Area Forecast Discussion
Issued by NWS Sterling, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KLWX 300129
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
929 PM EDT MON JUN 29 2015

.SYNOPSIS...
HIGH PRESSURE MOVES EAST THIS EVENING. LOW PRESSURE OVER THE GREAT
LAKES WILL RIDE A NEARLY STATIONARY FRONT TO THE NORTH...WITH THE
ASSOCIATED COLD FRONT SWINGING INTO THE REGION ON WEDNESDAY. THIS
FRONT WILL STALL OVER THE MID ATLANTIC THROUGH SATURDAY.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
UPPER LVL TROUGH POSITIONED OVER MID WEST THIS EVENING...WITH
TROUGH AXIS ORIENTED ACROSS OH RIVER VALLEY. 00Z SFC ANALYSIS
INDICATING FRONTAL BOUNDARY EXTENDING WESTERN WV INTO CENTRAL PA.
ON GOING CONVECTION ATTM IN THE VICINITY OF THIS SFC BOUNDARY WITH
SUPPORT ALOFT COMING FROM EMBEDDED SHORTWAVE ROUNDING THE BASE OF
THE TROUGH. PCPN HAS BEEN WEAKENING/DISSIPATING AS IT NEARS THE
WESTERN FRINGES OF THE CWA WITH THE AREA HAVING BEEN CAPPED DURING
THE DAY. SOME ELEVATED INSTABILITY ALREADY IN PLACE COULD AID IN
CONTINUING THE CONVECTION FORMING TO THE WEST INTO AREAS WEST OF
THE BLUE RIDGE AS THE SHORTWAVE SWINGS EASTWARD. MINIMAL SHEAR AND
INSTABILITY OVERALL THOUGH WOULD SUGGEST A WEAKENING TREND...WITH
ONLY ISO-SCT SHOWERS EXPECTED. WILL HOLD OFF ON TSTM MENTION UNTIL
TUES MORNING. MOST OF THE AREA WILL REMAIN DRY FOR TONIGHT.

SFC LOW OVER THE OH RIVER VALLEY WILL RIDE THE NEARLY STATIONARY
FRONT ON TUES...REACHING THE EASTERN GREAT LAKES BY TUES EVENING.
MODELS DEVELOP SFC TROUGH ALONG EASTERN EDGE OF THE BLUE RIDGE BY
THE AFTN...WHICH WILL AID IN TRIGGERING AFTN CONVECTION WHEN THE
BEST SUPPORT FROM ALOFT ROUNDS THE BASE OF THE UPPER LVL TROUGH.
STRONG SURGE OF BOTH WAA AND MOISTURE ADVECTION...ESP EAST OF THE
BLUE RIDGE...WILL LEAD TO INCREASING INSTABILITY...WITH SBCAPE
VALUES BETWEEN 500-1000 J/KG. DEEP LAYER SHEAR IS FORECASTED
25-35 KTS...WHICH COMBINED WITH THE INCREASED INSTABILITY COULD
LEAD TO ISO STRONG TO SVR STORMS.

TUESDAY NIGHT...TROUGH LINGERS OVER THE AREA...ACTIVITY SHOULD
SHIFT EAST TO THE BAY THROUGH THE NIGHT. THE UPR TROUGH ENTERS THE
CNTRL APPALACHIANS LATE IN THE NIGHT...WITH SCATTERED SHOWERS
POSSIBLE. MIN TEMPS LOW TO MID 60S WEST OF THE BLUE RIDGE...UPR
60S TO LOW 70S EAST...MID 70S NEAR SHORE.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
TROF AXIS MOVE SLGTLY EAST ON WED WHILE CDFNT CREEPS SEWD TWD AREA.
OVERALL FORCING MECHANISMS DO NOT LOOK THAT GREAT. HWVR...IF EURO
DEPICTION OF S/WV CROSSING MD DURING THE DAY PANS OUT...THEN THERE
WL BE A BETTER CHC AT TSRA. SHEAR EXITS ELY...BUT STILL HV FVRBL
INSTBY PARAMETERS. HV TAKEN POPS DOWN A BIT...FCST GNLY ARND 30-40
PCT...BUT PLACED A BIT MORE EMPHASIS IN THE LEE TROF LT IN THE DAY.
DIMINISHED PCPN AFTER LOSS OF DAYTIME HEATING. KEPT TEMPS NEAR
NORMAL.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AT 12Z THU MEANDERING FRONT IS CURRENTLY PROGGED TO BE ALONG OUR
NORTHERN BORDER WITH MOST...IF NOT ALL...OF OUR AREA IN THE WARM
SECTOR. SOME QUESTION REMAINS WITH REGARDS TO TIMING OF FRONTAL
PASSAGE...WITH SOME GUIDANCE SUGGESTING FRONT PASSES THROUGH
EARLY...WHILE OTHERS SUGGEST A LATER PASSAGE. REGARDLESS...SFC LP
TRACKS ALONG THE FRONT AND...WITH BAROCLINICITY...SOME UPPER LEVEL
SUPPORT...AND DEEP MOISTURE...COULD SETUP A RATHER WET PERIOD. UPPER
LEVEL FLOW NOT OVERLY IMPRESSIVE (AOB 30 KTS AT 5H) AS SUBTLE SHORT
WAVE APPROACHES THE AREA...SO NOT EXPECTING EXTREMELY ORGANIZED
STORMS...THOUGH COULD BE ENOUGH INSTABILITY FOR STRONGER PULSE-TYPE
STORMS.

