textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Adjusted precip chances for the cold front Friday night.

KEY MESSAGES

1. Very dry conditions this afternoon, with widespread critical relative humidity. A Fire Danger Statement is in effect for Upstate South Carolina and northeast Georgia through 8 PM EDT. Temperatures moderate back to above normal by Thursday. 2. Near-record high temperatures 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: Very dry conditions this afternoon, with widespread critical relative humidity. A Fire Danger Statement is in effect for Upstate South Carolina and northeast Georgia through 8 PM EDT. Temperatures moderate back to above normal by Thursday.

Flat west to northwesterly flow aloft will continue this afternoon as a 1034mb surface currently situated over the OH Valley and Lower Great Lakes keeps the flow east to northeasterly at the surface. As a result, very dry air aloft has developed a strong subsidence inversion which has allowed for RH values to plummet below 25% over the higher elevations, in particular between 2500'-4500' this afternoon with single digit to below zero dewpoints. Boundary layer mixing is starting to cause RH values to dip below 40% elsewhere as temperatures rise into the 50s and dewpoints remain in the 20s. However, deep subsidence inversion atop the boundary layer should help to limit further dewpoint mixing and thus, lower RH values. Winds have remained relatively light with sporadic low-end gusts up to 15kts, helping to limit conditions from reaching Red Flag Warning criteria, but with ongoing drought conditions and RH values still forecasted to dip around 25% this afternoon, a Fire Danger Statement remains in place through 8 PM EDT this evening for Upstate SC and northeast GA. Much cooler temperatures are expected as well with a passing backdoor front well to the south and a drier and cooler airmass settling in. Factor in a few mid/upper-level clouds streaming overhead as a shortwave passes over the area and afternoon highs will run 5-10 degrees below normal. Good radiational cooling conditions will be in store for tonight with only high clouds possible and light winds, leading to overnight lows dipping a few ticks below normal tonight.

Surface high shifts over the Mid-Atlantic Coast tonight and develops an in-situ type of synoptic look, but the flow turns more out of the south and southeast later on Wednesday, which keeps it from becoming true cold air damming. 850mb ridge will breakdown Wednesday and shift towards the Southeast Coast, allowing for the low-level flow above the surface to turn out of the southwest. An increase in stratocu and mid-level clouds are possible Wednesday afternoon, but guidance has backed off on any precip. Still expect temperatures to rise compared to Tuesday by a few degrees, but still a tick or two below normal. An upper anticyclone over the Southern High Plains will slowly propagate eastward and allow for rising heights over the area on Thursday with continued south to southwesterly flow in the low-levels. This should help allow temperatures to rise well into the mid and upper 70s for afternoon highs.

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

A weak, surface high pressure ridge slides south of the area Friday as a cold front approaches from the north. This keeps a westerly low level flow over the area with little to no Gulf moisture inflow ahead of the front. There will be enough moisture for showers to develop across the mountains late in the day. The best forcing slides eastward Friday night as the driving shortwave doesn't dig very far south. All this contributes to the better precip chances remaining limited to the NC mountains and I-40 corridor. Chance PoP does develop for the I-77 corridor but drops off rapidly across the western Upstate and NE GA. Even where the better PoP is, QPF remains light which won't help mitigate drought conditions very much. SBCAPE remains weak as well, limiting thunder chances. Highs will threaten records at CLT and GSP with increasing thickness values and westerly flow.

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

Highs will be around 5 degrees below normal Saturday rising to around normal for Sunday as cool and dry high pressure builds in behind the departing cold front. Saturday night will be the coldest night with lows 5 to 10 degrees below normal, below freezing across the NC mountains and portions of the I-40 corridor. 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.

High pressure slides eastward early next week with a southerly flow developing and a warming trend with highs 10 to 15 degrees above normal by Tuesday.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

At KCLT and elsewhere: VFR conditions will prevail through the forecast period. Earlier cloud cover has shifted east of the terminals leading to FEW250/SKC with east to northeasterly winds at 5-10 kts and the occasional low-end gust. Winds will subside after 00Z as a gradual increase in VFR cloud cover is expected. Winds will begin to toggle to an east to southeasterly component overnight into Wednesday morning, while remaining under 5 kts. A slight increase to 4-8 kts expected by Wednesday afternoon with winds toggling more to a south to southeasterly component. SCT/BKN cloud cover should stick around through the end of the TAF period, but remain VFR.

Outlook: VFR conditions continue through most of the week. Rainfall and associated restrictions may return by Friday as a cold front crosses the area, but confidence is limited.

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.