Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 180921 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 420 AM EST Wed Jan 18 2017 .SYNOPSIS... A cold front will track southeast through central North Carolina today. In the wake of the front, high pressure will build into the region from the northwest tonight and Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 320 AM Wednesday... Cold front approaching the area is currently settled along the WV/VA border. Out ahead of the front, radar showing some light rain along the VA/NC border north of the Triad and that will gradually work its way into the northern tier today. Short term models do not show a lot of precipitation with the front as it moves through the area. There will be a few wind gusts however up to 20 kts or so. Temperatures will be tricky as the timing of the front could mean near steady state or slightly falling temperatures through the afternoon hours. Regardless highs will be in the lower 60s across the north and near 70 degrees in the south. Lows in the upper 30s to low 40s. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 320 AM Wednesday... High pressure will be in control for much of the day on Thursday as an upper level ridge moves over central North Carolina. A bit cooler with temperatures in the upper 50s to lower 60s. Winds will be light and variable under the surface high and the airmass will be dry. A southern stream low will start to encroach on the area by early Friday morning with increasing clouds throughout the night on Thursday night but all precipitation is expected to hold off until Friday. Lows Thursday night in the low to mid 40s. && .LONG TERM /Friday through Tuesday/...
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As of 420 AM Wednesday... Model agreement with the general pattern continues to be better than usual through the weekend, although some important differences in the low level pattern are evident, and notable timing differences crop up by Mon/Tue. Models are overall trending wetter in this time frame. Temps will remain quite mild, with all cold air staying bottled up over northern Canada and the Arctic region. Fri/Fri night: The mid level trough extending from the Midwest through the Ohio Valley to SC early Fri will continue to pivot to the NE through NC and into the Mid-Atlantic and Northeast Fri, and will be followed by prominent shortwave ridging over the Southeast Fri night. Focused mid level DPVA and upper divergence associated with passage of the trough, along with high PW, will support a band of rain shifting through central NC Fri morning, with a west-to-east tapering down Fri afternoon, and dry but mostly cloudy conditions Fri night as low level moisture pools over the area with a light surface flow. Will go with likely pops Fri morning, trending downward Fri afternoon. The ECMWF/NAM bring today`s surface front back northward into NC, albeit in a very diffuse form, while the GFS is more defined in keeping the frontal zone near the NC/SC border, favoring thick low clouds and cooler temps, especially over northern NC. With well-above-normal thicknesses tempered a bit by the morning rain and lingering clouds late Fri into Fri night, expect above normal temps with highs from the mid 50s N to lower 60s S. Lows 45- 50. Sat/Sat night: What once appeared to be a fairly dry day now looks be trending wetter. Thanks to a powerful mid and upper jet from CA across the Desert Southwest and adjacent Mexico to TX, a strong low will be closing off over OK/TX before shifting to AR/LA through Sat night. Subtle perturbations ejecting from this low/trough will swing NE into the Carolinas Sat afternoon/night, while bands of enhanced upper divergence spread in from the SW, a product of ideally juxtaposed upper jetlets over the Ohio Valley and over the NE Gulf. Low level flow will be ramping up with an 850 mb jet nosing into the Carolinas, fostering moist isentropic upglide along/above the diffuse surface frontal zone. And models agree on PW staying well above normal as they generate precip over the area, mainly across the southern and western CWA Sat and areawide Sat night as heights aloft continue to fall with the approaching trough. Will bring in low chance pops mainly S on Sat, trending up to good chance Sat night. The rain and clouds will lead to a tighter diurnal temp range. Highs in the low-mid 60s Sat followed by lows in the mid 40s to lower 50s. Sun into Mon: The mid level low is expected to cross the lower Miss Valley, Gulf States, and Carolinas before moving into the interior Mid-Atlantic region through late Mon. This system will be accompanied at the surface by a complex but likely occluded frontal system, with vigorous deep forcing for ascent promoted by a 40-50 kt low level jet punching into the area, intense upper divergence within a zone of ascent between two ideally juxtaposed upper jets, and large mid level height falls. Confidence is high in a period of potentially heavy rain and embedded storms with strong kinematics and marginal instability and lapse rates, but the timing is less certain, as the GFS becomes much slower (farther SW) than the ECMWF with the upper low and trough as it swings ENE through our area with a negative tilt. Will lean toward the faster ECMWF, which has good agreement with its ensemble mean. Will have likely pops Sun/Sun night, with the best chance of heavy rain and storms Sun evening, followed by a SW-to-NE tapering down of pops on Mon as some drier mid level air works in from the SW. A strong storm or two remains possible given the energetic wind field, despite the weak instability noted by the models. Lingering instability showers and isolated storms will persist Mon with indications of high lapse rates and abundant moisture. Temps should remain above normal despite the clouds/precip. Tue: We should be on the west side of the departing low/trough shifting to our east and north, with yet another mid level ridge building in. Expect dry weather and a trend to fair skies. With no cold air available, temps will remain above normal. -GIH
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&& .AVIATION /06Z THURSDAY THROUGH SUNDAY/... As of 100 AM Wednesday... 24 Hour TAF period: VFR conditions across the area this morning as winds remain between and 5-10 kts with a few gusts of 15-20 kts. As a front approaches the area later this morning, there is some uncertainty whether or not low ceilings will develop. At this point feel that there will be a chance for some MVFR/IFR ceilings during the 9-12Z period. Some very light precipitation may accompany the front but that will be of minimal impact. Some gusty winds up to 20 kts this afternoon are expected. Conditions will return to VFR in the late afternoon/early evening time frame. Long term: VFR is expected to hold until Friday when the next system is expected to move through from the southwest. A stronger system is expected to impact the area early next week. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Ellis SHORT TERM...Ellis LONG TERM...Hartfield AVIATION...Ellis

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