Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 241030 AAA
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
630 AM EDT WED SEP 24 2014

.SYNOPSIS...
HIGH PRESSURE WILL EXIT OFF THE NEW ENGLAND COAST TODAY...AS LOW
PRESSURE APPROACHES FROM THE ATLANTIC COAST. THIS SYSTEM WILL MOVE
ALONG THE ATLANTIC COASTLINE...ACROSS THE MID-ATLANTIC REGION AND
THEN OFF THE COAST INTO EARLY THURSDAY. HIGH PRESSURE IS ON TAP
FOR THIS WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
HEADLINE UPDATE...ADDED THE MIDDLE PORTIONS OF THE MD CHES BAY TO
THE CURRENT SCA. HIGHER GUSTS ARE BEGINNING TO SPREAD FURTHER NWD
AHEAD OF THE APPROACHING LOW PRES SYSTEM.

A FLOOD WATCH IS IN EFFECT FOR MUCH OF THE WASHINGTON AND
BALTIMORE METRO AREAS FROM THIS EVENING THRU THE OVERNIGHT HOURS
TONIGHT. SEE HYDROLOGY SECTION BELOW FOR FURTHER DETAILS.

THE LOW PRES SYSTEM OVER THE SRN ATLC STATES IS STILL GEARING UP
TO MAKE ITS NWD JOG BUT WILL FIND IN THE COMING HRS A FAIRLY OPEN
PATH DUE NORTH FROM THE CAROLINAS. HIGH PRESSURE THAT HAS GIVEN
OUR AREA A VERY FALL-LIKE START TO THE SEASON WILL ROLL OFF THE
NEW ENGLAND COAST...OPENING UP THE PATH FOR THE LOW TO TRACK UP
ACROSS THE I-95 CORRIDOR. A CUT-OFF UPPER LOW POWERING THE SYSTEM
WILL REMAIN ON THE WRN FRINGE OF THE SFC SYSTEM...ALSO DRIFTING
NWD UP THE SPINE OF THE APLCNS.

LIGHT SHOWERS ARE ALREADY SPREADING UP ACROSS SERN VA...LARGELY
DISSIPATING UPON ARRIVING TO THE SRN CWA BORDER. THIS WILL
CONTINUE INTO THE MID MRNG HRS...WHEN MORE OF THE DRY BOUNDARY
LAYER BECOMES SATURATED. THE 00Z KRNK SOUNDING SHOWS A VERY DRY
LEVEL BETWEEN 600-850MB...ESSENTIALLY DRYING OUT THE INCOMING
ACTIVITY. THIS DRY POCKET WILL MOVE ITS WAY UP ACROSS OUR REGION
OVER THE NEXT SEVERAL HRS...PREVENTING MUCH PRECIP FROM AFFECTING
THE AREA FOR THE FIRST HALF OF THE DAY BUT WILL EVENTUALLY BE
OVERCOME LATER THIS AFTN. MORE STEADY SHOWERS WILL BEGIN TO ARRIVE
OVER SRN MD AND NRN VA INTO THE LATE AFTN HRS...THEN ON TOWARD THE
METRO AREAS AND JUST INTO THE SHEN VLY LATER THIS EVE.

THE HEAVIER ACTIVITY IS EXPECTED TO BEGIN LATE TONIGHT...AFTER
SUNSET AND INTO THE EARLY MRNG HRS. POCKETS OF EMBEDDED HEAVY RAIN
WILL FORM ALONG CONFINED REGIONS OF STRONG LIFT...LIKE WHAT IS
OCCURRING OVER THE NC OUTER BANKS ATTM. BREEZY WINDS WILL ALSO
BEGIN TO ARRIVE INTO THE EARLY MRNG HRS...SURROUNDING THE INCOMING
SFC LOW. THE LOW ITSELF WILL STAY MAINLY TO OUR SOUTH AND
EAST...BUT THE STRONGEST WINDS AND HEAVIEST RAIN WILL BE STATIONED
ALONG AN EAST/WEST AXIS JUST NORTH OF THE LOW AND W/ THE NOSE OF
IT POKING INTO THE CWA FROM DELMARVA. THE TIMING OF ALL OF THIS
HAS BECOME PROGRESSIVELY SLOWER W/ RECENT NAM/EURO RUNS WHICH HAVE
BEEN THE MOST CONSISTENT AND PERSISTENT W/ THE DEPICTION OF THE
LOW`S TRACK/INTENSITY.

&&

.SHORT TERM /THURSDAY/...
AS THE LOW BEGINS TO DRIFT BACK OFF THE DELMARVA COAST INTO
THU...WINDS WILL DROP OFF WHILE TURNING NELY. THIS WILL BEGIN TO
DISSIPATE THE LEFTOVER PRECIP - THOUGH THE DENSE LOW CLOUDS WILL
STICK AROUND FOR MUCH OF THE DAY. HIGH PRESSURE WILL PROVIDE
GOOD SUBSIDENCE IN THE WESTERN HALF OF THE REGION.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
UPPER TROUGH/LOW PRESSURE WILL GRADUALLY PULL AWAY FROM THE MIDDLE
ATLANTIC REGION THURSDAY NIGHT AND THE FIRST PART OF FRIDAY. STEADY
RAIN IS EXPECTED TO END BY THURSDAY NIGHT BUT A FEW LINGERING
SHOWERS COULD STILL HOLD ON FROM THE BALTIMORE METRO AREA AND POINTS
NORTH INTO EARLY FRIDAY. IF THE SYSTEM SLOWS DOWN OR UPPER ENERGY
HANGS BACK LONGER FUTURE SHIFTS MAY NEED TO EXTEND POPS FURTHER OUT
IN TIME.

