textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Fire weather elements will be less critical on Wednesday. Nevertheless, increasingly gusty winds, warmer temperatures, and the expectation of low fuel moisture will elevate the fire danger.

KEY MESSAGES

1. Snow with gusty NW winds continue across portions of the mountains near the NC/TN border through tonight, with below normal temperatures through Tuesday. Impacts from the snow could create hazardous travel conditions in these locations. 2. Near-critical fire weather conditions are expected each afternoon through Tuesday. 3. Temperatures warm above normal for the latter half of the week, with warm conditions continuing through the weekend. A cold front increases rain and possible thunderstorm chances across the area early Thursday into Friday.

DISCUSSION

Key message 1: Snow with gusty NW winds continue across portions of the mountains near the NC/TN border through tonight, with below normal temperatures through Tuesday. Impacts from the snow could create hazardous travel conditions in these locations.

Continued northwest flow snow and gusty winds across the mountains should gradually subside later this evening into the early parts of the overnight period as a ~1030mb surface high shifts south over the MS Valley and the deep Nor'easter low shifts to the New England Coast before eventually reaching Nova Scotia tonight. The ongoing Winter Storm Warning and Winter Weather Advisory remains in effect through 12 AM Tuesday and still looks to be on track. An additional 1-4" of snow is expected through this evening for elevations above 3500' along the immediate Tennessee border in the favored upslope zones, with less than an inch below 3500' and locations just outside the NC/TN border. The snow is still shown tapering off later this evening. Wind Advisory criteria gusts will continue at the highest peaks through the afternoon with gusts up to 55 mph. Deeper mixing and relatively tight pressure gradient will produce gusts of 25-35 mph elsewhere. Gusts will decrease this evening as the boundary layer shrinks and the upper trough and coastal low lifts further northeast away from the CFWA, allowing the pressure gradient relaxes.

Frigid temperatures are expected once again tonight with wind chills in the single digits in the mountains and upper teens to lower 20s outside of the mountains. The actual temperature is forecasted to end up a few ticks lower compared to Sunday night, but the wind will be a lot lower as well in comparison. Surface high will slide along the Gulf Coast Tuesday as temperatures rebound into the upper 40s and lower 50s outside of the mountains for afternoon highs. The mountains will rebound as well with mid 40s expected in the major mountain valleys and continued cold in the higher elevations, especially in locations with a good snow pack.

Key message 2: Near-critical fire weather conditions are expected each afternoon through Tuesday.

RH values between 30-40% should continue to drop towards 25% this afternoon with sustained northwest winds at 10 to 20 mph with gusts up to 35 mph, with very isolated 40 mph east of the mountains. These conditions will elevate fire weather concerns, especially across the foothills where fuel moistures are lower due to the lack of sufficient rainfall from previous events over the past few days. Mountains will have winds to support fire weather concerns, but RH values remain well-above the threshold due to lower temperatures this afternoon.

Dry airmass remains in place on Tuesday as temperatures rebound into the upper 40s and lowers 50s in the major mountain valleys, foothills, and Piedmont, while dewpoints remain in the teens. Expect RH values to tank into the 15-25% range, which will especially elevate fire weather concerns. However, winds will be a lot lower compared to today with southwest winds at 5-10 mph. Light winds will be a limiting factor on Tuesday, but elevated fire weather concerns are expected to be present nonetheless.

Winds begin to steadily increase from the SW Tue night and especially Wed, when gusts of 20 to 30 mph are possible across much of the area during the afternoon. Humidity will also be increasing during this time, such that minimum RH is expected to mostly be in the 30 to 40% range on Wed. Nevertheless, 10-hour fuel moisture will likely be low and temperatures will be warmer, so fire danger is expected to remain somewhat elevated into mid-week.

Key message 3: Temperatures warm above normal for the latter half of the week, with warm conditions continuing through the weekend. A cold front increases rain and possible thunderstorm chances across the area early Thursday into Friday.

The upper flow pattern will steadily amplify through the latter half of the week, with a series of speed maxima expected to carve out a trough that is forecast to be centered from the central Gulf through the Great Lakes by Thursday morning. One speed max that will dig toward the Ohio and TN Valleys Wed night is forecast to support surface wave development to our west, with attendant warm frontal activation warranting increasing PoPs across our area...with chances ranging from likely near the TN border...to slight across the southeast tier. The latest global deterministic model guidance sources have diverged a bit on the eventual evolution of the surface wave, and rainfall amounts...as well as any low-end severe storm threat will hinge upon the track and intensity of surface development. Nevertheless, guidance continues to suggest Gulf moisture flux will be more than respectable as the surface wave passes near or over the CWA later Thu into Thu evening, and PoPs of 80-90% for at least modest QPF continues to be warranted.

Temperatures are forecast to warm 5-10 degrees above climo ahead of the front Wed night into Thu...and current indications are that any air mass change behind the front will be minimal...at least in terms of temperatures, while heights are forecast to quickly increase late in the week through the weekend. As such, forecast temps remain solidly above climo Thu night through Monday. Some global model sources and ensemble inputs continue to suggest some potential for re-activation of the baroclinic zone across the region late in the forecast period, and token/small PoPs enter the forecast for the late Sunday through Monday time frame.

AVIATION /18Z MONDAY THROUGH SATURDAY/

At KCLT and elsewhere: FEW/SCT VFR stratocu developing east of the mountains, KAVL continues to remain socked in with OVC035. Gusty northwesterly winds will continue at 20-30+ kts through the rest of the afternoon before gradually subsiding overnight. KAVL maintains at least low-end gusts through the overnight period before diminishing around or just after daybreak Tuesday. Winds turn out of the southwest on Tuesday, but will be considerably weaker at 4-8 kts, slightly higher at KAVL from the northwest. A deck of high clouds will pass through during the daytime period Tuesday, but that will be about the extent of the forecast.

Outlook: Quiet weather returns to the region through Wednesday. Another low pressure system will approach the area on Thursday, bringing showers and associated restrictions.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Winter Storm Warning until midnight EST tonight for NCZ033-050. Winter Weather Advisory until midnight EST tonight for NCZ048>052. SC...None.