Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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940 FXUS62 KRAH 211954 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 255 PM EST Tue Feb 21 2017 .SYNOPSIS...
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High pressure extending along the East Coast will move offshore tonight. A slow-moving upper level trough will cross the Southeast and Mid Atlantic states through Wednesday night.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 255 PM Tuesday... Rain chances late tonight look pretty small outside of the far W and NW CWA. The split mid level trough, consisting of a broad low- amplitude wave crossing the eastern Great Lakes/Quebec/Northeast states and a prominent deep low moving from NE LA into the NE Gulf, will bring increasing moisture and forcing for ascent to our area. But forecast soundings show a notable dry layer in the mid levels, likely leading to smaller hydrometeors, and DPVA with the approaching trough will be trending lower given the weakening mid level winds. Model-generated precip, including from the SREF/GFS/ECMWF, is generally confined to western NC, where the better moist upglide and upper divergence will reside, while the slowly departing low- and mid-level ridges should protect much of the central and eastern CWA from measurable precip. Will restrict pops through tonight to just the far W and NW CWA. With gradually increasing and thickening clouds from the west, expect a trend to mostly cloudy skies areawide. Lows from the mid 40s NE to the lower 50s SW. -GIH
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... As of 245 AM Tuesday... The closed low aloft will slide further southeast through the eastern Gulf of Mexico and over FL through Wednesday night, taking the best moisture with it. There is still a chance for some light rain to occur over Central NC on Wednesday as the weakened northern stream trough passes overhead, but exactly where the rain will fall is somewhat uncertain. Regardless, skies will be cloudy throughout the day and rainfall totals are not expected to be very high. The highs on Wednesday (like the temperatures the previous 24 hours) will depend on the return flow into the region from the high offshore. For now, expect a 10-15 degree temperature gradient from NW to SE (60 degrees NW to low-mid 70s SE). There will be enhanced east-southeasterly flow into the southeast U.S. to southern Mid- Atlantic coast Wednesday night as a result of being sandwiched between the Gulf low and the high over Bermuda. Though the best warm, moist advection will be south of the NC coast, expect a continuation of the above normal temps and overnight lows warmer than the previous night (low to mid 50s NW to SE). && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 325 AM Tuesday... The upper air pattern across central NC will continue to support very warm conditions though the atmosphere will be slightly unsettled. A strong cold front will cross our region this weekend followed by a slightly cooler and tranquil weather regime. A s/w ridge will build into our region Thu=Fri in response to the departure of an upper level low off of south FL. These rising upper heights will maintain very warm conditions across our region. Closer to the surface, low level southerly flow will gradual increase the moisture content of the column, yielding variably cloudy skies. With weak speed convergence occurs, a few stray showers will likely develop. This scenario appears more plausible over the western Piedmont both Thursday and Friday though most locations will remain rain free. With surface based CAPE approaching 1000 j/kg Thursday afternoon, a thunderstorm may be possible. Temperatures will remain a solid 15-20 degrees above normal though still a couple of degrees shy of record warmth. A mid-upper level s/w crossing the Great Lakes Fri-Sat will drive a sfc cold front southeastward into the Carolinas Saturday. This front will encounter a adequately sheared and slightly unstable air mass to support broken bands of showers and thunderstorms Saturday afternoon, primarily along and east of highway 1. Cannot rule out the possibility of a few strong/severe storms as mixed layer CAPE approaches 1000 j/kg though low level helicity is lacking. Blustery nw winds behind the front Saturday night/Sunday will usher a cooler/drier air mass into central NC. While air mass is cooler, afternoon temperatures will still average 4-6 degrees above normal for late February. Dry weather anticipated Saturday night into Monday as deep wly flow will limit precipitation chances. && .AVIATION /17Z TUESDAY THROUGH SATURDAY/... As of 1210 PM Tuesday... Expect VFR conditions through this evening with mainly mid and high clouds increasing from the southwest. Tonight, low pressure will move into the Gulf Coast states, sending low level moisture northward to the Triad/Triangle and eventually the coastal plains. Will start to see sub-VFR cigs and vsbys working to most terminals after 06z with best threat of any rain over INT/GSO, with drizzle toward RDU and RWI after 08z. With high pressure keeping flow off the Atlantic will see some fog as well, so vsbys could drop to IFR, though confidence is not high enough to add in the terminals except INT closer to the foothills. As we head into Wednesday will be tough to dislodge the lower cigs but models favor most sites going to VFR after 15z, though in-situ damming over the Triad should keep INT/GSO IFR til the end of this taf period. Looking ahead: Expect cigs in the MVFR/low end VFR range to persist through Wednesday afternoon, mainly west of RDU. With continued southeast flow through Friday, the early-morning sub-VFR cigs and visbys will likely be a reoccurring theme. Low clouds may scatter out enough during the daytime hours for a return to VFR. Winds will slowly veer through the period ahead of the approaching cold front. Showers and sub-vfr conditions will also be possible ahead of the front, which is expected to move through Central NC on late Saturday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...KC LONG TERM...WSS AVIATION...KC/WP

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