Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 241513
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1013 AM EST SAT JAN 24 2015

.SYNOPSIS...
LOW PRESSURE PUSHES TO THE NORTHEAST TODAY. THE NEXT LOW PRESSURE
SYSTEM WILL CROSS THE AREA FROM THE WEST SUNDAY NIGHT THROUGH
MONDAY. HIGH PRESSURE IS THEN EXPECTED THROUGH THE MIDWEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
CURRENT ROUND OF PCPN BCMG LIGHT ACROSS THE REGION THIS MORNING
WITH TEMPERATURES WARMING INTO THE MID 30S. HAVE ALLOWED THE
WINTER WX ADVISORY TO EXPIRE ACROSS PORTIONS OF THE SHENANDOAH
VALLEY...AND HAVE GONE AHEAD AND CANCELLED THE SOUTHERN HALF OF
THE WINTER STORM WARNING ALONG WITH THE WINTER WX ADVISORY FOR
AREAS ALONG I-95 WITH THE THREAT OF SNOW/ICE ACCUMS ENDING.
CONTINUED THE WINTER WX ADVISORY FOR NORTH CENTRAL MD/PANHANDLE
OF WV AND NORTHERN VA DUE TO ON GOING LIGHT PCPN (MIX OF SNOW AND
DZ). WHILE AIR TEMPS ARE WARMING TO SLIGHTLY ABV FREEZING...ROAD
TEMPS ARE STILL AT OR SLIGHTLY BELOW FREEZING SO WILL CONTINUE THE
ADVISORY TILL 17Z. BY THEN EXPECTING WE CAN LET ALL PRODUCTS END.

THIS MORNINGS PCPN ENDS...WITH A SHORTWAVE SWINGING EAST BRINGING
SCT SNOW SHOWERS TO ALLEGHENY FRONT AREA FOR THE AFTN. IT COULD
ALSO PRODUCE ISO RAIN/SNOW SHOWERS TO AREAS TO THE EAST...BUT VERY
LIGHT QPF AMTS. THE PCPN EXITS TO THE EAST LATER TODAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
SFC LOW PUSHES OFF TO THE NORTHEAST AND THE MAIN FORCING WITH THE
UPPER LVL SHORTWAVE SHIFTS EAST. WILL MAINTAIN UPSLOPE SNOW
SHOWERS OVER THE ALLEGHENY FRONT REGION WITH A WNW FLOW ON THE
BACKSIDE OF THE LOW. THE SHOWERS ARE EXPECTED TO TAPER OFF AS THE
WINDS BACK TO THE SW NEAR DAYBREAK SUN MORNING...BUT THE LACK OF
PCPN WILL BE SHORT LIVED AS AN ALBERTA CLIPPER QUICKLY APPROACHES
THE REGION.

TEMPS SAT NIGHT NEAR NORMAL...WITH EVERYWHERE IN THE UPPER 20S TO
RIGHT AROUND 30.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
INCREASED POPS AND MODIFIED FORECAST SNOWFALL AMTNS FOR LATE SUN
INTO MON. THE BULK OF THE ACTIVITY STILL EXPECTED DURING THE
OVERNIGHT HRS INTO THE EARLY MRNG HRS/FIRST HALF OF MON.
HOWEVER...THIS LOOKS TO BE A TRANSITIONAL SYSTEM LIKE THE FEATURE
FROM A FEW DAYS AGO - ONLY MORE INTENSE FROM START TO FINISH. MOST
CLIPPER SYSTEMS MOVE QUICKLY AND THIS WILL BE NO EXCEPTION...BUT
INSTEAD OF A DIRECT PATH TO THE MID-ATLC - THE UPPER FEATURE WILL BE
FORCED SWD FOR A BRIEF DECELERATION PERIOD OVER THE UPPER MIDWEST.
WHILE SPREADING SNOW SHOWERS ACROSS THE OHIO VLY AND WAITING FOR THE
OTHER POTENT NRN ATLC SYSTEM TO MOVE FURTHER OFF THE COAST...THE
FEATURE WILL MAKE A DIVE TOWARD THE SRN APLCNS.

ALL GUIDANCE IS IN GOOD AGREEMENT ON THIS...W/ ONLY SLIGHTLY VARYING
DIFFERENCES IN THE OVERALL INTENSITY AND EXACT TRACK. THE EURO
HOWEVER MAKING A BIGGER EFFORT FOR THE TRANSITIONAL PHASE DIRECTLY
OVER OUR AREA LATE SUN INTO EARLY MON. THE LATEST RUN AND EVEN MORE
RECENT ONES HAVE EFFECTIVELY DISSIPATED THE WRN PRECIP TO RECONVENE
IT OVER THE ERN HALF OF THE AREA/CHESPKE BAY. THE GFS ON THE OTHER
HAND WRINGS OUT MOST OF IT`S PRECIP - IN THIS CASE SNOW - OVER THE
WRN HALF OF THE AREA THEN DISPLACES THE FORCING OFF THE COAST W/
ONLY LIGHT/INTERMITTENT SNOWS OVER THE ERN HALF OF THE AREA DURING
THE DAY ON MON. MAY NEED TO CONSIDER WINTER STORM WATCHES FOR
PORTIONS OF THE AREA...ESPEC THE WRN SECTIONS OF THE CWA - CERTAINLY
THE APLCNS AND POSSIBLY INTO THE SHEN VLY/BLUE RIDGE IF GUIDANCE
COMES IN BETTER AGREEMENT W/ QPF/TIMING/PLACEMENTS.

