textproduct: Greenville-Spartanburg

SYNOPSIS

Cool high pressure moves in today, then an upper level disturbance arrives late tonight and brings the potential for light precipitation through Monday. Dry conditions return by midweek with normal temperatures. A cold front should arrive late in the week.

NEAR TERM /THROUGH TONIGHT/

As of 6:25 AM EST Sunday...

Key Message 1: A Dense Fog Advisory remains in effect outside of the NC mountains thru 10 AM this morning. A Freezing Fog Advisory is also in effect for portions of the NC mountains and along the I-40 Corridor until 10 AM.

Areas of dense fog have developed across most of our non-mtn zones over the past few hrs. The fog should begin to dissipate by mid- morning, but could linger thru late morning at some sites.

Otherwise...dry high pressure will continue building into the region while an upper trof pushes east of our fcst area by late this evening. Cloud cover will continue to gradually increase overnight, especially east of the mtns. Despite the cloud cover, it will be a cold night with temperatures falling near to below freezing across our fcst area. The sfc high will be overhead today allowing somewhat drier and warmer conditions to develop. Nonetheless, high temps are still expected to remain roughly 4 to 8 degrees below normal thanks to lingering cloud cover. Another round of dense fog may develop later tonight into early Monday thanks to calm winds and lingering low-level moisture, but it's likely to be more patchy than what we're currently observing.

Key Message 2: Another weak low pressure system will develop to our south later this evening and into Monday. This system is expected to bring light snow accumulations to portions of the NC mountains and rain elsewhere across our fcst area. As such, a Winter Wx Advisory has been issued for accumulating snow for the northern NC mountains. The Advisory is in effect from 1 AM Monday until 1 AM Tuesday.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

Key Messages:

1) Light snow will continue at high elevations across portions of the mountains on Monday, with cold rain elsewhere.

2) The precip could change to light snow across the northern foothills and northwest Piedmont before ending on Monday, but the potential for accumulation looks minimal at this time.

3) Dry conditions return Tuesday with below normal temperatures.

As of 125 AM EST Sunday: We should be in the middle of a short wave traversing the region at daybreak Monday, which the guidance has been fairly consistent in handling. What remains inconsistent, however, is the extent of wintry precip in the model guidance, with the GFS continuing to look overly optimistic (if you want lots of snow). Again, the QPF in that model looks overdone in light of the forcing confined mainly to mid-levels. The timing of the wave continues to be such that most of the precip potential will be carried off to the east by the middle part of the day before the cold air really has the chance to make a serious push from the north, though the GFS certainly tries. Confidence is high enough across the high elevations of the nrn mountains to issue an Advisory for snow starting early Monday because that part of the fcst area is less dependent on the timing of the cold air surge. There should be enough precip potential to bring the snow totals up into the 1-3 range in that area. The rest of the mtns just don't have enough in the QPF to warrant an Advisory. East of the mtns...there are too many limiting factors related to the time of potential changeover, the precip amounts, and duration. What is most likely is that the cold air chases the back edge of the precip east of the mtns across the nrn foothills and northwest Piedmont and we get a brief period of light snow in the mid/late afternoon that produces a dusting or less than an inch. Sorry, just a cold rain across the Upstate and northeast GA outside the mtns. Temps will remain below normal because of the clouds and precip...well below over the nrn tier. The precip moves out completely by sunset east of the mtns, but could linger over the nrn mountains into the evening, so the Advisory will run through 06Z Tuesday.

With that out of the way by daybreak Tuesday, high pressure should build in Tuesday and we should finally see some sun again, but high temps will be on the order of ten degrees under normal. The pattern moves right along, though, with the high center moving off to the east Tuesday night allowing for some warm advection to commence aloft overnight. So, low temps Tuesday night will only be slightly under normal.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

Key Messages

1) Fair but breezy Wednesday with near normal temperatures.

2) Low confidence in precip associated with a cold front that moves through late in the week.

3) Behind the front, a potential cold wave next weekend with temperatures running around 15 degrees below normal.

As of 1251 AM EST Sunday: The quietest day continues to look like Wednesday, but a clipper low moving across the Great Lakes in the fast-moving broadly cyclonic flow aloft still looks like it will bring us a breezy day. Guidance continues to show a southwesterly low level jet translating east across the region during the day when we will be able to mix down some of the higher momentum air. The resulting warm advection should allow temps to climb back up close to normal. Fortunately, the RH should stay high enough to alleviate most fire weather concerns. The breezy conditions should taper off Wednesday night as the low level jet moves away and the gradient temporarily relaxes. Beyond that, confidence for the late part of the work week is on a downward trend because the guidance suffers from consistency issues regarding the potential for the next clipper-like wave dropping through the broad upper trof, which leads to multiple scenarios. So, it becomes more difficult to say when a sfc cold front will get pushed across the region or how much moisture will be available for precip. Oddly enough, the model blend appears more confident than I am with the main precip potential late Thursday through Friday. The cold air looks like it will remain well behind any boundary that would move through with the precip, so we are looking at mainly rain, with some very high elevation minimal snow potential. No big deal.

The big deal, however, will be the temperatures behind the boundary when it finally does move through. The overall pattern looks more like typical dead-of-winter over the east with a deep mid/upper low over eastern Canada, which would support a large arctic sfc high dropping down across the Plains on Saturday and over the Southeast on Sunday. This pattern would support a period of light NW Flow Snow on the TN border Friday night, but more importantly would bring a cold air mass across our region for the weekend. Temps would be on the order of 15 degrees below normal in spite of clear sky. Brrr.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: Areas of dense fog will likely persist at all of our taf sites thru most of the morning with freezing fog expected to continue at KAVL thru mid-morning. The fog/low stratus should gradually lift late morning into early afternoon, but confidence remains fairly low that most sites will return to VFR before mid to late afternoon today. Some areas may not sct out completely before MVFR to IFR cigs, and to a lesser extent, MVFR visby return again later this evening. Rain chances increase towards the end of the taf period early Monday with PROB30s for RA at all taf sites beginning around 08 to 10z. Expect prevailing RA to begin at KAVL by roughly 08z Monday, with KCLT following suit by roughly 14z. Otherwise, winds should remain light to calm thru most of the period, with some sites favoring a S to SE direc- tion this afternoon.

Outlook: A low pressure system will bring precip and restrictions late Sunday night into Monday. Dry high pressure is expected to spread back over the area Tuesday into Wednesday.

GSP WATCHES/WARNINGS/ADVISORIES

GA...Dense Fog Advisory until 10 AM EST this morning for GAZ010-017- 018-026-028-029. NC...Dense Fog Advisory until 10 AM EST this morning for NCZ056- 068>072-082. Winter Weather Advisory from 1 AM Monday to 1 AM EST Tuesday for NCZ033-049-050. Freezing Fog Advisory until 10 AM EST this morning for NCZ035>037-051>053-057>059-062>065-501>510. SC...Dense Fog Advisory until 10 AM EST this morning for SCZ008>014- 019-101>109.