Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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055 FXUS62 KRAH 202035 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 330 PM EST Sat Jan 20 2018 .SYNOPSIS... High pressure will drift across the southeastern United States through tonight, then offshore on Sunday. A cold front will approach from the west Monday, and cross central NC on Tuesday. && .NEAR TERM /THROUGH Sunday/... As of 330 PM Saturday... Current stretch of tranquil weather conditions will continue during the near term. An area of sfc high pressure located over southern Georgia will continue to slowly weaken as it drifts eastward tonight and Sunday. Meanwhile, a compact upper level low pressure system over the north central Gulf early this afternoon will weaken as it slowly lifts east-ne tonight and Sunday. This weather system will spread patchy mid-high level clouds over central NC very late tonight and more notable on Sunday. The moistening of the atmosphere may allow for the development of patchy fog overnight into early Sunday morning, primarily over the Piedmont as warmer air traverses over the cooler ground in the wake of the recent snowpack. Not all models are showing this signal so there is the potential that no fog or low clouds will develop. For now, will advertise visibility no worse than a mile or two at this time. Min temps near 30 to the lower 30s. Expect enough sunshine Sunday afternoon along with a steady swly low level flow to push temperatures into the low-mid 60s. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 330 PM Saturday... May see a better potential for areas of fog late Sunday night into early Monday morning, primarily across the Piedmont, though increasing high cloudiness may inhibit fog development in vicinity of the Yadkin/Pee Dee river valley. Min temps mostly in the mid 30s. Monday, a deep cyclone over central Plains will slowly lift into and across the Great Lakes Monday night and Tuesday. Swly low level flow will continue to pull warm air into the Carolinas. This warm air coupled with ample sunshine will push temperatures well into the 60s along and east of highway 1. Thickening cloud coverage over the west will inhibit sunshine to result in cooler temps, holding the nw Piedmont in the upper 50s to around 60. At this time, expect bulk of the showers to hold off until after sunset, though a stray shower or two cannot be ruled out in vicinity of Winston-Salem by late afternoon. The trailing sfc cold front associated with the deep cyclone will approach from the west Monday evening, and cross our region early Tuesday. Thickening clouds and steady sly flow will likely maintain mild conditions Monday night with some places likely not dropping much below 55 degrees. Better support aloft over the NW Piedmont suggest better shower coverage in this region, with support waning farther to the south and east. Currently not expecting abundant rainfall with this system as forcing not overly impressive. Rainfall totals will likely vary from less than a half inch NW to under a quarter of an inch SE. Morning clouds and scattered showers Tuesday morning will giveway to increasingly sunny skies. 850mb front does not cross region until the afternoon, so we should have time to warm before low level cold air advection commences late in the day. This required an adjustment up in high temperatures Tuesday. Currently expect max temps Tuesday to be in the 60-65 degree range. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 212 PM Saturday... Tuesday night and beyond: Quiet weather with near to above seasonal temperatures are expected into early Saturday. The upper air pattern Tuesday night features a departing short wave trough aloft and cold front. A period of short- lived strong cold advection Tuesday night results in clearing skies and temperatures that fall to near normal in the upper 20s to lower 30s. Weak short-wave ridging develops on Wednesday and temperatures reach he mid to possibly upper 50s. A short-wave trough and an associated cold front with very little moisture swings across the region late Wednesday/early Thursday. Skies will remain mainly clear with limited sensible weather impacts. Ridging aloft with increasing heights build into the area for Thursday into early Saturday. Skies will remain generally clear with moderating temperatures. Highs on Thursday will range in the lower to mid 50s, in the mid to upper 50s on Friday and in the mid 50s to lower 60s on Saturday. A higher amplitude trough that moves onto the Pacific coast on Thursday reaches the central Plains by Saturday night. Deep layer southerly flow transports moisture northward from the Gulf and Pacific as a surface wave develops in the mid-Mississippi Valley. Both the 12Z operational GFS and EC have trended slower with the precipitation arrival in our region, especially with the precipitation spreading northward across GA and the Carolinas as the surface high is slower to depart. Will keep PoPs confined to the Saturday night period for now. -Blaes && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... As of 1255 PM Saturday... There is a high likelihood that VFR parameters will persist across central NC through 03Z Sunday as high pressure to our south maintains good to excellent aviation conditions. Some model members are still suggesting that areas of fog will develop over/in vicinity of the snowpack region overnight with visibilities as low as IFR. Will error on the side of caution and depict similar scenario with MVFR/IFR visibilities overnight through early Sunday morning. Several other model members, however, suggest little if any fog development overnight so this made need adjustments as the time approaches. Otherwise, expect VFR parameters through Monday afternoon, aside from a threat for early morning fog and low clouds across the Piedmont early Monday morning. An approaching cold front will cause ceilings to thicken and lower Monday though VFR ceilings expected through 00Z Tuesday. After 00Z Tuesday, shower coverage will gradual increase west-to-east, along with the threat for MVFR ceilings. Low end VFR/MVFR ceilings are highly probable late Monday night through early Tuesday morning along with scattered rain showers. Aviation conditions are expected to rapidly improve southwest-to-northeast across central NC late Tuesday morning through Tuesday afternoon as the cold front exist the region. VFR parameters will return to the area, and linger into Wednesday and Thursday. While sfc winds will generally be less than 10kts through Monday morning, the approach of the cold front Monday afternoon will cause sfc winds to increase, with sustained sly winds 10-15kts probable late Monday into Monday night and gusts around 25kts. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...BLAES AVIATION...WSS

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