12:15 PM | **Strong cold front arrives late this evening…powerful winds on Wednesday and Thursday…weekend snow threat continues**
Paul Dorian
A high-resolution (HRRR) forecast map at 10 PM later tonight with a band of showers and possible thunderstorms extending over the I-95 corridor associated with a strong cold front; courtesy NOAA/EMC, tropicaltidbits.com
Overview
The last couple of weeks were well above-normal in the eastern half of the nation, but this week will be a lot different with progressively colder conditions. In addition, winds will become quite a factor as they will become very strong on Wednesday and Thursday with gusts to 50 mph possible in the DC-to-Philly-NYC corridor. As far as precipitation is concerned, a strong and active cold front will arrive later this evening with occasional rain showers and there can be a rumble of thunder. Looking ahead, snow continues to be a threat for the weekend in the Mid-Atlantic region. The chances for significant snow this weekend in the DC-to-Philly-to-NYC corridor will ride on the timing of the phasing together of waves of energy in the northern and southern jet streams. Early indications suggest the phasing together of these two systems may not occur until they’re both offshore which would reduce chances for important snow accumulations in the I-95 corridor; however, it is way too early to write off a significant snowfall for the DC-to-Philly-to-NYC corridor.
12Z GFS forecast map for tomorrow afternoon with a tight pressure gradient across the Mid-Atlantic region; courtesy NOAA/EMC, tropicaltidbits.com
Strong cold front later this evening…mid-week strong winds
A strong cold front will arrive late this evening in the Mid-Atlantic region and it should result in occasional rain showers in DC, Philly and NYC and perhaps even some rumbles of thunder. It is also possible that a few snowflakes or ice pellets develop as cold air starts to pour in immediately following the frontal passage around midnight or so. Late tonight, winds will intensify out of the northwest and they’ll continue at very strong levels from Wednesday into Thursday with gusts to 50 mph possible. The pressure gradient will tighten on Wednesday between intensifying low pressure over New England and strong high pressure over southern Canada and this will result in widespread powerful winds throughout the Mid-Atlantic region – perhaps even some scattered power outages. Winds may slacken off a bit tomorrow night as diurnal heating dissipates only to resume at rather high levels again during the day on Thursday. Temperatures will actually drop some between today and Thursday and then highs may struggle to reach the freezing mark on Friday although winds will be considerably lower to end the work week.
12Z GFS forecast map for Saturday morning with two waves of energy in the upper atmosphere; courtesy NOAA/EMC, tropicaltidbits.com
Weekend snow threat continues
By the early part of the weekend, low pressure will be gathering strength over the Gulf of Mexico at the same time strong Arctic high pressure will slide east across south-central Canada. The strong high pressure to the north and northwest will provide enough low-level cold air for the upcoming weekend to likely result in snow in the I-95 corridor and points to the west and north. The upper atmosphere will feature two waves of energy by early Saturday – one in the northern jet stream over the western Great Lakes and the other down in the south-central US.
12Z GFS forecast map for Sunday evening with the same two waves of energy in the upper atmosphere trying to consolidate just off the east coast; courtesy NOAA/EMC, tropicaltidbits.com
Early indications are that these two upper-level systems may not phase together until both systems are just offshore and this late phasing would inhibit chances for significant snow in the DC-to-Philly-to-NYC corridor. However, there a few days to go and these upper-level features are still a long way away so there is time for the timing of the potential phasing to change. As it stands now, it looks like some accumulating snow is a good bet in the Mid-Atlantic region this weekend probably beginning during the PM hours on Saturday, but stay tuned as it is just a bit early to determine if it will be a significant snowfall.
12Z Euro is a bit more bullish today on snow prospects for the weekend in the Mid-Atlantic compared to its most recent model runs; map courtesy WSI, Inc., ECMWF