Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 140555 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1254 AM EST Thu Dec 14 2017 .SYNOPSIS... Temperatures will return to normal Thursday and Friday as a pool of cold air aloft moves away to the northeast. Another cold front will reinforce dry and cool weather this weekend. Low pressure approaching from the Gulf will bring an increasing chance of rain, and a warming trend through early next week. && .NEAR TERM /THROUGH THURSDAY/... As of 8 PM Wednesday...Temperatures appear to have stabilized and are even rising a bit over our western counties as warm advection in advance of the next front takes hold. Dewpoints are making an even more robust recovery and are now in the 20s and lower 30s. This is all according to plan and have not needed to make any major changes to the forecast. Previous discussion from this afternoon follows: Single digit dew point values are certainly a rarity in this part of the world, but the `Carolina Desert` appears to be in place today with widespread dewpoints of 8-12F and RH below 30 percent. This certainly is an indicator of the dryness of the airmass, echoed further by examination of the WV imagery, and RAP soundings depicting PWATs around 0.25 inches. Temps have rebounded better than forecast, approaching 50 in many spots thanks to full sunshine, but temps will drop quickly after sunset thanks to good radiational cooling in the dry column. However, the temp and wind forecast tonight is less than clear-cut. Warm advection will begin in earnest this evening as high pressure ridges northeast from the Gulf Coast, and a clipper-type low pressure moves through the Great Lakes creating a brief warm sector across the Carolinas. While this regime will be short lived, it will be quite strong, with 850mb winds forecast to exceed 40 kts, driving surface winds through the overnight. Still expect a surface inversion to develop, especially early, which will at least limit gust potential overnight, but do forecast an increase in winds after midnight and towards Thursday morning, with speeds of 10-15 mph likely. If the inversion doesn`t materialize, it could be a very windy night, but at this time think there will be enough of a lag in the LLJ development after sunset to permit an inversion first. As winds pick up, temps will likely level off or increase the latter half of the night, so mins in the low to mid 30s are expected early. On Thursday, the aforementioned clipper will swing across the Mid- Atlantic and drive a weak cold front into the Carolinas. Ahead of this feature, temps will climb to seasonable norms in the upper 50s to around 60, with continued nearly cloudless sky conditions in deep westerly flow. The surface front, which has little to no temp gradient across it, will swing across the region late in the period with a wind shift to the NW at the surface but little other fanfare. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 330 PM Wednesday...The deep east coast trough that has been in place for some time now will relax a bit during the short term period but not abate completely. A very broad trough will develop out west and sink down into the area by Saturday morning with an essentially dry frontal zone at the surface. After a brief period of weak warm air advection Friday 850mb temperatures will dip once again to near freezing or below by Saturday morning. This will lead to surface temperatures at or near freezing for most of the area for lows. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 330 PM Wednesday...The primary caption for the extended period, `Seasonably Cool and Dry This Weekend, Milder and Wetter early Next Week`. In wake of a dry cold frontal passage late Friday, a mainly fair and seasonably cool weekend appears to be shaping up, before the onset of a warming trend into early next week, as ridging aloft ensues. GFS and ECMWF differ on timing and strength of ejected Baja short-wave Sunday, but both agree on a milder and wetter pattern after the weekend. The first chance of rain by Sunday night, as this features ejects offshore early Monday. Despite ECMWF/GFS differences even into Tuesday, it seems we can infer a mild pattern prevailing and rain chances ahead of an upper trough, that in both models appears along the east coast next Wednesday. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 06z...A stiff southwest wind will continue overnight into Thursday. Have included some gusts in coastal terminals and tempo gusts inland. Although dewpoint temps have been increasing overnight, air mass remains dry overall. Only some passing mid to high clouds expected through the period with VFR conditions. Winds will veer to the west through today and further to the north tonight as another system passes by to the north and high pressure builds in from the north behind it. Extended Outlook...VFR. Possible MVFR Sun night into Monday associated with low pressure system moving across the Southeast. && .MARINE... NEAR TERM /THROUGH THURSDAY/... As of 8 PM Wednesday...Advisory conditions have not yet developed but winds are now increasing from the SW at 10 to 15 kts and seas are up around 2 to 3 ft. Still expect conditions to deteriorate overnight as SW winds increase in advance of the next front. No major changes with the latest update. Previous discussion from this afternoon follows: Westerly winds across the waters will transition to SW this evening as WAA begins ahead of a cold front dropping across the Great Lakes. This will drive increasingly strong SW winds, reaching up to 40 kts aloft, which will manifest at the surface as 20-30 kt winds this evening into Thursday, even with the cold ocean temperatures. For this reason the ongoing SCA remains unchanged into Thursday morning for these winds driving seas up to 4- 7 ft. The weak front will cross offshore during Thursday bringing a wind shift to the NW and speeds dropping to 10-15 kts, which combined with the offshore component help drop seas to 2-4 ft. SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 330 PM Wednesday...Somewhat light wind fields for the first part of the short term period as a weak boundary will bisect the waters. Expect northeast winds to the north of the front with west to southwest winds to the south. Later Friday afternoon a more consistent southwest flow develops with stronger magnitudes, 15-20 knots. This direction will be short lived as a northwest flow develops late Friday maintaining the 15-20 knots. Significant seas will be 2-4 feet through the period with some five footers possible later across the outer waters. LONG TERM /SATURDAY THROUGH MONDAY/... As of 330 PM Wednesday...A manageable marine period over the weekend with moderate offshore winds in wake of a dry cold frontal passage Friday night. As a result, inshore seas will have limited fetch length for growth, but notably larger seas will prevail offshore, although no advisories are expected as weak high pressure passes over then offshore on Sunday. SW-W winds expected Monday as high pressure settle offshore and SE of the waters. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until noon EST Thursday for AMZ250-252- 254-256. && $$ SYNOPSIS...99 NEAR TERM...REK/JDW SHORT TERM...SHK LONG TERM...MJC AVIATION...DL MARINE...MJC/REK/JDW/SHK is the U.S. government's official web portal to all federal, state and local government web resources and services.