460 FXUS62 KRAH 231602 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1100 AM EST Wed Jan 23 2019 .SYNOPSIS... An approaching storm system will bring unsettled weather to central NC today into Thursday. Drier and colder weather will arrive for the end of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 1100 AM Wednesday... Not many changes needed for the mid morning update. Near freezing air temperatures remain in place across the Triad region as of 11am on Wednesday with light rain/drizzle falling. While icing is becoming less of a concern with time thanks to rising dewpoint and air temps, a few localized spots remain at freezing, which could provide for some slick spots through mid day. Elsewhere, the low to mid level clouds are becoming more broken in nature and the warm front continues to push inland. Winter Weather Advisory will be allowed to expire at 12 noon. Previous Valid Discussion... Main forecast challenges today revolves around the extent of freezing precipitation that is expected through mid morning, and the expected temperature field late this afternoon. Later today, a coastal warm front will lift slowly northwestward across central NC in response to the approach of a s/w and attendant sfc cold front. This sfc feature will likely bisect our region SW-NE by early-mid afternoon, creating a 20-25 degree temperature spread, ranging from the low-mid 40s in the NW Piedmont to the low-mid 60s over the southern Coastal Plain. Expect shower coverage to remain scattered as isentropic upglide along this sfc feature should concentrate most of the showers north-northwest of this boundary. Tonight, the approach of the s/w will aid to strengthen the low level sly flow over central NC, leading to breezy and mild conditions. The low level jet will result in strong kinematics with effective bulk shear in the neighborhood of 50-70kts, supportive of banded convection. Similar to the event that occurred last Saturday night, expect a band of heavy showers to occur ahead of the sfc front. Lack of sfc based instability should inhibit showers from developing into thunderstorms. However, the strength of the wind just a couple thousand feet off of the surface should produce gusts 40-45kts at the sfc where the heavier showers occur. This threat appears greatest overnight into early Thu morning. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 340 AM Wednesday... Band of heavy showers accompanied by strong gusty winds will be crossing the eastern counties at the start of the day while showers will be decreasing in coverage across the west. A cold front will propel eastward across the region during the morning, with rapid clearing anticipated in the wake of the front. Temperatures will fall through the morning hours than stabilize mid day through mid afternoon before cooling off late in the day. Dewpoints, which will start out well into the 50s to lower 60s, will lower into the 30s by mid day in the NW, and range from the 20s NW to near 40 SE by the end of the day. The cooler drier air mass will continue to overspread central NC Thursday night. Under clear skies and light winds, overnight temperatures will drop into the 20s NW, and near freezing across the SE. && .LONG TERM /FRIDAY THROUGH TUESDAY NIGHT/... As of 225 AM Wednesday... Expect a return of cooler, drier weather in the wake of the cold front. Surface high pressure will slowly migrate eastward over the region through Saturday. Aloft, the eastern US will be under the influence of a broad upper level trough through the weekend. A series of weak upper level shortwaves will swing through the VA's, however do not expect any precipitation over central NC with any of them at this time. Highs on Friday and Saturday will generally range from low 40s NW to around 50 degrees SE while overnight lows will moderate a bit from mid 20s Friday night to upper 20s/Low 30s Saturday night. The gradual moderation in temperatures is expected to continue through the weekend. Highs in the mid 40s to low 50s Sunday and lows Sunday night in the low to mid 30s. A surface trough will develop to the west and build eastward over the Appalachians and NC Piedmont Sunday through and Monday. Warm southwesterly flow will again set up Monday night as the next frontal system over the Midwest approaches the Mid-Atlantic. The upper level trough will shift off to the northeast, resulting in a return to southwesterly flow aloft as the next upper level trough amplifies over the Rockies/Plains. Forecast confidence decreases significantly with the next frontal system, which is expected to move through the region sometime Tue/Wed. Low confidence in precip chances and amounts, however expect the moderation in temperatures to continue ahead of the front with a sharp drop in temperatures behind it (regardless of whether or not precipitation accompanies it). && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... As of 640 AM Wednesday... Widespread low end MVFR/IFR ceilings with pockets of LIFR will occur through 00Z Thu across central NC. In addition, patchy light precipitation will lift northeastward over portions of the Piedmont this morning. Where sfc temperatures are at or slightly below freezing, light freezing rain or freezing drizzle will occur, producing a thin glaze on the cold surfaces. This freezing precipitation threat appears highest in vicinity of the Triad terminals through 14Z. A strengthening low level jet will lead to low level wind shear conditions across most of central NC after 15Z, likely persisting into this evening. Winds at 2000ft will be sly between 40-50kts. The approach of a storm system later today will lead to an increase in shower coverage west-to-east across the region this evening into the overnight. In vicinity of the heavier showers, anticipate visibilities as low as 1-2SM and sfc wind gusts near 40kts. A cold front will cross central NC Thursday morning, bring an end to the widespread showers, and veering sfc winds from the SW to the NW. This NW flow will advect a drier more stable air mass into central NC, leading to clearing skies NW-SE late Thursday morning through early Thursday afternoon. VFR parameters expected across central NC Thursday afternoon into the weekend. The exception will be a small threat for high end MVFR ceilings in vicinity of the Triad Fri morning with the passage of a mid level shortwave, and again Sunday as another s/w approaches from the west. && .RAH WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until noon EST today for NCZ021-022-038. && $$ SYNOPSIS...WSS NEAR TERM...JJM/WSS SHORT TERM...WSS LONG TERM...KC AVIATION...WSS