Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 202052 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 350 PM EST Mon Feb 20 2017 .SYNOPSIS... High pressure will extend along the East Coast through early Tuesday. An upper-level disturbance will cross the Southeast states Tuesday night into Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 310 PM Monday... Quiet weather through tonight. Dry high pressure at the surface centered over southern Quebec will continue to ridge down the east coast into central/eastern NC as its center drifts to New England. Passage of the amplified mid level ridge axis over the area tonight will ensure dry and stable air aloft, although high level moisture streaking up and over the ridge will bring increasing high clouds through the night. The low level easterly flow within a stabilizing surface based layer may bring a few low clouds into the far western Piedmont late tonight, although models have been trending drier in recent runs. Expect no more than partly cloudy skies overnight, although the western CWA, where high clouds will be most thick, should trend to mostly cloudy late. Lows will range from the upper 30s in the NE, beneath the core of the ridge axis where both thicknesses and sky cover will be lower, to the mid 40s west. -GIH && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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As of 350 PM Monday... The surface high will continue to extend southward through eastern NC Tue as its center moves off the coast of New England. The mid level ridge axis will also move offshore as the full-latitude trough approaches from the west. This trough is currently phased but will split on Tue, with the northern portion deamplifying as it progreasses through Quebec and the Northeast through Tue night, while the southern portion drifts much more slowly along the Gulf Coast. Improved overrunning flow as the 850 mb ridge axis shifts off the Carolina coast Tue night along with falling heights will lead to a chance for showers in western sections, mainly after midnight. Forcing for ascent will initially be fairly weak however, as the weakening mid level flow will lead to weaker DPVA, although upper divergence will steadily improve. Low level moisture transport will exhibit a small rise overnight over the western CWA, with rising PWs. The NAM brings more substantial rain into our far NW Tue night as compared to the GFS/ECMWF, with much higher PW. The more muted and slower GFS/ECMWF solution is preferred based on its consistency, the weaker low level mass convergence, and the strength of the slowly departing ridge axis, so will only bring up pops into the good chance range in the NW Tue night, with little to no pops along/east of Highway 1. With the dip in thicknesses and increase in clouds Tue, will have highs in the mid-upper 60s, still well above normal. Lows Tue night in the mid 40s NE to lower 50s S. -GIH
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/... As of 247 PM Monday... The pattern begins to change for midweek and although we stay warm, a wetter pattern will bring more clouds and some chances for rain late in the week. That being said no day looks like a washout at this point and rainfall totals for the week look only to be about a half an inch at the most with some locations receiving very little rain. Temperatures will remain in the 60s and 70s throughout the period. To break it down further, Wednesday will bring our fist chance for rain as a low pressure system in the Gulf of Mexico dives southeastward towards the Florida Peninsula. As a surface high sinks southward, central NC will be on the northern fringes of this system and any rain that does occur will be a result of some isentropic lift and moisture advection from the south. Best chances will be in the western part of the forecast area. On Thursday a developing low pressure system to the west will establish a warm front along our northern border and begin to advect northward. As a result, best chances for any appreciable rain Thursday will be along the VA border counties. For the most part Friday looks dry as the low to the west tracks northeastward into the Great Lakes. As it does so frontogenesis will occur just west of the Appalachians as a cold front moves into North Carolina Saturday morning and across our area by Saturday late afternoon/evening. This may be our best chance for rain during the long term with a non-zero chance of some Thunder, especially in the southeast where some better instability may be allowed to develop. Behind the front, high pressure moves in for Sunday signaling a return to clear skies and dry weather. && .AVIATION /18Z Monday through Saturday/... As of 112 PM Monday... High confidence in VFR conditions areawide through at least this evening, as high pressure builds in from the north, topped by warm and stable air aloft. Mostly just high clouds based above 18000 ft AGL are expected through tonight and Tuesday across the area, however at INT/GSO, increasing low level moisture within stable low levels late tonight may result in a few low clouds based below 900 ft AGL and perhaps shallow MVFR fog 08z-12z tonight. Elsewhere, no low clouds/fog are expected tonight. Winds will stay light from the NE, trending to ESE areawide over the next 24 hours, but speeds will be a bit stronger at RWI/FAY this afternoon. Looking beyond 18z Tue, VFR conditions will hold through Tue evening. We will see a chance for late-night and early-morning sub- VFR fog/stratus repeat areawide each day through the remainder of the week. MVFR to IFR conditions with a few showers are possible late Tue night through Wed as an upper trough crosses the region. A cold front will cross the area Sat, bringing a chance for showers and MVFR cigs. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS/BLS NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...Hartfield

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