textproduct: Wakefield

WHAT HAS CHANGED

Winter Weather Advisories continue for the Northern Neck, western portions of the Middle Peninsula, and MD Eastern Shore. 1" to locally 2" is forecast in the advisory area, with 0.5-1" elsewhere, and lower amounts in far SE VA/NE NC. Uncertainty continues to remain higher than normal given marginal temperature conditions which could limit accumulations.

KEY MESSAGES

1) Confidence is moderate-high in portions of the area seeing some wet snow today, with the most likely timing for snow from 3-8 PM. 1" to locally 2" is expected across the VA Northern Neck and MD Eastern Shore, where Winter Weather Advisories are in effect. 0.5-1" is expected elsewhere, with lesser amounts for southside Hampton Roads and coastal NE NC. However, uncertainty remains due to marginal surface temperatures.

2) A strong push of Arctic air arrives on Monday and especially Monday night behind a secondary dry cold front, with below average temperatures to continue through the first half of the week.

3) Another storm system may impact the area next weekend, but it is way too early for specifics at this time.

DISCUSSION

As of 225 PM EST Sunday...

KEY MESSAGE 1...Confidence is moderate-high in portions of the area seeing some wet snow today, with the most likely timing for snow from 3-8 PM. 1" to locally 2" is expected across the VA Northern Neck and MD Eastern Shore, where Winter Weather Advisories are in effect. 0.5-1" is expected elsewhere, with lesser amounts for southside Hampton Roads and coastal NE NC. However, uncertainty remains due to marginal surface temperatures.

A fast moving shortwave at the base of an upper trough (currently in the western Carolinas as of 2 PM this afternoon) is forecast to strengthen as it takes on a slight negative tilt just before it crosses the area between 4-7 PM. At the surface, low pressure off the Carolina coast deepens while tracking NE through today before exiting well to the NE tonight. Steady rain continues across much of the area, and we have started to see temperatures and dew pts drop a few degrees as weak CAA ensues from the NNW. Precipitation will peak in intensity later this afternoon before quickly ending between 5-8 PM after the shortwave pushes through. Mesoanalysis shows that 925-850mb temps are between - 1 and -3C. Still, precip is rain as a melting layer around 1000-1500 ft AGL is still evident on both the AKQ and RAX radars. Precip has changed to snow to our SW at GSO/INT (near the back edge of the precip). As has been mentioned before, the key to whether precip can change over to snow will be the thermal profiles in the lowest 1000- 1500 ft AGL. If it can drop to 32-33F for a few hours due to wet- bulb/column cooling effects, then a period of accumulating snow is likely (mainly on grassy/elevated surfaces). On the other hand, if it doesn't drop below 34-36F, precip will remain predominantly rain with perhaps a brief period of snow at the tail end of the precip during the early evening. Additionally, snow will be more likely where precip rates are heavier. The 12z guidance has trended toward the latter scenario (less snow) with only 1-3 hours of snow possible as the precip ends across the Piedmont, central VA, the northern neck, and eastern shore. The cold air likely doesn't arrive in time for any snow accums across southside Hampton Roads and NE NC, but am expecting at least a light coating elsewhere. As such, will keep at least 0.5" of snow in the forecast in most areas aside from SE VA/NE NC. The best chance for 1-2" is from the Northern Neck onto the Eastern Shore, coinciding with the best overlap of dynamic cooling effects and mid-level frontogenesis. Winter Weather Advisories remain in effect for these areas, in addition to western portions of the Middle Peninsula.

Regardless of any headlines, would expect any accums to be mostly confined to grassy and elevated surfaces and not roadways. We could see accums on roadways if it snows hard enough for a couple of hours, though not that confident in this. A reasonable worse case scenario would be 2" for most of the area with 1" for SE VA and NE NC, mainly if precip intensity can overcome marginal sfc temps. Colder and drier air arrives from NW-SE this evening bringing a rapid end to the precip. Will also have to monitor for any freezing of residual wet/slushy surfaces tonight.

KEY MESSAGE 2...A strong push of Arctic air arrives on Monday and especially Monday night behind a secondary dry cold front, with below average temperatures to continue through the first half of the week.

Arctic air arrives Monday night behind a secondary cold front. Very cold temperatures are expected from Monday through Wednesday, with the coldest air occurring Monday night, Tuesday, and into early Wednesday morning. EPS/GEFS continue to show 2m temperature anomalies 15F to nearly 20F degrees below average. Overnight lows in the upper teens to mid 20s are expected Sunday night, and primarily teens Monday/Tuesday night. While it will be very cold Monday and Tuesday nights, the wind looks to be low enough for wind chills to be around 5-10F above Cold Weather Advisory criteria. The best chance of seeing wind chills meeting criteria is on the Eastern Shore Monday night. While day-time temps will be rather chilly each day Monday through Wednesday, Tuesday is forecast to be the coldest day with highs struggling to make it above freezing north of I-64.

