Area Forecast Discussion
Issued by NWS Greer, SC

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424 FXUS62 KGSP 171424 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 924 AM EST Sat Nov 17 2018 .SYNOPSIS... A gradual warming trend will develop over the weekend ahead of a weak cold front approaching from the west. The front will move through the area on Monday through Monday night, with moisture mainly limited to the mountains. A dry, reinforcing cold front will arrive from the northwest on Wednesday. && .NEAR TERM /THROUGH TONIGHT/... 923 AM EST Update... Temperatures slow to rebound from widespread lows in the 20s mountains to 30s piedmont so far this morning. Have adjusted highs today a couple of degrees cooler to match trends/latest guidance with highs today topping out in the 50s to near 60. Any remaining valley fog should burn off in the next couple of hours due to full sunshine. A very nice near-term is in store for the fcst area. Upper level flow remains nearly zonal and benign while a broad area of hipres develops across the mid/Atl and ridges down the east coast. The p/grad will remain loose which will keep winds weak and variable generally ne/ly to se/ly. The latest NAM soundings show dry air thru the column due to compressional warming with no good chance of Cu development nor mlvl moist adv. So...expect mainly sunny skies with passing streams of Ci. With steep inversions trapping llvl moisture...there could be isol fg/fzfg issues this morning across the mtn valleys, Upstate, NC piedmont...especially near larger lakes. However, any fg that does develop shud be shallow and burn off rather quickly after sunrise. Max temps will return to near normal levels in very good insol while mins once again drop below normal in very good rad cooling conds overnight which may lead to another bout of patchy fg arnd daybreak. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 AM EST Saturday: Deep-layer WSW flow will continue over the area on Sunday as weak surface high pressure persists over the region. With southwesterly winds in the surface to 850 mb layer, temperatures will continue to warm back toward climo values. A broad eastern trough will start to carve out on Monday, with associated surface reflections moving northeast along a frontal boundary west of the Appalachians. Temperatures will finally rebound to at or above climo in the continued warm advection. A narrow zone of improving moisture will approach the spine of the southern Appalachians late Monday to warrant isolated to scattered rain shower chances there late Monday afternoon. A leading lobe of upper vorticity will cross the region Monday night as the surface cold front makes a push into and across the region. This boundary will be accompanied mainly by westerly flow and a very narrow zone of slightly deeper moisture. Any nighttime PoPs will probably be confined to the western NC mountains. Post-fropa northwest flow moisture early Tuesday morning may be able to wring out additional light upslope precipitation. Profiles could support a mixover to light freezing rain/drizzle along a few of the highest and colder ridge tops, but ptypes will not be clear cut in this northwest flow scenario where a little instability could also be present. At any rate, wintry precipitation should not pose much of a threat in the higher terrain, and conditions will remain dry east of the mountains through daybreak Tuesday. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 315 AM EST Saturday: A trailing shortwave embedded in the broad eastern trough will pass mainly north of the area on Tuesday. Cold advection will kick in, but with some downslope warming, especially over Upstate SC where maxes should remain in the lower 60s. Wednesday will be the last day of good model agreement, with deep- layer NW flow atop the area as heights begin to fall over the southern plains. Dry surface high pressure will set up over the Appalachians and then likely migrate to a more favorable damming location over the northeast by Thursday. Temperatures will be one to two categories cooler in the resulting thickness trough. The GFS brings a southern stream wave eastward across the Gulf Coast states on Thursday, while the ECWMF develops shortwave ridging from the Appalachians westward. The discrepancies deepen on Friday as the GFS maintains more zonal flow and the ECM camp features very prominent height falls across the MS River Valley. Forecast confidence will thus remain low for the late week holiday period. There should at least be increasing clouds through Friday with a southeasterly fetch likely bringing shallow Atlantic moisture back to the Blue Ridge. In a slight nod to the ECMWF/NAEFS mean, will feature Friday light rain PoPs in the slight chance range for now. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: Surface hipres will continue to build across the mid/Atl this morning and maintain a broad p/grad across all TAF locations. A dry day will be on tap with no good chance of Cu or mid/cloud development...mainly passing FEW/SCT Ci. Winds will remain quite weak and VRB at times with a general ne/ly to se/ly direction as the sfc high centers north of the area. Good rad cooling overnight could lead to fg/br development at KCLT and most other TAF sites by daybreak which will burn off by 13z/14z. A good coating of frost is likely across all TAF sites this morning as frost points have been reached at most locales. Outlook: Gradually increasing potential for late night/early morning mountain valley fog and near area lakes beginning early next week. Otherwise, expect mostly VFR. Confidence Table... 14-20Z 20-02Z 02-08Z 08-12Z KCLT High 100% High 100% High 100% Med 75% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 100% High 100% High 93% KHKY High 100% High 100% High 100% Med 75% KGMU High 100% High 100% High 100% High 93% KAND High 100% High 100% High 100% Med 75% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...HG NEAR TERM...Munroe/SBK SHORT TERM...HG LONG TERM...HG AVIATION...SBK is the U.S. government's official web portal to all federal, state and local government web resources and services.