Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 300050
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
850 PM EDT WED JUL 29 2015

.SYNOPSIS...
A COLD FRONT WILL CROSS THE AREA LATE THURSDAY. HIGH PRESSURE WILL
BUILD FOR THE WEEKEND AND HOLD THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
PCPN CVRG HAS BEEN MUCH SPOTTIER...AND LIGHTER...THAN THIS TIME
YDA. WARM LYR BTWN H6-4 ON 00Z LWX RAOB LKLY THE REASON WHY. RDR
TRENDS SEEM TO HV BEEN CAPTURED BY THE HRRR QUITE WELL. STORMS E
OF THE BLURDG HV DSPTD...W/ ONLY A FEW CELLS IN THE PTMC
HIGHLANDS. IF LTST CYCLE OUTPUT VERIFIES...EVEN THIS ACTIVITY WL
ERODE BEFORE MIDNGT...W/ NOT MUCH GOING ON TIL NEW CELLS APPROACH
THE APLCNS PREDAWN. HV ADAPTED GRIDS TWD THIS DIRECTION...BUT HV
HELD ONTO LOW POPS IN THE MTNS. THAT CAN BE REEVALUATED.

NOT NEARLY AS MUCH WET GRND AS PAST CPL NGTS. HWVR A FAIR AMT OF
CLR SKIES AND DEWPTS IN THE LWR-MID 70S SUGGESTS THERE WL ONCE AGN
BE POTL FOR FOG DVLPMNT. HV KEPT IT PATCHY AND NOT DENSE DUE TO
REASONS MENTIONED ABV...SITUATED ALONG/W OF BLURDG AS WELL AS
ACRS NRN MD.

CDFNT CURRENTLY MOVING THROUGH THE MIDWEST WILL ENTER THE FCST
AREA AROUND 18Z THU AND SHOULD CLEAR THE FCST AREA BY 03Z FRI.
FRONT WILL BE LOSING MUCH OF ITS PUNCH BUT IT APPEARS THERE COULD
BE A QUICK BAND OF -SHRA/TSRA RIGHT ALONG OR JUST BEHIND THE
FRONT.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
12Z MODEL SUITE HAS THE COLD FRONT PLACED JUST SOUTHEAST OF THE
CWA BY 12Z FRIDAY. ANY LINGERING PCPN WITH THE FRONT SHOULD REMAIN
TO THE SOUTH AS THE FRONTAL BOUNDARY STALLS AND EVENTUALLY
DISSIPATES OVER THE WEEKEND. SFC HIGH PRESSURE BUILDS IN FROM THE
WEST IN THE WAKE. THE REGION WILL REMAIN AT THE SOUTHERN FRINGE OF
BROAD CLOSED LOW OVER CANADA...WITH THE SHORTWAVE ENERGY ROUNDING
THE LOW REMAINING WELL TO THE NORTH. AS SUCH...EXPECTING DRY WX
FRI AND FRI NIGHT. 12Z GFS SUGGESTING LIGHT PCPN OVER NORTHEASTERN
AREAS OF THE CWA SAT AFTN WITH A SHORTWAVE JUST TO THE NORTH. WILL
KEEP THINGS DRY FOR NOW THOUGH DURING THIS TIME WITH LACK OF SFC
FORCING CURRENTLY NOTED.

QUICK SHOT OF CAA IN THE WAKE OF THE FRONT ON FRIDAY DROP 850MB
TEMPS TO AROUND 15 DEGREES CELSIUS...RESULTING IN HIGHS GENERALLY IN
THE 80S. THE COOLER AIRMASS WILL BE SHORT LIVED AS THE HIGH BUILDS
IN...WITH 850MB TEMPS REBOUNDING BACK TO NEAR 20 DEGREES CELSIUS BY
SAT AFTN. LOWS FRIDAY NEAR NORMAL...WITH HIGHS NEARING 90 ON
SATURDAY. DEW PTS IN THE 60S SAT SHOULD KEEP HEAT INDICES WELL BELOW
ADVISORY LVLS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
QUIET WEATHER PATTERN FOR SUN INTO MON WITH HIGH PRESS DOMINATING
CONDITIONS BEHIND A COLD FRONT. THE FRONT LINGERS OFF THE DELMARVA
COAST AS IT WEAKENS... THEREFORE CANNOT RULE OUT SOME SHOWERS TO
THE SE AND E OF OUR CWA. SHORTWAVE TROUGH COULD BRING SOME AFTN
SHOWERS ON MON AND TUE... BUT CONFIDENCE WITH IT IS LOW ATTM... SO
HAVE KEPT LOW POPS. ANOTHER FRONT APPROACHES ON WED INCREASING THE
CHANCE OF SHOWERS AND TSTMS FOR THIS DAY. TEMPS WILL NEAR NORMAL
SUN AND GRADUALLY INCREASING INTO HE LOW 90S FOR WED.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR CONDS ACRS THE TERMINALS ATTM. SETUP SEEMS FVRBL FOR FOG
DVLPMNT ONCE AGN BTWN MIDNGT-DAWN. HWVR NOT AS MUCH WET GRND AS
PAST NGTS...WHICH IS COUNTERED BY HIER DEWPTS/LLVL HUMIDITY.
UNSURE EXACTLY HOW THESE TWO FACTORS WL BALANCE EACH OTHER. HV
OPTED TO KEEP PROLONGED MVFR CONDS OVNGT AT MRB...IFR AT CHO
WHERE SHRA WAS RECVD...AND ONLY BRIEF MVFR AT SUNRISE IAD/MTN. DO
NOT HV HIGH CONFIDENCE ATTM. CUD SEE FLGT CONDS WORSE THAN FCST
BUT WAS HESITANT ON OFFERING UP PROLONGED RESTRICTIONS.

