519 FXUS62 KILM 062321 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 621 PM EST Sat Jan 6 2018 .SYNOPSIS... Arctic high pressure over Illinois will build into the Carolinas Sunday. The frigid air of Arctic origin, will move offshore Monday, with temperatures rebounding up to normal levels. A weak cold front will move through Monday night, with high pressure building down behind it through mid week. Rain chances will increase late Thursday and Friday, as a warm front lifts north, followed by a cold front into next weekend. && .NEAR TERM /THROUGH SUNDAY/... As of 621 PM Saturday...GOES-E simple water vapor RGB channel illustrates nicely the frigid cold pool/trough, dippings its wintry toes into the heart of the Gulf coast states presently, with progress of the upper trough being made to the S and the E. Areas of snow-pack coupled with clear sky and current readings in the 20s at 6 pm, will bring a deep cold overnight of single digits and teens. No noteworthy changes to the frigid forecast. With minimum air temperatures like these, not a great deal of wind will be needed to reach wind chill advisory criteria, and this product remains posted for early Sunday. As of 300 PM Saturday...This extraordinary cold wave is breaking water pipes and breaking climate records stretching back 100 years. Lake Waccamaw is freezing over, along with our tidal creeks and salt marshes. Tundra Swans were spotted a few days ago in the Cape Fear River behind Carolina Beach, and local populations of pelicans and egrets are experiencing high winter mortality. We're approaching the end of our famed Southern Hospitality for this visiting arctic airmass and can't wait to see it leave the area on Monday. Until then, another extremely cold night is in store for the eastern Carolinas. The center of the arctic high will move from Indiana into Virginia by daybreak Sunday. Excellent radiational cooling over a few inches of persistent snowpack should allow temperatures to fall to 6 to 12 degrees tonight. It wouldn't surprise me if a few of our normally cold spots in Robeson or Pender counties approached zero. Areas of devoid of significant snow cover from Elizabethtown and Whiteville south into the Myrtle Beach/Pawley's Island area should run several degrees warmer with 12-17 degrees forecast for this stripe. My forecast for Wilmington of 9 degrees, should it verify, would be the coldest reading since the Christmas snowstorm of 1989 over 28 years ago. Aside from a few cirrus streaming in during the afternoon, sunny skies again on Sunday will only have limited success melting the snow as temperatures struggle into the 32-37 range. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...One last cold night forecast for Sunday night as this seemingly never-ending arctic blast finally retreats. Surface high pressure will be centered across the eastern Carolinas early Sunday night before slowly lifting eastward into Monday morning. This may be forecasted to occur too quickly, as the E NC snow pack (how weird is that to write) reinforces the cold high pressure and likely causes it to linger longer than guidance suggests. This will create a very weak gradient and strong radiational cooling will begin after dark. However, WAA just above the surface, which is actually beneficial to radiational cooling, will causing increasing moisture trapped within the near-surface inversion, and stratus may develop overnight. Even if cloud cover is delayed, increasing moisture within this layer will inhibit ideal cooling in a "dirty IR window" type setup. Additionally, increasing cirrus is expected from west to east, so although mins will be cold, they will be warmer than the past several nights. Expect lows falling into the upper teens across NC and inland SC, just above 20 elsewhere. Monday is a tricky forecast as the guidance suggests highs rising to near normal for the first time in 2018. However, the trend in MOS has been notably colder the last few days, and the with the guidance likely too fast in developing return flow as the high shifts offshore, cool north winds and increasing stratus will keep highs cool once again Monday, although our string of days without reaching 40 will come to an end with highs in the mid to upper 40s forecast. A cold front will drop into the area Monday night driven by a weak vorticity streamer moving through the mean trough. However, cold advection is weak and lagging with this feature, so temperatures into Tuesday morning are forecast to be near seasonable norms as cloud cover and wind inhibit much cooling. GFS profiles and time heights show enough moisture in the lower half of the column to produce some light showers with this feature, however the NAM/ECM and WPC suggest a dry FROPA. Inherited forecast is SCHC for late Monday night, and will leave this unchanged as it is D3, but expect most of the area will stay dry Monday night. if any light rain does fall will be of the liquid variety, no mixed ptype issues this time around. