textproduct: Raleigh

WHAT HAS CHANGED

* No significant changes, updated aviation discussion.

KEY MESSAGES

As of 102 PM Sunday...

1) Typical late-summer weather is expected, with mostly isolated late-day showers and storms for the next several days.

2) Risk for hot temperatures and dangerous heat increase later this week.

DISCUSSION

As of 102 PM Sunday...

KEY MESSAGE 1... Typical late-summer weather is expected, with mostly isolated late-day showers and storms for the next several days.

Near-normal deep-layer moisture, proximity to deep sub-tropical ridge in the western Atlantic, and minimal mesoscale forcing mechanisms, should keep coverage of showers/storms to isolated to locally scattered over the next several days. Coverage of showers/storms will be locally greatest each day focused around weak surface pressure trough over the Piedmont, the sea breeze as well as where moderate low-lvl instability develops, which varies by day.

Most showers/storms that are able to develop through the afternoon and evening will remain relatively shallow and consist of mostly showers with isolated/embedded storms with infrequent lightning. Downdrafts will be equally typical for summer-time storms and produce 20-30 mph wind gusts immediately surrounding the locations where they collapse.

Isolated and infrequent strong to locally severe storms remain possible given the moderate to strong instability in place within the hot/humid air mass over the Carolinas (MLCAPE of 2000-3500 J/kg). Clustering storms that collapse along a common cold pool will have the best chance to produce 40-60 mph wind gusts given the lack of deep-layer shear to otherwise organize storms (0-6 km shear < 20 kts).

Tues through Thurs: The southern flank of a belt of enhanced west- northwest mid-lvl flow over the Great Lakes and northern Mid- Atlantic will slowly shift south and into the Carolinas as early as Tues and persist over the region into the late week. During this time, a slight increase to the overall synoptic deep-layer shear is expected (15-30 kts, greatest towards the VA border). Additionally, any convectively induced perturbations and remnant MCV's from more vigorous convection from the OH and TN Valley's may provide locally more organized and greater coverage of convection along their track during this time.

KEY MESSAGE 2... Risk for hot temperatures and dangerous heat increase later this week.

Sub-tropical ridging over the western Atlantic will continue to elongate while retrograding westward across FL and into the northeast Gulf through Tues. Troughing pushing into the PacNW and western CONUS will help shift the persistent mid-lvl anticyclone from the Four Corners Region and build the ridge over the lower/mid MS Valley midweek before shifting into the TN Valley and Southeast late week into the weekend.

In the absence of convection, building sub-tropical ridge to our south and west as well as warming H850 temperatures to around 20C would support low-mid 90s today, and as high as upper 90s possible Tues through Fri. Heat index values in the upr 90s to near 100 over the nw Piedmont to around 105 elsewhere, are expected through at least Thu. The approach and possible passage of a frontal zone will probably yield less hot temperatures by Fri-Sat.

AVIATION /00Z MONDAY THROUGH FRIDAY/

As of 725 PM Sunday...

24 hour TAF period: Showers and thunderstorms continue this evening. While convective activity and intensity should begin to wane with loss of heating, showers and storms may persist for the next couple/few hours, mainly at KINT AND KGSO, and possibly KFAY. While there could be some sub-VFR fog/stratus late tonight/early Mon, mainly where rain occurred this aft/eve, confidence remains too low to include in this TAF issuance. While a shower or storm cannot be completely ruled on on Mon, chances are too low at any given terminal to include at this time.

Outlook: Isolated showers/thunderstorms remain possible each afternoon through mid week. Better chances for more widespread rain and associated restrictions will return Wednesday into late week. Each morning, low stratus and/or fog may bring the chance for sub- VFR restrictions.

CLIMATE

Record High Temperatures:

August 11: KGSO: 97/1925 KRDU: 101/1999 KFAY: 100/2009

August 12: KGSO: 97/1918 KRDU: 99/2002 KFAY: 102/1941

August 13: KFAY: 100/2007

August 14: KFAY: 100/1918

Record High Minimum Temperatures:

August 10: KGSO: 76/2007 KRDU: 77/1900 KFAY: 78/2007

August 11: KGSO: 75/2007 KRDU: 78/2010 KFAY: 78/2010

August 12: KGSO: 74/2016 KRDU: 77/1900 KFAY: 79/2010

August 13: KGSO: 76/2016 KRDU: 77/2016 KFAY: 79/1999

August 14: KGSO: 75/2016 KRDU: 78/1995 KFAY: 77/2016

RAH WATCHES/WARNINGS/ADVISORIES

None.