Area Forecast Discussion
Issued by NWS Wilmington, NC

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520 FXUS62 KILM 151507 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1107 AM EDT Sun Oct 15 2017 .SYNOPSIS... High pressure will shift offshore this afternoon. A strong cold front will quickly cross the Carolinas on Monday accompanied by showers. Much cooler and drier air will build in Monday night and Tuesday as Canadian high pressure builds over the eastern United States. Dry weather with seasonable temperatures should persist through Saturday. && .NEAR TERM /THROUGH TONIGHT/... As of 1110 AM Sunday...The fog mainly west of Kingstree to Lumberton line continues to slowly dissipate and visibilities are now above 1 mile thus the dense fog advisory was cancelled. Previous Discussion...this morning dense fog has set in mainly west of a line from Kingstree, SC to to Lumberton. The GOES-16 red visible channel is showing thin spots over portions of Florence, Marion, Darlington county starting to form so the start of the dissipation of the dense fog is beginning. To the east of the dense fog is a 1200 ft to 2000 ft stratus deck. The statistical guidance is showing all the cloud cover thinning by 17 utc. Only change to forecast was to cut maximum temperatures by 1 to 2 degrees. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 AM Sunday...The upper air pattern is looking less like summer and a lot more like fall. A progressive full-latitude trough will move across the eastern United States on Monday. Just like we saw with yesterday morning`s model runs, the new 00Z GFS is faster than the NAM with timing of the actual frontal passage. Even averaging the 4-hour timing differences together, I still like the warmer NAM forecast highs better as there should be some insolation during the morning ahead of the front where the airmass should remain quite warm. A decaying low and mid level ridge out ahead of the trough will prevent any significant return of moisture along the cold front, probably leaving only a narrow channel of moisture deep enough to produce showers. Good low-level convergence plus meager convective instability should yield a line of showers on and just behind the surface front. Reviewing model isentropic fields for Monday afternoon and night shows no significant upglide within the frontal inversion. Despite a good 6 hours of post-frontal cloudiness there probably won`t be a significant amount of post-frontal precipitation. Our forecast PoPs are 60-70 percent, but with only around a tenth of an inch of QPF. The chilliest air of the season will surge into the area Monday night. 850 mb temps will fall to +8C to +10C, significantly cooler than what we`ve seen all this month. Breezy low-level winds should keep temperatures from dropping too far, and we`re forecasting lows in the upper 40s with 50/low 50s on the beaches. Even with lots of sun on Tuesday highs should only reach 68-70. Better radiational cooling with lighter winds Tuesday night should allow temps to fall into the mid 40s inland with upper 40s near the coast. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 330 PM Saturday...With a recently passed cold front, high pressure will quickly build in across the area early next week where it will remain through the period. A brief cool down on Tuesday will be short-lived as upper level ridging moves in across the eastern US in to the latter part of the week. High temperatures on Tuesday will be in the upper 60`s inland to around 70 at the coast, with a gradual increase into the mid 70`s throughout the week. Overnight lows will range in the low to mid 50`s. In regards to precipitation, moisture supply to the area will remain extremely minimal given placement of the ridge. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... As of 12Z...Surface observations indicate some fairly dense fog inland with mainly MVFR conditions along the coast. Look for VFR conditions at most locations by 15Z. High pressure will shift offshore this afternoon with weak southwest flow expected, possibly a southeast sea breeze. Tonight, dense fog will likely return with moist southwest flow. A cold front will approach the region from the west at the end of the forecast period. Extended Outlook...Isolated to scattered MVFR/IFR produced convection is possible on Monday ahead of a strong cold front. MVFR stratus possible near the coast TUE/WED morning in blustery post-frontal NE wind. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 955 AM Sunday...north to northeast winds of 5 to 10 knots over the waters with a 3 foot, 9 second swell from the east. As the high shifts east today and a cold front approaches the waters on Monday the wind tonight will become southwest. Seas are expected to remain in the 2 to 4 ft range through the period. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 AM Sunday...The strongest cold front of fall will push across the coastal waters around noon on Monday. Light westerly winds Monday morning will turn northerly and increase to 20-25 kt with gusts over 30 kt by late afternoon. Cold air will continue to surge across the area Monday night with some gusts potentially reaching 35 knots due to deep mixing triggered by cold air moving across warm water. Wind speeds should diminish slightly on Tuesday, but Small Craft Advisory conditions will probably persist through the day as the incoming Canadian high remains too far north of our area to allow the pressure gradient to loosen. LONG TERM /WEDNESDAY THROUGH THURSDAY/... As of 330 PM Saturday...Wednesday and Thursday, expect northeasterly winds around 15 kts with seas 3 to 5 ft. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory from 5 PM Monday to 6 PM EDT Tuesday for AMZ250-252-254-256. && $$ NEAR TERM...DRH SHORT TERM...TRA LONG TERM...SGL AVIATION...DL is the U.S. government's official web portal to all federal, state and local government web resources and services.