Jan 21, 2014: Heavy Snow, Wind, Cold Tonight

Forecast Highlights:

scenarioThe third major snowstorm of this winter is set to affect the area today and tonight as a deepening low pressure tracks northeast parallel to the coast, producing moderate to heavy snow with up to 12 inches expected east and south of NYC along with strong northerly winds and wind chills near -5 to -10 degrees. Cold temperatures will then return for an extended period of time, as high temperatures will mostly remain in the 10s and 20s for the next 7-9 days.


 


<< January 19 | January 20 | January 21 >>

Monday, January 20 Observations:

1.20.14The first arctic cold outbreak since January 7 made its way southward through Canada, with a cold front pushing south through NY state during the day, producing areas of light snow, before reaching the area in the evening with isolated snow showers. With a southwesterly flow initially in place ahead of the front, temperatures returned to above average levels, peaking in the upper 30s inland, low 40s north/west of NYC, and in the mid to upper 40s in NYC and Long Island.

The highest temperature was 48 degrees in JFK airport, and the coolest high temperature was 38 degrees in Andover, NJ.

 


 

Today – Tuesday: Heavy Snow, Wind, Frigid

As yesterday’s morning update noted, there have been few consistent signs for a major storm to affect the region until this point, aside from a few model runs in the 156-180 hour range, which was mostly supported by the ECM which showed a significant system but with a somewhat different setup. The model guidance only fully began to trend towards a major storm early yesterday morning as they continued to slowly correct towards a sharper and stronger shortwave and vort max, which forces a low pressure to develop earlier and closer to the coast with more widespread and heavier precipitation. The trend was not over at that point, however, and the GFS and NAM have continued to trend wetter right through this morning’s 6z runs. While some small scale uncertainty remains, the third major snowstorm of the winter and the first with the heavy snow axis near the NYC area is set to affect the region today and tonight.

 

scenarioImpact Analysis: Since yesterday’s update, when the model guidance was still gradually correcting towards a stronger and further west low pressure, the guidance has generally come close to an agreement regarding the track and impact, with the low pressure tracking near southeast Virginia later today and briefly slows down southeast of New Jersey early tonight as the trough axis gains a negative tilt before quickly deepening and continuing to track northeast towards Atlantic Canada. Considering that the system is mostly northern stream based with little moisture from the Gulf of Mexico involved, as well as the cold air mass present north of the system that will be pulled into the region, precipitation type will be snow for most locations that observe precipitation, including far southern areas in Virginia and eastern North Carolina where some initial mixing with rain is expected. With the deepening of the low pressure and strong mid level lifting, moderate to heavy precipitation is expected to develop near and east of the I-95 corridor, supporting heavy snowfall.

Modeled precipitation amounts generally range from 0.35″ in interior western areas to 0.60″ near NYC and 0.80″ in Long Island/coastal CT. Snow to liquid ratios will be higher than the standard 10:1 ratio, however, with a thick dendritic growth zone (DGZ) with a saturated column up to 600mb, where temperatures of -12C to -18C support the formation of dendrite snow crystals and are favorable for higher ratios, which along with strong lifting within the DGZ but with strong northerly winds at 15-25 mph due to the tightening pressure gradient support ratios of at least 15:1. The strongest mid level lifting and most favorable dynamics are expected to set up between Philadelphia and central NJ and extend into NYC and Long Island, which is roughly where the heavy snow bands are expected to develop between 4-9pm, and the possibility of thundersnow cannot be ruled out under some of these bands. Later into the evening and night hours, the heavy snow bands will weaken as they shift east into Long Island and CT. Northwest of these bands into NW NJ and SE NY, steady moderate snow is expected throughout the duration of the storm. With the above factors noted, snow totals of 3-6″ are expected in NW NJ and SE NY, 7-11″ over the immediate NYC area, and 8-12″ over southern NYC into Long Island and coastal CT. There remains some uncertainty depending on the exact banding and ratios, however, with higher ratios and locations under the aforementioned banding axis capable of surpassing 12″ of snow, while locations northwest of the bands potentially seeing slightly less snow than forecast.

