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Area Forecast Discussion

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FXUS61 KLWX 211859
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
259 PM EDT MON APR 21 2014

.SYNOPSIS...
HIGH PRESSURE OVERHEAD THIS AFTERNOON WILL MOVE OFFSHORE TONIGHT. A
COLD FRONT WILL PASS THROUGH THE AREA TUESDAY AFTERNOON AND
EVENING. HIGH PRESSURE RETURNS FOR WEDNESDAY AND THURSDAY BEFORE
MOVING OFF THE COAST FRIDAY. A COLD FRONT IS EXPECTED TO PASS
THROUGH THE AREA SATURDAY.

&&

.NEAR TERM /THROUGH TUESDAY/...
THE CUTOFF LOW THAT WAS PREVIOUSLY LOCATED JUST OFF THE NC COAST YDA 
HAS SLOWLY MOVED AWAY FROM THE MID-ATLANTIC COAST. ANOTHER AREA OF 
LOPRES IS LOCATED OVER SWRN ONTARIO WHILE ITS ATTENDANT COLD FRONT 
EXTENDS SW-WD INTO THE UPPER MIDWEST AND NRN PLAINS. IN BETWEEN BOTH 
LOWS...THE AXIS OF A WEAK SFC RIDGE IS LOCATED ALONG THE ERN 
SEABOARD THIS AFTN. SUBSIDENCE BENEATH SHORTWAVE RIDGING HAS 
PROVIDED WITH ABUNDANT SUNSHINE AND SEASONABLE TEMPS. 

THE ULVL RIDGE AXIS PROGRESSING DOWNSTREAM OF THE AREA WILL BE 
ACCOMPANIED BY CIRRUS OVERSPREADING THE AREA FROM WEST TO EAST THIS 
EVE. MEANWHILE...SFC LOPRES WILL STRENGTHEN WHILE MOVING EWD ACROSS 
THE NRN GREAT LAKES TNGT WHILE THE AFOREMENTIONED COLD FRONT MOVES 
EWD AND REACHES THE OH VLY LATE TNGT. RISING DEWPOINTS IN RESPONSE 
TO LGT SLY FLOW AHEAD OF THE FRONT AND INCREASING CLOUD COVER SHOULD 
BE ENOUGH TO MITIGATE CONCERNS OF ANOTHER FROST/FREEZE. FCST MIN 
TEMPS GENERALLY RANGE FROM THE MID 40S TO LOWER 50S...ALTHOUGH 
SHELTERED/RURAL LOCATIONS NORTH AND WEST OF THE CITIES MAY DIP NEAR 
40F.

12Z GUIDANCE TRENDED SLIGHTLY SLOWER WITH THE TIMING OF THE COLD 
FRONT COMPARED TO PRIOR RUNS BUT THE GENERAL THINKING STILL IS FROPA 
OCCURS DURING THE AFTN WEST OF I-95. THE COLD FRONT MAY NOT REACH 
THE CHSPK BAY UNTIL THE EVE. MODEST WAA PATTERN CONTINUES WITH SLY 
WINDS AHEAD OF THE FRONT. FCST MAX TEMPS ARE HIGHEST EAST OF THE 
BLUE RIDGE WHERE POST-FRONTAL CAA ARRIVES AFTER MAX HEATING AND 
THERE IS A BETTER CHANCE TO SEE BREAKS IN THE CLOUDS THAN IN THE 
MTS. HIGHS TUE RANGE FROM THE 60S IN THE MTS TO NEAR 80F IN THE 
CITIES AND IN CENTRAL VA. ADDED MORE DETAIL TO THE EXPECTED TIMING 
OF PRECIP WITH POPS INCREASED TO LIKELY FOR A 2-4 HR PERIOD DURING 
AND JUST PRIOR TO FROPA. KEPT SLIGHT CHANCES FOR THUNDER AS GUIDANCE 
CONSISTENT OF KEEPING THE BEST LIFT TO THE NORTH OF THE CWA WHILE 
THE BEST MOISTURE FLUX AND INSTABILITY STAYS TO OUR SOUTH. 

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
THE COLD FRONT MOVES OFF THE EAST COAST TUE NGT WHILE HIPRES BUILDS 
IN FROM THE GREAT LAKES. A STRONG PRESSURE GRADIENT BETWEEN THESE 
TWO SYSTEMS WILL PRODUCE GUSTY NW WINDS BETWEEN 20-30 MPH TUE NGT 
AND WED. DESPITE THE CAA BEHIND THE FRONT...FCST MIN TEMPS TUE NGT 
WEIGHTED TOWARD WARMER BIAS CORRECTED MET GUIDANCE AS BOUNDARY LAYER 
STAYS WELL MIXED. SUB-ZERO H8 TEMPS FCST BY 12Z GUIDANCE. THIS COLD 
AIRMASS WILL BE MODERATED BY SUNNY SKIES AND DOWNSLOPING FLOW ON 
WED. MAX TEMPS RANGE FROM THE 40S ALONG THE ALLEGHENY FRONT TO MID 
60S IN CENTRAL VA AND ALONG THE I-95 CORRIDOR.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
A DEEP RIDGE AXIS WILL TRAVERSE THE AREA THURSDAY NIGHT...WITH 
HEIGHTS FALLING AHEAD OF AN APPROACHING SHORTWAVE TROUGH FRIDAY. A 
WEAK COLD FRONT ACCOMPANYING THE APPROACHING UPPER-LEVEL TROUGH WILL 
MOVE THROUGH THE AREA ON FRIDAY BRINGING A CHANCE OF SHOWERS. THIS 
FRONT IS MORE OF A PRESSURE TROUGH/WIND SHIFT AXIS...WITH ANY 
APPRECIABLE AIRMASS CHANGE LAGGING UNTIL A SECONDARY COLD FRONT 
PASSES THROUGH THE REGION ON SATURDAY. MOISTURE LOOKS LIMITED WITH 
THE SECOND BOUNDARY...AND THAT PRECLUDES HIGHER RAIN CHANCES FOR 
MOST OR ALL OF THE AREA AT THE MOMENT.

