A
BAND OF MOISTURE AT AROUND 600 MB (14K FT) BENEATH AN UPPER LEVEL
JET STREAM WILL MOVE OVER THE AREA TUESDAY AFTN. SCT CU MAY ALSO
DEVELOP AT AROUND 7K FT. NW SURFACE WINDS WILL BACK TO W/SW OVER
INLAND AREAS TUESDAY AFTN.

OUTLOOK...WINDS BECOME LIGHT AND VARIABLE TUESDAY NIGHT UNDER THE
INFLUENCE OF SURFACE HIGH PRESSURE WHICH WILL BE OVER THE AREA. LOW
DEW POINTS AGAIN WILL PRECLUDE FOG DEVELOPMENT.

VFR AND DRY WEATHER IS EXPECTED WEDNESDAY THROUGH EARLY THURSDAY.
THERE WILL BE A DAILY CHANCE FOR AFTERNOON AND EVENING TSTMS
THURSDAY THROUGH SATURDAY. ONLY SCATTERED COVERAGE IS INDICATED.
-- End Changed Discussion --

&&

.MARINE...
WILL MAINTAIN SCA HEADLINES FOR THE CHES BAY FM 7 PM THIS EVENG INTO
TUE MORNG...AS DECENT SURGE OF N WINDS OCCURS AS HI PRES BLDS TWD
THE REGION FM THE W. ALSO...EXPECT 15-20 KT OVER THE CSTL WTRS AS
WELL WITH SEAS 3-4 FT. HI PRES MOVES DIRECTLY OVER THE AREA TUE AFTN
WITH WINDS 10 KT OR LESS. SSW FLO RETURNS TUE NGT THRU THU...AS THE
HI SLIDES INTO THE ATLC. A WEAK FRONT WILL CROSS THE AREA THU NGT
INTO FRI MORNG...WITH WINDS SHIFTING FM WSW TO THE NW OR N ARND 10
KT OR LESS.

&&

.CLIMATE...
RECORD LOW TEMPERATURES WILL BE POSSIBLE TUESDAY MORNING (MAY 14TH):

RECORD LOWS FOR MAY 14TH:
NOTE...THE VALUE FOR ELIZABETH CITY HAS BEEN UPDATED.

RICHMOND....40 (1941)
NORFOLK.....43 (2007)
SALISBURY...32 (2007)
ELIZ CITY...40 (2008)

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...FROST ADVISORY FROM 3 AM TO 7 AM EDT TUESDAY FOR VAZ048-049-
     060>063-065>071-079>081-087>089-092.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EDT TUESDAY FOR ANZ630>632-634.

&&

$$
SYNOPSIS...AJZ/LKB
NEAR TERM...AJZ
SHORT TERM...AJZ/LKB
LONG TERM...BMD
AVIATION...LSA
MARINE...TMG
CLIMATE...