Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 8:29 PM GMT on January 09, 2011
Thoughts on January 11-12 Snowstorm...
A 1008mb low pressure is developing off the coast of Texas spreading of plethora of moisture northward along the Gulf Coast states. The low is courtesy of a deep trough sinking south towards the middle of the nation with an accompained strong 500mb low. With the trough axis being situated relatively far west, a low pressure will develop along a weak jet streak towards Missouri and slowly move northward. This low pressure will weaken and shear apart the Gulf of Mexico low pressure. Both lows will begin to lift northeastward with moisturing favoring the primary low and coastal low near Georgia. In between a dry slot will affect parts of the central Appalachians with moisture less than .15in. As the double barrel low complex continues to progress, the primary low over the Ohio valley will begin to weak and shear apart courtesy of significant blocking across northern Canada with a near record low Arctic Oscillation and negative NAO. This will begin an energy transfer restrengthening the coastal low. The timing of this transfer of energy remains highly uncertain at this point and will be very important to the evolution of this system as it traverses up the coastline with a heavy snowstorm across New England.
By Tuesday morning widespread light snow will begin across the Middle Atlantic reaching the Mason-Dixon line. Snow will be relatively light with rates only about .25in per hour as model QPF suggests less than .25in south of the Mason-Dixon line as this region will essentially be in a dry slot. As the coastal low continues to develop, the precipitation shield will begin to intensify from the Mason-Dixon line on northward with moderate snow by early afternoon as far north as the Mason-Dixon line in a widespread manner with rates around .5in per hour. Given the retreating high over Canada, the system will be a relatively quick mover. Current high resolution model guidance shows excellent dendritic growth over much of Pennsylvania west the New Jersey/Pennsylvania border coinciding with H85 thermals below -6C. This will allow favorable snow ratios of 15:1 or slightly higher over central and western Pennsylvania. Current QPF for the state of Pennsylvania through Tuesday night will be around .25-.4in from the overrunning, warm air advection precipitation.
By Tuesday night the low will begin to rapidly intensify off the coast throw a strong CCB across parts of eastern Pennsylvania, New Jersey, and southern New York. Favorable dendritic growth accompanied by enhanced frontogenesis will allow snow rates to increase to 1in/hr especially northeast of Trenton, New Jersey. The low will rapidly intensify to +-992mb by Wednesday morning with heavy snow across much of New England with several enhanced mesoscale bands. A tight pressure gradient will also allow surface winds to increase to 35mph+ gusts along the coast courtesy of a 50knot+ low level jet mixing occasionally down to the surface in heavy precipitation. The low will continue to move northeast with storm total QPF in excess of 1in from just northeast of New York City up through much of New England. Orographic lift across the Berkshires up through the Presidentials will enhance snowfall with storm totals upwards of 14in across the favored upslope regions. Given the relatively fast movement of the storm, snow totals should remain below 18in for all areas.
Many questions remain on the exact track and intensity of the low along with the question of timing on the transfer of energy. But the above summary gives a general basis to the evolution of the storm system. Expect more updates coming tomorrow.
This is my current rain/snow line...
Salisbury, Maryland - Georgetown, Delaware - Atlantic City, New Jersey - Islip, Long Island - Nantucket, Massachusetts
*Note west of this line will stay all snow for the entire duration of the storm. Along the line the snow will vary to sleet and perhaps rain for a point. But given the rapid cyclogensis the coastal low will undergo, most all areas even along the rainn/snow line will receive large snowfall accumulations especially as one moves north of Atlantic City.
1. Widespread snow accumulations in excess of 1in from Georgia to Maine.
2. Gusty winds as low pressure bombs out off of Long Island with gusts exceeding 35mph within 50mi of the Atlantic coast.
3. Heavy snow accumulations of 12in+ in parts of New England.
4. Embedded snow bands from New York City on northeastward with 2-3in/hr rates.
5. Very cold temperatures west of I-95 barely rising out of the low to mid 20s during the bulk of the snow accumulation.
The more difficult locations for the forecast include central Pennsylvania and northern parts of New England across northern Vermont, New Hampshire, and Maine. These areas have the highest bust potential in this storm.
Selected City Snowfall Accumulations for the Northeast...
