textproduct: Greenville-Spartanburg

SYNOPSIS

A warm and increasingly moist air mass will remain in place over our region through Saturday. Rain chances will be highest over the mountains as low pressure tries to organize to the west of our area. Drier but mild high pressure will arrive on Sunday and persist into early next week. A cold front will cross the the area in the middle of the week, ushering in much cooler temperatures behind it.

NEAR TERM /THROUGH SATURDAY/

As of noon Fri: Broad upper ridge centered over the eastern Gulf and south Atlantic Coast today. Nebulous forcing persists through the afternoon and evening over our CWA, with weak warm front or baroclinic zone remaining north of the area across KY/VA, north of the ridge. Said front is associated with a cyclone, now in the central Plains, which will advance across the mid-MS Valley tonight, inducing secondary cyclogenesis in the Mid-Atlantic by morning. A modest cold front should be pulled across the Carolinas/Georgia late Saturday or Saturday night in turn.

500mb vort axis, a wave preceding the aforementioned cyclone, now seen on vapor imagery over eastern KY/TN, set to track across the CWA as it dampens out this afternoon. Max temp potential looks to be limited by the midlevel cloud cover lingering over the northern CWA, but most of the Piedmont still makes it into the 70s (a few degrees shy of records). A modest amount of SBCAPE is shown to develop this afternoon, with prog soundings most supportive for deep convection over the mountains. However, as a reflection of the nebulous forcing, CAMs certainly are not excited and depict paltry coverage. 20-40% PoPs are forecast over much of the northwest half of the area through early evening. PWATs decline a bit for a time this afternoon but increase tonight as cold front approaches from the west. 850-700mb WAA also picks up, with some elevated instability above the associated inversion. Hence all areas receive at least a chance range PoP between about midnight and 5 AM; a small chance of thunder is forecast in the SW NC mountains and portions of the CWA southeast of I-85 overnight. Chances decline east of the mountains by daybreak, as the moisture band shifts east, but continue to increase along the TN border thru the morning due to upslope westerly flow, before tapering off.

Gusty SW winds will develop Saturday as clouds scatter, and with the further aid of downsloping aloft temps should reach the upper 70s in the Piedmont. Still forecasting a record high for CLT and GSP although AVL still falls short Some showers could redevelop east of the mountains during peak heating although dry mid to upper levels likely would weaken deep updrafts. Fast 700-500mb flow will persist aloft and 0-6km shear is accordingly impressive at 50-60 kt. The surface front arrives past peak heating, and the dry air aloft is a limiting factor, so severe threat looks rather low, but can't completely rule out the ingredients coming together for strong storms producing a straight-line wind and/or hail threat in our eastern CWA in the mid to late afternoon.

SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/

As of 1143 AM EST Friday...

Key Messages:

1) Clear and quiet weather in store for Sunday and Monday.

2) Above-normal temperatures expected to persist.

3) Next system approaches from the west by late Monday.

Quiet weather on tap for the short term...as z500 troughing slides to our east Saturday night...and ushers in somewhat clearer skies overnight. Some lingering mid/upper level moisture may persist into the first part of Sunday, especially in mountain valleys. By mid-day Sunday, however, a reinforcing shortwave axis will cross the western Carolinas and scour out any remaining moisture...leaving us dry and clear through Sunday night and into Monday. Highs will creep back toward normal, but the air mass pushing into the area Sunday will already be well-modified by the time it reaches us, so highs will remain above normal...just not as far above normal as they have been.

Upstream, the latter half of the weekend will see a complex split flow pattern develop over the western CONUS. An upper low initially located over the Four Corners region of the American Southwest will open up into the mean flow by early Monday, but should quickly be replaced by a new disturbance dipping down out of west-central Canada. The result will be cyclogenesis in the lee of the Colorado/New Mexico Rockies, but generally slow eastward progress of this low. By Monday evening, some upper-level moisture may return to the Carolinas - so perhaps expect some cirrus. But, the deeper moisture and associated active weather will remain well to our west through the end of the period.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

As of 1201 PM EST Friday: Significant timing differences among long-range ensembles continue to plague a forecaster trying to gauge what approaching low pressure will do mid-week. The bulk of operational guidance depicts an upper low deepening over the central Great Plains on Tuesday, then pivoting eastward into the Great Lakes and upper Ohio Valley, and steering an associated cold front across Tennessee by Tuesday evening. LREF membership generally supports this timing. The question becomes how quickly the front will push east of our CWA. The GFS and its ensembles tend to favor a slower progression, where the upper low lifts northward and the front only slowly meanders into the eastern Carolinas by Wednesday night. The ECMWF and GDPS, and at least the majority of their ensembles, depict a much faster progression as a consequence of a more open-wave-like upper pattern that maintains good steering flow farther south.

Slower solutions would maintain some degree of synoptic forcing with the frontal circulation well into Wednesday...and although ongoing rain would likely inhibit good destabilization, some sample forecast profiles from these solutions do support at least weak surface-based CAPE Wednesday afternoon...which could allow some embedded thunder. The bigger imapct, however, still appears to be rainfall...with areas west of I-26 potentially receiving up to an inch of rain...or even more in isolated spots across the Smokies and Balsams. By all accounts, we need this rain, and given dry antecedent conditions, we don't expect widespread hydro issues unless QPF response increases a good bit.

Behind the front, a cooler, drier air mass should settle into the area. Temperatures will trend back toward normal, and it should finally start to feel like late November. By Thursday and Friday, highs will only climb into the mid-50s, and lows will drop below freezing even across the low terrian. Brrr!

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: SW winds will pick up overnight ahead of an approaching cold front. This should keep fog from forming. However, KHKY will be sheltered from the flow and could see some fog and/or LIFR stratus for much of or at least part of the night. Scattered light showers will push across the area, but remain low enough in coverage to keep PROB30 for -SHRA in all the TAFs. During or after -SHRA, MVFR to IFR cigs could form and linger thru daybreak. Winds remain SW and become gusty across the Upstate. Wind toggles to NW at KCLT and other NC sites in the aftn, but not till late aftn or early evening in the Upstate. Skies should scatter out to VFR by midday. Isolated SHRA or TSRA could develop near KCLT after 18z Sat as well, but chance still too low to mention.

Outlook: Drier conditions return early next week, although there will remain some potential for mountain valley fog/low stratus each morning.

CLIMATE

RECORDS FOR 11-21

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 76 1994 24 1937 60 1931 11 1914 KCLT 78 1942 38 1937 64 1991 19 1914 1879 KGSP 78 1942 38 1914 64 1991 17 1914

RECORDS FOR 11-22

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 74 1940 32 1937 57 1934 15 2008 1937 KCLT 76 2011 38 1929 65 1883 13 2008 KGSP 77 2011 38 1937 58 1953 18 1914

GSP WATCHES/WARNINGS/ADVISORIES

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