Mid Atlantic Winter Storms 2009-2010 updated

[Stephanie]

Just a dusting of snow here from the storm. We had a mix of rain and snow for most of the day. It was pretty none the less. Put me in the mood to decorate for Christmas and shop.

[angelwing]

I got home from work Sat afternoon and it had started snowing around 11AM in Philly, by the time it was done we had about 4 inches Sat night in Blue Bell; we decorated the inside and finished up outside yesterday

Being North of the city is nice

[Stephanie]

We were VERY FORTUNATE that the mega storm that hit 2/3's of the country only brought us 2 inches of rain overnight. It could've been 20 inches of snow.

[angelwing]

We were VERY FORTUNATE that the mega storm that hit 2/3's of the country only brought us 2 inches of rain overnight. It could've been 20 inches of snow.

Yes, we got very lucky, minor flooding I had was a lot easier to deal with than 20 inches of snow (though I would have preferred the snow!)

[Lowpressure]

It now appears with models trending colder, that portions of the Mid Atlantic are in line for a nice winter storm. Winter Storm Watches have been posted from about Raleigh and points west.

NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
338 AM EST THU DEC 17 2009

...MAJOR WINTER STORM TO AFFECT THE AREA FRIDAY THROUGH SATURDAY
AFTERNOON...

.A COASTAL STORM SYSTEM IS EXPECTED TO SPREAD PRECIPITATION OVER
THE MOUNTAINS FRIDAY INTO SATURDAY. TEMPERATURES ARE EXPECTED TO
BE WARM ENOUGH FOR PRECIPITATION TO FALL MAINLY AS SNOW ACROSS
MUCH OF THE MOUNTAINS...WHILE A MIXTURE OF RAIN...SLEET AND SNOW
IS EXPECTED IN THE PIEDMONT. SIGNIFICANT ACCUMULATIONS OF SNOW ARE
POSSIBLE...ESPECIALLY ACROSS THE NORTH CAROLINA MOUNTAINS AND
FOOTHILLS...AND PIEDMONT AREAS ALONG THE I-40 CORRIDOR.

...WINTER STORM WATCH IN EFFECT FROM FRIDAY MORNING THROUGH
SATURDAY AFTERNOON...

THE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUED
A WINTER STORM WATCH...WHICH IS IN EFFECT FROM FRIDAY MORNING
THROUGH SATURDAY AFTERNOON.

SNOW...POSSIBLY MIXED WITH SLEET AND RAIN...WILL SPREAD INTO THE
WESTERN PIEDMONT OF NORTH CAROLINA...AS WELL AS NORTHEAST PORTIONS
OF UPSTATE SOUTH CAROLINA FRIDAY MORNING. THE PRECIPITATION IS
EXPECTED TO FALL MAINLY AS SNOW THROUGH MUCH OF THE AFTERNOON...
ALTHOUGH A CHANGE TO A MIX OF SLEET AND RAIN IS POSSIBLE ALONG AND
SOUTH OF I-85 DURING THE EVENING. PRECIPITATION WILL CONTINUE
THROUGH MUCH OF SATURDAY NIGHT BEFORE GRADUALLY TAPERING OFF EARLY
SATURDAY.

STORM TOTAL SNOWFALL IS EXPECTED TO RANGE FROM 2 TO 4 INCHES
IN AREAS SOUTH OF I-40...TO 4 TO 6 ACROSS THE NORTHWEST PIEDMONT.
LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE WITHIN HEAVIER BANDS OF
PRECIPITATION.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.

[srainhoutx]

Good Luck Lowpressure! I'm seeing some modeled totals that are just insane for parts of NC, VA, MD and on up to the Big Cities along North East Corridor.

[srainhoutx]

Updated HPC Prelim Extened Disco...

