textproduct: Columbia

WHAT HAS CHANGED

Minor adjustments made to Key Message 2 to reflect recent trends in the guidance. Aviation discussion updated for 18z TAF issuance.

KEY MESSAGES

- 1. High confidence in above normal temperatures over the next several days.

- 2. Limited rain chances early this week. However, a pattern shift mid to late week may lead to increasing rain chances into next weekend.

DISCUSSION

Key Message 1: High confidence in above normal temperatures over the next several days.

Confidence remains high in the temperature forecast over the next week, as offshore high pressure takes center stage and keeps our weather fairly benign. Upper troughing in the west will force amplification of the ridge over the eastern CONUS over the next several days as the storm track remains well to the north. In response, increasing heights and thicknesses will lead to above normal temperatures for mid-May with highs in the low 90s through at least Wednesday. The offshore high will also remain quasistationary, and southerly flow should continue to feed a steady stream of moisture into the region with dewpoints in the low to mid 60s much of the week.

Key Message 2: Limited rain chances early this week. However, a pattern shift mid to late week may lead to increasing rain chances into next weekend.

Scattered cumulus have developed across much of the FA this afternoon, with more robust development ongoing to the south over southeastern and south-central Georgia. A tongue of anomalously high PWATs is moving north through Georgia with values in excess of 1.4 inches west of the Savannah River. The primary failure mode for thunderstorms this afternoon continues to be a capping inversion over the region, which may restrict development to our far southwestern CWA, especially from Thomson to Midville in Georgia. Should any robust convection develop, there is sufficient DCAPE in place that damaging wind gusts would be the primary hazard. Because our freezing level is over 14000 feet, any hail should remain below severe limits and there is a near zero tornado threat.

After today, the chance for rain remains low Monday, Tuesday, and most of Wednesday. Attention then turns to a slow moving front which may arrive late Wednesday. This boundary, along with better moisture (PWAT values between 1.5" and 1.8"), and a couple weak shortwaves may bring an increase in rain chances lasting Thursday into the upcoming weekend.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR conditions expected the remainder of today with brief restrictions possible again Monday morning.

FEW to SCT cumulus are seen across the region this afternoon with 4- 8 kt winds out of the south to south-southeast. These conditions should continue the remainder of the afternoon and into this evening, though there has been a slight shift in guidance in terms of potential thunderstorms mainly between 20z-00z. More model guidance has shifted isolated storms nearing AGS/DNL later this afternoon, but uncertainty remains in if these storms will develop due to a lingering cap aloft from the ridge in place. Due to this shift in guidance, have added a PROB30 group for AGS/DNL. It is possible any storms extended further east, but confidence in this is low. Tonight, passing cirrus are expected with light 2-4 kt south to southeasterly winds. With lingering low level moisture, previous runs of LAMP and HRRR guidance showed a mix of fog and stratus developing tonight after 07-09z. LAMP guidance has backed off on the potential cig restrictions recently, but the mean HREF solution remains more aggressive with probabilities for ceilings less than 1000 ft nearing 40-60%. A 20-25 kt LLJ should be in place once again tonight, which may limit vsby restrictions a bit more, but at this time, periods of MVFR vsby or cig restrictions seem possible mainly from 08z until around 13z. Trends will need to be watched to determine if more impactful restrictions become likely. After 14-15z Monday, light winds should pick back up out of the south-southeast with clearing skies.

EXTENDED AVIATION OUTLOOK...Increased moisture may result in brief restrictions at the terminals due to low clouds and/or fog each day this week. Rain chances increase towards the end of next week.

CAE WATCHES/WARNINGS/ADVISORIES

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