Dense Fog in Virginia, May 29, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
441 AM EDT FRI MAY 29 2015

.SYNOPSIS...
HIGH PRESSURE OVER LAKE ONTARIO WILL SHIFT SOUTHEAST AND
REINFORCE HIGH PRESSURE OFFSHORE TODAY. SOUTHERLY WINDS WILL
CONTINUE TO BRING WARM AND HUMID CONDITIONS TO THE MID- ATLANTIC
THROUGH SATURDAY. A COLD FRONT WILL ARRIVE SUNDAY AND STALL OVER
THE AREA THROUGH MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
06Z SFC ANALYSIS INDICATING FRONTAL BOUNDARY REMAINS STRETCHED
ACROSS THE NORTHERN PORTION OF THE CWA...NEAR THE MASON DIXON
LINE. THIS BOUNDARY CONTINUES TO BE A TRIGGER POINT FOR ISO
ACTIVITY...MAINLY EAST OF THE BLUE RIDGE. MESO MODELS HINTING THAT
THESE SHOWERS AND TSTMS SHOULD DIMINISH BY DAYBREAK AND AS SUCH
WILL CARRY ISO POPS THRU 12Z. WITH SKIES SCATTERING OUT OVER MUCH
OF THE AREA...COMBINING WITH DECENT LOW LVL MOISTURE...EXPECTING
AT LEAST PATCHY FOG DEVELOPMENT THRU DAYBREAK AS WELL.

FOR TODAY...YET ANOTHER DAY OF HOT...HUMID AND SCT SHOWERS AND
TSTMS. NEAR STATIONARY FRONT WEAKENS BY THIS AFTN...WITH HIGH
PRESSURE BUILDING IN AT THE SFC AND UPPER LVL RIDGING PERSISTING.
ISO SHOWERS AND MAYBE AN ISO TSTM PSBL ALONG THIS BOUNDARY MIDDAY AS
SBCAPE REACHES 500-100 J/KG. HOWEVER...WITH LACK OF FORCING
ALOFT...AND THE LOSS OF THE FRONT BY THIS AFTN...EXPECTING THE
ACTIVITY TO TRANSITION MORE ALONG AND WEST OF THE BLUE
RIDGE...OCCURRING WITH THE COMBO OF DECENT INSTABILITY AND TERRAIN
CIRCULATIONS OFF THE SELY FLOW. WEAK SHEAR SHOULD MINIMIZE ANY
THREAT OF STRONGER STORMS. HAVE ONLY SLIGHT CHC POPS IN FOR THE
WESTERN AREAS TONIGHT WITH DCRSNG INSTABILITY...THOUGH A PASSING
WEAK SHORTWAVE COULD TRIGGER AN ISO SHOWER.

AS HAS BEEN THE STORY ALL WEEK...TEMPS WELL ABV NORMAL. MUCH OF THE
AREA WILL SEE 80S TODAY...WITH ISO SPOTS POSSIBLY REACHING 90 IN THE
PIEDMONT. MILD NIGHT TONIGHT WITH LOWS IN THE 60S.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
ANOTHER DAY OF WARM CONDITIONS SATURDAY AS THE REGION REMAINS
POSITIONED BETWEEN HIGH PRESSURE OFFSHORE AND A COLD FRONT SLOWLY
APPROACHING FROM THE WEST. WILL BEGIN TO SEE HEIGHT FALLS DURING
THE DAY SAT AS UPPER LVL RIDGE MOVES EAST AHEAD OF AN APPROACHING
UPPER LVL TROUGH. WHILE INSTABILITY VALUES NOT AS STRONG AS DURING
THE WORK WEEK...STILL EXPECTING ENOUGH OF AN UNSTABLE AIRMASS FOR
TSTM DEVELOPMENT MAINLY WEST OF THE BLUE RIDGE AND UP ALONG THE
MASON- DIXON LINE...ESP MIDDAY WITH A WEAK SHORTWAVE PASSING ALONG
THE PA/VA BORDER. HAVE CAPPED AT HIGH END CHC (SCT) POPS FOR NOW.

PRE FRONTAL SFC TROUGH WILL KEEP THE CHC FOR PCPN ONGOING SAT
EVENING...WITH THE FRONT THEN NEARING THE WESTERN AREAS BY SAT
MORNING. WILL MAINTAIN POPS OVERNIGHT...THOUGH THINKING ONLY A
SLIGHT CHC OF OCCURRING.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
CDFNT WL MV THRU DURING THE DAY SUN. ALTHO INSTBY WL BE
RESPECTABLE...ITS ALSO NOT EXTREME. BAROCLINICITY...DROPPING HGTS
AND DAYTIME HEATING WL ALL ASSIST IN TSRA DVLPMNT. ENVIRONMENT MAY
SUPPORT A FEW STRONGER STORMS. WUD THINK THAT WIND MAY BE THE BIGGER
THREAT...ALTHO MATURE STORMS CUD DROP A LTL HAIL TOO. AND...HAS BEEN
THE CASE FOR SVRL DAYS NOW...HIGH PWATS WL YIELD HVY RAINERS.

