Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221144 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 645 AM EST Tue Jan 22 2019 .SYNOPSIS... Arctic high pressure overhead this morning will drift offshore later today. This will allow a slightly warmer air mass to overspread the region. An approaching storm system will bring unsettled weather to central NC Wednesday into Thursday. Drier and colder weather anticipated for the end of the week. && .NEAR TERM /TODAY/... As of 325 AM Tuesday... Arctic high pressure will extend overhead today, maintaining a cold and dry air mass over central NC. The abnormally dry air is noted in the sfc dewpoints which vary early this morning from the single digits across the north, and between 10 and 15 above across the south. Aside from patchy cirrus floating overhead, skies will be mostly clear. With the sfc high in our proximity, expect winds to be lighter compared to the past few days, mainly light from the east- northeast. With many locations starting out in the middle teens, a diurnal temperature recovery of 20-25 degrees will yield afternoon high temperatures in the upper 30s to lower 40s. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... As of 325 AM Tuesday... ...Light ice accrual possible overnight across the NW Piedmont... The center of the Arctic high will drift offshore tonight, though a sfc extension of the high will extend back into central NC. A return sely flow at the sfc will aid in modest moisture advection into central NC. Sfc dewpoints in the teens at sunset will slowly recover into the 20s, and possibly into the lower 30s across the Sandhills and southern Coastal Plain. A few thousand feet above the surface, sly flow will strengthen in response to the area of high pressure offshore and a s/w crossing the southern Plains. this will result in increasing isentropic upglide, especially after 06Z. Moistening in the 925mb-700mb layer coupled with isentropic upglide/lift should generate patchy light precip overnight in vicinity of the Yadkin/Pee Dee River Valley. With sfc dewpoints in the 20s, and dry bulb temps near or slightly below freezing across the NW Piedmont (and initially across the southern Piedmont), expect spotty light freezing rain or freezing drizzle to occur. This freezing precip, though light, may persistent long enough across portions of the NW Piedmont to result in a trace of ice on elevated surfaces such as bridges/overpasses. This probability appears highest in the 09Z (4AM) to 14Z (9 AM) time frame. Plan to issue a winter weather advisory for the NW Piedmont counties of Guilford, Forsyth and Davidson from midnight to 10 AM. There is the potential that the advisory may need to be expanded a little farther to the south and east, if it appears that precip will start sooner or is more extensive. While not anticipating widespread travel problems, the random nature of the precip will play havoc with early morning commuters as slick spots expected to be random, catching motorists offguard. As the s/w progresses east into the lower MS Valley Wednesday, strengthening sly flow over the SE U.S. will induce a coastal trough/warm front to advance northwestward into central NC. This feature will create a wide disparity in temperatures as portions of the Sandhills and Coastal Plain will warm into the low-mid 60s. Meanwhile patchy light precip across the NW Piedmont will likely initiate an in-situ or hybrid cold air damming, keeping temperatures in this region in the 30s for most of the morning, recovering into the mid-upper 40s by late afternoon. Due to the random nature of the expected rain coverage, will have PoPs no higher than chance or low end likely. Expected precip amounts will be light, totaling no more than a few hundredths throughout the day. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY NIGHT/... As of 235 AM Tuesday... Wednesday Night and Thursday: The lingering wedge airmass will likely be eroded by midnight Thursday and temperatures are expected to increase through the overnight hours as the front approaches from the west. As such, the "morning" low will likely occur around midnight, mid 40s NW to around 60 degrees SE. The deep southwesterly flow will pump the warm moist air into the region, with increasing temperatures and precipitation chances from west to east through Thursday morning. Despite the precipitation, temperatures will top out around 50 degrees NW to mid 60s SE. The parent surface low is expected to move through the Great Lakes and into Canada before the front pushes into the region. However, a secondary low, strengthened by a developing shortwave aloft, will develop along the front over the southern Appalachians/northern Gulf Coast. The surface low will lift northeast along the mountains and eastward through the Carolinas/Virginia through Thursday morning. The cold front will likely move through central NC Thursday aft/eve, resulting in both an end to precipitation and decreasing temperatures behind it. As a result, temperatures may actually fall through the evening. Largely expect the front to be through the area by midnight Friday. Overnight lows in the upper 20s NW to low 30s SE. Friday through Monday night: Expect a return of cooler, drier weather in the wake of the cold front, with highs in the 40s on Friday and Saturday. Lows Friday night in the generally in the mid 20s, increasing slightly for Saturday night, upper 20s to around 30 degrees. Forecast confidence decreases significantly beyond Sunday. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... As of 645 AM Tuesday... There is a high probability that VFR parameters will occur across central NC through 06Z Wednesday. Sfc winds will slowly veer from a northeasterly direction this morning to an east-southeast direction this evening, then sly by early Wednesday. A developing low level jet will bring a threat for low level wind shear conditions to the region early Wednesday morning. Ceilings are expected to lower after 06Z Wednesday with IFR/LIFR ceilings probable across the Piedmont and Sandhills prior to 12Z Wed. Spotty light precip expected to develop and with sfc temperatures below freezing, patchy light freezing rain/freezing drizzle possible in vicinity of the Triad terminals between 08Z-14Z. Rain is expected to expand in coverage and intensity Wednesday night into Thursday morning as a frontal system approaches and crosses the region. Improving weather conditions expected late Thursday with VFR parameters expected Thursday night into Saturday. && .RAH WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from midnight tonight to 10 AM EST Wednesday for NCZ021-022-038. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...KC AVIATION...WSS

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