FLGT RESTRICTIONS FOR THE MRNG PUSH WL ERODE BY MID MRNG. A CDFNT
WL CROSS THE TERMINALS DURING THE AFTN...AFFECTING THAT PUSH AS
WELL. SCT-NRMS SHRA/TSRA WL BE FOUND ALONG/AHD OF THE FNT. THINK
THERE WL BE SOME DIURNAL STRENGTHENING...AND AM CARRYING VCTS FOR
DC/BALT TERMINALS AS A RESULT. WUD NOT COMPLETELY RULE OUT IMPACT
AT CHO/MRB BUT PROBABILITY IS LESS. IN THE EVENT OF A DIRECT HIT
BRIEF AOB IFR CAN BE ANTICIPATED. TIMING/SPATIAL UNCERTANTIES
PRECLUDE CARRYING ANY SPECIFIC MENTION ATTM. WSHFT NEAR 18Z AT
MRB...SPREADING EAST TO 21-22Z DCA/BWI.

VFR CONDITIONS FRIDAY AND SATURDAY. WINDS GENERALLY 10 KTS OR
LESS...SHIFTING FROM THE NW FRIDAY TO A WESTERLY FLOW SAT.

&&

.MARINE...
SLY WNDS SUSTAINED 10-15 KT ATTM. HWVR...SLY CHANNELING FCST TNGT
OVER THE MD BAY/LWR PTMC. MARGINAL WINDS /MAYBE JUST SHY OF ADVY/
FCST TO CONT THRU THE DAY THU...SPCLY AHD OF CDFNT. SCA ALREADY IN
PLACE. LOOKS SOLID TNGT...AND DO NOT HV CONFIDENCE TO REMOVE IT
FOR TMRW AT THIS JUNCTURE.

BRIEF PERIOD OF SCA GUSTS EARLY FRIDAY MORNING ON THE CHESAPEAKE
BAY...WITH ALL WATERS BCMG SUB-SCA BY FRI AFT. SUB-SCA CONDITIONS
THEN LASTING INTO THE WEEKEND.

&&

.TIDES/COASTAL FLOODING...
WATER LVLS RUNNING ABT A HALF FOOT ABV ASTRO NORMALS THIS EVENING.
HWVR...THERE IS STRONG CONSENSUS AMONGST WATER LVL MODELS THAT THE
UPCOMING HIGH TIDE WL ECLIPSE THE MINOR FLOOD THRESHOLD AT
ANNAPOLIS. ONLY A SLGT INCREASE IN THE CURRENT DEPARTURE WOULD BE
SUFFICIENT TO BEAR THIS OUT. HIGH TIDE AT APAM2 AT 5AM. WL BE
AWAITING THE LATEST GUIDANCE. CONSISTENCY SUGGESTS THAT AN ADVY
MAY BE WARRANTED.

NO OTHER SITE IN JEOPARDY ATTM...ALTHO WASD2 WL GET AWFULLY CLOSE
FOR 730 AM HIGH TIDE.

THE PM TIDE WILL BE THE LOWER OF THE TWO ASTRONOMICALLY. NW WINDS
THEREAFTER SUGGEST THE UPCOMING TIDE WILL BE THE ONLY ONE TO WATCH
CLOSELY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EDT THURSDAY FOR ANZ530>534-
     537-539>541-543.

&&

$$
SYNOPSIS...LFR/HTS
NEAR TERM...HTS/LFR
SHORT TERM...SEARS
LONG TERM...IMR
AVIATION...HTS/SEARS/IMR
MARINE...HTS/SEARS/IMR
TIDES/COASTAL FLOODING...HTS


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