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
818 AM EST THU DEC 17 2009

VALID 12Z MON DEC 21 2009 - 12Z THU DEC 24 2009

A REX-BLOCK EXTENDING FROM GREENLAND TO ONTARIO/QUEBEC AND A LARGE
AMPLIFYING UPPER TROUGH OVER THE NORTHERN PACIFIC WILL SUPPORT AN
UNUSUALLY HIGH-AMPLITUDE SPLIT-FLOW REGIME OVER THE CONUS THROUGH
THE MEDIUM RANGE PERIOD. ONE SOURCE OF SHORTWAVE TROUGH
DEVELOPMENT WILL OCCUR WITHIN AND AROUND THE LOW SEGMENT OF THE
REX-BLOCK...WITH NORTHWESTERLY FLOW ALOFT LIKELY ALLOWING THESE
SYSTEMS TO PERPETUATE COLD AND SOMEWHAT UNSETTLED CONDITIONS
ACROSS THE DAKOTAS/GREAT LAKES/OHIO VALLEY/NORTHEAST.
MEANWHILE...AN UPPER LOW NEARING THE PACIFIC NORTHWEST DAY 3
SHOULD REMAIN CUT OFF FROM THE MAIN FLOW AS IT DRIFTS OVER THE
NORTHWEST BRINGING WET CONDITIONS TO THAT REGION DAYS 3-5 BEFORE
SHIFTING EASTWARD AHEAD OF THE APPROACHING PACIFIC UPPER TROUGH.
ALTHOUGH TIMING/PLACEMENT/INTENSITY DIFFERENCES ARE QUITE
LARGE...SEVERAL DETERMINISTIC SOLUTIONS ALONG WITH MANY GEFS
MEMBERS SHOW CYCLOGENESIS COMMENCING IN THE LEE OF THE SOUTHERN
ROCKIES DAYS 5/6...ESPECIALLY AS THE UPPER TROUGH NEARS THE GULF
COAST REGION BY DAY 7...WITH ALL MODELS HINTING TOWARD ANOTHER
SIGNIFICANT WINTER STORM DEVELOPING. GENERALLY PREFER THE DETAILS
OF THE ECMWF/GFS ENS MEANS WITH THIS SYSTEM...ESPECIALLY EARLY IN
THE PERIOD ACROSS THE NORTHWEST WHERE THE GFS LIES NEAR THE FAST
EDGE OF ALL THE GUIDANCE.

FINALLY...DEEPENING LOW PRESSURE OFF THE MID-ATLANTIC COAST AT THE
START OF DAY 3 SHOULD BE ACCELERATING NORTHEASTWARD AFTER LEAVING
BEHIND A SIGNIFICANT MID ATLC REGION SNOW EVENT. INTENSIFYING LOW
MOVING ALONG THE GULFSTREAM EDGE LIKELY TO BE A SERIOUS MARINE
THREAT. SEE OPC WARNINGS.

UPDATED MORNING MEDIUM RANGE PRESSURES/FRONTS WILL BEGIN WITH THE
OPERATIONAL 00Z ECMWF DAYS 3-5 BEFORE SHIFTING TO A 70/30 BLEND OF
THE ECMWF ENSEMBLE MEAN AND GFS ENSEMBLE MEAN DAYS 6/7. AT 6-7
DAYS OUT THESE MEANS TONE DOWN THE SIGNIFICANT MS VALLEY
CYCLOGENESIS SEEN BY OP MODEL RUNS WITH LARGE DIFFERENCES LATE
PERIOD.
JAMES/ROSENSTEIN

[lester]

