textproduct: Columbia

WHAT HAS CHANGED

Minor changes to the key message. Aviation discussion updated for 18Z TAFs.

KEY MESSAGES

- 1. A typical summer pattern expected this week with increasing moisture and warming temperatures during the mid to late week period.

DISCUSSION

Key Message 1: A typical summer pattern expected this week with increasing moisture and warming temperatures during the mid to late week period.

While dry surface high pressure and deep ridging aloft will control the pattern, moisture returns with southwesterly flow across the area today. The pattern synoptically will not change all that much each day, with 90th percentile heights expected throughout much of the period. Rain chances hold off until Monday, when we reach sufficient low level moisture for diurnally driven showers and thunderstorms. The clouds and rain should result in lower daytime temperatures on Monday and especially Tuesday before we see high temperatures return to the 90s during the mid to late week period. Scattered daytime showers and thunderstorms are expected most days this week with a fairly typically summer pattern in place. The combination of heat and humidity could result in our first days of heat index values at or above 100 degrees, though still below heat product criteria. With the ridge in our vicinity, significant rainfall is unlikely. While PWAT's should climb above 1.75", QPF totals across all guidance is generally only 0.25-0.75" with some isolated higher amounts in areas that see repeated rounds of thunderstorms.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR conditions likely through the TAF period.

SCT cirrus continues overhead this afternoon, with any VFR cumulus dissipating after sunset. Low-level moisture will continue to increase tonight as high pressure shifts farther offshore. Winds will diminish this evening and become light overnight. With the clouds and light wind, fog is not expected.

Light southwesterly winds Monday will increase to around 5 to 8 kt by late morning and continue into the afternoon under BKN to OVC cirrus. A weak cold front approaching from the west may bring isolated afternoon showers/storms later in the period. However, confidence remains too low for inclusion at this time.

EXTENDED AVIATION OUTLOOK...Moisture increases heading into the workweek leading to scattered, mainly diurnal, showers and thunderstorms starting on Monday.

CAE WATCHES/WARNINGS/ADVISORIES

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