6-7 March 2011 – Significant multi-hazard winter storm
A cold front moved gradually southeastward across the
region during the day on Sunday, March 6th, as a wave of low pressure moved
northeastward along the boundary Sunday night into Monday, March 7th. To the
south of the boundary, it was mild as the area was in the warm sector of the
low pressure system. The storm tapped into both
Colder air was drawn into the area in the wake of the boundary, changing the ongoing rain to mixed precipitation, freezing rain and sleet, then to snow. The period of mixed precipitation only lasted a couple hours, except for across a portion of the Capital District where a prolonged period of mostly sleet occurred and across a portion of the Taconic where a prolonged period of freezing rain occurred. Once again, similar to the 25 February storm, it was a big forecast challenge determining where the mixed precipitation within the precipitation transition zone was going to be. There were conflicting model/ensemble data, with the GEFS showing run-to-run consistency, and the SREF shifting the precipitation transitions zone a little east within 12 hours of the precipitation onset, making for another exceptionally challenging forecast, similar to the 25 February storm.
Heavy snow accumulated across the western
The snow came down heavy at times, with snowfall rates of 1 to 2 inches per hour. In addition, brisk northerly winds resulted in blowing and drifting of the snow during the morning hours. This combination of heavy snow, along with blowing and drifting of the snow made it difficult for snow plows to clear the roads. The heavy snow and sleet resulted in widespread power outages, school closures, traffic accidents and even a few roof collapses.
925 hPa and 850 hPa temperature forecasts.
Note the tight temperature gradients through central and eastern NY and
central and northern
Above: GEFS 850 hPa winds (top row) and 925 hPa winds (bottom row). Note the separate wind maxima over the Carolinas in the right panels (initialized 12Z 06 March) represented by the 3-4 SD above normal contour, suggesting a second southern stream upper impulse approaching the northeastern U.S. that was not captured in earlier guidance.
Above: GEFS probability for 1.00 inches liquid equivalent precipitation in 24 hours. Note the more widespread and higher probabilities indicated in the near term guidance in the right panel (initialized 00Z 6 March). In fact the probabilities expanded inland.
Above: GEFS precipitation type forecasts, showing the west and northwest shift of the precipitation transitions zone and mixed precipitation in the nearer term guidance in the right panel (initialized 12Z 6 March).
Above: GFS 850
hPa temperatures and heights (top row) and 925 hPa temperatures and heights
(bottom row). There was very little
change in the position of the tight thermal gradient, but the heights were
forecasted to be lower in the near term guidance (initialized 12Z 6 March)
implying a stronger system tracking toward the northeastern
850 hPa temperatures (left) and winds (center and right). Note the tight thermal gradient is a little
west of where the gradient is in the GEFS.
Also note that the SREF is showing the developing system in the
Above: SREF probability for 1.00 inch liquid equivalent precipitation in 24 hours. Note the westward expansion of the high probabilities, similar to the GEFS.
Above: SREF precipitation type. Note the probabilities for various precipitation types shifted a little eastward in the near term guidance (initialized 09Z 6 March).
(top row) and SREF (bottom row) plume diagrams for
Above: Loop of surface maps showing the movement of the frontal systems and high and low pressure centers.
Pictures of ice accumulation in the mid
Pictures of ice accumulation from
Pictures of flooding in the mid
Flooding at Wappingers Creek near
Above: Ice jam
forming near the Stockade in