GDNC COMING INTO CONSENSUS THAT SFC FNT WL MAKE IT THRU...WHICH WL
ALLOW A COOLER AMS TO INFILTRATE THE RGN. HWVR...H8 WAA WL BE DVLPG
ALMOST RIGHT AWAY. SINCE AREA WL BE W/IN FRNTL ZONE...AN OVERRUNNING
PTTN WL SET UP...WHICH SPELLS A PD OF WET WX MON-MON NGT...AND
PERHAPS INTO TUE. CLD GRIDS STAY RATHER...WHICH ADDS CONFIDENCE IN
KEEPING MAXT IN THE 60S.

CNDN HIPRES WL EVENTUALLY WIN OUT BY MIDWEEK. TEMPS WL MODERATE WED-
THU AS PCPN CHCS DECREASE AND CLDS THIN. CONUS UPA PTTN WL STILL BE
QUIT AMPLIFIED...WHICH DOES SUPPORT CLDS SPILLING INTO AREA...AND
PERHAPS EVEN A FEW SHRA ON THE PERIPHERY OF RDG /SRN-WRN CNTYS/.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
GENERALLY VFR CONDITIONS THRU THE TAF PERIOD. PSBL FOG DEVELOPMENT
THIS MORNING KIAD/KCHO/KMRB SO WILL KEEP VIS 3-5SM IN. ANY FOG
WILL DISSIPATE BY 13Z. SCT SHOWERS AND TSTMS THIS AFTN...WITH
HIGHER CONFIDENCE OF OCCURRING KCHO/KMRB. WILL INCLUDE AS
PREVAILING GROUP...WITH VCTS MENTION AT KIAD. LOW CONFIDENCE OF
HAPPENING AT THE EASTERN THREE SITES...SO WILL HOLD OFF FOR NOW
UNTIL CONFIDENCE INCREASES. LIGHT AND VRB WINDS WILL INCREASE
AROUND 5 KTS FROM THE EAST BY 12Z...THEN BACK TO THE SE TO 10 KTS
DURING THE DAY TODAY.

SLY FLOW SETS UP TONIGHT THRU SAT NIGHT. INCRSG WINDS ON SAT WITH
PSBL GUSTS UP TO 20 KTS DURING THE DAY. ANOTHER ROUND OF SHOWERS AND
TSTMS PSBL AT MAINLY KMRB...WITH VERY LOW CONFIDENCE OF REACHING ANY
OTHER SITES SAT-SAT NIGHT.

TSRA SHUD BE NMRS SUN AS CDFNT DROPS THRU. WHILE XPCT PDS OF
VFR...PDS OF FLGT RESTRICTIONS LKLY...W/ LCL AOB IFR PSBL W/IN
STORMS. THIS WL CONT INTO SUN EVE.

FLOW WL TURN NLY MON...BUT UNSETTLED CONDS XPCTD MON-MON NGT. SINCE
FLOW WL BE ONSHORE /ENELY/ IN A MUCH COOLER AMS...WUD BE WARY OF LWR
CLDS AND PDS OF FOG IN ADDITION TO SHRA...OR MAYBE EVEN DZ. GRDL
IMPRVMNT XPCT TUE.

&&

.MARINE...
SUB-SCA CONDITIONS ON ALL THE WATERS THRU THIS MORNING. PSBL SLY
CHANNELING COULD RESULT IN GUSTS REACHING 18 KTS THIS AFTN ON THE
CHESAPEAKE BAY. CONFIDENCE TOO LOW TO ISSUE SCA AT THIS TIME. WILL
BE ISSUING SCA FOR SAT FOR THE CHESAPEAKE BAY WITH GUSTS UP TO 20
KTS PSBL ON THE SLY FLOW. THE SCA CONDITIONS WILL CONTINUE THRU
SAT NIGHT.

CFP SUNDAY. STRONG STORMS MAY BE DVLPG ALONG/AHD OF FNT...WHICH WUD
POSE A WIND THREAT. WUD ANTICIPATE SMW/S. ONCE FNT MAKES IT THRU...
WINDS INCR IN NELY FLOW...WHICH WUD BE ON SUN NGT. SCA PSBL AT THAT
TIME. NELY/ENELY FLOW WL CONT INTO TUE...BUT AT SPDS BLO CRITICAL
THRESHOLDS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 1 AM EDT SUNDAY FOR
     ANZ530-538>542.
     SMALL CRAFT ADVISORY FROM 10 AM SATURDAY TO 8 AM EDT SUNDAY
     FOR ANZ532>534-543.
     SMALL CRAFT ADVISORY FROM 10 AM SATURDAY TO 6 AM EDT SUNDAY
     FOR ANZ531.
     SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 2 AM EDT SUNDAY FOR
     ANZ537.

&&

SYNOPSIS...HTS
NEAR TERM...SEARS
SHORT TERM...SEARS
LONG TERM...HTS
AVIATION...SEARS/HTS
MARINE...SEARS/HTS