textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for the 00z TAF issuance.

KEY MESSAGES

- 1. A frontal system brings increased rain chances and cooler temperatures later in the week.

DISCUSSION

Key Message 1: A frontal system brings increased rain chances and cooler temperatures later in the week.

Low dewpoints, light winds, and mostly clear skies will promote large diurnal temperature ranges, with below-normal overnight lows in the low to mid 40s expected tonight. Have adjusted temps downward by 1-3 F tonight and Monday night from NBM guidance to account for decent radiational cooling from mostly clear skies and light winds. As the surface high gradually shifts southward, light southerly flow will allow temperatures to steadily rebound through midweek. Dry conditions will continue to support large diurnal temperature swings, with widespread highs in the mid to upper 70s and overnight lows in the 40s.

Attention will then turn to a complex and deep upper-level trough/low expected to dig across the eastern US late this coming week, bringing cooler temperatures in its wake. Global models continue to show disagreement regarding the placement and intensity of surface development across the southeast. Recent deterministic GFS runs have remain farther southwest and slower with the placement and progression of the shortwaves than the majority of guidance, but now shows two distinct shortwaves swinging across the southeast up the East Coast rather than the complete phasing shown in previous runs. This focuses the greatest potential for precip off the East Coast and to the north of our area across the Appalachians. Any associated frontal system is most likely to bring increased precip chances to the region Thursday into Friday, but accumulations will be light, with only around 20% of LREF members showing 24 hr QPF greater than 0.10 inches. Behind the system, much cooler conditions are expected late next week. Temperatures are currently forecast to run around 5 to 10 degrees lower than normal. Overnight lows in the mid to upper 30s are appearing more likely, and 40 to 70% of LREF members show of temps dipping below 35 by Saturday night, raising potential for the first frost of the season.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Primarily VFR conditions, with shallow patchy ground fog possible towards morning causing brief visibility restrictions.

Dry high pressure remains. As the low-level inversion sets up overnight, winds will be mostly calm at taf locations. There will be a weak jet between 10-15 knots above the inversion, but no issues with any kind of llws overnight. Once the inversion breaks, could see a brief period of gusty winds between 5-9 knots, but that quickly diminishes and winds fall back down being more light and variable through the day.

Most areas should remain vfr. However at sites closer to rivers, can not rule out some shallow patchy ground fog developing, causing brief visibility restrictions, especially at AGS/OGB. Guidance continues to show mainly vfr overnight, and any visibility restrictions would be very limited, so have kept mention out of tafs for now.

EXTENDED AVIATION OUTLOOK...Dry air will likely prevent widespread restrictions through the extended with moisture increasing Thursday.

CAE WATCHES/WARNINGS/ADVISORIES

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