Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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963 FXUS62 KRAH 231928 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 328 PM EDT Mon Oct 23 2017 .SYNOPSIS...
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A potent upper level trough and accompanying surface front will surge through the region this evening. A secondary dry cold front will follow and cross our region Tuesday night. Cool high pressure will be in control mid to late week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 328 PM Monday... ...Tornado Watch through 9 PM for the Western Piedmont... ...Slight risk of severe storms late this afternoon and evening... Current conditions... Radar indicated the line of convection was surging ENE across the NC Mountains and upstate SC, with Warnings already being issued over western NC and SC. The initial Tornado Watch has been issued for the western zones through 900 PM, with additional Watches likely to the north and east. This is a traditional high shear, low CAPE environment, with a low level boundary retreating northward through the NW Piedmont and Foothills (where an In-Situ CAD developed today). The approaching mid/upper trough has become strongly negatively tilted over the TN Valley with a parent low moving north through the Ohio Valley. The trailing cold front was surging over the Appalachians, with a meso-low and QLCS already pushing through the GSP area. The developing severe threat... The extensive cloudiness and showers over the western Piedmont will keep things more stable, lessing the severe threat over that region by a category (more marginal than a slight risk for the Triad Region may be more appropriate). However, along and east of the In-Situ wedge there will be more instability - especially from Raleigh and Southern Pines eastward where some sun will send temperatures well into the 70s (even some lower 80s SE). 500 to 1000 J/KG CAPES are expected by mid to late afternoon. TOR parameters are favorable in the western/southern Piedmont (especially from Charlotte and Statesville east to near Fayetteville. The current QLCS and meso-low upstream was racing NE and will be affecting our western counties in the current Tornado Watch beginning around 4-5 PM. This QLCS should continue to strengthen as it moves into the more unstable environment over central NC late afternoon and evening. The previous timing still looks to be on target. We expect the line to reach the Triad and southern Piedmont between 4 and 5 PM, then the Triangle and Fayetteville areas around dinner time, and the Interstate 95 corridor by mid to late evening. A 3-4 hour period of significant weather is expected as the lines of storms push through. The line itself should be accompanied by a few damaging wind gusts and possibly isolated tornadoes. A few supercell storms may develop out ahead of the line main line with the threat of damaging wind gusts and isolated tornadoes. Minor urban or small stream flooding will be possible during the height of the event, with 2+ inch per hour rainfall rates generally lasting 30 to 45 minutes at any given spot. Very dry antecedent conditions and the quick movement of the system overall should keep the flash flood threat low. Clearing behind the convective line, with the passage of the cold front, will spread west to east overnight. However, the latest models have introduced higher PROBS of the development of low stratus again between 4 and 8 am, with some patchy dense fog possible around sunrise as well. This is due to the surface winds becoming light or even calm very late tonight in the very moist near surface environment. Lows have been raised into the 50s NW to 60s down east.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
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As of 325 PM Monday... After low stratus early Tuesday, skies are expected to become partly sunny. Highs will be cooler, 60s NW to 70s SE. A secondary cold front will bring even drier and cooler air Tuesday night through Thursday. Still, readings are expected to remain above the critical threshold of a killing frost or freeze, even in the areas that fall into the mid to upper 30s (rural Piedmont).
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&& .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 210 PM Monday... Cooler and dry weather continues into the latter half of the week with highs in the upper 50s to mid 60s Thursday and near 70 degrees for the end of the week. Lows will remain in the 40s for the majority of the week and then climb back into the upper 40s to lower 50s for the weekend. The next chance for rain comes from a frontal system that will move through the area next weekend. There is uncertainty with regards to timing and also the evolution of a low pressure system riding up the southeast coastline prior to the arrival of the cold front that could cause a chance of precipitation earlier in the weekend. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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As of 325 PM Monday... An approaching frontal system will then result in the ewd progression of a band of IFR-MVFR ceilings, heavy showers and isolated storms with strong and gusty sly to sswly winds --including some severe with isolated tornadoes and straight line wind gusts to 50 kts-- between 22Z/23rd and 05Z/24th. SE surface winds will be strong and gusty ahead of the expected cold front. West to east clearing will occur with the passage of the associated cold front this evening-early tonight, followed by lessening winds and lingering low level moisture late tonight resulting in the development of low IFR stratus and MVFR fog between 08-123/24th. Outlook: VFR conditions are anticipated 15z Tuesday through Friday.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Badgett SHORT TERM...Badgett LONG TERM...Franklin AVIATION...Badgett

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