textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No significant changes to forecast trends.

KEY MESSAGES

1. The threat of patchy frost remains across the mountains tonight, and possibly east across the I-40 corridor Tuesday and Wednesday night. Protection of sensitive vegetation may be required in some locations. 2. Fire weather will gradually become more of a concern through mid-week as a dry air mass spreads across the region. Outdoor burning could become dangerous by Wednesday due to low relative humidity values, gusty winds, and dry fuels.

DISCUSSION

Key message 1: The threat of patchy frost remains across the mountains tonight, and possibly east across the I-40 corridor Tuesday and Wednesday night. Protection of sensitive vegetation may be required in some locations.

Cooler and drier weather will be in store through the first half of the week as high pressure builds in from the northwest. A weak, dry cold front will swing across the CWFA tonight to help reinforce the cooler and drier air. Boundary layers will struggle to fully decouple tonight despite temperatures reaching close to frosty levels, especially over the mountains. Some patchy frost is possible in sheltered mountain valleys, but not widespread enough to warrant a Frost Advisory. Overnight lows will be in the 30s across the higher terrain and 40s elsewhere.

The surface high will move over the Great Lakes and into northeastern CONUS Tuesday into Tuesday night. The temperature forecast remains relatively the same with afternoon highs near-normal and overnight lows reaching a category or two below normal. Frost potential remains patchy Tuesday night due to a tighter pressure gradient despite cooler temperatures compared to tonight, with likely the same sheltered valleys having the best Frost potential. The surface high should slip offshore the Northeast Coast Wednesday into Wednesday night and allow for the pressure gradient to relax some. With the cooler and drier airmass still in place, patchy frost development will be possible across the mountains and I-40 corridor as temperatures cool into the low to mid 30s, which will be the best night for a potential Frost Advisory. The northern mountains haven't started the Frost/Freeze program and won't until April 21st. Otherwise, expect dry conditions through at least Wednesday night.

Key message 2: Fire weather will gradually become more of a concern through mid-week as a dry air mass spreads across the region. Outdoor burning could become dangerous by Wednesday due to low relative humidity values, gusty winds, and dry fuels.

Most parts of the western Carolinas and northeast Georgia saw at least 0.25 inch of rain in the Friday to Sunday period, with the Smoky Mountains, upper Savannah River Valley, and a few swaths southeast of I-85 having substantially more. However, whatever mitigating effect that had on fuel moisture readings is likely to be short-lived. High pressure is already nosing into the area from the west. Modest diurnal mixing will continue this afternoon, and with airmass modification Tuesday deeper mixing should occur which will maintain critically low minimum RH of 25-30 percent in many locations. The dry pattern is reinforced as a Canadian high builds in from the north tomorrow night and Wednesday. Winds will turn N to NE, becoming breezy and occasionally gusty overnight into Wed morning. As these winds advect much drier air to the low levels, low minimum RH remains likely Wed afternoon even as temperatures trend cooler, and mixing depth is limited by a subsidence inversion. Brief overlap of critical RH with winds is possible for a time Wed, and may warrant issuance of an Increased Fire Danger Statement if confidence increases. Temperatures moderate somewhat on Thursday and the high drifts offshore, which still looks to result in slight Atlantic moisture fetch, so low RH is not as likely that day. However, warming temperatures will keep us close to that threshold into the weekend, with precip still looking quite unlikely through early next week as mid to upper level ridge builds overhead. Thus fuel moisture is likely to continue to remain low.

AVIATION /18Z MONDAY THROUGH SATURDAY/

At KCLT and elsewhere: VFR will prevail at all terminals through the forecast period. A steady stream of cirrus remains over the area through the rest of today and into tonight. Light north to northeasterly winds will continue through this evening, becoming light and variable overnight. A weak, dry cold front will move across the area by daybreak Tuesday and will shift winds due north and bring an uptick in speed at 5-10 kts. Better chance for low-end gusts are expected Tuesday afternoon with some high clouds still present.

Outlook: High pressure spreads over the region behind the cold front and lingers through the middle of week, with dry/VFR conditions expected through at least Thursday. Easterly flow may bring some return of lower clouds late Thursday into Friday.

GSP WATCHES/WARNINGS/ADVISORIES

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