East Coast blizzard 12/15-12/17/07

[ROLLTIDE]

http://www.cpc.noaa.gov/products/predictions/threats/p_threats.gif

[srainhoutx]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1244 PM EST WED DEC 12 2007

VALID 12Z SAT DEC 15 2007 - 12Z WED DEC 19 2007

THE FINAL HPC FORECAST REMAINS DERIVED FROM THE DETAILS OF THE 00Z
ECMWF FOR DAYS 3-7/SAT-WED...WITH CONTINUITY AND CONSENSUS OF THE
BULK OF MODEL AND ENSEMBLE GUIDANCE GENERALLY OFFERING REASONABLY
GOOD SUPPORT. WE STILL SEE NO COMPELLING REASON TO CHANGE
CONTINUITY.

GUIDANCE IS STILL IN THE PROCESS OF CONVERGING WITH THE VIGOROUS
STORM EXPECTED TO AFFECT THE ERN HALF OF THE CONUS DURING THE
WEEKEND AND INTO MON. THIS STORM OFFERS A SIGNIFICANT WINTER
WEATHER THREAT FROM THE S-CENTRAL US NEWD TO NEW ENG. THE 00Z
ECMWF HAS ADJUSTED SOMEWHAT FASTER THAN ITS PAST COUPLE OF RUNS
AND THE 00Z CANADIAN REMAINS SLOWER THAN THE GFS. THE 12 UTC
CANADIAN OFFERS A MORE NWWD TRACK...BUT THE 12 UTC GFS AND UKMET
SUPPORT THE ECMWF. THE 12 UTC NAM SEEMS WAY SLOW. 00 UTC GFS
SPECIFICS ARE STILL SOMEWHAT IN DOUBT AS THE MODEL HAS A
QUESTIONABLE SHORT-MEDIUM RANGE EVOLUTION OF THE UPSTREAM SYSTEM.
ALONG THE EAST COAST THE 00Z GEFS/12Z ECMWF ENSEMBLE MEANS REMAIN
FARTHER EWD THAN THE OPERATIONAL MODELS BUT HAVE TRENDED TOWARD
THE OP CLUSTER. SMALL SCALE DETAIL ISSUES NOT EASILY RESOLVED 3-4
DAYS OUT IN TIME COULD STILL ALTER THE TRACK...BUT FOR NOW
CONTINUE TO PREFER THE OP MODELS SINCE ENSEMBLE GUIDANCE HAS BEEN
KNOWN TO TAKE LONGER TO CATCH ONTO COASTAL DEVELOPMENT.

MEANWHILE...MOST GUIDANCE CONTINUES TO SHOW BETTER THAN AVERAGE
AGREEMENT AND CONTINUITY WITH THE EVOLUTION OF THE MEAN TROF FCST
TO DEVELOP OVER THE ERN PACIFIC/WEST COAST...THE THE 12 UTC GFS
HAS CERTAINLY BECOME A MORE PROGRESSIVE OUTLIER. OTHERWISE...ONE
WET SYSTEM SHOULD REACH THE WEST COAST SUN-MON WITH ANOTHER
FOLLOWING TUE-WED. SOME EMBEDDED TIMING/DETAIL DIFFS ALSO REMAIN
WITH THESE SYSTEMS...BUT THEY ARE GENERALLY OF A MAGNITUDE NOT
MUCH GREATER THAN TYPICALLY SEEN FOR 2-3 DAY FCSTS. ONE ITEM OF
NOTE WITH THE DAYS 6-7/TUE-WED SYSTEM IS THAT MULTI-DAY MEANS AT
THAT TIME WHICH SHOW THE CORE OF NEGATIVE MID LEVEL HEIGHT
ANOMALIES NEAR THE ALASKA PANHANDLE FAVOR THE ECMWF/CANADIAN WHICH
TRACK THE SYSTEM SOMEWHAT FARTHER NORTHWARD THAN THE GFS.