Game on

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
148 PM EST THU DEC 17 2009

DCZ001-MDZ003>007-009>011-013-014-016>018-501-502-VAZ028-031-042-
052>054-WVZ050>053-503-504-180300-
/O.NEW.KLWX.WS.A.0008.091219T0500Z-091220T1100Z/
DISTRICT OF COLUMBIA-WASHINGTON-FREDERICK MD-CARROLL-
NORTHERN BALTIMORE-HARFORD-MONTGOMERY-HOWARD-SOUTHERN BALTIMORE-
PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS-CALVERT-
EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY-
FREDERICK VA-CLARKE-LOUDOUN-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-
FAIRFAX-ARLINGTON/FALLS CHURCH/ALEXANDRIA-HAMPSHIRE-MORGAN-
BERKELEY-JEFFERSON-WESTERN MINERAL-EASTERN MINERAL-
INCLUDING THE CITIES OF...WASHINGTON...HAGERSTOWN...FREDERICK...
WESTMINSTER...GAITHERSBURG...COLUMBIA...BALTIMORE...ANNAPOLIS...
WALDORF...ST MARYS CITY...FROSTBURG...CUMBERLAND...WINCHESTER...
LEESBURG...MANASSAS...MANASSAS PARK...FAIRFAX...ALEXANDRIA...
FALLS CHURCH...MARTINSBURG...CHARLES TOWN...EMORYVILLE...
HARTMANSVILLE...KEYSER...FORT ASHBY
148 PM EST THU DEC 17 2009

...WINTER STORM WATCH IN EFFECT FROM LATE FRIDAY NIGHT THROUGH
LATE SATURDAY NIGHT...

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A
WINTER STORM WATCH...IN EFFECT FROM LATE FRIDAY NIGHT THROUGH
LATE SATURDAY NIGHT.

* PRECIP TYPE...SNOW.

* ACCUMULATIONS...HEAVY SNOW WITH ACCUMULATIONS GREATER THAN 5
INCHES.

* TIMING...SNOW WILL BEGIN LATE FRIDAY NIGHT AND WILL CONTINUE
THROUGH SUNDAY MORNING.

* TEMPERATURES...UPPER 20S TO LOWER 30S THROUGH THE EVENT.

* WINDS...10 TO 20 MPH THROUGH THE EVENT...WITH GUSTS OF 25 TO 30
MPH SATURDAY AND SUNDAY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW THAT MAY IMPACT TRAVEL. CONTINUE TO MONITOR THE LATEST
FORECASTS.

&&

$$

KRAMAR/STRONG

[Portastorm]

Yeah, it looks like you folks in the DC/Baltimore area are going to get hammered!

How exciting ... (envious).

[Squarethecircle]

Wow, this is terrific! We haven't had a good snow year in a few years, and now (hopefully) we're getting a second snowfall before January (and a big one).

[brunota2003]

That is an image from the NWS Wakefield of predicted 48 hour snows

http://www.erh.noaa.gov/er/akq/winter/totalsnow.png

My grandmother lives in the county they have the 14.6 on (west side of the map).

[brunota2003]

Wow, this is terrific! We haven't had a good snow year in a few years, and now (hopefully) we're getting a second snowfall before January (and a big one).

And it looks like you'll have another storm system on the way for Christmas!

[Stephanie]

Winter Storm watch for Southern New Jersey:

One product issued by NWS for: 2 Miles E Glassboro NJ
--------------------------------------------------------------------------------


Winter Storm Watch
URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
330 PM EST THU DEC 17 2009

...HEAVY SNOW AND WINDY CONDITIONS ARE LIKELY TO AFFECT OUR AREA
FROM LATER FRIDAY NIGHT INTO OR THROUGH SATURDAY NIGHT...

.DEVELOPING LOW PRESSURE MOVING UP THE COAST FRIDAY NIGHT WILL
BRING POSSIBLY HEAVY SNOW TO OUR AREA LATER FRIDAY NIGHT INTO OR
THROUGH SATURDAY NIGHT. WINDS MAY BE STRONG ESPECIALLY NEAR THE
COAST.

