Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 250341
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1041 PM EST SAT JAN 24 2015

.SYNOPSIS...
HIGH PRESSURE BUILDS IN BRIEFLY SUNDAY. LOW PRESSURE WILL PASS
SOUTH OF THE AREA SUNDAY NIGHT...THEN STRENGTHEN AS IT MOVES UP
THE COAST MONDAY AND TUESDAY. HIGH PRESSURE IS THEN EXPECTED
THROUGH MIDWEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS MENTIONED IN PREVIOUS DISCUSSION...RADAR ACRS WRN PA/WVA HV
STARTED TO FILL IN SLGTLY. UNFORTUNATELY UPSTREAM OBS INDICATE
FZDZ...NOT SHSN...AND THIS ACTIVITY HEADING TWD THE WRN SLOPES. A
CHGOVER TO SHSN DOES NOT SEEM EVIDENT. THEREFORE...HV ISSUED
FREEZING RAIN ADVY FOR THE OVNGT HRS. REST OF FCST REMAINS THE
SAME. PREV DISCUSSION FOLLOWS...

CWFA IN NW FLOW THIS EVNG. SFC RDGG RESIDES IN/NW OF OHVLY. HV HAD
A FEW HIER WND GUSTS PAST CPL HRS...REFLECTIVE OF A WEAK VORT
EMBEDDED W/IN THE MEAN FLOW. MDL SNDGS SUGGEST THAT SFC WNDS SHUD
DECOUPLE SOMEWHAT...WHILE WINDS REMAIN BRISK BTWN 1-5 KFT. HV HIER
WINDS ACRS THE RIDGETOPS.

CLDS ACRS THE APLCNS HV BEEN CREEPING TWD THE BLURDG. WHILE
BELIEVE THAT PCPN WL BE HELD BACK BY THE APLCNS...MEAN LYR RH DOES
INCREASE THRU MRNG. MADE SUBTLE CLDCVR ADJUSTMENTS. CLDS AND WINDS
SUGGEST THAT TEMPS WL HV TROUBLE FALLING MUCH. HV LEFT PRVS MIN-T
FCST AS IS.

FOR SUNDAY...DRY EVERYWHERE IN THE MORNING EXCEPT AGAIN THE
ALLEGHENY FRONT WHICH WILL HAVE SCT SNOW SHOWERS. HEADING INTO THE
AFTN...ATTENTION WILL BE TURNED TO THE APPROACHING CLIPPER SYSTEM AS
IT DIPS SOUTH THROUGH THE GREAT LAKES WITH IT NEARING KENTUCKY BY
00Z MONDAY. UPPER LVL ENERGY NUDGING AHEAD OF THE APPROACHING
ASSOCIATED CLOSED LOW COULD BRING LIGHT PCPN TO AREAS WEST OF THE
BLUE RIDGE AND ALONG THE MASON DIXON LINE SUN AFTN...BUT THE BULK OF
THE PCPN FOR MOST OF THE AREA LOOKS TO HOLD OFF UNTIL AFTER 00Z MON.
TEMPS WARMING INTO THE 40S COULD RESULT IN THE LIGHT PCPN BEING A
RAIN/SNOW MIX OR EVEN ALL RAIN. AT THE MOMENT NOT ANTICIPATING
ACCUMULATING SNOWS OUTSIDE THE POTOMAC HIGHLANDS/ALLEGHENY REGION
UNTIL SUNDAY EVENING.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
CLIPPER LOW PRESSURE SYSTEM WILL REACH THE CENTRAL OHIO VALLEY BY
SUNDAY EVENING...AND NEARLY VERTICALLY STACKED WITH AN UPPER LOW.
12Z ECMWF/GFS/NAM ALL IN AGREEMENT OVERALL SYNOPTIC SCENARIO. BOTH THE
UPPER TROUGH AND SURFACE LOW WILL TRACK SEWD INTO THE CAROLINAS
SUNDAY NIGHT. ASSOCIATED PRECIPITATION WILL SPREAD ACROSS THE AREA
DURING THE EVENING AND OVERNIGHT HOURS. TEMP GUIDANCE IS A FEW
DEGREES WARMER THAN PREVIOUS RUNS. THIS WILL RESULT IN SOME AREAS
STARTING WITH RAIN OR A RAIN/SNOW MIX BEFORE CHANGING OVER TO SNOW
SUNDAY NIGHT...INCLUDING THE SOUTHERN TIER COUNTIES OF MARYLAND
AND VIRGINIA...UP TO THE WASHINGTON DC METRO. ALTHOUGH MODELS ARE
CONSISTENT WITH GENERAL FEATURES...THERE ARE STILL SPECIFIC
DIFFERENCES REGARDING BANDING AND LOCALLY HIGHER QPF AMOUNTS. A
WINTER STORM WATCH HAS BEEN ISSUED STARTING SUNDAY EVENING FOR THE
NORTHWESTERN PORTION OF THE CWA...INCLUDING SEVERAL COUNTIES IN
WV...WESTERN AND NORTH CENTRAL MD...AND WESTERN LOUDOUN...CLARK
AND FREDERICK COUNTIES IN VA. LOW TEMPS RANGE FROM THE UPPER 20S
IN THE WATCH AREA AND THE POTOMAC HIGHLANDS TO THE THE LOW 30S
ACROSS THE PIEDMONT AND SRN MD.

