Thrusday Night Storm

[Jason234]

Didn't the watch just end...

Winter Storm Watch
URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE UPTON NY
251 PM EST WED FEB 23 2005

...WINTER STORM WATCH IN EFFECT FROM LATE THURSDAY AFTERNOON UNTIL
AROUND DAYBREAK FRIDAY MORNING...

.A DEVELOPING AREA OF LOW PRESSURE IS FORECAST TO MOVE OFF THE COAST
OF NORTH CAROLINA ON THURSDAY BRINGING SNOW TO THE TRI-STATE AREA BY
LATE THURSDAY AFTERNOON. THE SNOW SHOULD CONTINUE THURSDAY NIGHT AS
THE LOW PASSES TO OUR SOUTH. THE SNOW WILL THEN TAPER OFF AND END
EARLY FRIDAY MORNING AS THE LOW TRACKS TO OUR EAST.

CTZ007>012-NYZ071>081-240400-
BRONX NY-KINGS (BROOKLYN) NY-NASSAU NY-NEW YORK (MANHATTAN) NY-
NORTHEAST SUFFOLK NY-NORTHERN MIDDLESEX CT-NORTHERN NEW LONDON CT-
NORTHWEST SUFFOLK NY-QUEENS NY-RICHMOND (STATEN IS.) NY-
SOUTHEAST SUFFOLK NY-SOUTHERN FAIRFIELD CT-SOUTHERN MIDDLESEX CT-
SOUTHERN NEW HAVEN CT-SOUTHERN NEW LONDON CT-SOUTHERN WESTCHESTER NY-
SOUTHWEST SUFFOLK NY-
251 PM EST WED FEB 23 2005

...WINTER STORM WATCH IN EFFECT FROM LATE THURSDAY AFTERNOON UNTIL
AROUND DAYBREAK FRIDAY MORNING...

THE NATIONAL WEATHER SERVICE IN UPTON NY HAS ISSUED A WINTER STORM
WATCH.

SNOW IS EXPECTED TO EDGE INTO THE TRI-STATE REGION BY LATE THURSDAY
AFTERNOON WITH THE GREATEST THREAT COMING THURSDAY NIGHT. THE TRACK
OF THE LOW IS SOMEWHAT UNCERTAIN AT THIS TIME...BUT IT SHOULD TRACK
FAR ENOUGH NORTH TO PROVIDE THE LOCAL AREA WITH A GOOD CHANCE OF
SEEING SIGNIFICANT ACCUMULATIONS. AT THIS POINT...THE POTENTIAL
EXISTS FOR A SIX INCH OR GREATER SNOWFALL IN THE WATCH AREA.

THE LOW PRESSURE CENTER WILL BE A FAIRLY QUICK MOVER...SO MOST IF
NOT ALL OF THE SNOW SHOULD END BY EARLY FRIDAY MORNING.

STAY TUNED TO NOAA WEATHER RADIO AND OTHER LOCAL MEDIA FOR FURTHER
DETAILS OR UPDATES.

A WINTER STORM WATCH IS ISSUED WHEN SEVERE WINTER WEATHER IS
POSSIBLE...BUT NOT IMMINENT. AT THE TIME...THERE IS A POTENTIAL FOR
SIGNIFICANT SNOW AND OR ICE ACCUMULATIONS. FUTURE DRIVING AND WALKING
CONDITIONS MAY BECOME HAZARDOUS...SO IT IS IMPORTANT TO MONITOR THE
LATEST FORECASTS.

[LI Phil]

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
326 PM EST WED FEB 23 2005

VALID 00Z THU FEB 24 2005 - 00Z SUN FEB 27 2005


DAY 1...

MID APPALACHIANS/MID ATLC/WV/PA/NJ/NY...
THE MODELS INDICATE ONE CLOSED 850 MB LOW MOVES TWRDS THE APPALACHIANS AND REFORMS EAST OF THE MOUNTAINS DURING THE AFTERNOON THU...WITH INCREASING LOW LEVEL THETA-E ADVECTION ACRS
WV/VA OVERNIGHT AND MD/PA/NJ THU UNDER AN INTENSIFYING UPPER LEVEL
JET WITH 300 MB WINDS FCST TO INCREASE TO 130 KT BY THE NAM.

MODELS HAVE CONTINUED TREND NORTH OF BOTH THE CYCLONE AND
PRECIPITATION SHIELD...AS PHASING OF NORTHERN/SOUTHERN STREAMS
CONTINUES TO IMPROVE IN MODELS. 12Z NAM TRENDED ABT 100 NM
FURTHER NORTH 06Z-12Z WITH THE 850 MB LOW TRACK AND INCREASED
INTENSITY OF THIS LOW FROM A CLOSED 144 DM 850 MB LOW 00Z FRI TO
141 DM. THE COMPOUNDED TRACK/INTENSITY CHANGE RESULTED IN AN
INCREASE IN QPF AMOUNTS/EXPANSION IN COVERAGE/NORTH SHIFT ACRS
WV/PA/NJ.