DEZ001>004-MDZ008-012-015-019-020-NJZ016>027-PAZ070-071-180900-
/O.NEW.KPHI.WS.A.0007.091219T0600Z-091220T1100Z/
NEW CASTLE-KENT-INLAND SUSSEX-DELAWARE BEACHES-CECIL-KENT MD-
QUEEN ANNES-TALBOT-CAROLINE-SALEM-GLOUCESTER-CAMDEN-
NORTHWESTERN BURLINGTON-OCEAN-CUMBERLAND-ATLANTIC-CAPE MAY-
ATLANTIC COASTAL CAPE MAY-COASTAL ATLANTIC-COASTAL OCEAN-
SOUTHEASTERN BURLINGTON-DELAWARE-PHILADELPHIA-
INCLUDING THE CITIES OF...WILMINGTON...DOVER...GEORGETOWN...
REHOBOTH BEACH...ELKTON...CHESTERTOWN...CENTREVILLE...EASTON...
DENTON...PENNSVILLE...GLASSBORO...CAMDEN...CHERRY HILL...
MOORESTOWN...MOUNT HOLLY...JACKSON...MILLVILLE...HAMMONTON...
CAPE MAY COURT HOUSE...OCEAN CITY...ATLANTIC CITY...
LONG BEACH ISLAND...WHARTON STATE FOREST...MEDIA...PHILADELPHIA
330 PM EST THU DEC 17 2009

...WINTER STORM WATCH IN EFFECT FROM LATE FRIDAY NIGHT THROUGH
LATE SATURDAY NIGHT...

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY HAS ISSUED A WINTER
STORM WATCH...WHICH IS IN EFFECT FROM LATE FRIDAY NIGHT THROUGH
LATE SATURDAY NIGHT.

LOW PRESSURE WILL INTENSIFY AS IT MOVES UP THE COAST FRIDAY NIGHT
AND AFFECTS OUR AREA LATER FRIDAY NIGHT INTO OR THROUGH SATURDAY
NIGHT. HEAVY SNOW IS POSSIBLE AS THIS NOR/EASTER MOVES JUST TO
THE EAST OF OUR AREA.

WARMER AIR MAY MIX IN FROM THE OCEAN AND CAUSE A MIX OR CHANGE
TO RAIN RIGHT ALONG THE COAST...KEEPING SNOW AMOUNTS LESS THAN
AREAS JUST INLAND. HOWEVER, AS THE STORM PULLS AWAY EVEN THESE
AREAS MAY CHANGE BACK TO ALL SNOW AND RECEIVE HEAVY SNOW AMOUNTS.

THERE IS A POTENTIAL FOR AREAS OF HEAVY SNOW TO COMBINE WITH
GUSTY WINDS TO CAUSE DANGEROUS TRAVEL CONDITIONS SATURDAY AND INTO
SATURDAY NIGHT. WINDS ARE LIKELY TO BE STRONG...ESPECIALLY CLOSER
TO AND AT THE COAST. THIS WILL WORSEN TRAVEL CONDITIONS BY
CAUSING BLOWING AND DRIFTING OF THE SNOW.
A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.

$$

Almost sounds like a blizzard??

[srainhoutx]

Stay safe East Coast Members...

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
436 PM EST THU DEC 17 2009

VALID 00Z FRI DEC 18 2009 - 00Z MON DEC 21 2009


DAY 1...

