textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated for new Aviation Discussion.

Added a mention of patchy dense fog for tonight/early Tuesday.

KEY MESSAGES

1. Patchy dense fog will be possible late tonight and early Tuesday morning. Generally dry through Wednesday. Above-normal temperatures through the workweek, trending warmer through Friday. 2. Small chances for rain return late Wed into Thu as the next system approaches the area. Rain chances continue into this weekend, as temps trend cooler.

DISCUSSION

Key message 1: Patchy dense fog will be possible late tonight and early Tuesday morning. Generally dry through Wednesday. Above-normal temperatures through the workweek, trending warmer through Friday.

The center of high pressure over the Coastal Plain of the Carolinas this evening will drift off the Southeast Coast on Tuesday. Meanwhile, a 925-700mb ridge will shift east tonight through Tuesday. These changes will permit increasingly deep southwesterly low to midlevel flow, and gradual height rises aloft, promoting a slow upward trend in afternoon max temps through Wednesday; maxes in the Piedmont and mountain valleys will be in the 60s, 5-10 degrees above normal.

With the sfc high being centered overhead tonight and skies remaining mostly clear, strong radiational cooling is expected, and crossover temps are within reach. The recent rainfall provides the opportunity for fog to develop late tonight, and some localized areas of dense fog with 1/4 mile visibility or less will be possible late tonight into Tue morning; greatest potential looks to be between I-85 and the Blue Ridge Escarpment.

The warming trend toward midweek will be more noticeable in terms of min temps, with winds remaining southwesterly and pressure gradient tightening between the offshore sfc high and the sfc/upper low moving into the Upper Midwest, keeping winds up overnight. Warm front associated with that system effectively crosses the area late Tue night or early Wed, so fog/stratus development remains possible and would also help buoy overnight temps. As that system occludes its cold front looks to stall and reverse over the TN Valley, as next low develops in the lee of the central Rockies. Small 20-30% PoPs are forecast Wed night and early Thu with abundant cloud cover. Current forecast mins Wed night challenge the record high-mins at GSP and CLT, with aftn maxes Thu just shy of records in the current forecast and suggesting temps remain above the hi-min through midnight Thu night. Record max temps also appear possible Friday.

Key message 2: Small chances for rain return late Wed into Thu as the next system approaches the area. Rain chances continue into this weekend, as temps trend cooler.

After a relatively dry week, model guidance hints at a potential pattern change going into the weekend. Leading up to Friday, the overall pattern looks benign as the mid-level air remains quasi zonal and surface high pressure off the east coast continues to amplify. However, a few of the models in the long range depict a weak fujiwhara effect of two areas of low pressure over the upper Midwest, throwing a kink in the 500mb flow. Though the sfc lows themselves have no direct effect on the CWA, the associated cold front looks to stall near the southern Appalachians Wed night, and is reactivated as a warm front ahead of the next area of low pressure ejecting out of the Rockies, bringing the next chance for precip by early Thursday morning and generally increasing from there. Currently, this is where the models disagree and confidence lowers as where the system traverses will have a direct impact on downstream precipitation. For the current forecast, rain chances appear to be higher over the mountains, so keeping PoPs in the 50% to 70% range Thursday night into Friday. At this time, the probability for an inch or more of rain in a 24 hour period this weekend is about a 20-30% on Sunday. This will change but so far, doesn't look to be a highly impactful hydro event. After the potential system lifts to the north, the model guidance diverges on agreement of the next bout of rain over the weekend. Confidence this far out is too low for any details but once the rain moves out, colder and drier air look to be ushered in. Guidance dips temperatures into the normal or just below normal range to end the weekend and start the new week.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: VFR through late tonight at all terminals, then we look for fog development across the region in the pre-dawn hours given mostly clear sky and light wind. Guidance develops fog around most terminals right around daybreak but confidence is average at this point, if only because dewpoints mixed out enough around the time of peak heating to suggest that we might not reach the crossover temp threshold for fog development. Will include a mention of fog in most places for the time being as a placeholder and then will monitor the trends for the 06Z issuance. After the fog mixes out, more clear sky on Tuesday, with a light S to SW wind.

Outlook: Nocturnal fog/stratus can't be ruled out near daybreak Wed or Thu. Otherwise VFR through midweek. Rain may return to the area by Thursday or Friday.

CLIMATE

RECORDS FOR 02-18

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 72 1897 15 1958 55 1891 0 1958 KCLT 78 2011 25 1979 62 1891 5 1958 1891 KGSP 78 2011 26 1979 55 1975 2 1958

RECORDS FOR 02-19

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 72 2014 16 2015 54 1951 3 2015 KCLT 76 2014 26 2015 55 1961 8 1958 1939 KGSP 75 2014 30 2015 55 1961 9 1958 1916 1900 1900 1911

RECORDS FOR 02-20

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 75 1939 26 1908 54 2018 4 2015 KCLT 77 2014 31 2015 59 1939 7 2015 1890 KGSP 75 2014 33 2015 57 1939 9 2015 1986

GSP WATCHES/WARNINGS/ADVISORIES

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