textproduct: Wakefield

WHAT HAS CHANGED

Increasing confidence for a major winter storm this weekend and very cold temperatures behind it. Recent model guidance continues to maintain more mixed precipitation and freezing rain than pure snow. Additionally, a Cold Weather advisory has been issued throughout the entire area for Friday night into Saturday morning as wind chills drop to the single digits or low-end negatives for far northern portions.

KEY MESSAGES

1) High confidence in a major winter storm impacting the region with increasing confidence regarding the precipitation types. Users should continue to keep a very close eye on the forecast over the coming days.

2) A Cold Weather Advisory has been issued for the entire forecast area for Friday night into Saturday morning ahead of the winter storm as wind chills drop to the s low-end negatives to single digits behind a strong Arctic blast of cold temperatures.

3) A prolonged period of very cold temperatures is increasingly likely from Saturday into at least the middle of next week with the potential for temperatures to remain below freezing for several days. Impacts from the winter storm are likely to last well into next week due to the very cold temperatures.

DISCUSSION

As of 245 AM EST Thursday...

KEY MESSAGE 1... High confidence in a major winter storm impacting the region with increasing confidence regarding the precipitation types. Users should continue to keep a very close eye on the forecast over the coming days.

Winter Storm Watches remain in effect for the entire area outside of far southeastern portions across Northeast North Carolina as confidence continues to increase in widespread snow, sleet, and freezing rain impacting the area Saturday into Sunday.

Confidence continues to increase in a Miller B low track bringing widespread snow, sleet, and freezing rain to the local area. A very strong Arctic cold front pushes into the local area Friday night into Saturday with very cold temperatures. Additionally, inverted trough sets up over the southeast US and a CAD setup develops over the local area as strong high pressure (1045+ mb) builds over the Midwest and moves east. The cold front that moves through the area will stall over the southeast CONUS and a low pressure will form along it in the Gulf, then moving towards the Appalachian mountains. At the same time, a secondary low will form off the Carolina coast and moves to the north. With this set up, there will be ample moisture with P-WATs ranging in the 200-300% above normal range.

A variety of precipitation types are expected in this setup with big differences from the NW portions of the area to the SE portions. The cold air at the surface will hold strong from the CAD reinforcement. Warmer air (above freezing) likely intrudes into the far SE, and possibly the Eastern Shore and slightly further inland, at the surface and a warm nose of above freezing temperatures around the 850 mb level will make for a very messy situation with all p-types present across the forecast area. Where the warm nose and thickness levels end up across the forecast area will be the ultimate determining factor for the p-types. This is where the greatest uncertainty remains amongst models. Right now, far northern portions of the area are favored to receive mostly snow/sleet, and the majority of the area (mainly south of I-64 and along/west of I-95) favors freezing rain, and the far SE favors plain rain. This does not mean that only these p-types will be seen in these area, as a shift in the thermodynamics could cause multiple p-types at once across the area. Whatever form of wintry precipitation that does fall will be significant.

The confidence in the system beginning as snow remains high across the area starting Saturday afternoon/evening. The highest snowfall amounts continue to be in the northern portions of the area with a 40-80% chance of 6" for the Richmond metro northwards with the highest chance in the northern tier of counties, and only a 10-40% chance for 6" across the VA border to the metro areas. There will be a sharp cutoff of snowfall totals from the north to the south. In addition to the snow, a few inches of sleet is possible with the deterministic GFS and Canadian models showing up to 1-3" on top of the snow.

After the initial onset of snow, the warmer temperatures aloft (and at the surface for the SE) will creep up into the area Sunday. With this, p-types will begin to shift and a good portion of the area may see significant to potentially catastrophic ice impacts. The latest NBM runs shows a 70-100% chance of 0.25" of ice for the interior portions of the area, including the southern piedmont and Richmond metros. There is increasing probabilities for 0.50" of ice for the same areas with the latest NBM showing a 50-70% chance. These amounts of ice would become very dangerous with widespread power outages. Even more alarming is the EPS and Canadian Ensemble show a mean of over 1.00" of ice. Ice accumulation of this magnitude would likely result in major travel impacts as well as widespread and long- lasting power outages. Ice amounts will continued to be heavily monitored with future forecasts.

Everyone should take note and begin to make preparations for a significant snow/icing event as moderate to major (potentially extreme) impacts are looking increasingly likely from this storm. In addition, after effects from the storm will likely last well into the work week due to very cold temperatures.

KEY MESSAGE 2... A Cold Weather Advisory has been issued for the entire forecast area for Friday night into Saturday morning ahead of the winter storm as wind chills drop to the s low-end negatives to single digits behind a strong Arctic blast of cold temperatures.

Ahead of the major winter storm, a strong cold front will moves across the region early Friday bringing a strong, cold Arctic airmass to the area. Behind the front, northerly winds will be breezy overnight and in the early morning around 10-15 mph with gusts to 25 mph. This combined with temperatures in the teens will allow the wind chill (or feels-like) temperatures to drop to the low- end negatives for northern portions of the area to near 10F in NE NC. In conjunction with the wind chill, Cold Weather Advisories have been issued for the entire forecast area from Friday late Friday evening through Saturday morning.