DIRECTLY BEHIND THE EXITING AND STRENGTHENING COASTAL SYSTEM WILL BE
A SECONDARY UPPER WAVE THAT GETS PULLED DOWN ACROSS THE GREAT LAKES
TOWARD THE MID-ATLC ON TUE. THE FEATURE ITSELF WILL BE DISSIPATING
LATE MON NIGHT UPON APPROACH TO THE UPPER MIDWEST...CARRYING A GOOD
SHOT OF COLD AIR AND ENOUGH LOW LEVEL MOISTURE TO CREATE SCATTERED
SNOW SHOWERS. AS THE WAVE PULLS AROUND THE BASE OF THE UPPER
TROUGH...THE SNOW SHOWERS WILL SWING ACROSS THE MID-ATLC DURING THE
DAYTIME HRS TUE BUT LIKELY DISSIPATING TOWARD THE LATTER HALF OF THE
DAY. AS THIS UPPER WAVE TRANSITIONS OFF THE COAST...THE MOISTURE
WILL BE CUT OFF QUICKLY AND PRECIP WILL END - UNTIL YET ANOTHER
UPPER WAVE APPROACHES FROM THE NORTH ON WED. THIS FEATURE WILL BE
LESS LIKELY TO AFFECT THE AREA OUTSIDE OF SOME UPSLOPE MTNS SNOWS
BUT WILL REINFORCE THE COLDER AIRMASS DURING THE MIDDLE OF THE WEEK.

THE NEXT WX CONCERN FOR THE EXTENDED IS THE COLD. THE TWO EXTRA
WAVES OF REINFORCING COLD AIR FROM THE NORTH TUE AND AGAIN ON WED
WILL NOT ONLY KEEP OUR DAILY HIGHS MAXED-OUT NEAR THE FREEZING MARK
BUT ALLOW OVERNIGHT LOWS TO DROP WELL INTO THE TEENS AND 20S ACROSS
THE REGION...SOME SINGLE DIGITS OVER THE APLCNS. HIGH PRES BRIEFLY
BUILDS IN FROM LATE WED INTO THU AND A RELATIVE WARM-UP BUT ONLY
INTO THE U30S ON THU AFTN.

ANOTHER CLIPPER WILL BE WELL ON ITS WAY TOWARD THE AREA DURING
LATTER HALF OF THE WEEK...MOVING ACROSS THE REGION LIKELY LATE THU
INTO FRI ACCORDING TO THE RECENT GFS AND EURO RUNS. NOT A COMPLETELY
SIMILAR SOLN BETWEEN THEM BUT ELEMENTS OF THE SAME LOOK...EXCEPT THE
GFS HOLDS A MORE COMPACT UPPER WAVE THAT SLIDES OVER THE AREA AND
BRINGS MORE PRECIP TO OUR REGION.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
OVC MVFR CIGS WITH PERIODS OF IFR CONDITIONS THRU 18Z. LIGHT PCPN
PSBL LATE THIS MORNING/EARLY AFTN BUT WILL BE MORE PERIODIC IN
NATURE AND MAINLY RAIN. -SN PSBL AT KMRB. CIGS/VIS WILL IMPROVE THIS
AFTN WITH NWLY FLOW GUSTING 20 TO 25 KT. VFR CONDITIONS TNGT.

A CLIPPER SYSTEM WILL QUICKLY ARRIVE DURING THE DAYTIME HRS ON
SUN...MAINLY THE LATTER HALF W/ MAINLY SNOW UPON ARRIVAL. PERIODS OF
SNOW FOR THE REGION LATE SUN INTO MON. IFR CONDS OR LOWER W/ THE
HEAVIEST ACTIVITY...THEN GUSTY NLY WINDS EARLY MON AS A LOW DEVELOPS
AND STRENGTHENS OFF THE COAST.

LINGERING SNOW SHOWERS ON TUE AND SOME SUB-VFR CONDS FOR THE FIRST
HALF OF THE DAY. ACTIVITY MOVING OFF THE COAST BY MID-WEEK. ANOTHER
COLD/POTENTIALLY SNOWY CLIPPER SYSTEM ON FRI.

&&

.MARINE...
SCA IN EFFECT FOR SRN PORTIONS OF THE WATERS...AND THEN ALL
WATERS TODAY WITH 20 TO 25 KT GUSTS EXPECTED. LINGERING SCA
GUSTS UP TO 20 KT THIS EVENING...THEN DECREASING OVERNIGHT.

WINDS REMAIN MAINLY BELOW SCA CRITERIA SUNDAY...WITH LOW CHC OF
OCNL GUSTS TO 18 KT PSBL SUN AFTN. HIGHER CONFIDENCE OF GUSTS INTO
THE 20S ON MONDAY WITH NORTHERLY FLOW SO SCA WILL MOST LIKELY BE
NEEDED AFTER 12Z MON. SMALL CRAFT ADVISORY MAY BE NEEDED MONDAY
EVENING AS NORTHERLY WINDS GUST OVER 20 KNOTS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER STORM WARNING UNTIL NOON EST TODAY FOR MDZ501.
     WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR MDZ003>006-
     502-503-505-507.
VA...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR VAZ027>031-
     505-507.
WV...WINTER STORM WARNING UNTIL NOON EST TODAY FOR WVZ501>504.
     WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR WVZ050>053-
     055.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR
     ANZ532>534-537-540>543.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ530-
     531-535-536-538-539.

&&

$$





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