textproduct: Wakefield

WHAT HAS CHANGED

Minor changes to storm total snowfall forecast, with amounts decreasing across the northern half of the area. Blizzard wording has been added to the Winter Storm Watch along the coast. A Cold Weather Advisory has been issued tonight for the Maryland Eastern Shore and Accomack County, VA. An Extreme Cold Watch has been issued for the entire forecast area Saturday night into Sunday.

KEY MESSAGES

1) High confidence that a strong winter storm impacts the region Friday night into Sunday. Significant accumulating snowfall, blowing and drifting snow due to strong winds, coastal flooding, and significant marine impacts are expected. The highest confidence is across south and southeastern portions of the area. There will likely be a very sharp gradient in total snowfall amounts, roughly along the US-360 corridor (potentially through the Richmond Metro).

2) A quick burst of light to moderate snow is possible Friday afternoon and evening ahead of the main winter storm, especially across portions of central and south central Virginia. Due to the very cold temperatures, any snow could quickly accumulate on surfaces, including roadways. This is a low confidence, but potentially high impact event.

3) Well below normal temperatures remain through early next week, keeping localized impacts (i.e icy roads) in place through the weekend. The coldest air wind chills are expected Saturday night into Sunday morning and an Extreme Cold Watch has been issued for the entire forecast area. A Cold Weather Advisory is in effect tonight for portions of the Maryland and Virginia Eastern Shore.

DISCUSSION

As of 315 PM EST Thursday...

KEY MESSAGE 1...High confidence that a strong winter storm impacts the region Friday night into Sunday. Significant accumulating snowfall, blowing and drifting snow due to strong winds, coastal flooding, and significant marine impacts are expected. The highest confidence is across south and southeastern portions of the area. There will likely be a very sharp gradient in total snowfall amounts, roughly along the US-360 corridor (potentially through the Richmond Metro).

Disagreement still remains higher than what is typically seen during this time range (especially on the NW side) amongst the deterministic and ensemble guidance in regards to total snow amounts/locations of the higher snow amounts across the area. The main mode of disagreement continues to be the battle zone between drier air from the N/NW associated with a very strong area of high pressure (~1045 mb) over the Plains, and an intense low pressure system developing off the SE coast late Friday night/Saturday. The disagreements in regards to snow amounts can be seen well in the probabilistic snowfall range amounts. If we use Richmond as an example, the 25th percentile shows 1" and the 75th percentile shows 8". For Norfolk, the ranges are a bit "closer" with the 25th being 6" and the 75th being 10".

Diving into the individual models/ensembles, the ECMWF/EPS has actually expanded the higher snow amounts across the south and southeast compared to some of the previous runs, with a very sharp cutoff north (unfortunately right near the Richmond metro). The Canadian has also moved a touch north with the ~3-6" amounts, but keeps the 6"+ amounts mainly confined to the southeast. Finally, the GFS/GEFS has trended south with the highest amounts (especially compared to the 00z/29 run), keeping a majority of the 6"+ amounts across the far south/southeast and the overall highest amounts just south of the CWA across NC. Finally, we are just starting to come into range of the CAMs which may provide a bit more clarity this evening and tonight. For now, the forecast resembles a blend between the previous forecast and the latest model guidance. Overall, snow amounts were lowered ~1-2" across the forecast area this afternoon, with amounts ranging from 0.5-2" across northwestern portions of the forecast area, to ~2-5" through the Richmond metro to the Tri- Cities, to 4-7" across south central Virginia over to Eastern Shore, to 7-12+" across southeast Virginia (Hampton Roads) into northeast North Carolina.

One trend that continues in most of the models is a "piece" of the surface high over the Plains ridging SE into the local area Friday into early Saturday, with low pressure across the eastern Gulf coast showing an inverted trough extending north into the southern Appalachians. This has trended to an initial overrunning precip event (all snow). For the Piedmont, this portion of the storm may account for a majority of the snowfall. SLR values will be very high, 15:1 to 18:1 so even a relatively low amount of QPF could lead to a significant accumulation (which will be efficient on area roads given temperatures well below freezing).

