Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 160103 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 803 PM EST Sun Jan 15 2017 .SYNOPSIS... High pressure positioned over the northern Mid Atlantic will nose down into North Carolina tonight, persisting over the region through Monday night. A cold front will approach from the west Tuesday. && .NEAR TERM /THROUGH TONIGHT/... As of 310 PM Sunday... Partly-mostly cloudy skies will become overcast by mid-late evening with patches of light rain probable over the western Piedmont. This patchy light rain in response to weak isentropic upglide initiated by the approach of a mid level s/w. This lift expected to be maximized during the overnight hours over the Piedmont, mainly centered in vicinity of the Triad. A parent sfc high (1030mb) positioned over the northern Mid-Atlantic will nose southward into eastern NC. The return flow over the cool stable air mass at the surface coupled with the patches of light rain will aid to initiate another cold air damming episode overnight. Min temps should vary from the upper 30s northeast to the low-mid 40s southwest. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 310 PM Sunday... Monday, ongoing CAD will maintain a low overcast deck through the morning, with patchy light rain and/or drizzle possible across the northern counties. Temperatures will be slow to recover, especially across the north half. An end to the spotty light precip and a gradually lifting of the ceilings will allow temps to rebound into the lower 50s across the south and the mid-upper 40s across the north. If ceilings lift sooner or dissipate, potential for afternoon temperatures to be 5-6 degrees warmer, primarily across the south. Monday night, expect variable cloudy skies to persist while another weak perturbation will approach from the west. This feature may trigger a patch or two of light rain and/or drizzle, mainly over the western Piedmont. Min temps in the low-mid 40s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 220 PM Sunday... Models continue to come into better agreement with the overall pattern through Friday. There are still small timing issues and differences in precip chances/timing over central NC. Generally, expect multiple rounds of wet weather with dry periods in between. Timing and amounts are still a challenge. The weather could get very interesting for late next weekend and early the following week. Tuesday through Wednesday Night: The wedge will probably linger through early Tuesday, however the models erode it by the aft/eve as the return flow from the high offshore and the southerly flow ahead of the approaching front both increase. Meanwhile aloft, the remnants of a closed low over the Baja gets absorbed into the northern stream as a shortwave that swings through the Great Lakes through and into the Mid-Atlantic Wednesday/Wednesday night. The wave should be strong enough to dampen/suppress the ridge. The surface low and attendant front will approach the area Tuesday night, swinging through by late aft/eve Wednesday. As a result, expect best chances for rain to be late Tuesday through Wednesday from west to east. Temperatures will be above normal, slightly cooler in the NW Tuesday (mid to upper 50s), but otherwise expect highs in the 60s and lows in the mid 50s Tuesday night. With the expected frontal passage late Wednesday, overnight lows will be lower, mid 40s north to around 50 degrees south. Thursday through Friday Night: There is surprising agreement between the models for this period, though there are some differences, the pattern is similar. Expect two additional rounds of precipitation during this time, with a period of dry weather in between. A fleeting surface high and upper level ridge will move through/build over the area Thursday while another low moves out of the desert southwest northeast toward the Great Lakes. The moisture advection into the Gulf coast states Thursday night combined with the sufficient forcing from the low will result in another round of rain moving into the Carolinas from the southwest Friday/Friday Night. Temperatures should be fairly steady during this time, highs in the upper 50s to mid 60s and lows in the 40s. Saturday and Sunday: This part of the forecast period gets quite interesting and the model agreement make it even more ominous. Although, this far out it is hard to jump on board completely. Fingers crossed for some changes. As of the latest model runs, a strong low will come onshore in the Pacific NW Friday/Friday night digging a trough south and east toward TX Saturday and Sunday. In the wake of the low that moves through Central NC Friday night, a ridge builds aloft over the southeast U.S. while the surface low strengthens over the Midwest. Very strong southerly flow advects very warm moist air into the Gulf Coast states late in the weekend. There is a bit of uncertainty whether a CAD wedge will set up and hold over NC or not and thus temperatures are low confidence, but do expect increasing chances for rain late Sunday into early in the week. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... AS OF 800 PM Saturday... 24-hr TAF Period: Ceilings should deteriorate between midnight- sunrise at all terminals, to MVFR at RDU/FAY/RWI and IFR/LIFR at INT/GSO. Sub-VFR ceilings are expected to prevail through the day at most terminals Monday, esp INT/GSO where IFR conditions may persist through the afternoon, as a warm/moist airmass aloft advects atop a cold/shallow airmass advecting into the region from the NE, and a cold air damming wedge develops across the N/NW Piedmont. Expect light NE/ENE winds to veer to the E at ~5kt overnight, then become light/variable during the day Monday. Looking Ahead: Conditions may briefly improve on Tue as the CAD wedge weakens in response to strengthening southerly flow in advance of a cold front approaching from the west, before deteriorating Tue night into Wed as low ceilings/rain overspread the region along/ ahead of the cold front, which is expected to cross central NC Wed afternoon. VFR Conditions will return to all terminals in the wake of the cold front Wed night and Thursday. -Vincent && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...KC AVIATION...Vincent

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