-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 291444
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
944 AM EST THU JAN 29 2015

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE COAST THIS MORNING. A COLD FRONT
WILL SWING THROUGH THE REGION LATE TODAY INTO TONIGHT. A STRONG
PRESSURE GRADIENT AHEAD OF HIGH PRESSURE WILL BRING WINDY AND COLD
CONDITIONS FRIDAY INTO FRIDAY NIGHT. HIGH PRESSURE WILL BUILD OVER
THE AREA SATURDAY...BUT LOW PRESSURE MAY IMPACT THE AREA LATER
SUNDAY INTO MONDAY. COLD HIGH PRESSURE WILL RETURN FOR THE MIDDLE
PORTION OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
MAIN CONCERN THIS MORNING IS THE WINTRY MIX EXPECTED THIS AFTERNOON
AND EVENING FOR THE MID-ATLANTIC. THE OUTLOOK AREA DROPPED INTO THE
TEENS FOR MOST OF THE AREA OVERNIGHT CAUSING SFC TEMPS TO REACH THE
TEENS AND 20S. THIS WILL PLAY A ROLE TODAY AS PRECIPITATION AHEAD OF
A COLD FRONT MOVES INTO THE REGION IN TIME FOR THE EVENING RUSH
HOUR.

A 40KT 925MB LLJ AHEAD OF AN APPROACHING COLD FRONT IS STILL WEST OF
THE APPALACHIANS THIS MORNING. THIS WILL MOVE EASTWARD AHEAD OF THE
COLD FRONT THIS AFTERNOON AND TEMPS AT 925MB WILL BECOME +32 F.
850MB TEMPS WILL ALSO CONTINUE TO BECOME +32 F TODAY. THIS WILL
ALLOW FOR MIXED PRECIPITATION WITH WARM AIR OVER COLD AIR/SURFACES.
SOUTHERLY FLOW AT THE SFC WILL ALLOW TEMPS AND DEWPTS TO RISE TODAY.
SNOW PACK ACROSS THE NRN MID-ATLANTIC WILL SLOW TEMPS FROM RISING AS
FAST AS CENTRAL VA AND SOUTHERN MD. SFC TEMPS WILL BE A CONCERN
TODAY AS THE GROUND IS FROZEN IN MANY PLACES. CLOUD COVER MOVING
OVERHEAD WILL ALSO SLOW TEMPS FROM RISING TODAY AS WELL. THAT BEING
SAID...TEMPS WILL RANGE FROM THE LOW 30S NEAR THE MD/PA BORDER TO
THE LOW 40S FROM DCA-CHO-NHK. THE SOUTHERLY FLOW WILL HELP SCOUR OUT
VALLEYS WEST OF THE BLUE RIDGE AS WELL AND SHD-WOO-W99 SHOULD RISE
INTO THE UPPER 30S. A CAVEAT IS THE HIGHER ELEVATIONS ON THE BLUE
RIDGE AND WESTWARD. ZR IS POSSIBLE AS TEMPS MAY STAY BELOW FREEZING.
WILL NEED TO MONITOR AND ADVISORY MAY BE NEEDED.

A WINTER WX ADVISORY IS IN EFFECT FOR THIS AFTERNOON THROUGH THE
EVENING FOR MUCH OF THE NRN OUTLOOK AREA. TEMPS WILL BE CLOSELY
MONITORED TODAY. DCA IS ALREADY AT 31 DEGREES BUT SURROUNDING
SUBURBS ARE IN THE 20S. THERE IS UNCERTAINTY REGARDING PTYPE NEAR
THE I-95 CORRIDOR DURING THE EVENING RUSH HOUR. AT THIS TIME...TEMPS
ARE FCST TO GO ABOVE FREEZING EAST OF THE WINTER WX ADVISORY. AS
GUIDANCE COMES IN THIS MORNING DECISIONS WILL BE MADE IF WE NEED TO
EXTEND THE ADVISORY FURTHER EAST.

PREVIOUS DISCUSSION...

