Scientific Forecaster Discussion

Area forecast discussion National Weather Service Greenville-Spartanburg SC 718 PM EDT Friday may 22 2015 Synopsis... dry Canadian high pressure will linger atop the region through the Holiday weekend. A southerly flow of moisture around Bermuda high pressure will gradually return next week. && Near term /through Saturday/... as of 715 PM...the forecast remains on track. I will update to adjust hrly temperatures through tonight. Overall...tonight should be calm...dry...and passing bands of thin high clouds. As of 5 PM...nice conditions across the region provide little reason to update the forecast. Recent satellite images and view out the windows indicated a patch of cirrus/wave clouds across the NC/SC state line across the foothills and Piedmont. I will update the forecast to indicate that cloud cover may remain for a couple of hours. Minor edits made to hourly temperature and dewpoints late this afternoon. As of 200 PM EDT Friday...an approaching upper ridge axis will allow heights to continually rise through the period. A surface ridge sliding through the Northern Ohio valley region will continue to advect east tonight...through the day on Saturday allowing for a weak back door reinforcing front to push into northeast Georgia and the western Carolinas. Thus...the entire forecast remains dry with below normal temperatures and light gradually veering winds highlighting the period. Expecting clear skies to prevail overnight tonight leading to abundant radiational cooling...therefore temperatures were populated from a consensus of raw guidance which was 3-5 degrees cooler than mosguide. Expecting lows tonight in the upper 40s to lower 50s over the lower terrain...while some values in the Lower/Middle 30s are expected over the higher elevations. Highs on Saturday will be slightly warmer than today...however still approx 3- 5 degrees below climatology with dewpoints in the 40s supporting low humidity levels. && Short term /Saturday night through Monday/... as of 210 PM Friday...dry weather will continue on Sunday as upper ridge axis continues to build atop the southeast Continental U.S.. low level flow around Bermuda hipres will steadily advect higher temperatures and dewpoints into the southern Appalachians. Maximums will be a few degree f warmer than Saturday topping out a bit above climatology. The upper pattern evolves slowly on Monday with the ridge axis sharpening. It is debatable how just far west it/S suppressive effects linger through sunset but the steady increase in low level moisture leads the model consensus to favor at least isolated diurnal deep convection in and/or near the high terrain. Temperatures are slated to continue to rise 2-3 degree f above Sunday/S readings. && Long term /Monday night through Friday/... as of 215 PM Friday...the medium range continues to look Summer-like with an upper ridge/anticyclone holding along the southeast coast and a Bermuda high at the surface providing a generally moist flow from the Gulf/Atlantic at low levels. This will favor above normal temperatures and mainly diurnal showers and storms each day. There is some discrepancy in the models on Thursday...for what it is Worth...in terms of the timing and strength of a short wave moving across the Midwest/Ohio Valley. This feature could push a weak boundary into the area on Wednesday evening or Thursday which would enhance precipitation chances mainly over the mountains...hence the likely pop over parts of the mountains both days. Chances may go down a bit for Friday if that boundary actually moves through. The chances for severe thunderstorms each day look minimal at this point because of poor lapse rates and relatively weak instability with middle level warm air. && Aviation /23z Friday through Wednesday/... at kclt and elsewhere...the center of a dry airmass will pass over the Appalachians tonight...reaching the western Atlantic by Saturday afternoon. MOS and near term models indicate only VFR conditions through the period across the western Carolinas. I will indicate winds generally 5 kts or less...generally calm tonight...with east-southeast winds developing by Sat afternoon. Outlook...high pressure will remain over the region through the weekend...then shift east early next week...allowing moisture to gradually return out of the south. Conditions should remain generally fair through the period. Confidence table... 23-05z 05-11z 11-17z 17-18z 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: (must be lower case) Www.Weather.Gov/gsp/aviation_tables && Gsp watches/warnings/advisories... Georgia...none. NC...none. SC...none. && $$ Synopsis...csh near term...Ned short term...csh long term...PM aviation...Ned

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