textproduct: Raleigh

WHAT HAS CHANGED

* A Heat Advisory, for near criteria values of 105 F, has been issued for Sunday for the Coastal Plain, ern Sandhills, and northeast Piedmont (including the Triangle).

KEY MESSAGES

As of 300 PM Saturday...

1) Continued hot, though trending less so, with isolated/widely scattered convection over the Piedmont today and scattered to locally numerous coverage on Sunday - most intense cells capable of damaging downbursts both days

2) Unsettled weather pattern returns next week, especially Monday and Tuesday.

DISCUSSION

As of 300 PM Saturday...

KEY MESSAGE 1... Continued hot, though trending less so, with isolated/widely scattered convection over the Piedmont today and scattered to locally numerous coverage on Sunday - most intense cells capable of damaging downbursts both days

The previously, anomalously strong lwr mid-latitude anticyclone has weakened 3 decameters since it peaked in strength over the Virginias at 00Z-12Z Fri. It has also peaked in relative proximity over s-cntl VA and nern NC at 00Z-12Z Sat. As its center continues to drift offshore and away from cntl NC, mid-level flow will continue to veer through sly to swly and provide a corridor for convectively-enhanced mid-level disturbances to track from the srn Appalachians to the srn Middle Atlantic Piedmont. These disturbances will focus ascent amid otherwise more broadly and weakly falling heights (10-30 meters) behind the aforementioned, departing anticyclone. A higher-level, TUTT trough or similar over VA, evident in water vapor satellite and upr air charts, will slightly precede these mid-level features and track across and offshore the srn Middle Atlantic through 06Z Sun. While this upr-level feature is worth monitoring for influence for deep convective development over the nrn Coastal Plain for the next few hours, it instead appears likely to merely maintain a veil of cirrostratus ceilings given trends in both regional radar data and CAM solutions.

At the surface, an Appalachian-lee trough will continue to extend across wrn portions of the srn Middle Atlantic Piedmont through the weekend. It will do so ahead of a synoptic front, now stretching across the nrn Middle Atlantic wswwd across cntl OH and IN, to a 1013 mb convectively-amplified low over nrn IL, which will settle to near the Mason Dixon line by Sun evening.

Generally persistence temperatures between 99-102 F are forecast through the remainder of this afternoon. When combined with surface dewpoints that have mixed out into the middle 60s on average over the Piedmont this afternoon, reliable heat index values will peak between 100-110 F. Isolated to widely scattered storms will be possible over the nw Piedmont this afternoon, invof the lee trough, while the greater multi-cell, cold pool-driven convective coverage will likely hold both to the west and north of cntl NC. The presence of observed DCAPE of 1600 J/kg at both GSO and MHX this morning, corroborated by more recent SPC meso/objective analysis data, will provide a favorable environment for damaging downbursts.

Temperatures on Sun will not be as hot as today given falling heights and associated cooling and also an increase in cloud coverage and scattered showers and storms and outflow, with the latter focused over the srn and wrn Piedmont Sun afternoon. It will nonetheless be continued hot, with high temps in the mid 90s to around 100 F. When combined with near persistence to slightly lower afternoon dewpoints versus those of today, heat index values are expected to peak in the upr 90s to near 100 over the the srn through wrn Piedmont, ranging to near 105 F in the Coastal Plain and adjacent Sandhills and northeast Piedmont. A Heat Advisory has consequently been issued for those latter areas for noon to 8 PM Sun. Given similarly high DCAPE values Sun as those of today, and with increased convective coverage, the chance of a few damaging downbursts will be slightly greater than today both in coverage and probability of occurrence.

KEY MESSAGE 2... Unsettled weather pattern returns next week, especially Monday and Tuesday.

As the ridge weakens further and continues to shift southeastward at the beginning of the work week, multiple rounds of shortwave energy will move through the region ahead of a cold frontal passage Tuesday night or Wednesday morning. This will allow for rain chances on both Monday and Tuesday in the afternoon and evening. Maximum temperatures should be in the low to mid 90s each afternoon with dewpoints in the 70s, which should allow for enough energy for storm development. Also, high PW values may allow for some stronger storms to produce isolated strong to damaging winds and heavy downpours in water-loaded downdrafts, however widespread severe weather is not expected. Ensemble guidance is suggesting around 0.25 to 0.5 inch of rain Monday afternoon and up to 0.3 inch on Tuesday afternoon, however any stronger storms could locally enhance rainfall totals. After the cold front moves through the region Tuesday night or Wednesday morning, the region should return back to a more typical summer-like pattern with diurnally induced showers with embedded storms and highs in the upper 80s through the 90s.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

As of 200 PM Saturday...

TAF period: Primarily VFR conditions and light, generally sly winds are forecast through the 18Z TAF period. The exceptions to VFR will be an isolated to widely scattered storm (20-30 percent chance) mainly through 00Z Sun at INT/GSO and a short-lived IFR ceiling at FAY between 10-12Z Sun.

Outlook: Convective coverage should further increase to scattered (30-50 percent probability) at INT/GSO and near and especially just west of RDU and FAY Sun afternoon-evening, followed by numerous showers/storms Mon and possibly again on Tue.

CLIMATE

Records within reach this forecast period...

Record High Temperatures:

July 4: KGSO: 98/1970 KRDU: 101/2024 KFAY: 98/2019 July 5: KGSO: 98/2012 KFAY: 101/2024

Record High Minimum Temperatures:

July 4: KGSO: 73/2018 KRDU: 79/1902 KFAY: 78/1913 July 5: KGSO: 74/1999 KRDU: 78/2024 KFAY: 77/2005 July 6: KGSO: 76/1999 KRDU: 79/1900 KFAY: 77/2024

RAH WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM EDT this evening for NCZ007>011- 021>028-038>041-043. Heat Advisory from noon to 8 PM EDT Sunday for NCZ008>011-024>028- 040>043-076>078-088-089. Heat Advisory until 8 PM EDT this evening for NCZ042-073>078-083>086- 088-089.