Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 271854 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 255 PM EDT Thu Jul 27 2017 .SYNOPSIS...
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A cold front will approach from the northwest tonight, and cross our region late Friday night.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 255 PM Thursday... Little change required to the near term forecast. Highest threat for scattered convection still appears to be across sections of the northwest Piedmont through 01Z. Atmosphere has become moderately unstable as sfc dewpoints have rebounded into the lower 70s. A pocket of slightly enhanced winds in the 850-700mb layer is projected to increase the effective bulk shear in vicinity of the VA border to around 30kts by late afternoon. This hear coupled with the available buoyancy should lead to the initiation/maintenance of scattered convection late this afternoon into the first half of the evening. The convective threat appears best along and north of I-85, and much less so to the south and southeast of Raleigh. DCAPE values have improved from what was expected earlier today, increasing the probability of strong or locally damaging wind gusts with the stronger storms. After 01Z, may see isolated/scattered convection drift east into sections of the northeast Piedmont and northern coastal plain though the convection should be weaker in intensity. A series of weak perturbations aloft may maintain a few showers/isolated storms into the overnight, mainly north of highway 64.
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&& .SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
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As of 255 PM Thursday... A lingering mid level shear axis overhead is expected to become reinvigorated late Friday into Friday night with the approach of a strong s/w diving sewd from the Great Lakes into the northern mid- Atlantic. This feature will interact with available instability and shear to produce scattered-numerous convection, essentially from late Friday morning into Friday night. Effective bulk shear weak at best at the inset though this is expected to improve by early Friday evening, leading to a threat for broken/bowing convective segments and attendant damaging wind threat. This scenario is based on an atmosphere that will have adequate heating prior to the arrival of the upper dynamics. The degree of convection overnight tonight through early Friday morning will play a role in the coverage/intensity of convection Friday afternoon and evening. If scattered/numerous showers-storms are in progress early Friday, it may hinder the ability of the atmosphere to achieve optimum instability by the time the better dynamics aloft arrive late Friday into Friday evening, limiting the potential for scattered severe storms. A sfc cold front associated with the s/w crossing into the northern mid Atlantic will approach central NC late Friday, and enter the Piedmont counties Friday night, slowly edging sewd into early Saturday. This feature will maintain a decent threat for showers and a t-storm or two, primarily south and east of Raleigh overnight Friday night. High temperatures Friday dependent upon the convective coverage Friday morning, and when convection re-develops Friday afternoon. Expect the hottest temperatures to occur across the Sandhills and southern coastal plain where near 90-lower 90s expected. Extensive cloud coverage and good potential for scattered convection will likely hold temperatures in the 80s across the northern Piedmont.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/...
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As of 230 PM Thursday... The surface front will be in vicinity of the coastal plain Saturday morning, with deep moisture and precip coverage on the decline as low level flow shifts westerly. As such, will taper off morning PoPs in the east from 60% to 30% by afternoon, with only slight chances elsewhere. Initial cool air advection will be underway behind the front, with highs Saturday ranging from low 80s north to mid 80s south. The cool air will surge south Saturday night as the upper trof rotates through, and the strong mid level forcing will spawn scattered convection Saturday night, mainly across the northeast. Mins Saturday night will be mostly in the mid 60s, and Sunday`s highs will be downright pleasant, with lower humidity to accompany temps mostly in the lower 80s, with some locations in the northeast perhaps topping out in the upper 70s. The cutoff low lifts northeast Sunday night and Monday, and the remainder of the extended at least through Wednesday will be dry as surface high pressure building into the Ohio Valley delays moisture return into the area. Gradual extension of the Bermuda high into the northern Gulf will eventually prevail, beginning with warm air advection on Wednesday, to be accompanied by the return of moisture laden air on Thursday. As such, a gradual warm-up is expected through the week, with highs Monday mostly in the mid 80s, rising into the upper 80s Tuesday and Wednesday, and back to the upper 80s/lower 90s on Thursday. Morning mins will follow the trend as well, from mostly mid 60s Monday morning to around 70 by Thursday morning.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/... As of 105 PM Thursday... While VFR parameters will prevail across much of central NC through this evening, scattered convection and associated MVFR parameters will threaten the Triad terminals primarily between 20Z-01Z. While the bulk of the scattered convection will dissipate by mid evening, a few showers will likely drift across the northern counties into the overnight. Additional scattered convection and associated MVFR parameters appear likely across central NC Friday through Friday night as a sfc cold front drifts southward. Areas of MVFR ceilings and a few showers are possible Saturday as the main upper trough drifts across the region. A drier, more stable atmosphere and attendant VFR parameters expected Sunday through Tuesday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...mlm AVIATION...WSS

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