textproduct: Greenville-Spartanburg

SYNOPSIS

A warm air mass remains in place over our region today with decreasing rain chances. Dry but mild high pressure will arrive on Sunday and persist into early next week. A moist cold front will cross the the area in the middle of the week, ushering in much cooler temperatures behind it.

NEAR TERM /THROUGH SUNDAY/

As of 1220 PM EST Saturday...

Key Messages:

1) Well Above Normal Temperatures Stick Around for the Weekend with New Daily Record Highs Possible Today at KGSP and KCLT

2) Spotty Showers Possible this Afternoon, Mainly Along and South of I-85 and Across the NC/TN Border

3) Breezy Winds Linger through Early this Evening

4) Dry Conditions and Cooler Temperatures Return Sunday

Quasi-zonal flow remains in place aloft over the forecast area through late this evening. At the sfc, a mostly dry cold front will track across the area this afternoon and early evening before pushing east late this evening. It will be another warm day with temps expected to run ~15-20 degrees above normal. The warmest temps are expected east of the mountains, where SW flow is in place ahead of the front. Highs east of the mountains will climb into upper 70s to lower 80s, threatening daily record highs at KCLT and KGSP. Highs across the mountains will be similar to yesterday. Not much moisture will be in place ahead of/along the front this afternoon/early evening. 12Z CAMs depict the best activity occurring across the NC/TN border as well as along and south of I-85. Capped PoPs to slight chance for now as activity is expected to be rather anemic. Could not rule out an isolated thunderstorm or two, mainly across the far eastern SC Upstate and southern NC Piedmont during peak heating, but confidence is low. Breezy winds from 15 to 25 mph (well below advisory criteria) are expected through late this afternoon, gradually diminishing by the early evening hours.

Weak upper troughing with an embedded shortwave will then track across the forecast area tonight into early Sunday. Meanwhile, at the sfc, dry high pressure will build in behind the departing front through the end of the period. This will allow cooler temperatures to return Saturday night into Sunday. However, lows will still end up ~12-15 degrees above normal, with highs ~8-12 degrees above normal. Lows tonight will be cooler compared to last night, ranging from the lower to mid 40s in the mountains and the upper 40s to mid 50s east of the mountains. Highs will once again be warmest east of the mountains, ranging from the upper 60s to mid 70s. Highs across the mountains will be cooler, ranging from the upper 50s to mid 60s across lower elevations and the upper 40s to lower 60s across the higher elevations.

SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/

As of 1103 AM EST Saturday...

Key Messages:

1) Clear and dry conditions expected Sunday night and Monday.

2) Increasing cloud cover and rain chances Monday night and Tuesday as a cold front approaches.

Sunday night and Monday will be dominated by dry, low-amplitude ridging aloft, as 1025mb surface high pressure crosses the lower Mid-Atlantic and reaches the NC/VA coastline by Monday evening. The result will be mostly clear skies. Temperatures will be a category or two cooler than this weekend, with highs on Monday in the mid-60s and lows Monday morning in the lower 40s, perhaps even dipping into the 30s briefly along the I-40 corridor.

With high pressure to our east by Monday night, winds should toggle around to the south...actually more like southeast in the latest operational guidance, which points to a brief period of CAD-like weather, featuring weak WAA in the low-levels and an increase in low-level moisture overnight. Model guidance currently indicates this will result mostly in just increasing cloud cover overnight, with precipitation not arriving in earnest until the daylight hours Tuesday...and continuing through the day as a shortwave lifts out of the Mississippi Valley into the Carolinas, and drives a cold front toward us from the west.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

As of 1118 AM EST Saturday...

Key Messages:

1) A cold front brings widespread rain to the area on Wednesday, with some embedded thunder, but no strong concerns for either severe weather or heavy rainfall.

2) A dry and cold air mass settles into the area on Thursday, and keeps temperatures at or below normal through the end of the week.

Tuesday night, the cold front may stall to our west briefly as upper forcing diminishes and flow becomes parallel to the surface boundary. However, additional shortwave energy will already be developing over the upper Great Plains and Midwest, which by early Wednesday should once again steer the front eastward into Wednesday. Confidence is improving regarding timing...enough to say that the front shouldn't clear the area in time to avoid at least a little destabilization on Wednesday afternoon, especially for the eastern zones in the NC Piedmont and eastern SC Upstate. For most of the forecast area, this looks like it would be elevated, posing no risk of severe weather; there remains, however, a chance of a weak surface-based unstable layer developing over those eastern zones, amounting to some 100-200 J/kg sbCAPE there. Having said that, the orientation of the front with the upper flow as well as the presence of ample CIN - more CIN than CAPE, in fact, in some GFS and GDPS soundings - continues to make this an unfavorable setup for high-shear-low-CAPE severe. QPF response, meanwhile, continues to point to some 0.25-0.5" of rain east of I-26, and 0.5-1.0" west of I-26...with locations across the Smokies and Balsams still looking like they could receive >1". Again, though...given dry antecedent conditions, this shouldn't pose much of a hydro threat.

Behind the front, rainfall should vanish, with dry conditions returning by Thursday morning but for some brief lingering NW flow showers/snow across the NC-TN border. The postfrontal air mass settling into the region will be much colder than what we've had the last week or two, with highs on Thursday barely creeping into the mid-50s (versus highs in the upper 60s ahead of the front on Wednesday) and lows in the 20s or lower 30s each night after Thursday. It should stay mostly clear through the end of the period next Saturday, as high pressure dominates the pattern.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: Expect dry, VFR conditions to prevail thru the 00z taf period. The only exception is at KAVL, where they may see intermittent MVFR cigs overnight and into the mor- ning from moist NW flow. This was handled with a TEMPO from 08 to 12z. Nonetheless, cigs could remain above 3000 ft, but my confidence in this scenario is fairly low. Otherwise, winds outside of the mtns will start out WNW/NW and become more N/ NNE later tonight/overnight. They should toggle back to a more NWLY direction Sunday aftn. Both KHKY and KAND could see periods of light and VRB winds thru the taf period. At KAVL, winds will remain NWLY/NLY thru the taf period with speeds between 5 and 10 kts.

Outlook: Expect dry, VFR conditions to continue thru Monday with the potential for mtn valley fog/low stratus each morning. Shower and thunderstorm chances and associated restrictions, return Tues into Wed as a moist cold front moves into our area.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...None. SC...None.