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Area Forecast Discussion

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FXUS61 KLWX 202122
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
522 PM EDT SUN APR 20 2014

.SYNOPSIS...
HIGH PRESSURE OVER EASTERN NEW ENGLAND WILL BUILD INTO THE AREA
TONIGHT AND MONDAY. A COLD FRONT WILL MOVE THROUGH THE AREA
TUESDAY AND TUESDAY EVENING. HIGH PRESSURE BUILDS BACK IN FOR THE
SECOND HALF OF THE WORK WEEK.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
AXIS OF SURFACE HIGH HAS MOVED SOUTH OF LONG ISLAND AND ACRS CAPE
COD. IT WILL WEAKEN AND PUSH INTO THE MID ATLANTIC OVERNIGHT.
ALOFT...A RDG AXIS IS ALSO SETTING UP...WITH WL AIDE IN
COOLER/DRIER AIR DRAINING SWWD. WHILE DEWPTS IN THE LWR-MID 30S
LCLLY /UPR 20S FOR SOME SITES IN THE APLCNS AND SHEN VLY/...
WIDESPREAD MID-UPR 20S DEWPTS PRESENT ACRS NJ/ERN PA. THUS...PTTN
IN PLACE FOR WINDS TO DECOUPLE OVERNIGHT RESULTING IN GOOD
RADIATIONAL COOLING. BASED ON THIS...MIN-T ADJUSTED A LTL. MOST
SUSCEPTIBLE WAS NERN MD...WHICH IS NEARER THE RDG AND THUS
POSITIONED TO RECEIVE SOME OF THE BETTER RADL COOLING. THAT MAKES
PATCHY FROST A CONSIDERATION. HV OPTED TO RAISE A FROST ADVY FOR
NERN MD FROM FDK-HARFORD AT THIS TIME. WL ALSO NEED TO MONITOR
LOUDOUN-MONTCO-HOWARD TO SEE HOW THEY RESPOND. IF LWR DEWPTS DO
INDEED DRAIN SWD AND TEMPS START PLUMMETING...THEN THE ADVY MAY
NEED TO BE XPNDD SWD.

BY MONDAY AFTERNOON AND NIGHT SURFACE LOW PRESSURE MOVES INTO THE
GREAT LAKE STATES AND A COLD FRONT BEGINS TO APPROACH THE AREA.
MODELS KEEP SUNSHINE IN PLACE FOR MOST OF TOMORROW BEFORE HI
CLOUDS INCREASE LATE IN THE DAY AND NIGHT. LIGHT SOUTHERLY WINDS
DEVELOP BUT DRY AIR REMAINS IN PLACE FOR MUCH OF THE DAY. WOULD
EXPECT TEMPERATURES TO BE A BIT WARMER WITH HIGHS IN THE UPPER
50/S TO UPPER 60/S...AND IT WILL FEEL MILDER WITH LESS WIND. MIN
TEMPS MON NGT IN THE MID 40S TO LOWER 50S.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
SUB-1000 MB SFC LOW TRACKS EWD ACROSS UPSTATE NY AND NRN NEW ENGLAND 
ON TUE. ATTENDANT COLD FRONT OVER THE OH VLY IS EXPECTED TO CROSS 
THE APPALACHIANS BY ABOUT 18Z TUE BEFORE MOVING EWD THRU THE CWA 
BETWEEN APPROX 18Z TUE AND 00Z WED. THE BEST FORCING LOOKS TO STAY 
NORTH OF CWA AND CLOSER TO TO SFC LOW AND UPPER SHORTWAVE TROUGH. 
PREVIOUS FCST HAD LIKELY POPS WITH FROPA. DID NOT WANT TO INCREASE 
POPS FURTHER DUE TO THE LIMITED FORCING AND PROGRESSIVE NATURE WITH 
THIS SYSTEM. THUNDER A POSSIBILITY WITH TIMING OF FROPA COINCIDENT 
WITH PEAK HEATING. WEAK MID-LVL LAPSE RATES AND INCREASING CLOUD 
COVER AHEAD OF THE FRONT DURING THE MRNG SHOULD LIMIT DEGREE OF 
DESTABILIZATION. FCST MEAN MLCAPE VALUES FROM THE 09Z SREF ARE UNDER 
500 J/KG FOR THE ENTIRE CWA AND MLCAPE PROBABILITIES AOA 500 J/KG 
ARE LOW...JUST TWO INDICATIONS OF A VERY LIMITED TSTM POTENTIAL. 
EVEN WITH CLOUD COVER...MAX TEMPS IN THE 70S AHEAD OF THE FRONT. 