HIGH PRESSURE AND COOLER TEMPERATURES BRIEFLY MOVE ACROSS THE AREA 
SUNDAY...BEFORE ANOTHER DISTURBANCE APPROACHES THE AREA EARLY NEXT 
WEEK.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
UNDER THE INFLUENCE OF HIPRES...VFR THIS AFTN AND TNGT WITH LGT SLY 
WINDS. A COLD FRONT MOVES THRU THE TERMINALS BETWEEN 18Z TUE THRU 
00Z WED. SHRA LIKELY WITH FROPA. FOR THE 18Z TAFS...CHANCES FOR TSRA 
TOO LOW TO INCLUDE IN 30-HR TAF SITES THIS FAR OUT. NW WINDS 
FOLLOWING THE FRONT WILL BECOME GUSTY TUE NGT AND WED AS HIPRES 
BUILDS IN FROM THE NW. GUSTS TO 30 KT POSSIBLE...ESPECIALLY AFTER A 
FEW HRS OF DAYTIME MIXING ON WED.

NW WINDS DIMINISH WED NGT AND THU WITH HIPRES BUILDING OVERHEAD.

MODERATE-HIGH CONFIDENCE IN SOUTHERLY WIND 5 TO 10 KNOTS WITH LOW 
CONFIDENCE SUB-VFR/SHOWERS FRIDAY...THEN MODERATE CONFIDENCE VFR 
WITH WESTERLY WINDS 5 TO 10 KNOTS FRIDAY NIGHT.

&&

.MARINE...
RIDGE AXIS LOCATED OVER THE MID CHSPK BAY THIS AFTN WITH LGT ELY 
WINDS TO THE NORTH AND WLY WINDS FARTHER SOUTH TOWARD TANGIER ISLAND 
AND SMITH POINT. 

SLY WINDS WILL DEVELOP TNGT AHEAD OF AN APPROACHING COLD FRONT. SLY 
FETCH WILL FAVOR CHANNELING IN THE OPEN WATERS OF THE BAY...WHICH 
WILL LIKELY ENHANCE WIND SPEEDS TO 15-20 KT SEVERAL HRS PRIOR TO 
FROPA ON TUE AFTN. SCA WAS ISSUED FOR THESE ZONES OF THE CHSPK BAY. 
SHOWERS AND POSSIBLY A FEW TSTMS TUE AFTN AND ERY EVE WITH FROPA. A 
GOOD PRESSURE SURGE BEHIND THE FRONT WILL BE ACCOMPANIED BY GUSTY NW 
WINDS TUE NGT. SCA ISSUED FOR ALL MARINE ZONES TUE NGT AND WILL 
LIKELY NEED TO BE EXTENDED INTO WED. 

THE CENTER OF HIPRES BUILDS CLOSE ENOUGH TO THE WATERS FOR WINDS 
ACROSS MOST OF THE MARINE ZONES TO SUBSIDE BELOW SCA LVLS WED EVE. 
SCA MAY NEED TO BE CONTINUED THOUGH IN SERN ZONES.

SUB SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED IN A WEAK PRESSURE 
GRADIENT REGIME TO END THE WEEK. WINDS COULD HIT SMALL CRAFT 
ADVISORY LEVELS FOR A TIME BEHIND A FRONT THIS WEEKEND.

&&

.TIDES/COASTAL FLOODING...
LGT SELY TNGT AND TUE AHEAD OF A COLD FRONT. POSITIVE TIDAL
ANOMALIES HAVE DEVELOPED TDA ALONG THE WRN SHORE OF THE MD
CHSPK BAY AS A RESULT OF LGT ONSHORE FLOW AND ARE CURRENTLY ALMOST
ONE-HALF FOOT. LATEST CBOFS GUIDANCE INDICATES ANOMALIES
INCREASING TO ABOUT ONE FOOT BY TUE MRNG. THIS WOULD KEEP TIDAL
LEVELS ABOUT ONE-QUARTER FOOT BELOW COASTAL FLOOD THRESHOLD AT
ANNAPOLIS AND GREATER THAN ONE- HALF FOOT BELOW COASTAL FLOOD
THRESHOLD AT BALTIMORE.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM TUESDAY TO 6 AM EDT WEDNESDAY 
     FOR ANZ530-531-535>539-542.
     SMALL CRAFT ADVISORY FROM NOON TUESDAY TO 6 AM EDT WEDNESDAY 
     FOR ANZ532>534-540-541-543.

&&

$$
SYNOPSIS...JRK
NEAR TERM...JRK
SHORT TERM...JRK
LONG TERM...DFH
AVIATION...JRK/DFH
MARINE...JRK/DFH
TIDES/COASTAL FLOODING...JRK






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