Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 291019 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 619 AM EDT WED JUN 29 2016 .SYNOPSIS... Weak high pressure centered over the Mid West will build over the southern Appalachian region through the late work week. A slow moving cold front is expected to become stationary across the western Carolinas this weekend. The boundary may remain stalled over the region into early next week, before possibly dissipating on Tuesday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 615 AM EDT Wednesday: Current fcst remains on track therefore no significant adjustments were needed/made with this update. Did tweak t/td in the immediate near term to best align with recent ob trends. Previous Discussion: An anomalous upper trof persists across the eastern CONUS this morning while a broad anticyclone rotates atop the Desert Southwest. At the surface, a cold front is slowly advecting southeast through the OH/TN valleys with a sprawling region of high pressure building in its wake over the upper MS valley. Closer to home, Expecting cu development later this morning amongst a modestly destabilizing warm sector ahead of the intruding front, which is progged to move into the NC high terrain by late morning. Said front will likely enhance convergence in the boundary layer and thus promote convective initiation over the mtns/fthills by early afternoon. Profiles over the piedmont will be relatively unstable, generally featuring 1-1.5k j/kg sbcape, while also exhibiting upwards of 30kts 0-6km shear thanks to improved flow aloft. In addition to these profile features, guidance favors a weak shortwave impulse ejecting through the trof base by mid/late afternoon which could provide some synoptic support for deeper convection, mainly along the I40 corridor. Placement of convection is with low confidence thus opted to spread mid/high chance pops across the mtns/fthills by midday, eventually moving east over the NC/SC piedmont as the front intrudes. Wouldn`t be surprised to see a few strong to perhaps an isolated severe storm this afternoon, especially over western NC adjacent to the approaching H5 vortmax. The front itself will likely struggle to clear the area tonight, most likely stalling out atop the region. This will likely yield continued convection thanks to persistent llv convergence in proximity to the boundary, and sustained elevated cape per soundings. Thus, will keep pops in the chance range along the I77/I40 region through midnight before slowly tapering to non mentionable levels by daybreak Thursday. Temperatures today will be a few degrees warmer with high topping out near normal, as well as tonight`s lows.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 155 AM Wednesday, a series of weak short waves move through the long wave trof over the eastern CONUS Thursday and Friday. At the surface, a weak boundary remains stalled just south and east of the area Thursday. A weak wave moves along the front bringing southerly low level flow and moisture back into the area. This leads to increased instability, especially along and east of I-85. An upper jet max moves through as well bringing divergence and some shear. The result will be scattered diurnal convection with the best coverage over the NC Piedmont and SC Eastern Piedmont. Decent DCAPE values develop as well. The combination of features could lead to an increase in severe thunderstorm chances, especially along the I-77 corridor. The surface boundary slides a little farther east and south on Friday. This leads to less low level moisture and only weak instability. Therefore, only isolated diurnal convection is expected. Highs Thursday will be a degree or two below normal and rise to near or a couple of degrees above normal Friday. Lows remain nearly steady a few degrees above normal. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 305 AM Wednesday, the upper trough over the east coast moves east of the area Saturday leaving nearly zonal flow in place across the area through Tuesday. A series of short waves move through the flow and over or near the area each day. At the surface, a frontal boundary drops into the area on Saturday. Scattered mainly diurnal convection will be the result. The front may sag south a little on Sunday, but a wave of low pressure moving along the front keeps the front from moving too far south and keeps low level moisture over the area. Numerous to good chance convective coverage develops during the day and only slowly tapers off overnight. A stronger low pressure center moves into the OH valley Monday bringing the front back north across the area. The guidance shows the potential for an MCS to develop with this wave, but it remains north of the CWFA. Still, we should see at least good chance convective coverage. The front finally begins to dissipate on Tuesday, but yet another wave moving along it keeps enough low level moisture, and the resulting instability, across the area for scattered mainly diurnal convection. Temps will bounce around just either side of normal each day. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
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At KCLT and elsewhere: Vfr through the period with the exception possible mvfr visb restrictions associated with any afternoon tsra. A cold front continues to push into the TN valley this morning. Out ahead, flow remains rather light and vrb, with a few sites light and out of the ssw, all amidst thin high cirrus. Llv lapse rates will increase late in the morning allowing for low vfr cu development ahead of convective initiation along the Blue Ridge. Said convection is progged to propagate into the foothills/piedmont regions warranting tsra tempos at all sites with low vfr cigs and mvfr visbs at all sites with timing based upon latest camguide. Guidance insists the front will likely stall across the region thus leading to possible isolated shra spread about the region overnight, however confidence is too low at this point to include in tafs. Also, given the stalled front, expecting winds along/behind the front to veer nw, mainly at KAVL/KHKY, while all other sites remain out of sw. Outlook: A warm and moist airmass will prevail through weeks end leading to afternoon/evening convection regionwide. Restrictions will be possible adjacent to any shra/tsra, as well as morning fog in the mountain valleys and at locales that experienced recent rainfall. Another front will slide southward towards the area this weekend yielding further increased chance for shra/tsra. Confidence Table... 10-16Z 16-22Z 22-04Z 04-06Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 100% Med 77% High 100% KHKY Med 66% High 100% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the schedule TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link:
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...RWH NEAR TERM...CDG SHORT TERM...RWH LONG TERM...RWH AVIATION...CDG is the U.S. government's official web portal to all federal, state and local government web resources and services.