ON MONDAY...ENERGY TRANSFERS FROM THE CAROLINAS TO THE OFFSHORE
WATERS...WITH RAPID CYCLOGENESIS TAKING PLACE EAST OF NORFOLK.
THIS WILL CONTINUE TO DRAW MOISTURE INTO THE REGION ALONG WITH
COLD AIR FROM THE NORTH. SNOW WILL CONTINUE...ALTHOUGH LIKELY
TRENDING LIGHTER DURING THE DAY AS MOST ENERGY TRANSFERS EWD
TOWARDS THE OFFSHORE LOW. FOR THE BALTIMORE/WASHINGTON METROS...
EXPECTING AN ADVISORY LEVEL SNOW OF AROUND 2-4 INCHES. SIMILAR
AMOUNTS EXPECTED OVER SOUTHERN PORTIONS OF THE SHENANDOAH VALLEY...
BLUE RIDGE AND THE PIEDMONT..WITH LESSER AMOUNTS TO THE SOUTH.
WITH THE FORECAST ADVISORY-LEVEL SNOWFALL...HAVE NOT ISSUED A
WINTER STORM WATCH FOR THESE AREAS. CERTAINLY HEADLINES WILL BE
REFINED AS THE EVENT DRAWS CLOSER.

SYSTEM PULLS OUT MONDAY NIGHT. LOWS DROP INTO THE 20S ACROSS THE CWA.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
ANOTHER PIECE OF ENERGY BEHIND THE DEPARTING ALBERTA CLIPPER WILL
ALLOW FOR THE OPPORTUNITY OF ADDITIONAL SNOW SHOWERS TUESDAY. SOME
UPSLOPE SNOW SHOWERS MAY STILL LINGER IN THE POTOMAC HIGHLANDS
TUESDAY NIGHT WHILE HIGH PRESSURE INFLUENCES DRY CONDITIONS
ELSEWHERE. TEMPERATURES TUESDAY AND TUESDAY NIGHT WILL BE 8 TO 10
DEGREES BELOW NORMAL.

HIGH PRESSURE WILL BUILD ACROSS THE REGION WEDNESDAY AND WEDNESDAY
NIGHT...KEEPING CONDITIONS DRY BUT TEMPERATURES 5 TO 10 DEGREES
BELOW NORMAL.

HIGH PRESSURE WILL MOVE EAST THURSDAY TO ALLOW FOR A GREAT LAKES LOW
PRESSURE SYSTEM TO DRAG A COLD FRONT ACROSS THE REGION LATE THURSDAY
AND THURSDAY NIGHT. THERE IS A CHANCE OF SNOW SHOWERS THURSDAY INTO
THURSDAY NIGHT. SOME LIGHT RAIN MAY ALSO MIX FURTHER SOUTH AS HIGHS
MAY HOVER NEAR 40 DEGREES. OVERALL...TEMPERATURES SHOULD NOT BE AS
CHILLY AS EARLIER IN THE WEEK.

A CHANCE OF A FEW LINGERING SNOW SHOWERS NEAR THE CHESAPEAKE BAY DUE
TO TRAILING UPPER LEVEL ENERGY FRIDAY. HOWEVER A DEVELOPING DOWNSLOPING
EFFECT COULD PROHIBIT SNOW SHOWERS EAST OF THE BLUE RIDGE MOUNTAINS.
ELSEWHERE...SNOW SHOWERS IN THE POTOMAC HIGHLANDS.