CAROLINAS TO CENTRAL APPALACHIANS...
A STRENGTHENING GULF OF MEXICO SYSTEM WILL TRACK ACROSS NRN FL AND
NEAR THE SE ATLC COAST FRI...WITH THE MODELS SHOWING AN
ANTICYCLONICALLY CURVED UPPER JET WITH WELL DEFINED DIVERGENCE
ALOFT PROVIDING ASCENT SUPPORT FOR PCPN TO SURGE NWD ACROSS THE
CAROLINAS...WITH SNOW AT HIGHER ELEVATIONS. THE 850 MB JET
INCREASES TO NEAR 50 KT OUT OF THE EAST...RESULTING IN A STRONG
UPSLOPE FLOW IN THE INTERIOR CAROLINAS.
MODELS HAVE TRENDED FASTER...STRONGER...AND FARTHER WEST WITH THE
INTENSIFYING CIRCULATION ALONG THE SE COAST....INCLUDING THE
NAM/GFS AND ECMWF/UKMET...RESULTING IN AN INCREASED THREAT FOR
SIGNIFICANT SNOW. AXIS OF HVST SNOW ASSOCD WITH DEFORMATION ZONE
IS EXPECTED FROM WRN NC AND ACROSS SWRN/CNTRL VA.
MODEL FCST SOUNDINGS SHOW A NEARLY ISOTHERMAL VERTICAL TEMPERATURE
PROFILE IN THE TRANSITION ZONE IN NC/SC...WITH A FEW TEMPORARY
INVERSIONS LEADING TO A MIXTURE OF ICE PELLETS AND LIGHT FREEZING
RAIN. MANUAL PROGS BLENDED THE SREF MEAN AND ECMWF. THE 12Z GFS
WAS GIVEN THE LEAST WEIGHT...WITH THE 12Z GEFS MEMBERS SHOWING A
FURTHER WEST LOW TRACK.


DAY 2...

MID ATLANTIC/ADJACENT APPALACHIANS...
THE MODELS HAVE TRENDED TOWARDS A MORE INTENSE CYCLONE ON DAY
TWO...WITH A WELL DEFINED COUPLED UPPER JET PATTERN DEVELOPING
OVER THE MID ATLANTIC STATES AND HIGH MAGNITUDE AND PERSISTENT
LOWER AND UPPER LEVEL JETS. THE 12-18Z NAM NOW SHOW SNOW OF
HISTORIC PROPORTIONS IN THE CORRIDOR FROM SOUTHWEST VA TO
WASHINGTON DC AND BALTIMORE. THE 12Z ECMWF AND UKMET HAVE SHARPLY
INCREASED AMOUNTS FROM PRIOR RUNS...AS HAVE THE 12Z GEFS MEMBERS.
THE 12Z GFS BECAME AN EASTERN OUTLIER WITH THE CYCLONE TRACK...SO
ITS LOWER AMOUNTS WERE GIVEN LESS WEIGHT. THE MANUAL PROGS
BLENDED THE HEAVIER ECMWF/UKMET/09Z SREF MEAN/12Z GEFS MEAN. THE
MORE INTENSE CYCLONE AND HIGHER AMPLITUDE DOWNSTREAM MID LEVEL
RIDGE HAS LED TO A FURTHER WEST DRIFT IN THE RAIN-SNOW TRANSITION
LINE IN VA/MD...SO LATER FORECASTS WILL HAVE TO WATCH THE
POTENTIAL FOR THIS TRANSITION ZONE TO CONTINUE TO CHANGE. THE
GREATEST PRECIPITATION POTENTIAL CAME OUT OF THE 18Z NAM...WHICH
WOULD RESULT IN A POTENTIAL FOR UP TO 3 FEET OF SNOW IN PARTS OF
NORTHERN VA AND CENTRAL MD/WASHINGTON DC. A HIGH RISK OF A FOOT
WAS SHOWN WHERE THE BEST OVERLAP OF SUFFICIENT QPF WHERE TEMPS ARE
COLD ENOUGH FOR SNOW AMONG THE 12-18Z NAM/12Z ECMWF/12Z UKMET/12Z
GEFS MEAN/09Z SREF MEAN IN INTERIOR VA.


DAY 3...

