snowfall totals

New Snowfall Map for 3/02-3/03

Miguel Pierre Forecasts, Winter Wx , ,

FinalSnwofallmap0303

This morning’s 6z and 12z NAM, RGEM, GFS guidance today has trended further south this storm. The latest HRRR runs also supports this trend. Total qpf totals for Northern NYC are now in .10″ -. 25″ range. With less north and more south. Current radar, water vapor imagery, and observations, don’t give me much reason doubt these solutions. Also some warmer temperatures, may support more wet snow,sleet, rain at onset. Especially over Southern New Jersey. The cause for the continue trend further south, is the lobe of the PV, dropping down faster into Great Lakes and Northeast regions and suppressing this
southern stream wave.

Along with the south trend, is also a trend to end the storm faster everyone. For NNJ,NYC, LI snow may tapering off to flurries by sunrise tomorrow morning. While steadier snow continues further south into late morning or early afternoon hours tomorrow.

So for all those reasons, snowfall totals have been adjusted downward everywhere. And it’s possible this is still too high for some areas. Just to note, the ranges in general, are from lowest to highest; from north to south. For example: Staten Island, is more likely to see 3″ or 4″ than 5″ or 6″. While Philadelphia is likely to see at or either side close to 6″.

Snowfall Map and Discussion for 2/18/14 Winter Storm

Miguel Pierre Forecasts ,

 

130am Snowfall map***Updated snowfall map, based latest guidance and observation and radar trends. It appears this system moving faster, and less snowfall will fall for areas NW of NYC. Still anyone visibilities may reduced to 1/4 mile for a couple hours, in heavy bands of snow.***

Cold high pressure will slide to the east tonight. Winds will turn more southeasterly. Temps will probably not drop much this evening and the may rise after midnight, near the coast. A 500mb shortwave will phases into closed low over Great Lakes region than open up as it heads east. At the surface, a small but robust area of low pressure will into Ontario and weaken. A secondary low will form near NJ/DE coasts and track into New England. This will set the area up for another moderate winter storm.

Precipitation with this system should arrive late tonight. There will be enough cold air in place, for everyone to start as accumulating snow. However, a  low-level southeast flow increases, enough warm air arrive to change coastal sections to rain or drizzle before ending tomorrow afternoon. Exactly when this happens and how snow fall before it, is problematic as mesocale models such as the NAM and RGEM are showing more liquid amounts than the global models. As they develop secondary low faster. Dynamics may also come into playing in keep boundary level temps cooler. The NAM model shows strong upward vertical velocities and mid-level instability (H5-7 lapse rates 7.1 C/km and total totals in upper 40s) that would result in band producing 2-3″ per  snowfall rates tomorrow morning with perhaps some thunder, before any changeover. The shortwave energy with system is also very potent. At this time, I will stay under the NAM’s totals. But if the NAM is correct, or the changeover is delayed, snowfall totals could be a few inches higher than on snowfall map.

namNE_500_avort_021Areas that see the least snowfall on the map, are south and east face shores that will most influenced by 15-30kt SE winds off the ocean and changeover to rain quickly. Just little farther inland over north side of NYC and north shore of LI snow will last longer, and come down moderate to heavy at times. Before changeover to rain and ending after 1-3 hours. Further NW in NNJ and theLower Hudson Valley, should remain mostly snow (perhaps ending as light rain and drizzle).

I might update this forecast map this evening or tonight, if more guidance comes in supporting a bigger/smaller snowfall. Tomorrow morning, I will be nowcasting here.