textproduct: Greenville-Spartanburg

SYNOPSIS

A warm front will lift northeast through the area today, bringing an unseasonably warm air mass to the region, along with small rain chances to the mountains. Mostly dry and very warm conditions are expected during the Christmas holiday through the weekend. A cold front may bring much colder weather early next week.

NEAR TERM /THROUGH TONIGHT/

As of 1230 AM EST Tuesday: Upper flow will amplify thru the near term, with ridging over the Plains and a trough diving into the Northeast. So, the overall flow over the region will veer from SWLY to NWLY in the low-levels, and WLY to NWLY in the mid and upper levels. A stratocu deck has spread over most of the forecast area and will start to scatter out later this morning east of the mountains, as downslope flow kicks in. In the meantime, spotty light radar echos can be seen on the radar mosaic within this cloud deck, and the CAMs agree on this light precip spreading over the area thru early morning. The sub-cloud layer remains very dry, and moisture aloft is shallow. So only a few spotty sprinkles can be expected, if anything manages to reach the ground. The exception will be near the TN border, where moisture will be aided by mechanical lift to squeeze out a few isolated showers. Temps are basically above freezing just about everywhere already, and should continue warming overnight within strong warm air advection. So no freezing precip is expected. Temps will begin a warming trend with highs in the 60s everywhere below about 3500 ft, which is 8-14 degrees above normal. It will be breezy today, as a westerly low-level flow mixes down across the area. Gusts will be highest in the usual high elevations east of the French Broad Valley and Northern Mountains, but should stay below advisory criteria. Winds should lose their gusts tonight outside the high terrain. Some guidance is hinting at patchy fog forming in the NC foothills and Piedmont. But dewpts remain fairly low, and fog looks unlikely. Lows will be well above normal, mainly in the 40s to lower 50s.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/

As of 1220 AM EST Tuesday:

Key Message: Near-record high temperatures are forecast for Christmas Eve, with very warm conditions continuing into Christmas.

The upper flow pattern will be dominated by a highly amplified ridge across the central Conus, resulting in very warm temperatures across much of the eastern half of the country through the period. A few lingering mountain/NW flow upslope showers are possible at the start of the period, but Wed should otherwise be dry, with max temps warming to 15-20 degrees above climo. Based upon the current forecast, record daily highs will be in jeopardy at KGSP and KCLT. The next in a series of speed maxima digging across New England will result in another round of relatively moist warm advection across the region on Thursday, with deeper forcing and precip chances again maximizing north of our CWA, and only token chance, mainly mountain PoPs warranted late Wed night into Christmas. Very warm conditions continue on Christmas Day, but daily records are considerably warmer/not as achievable.

LONG TERM /FRIDAY THROUGH MONDAY/

As of 1240 AM EST Tuesday:

Key Messages: Well-above-normal temperatures will continue through the weekend. A pattern change involving the arrival of an arctic front is looking increasingly likely early next week.

The major central Conus ridge will begin to de-amplify late in the short term...in response to a wave train setting up over the Canadian Rockies and Prairie...with additional height falls invading the West Coast of the Conus. By the end of the weekend, the ridge is forecast to completely break down, with a strong upper low/cyclone expected to develop across the upper Miss Valley/Great Lakes by Sunday morning. Resultant strong/large scale height falls are anticipated across the East by the end of this forecast period, with an arctic cold front likely sweeping across our forecast area in the late Sunday/Sunday night time frame. This will bring about a dramatic temperature swing...as well-above normal/near-record warmth that is forecast Friday through the weekend is expected to be displaced by well-below normal temps on Monday (i.e., max temps Monday forecast to be ~30 degrees colder than on Sunday). Otherwise, global models depict uninspired moisture return ahead of the arctic front, while deeper forcing will most likely pass north of the CWA, so PoPs are mainly limited to the 20-40% Sunday into Sunday night.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: Spotty sprinkles can be seen on the radar crossing the region, but shouldn't result in any restrictions at any of the TAF sites. There is still about a 20-30% chance of some MVFR cigs at KAVL and KAND thru about 15z, then possibly some MVFR clouds lingering in the valley around KAVL this aftn. Mid clouds should start to scatter out around midday to early aftn, leaving lower clouds along the TN/NC border that persist thru tonight. Winds will become gusty across the Piedmont by around 15z, with peak gusts in the 15-20z time frame that may be around 25 kt (cannot rule out a very period of some gusts between 25 and 30 kt at KCLT in the 16-19z time frame). Some LLWS is possible before the sfc winds pick up at KAVL and KHKY this morning. Winds should weaken and lose gusts by around sunset, and become light overnight. Some guidance is hinting at patchy fog developing tonight, mainly in the NC foothills and Piedmont. But confidence remains only about 20-30%, thus no mention in any of the TAFs at this time.

Outlook: A weak front will bring low-end chances for rain and associated restrictions through early Wednesday, mainly across the mtns. Otherwise, mostly dry, VFR conditions should prevail thru the end of the week, outside of possible patchy mtn valley fog and low stratus each morning.

CLIMATE

RECORDS FOR 12-24

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 72 1955 17 1906 59 2015 -5 1983 KCLT 73 2015 29 2022 63 2015 6 1983 1906 KGSP 71 1964 28 2022 61 2015 7 2022

RECORDS FOR 12-25

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 71 2021 14 1983 59 2015 -7 1983 KCLT 77 1955 22 1983 63 2015 4 1983 KGSP 78 1955 22 1983 61 2015 6 1983

RECORDS FOR 12-26

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 78 1971 17 1902 55 2015 0 1983 KCLT 77 2021 27 1983 58 2015 6 1983 1964 KGSP 76 2021 28 1983 62 1987 5 1985 2015 1980

RECORDS FOR 12-27

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 72 1971 19 1902 59 2015 3 1925 KCLT 72 2021 22 1892 65 2015 15 1970 2015 1948 1971 1925 KGSP 75 1971 29 1925 64 2015 12 1925

RECORDS FOR 12-28

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 73 1889 19 1894 56 2015 0 1925 KCLT 77 1971 30 1950 58 2015 10 1925 1935 1925 KGSP 75 1971 31 1950 64 2015 9 1925 1925

GSP WATCHES/WARNINGS/ADVISORIES

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