textproduct: Newport/Morehead City

WHAT HAS CHANGED

Lowered pops and the chance of thunder for tonight. Model guidance much too high on nocturnal pops, with diurnal activity waning with loss of heating, and no real 'trigger'mechanisms for remainder of the night, esp for thunder potential. Kept chc showers in the fcst, esp coastal areas and northern tier, with coastal areas seeing the showers after midnight, but limited any thunder mention to 20% or less through Fri AM.

KEY MESSAGES

1) Weak surface low to bring an increased risk of moderate to heavy rain and breezy conditions to northeastern ENC counties today.

2) Stalled front to lead to increasingly unsettled weather into this weekend.

3) Typical summertime pattern develops by next week with a daily thunderstorm risk and warming temperatures.

DISCUSSION

KEY MESSAGE 1...A well-defined, but compact, surface low is currently moving through the western Pamlico Sound vicinity. An area of moderate to heavy rain is accompanying this low, along with an increase in southerly winds along and just to the east of it. Southerly low-level steering flow will take this low north towards the Albemarle Sound vicinity by 5-8pm this evening. Along the track of the low, there will be a continued risk of moderate to heavy rain, a few lightning strikes, and breezy southerly winds. Given the trends with this low, I've increased the chance of rain along its track, and also bumped winds up. Based on obs from this morning, some areas just west of the track of the low could pick up a quick 0.25"-0.50" of rain.

KEY MESSAGE 2...A slow-moving frontal boundary is forecast to reach ENC sometime this evening or tonight. Of note, some guidance have trended even slower, suggesting the front may just barely get into ENC late tonight. Regardless, there is good model agreement regarding the front stalling over ENC through at least Saturday morning. A deep layer of moisture pooling along this front plus modest instability and increased low-level convergence should support scattered to numerous showers and thunderstorms off and on both day and night.

Deep layer shear beneath ridging aloft points towards a reduced risk of thunderstorm organization. At large, this should also lead to a reduced risk of severe thunderstorms. The one exception is during peak heating each day as steepening low- level lapse rates in a high PWAT airmass may support some water- loaded downdrafts capable of 40- 50 mph wind gusts and minor tree damage. This may especially be the case right along wherever the front sets up each day, as the area along the front will have the strongest convergence and "best" shear.

PWATs increasing to 1.75"-2.00" within a weakly-steered environment should support periods of heavy rain. The recent stretch of dry weather and ongoing drought should help to offset any hydro concerns. However, if heavy rain trains over any one area, especially urban areas, then a flooding risk could materialize.

KEY MESSAGE 3...Once this weekend's front lifts north, ENC will get back into a typical late-spring/early summer pattern characterized by moderate instability and weak to moderate deep layer shear. Convective initiation should primarily be seabreeze-driven. Given the expected shear/instability combo, there should be a daily risk of marginally severe thunderstorms, especially from Monday onwards. This potential is also supported by both machine learning and analog guidance.

Near-climo temperatures are expected during this time, with highs in the mid to upper 80s inland, and low to mid 80s along the coast. It should be noted that while the forecast will reflect an increased chance of showers and thunderstorms on Memorial Day, an all-day washout is not expected. It will be more unsettled than what we have seen the past few weeks, though.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

A slow-moving cold front will settle south into ENC, esp around the Albemarle Sound region, ewrd towards northern Pitt and Martin counties. Will not have a mention of thunder in the fcst tonight, as activity is mainly diurnally driven, but may cont to see some sct showers, esp around KPGV. Cigs may drop to IFR esp for PGV invof of the front, but remaining sites should remain in the MVFR to VFR range as will be warm sectored. CIGs should rise some during the day Friday, but guidance may be too quick to improve conditions, especially with the front expected to stall over ENC. Along and north of wherever the front stalls is where the greatest risk of IFR, or lower, conditions is expected.

Outlook (Saturday through Tuesday): A stalled frontal boundary will support a continued risk of ocnl sub-VFR conditions and on and off shra with some thunder, esp during the afternoon to early evening time frames with the sea breeze active each day with warm, moist airmass in place. Winds will be light, generally in the 5-15 kt range.

MARINE

A weak area of low pressure will move through the Albemarle Sound vicinity over the next few hours with an increased risk of thunderstorms, and gusty south winds up to 20kt. In the wake of this low, typical summerlike conditions will prevail, with breezy thermal gradient winds, and seas of 3-5ft.

A cold front is forecast to slide slowly south into ENC tonight, with north or northeast winds developing behind it. Guidance suggests the front will stall around the central waters, with the northerly winds being focused primarily across the northern rivers/sounds/coastal waters. A weaker gradient along the front should keep the risk of 25kt winds lower for those waters. Along the front there will be a continued risk of thunderstorms.

Outlook: A cold front will remain stalled across the area through Saturday morning. The front will then shift north as a warm front Saturday afternoon, leaving behind a more typical summerlike pattern.

MHX WATCHES/WARNINGS/ADVISORIES

NC...None. MARINE...None.