THE CANADIAN REGIONAL MODEL/GFS INDICATE THE PRECIP SHIELD IS
FURTHER NORTH THAN PREVIOUS RUNS BUT AMTS NOT AS HIGH AS NAM SINCE THE LOW INTENSITY IS NOT AS GREAT/TRACK IS NOT AS FAR NORTH.
THE UKMET WAS SLOWER IN DEVELOPING A CLOSED 850 MB LOW NEAR THE
MID ATLC COAST NEAR END OF THIS PD...THUS PRODUCES LESS PRECIP.

18Z NAM 24 HR LIQUID EQUIV PRECIP INDICATES MAX AMTS .75 TO .9
INCHES ACRS METRO DC/BALTIMORE...SUPPORTING WIDE SPREAD 6-8 INCHES AND LOCALLY HIGHER TOTALS. A WIDE SWATH OVER HALF INCH EXTENDS ACRS EAST WV AND INTO SOUTHERN PA. THE 12Z GFS INDICATED THE HALF INCH AREA STAYED IN MD...BUT TRENDS WOULD INDICATE A CONTINUED NORTH MOVEMENT OF THIS AREA. A SWATH OF SLEET IS LIKELY ACRS MUCH OF SOUTHWEST AND CENTRAL VA INTO SOUTHERN MD...WITH LIGHT FREEZINGRAIN OVERNIGHT IN THE MOUNTAINS OF WV/SOUTHWEST VA/ADJ NC...BUT DECREASING IN CVG HEADING TWRDS EAST VA AS SOUNDING THERMAL PROFILES BECOME MORE ISOTHERMAL WITH TIME.

DAY 2/3...

LONG ISLAND/SOUTHERN NEW ENGLAND....
ISSUE OF PHASING OF STREAMS AND RESULTANT TRACK/INTENSITY
DIFFERENCES CONTINUES AS 12Z/18Z NAM HAS TRACKED FURTHER NORTH
OVER THE COASTAL WATERS AND THE 18Z NAM INCREASED IN FORWARD
SPEED...NUDGING THE PRECIP/SNOW AREA ABT 40NM EAST FROM THE 12Z
RUN.

THE NAM 850 MB LOW IS FCST TO TRACK FROM THE DELMARVA TO SOUTH OF LONG ISLAND TO NEAR THE 40N 70W BENCHMARK AND BEYOND...AND
INTENSIFYING ALONG THE WAY. THE 12Z ECMWF RUNS ABT A DEGREE SOUTH OF THE NAM...AND THE GFS ANOTHER DEGREE SOUTHEAST OF THE
ECMWF...AND THE UKMET ANOTHER DEGREE SOUTH OF THE GFS.THE 850 MB LOW CENTER IN THE GLOBAL ENSEMBLE MEAN IS ABOUT 90 NM WEST NORTHWEST OF THE GFS OPERATIONAL FCST...SO THE ENSEMBLE MEAN
PRECIP AXIS IS FCST ABOUT 50 NM FURTHER NORTHWEST THAN THE
OPERATIONAL GFS ACRS SOUTHEAST NY/SOUTHERN NEW ENGLAND.

THE CONSENSUS STRONG LEVEL CONVERGENCE AND UPPER DIVERGENCE
SUPPORT AN AREA OF HEAVY SNOW ACRS LONG ISLAND/SOUTHERN NEW
ENGLAND.

THE CANADIAN/UKMET/GFS AREA OF HALF TO ONE INCH LIQUID EQUIV IS
OFF THE COAST VS 12Z/18Z NAM ONSHORE...WITH AN INCH FCST ACRS CAPE COD/ISLANDS.

[Jason234]

The 18Z run's are in...I am very confident on forecasting a plowable amount of snow for this event. All the short-range forecasting models are showing precip. to fall in the form of snow, so p-type is not an issue. The models vary from .25" accum. precip. to about .75-1 inches. The outliers are the GFS and the NAM. The CMC, NOGAPS, are in between for now...but they still show that we receive a plowable amount of snow (greater then 5 inches). The best dynamics for snow will be consequentially over Long Island, with the right rear quad of the jet coming over top. Also the -8 C isotherm at 850mb will be very close to the Island and it will result in ideal snow growth conditions. The thing that stills concerns me is the amount of handoff between the southern and northern branch in terms of moisture but based on what the models are showing it's seems like it will occur. Recent satellite observations indicate a baroclinic leaf is developing and a large area of high to mid level cloud deck is developing. Also to note the cloud deck extends fairly far north and some snow is starting to break out in the frontologentic lifting zone...which wasn't really seen on any model run's. This leads me to believe that a average of 7 inches will fall along the island with the east end receiving the most...so 6-8 inches is my call. Due to the cold nature of the system expect it to be fast and furious, with a prolonged period of snowfall rates above 1 inch per hour. Unlike the last storm that affected the region-ratio's will be higher 12:1. I will eventually update this thread tomorrow when the time comes necessary.