HIGH PRESSURE WILL BUILD INTO THE MIDDLE ATLANTIC REGION LATER
FRIDAY AND REMAIN IN PLACE THROUGHOUT THE UPCOMING WEEKEND.
TEMPERATURES ARE EXPECTED TO MODERATE BACK INTO THE MIDDLE TO UPPER
70S WITH LOWS GENERALLY RUNNING IN THE 40S WEST TO 50S TO NEAR 60
EAST. THE NEXT TROUGH OF LOW PRESSURE COULD APPROACH THE MIDDLE
ATLANTIC LATE MONDAY OR TUESDAY OF NEXT WEEK BRINGING INCREASING
CLOUDS AND A CHANCE FOR SHOWERS.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDS EARLY THIS MRNG AND INTO THE AFTN HRS. LOWER CIGS AND
SHOWERS WILL ARRIVE LATE THIS EVE ACROSS MUCH OF THE AREA.

SUB VFR CIGS AND RESTRICTED VSBYS IN LIGHT RAIN/SHOWERS WILL LINGER
INTO THURSDAY NIGHT. CONDITIONS ARE EXPECTED TO IMPROVE BY FRIDAY
AND VFR CONDITIONS ARE EXPECTED SATURDAY THROUGH MONDAY. THE NEXT
LOW PRESSURE SYSTEM COULD BRING A CHANCE FOR SHOWERS AND LOWERED
CIGS BY LATE MONDAY INTO TUESDAY OF NEXT WEEK.

&&

.MARINE...
WINDS HAVE ALREADY BEEN GUSTY OVER THE SRN MD BAY...SO A SCA IS IN
EFFECT FOR THESE AREAS THRU MID-MRNG. WINDS WILL INCREASE OVER THE
REMAINDER OF THE AREA WATERS LATER THIS AFTN...AS LOW PRESSURE
APPROACHES FROM THE SOUTH.

SCA BEGINS 10 AM WEDNESDAY FOR ALL THE WATERS AND CONTINUES INTO
THE OVERNIGHT HRS WHILE THE LOW IS APPROACHING AND PASSING BY JUST
TO THE SE OF THE BAY. PERIODS OF RAIN LATE THIS AFTN/EVE.

SCA CONDITIONS WILL GRADUALLY DIMINISH THURSDAY NIGHT. HIGH PRESSURE
WILL BUILD OVER THE WATERS LATER FRIDAY AND CONTINUE INTO MONDAY OF
NEXT WEEK. DURING THIS TIME...WINDS ARE EXPECTED TO REMAIN BELOW SCA
LEVELS.

&&

.HYDROLOGY...
EURO/NAM NEAR-TERM GUIDANCE CONTINUE TO SHOW THE ERN...AND
PARTICULARLY THE EXTREME NERN SECTIONS OF THE AREA UNDER THE BEST
COMBINATION OF THE MOISTURE...LIFT AND SHEAR FOR PERSISTENT
MODERATE TO HEAVY RAIN. MOISTURE-RICH AIR WILL BE LOCALIZED TO THE
AXIS OF HIGHEST LIFT ALONG/NEAR THE COASTLINE. NAM 250MB WINDS
SHOW A NORTH/SOUTH UPPER JET DIRECTLY OVER THE ERN HALF OF THE CWA
FOR GOOD UPPER DIVERGENCE. MORE IMPRESSIVE IS THE EXPECTED LOW
LEVEL JET MAX W/ A DUE ELY ONSHORE FLOW OVERNIGHT THAT CREATES A
THIN BUT PRONOUNCED AXIS. A SOLID 1-2 INCHES POSSIBLE ALONG THE
WRN SHORE COUNTIES OF THE BAY - STORM-TOTAL - INTO EARLY
THU...LOCALLY HIGHER. THESE AMOUNTS WILL TAPER OFF TO THE
WEST...ALSO W/ LOCALLY HIGHER AMOUNTS EXPECTED.

&&

.TIDES/COASTAL FLOODING...
CURRENT WATER LEVELS ARE RIGHT AT OR JUST BELOW NORMAL...BUT ARE
THERE BECAUSE THEY HAVE BEEN RISING FROM OVER A HALF-FOOT BELOW
NORMAL OVER A DAY AGO. A SLOW/STEADY INCREASE WILL CONTINUE THRU
THE DAY TODAY...THOUGH MINOR FLOODING NOT ANTICIPATED FOR UPCOMING
H.T. CYCLE. WINDS WILL INCREASE LATER THIS AFTN/EVE AHEAD OF A
STRENGTHENING LOW PRES SYSTEM TO OUR SOUTH.

STEADY 15-25KT WINDS WILL THEN QUICKLY INCREASE WATER LEVELS
ALONG THE MD CHES BAY WRN SHORE LOCALES. THE POTENTIAL FOR MINOR
CF WILL INCREASE SHARPLY WHERE THE ELY WINDS BANK UP
STRONGEST/LONGEST LATE TONIGHT. AS THE LOW DRIFTS NE OF THE AREA
ON THU...THE WIND FIELD WILL TURN MORE NLY AND ALLOW WATER TO PUSH
BACK DOWN THE BAY AND DECREASE FLOODING POTENTIAL OVER THE COURSE
OF THE DAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT
     FOR DCZ001.
MD...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT
     FOR MDZ006-007-009>011-013-014.
VA...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT
     FOR VAZ053-054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 AM EDT
     THURSDAY FOR ANZ535-536.
     SMALL CRAFT ADVISORY UNTIL 2 PM EDT THURSDAY FOR ANZ532-540.
     SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ533-534-
     537-541>543.
     SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 2 PM EDT
     THURSDAY FOR ANZ530-531-538-539.

&&

$$
UPDATE...GMS
PREV DISCUSSION...GMS/KRW





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