Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221713 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1213 PM EST Wed Nov 22 2017 .SYNOPSIS... A weak area of low pressure off the NC coast this morning will accelerate northeastward off the Mid-Atlantic today. Meanwhile, a cold front will move through the area later this morning. Cool high pressure will build over the area tonight through Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 957 AM Wednesday... Subsidence in the wake of exiting shortwave disturbance, aided further by post-frontal dry air advection, will allow for abrupt clearing of cloud cover this morning, with NWLY wind gusts into the teens at times during the late morning and into the afternoon. Seasonable highs this afternoon in the upper 50s NW to mid 60s SE. While continued CAA will largely govern min temps tonight, re- intensification of a 80-90 kt upper jet streak across the Carolinas this evening and overnight, owing to the approach of the next batch of southern stream energy lifting NE out of the Gulf of Mexico, will result in a resurgence of high-level moisture/cirrus cloud cover, very likely sufficiently opaque to temper radiational cooling. Lows in the lower to mid 30s. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 350 AM Wednesday... WV imagery this morning indicates a shortwave trough in nw flow aloft has amplified strongly across ern TX and into the nwrn GOM during the past 12 hours; and the latest model guidance suggests it will continue to amplify deep into the cntl GOM by 12Z Thu. Meanwhile, a shear vorticity maxima now migrating through swrn Canada, atop a highly amplified wrn conus ridge, will amplify sewd and into the mid MS Valley and mid-South through the same time. The former feature is the one the models had indicated would lift newd and yield a chance of rain across the sern US --including sern NC-- on Thanksgiving Day. Given how deep into the GOM this trough is forecast to plunge, it now stands little to no chance of gaining enough latitude to produce any impacts in cntl NC this period, aside from cirrus/cirrostratus in swly high level flow downstream of the trough. At the surface, a 1032 mb, arctic surface high centered over the upr MS valley this morning will weaken and modify considerably as it migrates ewd to the cntl Appalachians and middle Atlantic states by Thu-Thu night, while low pressure drifts slowly newd through the ern GOM, and renewed coastal frontogenesis occurs downstream of the low/off the sern US coast. Sensible weather resulting from the pattern described above should accordingly be mainly a temperature forecast, impacted very minimally by the aforementioned high level moisture forecast to stream across mainly the ern half of the RAH CWFA - highs in the upr 40s to mid 50s, and lows within a few degrees either side of the freezing mark. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 400 AM Wednesday... Little change in forecast rationale this period. The large scale pattern is forecast to begin a period of transition from a stable, highly amplified one across the conus, consisting of a persistent mean ridge centered near Baja CA and a longwave trough over the ern US, to a more progressive one that will allow for the ridge to expand ewd across the sern US by the middle of next week. At the surface, high pressure will generally dominate the weather over NC, though with a coastal frontal zone and embedded waves of low pressure passing close enough to threaten perhaps the far srn/ern Coastal Plain with a slight chance of rain Fri-Sat. Otherwise, a reinforcing and moisture-starved, nrn stream cold front will sweep across NC Sat night-Sun, only to usher additional surface ridging overhead for next week. Like the pattern aloft, temperatures will be in a continued state of transition, climbing well into the 60s ahead of the aforementioned dry cold front by Sat, will post-frontal 50s Sun-Mon, then modifying back into the 60s for most by the middle of the week. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 1213 PM Wednesday... A cold front has exited the area, with drying and clearing skies in its wake other than some lingering cirrus moving across from the southwest. Aside from the cirrus, VFR conditions will continue through the 24 hour TAF period. Gusty N/NW sfc winds (with gusts up to 20 kt) will continue through the rest of the daytime, then diminish to 10kt or less after sunset. Expect predominately VFR conditions through Monday. The exception could be near the far eastern zones Friday assoc with another coastal system, and a very brief period of sub-VFR late Saturday assoc with the next fast-moving cold front. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...CBL SHORT TERM...MWS LONG TERM...MWS AVIATION...np

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