Month: February 2014

More Cold and Snow for Next Week into March

Miguel Pierre Uncategorized

This is an update to the previous post on the cold & storm pattern in late February and early March

First, the model guidance now the Polar vortex drop further south in SE Canada. This is due the 500mb heights increasing around North Pole. This is similar pattern evolution we saw in the last two weeks of January  So there is now more potential for more extreme cold for late February and early March. You may have to wear you big coats again. The GEFS shows this potential for very anomalous negative 500mb height and surface temparture departures, near end of the next week.

12zGEFSf168

12zGEFSD8Another minor stratospheric warm event is occurring. The EP vectors are forecast shift more to right (poleward) by ECMWF. This would means that warm would be downwell in higher latitudes. Possibly resulting more west-based blocking over Greenland/Davis Strait.

70mb9065

ECfluxesThe MJO still forecast by GFS and ECMWF ensembles to head in through phases 7 and 8. These forecasts are a little less than reliable. But they have been fairly consistent this week. There is more support for progression by westerly vector wind anomalies being shown at 200mb and 850mb, over the Central Pacific.

220MJOforecastsMore later…

Rain Today, Strong Thunderstorms Possible Friday

Miguel Pierre Severe Wx, Winter Wx

A frontal system and strong shortwave trough will give the region a period of rain from later this morning into this afternoon.  The rain can be seen on radar over PA. Temperatures aloft are enough for the area to only see rainfall from this event. However, surface temperatures may be slow to rise above freezing, due to the snowpack. Which could cause rain to freeze on surfaces. Especially north and west of NYC. Therefore, the National Weather Service has issued a Freezing Rain Advisory for NW NJ and Orange and Rockland Counties in NY. Rainfall totals are likely between .25″ – .50″ across the area. So no significant flooding is expected. However snow melt today may cause some ponding on the roadways. So wear waterproof boots. Rain should ending this evening.

Radar2A cold front will move through on Friday, with some showers and possibly some thunderstorms. SPC has places southern parts of the tri-state area in a 5% or 15% risk for thunderstorms with damaging wind gusts. Models don’t show any surface-based instability. So severe weather is not likely. But with a strong 500mb jet streak and some elevated instability there is potential for a forced low-topped squall line that produce wind gusts of at least 40mph. Temperatures will also likely rise into 50s ahead of this front.

day3prob_0830
gfsNE_500_spd_060These weekend will feature mostly dry weather, with a gradual step down with temperatures. Next week still looks much colder with a threat of more snow.

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.