textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No significant changes aside from update for 12z TAF set.

KEY MESSAGES

1. Near-normal temperatures but low humidity through Friday, with near-zero chance of rain. 2. Another frontal system is expected to arrive from the west this weekend, bringing back rain chances but also below-normal temperatures. The system may stall near our area, and thus this pattern is likely to linger into early next week.

DISCUSSION

Key message 1: Near-normal temperatures but low humidity through Friday, with near-zero chance of rain.

A cold front will continue pushing south of the forecast area today until stalling north of the Gulf Coast tonight. A dry continental airmass will continue to build in behind it on breezy northwest winds. Lapse rates will be poor and the column very dry, so aside from perhaps a couple of brief, stray showers from taller cumulus this afternoon, the day should be devoid of any deep convection. Temps should top out a few degrees below yesterday's maxes, back to around normal, though some areas along/north of I-40 may see maxes slightly below normal. Low-level CAA will continue into Thursday; min temps tonight and maxes Thu are expected to be a little below normal, and PoPs end up basically zero. A slight rebound in temps is expected Friday as shortwave ridging occurs over the area.

Diurnal mixing won't be too remarkably deep, but enough to tap into very dry air above 850 mb. This appears likely to bring RH down well into the 30s percent, and per the NBM 10th percentile, which is what often verifies on moderately mixed days in the cool season and spring, a few of the usually more mixed locations could see RH dip below 30 percent. Winds will however be lighter Thursday/Friday compared to today, and fuel moistures are not likely to be of concern given the wet pattern of late.

Key message 2: Another frontal system is expected to arrive from the west this weekend, bringing back rain chances but also below-normal temperatures. The system may stall near our area, and thus this pattern is likely to linger into early next week.

The anomalously deep anticyclone over the Desert Southwest will persist through the weekend. A well defined shortwave will round that feature Friday, progressing through the MS Valley and into the Ohio Valley by late Saturday, accompanied by a surface low. This will reactivate the stalled front near the Gulf Coast, in turn leading to increasing cloud cover and precip chances over our area Saturday, but also supporting a warming trend via WAA aloft. Models continue to differ as to whether or where the shortwave cuts off into a closed low, but generally that looks to occur to our west. We should thus remain under a warm advection regime Sunday into Monday, when we feature likely PoP over most of the area. A hydro threat could develop given very high PWATs and likely slow storm motion. Confidence decreases beyond Monday as differences in the depiction of the cutoff low affect the position of the front, but PoPs still remain above climo Tue-Wed. Clouds and precip lead to temps falling back below normal Sun-Tue.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

At KCLT and elsewhere: Surface front appears to have briefly stalled early this morning near the SC sites, but it should push south in the first few hrs of the period. The effect is that winds will be more westerly there to start the period, compared to the NC sites which are clearly north of the front. NW winds will predominate otherwise today, veering to N or NE overnight tonight. IFR stratus is present in some of the NC mountain valleys, and could briefly expand to KAVL in the first hr or two of the period. Aside from that, just a few mountain wave cirrus today along with FEW diurnal cu at VFR level. Via mixing some gusts of 15-18 kt are likely in the afternoon, possibly excepting KAND. Gusts may continue through late evening at KAVL as high pressure continues to build in from the NW, and via mountain gap effect these could also be felt at KGSP and KGMU. Otherwise light northerly breezes continuing tonight. Can't rule out some valley stratus/fog reaching KAVL at daybreak Thu but confidence too low to mention this far out.

Outlook: Dry and mostly VFR through Friday, with shower and thunderstorm chances and associated restrictions returning this weekend into early next week. Low stratus and/or fog will be possible each morning, mainly in the mtn valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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