Part 2 of the storm gets amped up later Saturday, and is expected to peak Saturday night into early Sunday. The models (even the GFS) are all in pretty good agreement that the digging upper trough becomes cutoff as it drops SE from the TN Valley (at 12Z/Sat), to the GA-SC coastal plain by Saturday evening (00Z/Sun). The resulting low is forecast to deepen by as much as 15 mb/6 hr Sat evening as it drifts NE off the coast. Therefore, in addition to heavy snowfall, which is of highest confidence across SE VA and NE NC, very strong winds are likely to develop for coastal areas, with winds rather strong even for inland zones. Strong winds and a significant snowfall are expected within the Watch, with highest confidence across southern/SE VA and NE NC. Added blizzard wording to the Winter Storm Watch for portions of Hampton Roads and coastal northeast North Carolina and Blizzard Warning may likely be needed for these locations. Winds may gust to 50-60 mph along the coast Saturday night into Sunday.

Please keep a close eye on the forecast over the next 24 hours, with forecast confidence remaining below average for this timeframe. A ~50 mile shift in the coastal low will have drastic impacts to the final snowfall amounts. Additional messaging and headlines will need adjustments over the next few forecast cycles.

KEY MESSAGE 2...A quick burst of light to moderate snow is possible Friday afternoon and evening ahead of the main winter storm, especially across portions of central and south central Virginia. Due to the very cold temperatures, any snow could quickly accumulate on surfaces, including roadways. This is a low confidence, but potentially high impact event.

Latest CAMs, including the 18z HRRR and NAM 3km show the potential for light snow developing across areas south of I-64 Friday afternoon/evening. If snow does fall, there is a possibility (~20 to 40% probability) of accumulations up to 0.5". Air temperatures will be well below freezing during this timeframe, allowing for efficient accumulation on all surfaces. While this scenario is fairly low confidence, there could be significant travel impacts if it does happen.

KEY MESSAGE 3...Well below normal temperatures remain through early next week, keeping localized impacts (i.e icy roads) in place through the weekend. The coldest air wind chills are expected Saturday night into Sunday morning and an Extreme Cold Watch has been issued for the entire forecast area. A Cold Weather Advisory is in effect tonight for portions of the Maryland and Virginia Eastern Shore.

Tonight will again be very cold, though winds are expected to be light as high pressure extends into the area, keeping wind chills near ambient temps that will mostly be in the teens or mid to upper single digits NW. However, there will be enough of a light breeze tonight across portions of the Eastern Shore to allow for wind chills to drop into Cold Weather Advisory territory. As a result, another Cold Weather Advisory has been issued tonight into Friday AM for the Maryland Eastern Shore and Accomack County, VA where wind chills as low as 0 are expected. Friday will see highs struggle to get out of the mid 20s for much of the northern half of the area. Saturday will be even colder with highs in the low to mid 20s for most. An Extreme Cold Watch has been issued for Saturday night into Sunday morning where the combination of a strong N to NW wind and air temperatures in the low to mid teens will result in wind chills as low as 0 to 10 below.

AVIATION /20Z THURSDAY THROUGH TUESDAY/

As of 1210 PM EST Thursday...

VFR conditions are expected to prevail through the TAF period. Skies will remain FEW-SCT250 today. Winds are NW at 6-10kt with a few gusts to 18kt along the coast. Winds become NNW to NNE this evening and overnight. Mid level clouds will develop during the later morning to mid-day hours of Friday.

Outlook: A winter storm will impact the area later Friday through Sunday. Snow could start across the Piedmont, including FVX and possibly RIC (though lower confidence), Friday afternoon. It's then expected to spread eastward to include most terminals overnight into Saturday. May become +SN with low VIS Sat night into Sun morning. Winds will also become strong later Sat, with the highest gusts closer to the coast. Widespread flight restrictions are possible with this storm.

MARINE

As of 320 PM EST Thursday...

Key Messages:

- Small Craft Advisories remain in effect across the coastal waters north of Parramore Island into this evening.

- Confidence remains high in high-end Gale to Storm conditions this weekend as a strong coastal low develops off the Carolinas. Freezing spray and high seas are expected this weekend.

- Coastal flooding is increasingly likely across the Lower Chesapeake Bay, Lower James River, and Virginia Beach and eastern Currituck Counties Sunday morning.

NW winds 10-15 kt with gusts up to 20 kt across most of the local waters and 15-20 kt with gusts up to 25 kt across the northern coastal waters north of Parramore Island were noted this afternoon. As such, have ended all SCAs except for the coastal waters north of Parramore Island where they remain in effect until 7 PM. Additionally, while some light freezing spray remains possible through tonight, it appears marginal enough to refrain from issuing additional Freezing Spray Advisories at this time.

