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January 3, 2022 CAPE Storm Obs/Nowcast


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Nice discussion from Mount Holly. Mention of blizzard conditions for coastal DE. 

Spectacular satellite imagery over the East this morning as a strong area of low pressure comes together to our southwest. Just a classic eastern US winter storm presentation. A blossoming shield of precipitation is now overspreading the local area. A major winter storm will affect southern portions of the area over the next 18 hours. The main change to the forecast overnight was an increase in QPF, and by association, snowfall, for areas previously within and that were just north of the previous Winter Storm Warning. The QPF increase is almost unanimously supported by the last two cycles of global and hi res guidance, and translates to an increase in snow totals. The most difficult portion of the forecast remains the northward extent of precipitation shield. Even many of the recent model runs which increased QPF across the south generally didn`t move the precipitation shield north much. The latest blend does bring amounts up somewhat in the I-95 corridor. However, there is likely to be an exceptionally sharp northern cutoff to accumulating snow, probably even sharper than the latest forecast, which as it is has a much sharper than normal gradient. Even across, for example, Philadelphia County, it would not be surprising to see a significant difference in totals. And for northern portions of the area, it will simply be a cloudy and cold day with perhaps some flurries. Confidence in snowfall is much greater for southern areas. It is clear now that a swath of heavy precipitation will overspread the region. Extreme frontogenetic forcing is allowing precipitation to expand in coverage and intensity to our southwest, and this will only continue today. While precipitation is beginning as rain in some places, temperatures are continuing to cool behind yesterday`s front, and a flip to snow will occur. One possible exception is far southeast Delaware, where rain or mix could hold on for longer. Amounts were reduced a bit there. Otherwise, a large stripe of 8 to 12 inches of snow is now forecast, and can`t rule out some localized amounts a little over 12 inches. Snowfall to our southwest has generally been over-performing, and this trend could continue into our area. Snowfall rates could easily exceed 1 inch per hour at times this morning, perhaps 2 inches per hour. While snow ratios overall will be less than 10:1, these rates will quickly overwhelm the warm ground conditions left by recent near record warmth. These snowfall rates could persist for several hours this morning and early afternoon. Banding features are certainly possible within the heavy snow shield, leading to some local variations. Eventually, precipitation will end from west to east late this afternoon and this evening as the area of low pressure moves out to sea. Northeast winds will become strong near the coast today, gusting in the 30 to 40 mph range for several hours. With heavy snow occurring through this period, a period of near blizzard conditions is possible for areas such as Sussex County DE and portions of Cape May and Atlantic Counties. A Blizzard Warning was contemplated, but am not confident enough in criteria being met for more than brief periods.

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Just now, SnowenOutThere said:

Hey, don’t know if people saw this but wanted to make sure they did. Isn’t 994 far lower than what the models have/had at this time. I checked the NAM and it had 998 or 997, would this be a significantly good sign for a better storm if this is the case?

Good eye. Let’s see if it translates to anything (More expansive shield northward or heavier qpf) 

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Whichever areas can stay all snow JUST Nw of the r/s line in Virginia and E MD / DE are going to get hammered. Usually can find the heaviest precip near the fall line. Looks like Charlottesville over to culpelper are currently in this zone. Nice band moving into Manassas as well  

10C7850B-F9C6-4BC7-89F1-6EA90E88CEBD.jpeg

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1 minute ago, CAPE said:

Just a note about the teleconnections currently: -AO, -NAO, and yes a -PNA. WPO is also significantly negative. Southward displaced TPV lobe underneath that HL block. Pretty classic h5 look for a MA winter storm, with lots of red up top.

Just goes to show how much timing means with weather. We don’t need the trifecta +PNA -AO -NAO setup to score  

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