Area Forecast Discussion
Issued by NWS Newport/Morehead, NC
Issued by NWS Newport/Morehead, NC
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586 FXUS62 KMHX 170552 AFDMHX Area Forecast Discussion National Weather Service Newport/Morehead City NC 152 AM EDT Tue Sep 17 2024 .SYNOPSIS... An area of low pressure will continue to shift further inland and away from the coast tonight. Troughing will remain over the Eastern Seaboard through next week as well keeping unsettled conditions across ENC. && .NEAR TERM /THROUGH TONIGHT/... As of 815 PM Monday... - Flash flooding risk continues overnight Surface observations and regional radar show an area of low pressure centered near Lumberton, NC. East of the low, a confluent, and very moist, low-mid flow continues to support bands of heavy rain and embedded thunderstorms pivoting W/NW through the southern half of ENC. While convection within these bands has shown some signs of weakening, radar is still estimating 1"/hr+ rainfall rates is occurring at times. As the SFC low drifts westward, guidance is insistent that the ongoing bands of rain will shift northward as an associated frontal boundary lifts north. However, short-term guidance differ on how quickly this northward progression will occur. The timing difference lends itself to very different rainfall outcomes through the night. The slower guidance, for example, suggests another 3-6"+ of rain over the southern half of ENC, while the quicker guidance keeps amounts lower thanks to the more progressive nature of the rain. The slower guidance are favored at this time, based on trends seen on radar and satellite, and given the general synoptic pattern. In light of this, the heaviest rainfall through tonight is forecast to fall over already saturated soils, leading to a heightened flood/flash flood through the night. A large Flash Flood Warning was recently issued to capture the area most at risk through midnight. We`ll continue to evaluate this potential and issue additional warnings as necessary. The Flood Watch continues, and not changes were needed to that area. One note about the flash flooding potential. Some of the worst- case guidance is suggestive of additional rainfall amounts of 5-10" possible near the coast. Should this occur, there would be a much higher flash flood risk, which would be more problematic given that this would occur at night. Stay tuned for updates on the flash flood potential. Forecast-wise, a kept a higher chance of rain and storms across our southern counties, with the assumption that the bands of rain will be slower to lift north. Otherwise, the forecast is on-track, and no other major changes were needed. PREVIOUS DISCUSSION...Low pressure continues to move onshore with its rainbands dumping heavy rainfall across the Carolinas, especially in the Wilmington, NC area. This system has been slowly (5 mph) moving towards the NNW, but it will pick up speed as it gets picked up by the upper ridge. The hazards from this low pressure will be flash flooding, coastal flooding, and tornadoes. - Flash Flooding: As the system moves NNW, the axis of heavy rainfall (PWATs of 2-2.25") will transition from the southwestern to northeastern region of the FA. QPF has remained roughly the same for areas north of HWY 70 but has increased for areas to the south. Areas north of HWY 70 are expected to get 2-3" while areas south of HWY 70 are in the 4-7" range with locally higher amounts up to 8-9" possible. A Flood Watch is in effect for the entire area, but the highest likelihood to see flooding remains south of HWY 70. - Coastal Flooding: The coastal flooding threat remains largely unchanged, with the potential for up to 3 feet of water AGL in low lying areas. See the TIDES/COASTAL FLOOD section for more details. - Tornadoes: The current forecast track of the low brings the tornado-favorable right front quadrant across eastern NC. The highest low level helicity will be displaced to our west, along the I-95 corridor, but 0-3 km SRH of 100-250 m2/s2 combined with afternoon CAPEs between 1000-1500 J/kg support at least an isolated risk of a brief tornado or waterspout especially this afternoon and early evening. - Strong Winds: Winds will strengthen to 30-40 mph along the coast today, especially south of Ocracoke Island. Sporadic wind gusts up to 50 mph are possible in passing rain bands. These may cause sporadic power outages and/or tree damage. The axis of deepest moisture will transition northeastward overnight. Greatest rainfall amounts will likely be along and just north of HWY 70 with overnight QPF in the 2-3" range. Dry air entrainment will start to cut PoPs back from south to north late tonight and temps will reach the low 70s. && .SHORT TERM /WEDNESDAY THROUGH 6 PM TODAY/... As of 3 PM Monday...The axis of deeper moisture will continue its northeastward movement into tomorrow morning, which will bring the focus of heaviest rain to the Outer Banks. The QPF in this area is 1-2" with locally higher amounts possible in stronger rainbands. The Flood Watch for areas south of HWY 70 is scheduled to drop at 8 AM while the Flood Watch for areas north of HWY 70 is scheduled to drop at 2 PM.The low will finally lift north of the area tomorrow afternoon. This will decrease PoPs from south to north through the day. Highs will be in the low 80s for everywhere except the Northern Outer Banks where longer lasting rain will keep high temps in the upper 70s. && .LONG TERM /TONIGHT THROUGH MONDAY/... As of 400 AM Mon... Eastern North Carolina will remain unsettled through the entire period as an impactful low moves out of the area Tuesday. Beyond that, troughing over the Eastern Seaboard will continue to bring daily chances for showers and thunderstorms across the region into next weekend. Wednesday into the weekend... Previously mentioned upper trough will remain over the Eastern Seaboard through the end of the week while at the surface previously mentioned low is forecast to be to the north and likely dissipated. As we get into the weekend, there remains uncertainty with the forecast as the upper trough over the Eastern Seaboard is forecast to cutoff into an upper low as upper ridging builds across the Northeast. As is typical with upper lows, spread in timing and depth of the feature remains large and forecast confidence remains below average. Either way, daily chances for showers and thunderstorms will remain possible across ENC into the weekend as favorable troughing remains overhead. Continued onshore flow will keep clouds around the region while temps remain at or below avg. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... SHORT TERM /through 06z Wednesday/... As of 150 AM Tuesday... Occluded surface low is migrated across the NC/SC border early this morning with a persistent band of showers and thunderstorms overspreading all terminals. Flight conditions, outside of convection, are generally MVFR closer to the coast but more IFR across the coastal plain. All sites are likely to see brief drops to IFR in the band of heaviest showers, which is lifting north of a line from OAJ/NJM this hour. Near term cig trends are difficult to discern, but current thinking is prevailing cigs should continue until mid-morning when all sites eventually lift back to MVFR with daytime heating. What areas eventually scatter out to VFR remains a point of uncertainty, with the greatest odds of this from ISO/EWN southward. Conditions look favorable for low stratus and low visibilities Tues PM as wind fields collapse but low-levels remain heavily saturated. LONG TERM /Tuesday through Friday/... As of 405 AM Mon...Continued unsettled weather will bring a chance for sub-VFR conditions across ENC tomorrow as a low pressure system moves out of the area. After the low moves to the north we will still see at least a low end threat for the rest of the week for sub- VFR conditions as daily chances for afternoon and evening showers and thunderstorms will remain. && .MARINE... SHORT TERM /Today and Tonight/... As of 1100 PM Monday... Winds have begun to decrease across the inland rivers and sounds, and are now easterly around 10-20kt. There may be a brief bump in winds as bands of rain and thunderstorms move through overnight, but the risk of sustained gusts above 25kt is decreasing. PREVIOUS DISCUSSION...Dangerous boating conditions are ongoing this afternoon as winds remain strong on the northern periphery of an area of elongated low pressure impacting the Carolinas. Observations south of Cape Lookout show easterly winds of 20-30 kt, with seas ranging 8-11 feet. Strongest winds will be focused over Onslow Bay and southern Raleigh Bay this afternoon with gusts up to 35-40 kt. Farther north, winds are slightly weaker but still peak at 25-30 kts. Winds will peak this afternoon, then subside as the low shifts onshore and fills. Seas will continue to be quite hazardous today, peaking at 10-14 ft. Conditions begin to slowly improve into Tues morning. LONG TERM /Tuesday through Friday/... As of 415 AM Mon...Dangerous marine conditions continue into Tuesday, but gradually improve from south to north with winds easing down to 15-20 kts with gusts up around 20-25 kts by Tue morning and veering to a SE and eventually SW direction while seas fall down to 5-8 ft along our coastal waters. Winds and seas fall even further Wed with winds remaining S`rly at 10-15 kts while seas along our coastal waters finally lower down to 3-5 ft by Wed morning. This should then end SCA criteria across all waters with more benign boating conditions forecast for Thurs. Daily chances for showers and thunderstorms will remain possible through the period with locally enhanced winds and seas possible within the strongest storms that may develop. && .HYDROLOGY... As of 1100 PM Monday...Bands of heavy rain will continue to slowly pivot through ENC overnight and into Tuesday, producing periods of intense rainfall rates of 1"/hr+. Despite some disorganization of the bands at this time, there will continue to be flash flood risk overnight. The risk may then increase on Tuesday as heating and renewed destabilization supports increased rainfall rates. So far today the axis of heaviest rainfall has been along Duplin and Onslow Counties, and this will transition to the north and east as the low moves inland. Areas north of HWY 70 are expected to get 2-3" while areas south of HWY 70 are in the 4-7" range with locally higher amounts up to 8-9" possible. && .TIDES/COASTAL FLOODING... As of 1100 PM Monday... Coastal flooding will continue to be a risk through at least one more high tide cycle on Tuesday morning, and the Coastal Flood Advisories have been extended to capture this potential. With this week being a higher tide cycle, in general, the risk of coastal flooding may linger beyond Tuesday, and adjustments to the advisories may be needed. PREVIOUS DISCUSSION...Additionally with this system we can expect a high threat of rip currents, rough and dangerous surf/shore break, and beach erosion. Current Coastal Flood and High Surf headlines remain unchanged with the afternoon update. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...Flood Watch through this afternoon for NCZ029-044>047-079>081- 203>205. Coastal Flood Advisory until 8 AM EDT this morning for NCZ080- 094-194>196-199-203>205. Flood Watch until 8 AM EDT this morning for NCZ090>092-094- 193>196-198-199. High Surf Advisory until 8 AM EDT this morning for NCZ195-196- 199-203>205. Beach Hazards Statement from 8 AM EDT this morning through this evening for NCZ195-196-199-203>205. MARINE...Small Craft Advisory until 6 AM EDT Wednesday for AMZ150-152- 154. Small Craft Advisory until midnight EDT tonight for AMZ156-158. && $$ SYNOPSIS...MHX NEAR TERM...RM/OJC SHORT TERM...OJC LONG TERM...MS AVIATION...MS MARINE...RM/MS/OJC HYDROLOGY...MHX TIDES/COASTAL FLOODING...MHX