Jan 27, 2014: Cold Ends By Friday

Forecast Highlights:

temp39After a prolonged spell of cold temperatures, a more sustained warm up is in sight, but not before a final surge of arctic cold for a while affects the region on Tuesday and Wednesday, with highs back into the 10s to low 20s as a snowstorm remains south of the area, affecting locations unusually far south. A gradual warming trend will then begin, with highs back into the 30s by Friday along with multiple rain and/or snow chances both for the weekend and the middle of next week (Image credit: PSU e-Wall, modeled highs for Tues).


 


 

Sunday, January 26 Observations:

Daily observations will be added later today.

 


 

Today – Wednesday: Cold Returns, Snow Stays South

As a moisture starved clipper tracks north of the area this morning, with the aid of a strong southwesterly flow in the lower levels temperatures have warmed up into the 20s north and west of NYC, but have surged into the upper 30s near NYC and coastal areas, marking the first time since exactly a week ago that temperatures have warmed up above freezing. Temperatures will continue to warm up until peaking in the late morning/early afternoon in the low-mid 30s north and west of NYC into south CT, and the upper 30s to low 40s in NYC and Long Island. The cold front is expected to move through in the early afternoon; most models depict the precipitation collapsing well to the west of the area, although especially given the current radar persistence, I am siding with the precipitation partially holding together as it reaches the Hudson Valley, with scattered rain showers mainly north of NYC late this morning into the early afternoon, considering temperature profiles from the surface to at least 850mb are warm enough to support liquid precipitation. Temperatures will then fall in the mid to late afternoon into the mid 20s-low 30s.

The final arctic cold outbreak for a while will occur on Tuesday, with another very cold air mass entering the Midwest and reaching the northeast US in a moderated form. The cold air mass and surface temperatures are not as cold as modeled 1-2 days ago, however, and along with a slightly slower cold front, temperatures will not be as cold as initially anticipated. High temperatures in the mid-upper 10s inland and upper 10s-low 20s elsewhere are expected on Tuesday, with a breezy westerly wind at 10-20 mph leading to wind chills near to below zero in the morning hours. Temperatures are likely to struggle falling below 10 degrees in the immediate NYC area, Long Island and coastal CT for both Monday and Tuesday nights, with highs on Wednesday likely to rise into the low to mid 20s.

The main feature to note is the frontal boundary stalling near the southeast US, where a wave of low pressure will form off the coast, and along with the very cold air mass is expected to produce a snowstorm for locations unusually far south, including eastern North Carolina/South Carolina, southern Georgia through Louisiana, and even parts of northern Florida, where up to 4-8 inches of snow are possible along with ice. The main question remains how far north the snow will spread; yesterday’s 18z GFS hinted at a potential for more widespread snow into the I-95 corridor, but mishandled the southern stream shortwave currently off the coast of California, speeding it up relative to the other models and phasing it with the northern stream trough, which ultimately brought snow just southeast of the area with many ensemble members supporting at least some measurable precipitation, if not moderate snow. Since then, however, the GFS has backed away from this depiction with the southern shortwave now remaining separate from the system, which is more in line with the remainder of the model guidance, suggesting that the 18z GFS run yesterday was an off run rather than beginning a short range significant northwest trend. The trough attempts to gain a neutral tilt but fails to do so, with snow from the wave of low pressure on Wednesday perhaps approaching the area but expected to remain to the south.

Thursday – Next Week: Warming Up, Rain/Snow Potentials Return

As the trough and southern snowstorm depart, the most significant warm up since mid January will take place, as both with the moderation of the cold air mass over Canada with a much smaller coverage area of below -20C 850mb temperatures, the collapse of western North American ridging that initially aided in the southward displacement of the cold air mass, and the development of a trough in the western US leading to a southwesterly flow aloft over the eastern US will prevent another arctic air mass from surging into the region for the late week. Temperatures are expected to return into the low-mid 30s on Friday as a weak cold front moves through with isolated snow showers likely, with a low pressure likely to develop along the frontal boundary and affect the region on Saturday, possibly into early Sunday. At this time, the GFS is flatter with rain/snow for the area and the ECM is more amplified with rain; preference is given to the ECM at this time with the overall synoptic setup likely to support a storm track near or north of the area. Early indications for Superbowl Sunday in northeast NJ are for partly sunny skies, a breezy westerly wind, and high temperatures in the upper 30s, although the outlook is subject to some changes depending on the evolution of Saturday night’s storm system.

Attention then turns towards the middle of next week when the next potential for a storm exists. As this is beyond the standard 180-hour range, confidence is lower regarding the specific details of the forecast, although there are strong signals supporting a potential storm system affecting the region on Wednesday and/or Thursday, with the low pressure track possibly near or inland of the area given persisting ridging over the southeast US and a trough in the western US. More information will be posted on this time frame as details become clearer.

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