textproduct: Raleigh

WHAT HAS CHANGED

* Increased southwesterly winds and wind gusts on Thursday.

KEY MESSAGES

As of 245 AM Wednesday...

1) Potential for hazardous heat appears likely on Thursday for the Coastal Plain and Sandhills.

2) Conditional threat for strong to severe storms capable of producing damaging straight-line wind gusts Thursday afternoon and evening.

3) Atypical Increased Fire Danger possible on Thursday as strong gusty winds and hot temperatures may overlap with critically dry, drought-cured fuels.

4) The best chance of showers and thunderstorms appears to be late Thursday into Friday. As mentioned yesterday, do not expect drought relief until we get a pattern change.

DISCUSSION

As of 245 AM Wednesday...

KEY MESSAGE 1... Potential for hazardous heat appears likely on Thursday for the Coastal Plain and Sandhills

A significant area of low pressure (sub 990 at times) traversing the Great Lakes will advect anomalously warm 850mb temps over the Mid-Atlantic and Carolinas from the central Plains by Thurs. This will bring back the risk for hazardous heat on Thurs. A potential failure mode will be the chance for upstream convection to shift into the region from the Ohio Valley and/or any terrian induced convection in the western Piedmont. This leads to a low confidence temperature forecast across the Piedmont. Although confidence continues to increase that the Coastal Plain and Sandhills will remain dry through the daytime hours.

Thurs will feature the best chance for hazardous heat to develop when 20-22C 850mb temperatures spread across the area, and would support 2m temperatures of upper 90s to around 100, given sufficient insolation and limited convection/outflow. HeatRisk highlights widespread Major category is likely for the eastern Piedmont, Sandhills and Coastal Plain, 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 health impacts on all populations, especially those without adequate hydration and cooling.

KEY MESSAGE 2... Conditional threat for strong to severe storms capable of producing damaging straight-line wind gusts Thursday afternoon and evening.

Within the southwesterly flow at the surface, a moderately unstable air mass is expected to develop as temperatures rise into the 90s and surface dew points rise into the mid 60s to near 70 degrees. Enhanced lower tropospheric flow, moderately steep low-lvl lapse rates, and moderate instability may support isolated strong to severe winds, but lack of much dry air in the mid/upper-lvls should mitigate DCAPE and low-lvl theta-e differences.

Given the marginally favorable environment, strong to severe wind gusts will likely have to rely on the development and maintenance of any multicell storm clusters, which given 30-35 kts of cloud-layer shear, would be possible but highly conditional.

KEY MESSAGE 3... Atypical Increased Fire Danger possible on Thursday as strong gusty winds and hot temperatures may overlap with critically dry, drought-cured fuels.

A tight pressure gradient and enhanced low/mid tropospheric flow will result in breezy conditions on Thursday. Momentum- transfer from point soundings suggest 20-30 kts gusts will be common with periodic 35 kts gusts possible, especially where sufficient solar insolation can more efficiently transfer winds at the top of the mixed-layer to the surface. This combination of strong winds and hot temperatures may result in increased fire danger concerns despite marginal RH (40-30%) given the incredibly dry fine fuels across the area. Additionally, strong and erratic winds in the vicinity of thunderstorms would increase the risk for extreme fire danger.

KEY MESSAGE 4... The best chance of showers and thunderstorms appears to be late Thursday into Friday. As mentioned yesterday, do not expect drought relief until we get a pattern change.

There is still a chance of much needed rainfall Thursday night and Friday. The potential tropical system is still expected to track to our south, from GA across possibly SC. This would keep the heavier and widespread showers/storms to our south. The other potential for needed showers/storms should come with the northern branch short wave trough that will send a surface cold front into the region Friday. QPF still remains quite variable and in flux, but remains rather light (mostly under a 0.25 to 0.50). The GFS shows absolutely nothing over the drought plagued northern Piedmont of NC. The hi-res models are now coming into range, but do not offer much hope.

We need a pattern change. The pattern has been so persistent with either a dominate ridge aloft or a zonal flow. The areas east of the Appalachians have had an atypical mountain shadow hole in the rainfall due variations of a dominate westerly flow in the mid levels for quite some time. We need a break in the mid/upper levels over our region or a dominate Bermuda high with SW flow aloft to consistently bring Gulf moisture and lift to the region. This is not seen in the foreseeable future. The zeros keep stacking up.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

As of 200 AM Wednesday...

Regional radar imagery and surface observations show an area of mostly light showers across central SC resulting in sub-VFR cigs (mainly 22-12 kft, but cigs as low as 400 ft are observed in its wake into central GA). Time-of-arrival tool suggest light rain reducing vsby to 8-4 SM and MVFR cigs will arrive as early as 07z. VCSH will likely remain in its wake around FAY with breaks resulting in IFR cigs at times through 13/14z. Remaining terminals will likely remain VFR. Light to briefly gusty southwest winds and fair-weather cu around 4-7 kft should be expected through the afternoon hours.

Outlook: Marginal low-level wind shear and MVFR stratus will be possible Thu morning, followed by strong and gusty swly surface winds and scattered convection with daytime heating Thu afternoon- evening. MVFR ceilings may redevelop Fri morning and be accompanied a continued chance of convection ahead of a passing cold front through the day Fri.

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

None.