Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240801 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 400 AM EDT Fri Mar 24 2017 .SYNOPSIS... A warm front will lift north across NC and VA today. Bermuda high pressure will then extend across our region through early next week, though interrupted briefly by the passage of a shortwave trough on Sunday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 345 AM Friday... 1036 mb high pressure now centered a few hundred miles east of the DelMarVA will drift to near and just north of Bermuda today. Return Sly flow around the wrn periphery of the ridge will cause warmer and more moist air to flood north through the Carolinas and VA today, with afternoon temperatures in the upper 60s NW to lower 70s elsewhere in central NC, and surface dewpoints rising into the 40s to near 50 degrees. The increasing low level moisture values, and broad WAA regime, will favor a scattering of flat/fair weather cumulus trapped beneath a subsidence inversion that will have become established courtesy of an amplified longwave ridge now building east toward the Appalachians. Not as cool tonight, and with a chance of patchy radiation fog owing to the aforementioned increase in low level moisture values, with low temperatures mostly in the upper 40s (45-50) expected.
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
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As of 355 AM Friday... A mid-upper level trough axis extending south from a closed low now over sern CO will migrate newd from the MS Valley early Sat to near the srn Appalachians by Sun morning, as the parent upper low lifts toward the Great Lakes. Associated mid level height falls on the order of 20-30 meters will pivot NEwd across central and wrn NC Sat and Sat night, but lingering influence of the preceding ridge axis aloft/sub-tropical ridge will maintain a strong capping inversion and dry air aloft. As such, precipitation chances will remain low through Sat night, with perhaps just a slight chance of a shower near the Yadkin River by 12Z Sun. Even then and there, however, instability will be weak, shallow, and still capped by the inversion, so the (relatively) better chances of any showers will not occur until Sunday. It will otherwise be warm Sat, with scattered to broken fair weather cumulus, and mild Sat night with both thickening high level cloudiness in Swly flow aloft, and a chance of stratus over the wrn piedmont late. Highs in the lower to middle 70s, and lows in the lower to middle 50s.
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&& .LONG TERM /Saturday through Thursday/... As of 240 PM Thursday... High confidence in warm weather through the early part of next week, with bouts of showery weather, primarily on Sunday and Tuesday. Uncertainty grows midweek and beyond as differences emerge regarding their handling of polar low deepening over SE Canada and the adjacent NW Atlantic waters, however it appears certain that the wavy active southern stream pattern will persist through next week. Sat/Sat night: The potent mid level low will cross the central Miss Valley as its southward-extending trough takes on a negative tilt over the Mid South and Gulf States, leading to strengthening mid level flow from the SW into the Carolinas. PW will remain elevated, in the 75th percentile, with a light onshore-directed southeasterly flow drawing in increasing low level moisture. We should see considerable morning stratus and fog, particularly over the western half of the CWA where low level moist upglide will be deepest, and these clouds should lift to scattered to broken stratocumulus (more clouds west than east) with heating, and these should persist through the day, topped with high thin clouds. Very dry/stable mid levels will keep the day mostly dry, apart from possible patchy morning drizzle in the western Piedmont. Thicknesses will continue to trend above normal, supporting highs of 70-76 NW to SE. The mid level low tracks slowly from MO to IL Sat night, bringing the negatively tilted trough axis and its DPVA into the western Carolinas. This southerly steering flow will drive up PW to nearly 200% of normal just to our west and into the far NW Piedmont late Sat night, in tandem with the arrival of 25-35 kt low level jetting into the Srn Appalachians. Will bring in good chance pops very late Sat night into the far W CWA. Lows Sat night mainly in the mid 50s. Sun/Sun night: The mid level low will quickly weaken and fill as it approaches Lower MI Sun, while the trailing trough axis pivots northeastward through our area. The best precip chances (likely to categorical) will track ENE through central NC (especially NW) Sun morning into early afternoon beneath a band of enhanced upper divergence, with PW rising further to 250% of normal as steering flow becomes southwesterly. Despite the moist column, the dwindling dynamic forcing for ascent as this system tracks NE through the Mid Atlantic region will lead to a tapering down of precip chances through Sun, especially over our SE sections, as the core of the peak integrated water vapor transport shifts to our NNE. Only low chances are expected Sun night as the dampening mid level trough axis shifts to our NE with gently rising heights aloft, within a continued very moist column. Expect highs of 70-78 followed by lows in the upper 50s with overnight stratus developing. Mon-Tue: Monday will feature just patchy light precip at most over much of central NC as a mid level ridge axis shifts overhead with a weak cap at 925 mb and dry mid-upper levels, although higher PW settling over eastern NC and higher surface dewpoints may prompt greater convection coverage over our SE. Our next mid level trough in this active pattern will push through the eastern third of the CONUS Mon night through Tue, accompanied by a surface cold front. Important model differences start to emerge, with the GFS slower and more amplified than the weaker/faster ECMWF. Will lean toward the more progressive ECMWF given this active pattern, but confidence is not high. Will maintain good chance of showers and storms Mon night through Tue. Highs 75-80 Mon/Tue with thickness over 35 m above normal. Lows in the upper 50s. Wed-Thu: Model details differ, but in general, heights will rise over the Southeast in the wake of the departing trough, as another powerful and deep low tracks over the Southwest states. Expect dry weather and cooler temps, still near or just above seasonal normals, as surface high pressure builds in from the north. -GIH && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... As of 220 AM Friday... A lingering continental (dry) air mass, deposited by strong high pressure now drifting off the NC/VA coast, will result in continued VFR conditions through the TAF period. Surface winds, in return flow around the surface high, will become Sly to SSWly and increase into the 8-13 kt range, strongest and with at least occasional gusts into the upper teens kts at nrn TAF sites. A warm front and influx of low level moisture will result in the development of a scattering of flat cumulus, with bases around 4 k ft, today. Outlook: Patchy MVFR-IFR visibility restrictions in radiation fog will be possible early Sat morning. Associated moisture may then produce a few hour period of scattered to broken MVFR range cumulus with diurnal heating mid-morning to midday Sat, especially at Piedmont sites. Late night-early morning fog and/or stratus, then MVFR range cloudiness as that moist layer is heated through midday each day, will be possible through early next week. Otherwise, a chance of showers and storms and sub-VFR conditions mainly at Piedmont TAF sites will exist Sun, then again forecast area-wide on Tue. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...MWS LONG TERM...Hartfield AVIATION...MWS

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