Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 170101 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 901 PM EDT Sun Jul 16 2017 .SYNOPSIS... Relatively cooler temperatures are expected today and Monday with increased thunderstorm activity as a stalled front lingers across the area. This front should dissipate Tuesday. Hot and humid conditions should redevelop for the second half of next week as high pressure expands eastward from the Central Plains states. && .NEAR TERM /THROUGH MONDAY/... As of 330 PM Sunday...Latest 88D Mosaic shows storms developing quite rapidly across the western portions of the FA and just upstream across both CAE and CHS CWAs. This activity is being aided by dynamics associated with sheared mid-level vort centers. With progged PWs around 2.00 inches thruout the ILM CWA and progged K indices 36+ and quite the saturated sounding for various locations across the FA...all this points to Heavy Rain as the primary attribute to thunderstorm activity across the ILM CWA this aftn and evening. Localized flooding is likely across portions of the FA. With progged storm motions slightly slower around 10 or 10-15 mph, it will mainly be the training aspect of this convection that allows pcpn amounts within a short period to climb and possibly come close to local FFG Value thresholds. Have slightly adjusted the QPF for late this aftn and evening...and again during the pre-dawn Mon hrs thru midday Mon...both times slightly hier...and used WPC guidance as a first guess. HPC has the ILM CWA within a slight risk for Excessive Rainfall covering now thru Mon morning. Overall, pcpn amounts this aftn thru late Mon will be greatest across the coastal counties followed by a decreasing trend the further inland one goes. POPs will run in the good chance to likely categories thru Monday with a brief reprieve late this evening to several hrs after midnight. Models indicate some drier air to work it`s way into the FA from the NW as the upper trof moves eastward enough to push the majority of this baroclinic zone to along and just off the Carolina Coasts. However, not far enough to remove the threat for POPs which will be decrease to a low to modest chance by Mon evening. Max temps in the 80s to near 90 if insolation continues to poke thru. Tonights lows in the 70s. Mondays highs will run at or a few degrees below Sun maxes. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...Stalled boundary which has been plaguing the area causing rounds of convection each day will finally dissipate Tuesday, leading to more typical summertime conditions once again through the latter half of the short term. Drying evident on soundings beginning late Monday will cause convection to wane quickly during the evening hours into Tuesday morning. As PWATs fall to around 1.5 inches, some residual shower activity is likely the first half of Monday night, but will drop POP to silent by daybreak Tuesday. No significant surface features evident Tuesday thanks to the frontal dissipation, but continued troughing aloft and temps climbing back to near 90 will create a summertime unstable atmosphere, and scattered diurnal tstms are possible along the typical sea breeze and piedmont trough. Do not expect widespread coverage, and with much drier air aloft many places may remain dry Tuesday, but the steepened lapse rates thanks to the persistent troughing at 500mb necessitates at least low-CHC POP during the aftn/eve as MLCape climbs to 1500 J/kg. Convection will wane in the typical nocturnal fashion Tuesday night and expect a dry period into Wednesday morning. As high pressure begins to strengthen offshore and thicknesses climb slowly, mins through the short term will remain above seasonable values, 71-74 Monday night, warmest at the coast, and a degree or two warmer everywhere Tuesday night. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 300 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 /00Z MONDAY THROUGH FRIDAY/...
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As of 00Z Monday...Precipitation has evolved into a stratiform rain with rain falling out or mid clouds with some embedded thunder. Rainfall rates are not all that heavy and visibility should only be reduced briefly to MVFR in showers and a rumble of thunder through 05-09z. There is a possibility for low stratus and fog from about 09z-13z, mainly inland, and have included a risk for MVFR/IFR at KLBT and KFLO at this time. For Mon, have included VCTS at all the terminals after 16-17z. Later packages may opt for inclusion of flight restrictions due to showers and thunderstorms. Extended Outlook...Flight restrictions will be possible in scattered showers and thunderstorms Mon night and Tue.
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&& .MARINE... NEAR TERM /THROUGH MONDAY/... As of 330 PM Sunday...Thunderstorm activity will continue to pick up over inland areas of the Carolinas this afternoon and eventually push off the coasts during late this aftn and thruout the evening. The nocturnal nature of tstorms developing over the local warm mid 80 degree waters late tonight and the overnight period. This will be in addition to the tstorms that move off the mainland overnight. Expect scattered to numerous coverage from late this aftn thru tonight and likely continuing thru Mon mid-morning. With the stalled sfc boundary remaining inland thru tonight, winds will generally be SW at 5 to 10 kt, locally hier and variable in direction in Tstorms. Could see winds back to a more southerly direction during the pre-dawn Mon hrs as a weak sfc low moves along the stalled front. Significant seas will run 2 to 3 ft thruout and mainly dominated by a 2+ foot ESE to SE ground swell at 8 to 9 second periods. Latest buoy obs trends and wavewatch3 guidance both illustrate this dominating swell. SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...High pressure offshore will become stronger through mid-week as it ridges westward from the Atlantic Ocean. The gradient remains relatively light, so winds will persist from the SW at 10-15 kts through the period. These light winds will allow a continued SE ground swell at 2ft/9sec to be the primary wave group, driving seas to 2-3 ft. LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 300 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 Thurs into Fri as winds increase out of the SW to W. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...DCH SHORT TERM...JDW LONG TERM...RGZ AVIATION...RJD

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