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 300 PM Saturday...High pressure will build down behind a weak cold front on Tues while a ridge tries to nose up into the Southeast over the top of a cutoff low over the Gulf. A very shallow moist layer and a steep inversion early Tues may keep some low clouds to start the day, but as warming and mixing occurs, should see increasing sunshine and warming on Tues into Wed. Temps should reach well into the 50s Tues and into the 60s by Wed. There will be westerly downslope flow aloft through mid week and the h5 heights and 850 temps will continue to rise through the week. Therefore expect a warming trend as the 850 temps reach up to 6c by Tues aftn. High pressure will shift off shore and a warm front will lift north Thursday. May see some enhanced lift as cutoff to the south gets caught up in deep southerly flow on front end of digging mid to upper level trough later in the day on Thurs. Therefore expect increased clouds and chc of rain on Thurs. Once this warm front moves north of the local area by late Thurs, we will see an increasing southerly return flow into Fri. The 850 temps will reach up to 10c Thurs and with continued WAA through Fri, they will increase up above 12c. This should bring temps a good 15 degrees above normal, into the 70s, by Fri aftn, especially if we get enough sunshine. The digging mid to upper trough will push a cold front east late Fri into Sat with increasing chc of pcp once again. Expect the best chc to come Fri night into Sat. Should be interesting to see if we get areas of sea fog Thurs and Fri as warm and moist air flows over the cool waters. Overall expect drier weather Tues through early Thurs and wetter weather late Thurs into the first part of the weekend with warming temps through the week. && .AVIATION /23Z SATURDAY THROUGH THURSDAY/... As of 00Z...Arctic high pressure will settle over the region through the valid TAF period. Winds will diminish overnight, going calm at times with near record cold temperatures. Sunday, scattered cirrus with a predominately northerly wind, mainly less than 10 kts. Extended Outlook...MVFR/SHRA Monday through Tue morning, Otherwise VFR. && .MARINE... NEAR TERM /THROUGH SUNDAY/... As of 621 PM Saturday...Seas 2-4 ft, in mixed wave periods from the ENE, accompanied by a moderate NNW chop prevails, and this regime should hold overnight, possibly up to 5 feet near Frying Pan Shoals overnight. A SCEC is not out of the question later if winds clock in stronger than model guidance is laying forth. As of 300 PM Saturday...Arctic high pressure over Indiana this afternoon will slide southeastward into Virginia by daybreak Sunday. Very cold air continuing to pour into the region from the north will create wind chills from 5-15 degrees across the coastal waters late tonight and into Sunday morning. Northerly winds of 15-20 knots will continue into Sunday morning while veering a little more northeasterly, then diminishing to 10-15 kt Sunday afternoon. Seas currently 2-4 feet could build toward 5 feet at 20 miles' distance from shore overnight into Sunday morning. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...High pressure centered near the Outer Banks will drift slowly eastward this period while maintaining a ridge back into the Carolinas. This leaves a weak gradient across the waters with NE winds Sunday night and Monday around 5-10 kts, veering slowly to become Southerly late Monday night. At the very end of the period, a weak cold front will push offshore turning winds to the NW at still light speeds by Tuesday morning. A general 10-sec SE swell will exist in the wave spectrum through early next week, and with the light winds will noticeable to mariners. Otherwise expect a 1-2 ft NE wind wave becoming S late, and significant seas will be around 2 ft. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 300 PM Saturday...High pressure will build down behind weak cold front through Tues with light northerly flow. This will maintain lower seas of 3 ft or less. High pressure will shift farther off shore Wed into Thurs and winds will veer around becoming more on shore and eventually southerly as a warm front lifts north late Thursday into early Fri. The winds will gradually increase late Thurs as gradient begins to tighten ahead of next cold front approaching the Carolinas from the west. Expect winds to increase up to 10 to 15 kts out of the south by Thurs night. This on shore, then southerly flow will push seas up to 3 to 5 ft by late Thurs and possible into SCA thresholds by end of the period, heading into Fri morning. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Wind Chill Advisory from 4 AM to 10 AM EST Sunday for SCZ017- 023-024-032-033-039-054>056-058-059. NC...Wind Chill Advisory from 4 AM to 10 AM EST Sunday for NCZ087- 096-099-105>110. MARINE...None. && $$ NEAR TERM...TRA/MJC SHORT TERM...JDW LONG TERM...RGZ AVIATION...43