Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 170808 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 407 AM EDT Mon Jul 17 2017 .SYNOPSIS... A weak cold front will gradually dissipate overnight into Monday. High pressure aloft will build east from the Plains states Tuesday through Friday, leading to hot and humid weather. && .NEAR TERM /OVERNIGHT/... As of 1015 PM Sunday... Little change to the near term forecast. 00Z upper air analysis depicts a fairly wet atmosphere over eastern NC while the western half drier and more stable. This contrast is nicely illustrated on the GSO and MHX soundings with MHX reporting precipitable water value of 2 inches while GSO was 1.1 inches. This separation of the air masses delineated by a weak sfc trough and a mid level shear axis aligned close to our east of highway 1. The evening analysis also picked up on the minor perturbation lifting newd across eastern GA into SC. This feature will continue to lift east-ne, crossing the eastern sandhills and southern coastal plain after midnight. This disturbance interacting with the available moisture will trigger a few showers and isolated thunderstorms later tonight, primarily in vicinity of the I-95 corridor south of Smithfield. Some of these showers may venture as far west as the southern and eastern sections of the Triangle. Otherwise expect variably cloudy skies. Locations that experience partial clearing after midnight may see areas of fog developed, especially if they received a heavy downpour this afternoon. Thus the fog potential, if it occurs, appears best east of highway 1. Overnight temperatures in the upper 60s to lower 70s. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 227 PM EDT Sunday... Little change in the pattern with the longwave trough axis remaining along the Appalachians. Yet both the GFS and NAM show the plume of highest pwat shifting to our east, and this is noted in forecast soundings that show pwat falling to 1.5" or less across our entire CWA Monday afternoon. Models suggest the best chance for rain will be to our west developing over the mountains and drifting east across the foothills, and to our east near the coast in the deeper moisture, with lesser coverage across central NC compared to today. Thus, will stay just below PoPs climo, going with 20-30% across our CWA, highest east near the better moisture and lowest west. Nearly all the guidance suggests high temps near climo, thus upper 80s for highs. Mainly dry Monday night with any isolated showers/tstms dissipating by early overnight. Lows around 70. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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As of 400 AM Monday... A pair of shortwave troughs evident in WV imagery over wrn NC and central IN this morning will contribute to the development of a mid- upper low over the middle Atlantic states during the next 24-48 hours, which will move slowly east and off the middle Atlantic coast by 00Z Thu. Meanwhile, an upper ridge now over the central Plains will strengthen and expand/build esewd across the middle MS and TN Valleys through the weekend. Central NC will consequently lie on the far srn fringe of a belt of initially nwly flow aloft that will gradually back to wly, as the ridge becomes situated over the southeastern U.S. by Sun. At the surface, a trough will become established in the lee of the srn and central Appalachians, on the wrn periphery of high pressure over the central and wrn N. Atlantic. Meanwhile, a frontal zone will settle swd, into VA by Fri night-Sat, before retreating nwd by Sun- Sun night. This frontal zone may become briefly modulated swd into nrn NC by convective outflow Fri night-Sat; and precipitation chances will be maximized (in the chance range) then and there. Otherwise and elsewhere, the presence and influence of the sub- tropical ridge will likely restrict diurnal convection to differential heating zones over the mountains and along the sea breeze. The bigger story will likely become another round of heat and high heat indices, as temperatures beneath the ridge climb into the middle 90s to around 100 degrees - hottest Fri-Sat. When combined with surface dewpoints ranging from the middle to upper 60s west of the Appalachian-lee trough (over the nw NC piedmont) to lower to middle 70s to the east of that feature (over the Coastal Plain) heat index values between 100 and 110 degrees are expected to result.
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&& .AVIATION /06Z MONDAY THROUGH FRIDAY/... As of 140 AM Monday... 24 hour TAF period: Widely scattered light showers continue to pop up periodically in the moisture laden airmass over the area. Coverage is too sparse to include as a prevailing or tempo group outside of FAY where coverage will be enhanced by a mid level wave lifing up the coastal plain this morning. Predawn MVFR fog and perhaps some stratus is expected with humidities at 100% with light southerly flow, with improvement by 13Z except perhaps at FAY where MVFR ceilings are possible through mid day. Diurnal convection on Monday will be mainly focused in the east...FAY & RWI. Long term: Diurnal showers and storms will be possible through midweek and along with that the possibility for fog/low stratus each morning through the period. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...WSS SHORT TERM...np LONG TERM...MWS AVIATION...mlm

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