textproduct: Newport/Morehead City

WHAT HAS CHANGED

Confidence continues to increase for a low off the Southeast Coast to develop later this week/weekend, however exact impacts to Eastern NC remain uncertain.

KEY MESSAGES

1) An anomalously cold airmass will remain over the Eastern CONUS and will result in below normal highs and lows through the week. Bitter wind chills are expected each morning with Saturday night/Sunday morning currently forecast to be the coldest period (0-10 degree wind chills).

2) A deep trough will dig across the ECONUS this weekend with a low forming off the Southeast coast, potentially bringing several hazards to ENC including wintry weather.

DISCUSSION

KEY MESSAGE 1... No real changes in forecast thinking as an Arctic high pressure system continues to extend into the Carolinas and will move little over the next few days. With a reinforcing dry cold front progged to move through the Carolinas Wed night into Thursday keeping things on the cold side. This is forecast to continue to bring below normal temps to ENC into this weekend with highs ranging from 30-45 degrees and lows around 15-30 degrees. Late night/early morning wind chills will be in the 10s to low 20s through the week. The coldest period in the forecast is currently Saturday night/Sunday morning with 0-10 degree wind chills.

KEY MESSAGE 2... Deep positively tilted upper level trough will dig across the Plains later this week and move into the Eastern Seaboard this weekend as it takes on a more neutral to negative tilt. At the same time we will be monitoring two mid level shortwaves, the first will be a southern stream shortwave that will traverse from the Pacific Northwest Wednesday to the Gulf Coast States late this week. At the same time a second northern stream shortwave will dive south from Hudson Bay Canada on Wednesday and into the Southeastern CONUS this weekend. This is forecast to result in surface cyclogenesis off the Southeast coast sometime Fri or Saturday with this low then tracking north and east while deepening, potentially rapidly as the weekend progresses.

There are quite a few forecast challenges with this setup leading to continued low confidence in the forecast for this weekend. The first will be the exact timing and strength of each mid level shortwave and if and where they phase together over the weekend. If they were to phase together a stronger and more rapidly deepening low would develop. However, if these mid level shortwaves don't phase or phases well offshore, a weaker surface low and lower rate of intensification would occur near the Southeast Coast. In addition to this, uncertainty remains in when the aforementioned trough begins to take on a more neutral or negative tilt which will impact when surface cyclogenesis occurs and the eventual track of whatever low does develop.

All of the above will greatly dictate how the forecast trends for this weekend, but confidence is gradually increasing that ENC will see marine, coastal, and potentially winter impacts this weekend. The WPC Winter Storm Severity Index now shows a 60-70% chance of moderate impacts across ENC this weekend. This is a slight increase from 50-60% about 12 hours ago. HOW impactful this system will be will become clearer with future updates, so users should be leery of any snow maps this far out.

PoPs will increase Friday night, peak on Saturday, and clear out on Sunday. For now, it looks like snow is the most likely P-type for the coastal plain with the coast being the transition zone and more likely to see mixed precip. This is subject to change as we are still several days out, and it's much too soon to nail down any amounts.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

VFR conditions and clear skies are expected to continue through tomorrow as dry and cold high pressure persists over the region. Another dry boundary will move through tonight with wind gusts coming up to 15-25 kts, but mostly along the coast and east of the TAF sites.

Outlook: VFR conditions will likely continue through Friday as cold high pressure remains in place. This weekend an extended period of sub-VFR conditions is likely as a coastal low develops and brings wintry precipitation to some if not all of Eastern NC.

MARINE

Latest obs across ENC show widespread SW'rly winds at about 10-15 kts with gusts up to 20 kts and 2-4 ft seas as high pressure wedges in from the south and west. This will be short- lived, however, as another round of marginal SCA winds is forecast to develop across the coastal waters and Pamlico Sound tonight through early Wednesday as a weak mid level shortwave traverses through the area. Generally expect W to WNW winds at 15-20 kts with gusts up around 25 to 30 kts across the waters with small craft advisories tonight, with 10 to 15 kt winds with gusts up to 20 kts elsewhere. Given the brief period of elevated winds seas will likely only build to 3-5 to 4-6 ft tonight. By Wednesday morning winds will quickly decrease down to 10-15 kts and veer to the NW across all waters thus ending all SCA's. A dry cold front will then transit across our waters Wed evening potentially bringing yet another round of brief SCA conditions to our waters overnight Wed.

Outlook: Additional rounds of SCA conditions are expected Thursday and Friday night with Gales and potentially storm force winds developing Saturday and lasting through the weekend.

MHX WATCHES/WARNINGS/ADVISORIES

NC...None. MARINE...Small Craft Advisory from 7 PM this evening to 4 AM EST Wednesday for AMZ135. Small Craft Advisory until 7 AM EST Wednesday for AMZ150-152- 154. Small Craft Advisory from 7 PM this evening to 7 AM EST Wednesday for AMZ156-158.