Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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314 FXUS62 KRAH 221118 AFDRAH AREA FORECAST DISCUSSION National Weather Service Raleigh NC 620 AM EST Wed Jan 22 2020 .SYNOPSIS... High pressure will extend through central North Carolina from the north and northeast through Thursday. A strong, slow moving storm system will approach from the west late Thursday, then cross the region Thursday night through Saturday morning. High pressure will build in from the southwest late Saturday through Sunday. && .NEAR TERM /TODAY THROUGH TONIGHT/... As of 220 AM Wednesday... Another quiet and cool day is likely, although it won`t be as chilly as yesterday given the modification of the surface ridge extending in from the N. The strong mid level low which dove over the Southeast states yesterday now sits over the NE FL coast and is projected to steadily fill as it tracks SE then E out over the Atlantic. Amplified shortwave ridging rearward of this low will build overhead from the W today, ensuring a continued dry and subsiding column within below normal PW. Thicknesses will have rebounded today from yesterday`s readings with the air mass modification and reduced CAA, and while they`re still projected to be 20-25 m below normal, the plentiful sunshine should help offset these readings, supporting highs in the mid 40s to around 50, 5-8 degrees F below normal. The column will remain dry and stable tonight, but high clouds will spread in from the west overnight ahead of the incoming amplifying/phasing mid level shortwave trough moving through the Great Plains. There are also signs that we could see some low cloudiness working into the eastern Coastal Plain and eastern Sandhills late tonight, as the low level flow at 1000-2500 AGL / 280-285K takes on an easterly component and draws low level Atlantic moisture into the area within the stable surface-based depth. Confidence in this is not high, though, as not all models agree on this occurrence, so will keep just partly cloudy skies at most in the extreme E and SE CWA late tonight. Expect temps to be a few degrees higher than this morning`s temps, especially in the E where dewpoints will be fastest to recover. Lows in the mid-upper 20s with some lower 20s in some rural Piedmont locations. -GIH && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 245 AM Wednesday... The mid level trough will continue to amplify as it heads E and closes off a low over the Mid Miss Valley by daybreak Fri. Preceding high clouds spreading into NC will thicken and lower into the mid levels, while in the lower levels, as the ridge heads further out over the N Atlantic and weakens, the increasing and deepening E and SE flow will draw greater moisture and clouds into central NC, especially Thu evening/night. The deepest forcing for ascent with the approaching trough will hold to our W through Thu night, with the greatest mid level height falls and upper divergence holding back over the Mid South, but the increasing PW to above normal values and a shot of weak DPVA swinging out of the mean trough supports bringing in slight chance pops in the far W CWA overnight. Expect highs from the upper 40s to lower 50s Thu, with the rebounding thicknesses balancing the increased cloud cover. Lows in the 30s. -GIH && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 330 AM Wednesday... An upper level low located over the Mid MS valley Friday morning is forecast to track east, along the Mason-Dixon Line, and is progged to reach the Mid-Atlantic Coast by Saturday night. As the associated sfc low follows a similar track, models are in good agreement that a secondary, triple point low will develop INVOF of the western Carolinas Friday afternoon and will move north through the area Friday evening, before reaching the DELMARVA coast by daybreak Saturday. Strengthening isentropic lift and overrunning will lead to increasing rain chances across the western Piedmont Friday morning and then into the central Piedmont and the Sandhills by the afternoon, with the early onset of precip across NC Piedmont helping to set the stage for a strong CAD event on Friday. The strongest forcing and heaviest rain arrives during the late afternoon and evening as the occluded front and triple point low move north through the area. Models indicate that the true mT air will remain off the SE Coast( dewpoint recovery limited to the 50s across interior NC). This will set up a classic high shear/low CAPE environment, with very weak surface based instability of only MLCAPE of 100 to 200 J/KG expected to preclude a threat of severe storms across the area at this time. The front and forcing looks to exit north and east of the area between 06 to 09z Saturday, ending rain chances SW to NE across the area. Rainfall amounts are expected to range from 0.25 to 0.50" across the eastern half of the forecast area, to 0.50 to 1.0" across western portions. As previously mentioned, a strong CAD across the NC Piedmont on Friday will result in a sharp NW to SE temperature gradient across the area; highs ranging from lower 40s NW Piedmont to lower 60s across the coastal plain zones. Partial clearing and CAA in the wake of the cold front late Friday night will drive overnight lows; lows ranging from mid 30s NW to mid 40s east. Upper troughiness will persist across the area Saturday through early next week, resulting in some periodic cloudiness, but generally dry conditions. A modified cP parent high will build slowly east, resulting in seasonable temps through the period. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... As of 620 AM Wednesday... High confidence in continued VFR conditions well into tonight. High pressure continues to extend over central NC from the NNE today into tonight, with dry air at multiple levels and ridging aloft keeping clouds at bay, although we may start to see high clouds moving in from the west after midnight tonight, thickening as they spread E and lowering into the mid levels toward morning. In addition, patchy low level moisture streaming inland from low pressure off the Southeast coast may bring a few MVFR clouds into the SE Coastal Plain including FAY toward daybreak, but confidence in this is not high. Winds will hold mostly under 10 kts from the NNE or NE. Looking beyond 12z Thu, the storm system moving in from the W/SW will bring increasing chances for sub-VFR conditions starting Thu night, with rain chances peaking Fri afternoon/Fri night, highest at Triad terminals. Low cigs may linger into Sat morning, but otherwise fair skies and VFR conditions are expected Sat/Sun. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...CBL AVIATION...Hartfield

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