Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 231635 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1140 AM EST Tue Jan 23 2018 .SYNOPSIS... A cold front will exit central NC early this afternoon. An area of high pressure and attendant seasonably cool air mass will build into and settle over the region Wednesday and Thursday. && .NEAR TERM /THIS AFTERNOON/... As of 1140 AM Tuesday... have made adjustments to the hourly temperatures based on observed trend and expectation of warming prior to the passage of the 850mb trough. Appears that most of central NC will reach the 70 degree plateau with lower 70s probable over the eastern half of central NC. still expect strong gusty winds through early afternoon. Have seen a few reports of gusts close to 40 mph. 1040 AM discussion... Any adjustment to the near term forecast was to dwindle the PoP chances across the east and increase the sfc wind gusts through early afternoon. Scattered-numerous showers exiting the northern coastal plain at 15Z along a pre-frontal trough. Based on sfc dewpoints and wind field, the sfc cold front is just entering the western Piedmont. At the initial onset of the clearing, strong gusty winds are occurring. Recorded wind gusts between 40 and 45 mph have occurred in the Triad region. This is supported by the 12Z GSO sounding which depicts 35- 40kts just off the sfc. Expect this batch of strong gusty winds to traverse east through the rest of the morning, reaching the coastal plain counties early this afternoon. Modest convergence along the sfc front will likely produce a band of low topped showers over the east half of central NC through 18Z. SW sfc flow behind the sfc front will advect a drier more stable air mass as dewpoints drop into the 40s across the coastal plain and 30s in the Piedmont. The passage of the 850mb trough will not occur until late in the afternoon. The late initiation of the cold air advection will allow temperatures across the region to soar into the upper 60s and lower 70s, with mid 70s a good possibility over the southern coastal plain and Sandhills. && .SHORT TERM /TONIGHT/... As of 410 AM Tuesday... Mostly CAA-driven lows, though with brief radiational cooling potential over the wrn Piedmont, are expected to dip into the lwr to mid 30s for most. Skies will be mainly clear, aside from srn stream upr jet-induced cirrus that will nose nwd across SC, and into at least srn NC, after midnight. && .LONG TERM /WEDNESDAY THROUGH TUESDAY/... As of 145 AM Tuesday... Wednesday through Saturday: Expect dry weather through Saturday. An upper level shortwave and a reinforcing dry cold frontal passage is expected Wednesday night/Thursday. Surface high pressure is expected to build into the area in the wake of the secondary cold front and remain over the area into Saturday. Meanwhile, the upper level ridge will move eastward over the Carolinas through Friday night. Highs will be generally in the upper 40s north to mid 50s south through Wednesday and Thursday, with moderation beginning Friday. Lows in the upper 20s to low 30s Wednesday and Thursday nights, increasing Friday night. Saturday Night through Tuesday: Another upper level trough and surface cold front will develop over the Midwest and progress eastward toward the Mid-Atlantic over the weekend. As southwesterly flow increases, so will the warm, moist advection into the region. As a result, cloud cover and chances for precipitation will increase late Saturday into Sunday as the cold front approaches. Some differences in the evolution of the upper level trough and the timing and duration of convection as it moves into/through Central NC have developed between the medium-range models. The ECMWF is more amplified, slower, and wetter than the GFS. As a result of the latest forecast cycle model differences, confidence in the timing of the front and convection associated with it is low. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... As of 700 AM Tuesday... Generally MVFR ceilings, with pockets of IFR ones, and MVFR visibility restrictions in showers, will become VFR with the passage of a lead cold front from west to east between 12-14Z at wrn sites and 16-17Z at ern ones. A strong swly low level jet (llj), on the order of 40-50 kts as low as 1500-2000 ft, with progressively stronger winds above that level, will continue to migrate newd across e-cntl and nern NC this morning. The presence of this feature will support the continued newd development and maintenance of the aforementioned ceilings and convection. Since the axis of this llj is departing, low level wind shear should be ending in the next hour or so at RDU/RWI/FAY, if it has not already. The passage of the aforementioned cold front will result first in the redevelopment of scattered to numerous showers along it, then behind it with abrupt clearing, with a veering of surface winds to swly and a similarly abrupt increase into the 15-25 kt range (sustained), with gusts up to 30-35 kts for several hours immediately following the frontal passage. These winds will then lessen and continue to veer to wly or nwly later this afternoon and evening. Outlook: MVFR ceilings will be possible Sat, with showers Sat night, ahead of, and in association with, a weekend frontal system. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...MWS LONG TERM...KC AVIATION...MWS

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