1/19 Light-Moderate Snow Event

Synoptic Setup 

A vigorous shortwave/trough will move through the area around tomorrow at midday, providing strong lift to generate snow and sufficient dynamics from the strong upper jet, in addition to PVA and modest WAA. These dynamics will allow heavy precip to be brought about just ahead of the shortwave and a more expansive precip shield, which guidance has been trending to. Guidance, in addition to the more expansive precip shield, has brought the vort-max further south, allowing for higher amounts of QPF. The heaviest snow/concentration of precip will just be north of the vort-max; putting us in a more favorable position. 

This is ahead of a great antecedent airmass, with already existing snow cover contributing to it even more. However, the absence of deep moisture, and generally low precip amounts, as well as the general storm being too progressive will inhibit this from becoming a major storm - despite the favorable H500 pattern. Nonetheless - a moderate storm for the area is looking likely, with ample cold. Ratios will be high due to a cold, saturated profile in the DGZ and the rest of the column, leading to modest dendrite growth. Surface temps will also be in the upper 20s and lower 30s the entire event; below freezing the entire time. 

We should see a good thump of snow not too far from onset; making morning commute extremely hazardous. Shortwave forcing by that time is very good and would support locally heavy rates; despite low lift in the DGZ. This will likely be another high-ratio, generally low-rates event. Roads will become slick and snow-covered extremely quickly, with lingering snow expected to last through the evening rush hour. Thus, most schools/offices have closed in person. Snow will continue throughout the rest of the day, but will become lighter after the morning thump. 

Snow Map

This is my forecast:

I went extremely bullish due to the uptrends today and the overall setup. The most snow will be N of I70 in NE MD due to great dynamics and precip from the IVT(which won't have that much of an impact closer to DC). N of I-66 should generally see 2-4"+ (why I brought my 3-5"+ zone further south), with the south of it generally seeing 1-3". Although this is bullish -  please keep in mind that just cause a specific area is in the 3-5"+ zone doesn't mean they will be seeing the higher amounts of the range. Most areas S of 70 in that zone will likely stay under 5". The further north and east you are, the better for this setup(outside of the mountains). The exact location of the bands and the heaviest QPF/snow are uncertain, thus why I added the plus for any isolated spots above the range. The general consensus should be another nice high-ratio, low-rate snow event - on top of already existing snow, something that is quite rare in the mid-Atlantic. This storm will have a large impact on the morning commute and bring about hazardous travel.

Additionally, radar looks good right now, with virga saturating the column currently, as well as a decent precip shield in the OH Valley/Midwest. MPING reports confirm this is all reaching the ground over there. Earlier today, HRRR underdid the moisture in IA and didn't see the snow shield reaching Cincinnati (all related to our storm system). Current observations look good so far and aren't indicative of any major concerns.

Overall, the last-minute uptrend on the vort-max being further south and a more expansive, robust precip shield have led to totals becoming higher in the DMV.

Here are the current NWS warnings/advisories map, and precip onset: