Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 300735 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 335 AM EDT Fri Sep 30 2016 .SYNOPSIS... A dry southwest flow of air will linger across the region through this weekend. Progressively warmer temperatures are on tap through early next week. The path of tropical cyclone Matthew will be closely watched as it tracks north near the Atlantic coast next week. && .NEAR TERM /THROUGH TONIGHT/... Occasional convection continues to fire in the warm sector and move N/NE early this morning, mainly near and east of the I-77 corridor. Some of the cells have been quite strong and/or heavy rain producers. This activity has been supported by a mid-upper level speed max digging into the base of the trough extending from upper low centered over the Ohio Valley. There`s been enough of an eastward component to cell motion that training hasn`t been much of an issue, yet. The latest mesoscale guidance suggests some semblance of convective coverage will persist through daybreak. In fact, the latest HRRR depicts an uptick in coverage around 12Z. Pops have been increased to solid chance along much of the I-77 corridor through sunrise. We aren`t expecting a whole lot out of this activity, but will certainly need to watch for the training potential, especially in the urban corridor along I-77. The aforementioned speed max is expected to lower heights enough such that the frontal boundary should finally nudge east of the forecast area by early afternoon, spreading much drier air into the NC Piedmont and northern foothills. Thus, deep convection in the near term is expected to peak around daybreak, then diminish through the morning, with nothing expected this afternoon. Some of the mesoscale and short term guidance tries to develop some ridge top convection this afternoon, but forecast soundings look positively hostile to convective development, so we`re not buying it. Max temps are expected to be (finally) right around normal, except along the I-77 corridor, where maxes of a category or so above climo are still expected. With the dry air mass in place, all areas are expected to see around to a little below climo min temps tonight. && .SHORT TERM /SATURDAY THROUGH MONDAY/... At 240 AM Friday: GFS and ECMWF indicate that the center of a H5 closed low will lift north across the Great Lakes region this weekend. The mid level pattern across the region will likely feature a Bermuda High and a trof from the Ohio River valley south to the Mississippi Delta. Short range guidance shows that a dry slot associated with the Great Lakes low will rotate across the western Carolinas. This pattern should result in dry conditions and high temperatures ranging from the mid 70s within the mtn valleys to the low 80s east. On Monday, it appears that an asymmetrical mid-level omega block will develop over the northern CONUS, with the ridge axis over the Mid West and Great Lakes. TC Matthew is expected to be tracking north near the eastern tip of Cuba by late Monday. Sensible weather across the CWA will remain unchanged from the dry weekend. High temperature are forecast to warm a degree or two over values reached on Sunday. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... As of 250 AM Friday: The path of TC Matthew will gain most of the attention through the extended period. Both the GFS and ECMWF indicate that Matthew will track north, tracking parallel along the Atlantic coast from FL to NC. To the west, the northern tip of a H5 ridge will reach the southern Appalachians, sourced from a high over Mexico. To the north, another deep low is expected to organize across the nrn plains. The pattern does not appear to be supportive of heavy rainfall across the CWA, developing ahead or west of Matthews track. I will keep the forecast generally dry from Tuesday through Thursday. Temperatures are forecast to remain between 3 to 5 degrees above normal. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... At KCLT and KHKY, surface front remains virtually stalled just west of the terminals early this morning, with plenty of low level moisture in place. This creates the very real potential for another round of fog and/or low stratus this morning. In fact, KCLT was already reporting a low MVFR cigs at issuance time, and there`s plenty of IFR cigs not too far away. Meanwhile, SHRA were near the KCLT airfield at 0530Z (tempo`d through 07Z), and this may result in mixing out the lower cigs, at least for a little while. Based upon observational trends, as well as signals from the guidance, there`s enough confidence to add a mention of IFR cigs at both terminals later this morning, but enough uncertainty exists such that these conditions will be handled largely with tempos. The front is expected to finally punch through by late morning, so improvement to VFR should be rapid, with VFR conditions persisting through the end of the period. Elsewhere: It`s now looking doubtful that earlier forecast restrictions will materialize at KAVL. An up-valley wind of 5-10 kts is expected to persist, which should keep temp/dewpoint spreads around or above 5 degrees. Suppose a brief IFR cig still cannot be ruled out (and this is hinted at in the forecast with a tempo for FEW008/SCT020), but all restrictions have been removed from the forecast. With drier air lingering behind frontal boundary, all sites are forecast to see VFR conditions persist for the next 24 hours. Outlook: VFR conditions expected in most places through the beginning of next week as dry high pressure settles in over the area. Confidence Table... 07-13Z 13-19Z 19-01Z 01-06Z KCLT Low 55% High 93% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 85% High 99% High 100% High 100% KHKY Med 70% High 92% 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... GA...None. NC...None. SC...None. && $$ SYNOPSIS...NED NEAR TERM...JDL SHORT TERM...NED LONG TERM...NED AVIATION...JDL

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