textproduct: Raleigh

WHAT HAS CHANGED

* No major changes.

KEY MESSAGES

As of 215 PM Monday...

1) Hot and mainly dry through Wednesday.

2) Rain chances return mid-week, highest on Thursday, and linger through the weekend. Low confidence in high temps Thursday and especially Friday.

DISCUSSION

As of 215 PM Monday...

KEY MESSAGE 1... Hot and mainly dry through Wednesday.

An unseasonably strong mid/low-level anticyclone (700mb heights well exceeding the daily max at GSO, MHX, CHS, and RNK), and strong cap at the base of steep mid-level lapse rates (associated with a modified EML and persistent subsidence) sampled in the 12z RAOB data over Carolinas and portion of the Southeast, will keep conditions capped and void of precipitation amidst seasonably moist deep-layer moisture in place. Warm temperatures though the mid/low-lvls will exceed the 99th percentile through at least Wednesday and support several days of hot conditions at the surface when temperatures should regularly eclipse 90 degrees by mid-afternoon.

Given central NC's position within the described weather pattern above, there are minimal failure modes and reasonably high confidence in the forecast high temperatures through Wed. Minimal mixing out of dew points have been observed over the past couple days over the Carolinas, and adjusted heat indices will remain below triple-digits, but still reach into the mid-90s in most locations.

This kind of early-season heat can still be unexpectedly dangerous, as people have not yet become acclimated to the hot weather. The daily experimental Heat Risk is expected to peak at Moderate (level 2 of 4) today through Wed, but may reach Major (level 3 out of 4) in urban areas around the RTP. This kind of heat is quite unusual for this time of year and has historically led to high levels of heat illness, with sensitive individuals and those without adequate cooling particularly vulnerable. And with just a modest breeze and lots of sunshine each day, the WBGT index will also be elevated, so spending time in the shade is encouraged, especially for those working or exercising outdoors.

KEY MESSAGE 2... Rain chances return mid-week, highest on Thursday, and linger through the weekend. Low confidence in high temps Thursday and especially Friday.

The mid-level ridge will weaken and shift out of the region Wed/Wed night as a s/w tracks ewd across the Northeast US/mid-Atlantic. The sub-tropical ridge may once again strengthen and lift newd across the region Thu night through Sat, with several s/w disturbances tracking across the Plains and MS Valley. At the surface, a pre- frontal trough will develop over the area on Wed, with Bermuda high pressure to the east and a cold front approaching from the north, remaining in place until the cold front slides southward across central NC on Thu. A brief CAD may set up Thu night into Fri as high pressure tracking across the Northeast US ridges swd into the area. Expect the front to lift nwd back across the area Fri night/Sat, however the spread in available guidance increases beyond Fri and details remain uncertain thereafter.

Precipitation: The northern and northwest Piedmont could see showers/isolated storms as early as Wed evening, however the better chances will come Thu along and ahead of the backdoor cold front as it moves into and across the area. In the wake of the front, warm air advecting in above the cooler, stable boundary layer could result in some light rain Thu night into Fri over central NC. Assuming the wedge erodes Fri night into Sat and a warm front lifts nwd across the area, there will be the chance for additional diurnally driven convection over the weekend, especially along differential heating boundaries.

Temperatures: Highs Thu will be impacted by the timing of the front and the convection ahead/along it. For now, expect highs ranging from around 80 degrees north to low 90s south. There is a large bust potential wrt highs on Fri given the potential for CAD to briefly set up and possible continued rain into it. For now have highs ranging from around 70 degrees NW to low/mid 80s south, but with below average confidence. Lows Thu and Fri nights expected to range from mid 50s north to mid 60s south. Generally expect temperatures to moderate back to near/slightly above normal over the weekend.

AVIATION /18Z MONDAY THROUGH SATURDAY/

As of 100 PM Monday...

Prevailing VFR conditions are expected through the 24 hr TAF period. Scattered fair weather cu with bases around 5-7 kft will continue across the forecast area until dispersing shortly before sunset. Enhanced moisture at the surface is expected to lift north from Coastal Carolinas to produce another round of low-stratus and fog, but forecast confidence on reaching any central NC terminals is low.

Outlook: Threat for morning low-stratus and mist will again be possible Wed and Thurs morning within this persistence pattern. Showers and storms will be possible as early as Wed evening around INT/GSO, but more likely Thurs surrounding a backdoor cold frontal passage and breezy northwest winds. Brief classical-CAD will likely bring sub-VFR cigs to all terminals behind the fropa that will likely persist into Fri, especially in the typical CAD regime at INT/GSO and potentially RDU.

CLIMATE

Record High Temperatures:

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 KFAY: 75/1930 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.