textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No major changes to forecast thinking over the next week.

KEY MESSAGES

1. Dry through Thursday. Much warmer and more humid conditions develop on Thursday. Breezy winds return Thursday, bringing some relief from the higher humidity. 2. Record high temperatures possible Friday ahead of another cold front. The front brings a chance of showers late Friday and Friday night. 3. Cool, dry high pressure builds in for the weekend with moderating temps early next week.

DISCUSSION

Key message 1: Dry through Thursday. Much warmer and more humid conditions develop on Thursday. Breezy winds return Thursday, bringing some relief from the higher humidity.

Upper troughing remains over the Carolinas through tonight before heights gradually build on Thursday in response to the northeastern periphery of an upper ridge (centered over Southern Texas/northern Mexico) building into the Southeast. This upper ridging will allow for the return of much warmer and well above normal temperatures on Thursday. At the surface, the southwestern periphery of a dry surface ridge centered over the western Atlantic will remain over the Southeast through Thursday night. Meanwhile, a cold front will slowly sink southeastward Thursday into Thursday night, but will remain northwest of the GSP CWA through daybreak Friday.

Periodic cloud cover can be expected through tonight, before sunnier, much warmer and more humid conditions return Thursday. Should see some relief from higher humidity in the form of breezy winds (well below advisory criteria) on Thursday. Highs on Thursday will end up 10-15 degrees above normal, ranging from the mid 70s to lower 80s across the lower elevations, and the 60s across the higher elevations. Lows tonight will end up around 7-10 degrees above normal, becoming 15-20 degrees above normal Thursday night.

Key message 2: Record high temperatures possible Friday ahead of another cold front. The front brings a chance of showers late Friday and Friday night.

Heights briefly rise Friday as an upper ridge axis expands eastward. A cold front then drops southward into the area Friday night. Little to no Gulf moisture expected with low level westerly flow. There is enough moisture with the front for likely PoP across the mountains late in the day into the evening. Precip chances then increase across the I-40 and I-77 corridors where better moisture and forcing move through. The shortwave driving the front doesn't dig very far southward and is shunted off to the east. Any frontal wave that develops will be east of our area as well. Very little in the way of surface based instability develops, keeping any thunder threat to a minimum. Precip chances drop off significantly across the western Upstate and NE GA with the much of that area remaining dry. Even where PoP is higher, QPF will be light so that no significant drought relief is expected.

With the increasing heights, thicknesses, and westerly flow, high temperatures are forecast to break records at CLT and GSP and approach the record at AVL. Lows Friday night will be much colder than the previous night, but still near normal across the mountains and around 5 degrees above normal elsewhere. Precip should move out of the mountains before the colder temps arrive.

Key message 3: Cool, dry high pressure builds in for the weekend with moderating temps early next week.

A cool and dry airmass builds in behind the front on Saturday. Gusty northerly winds are expected with a tight pressure gradient between the departing cold front and high pressure over the Ohio Valley. Despite cooler temps, the airmass is so dry that RH values drop below 25% across the area. This could lead to increased fire danger given only light QPF is expected with the front Friday night. Highs will be up to 5 degrees below normal Saturday and 5 to 10 below normal Saturday night with a freeze for the mountains and portions of the NC foothills. This said, the first group of zones in the spring frost-freeze program (GA/SC zones outside the mountains and southern tier of NC Piedmont zones) do not activate until April 1.

The sfc high moves quickly off shore Sunday with temps moderating a few degrees; however, the developing southerly flow remains weak with no significant moisture recovery expected. RH values again drop below 25% but winds will be much lighter. A warming trend develops through Wednesday as the southerly flow kicks in and thicknesses rise with highs back to around 15 degrees above normal for Tuesday and Wednesday. Lows may be below freezing for the higher elevations Sunday night but will be near to slightly above normal elsewhere. Rising to 10 to 15 above normal by the end of the period. Frontal systems remain to our north and west through the period, but there could be enough moisture return for some diurnal showers across the mountains; however, this is more uncertain than the temp trends.

AVIATION /00Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: VFR conditions are forecast to continue through the period. SCT/BKN clouds in the 035-050 range will remain possible, especially tonight into Thu morning. Can't rule out some MVFR cigs developing toward sunrise, especially at the upstate SC terminals and KAVL, but confidence is low at this time. Mostly light S/SW winds tonight will become WSW at 10-15 kts with higher gusts from late morning into the afternoon Thursday (directions are expected to be NW at KAVL).

Outlook: A cold front may bring showers and associated restrictions, mainly to the mountains Friday afternoon into Friday night, but confidence is low as moisture with the front looks limited. Breezy winds associated with the front will linger through Saturday afternoon. Dry and VFR conditions return behind the front this weekend.

CLIMATE

RECORDS FOR 03-27

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 85 2020 32 1955 60 1921 11 1955 1894 KCLT 85 1950 40 1894 62 1949 19 1955 1944 KGSP 86 2020 45 2011 60 1921 15 1894 1947

GSP WATCHES/WARNINGS/ADVISORIES

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