textproduct: Greenville-Spartanburg

SYNOPSIS

Cool high pressure will move past the region today and Sunday, but then an upper level disturbance will bring another round of precipitation for late Sunday night and Monday. The middle part of next week will be dry with temperatures returning to normal. The next cold front should arrive late in the week.

NEAR TERM /THROUGH TONIGHT/

As of 1:05 AM EST Saturday: An area of sct precip continues to make its way eastward over CAE's area to our south. A broad deck of low stratus will persist over our region thru the overnight and much of the morning as a stalled, moist frontal bndy lingers just to our south. With light to calm winds across our area and RH values near saturation, we are already seeing some patchy fog develop over the SC Upstate and NC Piedmont. If the fog becomes more prevalent over the next few hrs, we will likely need an SPS or possibly a Dense Fog Advisory for portions of our fcst area. Low temps this morning will be near to slightly above normal for most of our fcst area.

Otherwise, another wave of weak low pressure will move east along the above-mentioned frontal boundary to our south. This will bring a return of deeper moisture, weak isentropic lift, and low-end light rain chances, mainly along and south of the I-85 corridor late this morning and into the early afternoon. The low moves east of our area during the afternoon taking the lift with it. The low clouds are ex- pected to lift thru the afternoon and will likely sct out, first over our higher terrain and then south and east. This should help erode the wedge and allow high temps to rebound a decent amount compared to yesterday. Nonetheless, highs will still be roughly 5 to 10 deg below normal for early December.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/

Key Messages:

1) Some light snow possible late Sunday night and Monday over the mountains, but right now areas east of the mountains are most likely to only get cold rain.

2) Temps remain below normal.

As of 1235 AM EST Saturday: The main feature of interest continues to be a southern stream short wave forecast to make a run at the western Carolinas Sunday night and then crossing the region on Monday, while cold air makes an attempt to drop south across the region. Needless to say, the timing of this interplay is difficult and uncertain roughly 48 hrs out. Confidence in the track and timing of the wave is decent enough, arriving in the early morning Monday and then moving across the region in the first half of the day. The wave should have enough moisture with it to wring out some light precip. However, most of the forcing will be at mid-levels. Not really seeing much in the way of upper divergence or low level isentropic lift or frontogenesis across our region, so that figures to be a limiting factor. Thermal profiles suggest this will be either a rain or snow situation, which simplifies things. Confidence is better for an elevation-dependent rain/snow combo across the mtns starting in the pre-dawn hours, because there will be enough cold air aloft over the higher terrain so the p-type is less dependent on the arrival of the colder air from the north. Outside the mtns is much less certain. As it looks right now, most of the precip would be moving off to the east before it would cool off sufficiently across the foothills and western Piedmont for much in the way of snow. Plume diagrams don't look great, either. Bottom line...right now little stock is placed in the operational GFS in its depiction of significant snow amounts over the mtns and extent of snow east of the mtns. Signs point toward an Advisory-level event mainly over the nrn mountains for Monday morning.

Otherwise, temps will remain below normal. Sunday looks close to normal for highs, but Monday should be on the order of ten degrees under normal with the early precip and clouds. The cold air surge will eventually arrive, so overnight lows Monday night will be well below freezing.

LONG TERM /TUESDAY THROUGH FRIDAY/

Key Messages

1) Quiet through mid-week with a warming trend back to normal temperatures.

2) Breezy Wednesday ahead of an approaching cold front.

3) A potential cold front passage late Thursday or Friday could bring cooler temps and another chance of precipitation.

As of 1254 AM EST Saturday: Guidance shows the region remaining under a broad long-wave upper trof through the middle part of the week with the main sfc high, though relatively weak, moving across the region on Tuesday. This would keep temps about ten below normal for Tuesday highs, but the sfc high moves off to the east Tuesday night. If all goes according to plan, the high to our east and the passage of a fairly strong clipper low over the Great Lakes Wednesday would quickly increase the southwesterly warm advection flow with a low level jet translating east overhead during the day. That results in a quick rebound to near-normal temps Wednesday afternoon. Assuming mixing is deep enough, there would be the potential for breezy southwest winds through the day and into the overnight hours. Signs still point toward another strong nrn stream short wave dropping down into the trof late in the week, digging and sharpening the trof and pushing a strong cold front toward our region on Thursday. Passage would be either Thursday night or Friday morning, with precip being mostly rain with some high elevation snow potential. There would be a decent chance of some NW flow snow on the TN border behind the front in this scenario, with temps falling back down into the realm of ten degrees under normal for the weekend.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: Numerous restrictions will continue overnight and into the morning as widespread low stratus and areas of fog per- sist over the area. IFR to LIFR cigs are expected at most terminals with periods of dense fog also fairly likely. The latest guidance suggests that fog development is less likely at KAVL despite the light to calm winds, however it remains possible thru the morning. Eventually, conditions will improve heading into the afternoon and there may end up being a fairly sharp gradient between the low stratus and VFR, which could bring rapid improvement once the retreating bndy lifts back north. This should bring a return to VFR at all terminals by the late afternoon to early evening. Winds will remain light and VRB to calm thru the morning, and eventually pick up from the SW during the afternoon. They are expected to go light to calm again later this evening. At KAVL, calm winds will eventually take on a NWLY direction this afternoon, but will likely be light and VRB at times thru the day.

Outlook: Another round of low stratus and fog is possible Saturday night into Sunday morning across portions of the foothills and Pied- mont. Another storm system may bring more precip and associated restrictions Sunday into Monday. Drying high pressure is expected to spread back over the area by early Tuesday.

GSP WATCHES/WARNINGS/ADVISORIES

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