Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 271113 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 713 AM EDT Thu Jul 27 2017 .SYNOPSIS... Isolated showers and thunderstorms Thursday will become more numerous Friday into Saturday ahead of an unseasonably strong cold front. Some of these storms could reach strong to severe levels Fri aftn thru early Sat. Drier and cooler air, relatively speaking, is expected to push across the area in the wake of the cold frontal passage late Sat and continue thru early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM Thursday...The local area will remain in subsidence and dry air through today although the NE to E flow will come back around to the SE to S by this afternoon. Temperatures were down near 70 early this morning in a drier and relatively cooler air mass, but there will be a gradual moisture return bringing dewpoint temps up a few degrees tonight. Shallow moisture provided some patchy fog and low stratus in places, but this will dissipate allowing for plenty of sunshine through the day today. The developing southerly winds may bring some of the moisture from convection associated with lingering front/low over Fl/GA this afternoon. Have included a slight chc of shwrs/tstms over the Georgetown area to account for this slight moisture return. Overall expect temps to return into the mid to upper 80s after a below normal start to the day. Mid to upper ridge extending in from the west will get squeezed out as trough digs down from the north late today through tonight and weakening low to the south moves off to the north to northeast. This lingering low pressure to the south will weaken and move north to northeast through early Fri. This should produce some shwrs/tstms over the waters by Fri morning and some of these showers will affect the coast. Convection associated with shortwaves rotating around mid to upper trough should remain northwest of area through today but will include increasing chc of convection reaching into the area by Fri morning. Pcp water values as low as 1.2 inches today will increase up near 1.6 inches by Fri morning but just to the south and north values will be up to near 2 inches. The moisture return will bring temps back up into the mid 70s for low temps tonight. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 400 AM Thursday...An active wx period will highlight this time period. Already under the influence of an upper trof at the start of this period, it`s amplification is progged to increase as a vigorous mid-level s/w trof dropping southeast from the Great Lakes, reaches the Mid-atlantic states early Sat. Models amazingly even agree in taking this open s/w and closing it off over the Mid-Atlantic states thru Sun morning. All of this activity aloft is quite unusual for this time of the year when the area is usually under the influence of Bermuda High pressure sfc and aloft with subtle flow aloft. At the sfc, Friday will see convection fire up along a pre-frontal trof across the central Carolinas and push to the ILM CWA during the aftn and evening. By Friday night, will see sfc low really start to take shape and in association of the vigorous mid-level s/w trof dropping toward the Mid-atlantic states. This 1010mb low initially will strengthen to at or below 1000mb by Sat morning over the DELMARVA area. It`s associated cold front will be pushing southeast across the FA Sat aftn and clearing the ILM CWA Coast during Sat evening. Convection ahead and along the cold front Fri evening thru Sat will have plenty of dynamics to work with that will result in strong to severe thunderstorms likely. SPC already has a Slight Risk across the FA. As for temps, maintained a blend of model guidance thru the period. Looking at a decreasing trend to both highs and lows from Friday thru Sunday morning. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...Primary weather features this period include an unseasonably amplified upper trough, followed by Canadian high pressure which may bring a brief feel of very early Fall, as dewpoints dip below normal for the season. A surface trough inland Saturday will move offshore Saturday night, as relatively strong high pressure from Canada barges in from the NW in earnest early Sunday. The high will drop dewpoints deep into the 60s Sunday, removing the muggy edge well into the next week, as the high remains anchored over the mid- ATLC region. The best rain chances are Saturday, before mid-level drying and lowering dewpoints inhibit convection. NE flow in the low-levels may bring in bouts of oceanic cu and, in conjunction with the Canadian high, will keep maximum temperatures below normal from Sunday onward. This accompanied by small rain chances, mainly by the coast. It`s possible a few storms early Saturday could be capable of strong gusts. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... As of 12Z...Mainly VFR conditions during this 24 hr stretch. Only exception will be possible MVFR conditions from BR during the 08z-12z time frame Fri morning. Upper level cloudiness will push across the FA thruout this period. There is a mid-level cloud deck from EDE to CLT that is making some progress southeastward. Will include short term bkn deck in the 6.0k to 7.0k foot height in the FLO and LBT TAFS but hold off with the coastal terminals. This deck likely to scour out by the time it reaches these terminals. Diurnal Cu will sprout up in the 2.5k to 4.5k foot level later this morning and aftn however will keep it FEW/SCT. Light NE-E winds around 5 kt will start the day. The center of the sfc high will push off the NC Coast this aftn. The sfc pressure pattern becomes conducive for southerly winds 5 to 10 kt except SE-SSE around 10 kt for the coastal terminals. Depending how much heating will determine the strength of the sea breeze and the possibility of stronger aftn/early evening winds for the coastal terms. Winds all site veer to SW and drop to less than 5 kt by late this evening and overnight. Extended Outlook...MVFR/IFR flight restrictions are likely in association with thunderstorms later Fri thru early Sat. Some of the storms may be strong to severe. Mainly VFR expected Sunday thru Monday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 AM Thursday...Winds will remain 10 kts or less through today as they shift from NE-E around to the SE to S as high pressure extending across the waters from the north shifts further off shore. The sea breeze will give a little spike to the winds this afternoon. Seas will remain fairly benign with heights less than 3 ft. A small SE swell around 9 seconds will mix in. Winds will veer slightly more by Fri morning as Bermuda High begins to dominate. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 400 AM Thursday...Deteriorating wind and sea conditions expected thru this period. Ahead of the pre-frontal trof, SW winds will increase to 15 to 20 kt during Friday and maintain these speeds into Friday night with gusts to 25 kt being added to the mix. For Sat, the sfc pg will tighten even more as low pressure deepens over the Delmarva and Mid-atlantic states. The sfc cold front dropping southeastward, will be on the doorsteps by Sat morning. Models take the cold front across the local waters late in the day Sat or Sat evening. Expect active SW to WSW winds ahead of the cold front that will likely breach SCA thresholds until the CFP, Sat evening. After FROPA, winds will veer to the N-NE around 15 kt. Significant seas will undoubtedly be dominated by wind driven waves at 5 second periods on Fri, and around 6 second periods during Sat. Seas will build to 3 to 5 ft during fri and reach 4 to 7 ft by and during Saturday. The 7 footers primarily the waters from off Cape Fear to Little River Inlet. This a result of a longer fetch due to the strong WSW-W wind directions during Sat. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...A significant wind-shift will occur Saturday from WSW to NNE, as a strong cold front for late July crosses the coast Saturday afternoon or evening. It is possible a Caution headline or even an Advisory may be needed for gusty winds ahead of and just behind the front. In addition...TSTMS and showers will be more numerous Saturday and a few storms may be strong to severe. NE winds 15 KT Sunday will begin to veer Monday to E-SE, with seas of 2-4 feet, highest offshore. Sunday seas a bit messy, as residual SSW waves every 6 seconds mix with a NE chop and weak SE swell waves. Isolated showers will dot the waters Sunday and Monday but of light intensity. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...DCH NEAR TERM...RGZ SHORT TERM...DCH LONG TERM...MJC AVIATION...DCH

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