Scientific Forecaster Discussion

000 fxus62 kgsp 241826 afdgsp Area forecast discussion National Weather Service Greenville-Spartanburg SC 226 PM EDT Wed Apr 24 2019 Synopsis... a disturbance pushing into the region will lead to scattered shower and thunderstorm activity late Thursday into Friday. High pressure over the southeast will support generally quiet weather this weekend into early next week. && Near term /through Thursday/... as of 2pm EDT wednesday: highs today are coming in at or just above levels seen yesterday, as prevalent southeast Continental U.S. Ridge keeps the area in the warmest air so far this year. It may be a couple degrees cooler on Thursday due to some increase in clouds, and some drop in thicknesses as incoming shortwave pushes ridge eastward. Moisture transport ahead of this next system makes some progress on Thursday as dewpoints advance in the morning, but remains shallow. With expected mix-out of bl moisture Thursday afternoon, pwats increase little. Upper system makes more progress Thursday night with rain becoming possible over the mountains near the Tennessee border as dynamical forcing from upper wave comes in, along with an approaching front. Winds are currently fairly light and variable as flow transitions from surface high moving east of the area, to a trough moving in from the west that will increase southwesterly winds this afternoon and Thursday. With mostly clear skies and good afternoon mixing, some wind gusts are possible this afternoon, though 850mb winds are weak today, and gusts are more likely Thursday afternoon as low- level flow picks-up. && Short term /Thursday night through Saturday night/... as of 200 PM Wed: a cutoff low will begin to merge/phase with a northern stream shortwave over the Mississippi Valley Thursday night. Brisk low-level flow will develop ahead of this system, though isentropic charts don't indicate particularly good warm upglide will occur, and winds are relatively veered. An increasing pop still is warranted, especially in the southerly upslope flow areas. The trough will sharpen up a bit as it swings across the southern Appalachians on Friday, and the associated cold front pushes across the County warning forecast area. The timing of the shortwave/fropa is not ideal for convection, with a short time window for destabilization before the front departs; shear and forcing do not suggest much of a severe threat anyway. Friday night, temps will fall slightly below normal as a dry Continental airmass spreads in behind the front. Saturday looks to be a very nice Spring day with abundant sunshine and temps therefore rising slightly above normal. && Long term /Sunday through Tuesday/... as of 200 PM Wed: low pressure moving from the Great Lakes to New England on Sunday will shunt the incumbent dry airmass south of the area. The low however be replaced by another blob of Canadian high pressure, which will drive a cold front in our direction. Most of the global model depictions show the front pushing through without producing qpf, then quickly retreating northward ahead of the next plains system. The 24/00z European model (ecmwf) is currently the only source showing the front stalling just north of the region, though that results in a similarly small impact on our sensible weather. Either way, high pressure remains the dominant feature for most of the medium range. Some diurnal instability will develop, mainly over the mountains, resulting in a small pop focused on the aftn/evening. With the exception of Monday when we will be invof or just behind the front, temps will run a couple categories above normal. && Aviation /19z Wednesday through Monday/... at kclt and elsewhere: good VFR through the period. Winds are still somewhat light and variable, but should become more definitely southwesterly this afternoon as surface flow ahead of incoming system begins to take hold. A few gusts are possible this afternoon due to good deep layer mixing, but 850mb winds are weak enough, that only mentioned this in the taf for and, where 850mb winds are strongest. For kclt, gusts are more likely Thursday afternoon after 18z as 850mb flow improves during another day of good mixing. Some clouds above 10kft this afternoon increase in coverage overnight as incoming system begins to affect the area. Any precipitation with the next system will hold-off until Friday at the taf sites. Low- levels remain dry enough to keep fog out of tafs for at least another day. Outlook: periods of showers and thunderstorms associated with a cold front bring the potential for restrictions Friday. VFR returns for the weekend into Monday as high pressure builds in behind the cold front. Confidence table... 18-24z 00-06z 06-12z 12-18z kclt high 100% high 100% high 100% high 100% kgsp high 100% high 100% high 100% high 100% kavl high 100% high 100% high 100% high 100% khky high 100% 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 scheduled taf issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: Www.Weather.Gov/gsp/aviation && Gsp watches/warnings/advisories... Georgia...none. NC...none. SC...none. && $$ Synopsis...Munroe/SW

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