textproduct: Newport/Morehead City

WHAT HAS CHANGED

Corrected for incorrect excessive rainfall risk.

KEY MESSAGES

1) Seasonable fall weather lingers through today.

2) Warming trend begins late this week and into the weekend, along with next chance for rain, potentially heavy.

DISCUSSION

KEY MESSAGE 1...Little change in the weather pattern forecast today as high pressure and dry airmass remains in place and temperatures only slightly below normal for early October. Radiational cooling occurring this hour with some of the more reliably cool spots already into the upper 40s. Low-level thicknesses slowly build today and highs will be a few degrees warmer than yesterday but still below 80. A modest uptick in TDs suggests lows overnight in the low to mid 50s, but well sheltered spots could make a run again into the upper 40s.

Overall airmass will be too dry for widespread fog, but some very shallow and transient patches are possible this morning and next.

KEY MESSAGE 2...Overall pattern evolves later this week as upper level ridge expands across the southeastern CONUS in response to deepening troughing over the Rio Grande Valley as well as a developing tropical cyclone (currently designated TD 9 and referred to as such for the remainder of the discussion) over the south- central Gulf. Conditions remain dry over the Carolinas, but the rising low- level thicknesses point to highs rebounding to above normal. Most inland areas will reach the low to mid 80s, with highs around 80 near-shore.

By the weekend, TD 9 is forecast to have strengthened and lifted northward towards the Gulf Coast, interacting with the mid-level trough. This evolution is complex and model guidance still shows some spread on its timing and track, especially as it migrates further inland. What is likely is east of TD 9 a warm front will lift northeast across the southeastern CONUS on the leading edge of the cyclone's deep tropical moisture. The potential for a wave of low pressure to develop along the front remains a low probability event based on 00z guidance trends, but given the aforementioned uncertainty trends will continue to be monitored.

Highest confidence remains around a moderate to heavy rainfall event across eastern NC. Timing of rainfall onset is a source of considerable uncertainty, with this morning's guidance suite now favoring a Saturday afternoon/evening and Sunday time frame. The AI guidance and the GFS have shifted more into this faster camp, while the ECMWF model remains slower (its AI counterpart, interestingly, favors a faster onset as well). Given this notable change, WPC has placed much of our area in a Marginal (Level 1 of 4) risk of excessive rainfall covering Sat AM to Sun AM. The probability for exceeding an inch of rain across all ensemble suites, regardless of timing, still remains around the 50-75% for much of the area. Probabilities of seeing rainfall exceeding 3" are now up to 25-30%, an increase from yesterday.

Guidance suggests minimal instability, but sometimes this type of setup can favor some shallow, rotating thunderstorms along the advancing warm front where southeasterly flow is enhanced.

AVIATION /10Z WEDNESDAY THROUGH SUNDAY/

Apart from some transient shallow fog around PGV, terminals remain VFR this morning. High pressure crests overhead keeping winds light and skies primarily clear. Tonight features another potential period of shallow fog with slightly better probabilities compared to yesterday with a modest uptick in low-level moisture, although increasing cirrus along the coast may hamper odds for MRH/OAJ/EWN.

Outlook: The overall pattern is expected to remain mostly unchanged through the end of the work week. Outside of a MIFG/BR/FG risk each night and morning, mostly VFR conditions are expected to prevail. The next chance for widespread sub-VFR conditions comes over the weekend as tropical moisture moves north into the area from off the Gulf and Southwest Atlantic. RA and potentially a TSRA risk looks to accompany the increased moisture as well.

MARINE

Marine conditions continuing to improve this morning with northeast winds easing to around 10-15 kt and seas falling to 3-4 feet nearshore. Winds continue to fall through the day as high pressure crests overhead, eventually veering southwesterly north of Oregon Inlet but remaining at around 10 kt or less. Seas fall to 2-3 feet nearshore later today and into tonight.

Outlook: Gradient is forecast to re-strengthen over the weekend as a front develops off the Southeast U.S. coast. This front will eventually lift north as a warm front as a tropical system in the Gulf lifts north through the Gulf Coast States and weakens. A period of moderate southeasterly winds is likely to accompany the front, with 20-30kt winds likely, along with seas building to 6-8ft at 7-8s. The evolution of this system remains complex and uncertain, so users should remain vigilant to future forecast adjustments.

MHX WATCHES/WARNINGS/ADVISORIES

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