[Jason234]

Expect snow to overun the area by 2:30 P.M...starting out as light and about 1 inch accum. by the nightbreak. After around 6 P.M snow should steadily pick up....and a prolonged period of snow fall rates above an 1 inch per hour is anticipated at the coast and the Island. Plan accordingly.

[LI Phil]

Area Forecast Discussion
National Weather Service Upton Ny
1000 Am Est Thu Feb 24 2005

.short Term (this Afternoon Through Friday)...

Update...no Sig Changes Planned But I/ll Update The Wording For This Afternoon. The Snow Will Gradually Move Into The Local Area This Afternoon. Snow Amounts Look Ok.

Otherwise...lots To Consider Here With Impending Winter Storm. Early Morning Wv Imagery Clearly Shows Strong S/w Digging Through The East Central Plains States. Rex Block Continues To Dominate Over The West Coast. Southern Stream Short Wave Is Helping To Decrease Surface Pressures Over The Sern Us...and Is Aiding In The Maintenance Of Widespread Convection Over Sc As Per Regional Radar Mosaics. The Nam Seems To Have A Decent Handle On This Area Of Heavy Precip...perhaps A Little Better Than The Latest Gfs. Suny Mm5 Ens Members Seem To Have A Decent Handle On This Area Of Convection As Well.

Cirrus Has Already Spread Into Our Area In Advance Of The Upcoming System. Clouds Will Increase Quite Quickly Today As Low Pressure Continues To Develop To Out South. Will Side With The Colder Mav Maxes For Today...given The Thickening Cirrus Shield And Sfc Hi Pretty Much Parked Overhead...allowing For Very Limited Mixing.

To Cut To The Chase...will Generally Side With The Nam On Things
(but Temper Qpf A Little). Mm5 Is Close To Nam...but There Is Considerable Spread Among The Ic Members With Respect To Total Qpf Ending 12z Fri.

I Have To Say This Hasn't Been Very Easy Coming Up With Warning/advisory Areas. Even Though Surrounding Forecast Offices As Well As Hpc Wwe Are In Good Agreement With The Qpf Forecast...the Warning/advisory Criteria Line Basically Bisects My Cwa. This Basically Means That There Is Bust Potential On My Part Either Way I Go With It. That's Just Part Of The Business I Guess.

I Favored The Nam Due To It's Generally Better Handling Of Convection And Mesoscale Processes. Its Further North Low Track May Be A Better Option Considering The Widespread Convection Currently Ongoing Acrs The Carolinas. The Heat Release From This Convection May Very Well Get Carried Northeastward...hence Acting To Raise Heights Further North...which Would Allow For The Sfc Low To Track Further North Than The Gfs...resulting In Heavier Precip Here.

Moderate To Locally Heavy Snow Is Expected Tonight...mainly Along The Coast. The Smaller Grid Spacing Of The Nam Allows For A Better View Of What Mesoscale Processes Might Happen...and I Think This Has An Effect On The Forecasted Qpf. Gfs Grid Spacing Allows For Too Much Smoothing Of Mesoscale Features. Also...nam Experimental Csi Depth Progs Via Hart/fsu Shows Some Instability Will Be Present...combined With Decent Frontogen Overnight Which Supports The Heavy Snow Potential.

With This Said...will Take A Tempered Approach To The Nam Qpf. Cold Temps Should Aid In Around 15:1 Ratios. Expect Snow To Overspread Most Of The Cwa By Mid To Late Afternoon From Sw To Ne As The Precip Chews Through A Substantial Dry Layer.

As Such...will Convert All Winter Storm Watch Areas Over To Winter Storm Warnings At This Time. Will Include Essex And Union In Nj In The Winter Storm Warning. Elsewhere...will Go With Snow Advisories. Winds Will Pick Up Overnight As Temps Drop...allowing For Wind Chill Readings In The Teens And Upper Single Digits. Blowing And Drifting Likely With More Fluffy Nature Of Snow.

As For Amounts...will Go With 5-7 Inches Across Warning
Area...except 6-8 Acrs Suffolk Long Island And Extreme Se Ct. The
Forks Could See Spot 9. Will Generally Go 3 To 6 In The Advisory
Areas. Given Ratios As Well As A Still Uncertain Low Rack...dayshift May Have To Adjust In A Few Areas.

In Any Event...this Will Be A Quick-mover. Snow Should Be Gone By
12z Friday. Hipres At The Sfc Will Build In Friday...but Clouds
Should Linger Due To Approaching S/w From The Lakes.

[Jason234]

The ehco's will be enhacned with the pressure drops (condensation and evaporation) in the mid to upper levels. Models are now more enthusiastic with a lingering area of light snow around long island until about 11 P.M tomorrow morning with a curvature of the trof and isobars...conducive to strong vertical lifting.