Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 180550 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 150 AM EDT Wed Apr 18 2018 .SYNOPSIS...
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A frontal zone will strengthen from the central Plains to NC early this morning. The front will retreat northward into VA this afternoon, ahead of an area of low pressure that will develop and track across the middle Atlantic states later today and tonight. A trailing cold front will cross central NC Thu morning, followed by much cooler high pressure that will build into our region through Sat.
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&& .NEAR TERM /TONIGHT/... As of 1010 PM Tuesday... A complex mid-upr low centered over srn Quebec, and with multiple satellite disturbances rotating around it, will continue to wobble nnewd tonight, while a longwave ridge evident in 00Z upr air data over the MS Valley and cntl Canada, will migrate ewd. Associated strong height rises aloft, on the order off 100-150 meters, have already expanded into NC since this morning, with additional height rises and subsidence aloft, forecast for tonight. Meanwhile in the lower levels, a couple of closely-spaced frontal zones were analyzed this afternoon and evening across the VAs and lwr OH Valley, and from the mid-South to SC, respectively. The nrn- most boundary, analyzed at 02Z from nern NC wnwwd to a 1008 mb low centered near Danville and South Boston, VA, then wwd through swrn VA, srn KY, and the mid MS Valley, will strengthen while settling slowly swd to a 12Z Wed position near Cape Hatteras to Fayetteville to Statesville, NC. A strong WAA regime atop this swd settling boundary, which yielded an impressive 17C 850 mb temperature change/increase observed at GSO from 12Z Tue to 00Z Wed, and Fgen related to that frontal zone, will contribute to upward motion in the sfc to 850 mb layer tonight, beneath the aforementioned deeper, mid-upr level subsidence. While this lwr level lift will occur in an initially dry layer characterized by 925-850 mb dewpoint depressions of 15-20C evident in 00Z proximity RAOB data, the models suggest that this lift will cause the current area of high-based stratocumulus over ern KY/srn WV/swrn VA to develop sewd along and north of the VA/NC border between 06-12Z Wed, with associated partly to mostly cloudy conditions likely to develop over the nrn NC Piedmont during that time. Skies are expected to remain clear elsewhere. The dry air mass in place, and lessening surface winds within the pressure trough related to the aforementioned frontal zone, will favor fair to good radiational cooling conditions, except late tonight near the VA border, where increasing cloud cover will cause temperatures to level off or rise slightly in the several hours prior to daybreak - lows in the 40s. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... As of 235 PM Tuesday... As the mid level flow at our latitude flattens with rising heights, the surface frontal zone over far N and NE NC will lift to our NE Wed, putting NC solidly within the warm sector, with a strengthening SW flow. Tonight`s clouds across the N and NE will continue to dissipate early Wed morning, and with a generally dry column and no immediate moisture upstream, we should see mostly sunny skies, with little more than scattered flat afternoon cumulus. Winds should again be sustained near 15 mph with gusts around 20-25 mph. We do have some concerns for adverse fire behavior Wed, with strengthening winds and successive windy days that continue to dry out fine fuels, however the RH values should be just above critical criteria. Thicknesses will start the day near normal but will soar through the day, with late-day 850 mb temps approaching 15C, suggesting highs from the upper 70s to lower 80s, and we may even see some mid 80s in the far S. Expect mild lows of 55-63 Wed night, with SW winds staying elevated at around 10 mph. -GIH && .LONG TERM /THURSDAY THROUGH TUESDAY/... As of 230 PM Tuesday... Continental high pressure will begin to influence the pattern on Thursday, bringing a dry airmass into the area. This combined with the exiting low pressure system to the northeast will keep a tight pressure gradient over the area, leading to breezy conditions for much of the day. With gusts of 25 to 30 kts possible, and min RH values hovering around 30 percent, fire weather could become a concern by Thursday afternoon. Gusts may remain through the evening hours before finally relaxing overnight Thursday night. Highs in the upper 60s to upper 70s from NW to SE. Lows Thursday night in the low 40s. Broad high pressure will remain in control through the weekend with only some increasing clouds by Sunday afternoon as the high pressure splits and clouds start to build in as a result of northeasterly winds against the mountains. Temperatures will remain cooler than normal with highs generally in the 60s as opposed to the low 70s expected this time of year. Overnight lows gradually rising through the 40s during this period. For early next week, models are split on what will happen to a low pressure system over the deep south with the GFS taking a more northerly track and bringing precipitation into central NC from the south by early Tuesday morning. The EC solution takes the system south towards the Florida Panhandle keeping NC dry. For now will introduce a low chance of showers for Tuesday given the uncertainty. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 150 AM Wednesday... There is a high likelihood that VFR conditions will persist across central NC through Thursday afternoon. Of note to small aircraft operators will be gusty sfc winds this afternoon, most likely after 2 PM, with gusts 20-27kts probable. While the sfc gustiness will subside just prior to sunset, a low level jet passing overhead will result in low level wind shear parameters Wednesday evening across most of central NC, and primarily along and east of highway 1 overnight. SW winds around 2000ft expected to be 40-45kts. Sfc winds will be gusty again Thursday as a cold front glides eastward across the region. Gusts in the 25-30kt range will be probable, strongest in the morning through early afternoon. VFR parameters are expected to persist into the weekend. Cool high pressure will build into the area Friday and linger overhead Saturday into Sunday. The next threat for sub VFR ceilings may occur as early as Sunday night, but may hold off until late Monday or Monday night.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...WSS

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