textproduct: Raleigh

WHAT HAS CHANGED

* No major changes.

KEY MESSAGES

As of 255 PM Friday...

1) Dangerously hot weather continues today. After slightly lower highs Sat, another very hot day is likely Sun.

2) Strong to severe thunderstorms possible late this afternoon through this evening, highest risk across the northern half.

3) Shower and thunderstorm chances highest Sunday aft/eve, possible each day. Relatively cooler Monday through Wednesday, with temperatures increasing again late-week.

DISCUSSION

As of 255 PM Friday...

KEY MESSAGE 1... Dangerously hot weather continues today. After slightly lower highs Sat, another very hot day is likely Sun.

As of noon, all automated stations across central North Carolina had already risen over 90 degrees, and many locations will reach 100 degrees today. With greater humidity values over the last few days, this will bring widespread heat index values between 100 and 110 degrees. The experimental Heat Risk reaches Major (level 3 of 4) everywhere today, with areas from the Triangle to Fayetteville area reaching Extreme (level 4 of 4), indicating that not only is this heat particularly unusual, it is correlated with high levels of heat illnesses as noted by historical CDC heat-health data, and this heat could produce significant health impacts on all populations, especially those without adequate hydration and cooling. A Heat Advisory remains in effect today for all of central NC. Behind the front that moves through tonight, Saturday's highs will be lower, but still in the 90s across the area. With southerly flow developing again on Sunday, high temperatures will approach 100 degrees again in many locations. Another heat advisory may be needed for Sun, especially given the preceding multiple hot days, warm nights, and only modest "cooling" on Saturday leading to amplified heat stress.

KEY MESSAGE 2... Strong to severe thunderstorms possible late this afternoon through this evening, highest risk across the northern half.

Nearly the entire forecast area remains in a slight risk (level 2 of 5) for this afternoon, with the primary threat coming from damaging winds. A cold front is moving in from the northwest, and it will produce scattered showers and thunderstorms. While some isolated thunderstorms will be possible along a sea breeze by mid afternoon, the highest chance for showers/storms will probably come between 6- 10pm as the front approaches. Shear values will be somewhat lacking to organize any convection that occurs, but the extremely hot temperatures will allow for MUCAPE values between 2000 and 3000 J/kg, so there will be plenty of instability for storms to work with. DCAPE will also be above 1000 J/kg, enhancing the potential for damaging winds. The threat for showers/storms should greatly decrease after midnight. Despite the ongoing drought, cannot rule out the potential for localized flooding if rain rates are heavy enough at any given location.

KEY MESSAGE 3... Shower and thunderstorm chances highest Sunday aft/eve, possible each day. Relatively cooler Monday through Wednesday, with temperatures increasing again late-week.

Aloft, a nrn stream s/w moving ewd across the cntl Plains and mid-MS Valley Sat night will catch up with a srn stream wave over the TN Valley on Sun, then continue ewd across the mid-Atlantic/Carolinas Sun aft/eve. At the surface, a trough will strengthen over the area Sat night/Sun as a cold front progresses sewd across the OH Valley and into the Appalachians. Swly flow will advect warm moist air into the area ahead of the front through Sun eve. While there is still some uncertainty for Sunday wrt storm chances and strength, the 12Z NAM forecast soundings have 1000+ J/Kg SBCAPE with about 20 kts bulk shear coincident with a NAM Nest simulated line of showers and storms moving esewd into and across the area late Sun aft through Sun eve. The GFS instability is a bit lower, about 500 J/Kg, with similar bulk shear values and simulated reflectivity indicating some convection moving across the area. From SPC, there is currently a Day 3 Marginal Risk for severe storms across northeastern portions of the area Sun aft/eve. More of the hi-res guidance should become available in the next 24 hrs or so, hopefully increasing forecast confidence one way or the other.

Monday onward: The cold front will move into the area Sun night, potentially stalling across the region on Monday, with the potential for a low to develop along it, roughly invof the SC/NC coast. The low should shift offshore on Tue, allowing the front to lift back northward across the area by Wed/Wed night. Swly flow and warm advection will increase over the area until the next cold front slides swd into the area late/end of the week. Diurnal, pulse-type convection is possible each day, lowest probs on Wed with perhaps the wettest period late Thu into Fri, though its a bit far out to be very confident.

AVIATION /00Z SATURDAY THROUGH THURSDAY/

As of 855 PM Friday...

Through 00Z Sunday: Isold showers/tstms ahead of the cold front will remain possible through about 04Z this evening before finally diminishing in coverage. Outside of localized flt restrictions due to shower/tstms, VFR flt conditions expected through the TAF period. Sfc winds will become light from the NW early overnight then becoming north in the wake of frontal passage closer to daybreak Saturday morning. The front is expected to stall near the SC border during the daytime Saturday and while INT/GSO should remain dry Saturday afternoon, scattered showers/storms will be possible at RDU/RWI and likely at FAY.

Outlook: Diurnally driven showers and thunderstorms will remain possible at all terminals Sunday through Tuesday, with less coverage expected by Wednesday.

CLIMATE

Record High Temperatures:

June 12: KGSO: 104/1914 KRDU: 98/2002 KFAY: 99/1926

June 13: KRDU: 100/2002 KFAY: 99/2022

June 14: KGSO: 98/1926 KRDU: 97/1944 KFAY: 100/2022

June 18: KRDU: 98/2015

Record High Minimum Temperatures:

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

June 13: KGSO: 73/2015 KRDU: 75/2025 KFAY: 77/1998

June 14: KGSO: 71/2025 KRDU: 79/2022 KFAY: 77/2022

June 15: KGSO: 74/2022 KRDU: 78/2025 KFAY: 76/1926

June 16: KFAY: 77/2015

June 18: KGSO: 73/2018 KFAY: 76/2017

RAH WATCHES/WARNINGS/ADVISORIES

Heat Advisory from 11 AM to 8 PM EDT Friday for NCZ007>011-021>028- 038>043-073>078-083>086-088-089.