textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Rain amounts are trending up for Saturday night, especially across the mountains.

KEY MESSAGES

1. Above normal temperatures with daily chances for showers and thunderstorms through Saturday. 2. Cold front Saturday night and Sunday increases the chance for rainfall. 3. Frost/freeze conditions possible in the mountains early to middle of next week.

DISCUSSION

Key message 1: Above normal temperatures with daily chances for showers and thunderstorms through Saturday.

The synoptic regime remains relatively unchanged as a prominent Bermuda high is parked just off the East Coast and will be the primary influencer for our weather through the end of the week and into the weekend. Farther west, an active southern stream extends from the Great Basin to the Southern Plains with a lead shortwave trough lifting across the Mississippi Valley into the Midwest. Associated forcing for ascent will be displaced well away from the Southern Appalachians with rather height heights continuing to support above normal temperatures. Afternoon highs will climb into the mid 70s to low 80s each day. Otherwise, at least isolated to widely scattered afternoon showers and thunderstorms will be possible each day within a warm and moist airmass. Coverage may be fairly limited today and Friday, but should increase on Saturday ahead of an approaching trough as low-level flow ramps up.

Key message 2: Cold front Saturday night and Sunday increases the chance for rainfall.

By Saturday, guidance depicts a developing surface low across the midwest and a trailing cold front. Latest guidance does slow the FROPA compared to previous forecasts. Ahead of the front, the CWA remains in an open warm sector as the persistent high off the coast continues to advect moisture into the southeast. The good news is this looks to bring a decent rainfall to portions of the far western mountains. At this time, guidance shows an uptick in chances for rain amounts exceeding 1" (30-40%) Saturday night into Sunday. As usual, the line of storms appears to weaken as it crosses the terrain, decreasing rain amounts. However, pre-frontal showers and thunderstorms are possible which could increase rain chances for isolated locations. At this time, severe weather cannot be ruled out. Looking at long range modeled soundings, there could be enough instability and shear to have a pre-frontal storm be strong, possibly severe. But the line coming in overnight doesn't appear to have the gumption needed for too much concern, outside of strong winds and heavy rainfall. So for now, expect a few showers and thunderstorms Saturday afternoon/evening with another chance for possible severe with a line of storms ahead of a cold front Saturday night into Sunday.

Key message 3: Frost/freeze conditions possible in the mountains early to middle of next week.

Behind the front, drier conditions return along with cooler temperatures. Guidance at this time depicts overnight near freezing temperatures reaching the mountains as early as Sunday night. However, the colder air looks to be Tuesday night for the mountains, despite chillier conditions for locations east of the mountains. Long range guidance shows the source for these freezing temps coming from a potential backdoor cold front as high pressure migrates eastward. From Tuesday onward, surface winds prevail NE as a dry CAD sets up. At this time, the chances for freezing temps in the mountains are 20-30%, should this pattern continue to trend in model guidance.

AVIATION /06Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: Predominately VFR conditions will prevail through the TAF period at all terminals. A deck of low stratus may develop into the I-85 corridor during the early morning hours through sunrise with a brief period of MVFR ceilings possible at KCLT. Otherwise, isolated to widely scattered showers and perhaps a stray thunderstorm will be possible this afternoon, mainly across the mountains. Confidence is too low to warrant mention in the TAFs with the exception of KAVL where a PROB30 group will be carried. Winds will remain out of the south/southwest with a few low-end gusts possible this afternoon.

Outlook: Daily chances for showers and thunderstorms with associated restrictions through the weekend. A cold front will bring greater chances for restrictions Saturday night into Sunday morning. Dry high pressure moves in Monday.

GSP WATCHES/WARNINGS/ADVISORIES

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