textproduct: Raleigh

WHAT HAS CHANGED

* Heat Advisory issued for the Triangle, eastern Piedmont, Sandhills, and Coastal Plain from 11 AM to 8 PM today.

KEY MESSAGES

As of 222 AM Thursday...

1) Heat Advisory in effect today for the eastern Piedmont, Sandhills, and Coastal Plain.

2) A conditional threat for strong to severe storms capable of producing damaging straight-line wind gusts remains this afternoon and evening, with greatest chances for showers/storms late tonight into Friday.

3) Increased Fire Danger today as strong gusty winds and hot temperatures overlap with critically dry, drought-cured fuels.

DISCUSSION

As of 222 AM Thursday...

KEY MESSAGE 1... Heat Advisory in effect today for the eastern Piedmont, Sandhills, and Coastal Plain.

A hot, moist, and windy day will be in place today as broad southwest flow and very warm temperatures in the low-levels favor record heat. In fact, the low-level thicknesses approach near maximum values for this afternoon and early evening. These values rise some 16-20m from Wed, supportive of a 4-6 rise in highs compared to Wed. That should put highs across central NC largely in the mid 90s across the west, to upper 90s to near 100 elsewhere. RDU will likely break its record high. Given the strong southwest flow of 25-35 mph wind gusts, we will see some drier air mix down, allowing to dewpoints to perhaps mix out into the mid to upper 60s. However, we will additionally see moisture steadily increase ahead of the tropical remnants. Even with the lowered afternoon dewpoints, heat indices for areas along/east of US-1 range from 104 to 108, with the HeatRisk category in a 3 out of 4. This kind of heat will affect anyone without cooling/hydration.

KEY MESSAGE 2... A conditional threat for strong to severe storms capable of producing damaging straight-line wind gusts remains this afternoon and evening, with greatest chances for showers/storms late tonight into Friday.

The pattern today through tomorrow features a few systems worth noting. First, a cold front across the Midwest into the OH valley will gradually slide south but remain north of the region through most of Fri. A pre-frontal trough will exist this afternoon, stretching just east of the Appalachians of VA/NC. Third, we continue to watch the tropical remnants, which will bring overall deepening moisture today through Fri.

SPC has maintained a marginal risk of severe storms today and tonight, with the main threat remaining damaging straight-line wind gusts. The overall ingredients include high DCAPE upwards of 1000 J/kg, driven in part by the inverted-V soundings and dry air at lower levels from deep mixing. Additionally, MLCAPE approaches some 1500 J/kg, along with mid-level flow around 30 kts, supportive of this threat.

The caveat is that overall storm coverage at least during the day may be limited. The 00z HREF members are not in agreement on overall coverage. Some members show more isolated activity, focused along subtle boundaries or the pre-frontal trough. Other HREF members, namely the NSSL show convection blossoming over SC and reaching central NC in the late afternoon to early evening, perhaps enhanced along a sea-breeze. Needless to say, there is quite a bit of spread. Nevertheless, that severe risk is warranted if storms can get going.

A better chance of showers and embedded storms looks favored late Thu night and overnight into perhaps late morning to midday Fri. This is when the tropical remnants from Arthur advect up into the region. The 00z models appear to be in better agreement with the track of this low, with the global models placing its position in north-central SC by early Fri morning. However, a few CAM solutions (NSSL/NAM-NEST) are further north, tracking the low near Charlotte and right into the Triangle during the morning hours Fri. Regardless of solution, moisture associated with the system should favor widespread showers. We are slightly concerned that there could be an isolated tornado threat in southern areas early Fri morning as the low passes through. During this time, low-level and deep-layer shear increase, though instability is somewhat uncertain. Given dewpoints near the low 70s, this threat possible but with low confidence at the moment. The best chance for this would be in the Sandhills to southern Coastal Plain.

KEY MESSAGE 3... Increased Fire Danger today as strong gusty winds and hot temperatures overlap with critically dry, drought-cured fuels.

The stout SW winds out ahead of the approaching surface front (from the NNW) and approaching dissipating tropical system (from the WSW) are expected to peak at sustained values of 15-20 mph, with frequent gusts as high as 25-35 mph expected as deep mixing taps into strong winds just aloft. While RH values are expected to be mostly 35-40% and thus above typical critical thresholds, the ongoing severe-to- exceptional drought and exceptionally dry fuels combined with these gusty winds will lead to an increased risk of fire ignition and adverse fire behavior over much of NC today, from just inland to just east of the Foothills. This risk will be amplified by erratic and shifting winds and gusts in and near storms. After coordination with the NC Forest Service and their field operations staff, a fire danger statement remains in effect to address the increased fire danger.

AVIATION /06Z THURSDAY THROUGH MONDAY/

As of 222 AM Thursday...

VFR conditions are favored to start the TAF period. As low-level moisture increases from the southwest, we are still thinking an area of brief MVFR ceilings are expected to reach GSO, INT, RDU, and FAY. However, given recent guidance, we did reduce the eastward extent of these sub-VFR conditions, keeping RWI VFR. We opted for TEMPO groups at RDU and FAY given uncertainty as to how prolonged it may be compared to higher chances over the far western Piedmont. Regardless, these conditions should lift to VFR at all terminals ~14z, with gusty SW winds commencing in the 25-30 kt range. These gusts should weaken by sunset.

Convective chances are somewhat uncertain, but a few focus areas are possible. The first is along a pre-frontal trough near GSO/INT. A second chance may be with overall increasing moisture ahead of the remnant tropical system. CAM solutions are not in the best of agreement so kept the PROB30 TSRA groups, mainly in the 18-24z period, slightly earlier in the west and a tad later in the east. A better batch of showers and embedded storms are expected after the period between 06-12z Fri.

Looking beyond 06Z Fri: A better chance of rain and isolated storms will arrive into early Fri as the tropical remnants advect into the region, coincident with sub-VFR conditions. VFR conditions should then dominate from late Fri through at least Sun, with another chance of sub-VFR stratus Sun night into early Mon.

CLIMATE

Record High Temperatures:

June 18: KGSO: 100/1944 KRDU: 98/2015 KFAY: 102/1944

Record High Minimum Temperatures:

June 18: KGSO: 73/2018 KRDU: 77/2025 KFAY: 76/2017

June 19: KGSO: 77/1970 KRDU: 73/2025 KFAY: 77/2017

RAH WATCHES/WARNINGS/ADVISORIES

Heat Advisory from 11 AM this morning to 8 PM EDT this evening for NCZ008>011-024>028-040>043-075>078-085-086-088-089.