textproduct: Columbia

WHAT HAS CHANGED

Updated for 12z TAF forecast.

KEY MESSAGES

1. Dense fog this morning across the area.

2. Significant temperature drop from Sunday to Monday as wedge conditions develop.

3. Well above normal temperatures and unsettled weather late week.

DISCUSSION

KEY MESSAGE #1: Dense fog this morning across the area.

With clear skies and light winds, temperatures dropped quickly with favorable radiational cooling early this morning. Lingering low level moisture is in place which is leading to the development of dense fog with observations showing visibility of a quarter mile or less in some locations. Dense fog advisory remains in effect until 10am.

KEY MESSAGE #2: Significant temperature drop from Sunday to Monday as wedge conditions develop.

Lingering fog this morning will dissipate leading to mostly clear skies this afternoon. Forecast soundings indicate the top of the inversion is around 15C, and with increased mixing with plenty of sunshine today, temperatures expected to rise to well above average with high confidence in highs in the mid to upper 70s. Tomorrow, strong surface high (Around 1040mb) expected to shift into the Northeast with increased winds over the forecast area out of the northeast and rain, mainly north of the area expected to strengthen cold air damming. While there remains uncertainty in the high temperature forecast, hires model guidance, which typically performs better in these situations is below the nbm 10th percentile. As a result, went below blended guidance for highs Monday but may not have gone quite low enough with possible that portions of the area remain in the 40s through the day with breezy northeast winds and widespread low clouds.

KEY MESSAGE #3: Well above normal temperatures and unsettled weather late week.

High pressure will shift offshore for the second half of the week with strengthening upper ridging with NAEFS mean indicating 500mb heights above the 90th percentile. This will lead to well above average temperatures with blended guidance showing high confidence in highs in the upper 70s to low 80s and lows in the upper 50s to low 60s through the end of the period. Unsettled conditions possible for the end of the week with increasing moisture with the GEFS and ECMWF ensemble means showing PWATs rising to around 150-200% of normal. In addition, with well above average temperatures, increasing potential for destabilization leading to the potential for thunderstorms with GEFS probability of greater than 500 J/kg surface based CAPE around 60 percent each afternoon Thursday through the weekend.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Widespread IFR/LIFR restrictions in fog this morning then VFR conditions expected.

Favorable environmental conditions fostered widespread dense fog development across the area. Fog should dissipate by 14-15z as mixing takes place and VFR conditions return through the remainder of the day as calm winds pick up a bit from the southwest as the surface high shifts southeast of the region. A backdoor cold front will push into the area late tonight and may result in cig restrictions in stratus near the end of the forecast period.

EXTENDED AVIATION OUTLOOK...Wedge conditions expected to develop on Monday with restrictions in low clouds expected through Tuesday.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Dense Fog Advisory until 10 AM EST this morning for SCZ016-018- 020>022-025>031-035-037-038-041-115-116-135>137. GA...Dense Fog Advisory until 10 AM EST this morning for GAZ040- 063>065-077.