Wind Chill Advisory 1, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
327 AM EST MON JAN 2 2012

.SYNOPSIS...
HIGH PRESSURE BUILDS IN THROUGH TUESDAY NIGHT...WITH GUSTY
NORTHWEST WINDS BRINGING THE COLDEST AIR THUS FAR THIS SEASON.
AN UPPER LEVEL DISTURBANCE WILL CROSS ON WEDNESDAY...FOLLOWED BY A
MODERATING TREND FOR THE SECOND HALF OF THE WEEK.
&&

.NEAR TERM /THROUGH TONIGHT/...
CDFNT CLEARED CWA YDA EVE...WITH STRONG CAA AND GUSTY NW WINDS IN
ITS WAKE. DWNSLPG/COMPRESSIONAL WRMG AND AT LEAST PARTIAL SC DECK
ACRS RGN HAS CURBED COOLG OVNGT...WITH 3 AM TEMPS STILL IN 40S E OF
BLUE RDG/30S W. WINDS HAVE GUSTED ABV 30 KTS MANY LOCATIONS...BUT
GENERALLY BELOW 40KT ADZY CRITERION SO WILL DROP WIND HEADLINE EARLY.

XPCT BREEZY CONDS TO CONT THRU TNGT DUE TO TIGHT PRES GRADIENT BTWN
LOPRES IN CANADIAN MARITIMES AND HIPRES OVR SRN PLAINS. MOST OF CWA
WILL BE DRY...ASIDE FROM A FEW FLURRIES W OF BLUE RDG...WITH PERIODS
OF SC SPILLING SEWD INTO RGN TDA...BCMG DOMINANT OVNGT AS UPR TROF
PASSES THRU CWA.  HWVR...TRADITIONAL UPSLOPE FAVORED AREAS WRN SIDE
OF ALLEGHENY FRONT WILL SEE SIGNIFICANT SNOWFALL. LGT SNSH THIS MRNG
WILL INCR TDA AS MOISTURE FROM GREAT LAKES INTERACTS WITH TERRAIN
INDUCED LIFT. LLVL FLOW WILL BACK FROM PRESENT WNW TO NNW AS LOPRES
STRENGTHENS OFF DELMARVA...ALLOWING MORE FAVORABLE WIND TRAJECTORY
FROM LAKE ERIE BY THIS EVE. MODEL SOUNDINGS DEPICT DEEP
MOISTURE...INSTABILITY/STEEP LAPSE RATES AS H8 TEMPS PLUMMET TO
BELOW -15C...AND AMPLE LIFT TNGT TO PRODUCE HVY SNSH WITH HIGHEST
ACCUM DURG THE EVE/OVNGT. WSW RMNS IN EFFECT ACRS WRN 5...AND STORM
TOTALS MAY EXCEED 1 FT IN SPOTS.

TEMPS WILL RISE LITTLE TDA...WITH MAXIMA REACHING 40S E OF BLUE
RIDGE...U30S SHENANDOAH VLY...AND U20S MOUNTAINS. MINIMA TNGT FCST
TEENS ACRS MOUNTAINS AND L-M20S ELSEWHERE. WITH PERSISTENT NW WINDS
OF 15-25 KTS...GUSTING TO JUST BELOW ADZY THRESHOLD...WIND CHILLS
WILL BE IN TEENS TNGT...WITH SINGLE DIGITS ALONG/W OF BLUE RIDGE.
HIGHER ELEVATIONS OF HIGHLAND...GRANT...AND PENDLETON CNTYS XPCD TO
HAVE WIND CHILL VALUES AOB -5F...THUS WIND CHILL ADVISORY HAS BEEN
HOISTED BEGINNING 0Z TNGT.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
H5 TROF AXIS SWINGS THRU TUE...PROVIDING LAST BIT OF ENHANCED
SUPPORT FOR UPSLP SHSN...AS WELL AS DP MIXING POTENTIAL AREAWIDE.
THE THERMAL TROF WL BE LAGGING SVRL HRS BHD...MAKING TUE THE DAY W/
THE COLDEST MAXT /AND MIN-T TUE NGT/ OF THE BUNCH. CONSIDERING
SUSTAINED WNDS 15-20 KT /ALMOST RIGHT OFF THE DECK/ AND 25-30 KT
GUSTS EASILY ACHIEVED W/IN MIXED LYR /WHICH SHUD REACH UP CLOSE TO
H8/...WIND CHILLS WL BE A FACTOR THROUGHOUT THE DAY /AND INTO THE
NGT/ ACRS THE WHOLE AREA. ATTM...WL JUST CARRY THE ADVY FM TNGT INTO
ELY TMRW MRNG. WHILE HAZARD GRIDS LKLY WONT SPREAD E OF THE
APPALACHIANS... APPARENT TEMPS STRUGGLING TO REACH 20F TUE /AND THEN
DROPPING TO 5-15 ABV TUE NGT/ WL BE PERCEIVED AS A BIG DEAL...SPCLY
IN LIGHT OF ACTUAL TEMPS THIS PAST WKND.

