textproduct: Newport/Morehead City

WHAT HAS CHANGED

Increased the chance of showers and isolated thunderstorms early this morning north of HWY 70.

KEY MESSAGES

1) Low-end thunderstorm risk through this afternoon.

2) Risk of dangerous heat later this week

3) Pattern expected to become more conducive for thunderstorm development by the weekend

DISCUSSION

KEY MESSAGE 1...As of 3am, a cold front was approaching the HWY 64 corridor. Weak instability and decent moisture along this front has been supporting widely scattered showers and isolated thunderstorms from SE Virginia into NE NC. Guidance suggests that what instability is left will wane by sunrise this morning, and this should lead to a reduced chance of showers by then. After a lull in shower activity this morning, there should be a renewed risk of scattered showers and thunderstorms this afternoon south of HWY 70 as the front reaches the southern counties of ENC. While the overall spirit of the forecast hasn't changed in that area today, it is worth noting that guidance has trended higher with instability along the front this afternoon (ie. MLCAPE potentially reaching 2000j/kg). Deep layer shear is still forecast to be weak, but the increased instability plus steep low-level lapse rates and DCAPE greater than 1000j/kg may support a risk of 40-50 mph wind gusts with the strongest/tallest updrafts. The overall severe thunderstorm risk continues to look low, though.

KEY MESSAGE 2...Guidance continue to trend warmer with low- level thicknesses later this week, with the warmest temperatures expected Thursday and Friday. While temperatures may not reach record- breaking levels, forecast aids and ensemble guidance suggest multiple days of well above normal temperatures. This combined with increasing humidity is forecast to support widespread "feels like" temperatures of 100-105 degrees. Additionally, the NWS' experimental Heat Risk guidance shows a moderate to major heat risk for much of ENC from Friday into the weekend. The one caveat (discussed in more detail in KEY MESSAGE 3) is the potential for thunderstorms late in the week as this could provide relief from the heat for some areas each day.

KEY MESSAGE 3...Increasing moisture and instability beneath weakening ridging aloft is expected to support a pattern that is more conducive to a daily risk of convection. Initially this may be mostly seen as a more active seabreeze. However, by the weekend there may be some added large-scale forcing from various upper level impulses forecast to move through, or glance, the region. While the strongest shear looks to be removed from the area, moderate to strong instability may support a daily risk of marginally severe, pulse convection (fairly typical for this time of year).

AVIATION /07Z MONDAY THROUGH FRIDAY/

Increasing moisture plus modest instability along an approaching cold front should continue to support isolated to SCT SHRA and TSRA across parts of ENC early this morning. For the TAF sites, this is mainly expected to be a risk for KISO and KPGV. During the afternoon hours, a renewed SHRA and TSRA risk is expected across southern sections of ENC (mainly impacting areas in the vicinity of KOAJ). Confidence in this occurring has increased enough to warrant a PROB30 mention for TSRA at KOAJ. Where TSRA occur, the environment appears supportive of 30-40kt downburst winds. There will be a risk of sub-VFR VIS as well.

For all TAF sites, the cold front will lead to a northeasterly wind shift as it moves through. This will first occur at KISO and KPGV between 12z-15z, then between 13z-16z at KEWN and KOAJ. The northeasterly winds may be gusty at times through sunset. A brief period of SCT low clouds may follow behind the front. However, the risk of widespread sub-VFR CIGs appears low.

Outlook: High pressure builds in tonight into Tuesday with generally low-impact aviation conditions expected. Southerly flow returns by the middle of the week. Increasing moisture and instability within this flow should eventually lead to an increasing chance of TSRA, especially by the end of the week.

MARINE

A cold front will move south through the northern and central waters this morning, then the southern waters this afternoon. This front will be accompanied by a northeasterly wind shift, with occasional gusts of 20-25kt. Waters favored in northeast flow (Pamlico Sound, mouth of the Neuse River) appear to have the highest chance to reach 25kt. A Small Craft Advisory was considered for those waters. However, it looks a bit marginal, therefore no headlines are planned at this time. Within the northeasterly flow, seas of 4-6ft will be common, with some 6-7ft waves possible for the offshore waters with the flow against the Gulf Stream. Most waters will not see thunderstorms today. However, a thunderstorm risk is forecast to develop along the front, potentially impacting the nearshore coastal waters south of Bogue Inlet as well as the New River.

Outlook: High pressure builds in tonight through Tuesday with improving boating conditions. Then, from mid to late week, a strengthening southerly flow is forecast to develop. A daily risk of 25kt winds appears likely during this time, especially Wednesday and Thursday when the thermal gradient is expected to be the strongest.

MHX WATCHES/WARNINGS/ADVISORIES

NC...None. MARINE...Small Craft Advisory until 5 AM EDT early this morning for AMZ152-154-156.