textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Decreased RHs for Monday afternoon along with increased winds, with IFD for the Piedmont.

Confidence is increasing for near freezing overnight temperatures possible next weekend, mainly for the mountains.

KEY MESSAGES

1. A cold front will push through the area Monday bringing some showers to the mountains tonight, though temperatures will remain above-normal. Increased fire danger on Monday afternoon with a drier airmass and breezy conditions. 2. Much cooler temperatures and dry conditions return Tuesday through the middle of the week. 3. A cold front could cross the area next weekend with another round of cooler air and increased rain chances.

DISCUSSION

Key message 1: A cold front will push through the area Monday bringing some showers to the mountains tonight, though temperatures will remain above-normal. Increased fire danger on Monday afternoon with a drier airmass and breezy conditions.

A shortwave will dive into the Appalachians tonight, dragging a mostly-dry cold front across the Southeast. Moisture associated with the front is paltry especially along the tail end, but upslope flow into the mountains as the front approaches will be enough for a few showers along the TN border late tonight and approaching daybreak Monday. Across the foothills and Piedmont, profiles dry out rapidly, with enough for some Cu to develop along the front but no showers expected. CAA will build in as the front sweeps through, counteracted by the downsloping in the NW to N flow at the surface. Temperatures on Monday are expected to remain well above-normal, though several degrees cooler than the near record (or record) highs this afternoon. With the timing of the front, some areas in the mountains may see an early morning high, with near-steady tempertures the rest of the day, and likely some areas in the foothills and NW NC Piedmont may see a midday max temp, slowly falling through the afternoon.

Other issue of note is the drier dewpoints advecting in with the front, enhanced by diurnal mixing (though the mixed layer only extends to 850-800mb), combined with breezy NW winds enhanced by typical post-frontal gap effects. RHs will drop below 30% across most of the Piedmont, with the exception being the Lakelands, and winds 10-15kt may gust up to 25kt. With this, most of the Piedmont is right at criteria for Increased Fire Danger statement, and after coordination with surrounding offices and land managers, have opted to issue one for Monday afternoon.

Key message 2: Much cooler temperatures and dry conditions return Tuesday through the middle of the week.

Behind the front, surface high pressure sets up across the eastern CONUS and slowly migrates eastward through Thursday. As high pressure moves over the northeast, a return of a weak CAD ensues. Surface winds become more northeasterly Tuesday and gradually breaks down through Thursday. Despite the CAD setup, current guidance keeps rain chances at bay and this should have no major impacts to the forecast, other than reinforcing cooler temperatures Tuesday and Wednesday. As winds veer southerly, moisture ticks up Wednesday and so do the temps ahead of the next frontal passage.

Key message 3: A cold front could cross the area next weekend with another round of cooler air and increased rain chances.

By Friday, guidance has another stout ridge over the southern zones, allowing for NW flow aloft to return to the southeast. At the surface, a robust area of high pressure appears to spill out of Canada and into the central CONUS. This frontal boundary makes a run for the CWA on Friday and into Saturday. Guidance tries to activate shower activity, with higher chances (40-50%) across the mountains and slight chance (20-40%) elsewhere. For current trends, temperatures appear to be too warm to support any frozen precipitation at the current forecast, but this could change. There still remains a very low (<15%) chance that should colder temps come in quicker, a brief NW flow snow burst is possible, though little to no accumulations would occur. Behind the front, a return to more seasonable temps. Overnight temps could reach the freezing mark for the weekend, with Saturday night having the better chances: 30-40% for the mountains and 15-25% for the NC Piedmont. This is likely to change, but as of now, the signal for a widespread freeze hoists a much lower confidence.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Winds will diminish only somewhat this evening, staying around 8-10 kt east of the mountains overnight. Westerly to WSW flow around 1500-2000 ft AGL will approach 40 kt, especially across NC, so have added LLWS at KCLT and KHKY in the overnight/early morning time frame. Then winds will pick up and veer to nearly due W before a cold front bring them around out of the NW around 14-15z Monday morning. Little moisture expected with the front, but could see MVFR cigs at KAVL Monday morning. Confidence still too low to mention in the TAF. Otherwise, high-based Cu expected during the day Monday, with clearing skies late aftn into the evening. Winds will be gusty thru the rest of the period, veering to more NLY or NNELY by Monday evening.

Outlook: VFR through Tuesday. Some restrictions may develop Tue night with moist frontal zone forming over the area. Diurnal convection possible later in the week.

CLIMATE

RECORDS FOR 03-22

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 86 1907 32 1915 58 1991 15 1965 KCLT 89 1907 38 1883 64 1948 24 1965 KGSP 85 1935 42 1985 62 1948 20 1906 1914

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...INCREASED FIRE DANGER from Monday afternoon through Monday evening for NCZ035>037-056-057-068>072-082-502-504-506- 508-510. SC...INCREASED FIRE DANGER from Monday afternoon through Monday evening for SCZ008>014-019-101>109.