textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated for 00z aviation discussion.

Patchy frost has been added to more of the mountain valleys for early Monday morning.

Rainfall amounts for the middle of the week system continue to trend slightly higher with this issuance, but the low threat for severe weather is unchanged.

KEY MESSAGES

1. Patchy frost will be possible early Monday morning in some sheltered locations in mountain valleys. People should consider protecting sensitive plants again tonight across the NC mountain valleys. 2. Another cold front will bring rain to the area during the middle part of the upcoming week. The signal for beneficial rain, at least for the mountains, continues to improve. The threat for severe weather with this system still appears relatively low, but remains worthy of monitoring.

DISCUSSION

Key message 1: Patchy frost will be possible early Monday morning in some sheltered locations in mountain valleys. People should consider protecting sensitive plants again tonight across the NC mountain valleys.

Sfc high pressure overhead today will essentially re-center itself off the Carolina Coast tonight, but radiational conditions will be very good under clear sky and with light/variable or calm wind. However, modification of the air mass will keep low temps on the order of 3-5 degrees warmer than this past morning, limiting the threat of frost outside the mountains. Temps will still get cold enough in some parts of the mountains, and valley locations stand the best chance, especially places that are normally sheltered anyway. The new forecast will feature some frost especially in parts of the French Broad River valley and Little TN River valley, but the coverage is not great enough to issue another Frost Advisory for tonight.

Otherwise, the weather should be fairly quiet for Monday and Tuesday under a flat confluent flow aloft and with high pressure off the coast allowing for some advection of moisture and warmth toward the middle of the week. This should temps to return to within a category of normal but on the cool side for Monday, and then back to normal on Tuesday. The afternoon RH both days should stay around or above 30 percent.

Key message 2: Another cold front will bring rain to the area during the middle part of the upcoming week. The signal for beneficial rain, at least for the mountains, continues to improve. The threat for severe weather with this system still appears relatively low, but remains worthy of monitoring.

Subtle changes are seen in the guidance as we get out into the middle part of the week with regard to a mid/upper trof moving east across the Plains on Wednesday and its affect on a slow moving cold front over the OH Valley/mid-MS Valley regions. We still have a favorable setup for moisture return from the Gulf ahead of the system with persistent but retreating high pressure off the East Coast, which is a welcome sight in the model guidance. One trend is for the main short wave to make slower eastward progress with less amplitude, which might serve to prolong our rainy period, which in this case would not necessarily be a bad thing. The new forecast will feature a longer period of likely/categorical precip probs Wed/Thu. The probabilistic guidance from the model blend also shows the chances of getting at least an inch of rain over the mtns/western Upstate/northeast GA mountains has increased to 40-60 percent. However, the high chances might not translate eastward across the NC Piedmont, as there is now some indication in some of the guidance of a split occurring, with better precip moving from east TN up into western VA, and another batch moving east with deep convection from GA into the Midlands, essentially missing us to the south. We'd still get some rain, but not all that much. We shall see how these trends move in the next day or so. As for the severe weather chances, they appear about the same as they did this time yesterday, mainly focused on the area from the Lakelands to the southern part of metro CLT Thursday afternoon. We still have a joint prob around 30 pct of sfc-based CAPE above 500 J/kg and deep shear above 30kt. The Day 4/Wed outlook has the risk area well to our west, though some of the NCAR AI guidance shows that risk area nosing into the Upstate. Also, there's no SPC risk area for Day 5/Thu but the AI guidance shows some possibilities in eastern NC. Essentially this indicates a timing issue for the western Carolinas, so any speeding up or slowing down of the system could easily improve our chances for severe storms. Worth monitoring.

A brief cool-down can be expected behind this front for Friday, nothing too extreme, but about ten degrees below normal. Temps rebound for the weekend. Another system may affect our region Saturday/Sunday.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR conditions will prevail at all terminals through the TAF period. Clear skies continue overnight with light and variable winds. Winds remain out of the southwest tomorrow with another round of afternoon gusts beneath mostly sunny skies with no restrictions.

Outlook: Expect dry/VFR conditions to linger through the first half of the week. Restrictions are possible with next frontal system Wednesday and Thursday.

GSP WATCHES/WARNINGS/ADVISORIES

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