textproduct: Raleigh

WHAT HAS CHANGED

* Severe weather chances today remain mostly unchanged, but there may be some additional low-end chance of strong to severe storms on Tuesday.

KEY MESSAGES

As of 230 AM Monday...

1) There is a Slight Risk of severe storms today, with the greatest threat generally across the northwest and northern Piedmont.

2) Heat will peak today with heat index values near 100-104F, mainly along and east of Highway 1. Hot weather possible again next weekend into early next week.

DISCUSSION

As of 230 AM Monday...

KEY MESSAGE 1... There is a Slight Risk of severe storms today, with the greatest threat generally across the northwest and northern Piedmont.

A strong shortwave trough will cross the Ohio Valley and Mid- Atlantic today, with a trailing cold front poised to cross central North Carolina tonight through early Tuesday. Moist southerly flow ahead of the front will send dew points into the mid-60s in the western Piedmont and near 70 further east, resulting in modest MLCAPE of 1000-1500 J/kg. While the belt of strongest mid-level flow is expected to remain north of the region, 20-25 knots of sfc-500mb bulk shear will support a severe threat. Scattered convection is expected to form along differential heating in the mountains or the lee trough, progressing eastward through the Triad and potentially the Triangle and northern Piedmont from 4-8 PM this evening. High- resolution guidance shows some variation in storm coverage; however, steepening low-level lapse rates and DCAPE up to 1000 J/kg across the Piedmont may support upscale merging of cold pools and a straight-line damaging wind threat as storms move off the mountains. The SPC currently has nearly all of Central North Carolina in a Slight Risk, with coverage maximized across the north.

An overnight lull should give way to renewed convection as the cold front and a potential MCV resulting from upstream convection (noted most aggressively in the HRRR) cross the area. With a highly focused area of lift ahead of the MCV, induced pressure falls, backing winds, and high pre-frontal moisture content, a conditional severe threat may emerge late Tuesday morning. This threat is primarily focused across the northern half of the area based on the forecast track of the MCV. This remains a low-confidence forecast as it is highly sensitive to todays upstream convection. Additional storms, which may not pose as much of an organized severe threat, are possible across southern counties later in the afternoon as the front sinks south.

QPF on this afternoon and evening generally ranges from a quarter to half an inch in the northern Piedmont to only a few hundredths in the far SE. However, HREF LPMM indicates isolated higher amounts of of 1-2 inches can't be ruled out with any storms, with some run-to- run consistency suggesting the best chances across the Triad.

KEY MESSAGE 2... Heat will peak today with heat index values near 100-104F, mainly along and east of Highway 1. Hot weather is possible again next weekend into early next week.

With highs in the low to mid 90s and increasing surface dewpoints into the mid 60s to around 70, heat index values will peak in the upper 90s to low 100s, mostly from the Triangle south and eastward. The NWS experimental Heat Risk does reach the Major category (level 3 of 4) in spots around the Triangle down to the Sandhills and S Coastal Plain, indicating atypically high heat that could lead to an increased risk of heat illnesses, especially for vulnerable populations.

Looking ahead to next weekend, a strong ridge is expected to build across the Deep South toward the East Coast, which results in high probabilities of above normal temperatures in the CPC 6-10 Outlook. Models tend to vary on whether the ridge will be center near the MS River Valley region to further east and closer to the southern Appalachians, which will strongly influence whether we end up on the warm or slightly cooler side of a frontal zone in the vicinity of the East Coast.

AVIATION /06Z MONDAY THROUGH FRIDAY/

As of 150 AM Monday...

Return/sly flow and associated moisture transport will favor the development of patches of IFR to MVFR-based stratus, some of which has already developed across the lower Savannah Basin early this morning, across the NC Sandhills and Coastal Plain around and/or shortly after 12Z. Scattered to locally numerous showers/storms are expected from the srn Appalachians to the srn Middle Atlantic Piedmont this afternoon-evening, including likely into the INT/GSO vicinity by around 21-22Z. A few may reach RDU around sunset, before generally weakening with time and ewd extent through the evening. Otherwise, light sly to swly surface winds this morning will strengthen and gust to around 20 kts with daytime heating today.

Outlook: A chance of convection will linger through Mon night and may increase with the possible passage of a convectively-amplified mid-level disturbance early Tue, especially from RDU to RWI. Dry and VFR conditions will follow behind a passing cold front later Tue and continue until return flow moisture yields a chance of morning stratus again Thu and Fri.

CLIMATE

Record High Temperatures:

June 22: KRDU: 100/2022 KFAY: 101/2022

June 25: KRDU: 100/1952

June 26: KFAY: 101/1951

June 27: KFAY: 102/1998

Record High Minimum Temperatures:

June 23: KGSO: 74/2024 KRDU: 78/2024 KFAY: 77/2024

June 25: KFAY: 75/1952

June 26: KGSO: 74/2010 KRDU: 77/2024 KFAY: 76/1997

June 27: KRDU: 76/1952 KFAY: 77/1998

RAH WATCHES/WARNINGS/ADVISORIES

None.