textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Not quite as cold but still frigid temperatures for Monday night into Tuesday, especially across the mountains.

Moderate uncertainty for a Thursday cold front.

High uncertainty for the weather system next weekend.

KEY MESSAGES

1. Quiet weather tonight through Monday with below-normal temperatures 2. Another cold air mass spreads over the region by the middle of next week. A Cold Weather Advisory may be needed for a portion of the mountains Monday night into Tuesday. 3. A weak cold front may cross the area Thursday with a slight chance for precipitation. Guidance is trending toward another system affecting the area next weekend but sensible weather and impacts are highly uncertain.

DISCUSSION

Key message 1: Quiet weather tonight through Monday with below-normal temperatures

Cold front exits to our east and cold, dry high pressure builds in from the west. Clearing skies and cooler thicknesses under a deep trough aloft will help overnight lows dip 5 to 10 deg below normal. Lingering wind in the high terrain will produce wind chills in the single digits above zero, with some sub-zero wind chills on the highest peaks. Monday looks sunny with highs about 5 deg below normal in the Piedmont, but 10-15 deg below normal in the mountains.

Key message 2: Another cold air mass spreads over the region by the middle of next week. A Cold Weather Advisory may be needed for a portion of the mountains Monday night into Tuesday.

A large area of surface high pressure and a cold and very dry air mass will move into the area Monday night into Tuesday. Winds will become breezy, at least over the mountains before the center of the high moves in later on Tuesday. Lows will be 10 to 15 degrees below normal. With the breezy winds, wind chill values look to fall below zero for the higher elevations. A Cold Weather Advisory may be needed, especially for the higher elevations. Tuesday night will be nearly as cold but lighter winds keep wind chills above critical values. Tuesday will be the coldest day with highs 10 to 15 degrees below normal.

Key message 3: A weak cold front may cross the area Thursday with a slight chance for precipitation. Guidance is trending toward another system affecting the area next weekend but sensible weather and impacts are highly uncertain.

A weak short wave rotates through the deep upper trof over the eastern CONUS Thursday taking the trof axis with it with zonal flow developing Friday. Still expecting a weak cold front associated with the short wave to cross the area on Thursday. Forcing is weak over our area and moisture will be limited. This results in only a slight chance of a wintry mix mainly for the NC mountains Wed nite and Thu morning. Some rain may develop outside of the mountains. There is still some uncertainty on precip types but good agreement that any QPF will be very light and the chance of any impacts looks very low at this time.

Heights begin to fall Saturday into Sunday as yet another short wave dives south and moves across the area. A baroclinic zone, and a moist low level easterly flow, sets up across the Southeast between high pressure to the north and weak low pressure in the Gulf. This combined with increasing isentropic lift and frontogenetical forcing leads to precip developing across the area. The operational guidance and most ensemble means are trending in this direction with temps cold enough for at least a wintry mix across the area. That said, the LREF mean and the NBM have little to no probability of even Advisory level wintry precip. As usual in these types of situations, confidence is very low given the model to model and run to run inconsistency. Keep up with the latest forecasts as they are likely to change going forward.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

At KCLT and elsewhere: Clouds and very light precip moves out of the area this aftn, with just some lingering -RA around KCLT until about 20z. Generally SKC for the rest of the period. Light wind at KCLT will favor a WNW direction thru 00z, then toggle to SW when it picks up Monday morning. Gusty winds will continue at KAVL until around sunset, then resume late Monday morning. May see some low-end gusts across the Upstate Monday within a WSW flow, with highest chances at KAND.

Outlook: Dry high pressure will settle over the region through midweek, keeping VFR conditions across the region. A cold front may bring a chance of some light precip, mainly to the mountains Wednesday night into Thursday.

GSP WATCHES/WARNINGS/ADVISORIES

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