Significant Nor'easter to impact Northeast...
Posted: 6 February 2013
A northern stream influence will phase with another disturbance out of the southern stream and subsequent cyclogenesis along the New England coast is anticipated during the February 8-9 time period. Significant storm impacts will occur from western New York east to Cape Cod. Given the late redevelopment and associated Miller B-type storm formation, many areas south of the 40N will see little impact from this event. Slow movement and impressive mesoscale banding will result in snow accumulations in excess of two feet for some areas just west of Boston. While too early to declare this a KU event, the entire situation is definitely worth monitoring over the next few days with potential NESIS ratings likely on the order of 2-3.
Current Surface Plot...
(Courtesy of HPC)
February 8-9 Nor'easter
A quick hello after a short hiatus from blogging over the past few weeks; I know many of you are still waiting to hear my thoughts on the American Meteorological Society conference. Eventually I will get around to writing up a quick summary for those interested. Nevertheless, it was a necessary to provide an immediate full update on what will be a very significant nor'easter to impact the Northeast. Blizzard conditions will likely occur across much of the densely populated portions of eastern Massachusetts including the Boston metropolitan region.
The complex and impressively large storm system will build itself in a series of critical puzzle pieces that will fit together to east coast cyclogenesis. A northern stream wave, which is already evident on radar across the northern and eastern Midwest will continue tracking south and east. This weak surface low (not even evident on some surface maps) will track across southern Ohio. A weak H85 low will be associated with this wave and will move into Pennsylvania and extreme southern New York. Therefore WAA at the surface will likely occur under southwest winds despite a strong banana high pressure system to the north. As the northern stream begins to interact with the moisture-filled subtropical jet, another low pressure will begin to take shape off the North Carolina coastline. This is a very typical Miller B type storm evolution.
The low pressure will begin to rapidly deepen and expend its precipitation shield inland. Isentropic lift and weak frontogenic forcing ahead of the S/W in Ohio will spread light snows across western and the southern tier counties of New York State by Thursday night. This precipitation will be primarily driven from the northern stream system. Guidance is suggesting a small window of bombogenesis with pressure falls ~3mb/hr as surface pressures drop to 988mb south of Long Island, NY. A track just inside the 40/70 benchmark is then expected.
Precipitation will be falling in two distinctive shields. One across New York State and the other expanding in the Delmarva with the coastal low. Eventually as the phasing occurs (timing remains uncertain), the radar will take on a different graphic with a strong dominant deformation axis from central New York that will slowly move east spreading heavy snow in its path. There will likely be a large dry slot that will form to the south and east of the deformation axis. It is likely this will impact most of the state of Pennsylvania. As will be noted below, there are a few signs on the latest guidance that this dry slot could impact areas as far east and north as New York City and the Connecticut river valley.
The low pressure will continue trekking northeast and develop several impressive mesoscale bands associated with the CCB axis from New York City northeast to Boston. Guidance suggests high Omega values and near-ideal snow growth with a low, moist dendritic layer. H85s will primary focus around -10C providing an additional support for excellent snow rates during the height of this storm especially for areas just inland towards Worcester, Massachusetts. QPF will likely exceed .5" in a small three window for some areas of central and eastern Massachusetts with therefore associated snow rates exceeding 2"/hr. Elevated instability will be possible along the highest frontogensis and PWATs axis again focused in central areas; therefore thunder snows cannot be ruled out. This signal though may grow as we get closer to the event and 4km HIRES models have a better look at the banding impacts of the storm.
A few current models indicate that as the low becomes vertically stacked, that it may stall for a period of time. It is likely this is an over-amplification error. Therefore the QPF amounts >3" are likely irrelevant to this event. In general the jet flow is still relatively progressive and inhibits these classic KU characteristics.
A widespread and uniform moderate snowfall will occur from western New York east and north to the northern Maine with 4-10" of snow. The best forcing will be south and east along with the best snow growth. Closer to the tightly wrapped east coast low will be an axis of very high snow amounts that may approach two feet in some areas. The highest QPF and snow will likely fall near the Worcester region.