 

snowmap2Forecast for NYC Area: Snow showers have already developed across northern NJ and NYC over the last 1-2 hours, and are expected to continue to steadily spread across the rest of the area by the early afternoon. Temperatures will continue to steadily fall before stalling in the low to mid 10s north and west of NYC and mid to upper 10s near and south/east of NYC for the mid to late afternoon hours. Heavy snow bands will develop near Philadelphia and central NJ early this afternoon, likely spreading into the area by 3-4pm with heavy snow focusing near NYC and Long Island/coastal CT while moderate snow falls elsewhere. Thundersnow cannot be ruled out under the heavier snow bands. By the evening and early overnight hours, a strengthening northerly wind up to 15-25 mph is expected, which along with heavy snow is expected to lead to near blizzard conditions in Long Island, although official blizzard criteria is not expected to be reached, while wind chill values fall into the 0 to -10 degree range. The snow bands will gradually shift east into the rest of Long Island and CT while weakening after 9-11pm, with snow steadily tapering off from west to east from 12am-2am west of NYC and 3-5am east of NYC.

Snow accumulations of at least 3-6″ are expected in NW NJ and SE NY, 7-11″ over the immediate NYC area, and 8-12″ over southern NYC into Long Island and coastal CT. While the model guidance has come into better agreement since yesterday’s update, despite the fact that it has taken until the night before the storm to actually reach a consensus, there remain some minor uncertainties regarding the snow totals and the ratios, with higher ratios than currently forecast leading to an increased likelihood of totals near/locally over 12 inches. The setup of the heavy snow bands will also continue to be monitored, which is currently forecast to end up from central NJ into NYC and west-central Long Island; this axis has the potential to see more snow than currently forecast, while NW NJ and SE NY may see slightly less snow than currently forecast. Live storm updates will be posted starting around 1pm and continuing through the early overnight hours.

 

Wednesday – Beyond: Cold Persists, Brief Break on Saturday

This storm will mark a return to sustained cold temperatures following the recent pattern moderation, as strong northerly winds will allow for cold surface temperatures to advect into the area tonight into Wednesday. Low temperatures tonight are expected to fall into the mid-upper 0s for most, with the immediate coast likely in the low 0s and interior NW NJ/SE NY slightly below zero. Along with strong north winds, wind chill values of -5 to -15 degrees are expected for Wednesday morning. High temperatures are only expected to reach the mid to upper 10s for most locations, marking the 3rd such day this year that temperatures have stayed below 20 degrees, an occurrence that in recent years has not happened much more than once each winter, if at all. Temperatures will slightly warm on Thursday as a weakening frontal boundary moves through, possibly producing isolated snow showers, with highs in the low-mid 20s expected. The remaining cold air mass behind the frontal boundary will then move through overnight into Friday with some moderation, as lows again fall into the mid 0s-low 10s for most locations and near zero inland, with highs slightly cooler than those of Thursday, peaking in the upper 10s to low 20s.

A brief moderation in temperatures will occur on Saturday as a strong low pressure develops near southern Canada with a strong southwesterly flow over the region removing most of the cold air, but with enough left for temperatures to peak in the upper 20s-low 30s for most locations; with enough cold and moisture in place, scattered snow showers are possible on Saturday and Saturday night. A strong piece of the polar vortex will then shift into southern Canada with the aid of strong ridging building into the northeast Pacific and extending north of Canada, dragging a frigid air mass to settle just north of the US/Canada border; unlike early January, however, the core of the cold is not expected to spill into the US, also considering a lack of blocking over Canada that was present in early January, although temperatures are nonetheless expected to remain cold, with highs generally in the 10s and 20s and lows in the single digits and 10s, with the next snow potential likely towards the middle of next week.

One thought on “Jan 21, 2014: Heavy Snow, Wind, Cold Tonight

  1. CHRISTAIN Reply

    it is cold as I do not know what. something is wrong with this weather this weather needs to change quickly its cold outside kids getting sick I just cant believe it its crazy

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