THE 09Z SREF/12Z GEFS MEMBERS/12Z UKMET/12Z ECMWF LED A BIG CHANGE
TO FORECAST THE CYCLONE TO TRACK FURTHER WEST TO THREATEN
NY/SOUTHERN NEW ENGLAND WITH HEAVY SNOW. THE 18Z NAM HAS JOINED
THIS CLUSTER...MOVING ITS 12Z RUN FORECAST SURFACE LOW ABOUT 250
NM FURTHER WEST AS OF 12Z SUNDAY. THIS INCREASES THE ODDS THE 12Z
GFS WOULD BE A LOW PROBABILITY SOLUTION...GIVEN THE NCEP ENSEMBLE
MEAN LOWS CLUSTER WITH A MAJORITY OF MEMBERS SHOWING A FURTHER
WEST SFC-500 MB CYCLONE AND MORE PRECIPITATION OCCURRING IN
NJ/NY/SOUTHERN NEW ENGLAND. THE 12Z-18Z NAM/00-12Z ECMWF/12Z
UKMET AND SEVERAL SREF/GEFS MEMBERS ALSO SHOW A SURFACE LOW
DROPPING BELOW 980 MB...PRESENTING A POSSIBILITY OF A MAJOR SNOW
STORM. PROBABILITIES ACROSS ALL THRESHOLDS ARE SHOWN TO ACCOUNT
FOR SIGNIFICANT MODEL TO MODEL AND RUN TO RUN CHANGES.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

PETERSEN

[Brent]

WOW, this is nothing short of EPIC if this verifies. We're talking top of the line BLIZZARD.

[Stephanie]

The Megalopolis will be crippled - the final shopping weekend before Christmas!

[WeatherLovingDoc]

WaPo this morning suggests 6 to 12 inches. Just bumping this thread for my S2K friends current thoughts.

Yes Stephanie, there is a Santa Claus in Virginia, but will all the children get their anticipated delights?

Off to shopping this am if you know what I mean.

[cpdaman]

and then the 06Z nam and 0Z ecwmf shifted well SOUTH EAST and said not so fast for philly, NYC, Prov-Bos!

so looks like a mid atlantic event primarily to me now.....with the potential (although lowering and lower than last nite) for Heavy snow making it thru the NYC-Bos corridor

next two runs of the euro will have SNE snow lovers praying.....those prayers could have been answered with some run to run consitency last nite by the euro but nope...SE trend ......now we need a NW trend and then some consistency .....not betting the house on that

The soundings for areas in the carolina's are borderline on the interior piedmont.......could be historic snow or just a slushy mess interesting to see where that line occurs.....in winston salem.....raleigh area.....charlotte....

where D sutherland when you need him? lol

[srainhoutx]

HPC thoughts this morning. I will add that folks in NYC into SNE should keep an eye on things as storm track adjustments may be warranted as new guidance comes in today. I do agree that the greatest threat appears to be for the Mid Atlantic Areas. Folks in W NC, VA, and MD could receive amounts in the 12+ range IMHO. Stay Sake Folks.

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
527 AM EST FRI DEC 18 2009

VALID 12Z FRI DEC 18 2009 - 12Z MON DEC 21 2009


DAYS 1...

