Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 211929 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 329 PM EDT SAT MAY 21 2016 .SYNOPSIS...
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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 continuing into next weekend.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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As of 300 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 partially keep a lid on convection this afternoon. Daytime insolation has broken thru to the sfc...and now the stratus deck has 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 from these storms will be strong wind gusts. Have highlighted the hazardous weather outlook to convey this potential. Afternoon highs should break into the 80s across the majority of the ILM CWA. 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 after the cfp. Leaned toward the higher end of the available min temp mos guidance.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
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As of 300 PM Saturday...The start of this period will feature the upper trof extending down the east coast Sunday morning. The upper trof closes off and nearly becomes a cutoff low depending on your definition. The upper low`s center over the VAs Sunday afternoon is progged to drop southward to a position over eastern NC by daybreak Mon. And remarkably, the models are in pretty good agreement in lifting this closed low northward to basically off the NJ Coast by daybreak Tue. Like spokes on a bicycle wheel, there will be mid level s/w trofs or vorts rotating around this upper low. With decent or o.k. lapse rates, available moisture, and if enough daytime insolation to further aid instability, convective chances should increase ahead and in the vicinity of these rotating s/w trofs. Models are at times different with the timing of their movement across the fa, but nevertheless the threat for convection will exist especially during each day. At night, depending on the strength of the upper s/w trof rotating thru, will likely have to carry low pop convection well into Sun night. In addition...model sounding data indicate 500mb temps drop to -19 degrees C and as a result, small hail from any of the convection will become a possibility. The end result is that this cold core upper low affecting the area Sun thru Mon night means temperatures will average 5 to 10 degrees below normal this period. Normal daytime highs run in the low to mid 80s and night time lows in the lower 60s.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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As of 300 PM Saturday...Warm summertime weather forecast for the upcoming week as a pattern more typical for this time of year finally sets up. Upper level low will be migrating off to the northeast on Tuesday as ridging blossoms northward from the Gulf of Mexico. As this happens...surface high pressure will re-center itself off the southeast coast...with a Bermuda High type setup forecast for the remainder of the period. The combination of warm return flow around the surface high and bulging heights beneath the mid-level ridge will create warm and mostly dry conditions as subsidence prevents much in the way of even diurnal convection. The exception still looks like Thursday when a weak impulse will rotate atop the ridge and cause subtle height falls...which when combined with the increasingly unstable airmass as heat and humidity increase...should fire off some storms Thursday/Thursday night. Otherwise...the extended looks very nice with highs and lows slightly above climo under ample sunshine.
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&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/... 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. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 300 PM Saturday...The earlier band of pcpn has pushed well ne of the area by early this aftn. This will leave only isolated convection at best for this aftn. Expect convection to move off the mainland thruout the evening hrs in response to a cold front, currently draped ne to sw across northern nc, dropping southward tonight. 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 after the cfp. The sfc pg will remain relatively weak with 10 to 15 kt wind speeds thru the period. 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 PM Saturday...The sfc cold front will slowly drop south of the area waters early Sunday morning. Winds behind the cfp, will veer to the NW and NNW Sunday and persist in this direction thru Monday. For Monday Night, with the upper low now lifting to the north, away from the area waters, the sfc pressure pattern will become less dominated by the cyclonic flow associated with this upper low. This will result in winds slightly backing to a westerly direction. The sfc pg thru Monday will remain weak across the ILM SC waters, and 1 step hier than weak across the ILM NC Waters. This will yield wind speeds in basically the 10 to 15 kt range...with the hier side of this range across the ILM NC Waters. Significant seas will range between 2 and 4 feet thru the period, with the 4 footers occurring primarily early in the period, basically thru early Monday and mainly across the ILM NC Waters. Dominating periods will basically range between 7 and 9 seconds. With an offshore wind, wind driven waves will be minimal due to the limited fetch. As a result, an ese 1 to 3 foot ground swell will become the primary significant seas producer, hence the hier dominating periods. Upper s/w trofs rotating around the upper low will sporadically move across the area waters thruout this period. Dynamics from these will be enough for convection to also sporadically occur. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 300 PM Saturday...Westerly winds Tuesday will transition to the S/SW Wednesday and then remain from that direction for several days as high pressure offshore becomes the dominant feature. The gradient in the vicinity of this high will be weak...so wind speeds will be around 10 kts each day regardless of direction. Although a SE 8-9 sec swell will amplify within the spectrum...especially late in the period...wave heights will remain just around 2 ft Tue/Wed...rising to 2-3 ft late thanks to that growing aforementioned swell.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...DCH SHORT TERM...DCH LONG TERM...JDW AVIATION...RGZ MARINE...DCH/JDW

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