textproduct: Raleigh

WHAT HAS CHANGED

* Just a very outside chance of a stray isolated shower Sunday

KEY MESSAGES

As of 115 PM Saturday...

1) Hot weather and mainly dry with low to middle 90s Sunday through Wednesday.

2) Increasingly unsettled and trending lower in highs Wed onward, but the finer details are far from certain.

DISCUSSION

As of 115 PM Saturday...

KEY MESSAGE 1... Hot weather and mainly dry with low to middle 90s Sunday through Wednesday.

Anomalous ridging extending west into the southeast US is forecast to be in place from tomorrow through at least Wednesday. Ensemble and probabilistic data from the NBM continue to show a high likelihood (70-percent and greater) of high temperatures at or above 90 degrees during this stretch. Low-level thicknesses will rise to values typical for late July, supportive of low to middle 90s. The Heat Risk category reaches a Moderate (level 2 of 4) threshold during this time with dewpoints mixing out into the 50s at times in the afternoon. As we saw in April during the two heat wave events, early season heat can result in a rapid rise in heat-related illnesses due to people being less accustomed to these conditions.

Shower and storm chances will remain limited during this time frame, mainly focused along subtle, mesoscale boundaries of the sea-breeze and a lee trough west of the Piedmont.

For our Sunday, tomorrow, the mid-level lapse rates are actually fairly steep, with over 8C/km, with 1500 J/kg of CAPE, albeit with a notable capping inversion within the ridge. A decaying eastward- moving mid-level disturbance in eastern GA and upstate SC will likely force scattered storms across this region. The newer high-res REFS ensemble also shows a few widely isolated storms in and around central NC, perhaps in relation to a few cells breaking the cap where a tongue of higher lower 60s dewpoints set up within PW's of 1.2 to 1.4 inches. The overall chance on Sun is low, but a stray storm cannot be ruled out. The better chance of storms may come late Wed with the approach of a cold front and resultant storm outflow from storms upstream.

KEY MESSAGE 2... Increasingly unsettled and trending lower in highs Wed onward, but the finer details are far from certain.

The long-range LREF ensemble and corresponding deterministic scenarios continue to indicate that the anomalous ridge extending into the area will gradually lose its influence. The consensus supports a gradual trend of height falls in association with troughing across the west and northwest gradually shifting east into Canada. As that happens, a slowly approaching cold front is forecast to slide east from the OH/TN valley region. That front, if it were to approach as guidance suggests, should favor increased shower and storm chances to close out next week. The wettest period in the guidance is centered around Thu, when the front approaches and may eventually push through. The LREF ensemble shows many members indicating increasingly wet weather Thu into the weekend, as a result of the lingering front and disturbances aloft tracking into the area in the southwest flow. But the mesoscale details will be key in this convective regime as it relates to how much QPF we get, which still shows high spread. At the surface, ensembles do suggest the potential for late-season cold air damming late next week with clusters indicating 1024-1028mb high pressure nosing down from the Great Lakes. However, there still remain a set of other solutions which show a more progressive high off the Atlantic coast, making these details far from certain. For now, expect that uptick in storm chances late next week, along with gradually lower highs in the 70s to 80s.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

As of 100 PM Saturday...

VFR conditions are expected to prevail through the 24 hour TAF period as mid/high clouds briefly thicken through tonight. Low-lvl moisture return may result in SCT/BKN MVFR-to-LIFR cloud layer and mist, primarily around FAY but perhaps as far north as RDU/RWI. Confidence in its development is low, but higher confidence exists in the possibility of a brief MVFR cig as diurnal heating begins through 15-16z Sun morning, again, primarily at FAY. Otherwise light south-southwest winds prevail with periodic gusts lingering this afternoon until around 23-00z this evening.

Outlook: Risk for morning stratus, mist, and brief MVFR cigs through mid-morning will continue each morning, primarily across the Coastal Plain and Sandhills (FAY/RWI), through Wed morning. Rain and sub-VFR aviation restrictions become more likely Wed through Thur ahead of and especially behind a weak and slow-moving cold front where classical-CAD pattern appears probable as early as Thurs/Thurs night.

CLIMATE

Record High Temperatures:

May 17: KGSO: 94/1915 KRDU: 92/1947 KFAY: 97/1941

May 18: KGSO: 95/1911 KRDU: 95/1906 KFAY: 96/1911

May 19: KGSO: 96/1911 KRDU: 95/1962 KFAY: 96/2022

May 20: KGSO: 95/1917 KRDU: 96/2022 KFAY: 99/2022

Record High Minimum Temperatures:

May 18: KGSO: 70/2015 KRDU: 72/1896 KFAY: 71/2018

May 19: KGSO: 68/2018 KRDU: 70/2022

May 20: KGSO: 68/2022 KRDU: 69/2019 KFAY: 71/2022

May 21: KGSO: 67/2022 KRDU: 71/1898 KFAY: 71/2025

RAH WATCHES/WARNINGS/ADVISORIES

None.