Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 200542 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1242 AM EST Mon Nov 20 2017 .SYNOPSIS... High pressure will control area weather through Monday. A coastal trough and approaching cold front may bring some showers late Tuesday and Tuesday night. Low pressure is expected to develop in the eastern Gulf of Mexico mid week and may bring unsettled weather to the eastern Carolinas Thursday and Friday as it moves northeast. High pressure early next weekend will be followed by the passage of a cold front next Sunday. && .NEAR TERM /THROUGH TONIGHT/... As of 8 PM Sunday...Have added Columbus County to the Frost Advisory although this is expected to be a marginal event due to very dry air over the forecast area. Patchy Frost is a good bet here and there overnight, but widespread frost may be tough to get given dry low levels. Previous discussion from this afternoon follows: Surface high pressure will build in under a northwest flow aloft. The airmass is once again just cold enough to cause some frost/freeze concerns as a good part of our area remains at least officially in the growing season. It appears via guidance and some residual low level mixing that any freeze conditions will be a stretch. There is enough of a threat/concern for frost especially late when the winds diminish. Will go ahead and issue a frost advisory for areas where mins are 35 degrees and under. This will preclude most of the coastal areas. Overnight lows will general be in the middle 30s. Highs Monday will be middle to upper 50s under mostly sunny skies. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...High pressure previously overhead takes on a very west-east elongation Monday night bringing a light onshore flow to coastal areas, especially SC. The ocean influence paired with the radiational cooling inhibition could add a few degrees to the seasonably cool nighttime lows. Neither should hold true over NW zones and there may be a large than normal NW to SE gradient in low temps, those areas ending up almost as cool as the previous night. On Tuesday warm advection will both shoot highs back to climatology if not a few degrees warmer but also yield increasing cloud cover and some slowly increasing rain chances. These rain chances appear to increase and shift from inland to the coast Tuesday night as the WAA interacts with stronger vorticity centers in the SW mid level flow. The WAA and cloud cover will keep Tuesday night lows elevated a good 10 degrees above climatology. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 300 PM Saturday...Lingering rain is possible early Wednesday as an upper trough moves out and a cold front moves out to sea. Another short wave trough could spawn low pressure development along the old front off the southeast U.S. coast. This will bring another chance of rain to the area Wednesday night into Friday, though the exact details of this scenario are still in doubt. Dry weather is expected for the remainder of the long term but light showers are possible with another frontal passage and vigorous upper trough on Sunday. Temperatures will be near seasonal normals of mid 60s Wed before falling back into the mid to upper 50s for Thu and Fri. Slightly warmer temperatures are expected Sat and Sun with highs in lower 60s. Mins temperatures Wednesday night will fall to the upper 30s to lower 40s with higher numbers SE and along the immediate coast. Temperatures in the mid 30s to around 40 are expected Thu night and Friday night before rebounding to the mid to upper 40s Saturday night. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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As of 06Z...High confidence in VFR through the valid period. High pressure will shift eastward today, moving atop the terminals this aftn and then offshore tonight. This occurs in conjunction with W/NW flow aloft creating nearly cloudless sky conditions and northerly winds of 10 kts or through the aftn. As the high shifts offshore winds will begin to shift to the east in response to a developing coastal trough, but at still light speeds. No low level clouds are expected within this valid period, but mid-level flow becoming SW will drive increasing cirrus level moisture and a BKN cirrus cig is forecast Monday night, but VFR will persist. Extended Outlook...MVFR conditions may develop in low clouds and light rain Tuesday through Wednesday morning, then MVFR to IFR conditions are possible Thursday night into Friday in low clouds, rain, and fog.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 8 PM Sunday...Have dropped Exercise Caution headlines for our southern 3 marine zones as conditions continue to improve. For AMZ250 we are just barely within criteria with 15 to 20 kt winds and 3 to 5 ft seas, but expect this too will improve by around midnight. Previous discussion from this afternoon follows: Winds and seas on the way down this afternoon as although cold air advection continues, the stronger low level wind fields were ahead of the front that has long since passed. North to northwest winds of 15-20 knots will prevail most of the late afternoon hours and night. On Monday surface high pressure settles over the area and winds decrease dramatically, down to the single digits by late afternoon. Seas are down to just over six feet at 41013 and I will wait til the last minute but most likely cancel the small craft advisory just a touch early and issue an exercise caution statement. Overall seas will settle into a 2-4 foot range overnight and even less later tomorrow. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...Things just about as quiet as they get for the marine environment for most of the period. West-east elongated high pressure to keep just a light onshore flow of just a few knots. A weak coastal trough will develop on the periphery of the high later Tuesday into Tuesday night veering flow to SE and adding a few knots of wind speed, bumping the forecast up a category or more. Seas will be following suit, showing a gradual growing trend. LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 300 PM Saturday...N to NE winds INVOF 15 KT are expected through much of the period though a peak of 15 to 20 KT is possible Thu night into Friday. On the open waters, seas of 3 to 5 feet are expected through the period. Depending on low pressure development off the SE U.S. coast, conditions in this period could be hazardous and it is possible that winds and seas could exceed thresholds for Small Craft Advisories, 25 KT winds and/or seas of 6 FT, during this period. && .ILM WATCHES/WARNINGS/ADVISORIES...
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SC...Frost Advisory from 4 AM to 9 AM EST this morning for SCZ017- 023-024-032-033-039-053. NC...Frost Advisory from 4 AM to 9 AM EST this morning for NCZ099. MARINE...None.
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&& $$ SYNOPSIS...99 NEAR TERM...REK/JDW SHORT TERM...MBB LONG TERM...RAN AVIATION...JDW MARINE...REK/MBB/SHK/RAN is the U.S. government's official web portal to all federal, state and local government web resources and services.