CAROLINAS TO MID ATLANTIC REGION AND ADJACENT APPALACHIANS

AN AREA OF LOW PRESSURE OVER THE NORTHERN GULF OF MEXICO WILL BE
INTENSIFYING/DEEPENING AS IT MOVES NORTHEAST ACROSS THE FL
PENINSULA AND OUT OVER THE WATERS OF THE WESTERN ATLANTIC OFF THE
CAROLINA COAST BY 19/12Z. THE MODELS ARE SHOWING GOOD DIVERGENCE
ASSOCIATED WITH THE EQUATORIAL ENTRANCE REGION OF AN UPPER LEVEL
JET THAT LIFTS ACROSS THE SOUTHEAST AND MID ATLANTIC REGION BY
EARLY SATURDAY MORNING...AS SPEEDS IN THE CORE ACCELERATE FROM
AROUND 120 KTS EARLY ON INTO THE 145 TO 155 KTS RANGE. SFC
CYCLOGENESIS IS FORECAST TO BE MOST INTENSE AFTER 19/06Z AS THE
DIVERGENCE ON THE NORTHERN SIDE OF A SUBTROPICAL JET GETS EASES
NORTHWARD AND INTO A COUPLED CONFIGURATION WITH THE JET STREAK TO
THE NORTH. THIS LEADS TO INCREASING STRONGER ONSHORE/UPSLOPE FLOW
FROM THE CAROLINAS INTO THE MID ATLANTIC REGION. INITIALLY...SNOW
SHOULD BE IN THE HIGHER ELEVATIONS OF THE MIDDLE PART OF THE
APPALACHIANS TO THE PIEDMONT...BUT STRONG UVV ASSOCIATED WITH THE
COUPLED JET HELPS TURN ANY LIQUID PCPN TO SNOW ACROSS THE MID
ATLANTIC REGION OVER MUCH OF THE MID ATLANTIC. THE 18/00Z NAM
FITS WELL WITH THE DEPTH/SPEED/INTENSITY OF THE SYSTEM AS SHOWN BY
THE 17/12Z ECMWF. THE GFS MAINTAINED GOOD CONTINUITY WITH ITS
17/12Z AND 17/18Z RUNS WHICH WAS FLATTER THAN THE NAM/EC. MANUAL
PROGS GAVE SOMEWHAT MORE WEIGHT TOWARDS THE NAM/ECMWF SOLN SINCE
OTHER MODELS WERE TENDING THAT WAY...ALTHOUGH SNOWFALL AMOUNTS IN
THE MID ATLANTIC REGION WERE SCALED BACK FROM THE AMOUNTS IMPLIED
BY THE LIQUID QPF IN PART DUE TO THE POSSIBILITY OF WARM AIR
ENTRAINING INTO THE SYS FROM THE EAST.
THIS ALSO SETS UP THE POSSIBILITY OF SOME LIGHT FREEZING RAIN OR
ICE PELLETS SINCE FORECAST SOUNDINGS STILL SHOW NEARLY ISOTHERMAL
LAYERS THAT CAN BRIEFLY TAKE ON INVERSIONS WHICH LOOK TO BE
SUFFICIENTLY DEEP TO ALLOW FOR MELTING FROM THE CENTRAL/SOUTHERN
PART OF THE APPALACHIANS...ACROSS WESTERN/NORTHERN NC INTO SRN VA.


DAY 2...

MID ATLANTIC TO NORTHEAST/SRN NEW ENGLAND...

