textproduct: Greenville-Spartanburg

SYNOPSIS

A cold air wedge pattern will persist over the western Carolinas and northeast Georgia keeping temperatures chilly through Wednesday. Widespread moderate to heavy rain will return on Wednesday. Conditions gradually dry out by late week with temperatures trending warmer for the weekend, although still below normal.

NEAR TERM /THROUGH WEDNESDAY/

As of 125 PM EDT Tuesday: CAD will remain firmly entrenched across the area through tonight and much of the day Wednesday. Isentropic lift has weakened, so the widespread rain has diminished; however, spotty rain and drizzle will continue through the evening with weak lift remaining in place. Isentropic and synoptic lift begin increasing overnight into the day Wednesday as an upper low and associated cold front approach from the west. Upper divergence increases as well as the right entrance region of an upper jet max moves into the area. Precip should start out as rain an drizzle then transition to showers with the deep moisture and forcing moving in. Unless the CAD erodes more quickly then expected, which seems unlikely given the pattern, thunderstorms are not expected with no surface based instability developing. That said, pockets of heavy rainfall are expected, especially along and near the Blue Ridge. Can't rule out some ponding of water or bankfull stream levels given the previous days rainfall, but these should be isolated in nature, if they do develop, in light of the overall previously dry pattern. Gusty winds will continue through the period but should remain below advisory levels. Lows tonight will be near normal. Highs will be 10 to 20 degrees below normal, with the coldest temps in the heart of the wedge.

SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/

As of 1230 PM EDT Tuesday: As we move into the short term Wednesday evening, the parent CAD high will have moved well northeast and no longer in a favorable position for damming, though a residual cool pool will remain in place up against the eastern slopes of the Appalachians. Strong upper low will be pushing across the TN valley, with occluded surface low pushing a front through the Deep South. Warm frontal precip enhanced by continued isentropic and orographic uplift will continue across the area, but as the night progresses, the cold front will sweep across the area, eroding the damming. CAA behind the front will drop temperatures a couple of degrees across most of the area compared with tonight, except for portions of the NW NC Piedmont. NW flow will linger across the mountains during the day on Thursday, but downsloping will counteract the CAA and as is typical after CAD erosion, temperatures on Thursday should be 5-8 or so degrees warmer than Wednesday for all but the highest elevations. Very interesting pattern as the mid-latitude cyclone and especially the surface front is progged by most guidance to phase with Melissa at it moves northeast off the Bahamas.

Colder Thursday night with the post-frontal airmass in place, with lows across most of the Piedmont around 40 and near to just slightly below freezing in the higher elevations. Flow aloft will flatten somewhat but the surface gradient will remain fairly strong, with wind gusts overnight 15-20mph in the Piedmont and would not be surprised to see some gusts approaching 40mph in the higher elevations. The winds may preclude frost formation but will continue to evaluate this in later forecast cycles. A cool but mostly sunny day in store for Friday (except in the TN border counties where NW flow will keep enough upslope moisture for some cloudiness). At the end of the period, another shortwave will be gearing up over the Northern Plains to watch for the extended.

LONG TERM /FRIDAY NIGHT THROUGH MONDAY/

As of 1245 PM EDT Tuesday: The flatter upper pattern at the base of the larger trough will shift out of the SW in response to a potent little upper wave digging down and closing off later in the weekend. In the meantime, surface high pressure in place Friday night will lead to the coldest night of the period; mid to upper 30s in the Piedmont and below freezing again at the peaks. Could see some freezing in some of the mountain valleys if the winds drop off early enough. Will have to evaluate this for frost, keeping in mind that Nov 1 is our frost/freeze cutoff for the mountains and foothills. Additionally, folks spending time outside on Halloween should keep in mind that temperatures will drop off rapidly after sunset Friday night.

Below-normal temperatures will continue into the weekend as the aforementioned trough digs and deepens to our west. The upper low diving into the Lower MS Valley will induce surface cyclogenesis along the northern Gulf Coast. Previous guidance had favored a clipper-like system, but new trends are now showing this deeper cutoff low, with moisture lifting north toward the Southern Appalachians in the SW flow aloft. Pops increase across the mountains late Sunday and for now have kept pops confined to that area and generally slight chance until we get a better handle on the synoptic pattern. Below normal temperatures continue through the end of the period.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

At KCLT and elsewhere: Precip and associated vsby restrictions have become more spotty, but expect some MVFR vsby with the spotty rain and drizzle this afternoon. Generally MVFR cigs but TEMPO IFR or low VFR also possible. Conditions deteriorate overnight as precip moves back in and the CAD pattern continues. Have cigs dropping through MVFR to IFR with vsby dropping back to MVFR. PROB30s for LIFR cigs and IFR vsby in precip. Expect prevailing SHRA with MVFR vsby and IFR to LIFR cigs from mid-morning through the end of the period as a cold front approaches from the west. Gusty NE wind continues through the period for all but KAVL where light and variable wind becomes S to SE from around daybreak through the end of the period.

Outlook: Widespread showers, associated restrictions, and gusty winds continue Wednesday afternoon as a cold front moves into the area. Conditions improve behind the front, although gusts may linger on Thursday, and continue into the weekend.

CLIMATE

RECORDS FOR 10-28

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 81 2023 41 1910 62 1984 23 1914 1940 1918 KCLT 87 1940 49 1976 67 1919 26 2001 KGSP 85 1991 51 1976 66 1919 27 1914 1903

RECORDS FOR 10-29

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 82 2020 32 1910 59 1984 21 1976 KCLT 83 2023 48 1925 67 1984 27 2001 2020 1910 1976 KGSP 84 2016 47 1925 66 1984 25 1976 1927

GSP WATCHES/WARNINGS/ADVISORIES

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