Hagerstown, MD- Light to moderate snow; 1-3in
Baltimore, MD- Moderate snow at times; 2-5in
Salisbury, MD- Wet snow and sleet mix; 1-4in
Washington, DC- Light to moderate snow; 1-4in
Wilmington, DE- Moderate snow, heavy at times; 4-8in
Dover, DE- Moderate snow; 3-7in
Trenton, NJ- Moderate to heavy snow; 5-10in
Pittsburgh, PA- Moderate snow; 2-5in
State College, PA- Light to moderate snow; 1-4in
Harrisburg, PA- Moderate snow; 2-6in
Philadelphia, PA- Moderate to heavy snow; 5-9in
Scranton, PA- Moderate snow; 3-6in
New York City, NY- Heavy snow; 6-12in, locally more
Poughkeepsie, NY- Moderate to heavy snow; 4-8in
Binghamton, NY- Moderate snow; 3-6in
Albany, NY- Moderate to heavy snow at times; 3-7in
Hartford, CT- Heavy snow; 10-15in
New London, CT- Heavy snow; 10-15in
Concord, NH- Moderate to heavy snow; 6-12in
Providence, RI- Heavy blowing snow; 10-16in
Worcester, MA- Heavy snow; 12-16in
Boston, MA- Heavy snow, windy at times; 8-14in
Nantucket, MA- Heavy snow mixing with sleet at times, windy; 4-9in
Hyannis, MA- Heavy snow, windy with drifting snow; 7-13in
Portland, ME- Heavy snow; 6-12in
Bangor, ME- Moderate to heavy snow; 4-9in
"Final Forecast Above"
A very dynamic storm setup is creating model chaos with polarizing views dependent on the models. The high resolution models including the NAM, NMM, and ARW are indicating this storm becoming a bit more amplified allowing for a further west track. This allows the low to intensify quicker with heavier precipitation. Several mesoscale boundaries are being indicated especially towards southern New England particularily just northwest of New York City with an increased area of upward vertical velocities are present based on the NAM 700mb. The mesoscale boundaries will feature the heaviest snow rates accompanied by the best dendritic growth with hourly rates up to 2in per hour. Current GFS/NAM combination indicates a deep area of frontogenic forcing with an embedded CCB band across central Connecticut and central Massachusetts. Further south, the less dynamics will be available especially south of New York City with a weaker portion of the deformation band. The overrunning precipitation associated with the primary low over Ohio will spread light to moderate snows developing from Washington DC northward stretching from Columbus, OH to Reading, PA. Shortly, HIRES NMM simulated radar indicates a collapsing precipitation shield as energy is transferred off the coast. The simulated radar shows a large strengthening deformation band from about Harrisburg on eastward quickly moving north and east. The GFS and NAM differ on the strength of this axis as for QPF placement. Again the mesoscale, high resolution models show significantly more precipitation than the operational models of the GFS, ECMWF, and GGEM. Now the mesoscale models have a precipitation wet bias, but still the differences are quite significant in QPF in when taking in account the wet bias. The H5 charts are quite similar on all the guidance, but the surface plots differ. Given the general theme of declining QPF in antecedent runs leading up to the event, I am actually using GFS/ECMWF QPF has my primary blend. While yes the mesoscale models are quite wetter along with the SREF blend, the recent poor model QPF performance leads me to blend a bit conservative at this point. Considerable questions remain to where the dry slot occurs in Pennsylvania and how far north the heavy precipitation gets across northern New England. These nuisances will likely only be discovered upon actual evaluation of the radar. For further reference, after tracking the RUC QPF during the December 26 storm, I found it to be highly inaccurate. Overall QPF performance has been very poor recently, so I am sticking with the low QPF blend.
After the storm...
As the low pressure zips northeast out of the region, an anticyclonic flow will resume with a bit of lake effect snow. The air mass left in its wake will be very dry likely preventing a widespread lake effect snow outbreak. The flow also favors a northerly trajectory, keeping a hold on the lake effect machine. A few areas downwind of the lakes in the Syracuse-Finger Lake belt may receive a quick 3-6in in the Wednesday to Thursday time frame. Further south across Maryland and Pennsylvania the snow belts will likely get a minimal 1-5in including the Laurel Highlands. A weak disturbance will move across the area Friday with some light snow showers and flurries across the Northeast especially towards New York state. Little to no snow accumulation is likely. A very strong high pressure, 1038mb, will slowly move east out of the middle of the nation bringing clearing skies across the entire region towards Saturday. This high pressure will center itself across the Middle Atlantic likely bringing some radiational cooling Saturday night for one of the coldest nights of the winter. With a widespread snow cover over the entire east coast coupled with a below normal trough and low dewpoints, lows below zero are likely in the colder spots near Bradford, Pennsylvania and up across northern New York state along with parts of Maine. High temperatures much of the week will be around (-3)-(-7)F below normal for the entire Northeast, but especially for those with a solid snow pack. By Sunday, things begin to get interesting as a -3SD trough moves south over the Northern Plains with H85 thermals near -25C accompanied by a 1038mb high pressure. Lows over the Midwest may drop to near -20F or so in some areas across the north country. This arctic front will center itself across the Mississippi Valley along the steep temperature contrast. A low pressure will develop along the front, but it remains uncertain with regards to the track. In any case it is likely some light snow will exist along the arctic front as it cross through the Northeast with several heavy squalls given what appears a decent WINDEX event. The low pressure over the mouth of the Mississippi will just play another role. The ECMWF delays this arctic air mass a bit later in the week, so the long range definitely remains uncertain post Saturday, January 15. Following that I am expecting a slight rebound in temperatures to close the month of January with slightly above normal temperatures as the pattern reloads. The key word there is reloads. Current wavelengths support another wintry blast for an above normal snowfall February. At this point if this forecast holds, most all winter predictions will completely bust. As we say last year, an anomalous -AO will dominate despite whatever the ENSO conditions.
Please post storm reports in this blog from across the Northeast during the winter storm and please post location of observation in each report...
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"Here northeast of Harrisburg 2010-2011 winter statistics"
Current Snow Cover- 6in
Monthly Total (November)- Trace
Monthly Total (December)- 0.6in
Monthly Total (January)- 7.75
Seasonal Total- 8.35in
Winter Weather Advisories- 2
Winter Storm Warnings- 0
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 1
Winter Storm Watches- 1
Lowest High Temperature- 24.1F
Lowest Low Temperature- 12.8F
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First accumulating snow - December 10 - 0.50in
Clipper light snow - January 7-8 - 2.25in then another 1in
Double Barrel Low - January 11 - 4.5in of snow
Lower Susquehanna Valley Doppler...
(Courtesy of WGAL)
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