Area Forecast Discussion
Issued by NWS Newport/Morehead, NC
Issued by NWS Newport/Morehead, NC
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213 FXUS62 KMHX 261132 AFDMHX Area Forecast Discussion National Weather Service Newport/Morehead City NC 732 AM EDT Thu Sep 26 2024 .SYNOPSIS... The upper ridge will move little today but the pattern is becoming progressively more unsettled as Hurricane Helene lifts across the eastern Gulf of Mexico and into the southeastern CONUS. Friday will bring unsettled weather as some impacts from Helene are felt, and then upper low pressure may bring some occasional showers late weekend into early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 3:30 AM Thursday...The upper level ridge will remain anchored off the east coast today. The upper trough will continue to dig further into the Mississippi River Valley and has become cut off while Hurricane Helene is intensifying as it approaches the The Big Bend of Florida. Widely scattered showers and isolated thunderstorms will overspread ENC today, but our proximity to the offshore upper ridge will provide some mid-level subsidence, which may minimize deeper convection along the northern tier of the FA. With bands of convection moving onshore, severe storms will be a possibility throughout the day, especially south of Highway 70. SPC has outlined the southern half of the CWA in a Marginal Risk (Level 1/5) for the potential of damaging wind gusts and an isolated tornado. With the outer bands of Helene pumping ample moisture into the Carolinas (2-2.5 PWATs), some heavier showers can be expected, and any training cells could produce localized flooding issues. Warm SSTs, strong deep layer shear, and marginal instability (MLCAPE 500- 1000 J/kg) could support the formation of waterspouts. The Crystal Coast will need to be watched the closest for this activity. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... As of 3:30 AM Thursday...The concern for severe hazards increases as we move into the overnight hours. PoPs will increase from southwest to northeast after midnight as more powerful bands of Helene move across the area. The late overnight/early Friday morning hours will host a heightened threat for heavy rainfall, tornadoes, waterspouts, and damaging wind gusts. Again, any training cells could produce localized flooding issues. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... As of 4 AM Thu... Friday...The main item of interest will be the impacts from TC Helene. The center of the storm will be moving through GA and then into the TN Valley Friday morning. With the large size of the system, and psudo warm front moving through the ctrl/ern Carolinas, a heavy rain band or two will be propagating through ENC during the day. Strong moisture advection east of the center should allow a plume of tropical moisture to quickly overspread the coastal Carolinas throughout the day from w to e. At the same time, a broadly diffluent flow aloft plus increasing WAA should support a period of strong forcing, leading to a quick period of moderate to heavy rain and scattered thunderstorms, some of which may become severe and contain a few tornadoes. SFC based CAPEs inc to aoa 1,500 J/KG with plume of mid/upr 70s TD`s overspreading the region. Strong backing of sfc winds to the SE will produce significant low lvl helicity values (300-400 M2/S2), and a favorable environment for a couple tornadoes will be in place, as indicated by large hodograph structures acrs ENC. SPC has upgraded the marginal risk that was in place to a slight risk. Concerning heavy rain threat, while quick- hitting, guidance has been showing a consistent signal for a brief period of heavy rain and localized flooding, though the good news is the band or bands of heavy rain will be progressing eastward fairly quickly, with rain ending by mid to late afternoon for most areas inland, and all areas including the OBX by early evening. Attm, 0.75" to 1.00" are forecast, with locally higher amounts in heavier cells. Breezy conditions will be present as well, with sserly breezes gusting to 20-25 mph inland, with 30+ mph close to the coast. Quick drying with all rain ending and winds diminishing rapidly and becoming swrly Fri evening, with temps still muggy in the low 70s. Saturday...Mainly dry with subsidence in place behind the system, and upr low pres well west of ENC. Warm and humid continues with swrly flow, and highs well into the mid to perhaps a few upper 80s. Heat indices will be in the low 90s. Sunday through Tuesday...Aforementioned upr low migrates slowly eastward, with chances for showers each day, with perhaps a surface low developing near or over ENC. Have capped pops at 30% attm due to uncertainty on synoptic and mesoscale features this period. Temps will cont to near or slightly above climo, with highs in the low/mid 80s to 60s to around 70 for lows. Wednesday...The upper low should finally exit the region and offshore by mid week, with broad nwrly flow ensuing and bringing drier and cooler air back to the region. Temps should drop back down to around climo with highs in the 75-80 range for most, and lows upper 50s to low 60s. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... SHORT TERM /through today/... As of 7:30 AM Thursday...Low clouds around 3-4 kft will linger today with scattered showers and thunderstorms possible across the FA, which could introduce brief interruptions to otherwise low-end VFR conditions. As we get into the evening and overnight hours, the signal for sub-VFR flight cats becomes much greater. Shower and thunderstorm chances will increase late tonight/early Friday morning and will be accompanied by gusty winds (15-20 kt) as stronger rainbands from Hurricane Helene move across the area. Some storms may be strong to severe. LONG TERM /Fri through Mon/... As of 4 AM Thu...A tropical system is forecast to pass well west of eastern NC, but still be close enough to produce a period of gusty winds, RA, TS, and sub- VFR conditions during the day Friday. VFR returns by evening as drier air moves in behind the system. Sat should remain dry, though ocnl showers will be possible Sun through early in the week as upr low pressure will migrate through the region. && .MARINE... SHORT TERM /Through tonight/... As of 3:30 AM Thursday...Marine conditions will deteriorate through the period. The wind field will stay generally southeasterly but will increase from south to north through the day. The coastal waters south of Cape Hatteras are currently 10-15 kt and will increase to 20-25 kt with gusts to 30+ kt by tonight. The coastal waters north of Cape Hatteras will increase from 10 kt to 15-20 kt with gusts to 25 kt. Seas south of Oregon Inlet are currently 5-6 ft at 11-13 seconds and will increase to 7-9 ft by late tonight. Seas off the NOBX will remain around 5-6 ft through the period. Given these conditions, SCAs are in effect for all coastal waters through the period. LONG TERM /Fri through Mon/... As of 4 AM Thu...On Fri, gradient inc to 20-25 kt sustained and gusts to 30 kt for the coastal waters and seas build to 7-10 ft with the sserly winds. A few gusts to 34 kt possible briefly for the ctrl/srn waters south of Hatteras during the day Fri. Winds quickly diminish Fri night, though high seas will be slow to respond and remain above 6 ft into Sat. Sun into early next week will bring lighter winds of 5-15 kt and seas of 2-4 ft. && .TIDES/COASTAL FLOODING... As of 4 AM Thu...The coastal flood threat continues for all of coastal North Carolina through today as tide levels remain elevated, including the Neuse, Bay, Pamlico, and Pungo Rivers as reported water levels remain elevated. Water levels will continue to trend slightly lower, but will still remain high enough to result in up to a foot of inundation. Along and north of Ocracoke, swell offshore is weakening but may still result in some minor overwash where dune structures are compromised or vulnerable. Looking ahead, we`ll continue to closely monitor the track of TC Helene as coastal impacts could be felt across a portion of ENC on Fri into Fri evening thanks to southerly onshore winds and large waves, and coastal flood advisories will likely have to be continued for mainly oceanside zones from Hatteras Island southward. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...Coastal Flood Advisory until 6 PM EDT this evening for NCZ080- 094-194>196-199-203>205. High Surf Advisory from 3 AM Friday to 4 AM EDT Saturday for NCZ195-196-199-204-205. Beach Hazards Statement through this evening for NCZ196- 203>205. MARINE...Small Craft Advisory from 10 AM to 6 PM EDT Friday for AMZ131- 136-137-230-231. Small Craft Advisory from 6 AM to 6 PM EDT Friday for AMZ135. Small Craft Advisory until 7 AM EDT Saturday for AMZ150. Small Craft Advisory until noon EDT Saturday for AMZ152-154- 156-158. && $$ SYNOPSIS...MHX NEAR TERM...OJC SHORT TERM...OJC LONG TERM...TL AVIATION...TL/OJC MARINE...TL/OJC TIDES/COASTAL FLOODING...MHX