BETWEEN THE STRONG ERN SYSTEM AND THE ERN PAC/WEST COAST MEAN
TROF... FLOW SHOULD BE OF FAIRLY LOW AMPLITUDE. TELECONNECTIONS
RELATIVE TO THE PACIFIC MEAN RIDGE/ERN PAC TROF BY THE LATTER HALF
OF THE PERIOD YIELD ABOVE NORMAL HGTS OVER THE EAST BUT A HINT OF
WEAK MEAN TROFFING. MODELS GO ALONG WITH THIS IDEA AS ENERGY
PROGRESSES THRU THE CNTRL/ERN STATES SUN-MON. UNCERTAINTY IS HIGH
WITH DETAILS THOUGH. AS MENTIONED EARLIER GFS DETAILS ARE
QUESTIONABLE AS FAR BACK AS THE SHORT RANGE... AND BY SUN-MON
APPEARS TOO DEEP WITH ITS MID LVL SYSTEM FOR A TRACK THAT IS
FARTHER S THAN THE ECMWF. SOME ENERGY EXITING THE ERN PAC MEAN
TROF MAY REACH EWD BY TUE-WED BUT MODELS/ENSEMBLES ARE UNDECIDED
OVER WHETHER IT WILL BE STRONG ENOUGH TO HAVE A SFC REFLECTION.

RAUSCH/SCHICHTEL

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

[srainhoutx]

Looks as if we will see two events the next few day for the NE. HPC precip maps are impressive...

http://www.hpc.ncep.noaa.gov/medr/95e00wbg.gif

Current Weather Hazards:
http://www.srh.noaa.gov/nat_hazard.php

[srainhoutx]

Lastest from HPC concerning BIG Mess across a lot of real estate...

SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
252 PM EST FRI DEC 14 2007

VALID 00Z SAT DEC 15 2007 - 12Z SUN DEC 16 2007

A STRONG WINTER STORM IS FORECAST TO IMPACT A LARGE SECTION OF THE
COUNTRY THIS WEEKEND EXTENDING FROM THE CENTRAL PLAINS INTO THE
OHIO VALLEY AND NORTHEAST. THE STORM SYSTEM IS CURRENTLY
ORGANIZING ACROSS TEXAS AS A DEEP UPPER LEVEL LOW STRENGTHENS OVER
THE SOUTHERN ROCKIES. SNOW THAT IS CURRENTLY FALLING ACROSS THE
CENTRAL PLAINS WILL INCREASE IN COVERAGE AND SPREAD EAST TONIGHT.
SNOWFALL TOTALS OF UP TO 8 INCHES ARE EXPECTED THROUGH SATURDAY
ACROSS PORTIONS OF EASTERN KANSAS INTO CENTRAL MISSOURI. AS LOW
PRESSURE AT THE SURFACE TRACKS NORTHEASTWARD INTO OHIO...LOW LEVEL
SOUTHERLY FLOW AHEAD OF THE SYSTEM WILL TAP WARM...MOIST AIR FROM
THE GULF OF MEXICO WHICH WILL COMBINE WITH MOISTURE FROM THE
REMAINS OF TROPICAL STORM OLGA OVER THE YUCATAN PENINSULA. THIS
ADDITIONAL MOISTURE WILL ALLOW FOR HEAVY RAIN AND THUNDERSTORMS
ACROSS FLORIDA...SOUTHEASTERN GEORGIA AND INTO EASTERN PORTIONS OF
THE CAROLINAS. FURTHER NORTH...COLD AIR WILL BE TRAPPED AT THE
SURFACE EAST OF THE APPALACHIANS WHICH WILL CAUSE SIGNIFICANT
FREEZING RAIN ACCUMULATIONS ACROSS THE SHENANDOAH VALLEY IN
WESTERN VIRGINIA AND SOUTHERN PENNSYLVANIA THROUGH SUNDAY. UPSTATE
NEW YORK AND NEW ENGLAND WILL SEE MOSTLY SNOW FROM THIS SYSTEM
WHICH SHOULD EASILY LEAD TO SNOWFALL ACCUMULATIONS OVER A FOOT IN
THESE AREAS. THE FRIGID AIR CURRENTLY IN PLACE ACROSS THE NORTHERN
PLAINS WILL BE PULLED SOUTH AS THE COLD FRONT ASSOCIATED WITH THE
WINTER STORM MOVES WELL INTO THE GULF OF MEXICO. THIS WILL LIMIT
HIGH TEMPERATURES ACROSS MUCH OF THE CENTRAL PORTION OF THE U.S.