Strong high pressure builds south from the northern Plains into the Gulf Fri into Sat. Meanwhile, a coastal low is expected to develop off the Southeast coast Fri night into Sat before tracking ENE off the coast through Sun. Most model guidance shows the potential for quite impressive pressure falls with WPC depicting a 980mb low off of the Outer Banks by 12z Sun. Recent model trends have favored a farther south track of the low which has resulted in slightly lower winds forecast for the local waters. However, there remains a moderate-high potential for widespread Storm conditions this weekend across the Ches Bay, coastal waters, Lower James River, and Currituck Sound with Gale conditions likely across the upper rivers. The probability for 48 kt gusts was 30-60% across the Ches Bay (highest across the Lower Bay), 40-65% across the northern Coastal Waters north of Cape Charles Light, and 70-80% across the southern coastal waters south of Cape Charles Light. Therefore, have maintained all Storm Watches and Gale Watches. Seas of 8-12 ft across the northern coastal waters and 10-15+ feet across the southern coastal waters (highest across the NC coastal waters) are expected given the strong winds. Additionally, given the high probability for snow (potentially heavy), periods of zero visibility are increasingly likely across the coastal waters Sat into Sun. Winds become NW behind the low and gradually diminish Mon.

Tides/Coastal Flooding...

Given the strength of the low coinciding with higher astronomical tides, widespread coastal flooding is increasingly likely with the Sun morning high tide. Moderate coastal flooding remains possible across the Lower James River and lower Ches Bay Sun with moderate to locally major coastal flooding possible across the Mouth of the Bay and the Virginia Beach and Currituck Outer Banks coastline. Minor coastal flooding remains possible across the Atlantic coastline of the Eastern Shore. Will hold off on Coastal Flood Watches at this time, however, will likely need them in future updates as confidence increases. Additionally, given the strong N/NNW winds, low water levels are likely across portions of the middle Ches Bay and Currituck Sound. Low Water Advisories may be needed in future updates.

CLIMATE

Record Low Max Temperatures for Sat Jan 31:

- RIC: 23 (1948) - ORF: 25 (1936) - SBY: 24 (2019) - ECG: 29 (1965)

Daily Record Snowfall for Sat Jan 31 and Sun Feb 1:

- Date: Sat Jan 31 Sun Feb 1

- RIC: 7.0" (1948) 3.1" (1948) - ORF: 4.0" (1980) 4.0" (1910) - SBY: 4.0" (2010) 4.0" (1962) - ECG: 5.0" (1980) 7.0" (1948)

AKQ WATCHES/WARNINGS/ADVISORIES

MD...Cold Weather Advisory from 7 PM this evening to 10 AM EST Friday for MDZ021>025. Extreme Cold Watch from late Saturday night through Sunday morning for MDZ021>025. Winter Storm Watch from Saturday morning through Sunday afternoon for MDZ023>025. NC...Extreme Cold Watch from late Saturday night through Sunday morning for NCZ012>017-030>032-102. Winter Storm Watch from late Friday night through Sunday afternoon for NCZ012>014-030. Winter Storm Watch from late Friday night through Sunday evening for NCZ015>017-031-032-102. VA...Cold Weather Advisory from 7 PM this evening to 10 AM EST Friday for VAZ099. Extreme Cold Watch from late Saturday night through Sunday morning for VAZ048-060>062-064>069-075>090-092-093- 095>100-509>525. Winter Storm Watch from late Friday night through Sunday afternoon for VAZ092-093. Winter Storm Watch from late Friday night through Sunday evening for VAZ095>100-524-525. Winter Storm Watch from Friday evening through Sunday afternoon for VAZ060-061-065>069-079-087. Winter Storm Watch from late Friday night through Sunday afternoon for VAZ076>078-080>086-088>090-512>520-522-523. MARINE...Storm Watch from Saturday evening through Sunday evening for ANZ630-631-650-652-654. Storm Watch from Saturday afternoon through Sunday evening for ANZ632>634-638-656-658. Gale Watch from Saturday evening through Sunday evening for ANZ635>637. Small Craft Advisory until 7 PM EST this evening for ANZ650- 652.