Swell Matrix

Area Forecast Discussion

National Weather Service Newport/Morehead City Nc

1055 pm EST Wed Jan 17 2018

Synopsis

A cold front will cross the area late this afternoon and evening. Low pressure will develop along the front offshore tonight. Both systems are forecast to produce snow across Eastern North Carolina this evening and tonight. High pressure will build in from the west Thursday through the weekend. A cold front will cross the region Monday night followed by high pressure Tuesday and Wednesday.

Near Term

Until 6 am Thursday morning As of 11 PM Wed, Little changes for the late evening update. The coastal low is continuing to deepen along hte coast with precip increasing across the eastern half of the forecast area. Rain has changed to snow across the Crystal Coast and expect it to continue to transition to the east through the overnight.

Previous discussion, Compact upr trough is pivoting through the deep south and wrn Carolinas this afternoon, and becoming negatively tilted per latest H2O vapor imagery. This will promote cyclogenesis offshore of the NC coast this evening, and be the focus for periods of snow, heavy at times, tonight.

First, mesoscale snow band just west of the coastal plain has been hammering the Piedmont with heavy snowfall. This band is edging eastward towards E NC, though will begin to weaken as energy is transferred offshore to the developing low. Warm sfc temps across E NC as many areas have topped out in the upr 40s/low 50s this afternoon, so the snow will have a tough time to begin accumulating on area roadways initially.

With the warm temps in the boundary layer, rain is initially expected this afternoon, before a transition to a rain/snow mix and then quickly to snow northern and western zones very late this afternoon through the early evening. The last places to switch to snow will be the Crystal Coast, then finally the southern OBX. A general 1 to 2 inches still expected for the counties under winter wx advisories through this evening.

General thinking for snowfall amounts overnight has not changed too much from previous assessments this morning. With a deepening low offshore, large scale lift occurs aloft as coastal areas will be under right entrance region of upr jet. Mid level fgen maximized this evening to the early morning hours, as large omega vals collocated with DGZ for several hours. Thus, best opportunity to pick up 2-3 inches of snow appears to be across the coastal locales. Along the OBX, localized totals of up to around 4 inches are expected. Localized higher amounts possible if heavy meso banding sets up. Latest 17/12Z ECMWF has trended stronger with the low, and hence more bullish on QPF from Carteret through the northeastern zones, so winter storm warning criteria snowfall still in play.

With the strengthening coastal storm will come strong winds for the eastern coast tonight. Issued Wind Advisory for the Outer Banks tonight into early Thursday morning with northerly winds increasing to 25 to 35 mph with gusts to 45 mph.

Short Term

6 am Thursday morning through Friday As of 155 PM Wed, Cold and dry conditions will follow the offshore low pressure system Thursday, with high temps only topping out in the upper 30s to around 40 deg across the area. Most locations will rise above freezing between 10am and noon. Area roadways will likely remain dangerous until temps rise above freezing and melting begins. Low temps will cold again Friday morning, low to mid 20s inland and upper 20s/30 along the coast. As the cold upper trough moves away on Friday, high temperatures will moderate to 50 to 55.

Long Term

Friday night through Wednesday As of 155 PM Wednesday, Saturday and Sunday, High pressure moving off the coast, and rising heights will allow temperatures to warm above average over the weekend, with dry weather expected. Highs Sat in the 50s then warming into the mid 50s to low 60s Sunday.

Monday and Monday night, A cold front will approach late Monday bringing a threat of showers to area by evening. More widespread showers are expected Monday night as the front crosses the area. Increased pops to high chance. Mild temperatures will continue ahead of the front with highs in the lower to middle 60s expected.

Tuesday and Wednesday, Dry and slightly cooler conditions will be forecast for Tuesday and Wednesday as the models indicate high pressure over the area. Some lingering precip will be possible early Tuesday with a slower frontal passage, but should be drying out Tue. Highs are forecast in the mid 50s to around 60 degrees Tue and 50s for Wed.

Aviation

04z Thursday through Monday Through Thursday As of 7 PM Wednesday, A winter storm will push across rtes overnight bringing periods of snow with reduced cigs/vsbys at the terminals. A mix of MVFR and IFR cigs across rtes early this evening and expect pred IFR late this evening and early morning with greatest coverage of precip. The system will push off shore late tonight with VFR conditions returning and persisting through Thursday. Gusty north winds around 20-25 kt until early morning becoming NW then W late tonight and Thursday with gusts to around 15 kt.

Thursday night through Monday As of 155 PM Wed, Pred VFR conditions expected through the period with dry high pressure over the area.

Marine

Through Thursday As of 830 PM Wednesday, Dangerous winds and seas developing tonight. Gale Warnings remain in effect for all the coastal waters and Pamlico Sound, with SCA for the Albemarle, Alligator and inland rivers.

Latest obs show N/NE winds increasing, now 20-30 kt with gusts to 40 kt north of Lookout and 20-25 kt with gusts to 30 kt south. Seas have built to 7-9 ft north of Ocracoke and 5-7 ft south. A cold front will move through the waters late this afternoon and early evening, with northerly winds increasing quickly along with building seas. Northerly winds peak at 25-35 kt with gusts up to 40-45 kt and seas 7-11 ft late tonight and early Thursday as low pressure develops off of the coast. Winds and seas will slowly diminish through the day Thu. Nw winds become 15-25 kt with seas subsiding to 4-7 ft late.

Thursday night through Monday As of 155 PM Wed, Winds become more westerly Thu night and will continue to slowly diminish along with seas. Seas expected to subside below 6 ft after midnight across the central waters. Friday and Saturday W/SW flow 10-15 kt is expected with seas 3-5 ft Friday and 2 to 4 ft Saturday. Light winds and seas expected Sunday into early Monday, generally 10 kt or less with seas 1-3 ft. Could see increasing southerly winds and building seas Monday ahead of the approaching cold front.

Watches, Warnings, Advisories

Nc, winter weather advisory until 2 am EST Thursday for ncz029-044- 079-090>092-098. Winter storm warning until 6 am EST Thursday for ncz045>047- 080-081-093>095-103-104. Coastal flood advisory until 10 am EST Thursday for ncz103-104. Wind advisory until 8 am EST Thursday for ncz103-104. Marine, small craft advisory until 10 am EST Thursday for amz130-131- 136-137. Gale warning until 10 am EST Thursday for amz135-150-152-154. Gale warning until 8 am EST Thursday for amz156-158.

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