NO CHANGE IS IN STORE FOR THE SOUTHWEST AS DRY CONDITIONS ARE
EXPECTED TO CONTINUE THROUGH THIS WEEKEND. FURTHER NORTH
HOWEVER...A ONE TWO PUNCH OF SYSTEMS WILL IMPACT THE PACIFIC
NORTHWEST. THE FIRST WILL COME TONIGHT...AS A MATURE OCCLUDED
CYCLONE REACHES THE WEST COAST AND DISSIPATES SHORTLY THEREAFTER.
WIDESPREAD LIGHT TO MODERATE RAIN WITH HIGHER ELEVATION SNOW CAN
BE EXPECTED ALONG THE WEST COAST FROM OREGON...NORTHWARD INTO
BRITISH COLUMBIA. THE SECOND SYSTEM WILL APPROACH THE AREA
BEGINNING SATURDAY NIGHT BRINING THE SECOND ROUND OF WET WEATHER
TO THE COAST.

RELATIVELY QUIET WEATHER IS EXPECTED ELSEWHERE AS THE EAST COAST
AND WEST COAST WILL BE SEEING THE ACTION THIS WEEKEND.

OTTO

GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV

[TallahasseeLassie]

they have changed my forcast like 12 times in the ast 24 hours!!!
lord

[srainhoutx]

they have changed my forcast like 12 times in the ast 24 hours!!!
lord

Looking at Lastest NAM and NOGAP as compared to GFS, it will be a close call for SE New England. NAM and NOGAP shows a storm track offshore, while GFS shows a more inland Storm Track. Will be watching for changes...

[Race2Beach]

http://www.crh.noaa.gov/images/fxc/iwx/wx/File.png

A significant winter storm will affect the area this weekend. Heavy snow and strong winds of 20 to 30 mph will result in blowing and drifting snow and visibilities near zero at times. Snow will begin across the area today but will really increase in intensity tonight into Sunday morning...then end from west to east Sunday afternoon. Travel is discouraged from late this afternoon through Sunday morning due to the heavy snow and strong winds that may result in closed roads and could potentially strand travelers.

[Race2Beach]

Urgent - Winter Weather Message
National Weather Service Northern Indiana
508 Am Est Sat Dec 15 2007

...major Winter Storm For Today And Sunday...

.a Winter Storm System Will Move Out Of East Texas Today...and Into
South Central Ohio By Early Sunday. This Strong System Will
Rapidly Intensify As It Lifts Northeast Into The Ohio Valley And
Will Produce Significant Snowfall Amounts Of 6 To 12 Inches With
Locally Heavier Amounts.

Snowfall Will Develop Across The Area This Morning And Increase
In Intensity This Evening. As This Winter Storm Intensifies...
Winds Are Expected To Increase Tonight And Sunday. North To
Northeast Winds Of 20 To 30 Mph With Gusts To 40 Mph Will Cause
Blowing And Drifting Snow. The Snow Will Gradually Taper Off From
West To East Sunday Afternoon.

If Travel Is Planned Through The Great Lakes And Ohio Valley
Region This Weekend...you Are Urged To Stay Abreast On The Latest
Forecasts And Statements Concerning This Major Winter Storm.

[Race2Beach]

http://www.hpc.ncep.noaa.gov/wwd/day1_psnow_gt_04.gif

[Race2Beach]

http://www.hpc.ncep.noaa.gov/wwd/day2_psnow_gt_04.gif

[Race2Beach]

Probabilistic Heavy Snow And Icing Discussion
Nws Hydrometeorological Prediction Center Camp Springs Md
352 Am Est Sat Dec 15 2007

Valid 12z Sat Dec 15 2007 - 12z Tue Dec 18 2007


Day 1 And 2...

