textproduct: Raleigh

WHAT HAS CHANGED

* No significant changes from earlier forecasts.

KEY MESSAGES

As of 135 PM Tuesday...

1) Temperatures will trend to well above normal this week, hottest Thu and Fri.

2) Generally dry weather through Thu night will yield to increased convection chances Fri through Sun, highest on Sat.

DISCUSSION

As of 135 PM Tuesday...

KEY MESSAGE 1... Temperatures will trend to well above normal this week, hottest Thu and Fri.

Surface high centered near the Mid Atlantic coast will continue an eastward drift over the next few days, while continuing to extend SW across central NC. As deep 850-500 mb W-to-E ridging spans just to our S through Wed, cutting off the Gulf/Atlantic, the resulting abundant sunshine will allow temps to heat up, and despite near- normal thicknesses Wed, the insolation will boost highs to near normal values. Low level thicknesses will climb further and peak Thu/Fri, with readings 15-20 m above normal, supporting highs around 2 categories above normal, mainly in the upper 80s to mid 90s. Heat index values will top out in the 90s Thu and 90s to around 102 Fri, as surface dewpoints creep upward ahead of the approaching cold front. This front will bring accompanying clouds and increasing rain chances Fri into the weekend which should curb the heat a bit, although the glancing blow of the weakening shortwave trough passing by to our N will be quickly followed by another ridge building over the Carolinas and Southeast states early next week, which will likely mean a return to hot temperatures by Mon/Tue.

KEY MESSAGE 2... Generally dry weather through Thu night will yield to increased convection chances Fri through Sun, highest on Sat.

Surface high pressure will continue to extend SW across central NC as it drifts further off the Mid Atlantic coast through Wed night. This will keep us within deeply dry and stable air, with low PWs and no pops. The 925-850 mb ridging stretching from OK/TX east to off the Southeast coast will limit significant Gulf/Atlantic moisture influx and keep most of the area free of rain chances through Thu, although a brief surge of 1.5"+ PW into SE NC Thu may provide sufficient moisture for a few late-day sea-breeze storms. The mid level ridge then breaks down by Thu as a broad and positively-tilted northern stream trough sweeps through the Upper Midwest and Great Lakes, with its accompanying surface cold front approaching our area from the NW late Thu. This will resulting in increasing moisture flux areawide and a rebound to near or above normal PW by Fri. With the increasing mid level flow helping to boost deep layer bulk shear and rising low level moisture fostering increased daytime CAPE, the confidence in the chance for afternoon and evening showers and storms for Fri and Sat is also increasing. With the dip in the westerlies reaching down closer to our latitude and resulting in passing of multiple weak perturbations over NC, these higher convection chances may linger into Sun, particularly over our S and E, as the surface front slow then stalls over our region. Models project that this troughing will weaken considerably and dissipate by Sun night/Mon as strong mid level ridging builds once again from the Mid South into the Carolinas, so rain chances should drop back to generally isolated by Mon/Tue.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

As of 755 PM Tuesday...

24-hour TAF period: There is high confidence in VFR conditions across much of central NC through the next 24 hours, with just a few flat cu and scattered mid/high clouds around. The one exception is some radiational fog that can't be ruled out in the east late tonight and early Wednesday morning. The best chance is at RWI, while confidence in it occurring is too low to include mention at the other TAF sites. Winds will be around 7 kts or less through the period, and many places will go calm tonight as high pressure extends west from the Atlantic.

Looking beyond 00z Thu: VFR conditions should prevail across central NC through at least Thu, with generally dry weather, although an isolated storm is possible in our far SE late Thu. Then, late Thu night into Fri morning, there is a risk for fog and low clouds producing sub-VFR conditions, mainly in our SE (FAY). The chance for showers and storms and resulting flight restrictions increases late Fri and reaches a peak Sat into Sun, as a cold front moves in from the NW and stalls across the Carolinas.

CLIMATE

Forecast temperatures are within a few degrees of these daily records:

Record High Temperatures: September 13: KRDU: 94/1936

Record High Minimum Temperatures: September 11: KGSO: 72/2007 KRDU: 75/1915 KFAY: 76/1925 September 12: KGSO: 72/2019 September 13: KGSO: 72/2019 KRDU: 74/2018 September 14: KRDU: 73/2018 KFAY: 75/2005

RAH WATCHES/WARNINGS/ADVISORIES

None.