IN TERMS OF UPSLP SNOWFALL...CUD FORSEE A HNDTH OR TWO LIQ QPF BEING
SQUEEZED OUT HRLY ALONG THE WRN SLOPES. RATIOS WUD BE RATHER HIGH
/25-1 PER BOTH NAM AND GFS BUFKIT/...SO THAT WUD EQUATE TO ANTHR 2-3
INCHES OF SNOW. ACTUAL SNOWFALL WL BE LCLZD AND COME IN BANDS...BUT
W/ FCST WNDS...IT/LL BE AWFULLY TOUGH TO ACTUALLY MEASURE ANYTHING.
WHILE UPA FLOW REMAINS SOMEWHAT NWLY TUE NGT...BLDG SFC RDG WL
DISRUPT BANDING IN THE EVNG /FOR LINGERING FLURRIES/ AND THEN SHUD
SURPRESS ACTIVITY OUTRIGHT OVNGT. WL ADD CHC POPS FOR THE EVNG.

ELSW...SKIES WL BE CLRG TUE PM IN THE WAKE OF THE TROF...BEFORE INCR
A LTL TWD WED DAWN AS H8 WAA ARRIVES. BOTH GFS/NAM SUGGEST THAT A
S/WV WL BE ARRIVING SOMETIME WED IN THE NW FLOW. HWVR...THEY DIFFER
ON THE DETAILS...INCL WHETHER THERE WL BE ANY QPF. SINCE AMS DRY AND
VORT LOOKS VIGOROUS /SPCLY PER GFS/ DONT WANT TO DISCOUT THE
POTENTIAL FOR FLURRIES. HV REVISED THEIR PLACEMENT WED AFTN...AND
ADDED SCHC FOR MEASUREABLE SHSN. THOSE CHCS SHUD INCR BHD THE
WV...AND GRIDS NOW REFLECT THAT.

HV REVISED MAXT TUE-WED DOWN FOR SUPPLY OF MODIFIED COLD AIR...AMPLE
CLDS AND LOW SUN ANGLE. ALTHO WL BE W/IN SFC RDG TUE NGT...THERE
SHUD BE AT LEAST A LTL WND AND SCT CLDS TO PREVENT A TEMP FREEFALL.
/DEWPTS IN THE SINGLE DIGITS!/ STILL...WERE TALKING MIN-T IN THE
TEENS...W/O MUCH CITY/SUBURB SPREAD.
&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A POSITIVELY TILTED TROUGH ACROSS THE SOUTHERN CONUS WILL MOVE
OFFSHORE MID-WEEK. BEHIND THE TROUGH...PREVAILING ZONAL FLOW PLUS A
SFC HIGH OVER THE GULF WILL FUNNEL MORE MODERATE TEMPS INTO THE
MID-ATLANTIC FOR THE END OF THE WORK WEEK. DAYTIME TEMPS WILL BE
ABOVE FREEZING FOR MOST OF THE AREA. MODELS ARE IN GOOD AGREEMENT ON
THE TIME OF A SHORTWAVE THAT WILL MOVE NORTH OF THE REGION OVER THE
WEEKEND. A STRONG SFC LOW OVER SOUTHERN CANADA WILL PUSH A COLD
FRONT THROUGH THE AREA SUNDAY. A PERIOD OF RAIN LATER IN THE WEEKEND
IS POSSIBLE WITH THE SYSTEM. AT THIS POINT...THE LIKELIHOOD OF
FROZEN PRECIP IS NOT GREAT WITH THE WARMER TEMPS AT THE LATTER HALF
OF THE WEEK AND GUIDANCE 850 TEMPS ABOVE FREEZING.
&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
VFR CONDS XPCD TO DOMINATE THRU NEXT 30 HRS...THO BKN/OVC 4-6KFT
CIGS MAY LWR TO NEAR MVFR THRESHOLDS AT KMRB AT TIMES. NW WINDS OF
15-20KTS WITH GUSTS AS HIGH AS 30KT WILL PERSIST...PEAKING THIS
AFTN.