KEY MESSAGE 3... A prolonged period of very cold temperatures is increasingly likely from Saturday into at least the middle of next week with the potential for temperatures to remain below freezing for several days. Impacts from the winter storm are likely to last well into next week due to the very cold temperatures.

Behind the strong Arctic front Friday and winter storm, strong high pressure (~1030 mb) from the Canadian plains will shift over the SE CONUS with potent upper level troughing will keep very cold temperatures over the area through at least the middle of next week. This... along with any snowpack... will likely keep high temperatures below freezing for an extended period of time with extended model guidance showing through early February. Low temperatures in the single digits inland (mid teens coastal) on Monday night into Tuesday will likely be the coldest, with lows in the lower teens to upper teens through at least mid week. This does not take in account for wind chill which could be below zero. Will note that SE VA/NE NC will likely see above freezing high temperatures Sunday and Monday and highs hovering around freezing through mid week. This prolonged period of very cold temperatures behind the winter storm could be quite dangerous for those without power. It is important that all take precautions in event that power is unable to be restored in a timely manner.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

As of 600 PM EST Thursday...

VFR conditions prevail through the 00z TAF period. Cloud cover continues to increase across the region this evening with a brief period of clearing or partial clearing tonight around midnight. However, cloud cover builds back into the area late tonight into Friday. A few light showers are possible across SE VA/NE NC late Friday morning into Friday afternoon, however, confidence is too low at any given terminal to reflect in the TAFs. Winds remain light and variable tonight through Friday ahead of a strong cold front.

Outlook: Winter weather is likely this weekend across all terminals, with a more prolonged period of winter weather likely at RIC, SBY, and PHF. Initial snow likely mixes with and changes over to sleet and freezing rain with an eventual changeover to plain rain possible along the coast as warmer air gets pushed onshore. However, uncertainty regarding winter impacts at ORF and ECG is higher. An extended period of degraded flight conditions is expected to continue through Sunday night.

MARINE

As of 250 PM EST Thursday...

Key Messages:

- Gale Warnings have been issued Friday night for the Chesapeake Bay and coastal waters south of Cape Charles Light. A Small Craft Advisory has been issued north of Cape Charles for Friday night into Saturday evening.

- Another period of strong NE winds is likely Sunday, as developing coastal low pressure develops along the stalled surface front. A brief period of benign boating conditions is ongoing across the local waters, with W-SW winds of 5-10 kt. Seas 2-3 ft, waves ~1ft. Mainly benign conditions tonight, despite a mainly dry cold front crossing the region overnight which will veer winds around to the NNW. Cold air advection behind the initial front is rather weak. However, a secondary/reinforcing cold front crosses the area Friday evening. Strong cold advection behind that front quickly increase to (NNW) 25-30 kt and gusts to 35 kt over the bay and southern coastal waters, with SCA conditions farther NE along the middle and upper Atlantic coast. In-house wind probs have increased to 60-80% in this area for Gale Force gusts, and have accordingly converted the Gale Watch over to a Gale Warning. Probs are much lower over the middle and northern coastal waters, with stronger pressure gradient remaining farther south. For that reason, have gone with longer duration Small Craft Advisory over this area through Saturday afternoon.

Winds decrease below Gale thresholds on Saturday but will remain solid SCA, and Gales will likely need to be replaced by SCA for a time over the Gale Warning area. Will hold off on headlines for Sat night and Sunday. There could be another brief duration of Gale Warnings Sunday morning, but will re-evaluate that in later cycles as we get closer, in hopes that uncertainties regarding exact location of developing/track of coastal low pressure Sunday into Monday becomes more clear. Regardless, it appears that at least SCA conditions persist into early next week, with a narrow area of Gales possible over central/southern portions of the area. Strong cold advection returns on the back side of the departing low through sunrise Tuesday. Waves and seas will build along with the stronger winds early Saturday and likely peak on Sunday in the 3-5 ft and 6-9 ft ranges, respectively. Freezing spray will be an ascending concern during this period as well, especially Monday night and Tuesday as Arctic high pressure quickly builds across the eastern CONUS.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...Cold Weather Advisory from 8 PM Friday to 10 AM EST Saturday for MDZ021>025. Winter Storm Watch from Saturday afternoon through Monday afternoon for MDZ021>025. NC...Cold Weather Advisory from 8 PM Friday to 10 AM EST Saturday for NCZ012>017-030>032-102. Winter Storm Watch from Saturday afternoon through Monday afternoon for NCZ012>014-030-031. VA...Cold Weather Advisory from 8 PM Friday to 10 AM EST Saturday for VAZ048-060>062-064>069-075>090-092-093-095>100- 509>525. Winter Storm Watch from Saturday afternoon through Monday afternoon for VAZ048-060>062-064>069-075>090-092-093- 095>100-509>525. MARINE...Gale Warning from 10 PM Friday to 7 AM EST Saturday for ANZ630>632-634. Small Craft Advisory from 6 PM Friday to 6 PM EST Saturday for ANZ650-652-654. Gale Warning from 10 PM Friday to 10 AM EST Saturday for ANZ656-658.