PRECIPITATION WILL MOVE AWAY FROM MOST AREAS THIS EVENING AND THE
COLD FRONT IS EXPECTED TO PASS THROUGH OVERNIGHT. GUSTY NORTHWEST
WINDS ARE POSSIBLE LATE TONIGHT...ESPECIALLY ALONG THE RIDGES. UPSLOPE
SNOW SHOWERS ARE EXPECTED TONIGHT ALONG AND WEST OF THE ALLEGHENY
FRONT. A WINTER WEATHER ADVISORY IS IN EFFECT FOR THESE AREAS.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
LOW PRESSURE WILL INTENSIFY OVER NEW ENGLAND FRIDAY WHILE HIGH
PRESSURE APPROACHES FROM THE MIDWEST. THE PRESSURE GRADIENT
BETWEEN THESE SYSTEMS WILL BE QUITE STRONG...RESULTING IN GUSTY
NORTHWEST WINDS. WIND GUSTS AROUND 45 TO 50 MPH ARE POSSIBLE AND A
WIND ADVISORY MAY BE NEEDED FOR PORTIONS OF THE AREA. THE STRONG
NORTHWEST WINDS WILL USHER IN COLD CONDITIONS. IN FACT...TEMPS MAY
HOLD STEADY OR EVEN FALL THROUGHOUT THE DAY. TEMPS FRIDAY
AFTERNOON WILL RANGE FROM THE SINGLE DIGITS IN ALLEGHENY HIGHLANDS
TO THE LOWER AND MIDDLE 30S IN SOUTHERN MARYLAND. MORE UPSLOPE
SNOW SHOWERS ARE EXPECTED ALONG AND WEST OF THE ALLEGHENY FRONT.
THE WINTER WEATHER ADVISORY CONTINUES UNTIL NOON...BUT SNOW
SHOWERS ARE POSSIBLE DURING THE AFTERNOON AS WELL.

FOR LOCATIONS EAST OF THE ALLEGHENY FRONT...A FEW SNOW SHOWERS ARE
POSSIBLE FRIDAY AS ANOTHER POTENT UPPER-LEVEL DISTURBANCE SWINGS
THROUGH THE AREA. MOST AREAS WILL NOT SEE ACCUMULATING SNOW...BUT
THERE WILL BE ENOUGH INSTABILITY TO COMBINE WITH STRONG COLD
ADVECTION FOR THE POSSIBILITY OF A FEW BURSTS OF HEAVIER SNOW
SHOWERS. THIS COULD LEAVE A QUICK COATING IN SPOTS AND WITH SUDDEN
CHANGES IN VISIBILITY THAT COULD HAVE A SIGNIFICANT IMPACT ON
TRAVEL...ALTHOUGH IT WOULD BE LOCALIZED. THE BEST CHANCE FOR THE
HEAVIER SNOW SHOWERS WILL BE ACROSS NORTHERN MARYLAND...EASTERN
WEST VIRGINIA AND NORTHERN VIRGINIA.

COLD AND DRY CONDITIONS FRI NIGHT AS SFC HIGH PRESSURE BUILDS SOUTH
AND EAST. LINGERING SNOW SHOWERS OVER THE ALLEGHENY FRONT FRI
EVENING EXPECTED TO DIMINISH AS THE NW FLOW INJECTS MUCH DRIER AIR.
MAIN CONCERN FOR FRIDAY NIGHT WILL BE THE WELL BELOW NORMAL
TEMPS...ALMOST 10-15 DEGREES BELOW. COMBINING WITH NW WINDS WITH
GUSTS 20-30 KTS...AND IN HIGHER ELEVATIONS 30-35 KTS...WIND CHILLS
FORECASTED TO DROP TO AROUND -10 DEGREES CELSIUS POTOMAC
HIGHLANDS...NEGATIVE SINGLE DIGITS ALONG THE MASON-DIXON LINE...AND
POSITIVE SINGLE DIGITS THE REMAINDER OF THE AREA. WILL CONTINUE TO
HIGHLIGHT THE WIND CHILL ADVISORY POTENTIAL IN THE HWO...MAINLY FOR
THE FAR WESTERN AREAS. USED A BLEND OF ADJMETBC/MOSBC WHICH HAS BEEN
TRENDING WELL FOR OVERNIGHT TEMPS.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
CENTER OF THE HIGH SLIPS SOUTHEAST INTO THE SE US SAT WHILE A NEAR
ZONAL FLOW SETS UP DURING THE DAY...AND WEAK RIDGING BUILDS SAT
NIGHT-SUN MORNING. THE PATTERN KEEPS THE AREA DRY THOUGH COLD THRU
SAT WITH TEMPS STILL RUNNING BELOW NORMAL. WARMING TREND BY SAT
NIGHT AS WINDS BACK TO SW FLOW...WITH 850MB TEMPS WARMING TO AROUND
-5 DEGREES CELSIUS.

NEXT CHC FOR PCPN SUN-MON WITH SFC LOW DEVELOPING OVER GOM AND
RIDING A NEAR STATIONARY FRONT TO OUR SOUTH. SOME QUESTION REMAINS
ON PCPN TIMING AND INTENSITY...AND AS SUCH THEN P-TYPE. GFS/CMC
STRONGER SOLUTIONS WITH THE LOW DEVELOPMENT AS UPPER LVL TROUGH DIGS
DEEPER SOUTH...AND PICKS UP SHORTWAVE ENERGY RIDING THE SOUTHERN
STREAM...WHILE THE ECMWF KEEPS MORE OF A SEPARATION. WENT WITH
LIKELY POPS BY SUN AFTN OVER WESTERN AREAS TO HIGHLIGHT THE HIGHER
CONFIDENCE OF PCPN...THEN SPREADING THE LIKELY POPS TO THE EAST FOR
SUN NIGHT-MON. CONCERNING PCPN TYPE...MAINTAINED MAINLY A SNOW
EVENT...WITH PSBL TRANSITION TO RAIN DURING THE AFTN SUN OVER JUST
THE FAR SOUTHERN AREAS OF THE CWA. HIGHER CONFIDENCE ANY PCPN ON
MONDAY REMAINS ALL SNOW WITH 850MB TEMPS DROPPING -10 TO -15 DEGREES
CELSIUS DURING THE DAY. AS THE LOW BECOMES CLEARER ON SUBSEQUENT
SHIFTS...WILL BE ABLE TO HAVE A BETTER HANDLE ON P-TYPE AND AMTS AT
THE ONSET.

