Area Forecast Discussion

WHAT HAS CHANGED

* Backdoor front appears to be trending slower to move through Mon.

* Confidence continues to increase that dangerous heat will return mid-late week.

KEY MESSAGES

As of 115 PM Saturday...

1) Continued hot through Mon. A brief reprieve Tue-Wed, but then another heat wave is increasingly favored late next week.

2) Diurnally driven convection possible each day through next week, but overall coverage remains quite limited.

DISCUSSION

As of 115 PM Saturday...

KEY MESSAGE 1... Continued hot through Mon. A brief reprieve Tue- Wed, but then another heat wave is increasingly favored late next week.

The overall pattern is more or less unchanged through Monday as anomalously hot weather continues across the region. The low-level airmass hovers in the 1425-1430m range with respect to low-level thicknesses, well supportive of mid to upper 90s. The one exception may be over the western Piedmont, where highs largely top out in the lower 90s.

A backdoor front moves through sometime Monday. We mention Monday vaguely as it appears guidance has been trending a touch slower with its passage, perhaps sliding south during the day. As a result, highs should still hover in the low to middle 90s in most locations, with even a few upper 90s in the Triangle. Sunday still looks to be the warmest day of the next few days, getting close to the record high for RDU of 100 (see climate section).

A brief reprieve is expected in the heat Tue-Wed behind the backdoor front and as somewhat cool high pressure extends down from Delmarva. But this high quickly builds offshore midweek, resulting in well above normal temperatures to return late next week and the upcoming weekend.

The stretch from Thursday through Saturday is becoming increasingly favored for dangerous heat. Not only will the airmass be similar to this weekend, but dewpoints will also increase well into the 60s, increasing heat stress and heat-related illnesses. The HeatRisk category reaches a category 3 and 4 out of 4 Thu through Sat. This is in the major to extreme category, affecting anyone without cooling/hydration, as well as health systems, industries, and infrastructure. Additionally, the NBM probability of meeting or exceeding 100F is 40-60 percent during this stretch, particularly Fri-Sat over the Triangle, Sandhills, and Coastal Plain.

KEY MESSAGE 2... Diurnally driven convection possible each day through next week, but overall coverage remains quite limited.

Storm chances continue to trend lower for Sun ahead of a backdoor front that is expected to move through sometime Monday. Most CAM solutions indicate that as convection develops in east-central and southeast VA during the afternoon and evening, storms weaken with southward extent across the far northeast Piedmont and northern Coastal Plain of central NC. We still think a 20-percent chance is warranted in our northeast. SPC maintained a marginal risk of severe in SE VA within 2000 J/kg of MUCAPE and 30 kts of deep-layer shear. However, most of that instability wanes over NC, keeping our severe threat low.

The backdoor front appears to be trending slower to move through, perhaps during the day Monday. As a result, a differential heating boundary may set up from NE to SW, with the best chance of afternoon isolated to scattered storms along/south of the Triangle and south of US-64. We still feel coverage will be limited and diurnally driven. Instability will be favorable, but shear is weak such that any severe threat would only be confined to a few stronger pulse- type storms.

Overall, the coverage of storms Tuesday onward appears low, largely focused over western NC and the far western Piedmont along the western periphery of the ridge. Several ensemble solutions do indicate an uptick in diurnally driven storm chances toward the latter part of next week and weekend, perhaps in response to a frontal system, but that is largely uncertain at this point. Increasing low-level moisture and dewpoints may also be a contributing factor. Regardless, coverage of storms still appears limited at this stage.

AVIATION /18Z SATURDAY THROUGH WEDNESDAY/

As of 115 PM Saturday...

Favorable VFR conditions will persist across central NC terminals as high pressure remains over the Southeast coast. Expect only periods of high thin clouds and a few flat, daytime cumulus, with no visibility restrictions. Surface winds will stay out of the SSW to SW at 812 kts during the day, dropping to 8 kts or less tonight. However, expect occasional gusts of 1825 kts across the Piedmont, Sandhills, and Coastal Plain during the daytime hours.

Looking beyond 12z Sun, VFR conditions are likely to hold through at least Sun, as the high pressure sitting over the region shifts slowly E and offshore. A backdoor cold front settling into the area from the north will bring a few showers and storms Sunday evening and night across the N and E. Sub-VFR clouds are possible starting late Mon and persisting through Wed, but confidence in the details is low.

CLIMATE

Record High Temperatures:

June 6: KGSO: 96/2008 KRDU: 99/2008 KFAY: 99/1943

June 7: KGSO: 98/1925 KRDU: 100/2008 KFAY: 99/2008

June 8: KRDU: 101/2008 KFAY: 101/2008

June 11: KRDU: 100/1914

June 12: KRDU: 98/2002 KFAY: 99/1926

Record High Minimum Temperatures:

June 7: KGSO: 73/2008 KRDU: 74/2008

June 8: KGSO: 73/2008 KRDU: 75/1899 KFAY: 74/2008

June 9: KGSO: 72/2020 KRDU: 75/1993 KFAY: 77/2008

June 10: KRDU: 76/2020 KFAY: 77/2020

June 11: KGSO: 74/2008 KRDU: 74/2008 KFAY: 77/1981

June 12: KGSO: 72/1998 KRDU: 75/1986 KFAY: 76/2016

RAH WATCHES / WARNINGS / ADVISORIES

None.