textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 18z TAFs. Key messages remain largely the same.

KEY MESSAGES

- 1. Dangerous heat expected to develop this weekend, continuing into next week. Additionally, guidance continues to signal an impactful and intense heat event developing by the end of next week.

DISCUSSION

Key Message 1: Dangerous heat expected to develop this weekend, continuing into next week. Additionally, guidance continues to signal an impactful and intense heat event developing by the end of next week.

Heat will be the dominant weather storyline over the next 7-10 days, with a long duration period of intense heat expected through the foreseeable future. An intense upper level ridge is forecast to develop over the next several days. This will first appear as a subtropical ridge, extending from the central Atlantic across Florida and into the Gulf. As an intense trough digs into the intermountain west, this will help to amplify the upper level ridge and establish it across the MS/OH/TN River Valleys to our northwest. Heat and humidity is forecast to continue building through Monday, with heat index values rising to near Heat Advisory criteria both Saturday and Sunday. A thermal trough is likely to be induced across the area both Sat/Sun, which should act as an impetus to force scattered afternoon showers/storms. This may help manage heat index values, but strong storms appear possible both days with CSU ML probabilities highlighting the area in an elevated risk for damaging winds in any strong storm.

Showers/storms will remain possible Monday, especially across the southern Midlands and CSRA as a low-end backdoor front sets up across the area. This is forecast to usher in a brief "reprieve" from the heat of Saturday and Sunday as slightly lower dewpoint air pushes in from the northeast. As usual, the blended guidance looks slightly too high with dewpoints through much of the period, which will impact overall heat indices a bit. Still, though, it will remain very warm during this period. Mid to upper 90s are expected Monday and Tuesday. 500 hPa heights well into the 90th percentile will be driving this, and this will help set the stage for the heat that is expected later in the week.

Guidance continues to show a favorable synoptic scale pattern for an intense heat wave next week. This will likely begin to establish itself at the tail end of this period, stretching into the July 4th weekend. Its tough to comment on much beyond the D7 portion of this forecast period (Thursday, Jul 2); however, confidence continues to increase that intense heat will build by this point and persist into the Holiday Weekend. The synoptic pattern matches many of our more intense heatwaves, with an anomalous 500 hPa ridge building to our northwest and facilitating the advection of very high 850 hPa temperatures from the lee side of the Rockies eastward towards the Mid- Atlantic and Carolinas. Ensemble guidance across the board is showing ~70-80% probabilities of >20C 850 hPa temps arriving by Thursday, driving highs near 100F beginning that day. It appears that a relatively "dry" airmass will be in place, which just translates to "we probably won't have 70F+ dewpoints all day" this time of year. This should foster an effective mixing regime, which would align with what the blended and ensemble guidance is showing for forecast highs during this period. One thing to watch for in the coming days will be whether or not guidance points to any consistent signals for convection in this period. This will be a major modulating point for just how warm we get. While it is too early to speculate on just how hot we will be, from a pattern recognition perspective, confidence is growing that we will see long duration, intense heat overlap with a major holiday weekend beginning at the end of this forecast period. Please review heat safety tips now so that you are well prepared!

AVIATION /18Z THURSDAY THROUGH TUESDAY/

VFR conditions are expected to continue over the next 24 hours.

Area of low pressure across southwestern Ga this afternoon is helping to spread some broken mid and upper level cloudiness across the forecast area. This will continue through the afternoon, with even an isolated shower not entirely out of the question across the CSRA. May see some scattering out of clouds this evening, then additional mid and upper level broken clouds will be pushing into the CSRA after midnight, and into the Midlands by morning. Ceilings remaining vfr through the period though. Winds will be south to southwesterly around 5 knots through the evening, then turning light to calm overnight. A return to southerly winds around 5 knots then expected for Friday. There is a small chance for near sunrise restrictions mainly for fog prone AGS/OGB but confidence is too low to include in TAF.

EXTENDED AVIATION OUTLOOK...Increasing heat and humidity into this weekend should yield daily diurnal convection and possible associated restrictions. The best chances for these showers/storms is Friday afternoon and Sunday. Brief morning vsby restrictions also possible into this weekend and early next week.

CAE WATCHES/WARNINGS/ADVISORIES

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