THE COLD FRONT MOVES OFF THE DELMARVA COAST TUE NGT WHILE HIPRES 
BUILDS IN FROM CENTRAL CANADA. A STRONG PRESSURE GRADIENT BETWEEN 
THESE TWO SYSTEMS WILL PRODUCE BREEZY NW WINDS TUE NGT AND 
CONTINUING INTO WED. 12Z NAM/GFS BUFKIT PROFILES SHOW A POTENTIAL 
FOR WIND GUSTS OF 30-35 MPH TO MIX DOWN THE SFC ON WED. MAX TEMPS A 
FEW DEGREES BELOW NORMAL ON WED OWING TO THE CAA IN WAKE OF FROPA.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
SURFACE HIGH BUILDING ACROSS AREA WEDNESDAY NIGHT. TEMPERATURES MAY 
DROP 5 DEGREES BELOW NORMAL BEFORE REBOUNDING THROUGH THURSDAY
NIGHT. 

HIGH PRESSURE MOVING OFFSHORE FRIDAY EVENING AND NIGHT AS COLD
FRONT FROM CENTRAL PLAINS TRACK EAST ACROSS GREAT LAKES/OHIO
VALLEY. MARGINALLY SUPPORT FOR PRECIPITATION WITH THE FRONT AS
MAIN AREA PVA IS NORTH OF AREA. INCREASED CHANCES OF PRECIPITATION
SATURDAY MORNING WHEN A SECOND FRONT SUPPORTED BY STRONG PVA
ENTERS THE AREA FROM THE NORTH.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
VFR SKC-SCT/BKN250 THRU MONDAY AFTERNOON AT THE TERMINALS. EAST 
SURFACE WINDS 10-15KT WILL SUBSIDE AT SUNSET THIS EVENING THEN SHIFT 
TO THE SOUTH BUT LESS THAN 10KT MONDAY. INCREASING HI CLOUDS LATE 
MONDAY. 

A COLD FRONT IS ANTICIPATED TO MOVE THRU THE TERMINALS FROM WEST TO 
EAST BETWEEN 18Z TUE AND 00Z WED. SHRA LIKELY AND ISO TSRA DURING 
THE AFTN WITH FROPA. BRIEF/LOCAL RESTRICTIONS POSSIBLE WITH HEAVIER 
SHRA OR TSRA. SLY WINDS AROUND 10 KT AHEAD OF THE FRONT WILL BECOME 
NWLY 10-15 KT FOLLOWING FROPA. WIND GUSTS UP TO 30 KT POSSIBLE ON 
WED AS HIPRES BUILDS IN FROM THE NW.

VFR WITH HIPRES OVERHEAD WED NGT THRU FRI.

&&

.MARINE...
FOR THE MOST PART...WNDS SUBSIDING BLO SCA THRESHOLDS ATTM. THE
EXCEPTION TO THIS REMAINS THE MAIN CHANNEL OF THE BAY BELOW BALT
HARBOR...AND MORE PERSISTENTLY THE BAY FROM DRUM PT-SMITH PT INCL
THE MOUTH OF THE PTMC/TANGIER SOUND. IN THESE AREAS...WNDS STILL
FUNNELED IN A SLIGHTLY TIGHTER P-GRAD BTWN HIPRES OVER FAR ERN NEW
ENGLAND AND LOPRES OFF THE CAROLINAS. THE GRADIENT WL BE THERE
MOST OF TNGT. FURTHER...MDL GDNC SUGGESTING THAT THE MIXED LYR
MAY TAP INTO THESE WNDS THRU AT LEAST THE EVNG. HV XTNDD SCA PAST
MIDNGT FOR THESE 3 SRNMOST MARINE ZNS.

WINDS WILL BE LIGHT/VRBL MON-MON NGT IN RESPONSE TO RDG AXIS.

SLY FLOW AHEAD OF A COLD FRONT GENERALLY 10 KT ON TUE. THERE IS A 
LIMITED POTENTIAL HOWEVER FOR WINDS TO REACH SCA CRITERIA IN THE 
MAIN STEM OF THE CHSPK BAY DUE TO SLY CHANNELING. CAPPED WINDS AT 15 
KT IN THESE ZONES FOR NOW WITH SUCH A MARGINAL WIND FIELD. SHRA AND 
POSSIBLY AN ISO TSTMS WITH THE FROPA LATE TUE AFTN AND EVE. NW WINDS 
BEHIND THE FRONT WILL BECOME GUSTY AS HIPRES BUILDS IN FROM THE NW. 
SCA LIKELY TUE NGT AND WED.

WINDS BELOW SCA LVLS BY WED NGT AS HIPRES BUILDS OVERHEAD.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR MDZ004>007.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR 
     ANZ531>533-536-541-542.
     SMALL CRAFT ADVISORY UNTIL 1 AM EDT MONDAY FOR ANZ534-537-543.

&&

$$
SYNOPSIS...HTS/JRK
NEAR TERM...HTS/SDG
SHORT TERM...JRK
LONG TERM...CEM
AVIATION...SDG/JRK/CEM
MARINE...HTS/JRK/CEM






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