HIGH PRESSURE WILL BUILD INTO THE REGION LATE FRIDAY THROUGH
SATURDAY...ALLOWING FOR DRYING OUT. TEMPERATURES SHOULD REMAIN BELOW
NORMAL.

&&

.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS ACROSS ALL TAF SITES OVERNIGHT...CONTINUING THRU
SUNDAY. SCT LOW-MID LVL CLOUDS WILL FORM AHEAD OF THE APPROACHING
PCPN...BUT NOT EXPECTING SUB-VFR CONDITIONS UNTIL AFTR 00Z
MON...THE EXCEPTION BEING KMRB WHICH COULD SEE LOWER CIGS AFTER
21Z. OVERALL...SUNDAY SHOULD BE DRY WITH THE PCPN MOVING IN SUNDAY
EVENING. WINDS WILL BE LIGHT AND VRB.

IFR CONDITIONS LIKELY WITH SNOW SUNDAY NIGHT INTO MONDAY. TAF
SITES OTHER THAN KMRB MAY START AS RAIN OR A RAIN/SNOW MIX FOR A
WHILE SUNDAY NIGHT. LIGHT E-ENE WINDS SUNDAY NIGHT...BECOMING N-NW
MONDAY. GUSTS POSSIBLE MONDAY OVER THE BALTIMORE/WASHINGTON
TERMINALS. CONDITIONS IMPROVE MONDAY NIGHT.

LINGERING LIGHT SNOW OR SNOW SHOWERS COULD POSE A THREAT FOR MVFR TO
IFR CONDITIONS TUESDAY. OTHERWISE...VFR CONDITIONS TUESDAY NIGHT AND
WEDNESDAY. NORTHWEST WINDS COULD GUST 20 TO 25 KNOTS TUESDAY THROUGH
WEDNESDAY.

&&

.MARINE...
WINDS THIS EVENING HV BEEN TRICKY. WHILE SFC FLOW HAS DIMINISHED
AFDK...30 KT WINDS RESIDE JUST 1K FT UPSTAIRS. THERE HAS BEEN
SPORADIC MIXING...MOST NOTABLY AT TPLM2. BUFKIT PROFILES SUGGEST
THAT THE LLJ WILL BE PRESENT TIL THE 06-09Z WINDOW. BELIEVE THAT
WE/LL BE IN SIMLR CONDS TIL THEN. HV OPTED TO EXTEND SCA TIL 08Z.

WINDS REMAIN MAINLY BELOW SCA CRITERIA SUNDAY. HIGHER CONFIDENCE
OF GUSTS INTO THE 20S LATE SUN NIGHT AND INTO MONDAY WITH
NORTHERLY FLOW SO SCA COULD BE NEEDED AS EARLY AS 06Z MON BUT MORE
LIKELY AFTER 12Z MON.

SCA WILL LIKELY BE NEEDED OVER AT LEAST CHESAPEAKE BAY AND THE
LOWER TIDAL POTOMAC MONDAY AND MONDAY NIGHT FOR GUSTY NORTH WINDS AS
LOW PRESSURE STRENGTHENS OFFSHORE.

SMALL CRAFT ADVISORY MAY BE NEEDED TUESDAY THROUGH WEDNESDAY AS
NORTHWEST WINDS GUST 20 TO 25 KNOTS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...FREEZING RAIN ADVISORY UNTIL 4 AM EST SUNDAY FOR MDZ501.
     WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY
     AFTERNOON FOR MDZ003-501-502.
     WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY EVENING
     FOR MDZ004-005-503-505.
VA...FREEZING RAIN ADVISORY UNTIL 4 AM EST SUNDAY FOR VAZ503.
     WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY EVENING
     FOR VAZ028-031-505.
WV...FREEZING RAIN ADVISORY UNTIL 4 AM EST SUNDAY FOR WVZ501-503-
     505.
     WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY
     AFTERNOON FOR WVZ050-051-055-501>504.
     WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY EVENING
     FOR WVZ052-053.
MARINE...SMALL CRAFT ADVISORY UNTIL 3 AM EST SUNDAY FOR ANZ530>534-
     537>541-543.

&&

$$
SYNOPSIS...SEARS/KCS
NEAR TERM...HTS/SEARS
SHORT TERM...KCS
LONG TERM...KLW
AVIATION...HTS/SEARS/KCS/KLW
MARINE...HTS/SEARS/KCS/KLW





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