Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 211750 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 150 PM EDT SAT MAY 21 2016 .SYNOPSIS... Showers and thunderstorms are possible ahead of a cold front today. An upper low will keep conditions cool with a slight chance for showers through Monday. More summer like weather develops by the middle of next week with above normal temperatures and drier conditions. && .NEAR TERM /THROUGH TONIGHT/... As of 1230 PM Saturday...the mid-level s/w trof mainly responsible for the rain this morning, has accelerated well ne of the area. in its wake, weak subsidence aloft will keep a lid on convection atleast thru the mid-afternoon hrs. Daytime insolation has broken thru to the sfc...with the ovc stratus cloudiness having transitioned into a cu field across the Carolinas. This will lead to increasing sfc based instability with Nambufr Soundings indicating 2000+ CAPE by late this aftn and into the early evening, along with DCape values increasing to 800+. SFC forcing from a cold front dropping southward will provide the necessary forcing to help initiate convection. The time frame for this to occur will be from late this afternoon thru the mid evening hours with 30-40 pops covering it. Looking over the various thunderstorm parameters, the best potential these storms produce will be for strong wind gusts and have re-hashed and highlighted the hazardous weather outlook to convey this potential. Afternoon highs should break into the 80s across most locations even along the immediate coast where westerly winds aloft will be strong enough to keep the sea breeze pinned if its able to develop. Tonights lows will depend on how much caa occurs behind the front. Leaned toward the higher low temp mos guidance. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...Upper level low pressure Sunday morning across Pennsylvania will not move east as one might expect. Instead, building 500 mb heights across the Great Lakes and southern Canada will force this low to drop southward all the way into northeastern North Carolina Monday morning. This will unfortunately bring a great deal of cold mid and upper level air southward (500 mb temps as low as -20C at ILM on the 00z GFS run) which when exposed to residual low level moisture and strong May sunshine will yield convective clouds and scattered showers. These showers are expected to be most numerous Sunday afternoon with forecast PoPs around 40 percent at ILM, 20 percent at FLO. Drier air should limit shower potential further on Monday, and by Monday night the upper level low should be far enough offshore for no impact on our weather. Temperatures will run several degrees below normal both day and night through the period. I have generally used a MOS consensus forecast which is little changed from the previous forecast. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 300 AM Saturday...Upper low moving away from the area Tue will leave a flat mid level pattern over the region for the middle of next week. Tue is a transitional day with surface high moving overhead and shifting offshore as the 5h low exits to the northeast. Temperatures will be near climo with deep west to northwest flow keeping the region dry. Guidance is hinting at weak ridging aloft trying to expand north from the Gulf or Mexico midweek, pushing temps above climo Wed through Fri. Despite the westerly flow aloft both the GFS/ECMWF show moisture from the southwest topping the weak ridge and heading east late in the week. Lack of deep moisture and weak subsidence will keep the region dry Wed but the increased moisture late in the week and potential for shortwaves emerging from the southwest does warrant a silent pop Thu/Fri. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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As of 18Z...All shwrs/tstms moved off this coast this morning leaving a fairly solid field of stratus which has broken up into stratocu around 2k-4k ft. Expect cu field to break up further this aftn, but increased sunshine will lead to increased instability and therefore potential for tstms later this aftn into this eve ahead of an approaching cold front. After midnight expect some MVFR fog with potential for stratus heading into Sunday morning as winds shift from W-NW to N as cold front comes through. Extended Outlook...Possible MVFR conditions on Monday, otherwise VFR.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1230 PM Saturday...The main band of pcpn has pushed well ne of the area with only isolated convection possible this aftn. Expect convection to move off the mainland late this afternoon thru this evening in response to a cold front, currently draped e to w across northern nc, drops southward. Isolated tstorm wind gusts could reach 30 kt. the cfp will occur from n to s...and should be thru thru the ilm nc and sc waters by daybreak sun. the sfc pressure pattern this aftn and evening will yield mainly westerly winds, becoming nw-n later this evening and overnight as the cold front drops south. The sfc pg is relatively weak with 10 to 15 kt wind speeds thru the period as a result. Significant seas will run 2 to 4 ft...with dominating 6 to 8 second periods. The 4 footers will primarily occur across the ILM NC waters from Cape Fear northward. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM Saturday...Mainly northerly winds are expected behind an early morning cold frontal passage Sunday. Low pressure will develop along this front off the Virginia coast late Sunday, and this should maintain a tight enough pressure gradient for 15 knot wind speeds to occur locally through Monday. By Monday night high pressure over the midwest should move close enough to the Carolinas to knock winds down below 10 knots. LONG TERM /TUESDAY THROUGH WEDNESDAY/... As of 300 AM Saturday...Surface high sliding off the coast Tue will commence an extended period of south to southwest flow. Gradient remains weak with speeds on the low end of the 10 to 15 kt range. Along the immediate coast there will be potential for a sea breeze each afternoon, resulting in onshore flow around 15 kt each afternoon along the coast. Seas around 2 ft through the period with occasional 3 ft possible. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...DCH SHORT TERM...TRA LONG TERM...III AVIATION...RGZ

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