A Significant Winter Weather Event Is Expected To Exit The Plains
And Reach Across The Northeast With A Variety Of Precipitation
Types. A Potent Trof Progressing Out Of The Srn Plains Will
Evolve Into A Closed Low Over Oh And The Lower Great Lakes Area.
An Evolving 7h Comma Head Is Fcst To Reach From Mo To Oh And
Spread A Batch Of Snow Ewd Today. The Axis Of Hvy Snow With
Possible 6 Inch Plus Amts Is Expected To Stretch In The
Deformation Zone Across Cntrl Il And Nrn In To Nwrn Oh And Srn
Lower Mi....south Of This Region Soundings Indicate A Change To
Sleet/freezing Rain And Some Rain Especially Over Oh And Srn In.
As The Sfc Low Reaches Into Oh...hvy Snow Should Set Up West Of
The Circulation In The Wraparound Area Before The System Weakens
And Pulls Northeast. From Oh To The Mid Atlc And
Northeast...overall...models Have Trended Warmer Over The Last Few
Runs. The Gfs Sfc Track Is Slightly Farther West With The Coastal
Low....while The Nam Bl And 85h Temps Have Warmed Substantially.
Indeed...layers Of Warm Air Aloft Should Intrude Into A Large
Portion Of The Northeast As The Very Strong Sfc Low Reaches Into
Ohio...while The Forming Coastal Low Tracks Inland From Nj To Ern
New Eng. The Result Should Be Hvy Snow Changing To Sleet For A
Time From Ny/pa To Cntrl/nrn New Eng. The Only Areas That May
Remain All Snow Should Be Close To The Canadian Border From
Upstate Ny To Nrn Maine...where Some 12 Inch Plus Amts Are Still
Expected. The Gfs And Nam Both Indicate A Warm Layer At 7h
Slicing Thru The Interior Northeast Which Should Bring At Least A
Few Hours Of Sleet To Many Areas. After A Period Of
Snow/sleet...very Strong Onshore Flow Will Result In Warming Bl
Temps And A Change To Rain Along The Northeast Coast. Low Level
Cold Air Should Persist Closer To The Appalachians...nam And Gfs
Support An Area Of Freezing Rain Centered On Ern Wv...wrn Va/md To
Portions Of Pa...where Localized .25 Inch Plus Icing Amts Are
Possible.

Northwest...
Fast Flow Acrs The Nrn Pac Will Bring A Couple Of Moist Systems
Across The Pac Nw And Nrn Intermountain Region Over The Next 2
Days. Accompanying Onshore Flow Will Produce Widespread
Orographic Snows From The Olympics/cascades Ewd Into The The Nrn
Rockies. Initial System Will Lift Across The Nrn Rockies And
Weaken Today. The Next And Stronger Pac Trof Will Swing Onshore
Sun Night Along With A Frontal Bndry. Best Threat For 12 Inch
Plus Snow Amts Will Be Across The Wa And Oregon Cascades As The
Onshore Flow And Jet Energy Focus On The Region.

Day 3...

Northwest And Ca...
Another Trof Will Approach The West Coast Along With A Potentially
Strong Sfc Low By Early Tues. Model Diffs Are Evident...but This
System Is Fcst To Reach Farther South Than The Previous Trofs And
Bring A Threat For Locally Hvy Snow Not Only Into The Cascades But
Swd Into The Nrn And Possibly Cntrl Ca Sierra. A Gfs/ecmwf Blend
Is Used...with Onshore Flow Reaching Into Nrn Ca... And A Threat
For 8 Inch Plus Amts Is Indicated Across The Favored Orographic
Locations.

