textproduct: Raleigh

WHAT HAS CHANGED

* Increased chances for precipitation Saturday and Sunday.

KEY MESSAGES

As of 125 PM Wednesday...

1) Scattered storms area-wide this afternoon, with dangerously high heat indices across the Sandhills and Coastal Plain; both hazards are of less concern on Thursday.

2) Chances for diurnally driven convection each day through the weekend, before drying out early-mid next week. Continued warm Fri and Sat, with near to below normal temperatures Sun and Mon.

DISCUSSION

As of 125 PM Wednesday...

KEY MESSAGE 1... Scattered storms area-wide this afternoon, with dangerously high heat indices across the Sandhills and Coastal Plain; both hazards are of less concern on Thursday.

A stationary front has moved very little over the last six hours and is noticeable on visible satellite, extending from northwest to southeast in the vicinity of VUJ, SOP, and FAY. It is just north of this boundary that the Storm Prediction Center has outlined in a marginal (level 1 of 5) risk for severe weather, with the threat coming from damaging wind gusts. While the wind shear is negligible, the continued hot and humid conditions have allowed for MLCAPE values between 2000 and 3000 J/kg and DCAPE values as high as 1000 J/kg across the southwest. Peak thunderstorm coverage is likely from 5-8pm this evening. In addition, a heat advisory remains in effect south of the Triangle for heat index values between 105 and 110 degrees this afternoon.

The coverage of thunderstorms should be less on Thursday, with the bulk of the thunderstorms expected to remain north and west of the forecast area. In addition, while high temperatures will be nearly the same between today and tomorrow, slightly drier air moving into the region Thursday should result in lower humidity and drop heat index values below advisory criteria.

KEY MESSAGE 2... Chances for diurnally driven convection each day through the weekend, before drying out early-mid next week. Continued warm Fri and Sat, with near to below normal temperatures Sun and Mon.

Aloft, a broad upper trough will sit over the region as a s/w progresses esewd across the Plains and into the MS Valley Fri/Fri night. The s/w will help amplify the trough as it continues esewd across the OH Valley and mid-Atlantic over the weekend. Meanwhile, a mid-upper level anticyclone will strengthen over the Desert Southwest Fri/Sat, then lift nwd across the Rockies and ewd over the nrn/cntl Plains Sat night through Sun night. The trough will get pushed south and east next week as the high builds across the nrn/n- cntl CONUS. At the surface, a trough will remain in place over the area through Sat. A backdoor cold front should push swd-sswwd across the area Sun/Mon, while an area of low pressure develops off the Southeast US coast. The ridge may remain over the area as the low lifts newd along and off the East Coast Tue/Wed, but details are less clear that far out. Expect the greatest chances and coverage of convective activity Sat and Sun. As for temperatures, the warmest day should be Fri, with highs ranging from low 90s NW to upper 90s SE. Sun and Mon should be the (relatively) coolest days, with highs ranging from low-mid 80s N and NW to upper 80s/around 90 degrees S and SE.

AVIATION /17Z WEDNESDAY THROUGH MONDAY/

As of 125 PM Wednesday...

TAF period: While the 18Z TAFs do not call for any flight restrictions, there is definitely potential for these conditions to occur. One source of cig/vis restrictions would come from scattered thunderstorms which are currently in PROB30 groups at all terminals this afternoon/evening. Anywhere that a thunderstorm occurs, there could be brief flight restrictions. A second source of cig/vis restrictions are model soundings showing shallow low stratus between midnight and sunrise. Models are not in universal agreement that this would happen, and the sounding appears unlikely to occur if a given location doesn't receive any rainfall, but should thunderstorms develop over terminals, this will greatly increase the probability that later flight restrictions will develop due to additional low-level moisture. The wind will generally be light and variable with surface high pressure just off the Delmarva Peninsula.

Outlook: Diurnally-driven thunderstorms should decrease in coverage on Thursday and Friday, primarily just influencing INT/GSO. A cold front passing from north to south over North Carolina this weekend will bring widespread showers and thunderstorms Saturday and Sunday, with more scattered coverage occurring on Monday.

RAH WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 8 PM EDT this evening for NCZ042-077-078-085-086- 088-089.