Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 171013 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 613 AM EDT Mon Jul 17 2017 .SYNOPSIS... A moisture-loaded air mass coupled with a dissipating and stalled front over the area, will bring periods of heavy rain through Tuesday. A building ridge of high pressure will bring hot temperatures and high humidity from mid-week into next weekend. Heat advisories and even heat warnings may be needed for the area later this week the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 3 AM Monday...The stationary frontal boundary which has lingered near the NC-VA border the last couple of days will become more diffuse today, but leave in place a very humid airmass across the eastern Carolinas. Precipitable water values will remain high through tonight, as much as 2.2 inches, although the ribbon of highest values will shift east through the period to just off the coast by tonight. It will be difficult to attempt to time the best chances of shower and thunderstorm potential today. Primary forcing will be from sheared vorticity emanating from the mid-level trough axis to the west, and with guidance trending lower for max temps today, the highest PoPs won`t necessarily occur during the mid to late afternoon. MOS guidance is signaling slightly better chances before 18Z than after, and by this evening, hi-res models are showing the bulk of precipitation shifting to or just off the coast. The risk of localized flooding will be present, and the most vulnerable areas will be portions of Georgetown, Williamsburg, Florence and Darlington counties, where several areas received 2 to 4 inches of rain Sunday and Sunday night. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 3 AM Monday...A transition period as the potential for heavy rainfall wanes Tuesday into Wednesday, as the leading edge of a massive upper ridge over the country`s heartland edges eastward into the area. Wednesday appears to mark the beginning of a pronounced heat wave, with heat alerts likely beyond this forecast period. The drying and warming aloft will sharply curtail convective coverage Wednesday compered to Tuesday. Measurable rainfall probabilities highest along and near the coast Tuesday, where convergence and upper support will reside. Heat Indices will hold below 100 degrees both days but highest on Wednesday. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 3 PM Sunday...The heat is back on for the long term. After one last day of low end convection possible on Wed, a large ridge builds into and over the southeast Thurs into the weekend. The mid to upper trough stretched down into the southeast on Wed will get pushed out of the area as large ridge of high pressure builds in from the central CONUS Thurs into the weekend. May see some cu develop and very localized convective development on Thurs into Fri as local area remains in NW flow on front end of ridge, but increasingly dry mid level air and subsidence will make it harder each day for any convective development especially Fri into the weekend. The mid to upper ridge will build over the southeast with anomalously high heights and 850 temps reaching up around 23c. This will combine with bright sunshine and a decent westerly downslope component to the low level flow to push temps well into the 90s by Thurs and Fri and should see temps above 100 in many spots over next weekend as ridge shifts almost directly overhead. The ridge should stretch from TX to the Bahamas over the weekend. The GFS suppresses ridge a little farther south as broad trough tries to push a cold front down into the Carolinas, but the ECMWF keeps the Carolinas under ridge with 595 dm heights directly overhead. The latter will obviously give a hotter forecast while the former could bring some clouds and possible a stray shower into NC. For now will keep with a more bullish ridge and a drier and hotter solution for the end of the week into next weekend. This excessive heat combined with dewpoints up into the mid 70s will produce heat indices between 105 and 110 from Thurs into the weekend with heat advisories and potential for excessive heat warnings over the weekend. A quick check on record max temps for some locations across the area run in the 97 to 102 range. Therefore we could see some record highs being broken and with overnight close to 80, we could potentially see some record high overnight, as well. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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As of 1015Z Monday...Isolated pockets of IFR cigs until 13Z due to light/calm winds and an abundance of residual moisture and wet ground in spots. VCTS applied to TAF sites since the area resides between waves, with weak subsidence expected much of the day. Prob30 for this evening as an impulse tracks across the region from SW to NE. Isolated MVF CIGS in stronger showers or a TSTM today and more widespread tonight. VSBY may also be lowered to 2SM in +RA. Extended Outlook...Flight restrictions will be possible in scattered showers and thunderstorms through Tue, then precipitation potential decreases significantly Wed-Fri.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 3 AM Monday...The pressure gradient will be relatively modest over the waters, but in general, a south-southwesterly flow around 10 knots will continue between Bermuda high pressure and a Piedmont trough inland. Seas are expected to remain in a 2-3 ft range through the period. Scattered to numerous showers and thunderstorms are expected across the waters today and tonight, associated with weak disturbances that propagate out from a mid-level trough across the western Carolinas. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 3 AM Monday...Displacement of oceanic high pressure east of Bermuda will result in a weak pressure gradient across the 0-20 NM waters this period with SW winds around 10 KT both Tue and Wed. Keep in mind however that winds and seas will be locally higher in and near scattered TSTMS. Radar updates are advised this period before venturing out. Seas of 2-3 feet will be a mix of SE waves 2 feet every 8-9 and S-SSW waves 1 foot every 4-5 seconds. LONG TERM /THURSDAY THROUGH FRIDAY/... As of 3 PM Sunday...Bermuda High regains control at the surface with S-SW flow mainly 10 kts or less. Expect less widespread showers and thunderstorms as ridge builds aloft through late week. Sea/land breeze will produce a spike and backing of winds in the afternoon into early evening and veering of winds to a more off shore flow overnight. Seas will remain in the 2 to 3 ft range, but could increase into Fri as winds increase out of the SW to W. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...8 NEAR TERM...CRM SHORT TERM...MJC LONG TERM...RGZ AVIATION...8

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