[Race2Beach]

http://www.spc.noaa.gov/products/md/mcd2224.gif


MESOSCALE DISCUSSION 2224
NWS STORM PREDICTION CENTER NORMAN OK
1151 AM CST SAT DEC 15 2007

AREAS AFFECTED...MUCH OF OHIO...FAR SERN IN

CONCERNING...WINTER MIXED PRECIPITATION

VALID 151751Z - 152345Z

MDT TO HEAVY SNOW WILL SPREAD FROM SERN IN/SWRN OH INTO CNTRL AND N
CNTRL OH THROUGH 00Z. PORTIONS OF SRN OH AND SERN IN WILL CHANGE TO
RAIN...WITH SOME AREAS NEAR THE TRANSITION ZONE RECEIVING PERIODS OF
FREEZING RAIN.

LARGE SHIELD OF WARM ADVECTION PRECIPITATION WILL PERSIST WITH HRLY
LIQUID RATES AVERAGING 0.05 TO 0.20 IN/HR. SNOW WILL BE THE DOMINANT
TYPE OVER N CNTRL OH...WHERE COOLER AIR EXISTS. TO THE S...LOW LEVEL
JET/WARM CONVEYOR WILL CONTINUE TO INCREASE IN INTENSITY AND WILL
RESULT IN WARMING TEMPERATURES ALOFT CENTERED NEAR 850 MB. THIS WILL
RESULT IN A WARM LAYER ALOFT AND MELTING HYDROMETEORS. THUS...WHILE
MDT TO HEAVY SNOWFALL RATES WILL OCCUR INITIALLY...A GRADUAL
CHANGEOVER TO RAIN IS EXPECTED THROUGH 00Z. AREAS THAT MANAGE TO
MAINTAIN LOCALLY SUB-FREEZING SURFACE TEMPERATURES NEAR THE
CHANGEOVER ZONE COULD SEE PERIODS OF FREEZING RAIN.

..JEWELL.. 12/15/2007


...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.

ATTN...WFO...PBZ...RLX...CLE...ILN...IWX...IND...

[ROLLTIDE]

MESOSCALE DISCUSSION 2227
NWS STORM PREDICTION CENTER NORMAN OK
0629 PM CST SAT DEC 15 2007

AREAS AFFECTED...MO...IL...IN...MI

CONCERNING...HEAVY SNOW

VALID 160029Z - 160630Z

WIDESPREAD SNOW WILL CONTINUE TO INCREASE IN INTENSITY ACROSS AREAS
OF THE MIDWEST THROUGH LATE TONIGHT AS A STRONG DEEP-LAYER CYCLONE
TRACKS ACROSS THE REGION. SNOWFALL RATES...PEAKING AT ABOUT 1 INCH
PER HOUR...ARE FORECAST IN A SOUTHWEST TO NORTHEAST BAND FROM ERN
MO...ACROSS CNTRL AND NRN IL...TO NWRN INDIANA AND SWRN LOWER MI
OVER THE NEXT SEVERAL HOURS. SOME AREAS WITHIN THIS CORRIDOR COULD
EXPERIENCE THESE PEAK SNOWFALL RATES FOR ABOUT 2-4 HOURS.

MIDWEST SNOWSTORM WAS WELL UNDERWAY THIS EVENING WITH 120KT MID
LEVEL JET AND NEGATIVE TILT SHORT WAVE TROUGH OVER THE LOWER MS
VALLEY SPURRING DEEP SURFACE CYCLOGENESIS ACROSS THE LOWER OH
VALLEY. MID/UPPER LEVEL BAROCLINIC LEAF STRUCTURE HAS RECENTLY
APPEARED IN SATELLITE IMAGERY WITHIN THE LARGER SCALE TROUGH AXIS
AND THE COOLING CLOUD TOPS OF THIS FEATURE INDICATE LOW THROUGH MID
LEVEL UVV IS INTENSIFYING FROM ERN MO TO NRN IL. MESOSCALE FORCING
FOR ASCENT WITHIN THIS ZONE WILL BE FURTHER SUPPORTED BY INTENSE AND
STRENGTHENING FRONTOGENESIS AS THE MID LEVEL LOW TRACKS NEWD ALONG
TIGHT THERMAL GRADIENT.

