textproduct: Greenville-Spartanburg

SYNOPSIS

Dry high pressure builds into the area today, bringing temperatures near normal to start the week. A warm front will lift northeast through the area Tuesday, bringing small rain chances to the mountains and an unusually warm air mass for late December to the region. Expect dry conditions elsewhere, and well-above normal temperatures for the Christmas holiday.

NEAR TERM /THROUGH TONIGHT/

As of 1215 am EST Monday: The upper flow pattern will continue to steadily amplify during the near term as a ridge builds strongly across the Rockies and Great Plains. The pattern will nevertheless remain quite progressive, and the center of very dry surface high pressure is forecast to move from the central Appalachians early this morning to Cape Hatteras by the end of today. Low RH/Fire Weather will therefore be our primary near term concern. Surface mesonet obs reveal dewpoints in the single digits with even some sub- zero readings in spots across the high elevations this morning...so there is plenty of very dry air available to mix to the surface later today...and minimum RH is expected to bottom out in the 15-20% range across much of the forecast area. Winds will be a non-issue, but a Fire Danger Statement may be necessary for out GA zones... where FDS criteria are lower. This is pending collaboration with neighboring forecast offices. Max temps today will be very close to climo...the last day they will be anywhere near normal until at least early next week.

The next in a series of speed maxima will approach the Great Lakes from the Canadian Prairie late tonight into early Tuesday, resulting in development of a warm advection pattern and shallow moisture return across our region by around daybreak Tuesday. Moisture will be too shallow and the near-surface layer too dry to support much in the way of noteworthy PoPs, but token 20% probabilities are advertised by daybreak across the NC counties bordering TN. Min temps will be 3-5 degrees above climo...with lows likely occurring early in the night (especially across the mountains) before the warm advection kicks in. This warming should preclude any precip-type concerns...in the off chance that precip does develop.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

As of 1130 PM EST Sunday:

Key Message: Warming trend ramps up through the middle of the week, with small rain chances in the NC mountains, mainly near the TN border.

A weak frontal boundary will slip into the area Tuesday under an amplifying flow aloft. An increasing pres gradient along with a decent W/NW 850 mb flow should support breezy conditions across the area, with highest gusts in the NC northern mountains. Gusts are not expected to approach advisory criteria. Upslope flow may squeeze out a few light rain showers near the TN boarder. But downsloping should keep the rest of the area dry. The front lifts back north as a warm front on Wednesday, with just some increase in clouds expected in the aftn thru Wednesday night. Temps will warm to about 5 to 10 deg above normal Tuesday, and about 15 degrees above normal on Christmas Eve. These fcst highs Wednesday are within a couple degrees of records for GSP and CLT climate sites. (See climate section below for more details).

LONG TERM /THURSDAY THROUGH SUNDAY/

As of 1205 AM EST Monday:

Key Message: Well-above-normal temperatures for the Christmas holiday, continuing into the weekend.

An upper ridge will continue to build with an axis over the lower to mid-MS Valley region Thursday. The ridge will then begin to flatten, but the axis will shift over the Southeast Friday. The latest medium range guidance then diverges on what the ridge will do over the weekend, with some retrograding the high (like the 00z GFS), or digging a deep trough over the central CONUS (like the 21/12z ECMWF). At least through Friday, guidance is in very good agreement on anomalously warm air spreading in across the area from the west, with downslope flow helping enhance max temps even further for the Piedmont. Latest fcst highs are into the upper 60s to mid 70s east of the mountains for Christmas day and the day after, which is within a few degrees of records (see climate section below). Some moisture may brush the NC mountains from the west Friday, but overall, dry weather is expected to continue thru Saturday. Models seem to be backing off any cool-down for Saturday, as well, with yet another day of near-record highs possible. We may see a pattern change begin to unfold with a stronger front cross the area Sunday and a cool-down into early next week. With such warm temps ahead of the front, no wintry precip types are expected. And the air mass ahead of the front doesn't look appreciably moist/unstable for any severe weather threat or much in the way of QPF.

AVIATION /06Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR conditions will persist through at least Monday evening, with only periods of mostly thin high clouds expected. NE winds, mostly in the 4-7 kts range are expected through the morning, veering toward the ESE and weakening a bit early in the afternoon, becoming light/variable during the evening. Moisture return and increasing lift are expected toward daybreak Tue, likely resulting in development of low clouds at KCLT...but these are currently expected to remain at the VFR level.

Outlook: A weak front will bring low-end chances for rain and associated restrictions Tuesday into Wednesday, mainly across the mtns. 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

GSP WATCHES/WARNINGS/ADVISORIES

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