textproduct: Raleigh

WHAT HAS CHANGED

* Locations where strong to severe thunderstorms will be possible this afternoon and evening has been expanded to cover areas along and west of the I-95 corridor, including the Triangle, Fayetteville, and the Triad.

KEY MESSAGES

As of 215 AM Friday...

1) Scattered to locally numerous showers and storms will be possible this afternoon/evening and be capable of strong to severe straight- line wind gusts and locally heavy rainfall amounts of > 1".

2) Monday into Tuesday will likely feature scattered to numerous showers and thunderstorms. Beneficial rain possible for some areas. Hot Monday, cooling by Tuesday especially north.

3) A NE flow and cold air damming will yield much cooler and cloudier conditions, possibly accompanied by periods of light rain and drizzle, by the middle of next week.

DISCUSSION

As of 215 AM Friday...

KEY MESSAGE 1... Scattered to locally numerous showers and storms will be possible this afternoon/evening and be capable of strong to severe straight-line wind gusts and locally heavy rainfall amounts of > 1".

A pair of fronts are expected the shift across our area over the next 24 to 36 hours. The lead boundary will be a pre-frontal trough, currently stretching roughly from Richmond to Charlotte in the 05z obs, which will mix southeast throughout the morning and bring atypical hot and humid conditions within northerly flow across the forecast area. Trailing this boundary will be the synoptic cold front, which will likely be working through the Virginias and southern Ohio Valley through the daylight hours.

In between these two boundaries, surface dew points should remain in the mid/upper 60s to low 70s throughout peak heating as temperatures rise well into the 90s. This should provide a moderately unstable air mass with instability ranging from 1000-2000 J/kg. Although isolated pulse air mass showers/storms can't be ruled out anywhere through the afternoon (with convective temps in the low 90s), the greatest convective coverage will likely be along a the track of upstream showers and storms currently working through Ohio as of 06z. Mean-wind steering flow should continue to track this cluster towards the central Appalachians by early afternoon and then track generally south and into central NC during peak heating. Poor mid-lvl lapse rates and related marginal instability should preclude a more widespread severe threat, however, steep low-lvl lapse rates in excess of 9 C/km over the Piedmont could favor storms organizing along a common cold-pool and result in localized strong to severe straight-line wind gusts, despite weak tropospheric wind shear (5-10 kts).

The synoptic cold front should start to working into the area from the north around or shortly after midnight and may support a continuation of shallow showers through the overnight period.

KEY MESSAGE 2... Monday into Tuesday will likely feature scattered to numerous showers and thunderstorms. Beneficial rain possible, remaining hot Monday. Turning cooler later Tuesday, especially over north-central areas.

Models continue to suggest a potentially moist period for our region Monday into Tuesday. This is due to the mid/upper trough approaching from the Midwest and Ohio Valley. One cold front is expected to reach NC Monday afternoon and possibly stall, with another cold front expected to backdoor the region late Tuesday into Tuesday night. There should be a couple of rounds of showers/storms, especially during the afternoon and evening Monday into Tuesday night. Some beneficial rainfall is expected, but as is typical with thunderstorms some areas will get the beneficial rainfall of 1 to locally 2 inches, while some others may be left out. Much more on this forecast through the weekend updates. It will likely continue very warm and humid Monday, with some cooler conditions Tuesday across the north (due to clouds/showers/storms). Monday highs should be in the mid 80s to lower 90s south. Highs Tuesday will be around 80 north to near 90 south. Lows in the mid 60s to around 70.

KEY MESSAGE 3... A NE flow and cold air damming will yield much cooler and cloudier conditions, possibly accompanied by periods of light rain and drizzle, Tuesday night into Thursday.

Once the cold front settles south of the region later Tuesday and Tuesday night, a low level NE flow will continue to feed low level moisture into the region. This would bring stable conditions and would mean that stratus, fog, and periods of light rain/drizzle or light showers will be likely Tuesday night into Wednesday and Thursday. The combination of the NE flow, moisture, cloudiness, and some light rain will keep daily highs in the 70s (or much below normal for the first time in weeks). Lows in the 60s, with some 50s possible north-central Wed-Fri.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

As of 130 PM Friday...

24 hour TAF period: Scattered showers and thunderstorms are beginning to develop across central North Carolina, with the greatest coverage around INT/GSO. The coverage is expected to expand over the next few hours, and TEMPO groups for thunderstorms with gusty wind were maintained at 4 of 5 TAF sites - confidence is not high enough to go with a TEMPO group as far east as RWI. INT just had a wind gust to 31 kt with IFR visibility, and this will be possible at each of the terminals this afternoon into the evening. After convection comes to an end tonight, IFR/LIFR ceilings are expected to develop late tonight into Saturday morning, although again, there is slightly less confidence as far east as RWI with the amount of cloud cover and whether ceilings will form. While there could be some minimal visibility restrictions, low ceilings will drive the flight category. Conditions may be slow to scatter out Saturday morning.

Outlook: There will be a chance of afternoon showers and thunderstorms at all terminals, with the highest chance at FAY. MVFR ceilings appear likely to develop Saturday night into Sunday morning. After mostly dry conditions Saturday night through Sunday night, expect widespread precipitation Monday through Tuesday, eventually becoming more scattered. Restrictions will be possible through this period as well.

RAH WATCHES/WARNINGS/ADVISORIES

None.