Temperatures may attempt to moderate a bit by the middle and end of the week as the upper flow turns more zonal. However, daily highs still look to be slightly below normal. While it also looks mainly dry, a series of fronts toward the end of the week could bring sporadic/light precip.

KEY MESSAGE 3...Another storm system may impact the area next weekend, but it is way too early for specifics at this time.

Despite the slight moderating trend is expected late this week, Arctic air is expected to remain entrenched across north and northeast portions of the CONUS through late week into next weekend. The flow aloft largely remains zonal but very strong (~1050mb) Arctic high pressure is progged to build into the north-central CONUS by next Saturday. A couple of fast moving shortwaves may track over the area next Sat and or Sun, which could bring chances for more widespread precip. There is ensemble support from the GEFS, EPS, CMCE, and the AI ensembles for wintry wx across a decent portion of our area, which seem reasonable given the strong supply of cold air to our N. Ultimately, exact precip types will be highly dependent on impossible-to-resolve (at this range) storm tracks. Will continue to monitor over the next several days.

AVIATION /19Z SUNDAY THROUGH FRIDAY/

As of 1225 PM EST Sunday...

Widespread rain continues across the terminals early this afternoon except at RIC. Precip should move back into RIC in the next hour or so. CIGs have dropped to MVFR-IFR, and should drop to IFR at all terminals by ~20z. Precip will continue through 23-01z, with 2-4 SM VSBYs in rain. The rain likely changes to snow or a rain/snow mix at RIC and SBY during the afternoon, with light snow possible for a few hours (most likely from 21-00z). There could be an hour or two of -SN with IFR VSBYs at PHF/ORF between 22-01z, with mainly rain at ECG. Conditions quickly improve to VFR tonight as drier air moves in behind the departing system. Winds remain below 12 kt through tonight, but become a bit gusty (to ~20 kt) out of the WSW on Monday.

Outlook: Dry/VFR Monday morning through Wednesday. A cold front potentially crosses the area Thursday with only a 20% chance of showers at this time.

MARINE

As of 225 PM EST Sunday...

Key Messages:

- Small Craft Advisories remain in effect for the Chesapeake Bay and coastal waters this afternoon into tonight due to the potential for 20 to 25 knot wind gusts.

- Another round of SCAs is possible Monday night into Tuesday as another cold front crosses the waters.

Afternoon weather analysis shows a weak low pressure system just off the coast of Virginia. The pressure gradient from this system continues to remain weak and winds are light out of the north between 5 to 10 kt with gusts upwards of 15 kt. Latest buoy obs are showing low seas with waves around 1 ft in the bay and 2 to 3 ft across the ocean. Through the rest of the afternoon and into tonight the low pressure will strengthen causing the pressure gradient to tighten. This will allow for winds to increase across the waters. Winds increase to 15 to 20 kt with gusts upwards of 25 kt with possible gusts upwards of 30 kt across the coastal waters. With the increase in winds waves will also increase to 2 to 3 ft across the bay and 3 to 5 ft across the waters. Small Craft Advisories have been issued for the bay, sound, and coastal waters lasting starting from 4pm and lasting through 1am tonight. The rivers will remain just shy of criteria however, a brief 20 kt gust cannot be ruled out. Early Monday morning through early Monday afternoon there will be a lull in the winds as the low pressure moves further off the coast and the pressure gradient weakens. Winds will shift to the SW and will be between 10 to 15 kt. By Monday afternoon, Winds will increase and remain out of the SW as a strong cold front approaches. Local wind probs have increased to 90%+ for gusts >= 18 kt gust and 80-90% of gusts >=25 kt across the northern 3 ocean zones. With the strong pressure gradient expected and high wind probs additional SCA will likely be needed for Monday afternoon into Tuesday morning. Generally benign, sub-SCA, conditions take hold through the midweek timeframe before another system potentially approaches next weekend.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...Winter Weather Advisory until 10 PM EST this evening for MDZ021>025. NC...None. VA...Winter Weather Advisory until 7 PM EST this evening for VAZ064- 075>078-085-517>522. MARINE...Small Craft Advisory until 1 AM EST Monday for ANZ630>632-634- 650-652-654. Small Craft Advisory until 10 PM EST this evening for ANZ633- 656-658.