A DEEPENING SFC LOW SHOULD BE TRACKING TOWARDS THE NORTH AND EAST
DURING THE PERIOD IN ASSOCIATION WITH A COUPLED UPPER JET PATTERN
AND HIGH MAGNITUDE/PERSISTENT UPPER AND LOWER JETS. SOME RATHER
SIGNIFICANT DIFFERENCES HAVE OPENED UP IN THE MODEL LOW TRACKS AND
PCPN AMOUNTS/COVERAGE IN THE 18/00Z MODEL PRODUCTION CYCLE. THE
18/00Z NAM WAS MOST AGGRESSIVE TAKING THE SFC LOW UP THE COAST AND
CONTINUED TO SHOW VERY HI QPF VALUES WHEN COMPARED WITH THE
ECMWF/CANADIAN/UKMET/GFS. THE 18/00Z ECMWF AND 18/00Z GFS BOTH
BROUGHT THE SFC LOW ROUGHLY UP TO CAPE HATTERAS AND THEN TOOK THE
LOW ON A MORE EASTERLY PATH RATHER UNLIKE THE NAM WHICH KEPT THE
LOW MOVING NORTHEAST. ONE FACTOR WHICH APPEARED TO FAVOR THE NAM
WAS THE WAY THAT ITS SFC LOW TENDED TO FOLLOW THE WEST WALL OF THE
GULF STREAM TEMPERATURES...A CLIMATOLOGICALLY FAVORED REGION FOR
STORMS. THE GFS/ECMWF IDEA OF CURVING A DEEPENING SNOW SOUTH AND
EAST OF THE BENCHMARK IS LESS STRONGLY SUPPORTED BY CLIMATOLOGY.
HAVING SAID THAT...BOTH THE 18/00Z GFS AND 18/00Z ECMWF TOOK THE
SFC OUT TO SEA MORE QUICKLY WHICH RESULTED IN LESS QPF FROM NY
INTO SRN NEW ENGLAND WHEN COMPARED WITH PREVIOUS RUNS. THERE WERE
ENOUGH ENSEMBLE MEMBERS WHICH PRODUCED ENOUGH PCPN TO KEEP A RISK
OF 4 INCHES EXTENDING INTO SRN NEW ENGLAND DESPITE THE OPERATIONAL
MODELS TENDING TO SHOW SCANT PCPN. GIVEN THE SPREAD...THERE IS
CERTAINLY ROOM FOR A SOLN SOMEWHERE BETWEEN THE NAM AND THE
GFS/ECMWF SOLN. WE TENDED TO SHOW THE BEST POTENTIAL ALONG THE
AXIS OF 18/00Z NAM PCPN. THE 18/06Z NAM SHIFTED ITS AXIS FURTHER
SOUTH TO TAKE ON A 00Z GFS/ECMWF LOOK...WHILE THE 18/06Z GFS
BROUGHT A STRIPE NORTHEAST INTO PARTS OF SRN/ERN NEW ENGLAND. SO
DESPITE GOOD AGREEMENT IN THE OVERALL IDEA...SOME IMPORTANT
DETAILS STILL NEED TO BE RESOLVED. WE INITIALLY USED 00Z NAM AND
21Z SREF FOR PCPN ALTHOUGH SOME MODIFICATIONS WERE MADE TO ACCOUNT
FOR THE SHIFT IN THE 06Z OPERATIONAL GUIDANCE. OF PARTICULAR
NOTE...A QUICK LOOK AT THE 00Z ECMWF ENSEMBLE MEAN PCPN DOES NOT
GIVE MUCH SUPPORT FOR THE OPERATIONAL ECMWF/GFS IDEA OF SWEEPING
THE PCPN OUT TO SEA.
THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

DAY 3...

EASTERN U.S....

THE DEEP LOW WILL START TO MOVE AWAY FROM THE US COASTLINE DURING
THE PERIOD...BRINGING
AND END TO THE SNOW. DESPITE THE 00Z OPERATIONAL MODELS THAT
WANTED TO SWEEP THE LOW EASTWARD AND ITS PCPN OUT TO SEA...WE
INCLUDED A RISK OF HEAVY SNOW IN PARTS OF NEW ENGLAND GIVEN
ONSHORE FLOW AROUND THE SFC LOW. WHILE THERE ARE NOT A LOT OF
ENSEMBLE MEMBER THAT SUPPORT THIS IDEA...ANALOGS TO A PREVIOUS
STORM WITH SIMILAR UPPER AIR PATTERNS SHOWED THAT MENTIONING A
RISK WAS STILL WARRANTED. PROBABILITIES ACROSS ALL THRESHOLDS ARE
SHOWN TO ACCOUNT FOR SIGNIFICANT MODEL TO MODEL AND RUN TO RUN
CHANGES.

NORTHWEST...

MOIST ONSHORE FLOW AHEAD OF AN AREA OF LOW PRESSURE OVER THE ERN
NOPAC SHOULD BRING A RISK OF 4 TO 8 INCHES OF SNOW MAINLY TO THE
HIGHER ELEVATIONS OF THE CASCADES EARLY ON DAY 3 WHICH THEN
GRADUALLY SHIFTS EASTWARD INTO THE NORTHERN ROCKIES AFTER 21/00Z.


THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

BANN

http://www.srh.noaa.gov/nat_hazard.php

[srainhoutx]

09Z SREF 24 Hour Precip Loop...


http://www.nco.ncep.noaa.gov/pmb/nwprod ... loop.shtml

2 meter Temp Loop

http://www.nco.ncep.noaa.gov/pmb/nwprod ... loop.shtml