VFR CONDS ANTICIPATED REST OF WK...BUT WNDS WL BE AN OP ISSUE TUE.
XPCT SUSTAINED 15-20 KT NW WNDS...GUSTING UP TO 30 KT. MAY ALSO SEE
A FLURRY OR TWO TUE INTO WED...PARTICULARLY INVOF MRB...BUT AGN THIS
SHUDNT BE AFFECTING THE FLGT CATEGORY.
&&

.MARINE...
SURGE OF COLD AIR FM THE UPR LVL CDFNT MIXING TO THE SFC...
RESULTING IN 30-35 KT GUSTS AT DC AND BALT HARBOR. ANTICIPATE THAT
SURGE WL TRANSLATE ACRS THE WATERS ELY THIS MRNG...BUT SHUD BE
RELATIVELY SHORT LIVED /NO MORE THAN A CPL HRS AT ANY ONE
LOCATION/. HV ISSUED MWS TO ADDRESS.

NW WINDS WILL CONT TO GUST FROM 20-30 KTS AFTER SUNRISE TDA AND
TNGT DUE TO STRONG CAA AND TNGT PRES GRADIENT BTWN N ATLC LOPRES
AND MS VLY HIPRES. SCA IN EFFECT THRU TNGT. UPR TROF AXIS/STRONGER
WINDS ALOFT AND MOST INTENSE CAA WILL CROSS OVR WATERS LATER
TNGT...WHEN GUSTS TO GALE CRITERION CANT BE RULED OUT.
HWVR...CONFIDENCE TO LOW ATTM TO UPGRADE HEADLINES.

WNDS TUE WL REMAIN AWFULLY CLOSE TO GLW. A PASSING S/WV WL TAP WINDS
HIER ALOFT...AND THE NW FLOW SUPPORT DEEPER MIXING THRU THE AFTN.
ONLY QSTN WL BE WHETHER WNDS WL BE JUST ABV OR JUST BLO CRIT. HV
OPTED AT THIS PT TO CARRY A STRONG SCA INTO TUE EVNG...AND CONT
MENTION POTL OF GLW IN SYN/HWO. TUE NGT WNDS WL GRDLY DECR AS
HIPRES BLDS...AT LEAST BLO SCA CRIT...BUT WNDS NEVER GO LGT BEFORE
ANTHR UPA DISTURBANCE PASSES BY WED. SHUD BE ABLE TO STAY UNDER
CRIT FOR THIS 2ND GO ARND.

&&

.FIRE WEATHER...
AS DRY AIR ADVECTS IN TDA...RH WILL FALL TO NEAR 30 PERCENT...WITH
SUSTAINED WINDS CLOSE TO 20 KTS...BOTH NEAR CRITERIA FOR FIRE
WEATHER CONCERNS. 10-HR FUEL MOISTURE WILL DROP TDA...BUT XPCD TO
RMN ABV 8 PERCENT...NOT LOW ENUF TO WARRANT SPS/RFW.

TMRW WL BE ANTHR WINDY DRY DAY TO BE MONITORED.
&&

.TIDES/COASTAL FLOODING...
WATER LVLS 1 TO 1 1/2 FT ABV ASTRO NORMS DUE TO SUNDAYS SLY FLOW.
HWVR...STRONG NW WNDS HV ARRIVED BHD THE COLD FRONT... WHICH WL
RESULT IN BLOWOUT CONDS. THINK LVLS WL RETURN TO NORMAL VALUES
THIS MRNG...AND SHUD BE BLO ASTRO NORMS TAFTN-TNGT-TMRW.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER STORM WARNING UNTIL 5 PM EST TUESDAY FOR MDZ501.
VA...WINTER STORM WARNING UNTIL 5 PM EST TUESDAY FOR VAZ503.
     WIND CHILL ADVISORY FROM 7 PM THIS EVENING TO 9 AM EST TUESDAY
     FOR VAZ503-504.
WV...WINTER STORM WARNING UNTIL 5 PM EST TUESDAY FOR WVZ501-503-505.
     WIND CHILL ADVISORY FROM 7 PM THIS EVENING TO 9 AM EST TUESDAY
     FOR WVZ501-502-505-506.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TUESDAY NIGHT FOR
     ANZ530>543.

&&

SYNOPSIS...SBK/HTS
NEAR TERM...SBK
SHORT TERM...HTS
LONG TERM...CJL
AVIATION...SBK/HTS
MARINE...SBK/HTS
FIRE WEATHER...SBK/HTS
TIDES/COASTAL FLOODING...HTS

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