Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 141518 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1020 AM EST Tue Nov 14 2017 .SYNOPSIS... An upper level disturbance will move across the Carolinas today. Strong surface high pressure will otherwise build across the eastern US through Wed, then weaken with the passage of another upper level disturbance Wed night. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1020 AM Tuesday... Little change required to the near term forecast. A narrow layer of moisture beneath a strong mid level subsidence inversion will maintain a thin deck of stratocu through this afternoon. In addition, a mid level s/w will cross our region through mid-afternoon, providing additional lift to maintain the deck of clouds. Since the moisture layer is rather shallow, there will be periods of at least partial sun. 12Z upper air analysis depicts central NC in the axis of a 850mb thermal trough. the low level nely flow will maintain weak cold air advection. This caa will cause instances of gustiness with gusts 13- 18 mph probable. Thus, due to the periods of cloudiness and cold air advection, temperatures will only warm 5-7 degrees from current levels. High temperatures should vary from the low-mid 50s north to the mid-upper 50s south. ~WSS Clearing behind the shortwave trough will favor good to excellent radiational cooling conditions tonight, except for perhaps over the far nwrn Piedmont where model forecast soundings indicate at least scattered stratocumulus may linger, with low temperatures in the lower to middle 30s. ~MWS
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 355 AM Tuesday... Shortwave ridging will initially extend across the sern US (and NC) Wed, but with renewed trough amplification across the Great Lakes and middle Atlantic states late Wed and Wed night. Associated glancing height falls in cntl NC, on the order of 20-40 meters at 500 mb, and an associated mid level moist axis, will consequently sweep across cntl NC Wed night. At the surface, initially strong surface high pressure will consequently weaken over the ern US, with coastal frontogenesis and cyclogenesis offshore the srn middle Atlantic coast, expected to occur downstream of the upper trough Wed and Wed night. Partly sunny conditions will favor high temperatures solidly in the middle to upper 50s Wed, Overnight lows, driven early by radiational cooling, but then followed by a leveling off or near steady temperatures courtesy of both some light swly stirring and the passing mid level cloudiness, are expected to be within a few degrees either side of 40 degrees. While some virga may result from the mid cloudiness, the moist layer should prove much too shallow, and sub-cloud layer much too dry, to support any precipitation at the surface. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 350 AM Tuesday... A shortwave moving across the northern Great Lakes will nudge a dry cold front southeast across the area early Thursday, with the frontal passage quickly followed by surface high pressure digging southeast out of the midwest across the mid Atlantic and offshore Friday night. Cool air will be slow building down the coast, and highs on Thursday will have time to reach the low and mid 60s, with cool air advection surging Thursday night to produce mins mostly in the mid 30s. Then, under sunny skies, highs Friday will struggle into the mid and upper 50s. With the high moving offshore, we`ll see a quick warmup and increasing moisture on Saturday in the short-lived return flow regime. Cloudiness will be increasing during the day with highs recovering into the 60s. There is a good bit of disparity in the timing of our next cold front which will be approaching the mountains on Saturday, but we could see showers in the western Piedmont as early as mid day, although PoP chances will favor Saturday night and Sunday to cover the window of uncertainty in the frontal passage. Strong low level jetting ahead of the front will provide for strong, but brief, moisture advection ahead of low level convergence. So, will be watching for future model consensus to nail down this expected window of enhanced shower coverage. Cold air advection should be ongoing on Sunday, with highs in the low to mid 50s, followed by mins tumbling to freezing or below under clear skies Monday morning. Highs Monday will be our coolest of the period, with highs struggling into the upper 40s across the north to lower 50s south. Dry weather will continue and a modest bump in highs are expected as low amplitude short wave ridging transitions across the area on Tuesday. Highs will be mostly in the mid 50s. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... As of 655 AM Tuesday... Multiple layers of stratocumulus, trapped below a couple of capping inversions in the lowest 5 thousand ft, will percolate over cntl NC through the forecast period. Although resultant ceilings are expected to remain around --and more likely just above-- MVFR/3000 ft, an occasional occurrence of MVFR ceilings cannot be ruled out throughout cntl NC today, with the relative highest probability at RWI and FAY this afternoon. Nely surface winds may also occasionally gust into the teens kts this afternoon, mainly at ern sites. Outlook: There is a low to medium chance of an MVFR ceiling at RWI Wed afternoon, on the west side of an area low pressure forecast to form and track along the srn middle Atlantic coast. The passage of a frontal system on Sat or Sun will result in a chance of showers and sub-VFR conditions. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...WSS/MWS SHORT TERM...MWS LONG TERM...mlm AVIATION...MWS

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