textproduct: Raleigh

WHAT HAS CHANGED

* Indications of a more active and possibly wetter pattern late in the weekend into early next week with a deep southerly flow.

KEY MESSAGES

As of 230 PM Sunday...

1) Above-normal warmth in the 90s continues through Monday before a cold front crosses the region late tomorrow, bringing isolated northern/western storm chances tonight and much cooler relief Monday night.

2)After a break on Tuesday, temperatures will warm on Wednesday with another round of dangerous heat arriving on Thursday and Friday and possibly continuing into Saturday.

3) Increasing moisture late in the work week and especially next weekend combined with a slightly more active flow will result in a chance of mainly diurnal convection. However rainfall coverage and amounts will still be limited.

DISCUSSION

As of 230 PM Sunday...

KEY MESSAGE 1... Above-normal warmth in the 90s continues through Monday before a cold front crosses the region late tomorrow, bringing isolated northern/western storm chances tonight and much cooler relief Monday night.

Warmth continues today and one more day tomorrow. Highs today will reach the low to mid-90s, with upper 90s expected across portions of the Triangle. A frontal boundary sagging southward across the Ohio Valley and northern Mid-Atlantic will approach the region tonight. While most showers and storms will remain north of the VA/NC border, isolated cells could develop late tonight across the NW, NE Piedmont, and Northern Coastal Plain. Monday remains warm and dry ahead of the front with highs in the low 90s. The front finally moves through late Monday, bringing cooler relief Monday night as lows drop into the upper 50s to mid-60s.

KEY MESSAGE 2... After a break on Tuesday, temperatures will warm on Wednesday with another round of dangerous heat arriving on Thursday and Friday and possibly continuing into Saturday.

The modest cool front that moves south through the area on Monday stalls to our south and southwest on Tuesday. A slightly cooler day with an east to northeast wind is expected on Tuesday with lower dewpoints in the upper 50s across northeastern areas and highs in the mid to upper 80s which is near to just slightly above average.

The airmass warms on Wednesday with low level thicknesses increasing about 10 to 12m on average with highs in the upper 80s to lower 90s. Dew points nudged upward an make it feel a little more humid but they should be offset somewhat by deep mixing of 6 to 8kft.

A much more significant period of heat arrives on Thursday through Saturday and likely peaks on Friday. Morning low level thickness values climb into the 1400 to 1410m range on Thursday and increase further into the 1420s on Friday. While the core of the hot airmass is located just to the north across the Chesapeake Bay region, these thickness values should support highs in the lower to mid 90s on Thursday and Friday with a few spots in the upper 90s. The airmass will be a bit more humid and so heat impacts will be greater. Note that some of the statistical guidance, primarily the NBM appear way too hot with many locations getting highs in the 98 to 102 range.

The experimental probabilistic Heat Risk tool shows a 50-80% chance of reaching Major heat levels, mainly across the eastern Piedmont and Coastal Plain, on Thursday thru Saturday, suggesting significant impacts for all populations without adequate cooling or hydration.

The heat relaxes a bit on Saturday and Sunday and heat risk decreases a bit. With the potential for more cloud cover and an upward tick in rain chances over the weekend, high temperatures will cool a bit but it will be muggy with lows in the lower 70s.

KEY MESSAGE 3... Increasing moisture late in the work week and especially next weekend combined with a slightly more active flow will result in a chance of mainly diurnal convection. However rainfall coverage and amounts will still be limited.

The modest cool front that moves south through the area on Monday stalls on Tuesday and becomes meridional as it extends from the central Appalachians south across western NC into western SC. Better moisture and local convergence near the front will result in a few showers or storms across the western Piedmont on Tuesday, with the greatest coverage across the Mountains and Foothills, otherwise fair weather is expected.

The front washes out as it lifts northeast on Wednesday with a south to southwesterly flow developing on Wednesday and expanding on Thursday and Friday. This will result in an upward tick in surface dewpoints and precipitable water values which will climb above average. The development of a mid level weakness/shear axis and potentially a lee surface trough should aide in provide at least a meager to modest focus for convection. These subtle features will come into better focus in a few days, but there is at least a low end chance (20 to 35%, greatest across the west) of mainly afternoon and evening showers and storms for Wednesday into Friday.

There are signals in some of the ensemble guidance that a digging trough over Midwest will support a stronger southerly flow at low and mid levels across the eastern Gulf and Southeast potentially resulting in a further increase in moisture and a more active pattern. A handful, perhaps 10 to 15% of the EC an GFS ensembles even suggest some sort of northward advancing low pressure area over the Gulf late in the weekend or on Monday. Still, WPC's 7 day precipitation forecast across central NC suggest precipitation totals averaging between 0.25 and 0.5 inches, which is 50% of average or less and as is typical with summertime convection, we are likely to see patches of higher totals with many areas not seeing much if any rain at all.

Finally, I'd be wary of automated forecasts and apps that show rain chances of 50 to 70% during the Wednesday thru Saturday period as the pattern suggests these are too high. &&

AVIATION /18Z SUNDAY THROUGH THURSDAY/

As of 200 PM Sunday...

High confidence in VFR conditions prevailing across all terminals through the forecast period. West to northwest winds around 510 kts at KINT and KGSO will back to the southwest this evening, before shifting to the northeast around 10 kts late tomorrow morning. Further east at KRDU, KFAY, and KRWI, occasional afternoon gusts up to 20 kts will diminish around sunset, with winds becoming light and variable overnight. A weak boundary slipping south tomorrow morning will transition winds to the northeast at all eastern terminals early morning.

The primary concern is a low-end chance for overnight convection across the north eastern half of the CWA. A PROB30 was added at KRDU (02Z06Z) and KRWI (03Z07Z) to account for potential isolated showers and thunderstorms, which could bring brief restrictions, lower ceilings down or below 5k feet, and variable strong winds. At KINT, KGSO, and KFAY are expected to remain dry. VFR conditions are expected to persist through Monday afternoon before the sub VFR conditions with showers and storms move into the region late afternoon Monday.

Outlook: Scattered showers and storms, which may contain brief sub- VFR conditions and gusty winds, are possible late Mon afternoon through evening, with the best chance from INT/GSO southeast through FAY, but confidence in the details is low. There is a good chance for sub-VFR cigs Mon night through the first half of Tue across the W and SW including INT/GSO. Otherwise, VFR conditions are favored, and typical daytime scattered showers/storms will remain possible through Thu.

CLIMATE

Record High Temperatures:

June 7: KGSO: 98/1925 KRDU: 100/2008 KFAY: 99/2008

June 10: KFAY: 99/2008

June 11: KGSO: 98/1914 KRDU: 100/1914 KFAY: 102/1926

June 12: KRDU: 98/2002 KFAY: 99/1926

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

Record High Minimum Temperatures:

June 7: KGSO: 73/2008 KRDU: 74/2008

June 8: KGSO: 73/2008 KRDU: 75/1899 KFAY: 74/2008

June 11: KGSO: 74/2008 KRDU: 74/2008 KFAY: 77/1981

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

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

RAH WATCHES/WARNINGS/ADVISORIES

None.