PCPN CLEARS THE AREA BY TUES MORNING...WITH SFC HIGH BRINGING
ANOTHER PERIOD OF DRY AND COLD TEMPS. TRENDED COLDER WITH HIGHS TUES
AND LOWS TUES NIGHT AS A RESULT. MODEL DIVERGENCE BY MID WEEK ON THE
HANDLING OF THE NEXT LOW PRESSURE SYSTEM...WITH PCPN PSBL ONCE AGAIN
LATE WED-THURS.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
SOUTHERLY WINDS ARE EXPECTED TODAY. A BRIEF PERIOD OF WINTRY
PRECIPITATION IS POSSIBLE LATE THIS AFTERNOON INTO EARLY THIS
EVENING. DRIER CONDITIONS WILL RETURN TONIGHT. STRONG NORTHWEST
WINDS ARE EXPECTED FRIDAY WITH A COUPLE SNOW SHOWERS POSSIBLE.
NORTHWEST WINDS WILL GUST AROUND 35 TO 40 KNOTS FRIDAY.

FRIDAY NIGHT-SAT NIGHT...VFR LIKELY...PSBL SUB-VFR LATE SAT NIGHT.
GUSTY NW WINDS 15-20 KTS WITH GUSTS TO 25 KTS FRI NIGHT...BCMG LESS
THAN 10 KTS BY SAT AFTN. PSBL LLWS FRI NIGHT WITH 2KFT WINDS 40-50
KTS.

SUN-MON...SUB-VFR LIKELY WITH PCPN...PSBL SUB-IFR SUN NIGHT/MON
MORNING. WINTRY MIX PSBL. INCREASING NW WINDS MON...GUSTS TO 20 KTS.

MON NIGHT-TUES NIGHT...VFR LIKELY.

WED-WED NIGHT...SUB-VFR PSBL WITH PCPN.

&&

.MARINE...
SOUTHERLY WINDS ARE EXPECTED AHEAD OF A COLD FRONT TODAY. THE COLD
FRONT WILL PASS THROUGH TONIGHT AND GUSTY NORTHWEST WINDS ARE
EXPECTED BEHIND THE FRONT FRIDAY. A SMALL CRAFT ADVISORY IS IN
EFFECT FOR PORTIONS OF THE WATERS THROUGH TONIGHT. A GALE WARNING
IS IN EFFECT FOR THE WATERS FRIDAY.

GALES LIKELY AT LEAST FIRST HALF OF FRIDAY NIGHT ON CHESAPEAKE
BAY...AND POSSIBLY ON THE UPPER POTOMAC. OCNL GALES MAY LINGER TILL
DAYBREAK SAT ON THE BAY. WINDS SUBSIDE SAT BUT REMAINING 15-20 KTS
DURING THE DAY. WINDS DIMINISH SAT NIGHT...AND REMAIN SUB-SCA
THROUGH SUNDAY. DEPENDING ON THE TRACK OF THE LOW SUN
NIGHT-MON...SCA CONDITIONS WILL BECOME POSSIBLE AGAIN. SUB-SCA
CONDITIONS RETURN FOR MID WEEK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO NOON EST
     FRIDAY FOR MDZ501.
     WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM EST
     THIS EVENING FOR MDZ003-502.
     WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM EST
     THIS EVENING FOR MDZ004-005-503-505.
VA...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EST
     FRIDAY FOR VAZ503.
     WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM EST
     THIS EVENING FOR VAZ028-031.
     WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM EST
     THIS EVENING FOR VAZ505.
WV...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO NOON EST
     FRIDAY FOR WVZ503.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EST
     FRIDAY FOR WVZ501-505.
     WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM EST
     THIS EVENING FOR WVZ050>053-504.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EST
     FRIDAY FOR ANZ530>534-537>543.
     GALE WARNING FROM 6 AM TO 6 PM EST FRIDAY FOR ANZ530>543.
     SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 PM EST THIS
     EVENING FOR ANZ535-536.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL/HAS
SHORT TERM...BJL/SEARS
LONG TERM...SEARS
AVIATION...BJL/SEARS
MARINE...BJL/SEARS