Scientific Forecaster Discussion

Area forecast discussion National Weather Service Greenville-Spartanburg SC 307 am EDT Thursday Apr 24 2014 Synopsis... high pressure will move off the eastern Seaboard today through tonight as a cold front and upper level disturbance approach from the west. The cold front will cross the area on Friday...with dry high pressure returning through the weekend. A wet and possibly stormy pattern will set up Monday through Wednesday. && Near term /through tonight/... as of 300 am...dry high pressure will slide east of the area today...allowing flow to turn out of the south today. Meanwhile...a fast-moving trough and associated low pressure system will cross the middle MS valley...then enter the tenn valley tonight. Models in good agreement on another sunny day with above normal temperatures. There will be some recovery of dewpoints and lighter winds...so not expecting as high of fire danger as yesterday. High res models generally agree that organized convection associated with the approaching cold front will make a run a the NC mountains overnight. The storms look to take on a linear Mode...but lose steam as they cross eastern tenn during the wee morning hours. The day 1 convective outlook from Storm Prediction Center does show a slight risk to our west...with general thunder risk from central Tennessee to the NC mountains I will keep some probability of precipitation creeping into the western zones late tonight...with the expected arrival of at least weakened showers to the smokies before daybreak Friday. Otherwise...expect an increase in clouds...and temperatures only dropping into the 50s most places. && Short term /Friday through Sunday/... as of 300 am EDT Thursday...a deamplifying but coherent middle level shortwave trough will move quickly east through the western Carolinas on Friday. Decaying convection may be in place across the mountains as the period begins Friday morning...but additional shower and thunderstorm development is likely across the foothills and Piedmont through middle afternoon prior to frontal passage. The best instability should line up over southeast Piedmont sections Friday afternoon...with 0 to 3 km bulk shear values around 30 knots. This might be just enough for thunderstorm organization...but probably not enough for a significant severe weather threat. Scattered showers may linger across the western mountains into early Friday evening in brief moist upslope flow. Upper level ridging will then build over the eastern Continental U.S. And strengthen through the weekend. There seems to be slightly better consensus on an approaching back door cold front stalling north of the region over Virginia through Sunday. Despite the weak frontal passage on Friday...maxes will be higher Sat and Sunday in better insolation. && Long term /Sunday night through Wednesday/... as of 300 am EDT Thursday...a deep low pressure system over the Central Plains by the end of the weekend will gradually fill as it wobbles eastward toward the Midwest Monday through Wednesday. The downstream ridge axis will move to the eastern Seaboard Sunday night...with heights falling through the remainder of the long term period. Gradually building SW flow and bands of moisture and lift ejecting eastward from the deep vortex will be hard to time through the period. The best moisture and upper support should lean toward the Tuesday through Wednesday period as a better upper jet structure east of the closed system will likely be in place near the Appalachians. Periods of heavy rain will be possible at some point...probably Tuesday or Wednesday...but that timing cannot be pinned down yet. Expect slightly above normal temperatures on Monday...near climatology Tuesday...and lower than normal maxes by Wednesday. && Aviation /07z Thursday through Monday/... kclt and elsewhere...VFR conditions expected through the period. A north-S axis of dry high pressure will shift east of the area today...causing the winds to veer from NE overnight to southeast by midday. Winds should remain fairly light...generally under 10 kts. Other than occasional filaments of cirrus...it should be sky clear through this afternoon. A cold front will enter the Ohio/tenn valley tonight...with increasing middle and high clouds toward the end of the taf period. Outlook...a cold front with potential for showers/thunderstorms is expected to cross the region Friday. Then dry high pressure returns Saturday through Sunday. Confidence table... 07-13z 13-19z 19-01z 01-07z 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 98% 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: (must be lower case) Www.Weather.Gov/gsp/aviation_tables && Gsp watches/warnings/advisories... Georgia...none. NC...none. SC...none. && $$ Synopsis...hg near term...Arkansas short term...hg long term...hg aviation...Arkansas

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