MODEL GUIDANCE APPEARS TO DEPICT THE SHORT-TERM FORECAST SITUATION
WELL WITH HIGHEST QPF AMOUNTS CORRESPONDING WITH THE DEVELOPING SW
TO NE BAND OF STRONGER FORCING ASSOCIATED WITH THE MID LEVEL LOW
TRACK. HOWEVER...SUB-GRID SCALE PRECIPITATION BANDING AND
ENHANCEMENT APPEARS LIKELY IN THIS PATTERN AND QPF AMOUNTS MAY BE
UNDER FORECAST ON THE MESOSCALE. THERE ALSO APPEARS TO BE SOME
POTENTIAL FOR EITHER VERY ISOLATED UPRIGHT CONVECTION...OR
SLANT-WISE CONVECTION...GIVEN LAYERS OF WEAK MOIST EPV AND POCKETS
CONDITIONAL INSTABILITY COINCIDENT WITH THE INTENSIFYING
FRONTOGENESIS. THUS...WHILE 1 INCH PER HOUR RATES APPEAR
LIKELY...SOME LOCALLY HIGHER CONVECTIVE SNOWFALL RATES ARE NOT OUT
OF THE QUESTION AS THE SNOWSTORM TRAVERSES THE REGION TONIGHT.

..CARBIN.. 12/16/2007


...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.

ATTN...WFO...IWX...GRR...IND...LOT...ILX...LSX...D VN...

http://www.spc.noaa.gov/products/md/mcd2227.gif

[ROLLTIDE]

MESOSCALE DISCUSSION 2228
NWS STORM PREDICTION CENTER NORMAN OK
0643 PM CST SAT DEC 15 2007

AREAS AFFECTED...FAR SRN NY...MUCH OF PA...WRN MD...NRN AND WRN
VA...ERN WV

CONCERNING...WINTER MIXED PRECIPITATION

VALID 160043Z - 160645Z

A MIX OF FREEZING RAIN...SLEET AND SNOW WILL INCREASE ACROSS THE
AREA THROUGH THE EVENING. POCKETS OF SIGNIFICANT ICING WILL BE
POSSIBLE...ALONG WITH MDT TO HEAVY SLEET.

BROAD ZONE OF WARM ADVECTION PERSISTS AHEAD OF DEEPENING SURFACE LOW
WITH INCREASING RADAR RETURNS MOVING NWD OUT OF WV/VA. SURFACE
ANALYSIS SHOWS FREEZING LINE EXTENDS SWWD OUT OF ERN PA INTO THE ERN
APPALACHIANS WITH COLD AIR DAMMING. MEANWHILE...00Z RNK SOUNDING
SHOWS A FAVORABLE PROFILE FOR FREEZING RAIN AS DOES THE IAD SOUNDING
GIVEN EXPECTED LOW LEVEL EVAPORATIVE COOLING. TO THE N...PROFILES
FROM SOUTH CNTRL PA N WERE ENTIRELY BELOW FREEZING AS OF 00Z.

CONTINUED ISENTROPIC LIFT WILL RESULT IN PRECIPITATION RATES
INCREASING TO 0.05 - 0.10 IN/HR IN GENERAL. FREEZING RAIN WILL BE A
PROBLEM MAINLY FROM FAR SRN PA...WRN MD SWD ALONG THE WV/VA BORDER
TOWARD RNK. THE PREDOMINATE PRECIPITATION TYPE WILL BE SLEET...SOME
HEAVY...ACROSS CNTRL PA. A CHANGE FROM MDT SNOW TO A MIXTURE OF
SLEET AND SNOW WILL OCCUR OVER NRN PA INTO FAR SRN NY BY 06Z AS WARM
NOSE NEAR 800 MB MIGRATES N.

http://www.spc.noaa.gov/products/md/mcd2228.gif