A few concerns of mine still exist for this event. Given the progressive flow if the phase capture occurs a bit later, the secondary low will form farther northeast. Therefore the dry slow will approach the tristate region into portions of even eastern Connecticut. This would also limit the higher snowfall amounts across the southern tier of New York allowing for more WAA as 2m temperatures warm into the mid 30s. Also the exact location of the rain/snow primary lines, especially towards New York City, will be highly dependent on the strength of the deformation axis/CCB. Therefore a high bust potential exists in this region. A few days remain before the event, but by Thursday evening WAA snows will already be moving into western New York. Stay tuned!
(Courtesy of Intellicast)
(Courtesy of NOAA)
This is my current rain/snow line...
Pittsburgh, PA - State College, PA - Wilkes-Barre, PA - Mt. Pocono, PA - New York City, NY - New London, CT - Hyannis, MA
***For this event there will not be one defined snow line. Also little to no mixed precipitation is expected given the setup therefore limiting precipitation types to either rain or snow. I chose my line based on a 75/25 split with >75% being snow as the majority precipitation for areas along and north of the line. Therefore while areas will mix with rain to the south, some snow accumulation cannot be ruled out especially for areas in the deformation axis as the system begins to pull northeast into the Gulf of Maine.
1. Widespread snow accumulations possible in excess of 10" from Buffalo, NY east to Boston, MA.
2. High, damaging winds anticipated along the immediate coast with gale force gusts in excess of 55mph particularly along Cape Cod.
3. Rain/snow mix can be expected in a narrow corridor along the southern periphery of the deformation axis. This may impact the NYC metro area.
4. High snow rates can be expected with model output suggesting up >6"/hr totals for a 3 hour period in New England during the height of the event.
5. Major impacts along I-95 corridor north of 40N where few winter storms have occurred this year to prepare people for winter driving conditions.
***Snow map posted 3pm 2/6/2013. This snow map is preliminary due to its early posting, but should give a general idea for most locations where the heavier snow will occur. My favored axis for two feet potential is just west of Boston towards the Worcester corridor where high snow rates and excellent snow growth will occur in correspondence to the impressive CCB band. A more difficult forecast for New York City is likely where they will be very close to a dry slot and warmer temperatures. In the end my forecast does abide by a colder approach give the dense air mass over the region and a bit of snow cover. Therefore I am extending some light snow accumulation as far south as Philadelphia where they may see the tail end of the deformation axis. The dry slot will significantly inhibit snowfall over the Middle Atlantic including Maryland, Washington DC, and central Pennsylvania. Warmer temperatures at the surface will also prevail in this region. Nevertheless it is possible for light snow accumulations as far south as the Mason-Dixon line.
Current Great Lakes Water Temperatures...
(Courtesy of NOAA)
Selected City Accumulations for the Northeast...
Hagerstown, MD- Light to moderate rain
Baltimore, MD- Scattered rain showers
Salisbury, MD- A few rain showers
Pittsburgh, PA- Rain/snow showers. Snow accumulations up to 2-3"
State College PA- Rain/snow showers. Snow accumulations 1-3"
Williamsport, PA- Periods of snow mixing with a little rain. Snow accumulations 2-4"
Altoona, PA- Rain/snow showers. Snow accumulations 1-2"
Harrisburg, PA- Rain/snow showers. Snow accumulations T-2"
Lancaster, PA- Rain/snow showers. Snow accumulations T-2"
Philadelphia, PA- Periods of rain mixed with occasional heavy snow. Snow accumulations 2-4"
Allentown, PA- Periods of heavy rain/snow. Snow accumulations 3-6"
Scranton, PA- Periods of heavy rain/snow. Snow accumulation 3-7"
Washington, DC- A few rain showers
Wilmington, DE- Occasional rain/snow showers. Snow accumulations 1-4"
Dover, DE- Occasional rain showers
Trenton, NJ- Periods of heavy rain/snow. Snow accumulations 2-5"
New York City, NY- Heavy snow occasionally mixed with rain. Snow accumulations 3-7"
Poughkeepsie, NY- Periods of heavy snow. Snow accumulations 4-8"
Binghamton, NY- Periods of heavy snow. Snow accumulations 5-10"
Ithaca, NY- Periods of heavy snow. Snow accumulations 5-10"
Albany, NY- Heavy snow and gusty winds. Snow accumulations 10-14"
Hartford, CT- Heavy snow and strong winds. Snow accumulations 10-15"
Concord, NH- Heavy snow and strong winds. Snow accumulations 14-18"
Providence, RI- Heavy snow occasionally mixed with periods of rain. Snow accumulations 10-14"
Worcester, MA- Blizzard conditions expected. Snow accumulations 15-20" with localized higher amounts
Boston, MA- Blizzard conditions expected. Snow accumulations 12-15" with localized higher amounts
Nantucket, MA- Periods of rain mixed with heavy snow. Snow accumulations 3-7"
Hyannis, MA- Periods of heavy rain/snow. Snow accumulations 4-8"
Burlington, VT- Heavy snow expected. Snow accumulations 8-12"
Portland, ME- Blizzard conditions expected. Snow accumulations 14-18" with localized higher amounts
Bangor, ME- Periods of heavy snow. Snow accumulations 8-12"
"Subject to Change"
Current Northeast Snow Depth and Northeast Wind chills...