FRONT OSCILLATES AROUND THE AREA THROUGH THE REMAINDER OF THE
PERIOD...WHICH KEEPS FORECAST MUDDLED. CHC POPS REMAIN IN THE
FORECAST EACH DAY FOR MAINLY DIURNAL TSTM ACTIVITY. WITH THE
TYPICALLY FAVORED HIGHER TERRAIN LOCATIONS HAVING THE HIGHEST POPS.

TEMPS EXPECTED TO REMAIN NEAR NORMAL THROUGH THE EXTENDED
PERIOD...WITH A SLIGHT INCREASE THROUGH THE WEEKEND. DEWPOINTS NOT
OVERLY OPPRESSIVE...GENERALLY AOB 70F...WHICH SHOULD KEEP IT FROM
GETTING TOO UNCOMFORTABLE.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
MAINLY VFR CONDITIONS THRU THE TAF PERIOD EXPECTED. LIGHT SLY FLOW
TONIGHT...INCRSG 12-14Z TUES. OCNL GUSTS TO 20 KTS PSBL MIDDAY.
GENERALLY DRY WX TONIGHT...KMRB COULD SEE A STRAY SHOWER. INCRG
CHC OF SHOWER/TSTM ON TUES...ESP DC/BALTIMORE TAF SITES. HARD TO
PINPOINT TIMING AT THIS TIME...SO WILL MAINTAIN VCTS THRU THE AFTN
HOURS. ANY TSTM COULD REDUCE CONDITIONS MVFR OR LOWER...AS WELL AS
BRING A BRIEF PERIOD OF GUSTY-STRONG WINDS AND HEAVY RAIN.

LOW CONFIDENCE IN FLGT RESTRICTIONS WED. POTL CERTAINLY THERE...BUT
TIMING/PLACEMENT A REAL STRUGGLE. VFR SHUD PREVAIL MOST OF THE
TIME.

MOST PERIODS THU THRU SAT WILL BE VFR...THOUGH EXPECT SUB-VFR
CONDS IN ANY TSTM ACTIVITY. VARIABLE WINDS EXPECTED THROUGH THE
PERIOD.

&&

.MARINE...
SUB-SCA CONDITIONS TONIGHT. SLY FLOW INCREASES TO 15 TO 20 KT
WITH GUSTS UP TO 25 KT ON TUES. SCA FOR ALL WATERS BEGINS AT 10AM
TUES AND CONTINUES UNTIL 8PM...WILL CONTINUE THE SCA INTO THE
OVERNIGHT FOR ALL WATERS MINUS NORTHERN ZONES OF THE CHESAPEAKE.
SCATTERED GUSTY THUNDERSTORMS DEVELOP LATE TUESDAY AFTN AND
CONTINUE THROUGH TUESDAY NIGHT.

WINDS AOB 10 KT WED-WED NGT...MAINLY FM THE SW.

WINDS EXPECTED TO REMAIN BELOW SCA CRITERIA THROUGH THE
EXTENDED...THOUGH WILL NEED TO MONITOR AS FRONT WILL BE NEAR AREA
EACH DAY. AFTN TSTMS ARE ALSO POSSIBLE EACH DAY...WHICH COULD IMPACT
MARINE CONCERNS.

&&

.TIDES/COASTAL FLOODING...
WATER LVLS WL BE INCREASING TONIGHT THRU MID WEEK. THE
WATER LVLS MAY APPROACH MINOR THRESHOLDS AROUND SW DC HIGH TIDE
TUES MORNING...AND THEN AGAIN WED ALONG THE WESTERN CHESAPEAKE DURING
THE HIGHER HIGH TIDE...WHICH IS THE AM CYCLE /MIDNGT THRU NOON/.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM TUESDAY TO 4 AM EDT WEDNESDAY
     FOR ANZ531>534-536-537-539>543.
     SMALL CRAFT ADVISORY FROM 10 AM TO 8 PM EDT TUESDAY FOR ANZ530-
     535-538.

&&

$$
SYNOPSIS...BAJ
NEAR TERM...BAJ/SEARS
SHORT TERM...HTS
LONG TERM...MSE
AVIATION...MSE/HTS/SEARS
MARINE...BAJ/MSE/HTS/SEARS
TIDES/COASTAL FLOODING...HTS/SEARS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.