Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 231843 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 240 PM EDT Thu Mar 23 2017 .SYNOPSIS... Continental polar high pressure will continue to modify over the srn Middle Atlantic states through tonight. A warm front will retreat north across the region on Fri, as the high drifts east toward Bermuda. && .NEAR TERM /THROUGH TONIGHT/... As of 1110 AM Thursday... Little adjustment required to the near term forecast. An area of high pressure at the surface and aloft will maintain relatively cool and dry conditions across central NC through tonight. After a chilly start to the day, with early morning temperatures in the upper 20s-lower 30s, temperatures this afternoon should recover into the low-mid 50s north and upper 50s south. Aside from a few passing thin cirrus, skies will remain sunny. ~WSS The surface ridge will continue to extend across NC tonight. Associated calm to light ESEly surface winds, combined with a mainly clear sky, aside from continued occasional thin cirrus, will favor strong radiational cooling and a light freeze away from urban centers. Low temperatures in the upper 20s to middle 30s. ~MWS && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... As of 355 AM Thursday... Surface high pressure will drift to near and just north of Bermuda; and associated return flow across the sern U.S. will allow a warm front to retreat north through central NC during the day Fri. Both temperatures and moisture will consequently be on the increase, with highs in the mid-upper 60s N and NW, to lower 70s in the S, and surface dewpoints in 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 mid-upper level ridging aloft. Not as cool Fri night, though with decent radiational cooling potential as the Bermuda surface ridge continues to extend west into NC. Patchy radiation fog may result, with low temperatures in the middle 40s to around 50 degrees. && .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 /18Z THURSDAY THROUGH TUESDAY/... As of 125 PM Thursday... High probability that VFR conditions will occur across central NC through 00Z Saturday. The exception will be the potential for a few patches of MVFR visibility due to fog in sections of the southern Piedmont, the Sandhills, and the southern coastal plain, between 10Z- 12Z Friday. The area of high pressure which has provided the VFR conditions will drift offshore Friday. The return sly flow will begin to advect a warm moist air mass into central NC. The arrival of this air mass will lead to higher chances for early morning fog or low stratus Saturday morning and Sunday morning. An approaching low pressure system will increase the threat for scattered showers Sunday through Tuesday. With the moist air mass in place, there will be periods of IFR/MVFR ceilings during this same period. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...WSS/MWS SHORT TERM...MWS LONG TERM...Hartfield AVIATION...WSS

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