textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated for the 00z aviation discussion.

KEY MESSAGES

1. A cold front will move east of our area tonight with drier and cooler air spreading over the region in its wake. 2. Frost still possible across the mountains and possibly a few parts of the North Carolina I-40 corridor each night from Monday night through Wednesday night. Protection of sensitive vegetation may be required Tuesday night and Wednesday night in some locations. 3. 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 afternoon due to low relative humidity values and dry fuels.

DISCUSSION

Key message 1: A cold front will move east of our area tonight with drier and cooler air spreading over the region in its wake.

Behind the front, robust CAA will allow a cooler and drier airmass to filter in, with lows tonight almost 20 degrees cooler than last night and slightly below early April normals. Sunny and beautiful day on Monday with highs very close to normal. With the dry airmass in place, RHs will drop into the 20 to 30% range across the area, but today's wetting rain will help with fuels.

Key message 2: Frost still possible across the mountains and possibly a few parts of the North Carolina I-40 corridor each night from Monday night through Wednesday night. Protection of sensitive vegetation may be required Tuesday night and Wednesday night in some locations.

Influx of colder air remains on track to commence tonight with NC mountain pre-dawn minimum temperatures in the 30s. Values around freezing will be limited to just the highest elevations. After the return to near climo maximums on Monday, a limited threat for frost development arises by early Tuesday morning for those NC mountain locations which can decouple, which typically means the deeper valleys.

As the center of a stronger high pressure center translates from the Great Lakes to the NE CONUS Tuesday, a reinforcing shot of colder air makes it way south into the region. Pre-dawn minimums both Wednesday and Thursday are still creeping upward and given the pressure gradient fcst to be in place, considerable mixing should limit any frost potential to just the deeper NC mtn valleys.

Note that the frost/freeze program remains inactive across the northern mountains of NC, so altho some parts of the nrn mountains might get below freezing Tuesday night, a freeze warning will not be issued and the fcst will be allowed to speak for itself.

Key message 3: 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 afternoon due to low relative humidity values and dry fuels.

Afternoon relative humidity values will likely tumble to below 30 percent each afternoon beginning on Monday. Thanks to an increasing pressure gradient, there is a risk of low amplitude easterly wind gusts developing Wednesday afternoon, but the risk for reaching red flag criteria remains low.

Beneficial rain today should keep fuels wet enough on Monday, but the dry air mass and a light NW to N wind should provide the opportunity for fuels to dry out through Tuesday afternoon. By Wednesday afternoon, even though high temps will drop compared to the previous two days, the low RH might become more problematic if fuels dry out as expected, because of better potential for wind gusts above 20 mph. Land managers will want to keep track of this forecast problem. Once the sfc high shifts farther offshore by Thursday, some Atlantic moisture should begin to return and afternoon RH rises accordingly.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Expect dry, VFR conditions thru the 00z taf period. All shower activity has moved east of our fcst area over the past couple of hrs with the cold front just now moving east of KCLT. Winds will become NWLY over the next few hrs and then NLY by the overnight. Expect gusts in the 20 to 25 kt range at KAVL thru the overnight with gusts subsiding by mid to late morning. The other terminals could see some sporadic low-end gusts thru the evening, but they should be intermittent. LLWS remains possible across the area overnight and into the morning, however it appears weaker per the latest guidance and was not included in the current set of tafs. Outside of the mountains, winds will eventually become light and VRB tomorrow afternoon with some sites favoring a NW to W direction. Otherwise, few to sct high clouds expected thru the period.

Outlook: Sfc high pressure spreads over the region behind the cold front and lingers thru the middle of week, with dry/VFR conditions expected thru at least Thursday.

GSP WATCHES/WARNINGS/ADVISORIES

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