(Courtesy of Wunderground)
A few computer model differences still exist especially in regards to the evolution of the phasing of the northern and southern streams. The extent and timing of this is critical for forecasts. Currently the NAM is the flattest piece of guidance despite the overly excessive QPF progged once the storm moves east of Cape Cod. 3-4" storm totals will not be occurring anywhere for this event; I do not buy into the storm stalling and being captured theory. I also believe the ECMWF is having a few QPF issues in the extent of the western periphery of the 1" range in New York state. Also it is currently running as the coldest model with 2m temps <0C as far south as the Mason-Dixon line during the start of the event. It is likely there will be enough WAA to allow temperatures to rise into the mid 30s as far north as Williamsport for a short period.
Globals will struggle with the exact positioning and cut-off of the dry slot. I would expect this region to be larger than anticipated on guidance and pose a significantly wrench in forecasting efforts for portions of the Middle Atlantic. In general not many other model contrasts exist at this point as it is a bit too early for HIRES 4km runs.
After the Storm
Quieter weather and little in the way of lake effect snow is likely for the period after this event. We will begin to see the ridge axis slide east across the central United States allowing for milder air to slide in across the east coast. Nevertheless, the air mass only remains marginally above normal so a torch period is not expected. A low pressure will track up through the Great Lakes for the beginning of next week. Some cold air immediately at the surface will allow any rain to fall as freezing rain especially for areas along and north of I-80. Eventually the precipitation will change to all rain north to the Canadian border. QPF amounts will generally be light and less than 0.5" for all areas. The next storm system of interest impacts the region on Valentine's Day. This event poses a bit more of a threat for wintry precipitation. Current wavelengths suggest though that precipitation type will be a problem for some areas at the minimum. At this point a significant east coast snow storm is not likely, but some areas of moderate to heavy snow accumulations are possible. February continues to look farely active with a top heavy northern stream. In response periods of dry, cold air such as that which occurred in January will not affect the Northeast this month. Snowfall accumulations may average near normal for many areas along and north of 40N this month. Again the general circulation is fairly similar to an -ENSO despite the conflicting teleconnections. I will post a new blog as soon as I can towards this coming weekend.
Please post storm reports in this blog from across the Northeast during the winter storm and please post location of observation in each report...
This blog is in progress. Check back soon...
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Lower Susquehanna Valley Doppler...
(Courtesy of WGAL)
"10mi northeast of Harrisburg 2012-2013 Winter Statistics"
Monthly Total (October)- 0.0"
Monthly Total (November)- 0.8"
Monthly Total (December)- 9.5"
Monthly Total (January)- 5.8"
Monthly Total (February)- 1.8"
Seasonal Total- 18.1"
Winter Weather Advisories- 6
Winter Storm Warnings- 0
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 1
Winter Storm Watches- 0
Lowest High Temperature- 32.1F
Lowest Low Temperature- 18.2F
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
First Trace of Snow - November 24 - Lake Effect Snow Showers
First Measurable Snow - November 27 - 0.8" - Overrunning event
Enhanced Clipper - December 24 - 2.1" - Christmas Eve Snow!
Miller B - December 26 - 3.3" - 0.15" of freezing rain also
Miller B - December 29 - 4.1" - Moderate all snow event
SWFE - January 15-16 - 1.0" - Snow/sleet/freezing rain/rain
Arctic Cold Front - January 21 - 0.5" - fluffy snow
Weak southern disturbance - January 25 - 3.3" - snow ratios above 20:1
Great Lakes Cutter - January 28 - 1.0" - snow/sleet/freezing rain/rain
Alberta Clipper - February 2 - 1.0" - very light snow