Area Forecast Discussion
Issued by NWS Newport/Morehead, NC
Issued by NWS Newport/Morehead, NC
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471 FXUS62 KMHX 150840 AFDMHX Area Forecast Discussion National Weather Service Newport/Morehead City NC 440 AM EDT Sun Sep 15 2024 .SYNOPSIS... High pressure remains wedged across the mid-Atlantic while low pressure developing off the southeastern coastline drifts northward today and Monday. Troughing will remain over the Eastern Seaboard through next week as well keeping unsettled conditions across ENC. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 400 AM Sun...Weather pattern remains largely stagnant this morning as strong mid-level ridge continues to wobble over the northeastern CONUS while weak low pressure continues to slowly organize along a stalled frontal boundary off the coast of South Carolina. At the surface, high pressure wedge continues to hold strong over the mid-Atlantic and central Carolinas while the Gulf Stream low remains stationary. There is a very weak offshore trough north of Cape Hatteras that is acting to support some very light shower activity across the north, but this is expected to dissipate later today. This pattern will not change much in the near term. The upper ridge is keeping deeper moisture and stronger lift shunted just south of our area (seen on radar as heavier rainfall is focused along and south of Cape Fear), and apart from a few stray showers along the southern coast (and, at least for the morning, the northern tier) dry conditions prevail. Widespread cloudiness continues thanks to moist easterly onshore flow, and expect this to hold through the day. Like yesterday, expect precipitation coverage to expand modestly in the afternoon with a stray thunderstorm possible as CAPEs hover between 500-1000 J/kg. Most likely areas to see rain remain along area beaches. NE to E winds continue to steadily increase through the day as the Gulf low slowly strengthens. At their peak, winds this afternoon will reach 15-20 mph with frequent gusts up to 30 mph (up to 35 mph OBX). Highs remain modestly below average as low dense overcast inhibits insolation, in the low 80s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... As of 400 AM Sun...Gulf low will begin to gradually lift northward overnight as upper ridge weakens. Isolated to widely scattered shower activity will persist along the coast through much of the overnight hours, especially along the Crystal Coast, but heavier rainfall is expected to encroach from the south as early as Monday morning as deeper plume of 2"+ PWATs drifts back northward. Rainfall totals overnight will remain relatively light (a half inch or less), with more robust precipitation expected during the day Monday. Prior to the onset of rain, cloudy and breezy conditions persist overnight as lows once again hover in the upper 60s to low 70s. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 4 AM Sun... Eastern North Carolina will remain unsettled through the entire period as an impactful low looks to bring several hazards to the area Mon into Tue. Beyond that, troughing over the Eastern Seaboard will continue to bring daily chances for showers and thunderstorms across the region into next weekend. Monday and Tuesday...We start the long term period out with unsettled weather. The upper levels will be denoted by deepening troughing across the Southeast. As this trough deepens, an incoming shortwave from the west will round this troughs base. At the same time, a mid level low off the Southeast Coast tracks north to northwest towards the Carolinas and becomes absorbed within this deepening trough on Tue. At the surface, our main weather maker for Mon and Tue will be impacting the area. Low pressure system is currently in the process of developing and is attached to a frontal boundary off the Southeast Coast. Latest guidance still continues to deepen the low on Sun detaching it from the aforementioned frontal boundary with this surface low then tracking north to northwest and potentially gaining sub- tropical or tropical characteristics as it nears the coast on Mon. The low then continues inland on Tue eventually lifting north of the region by Tue afternoon allowing for much more benign weather to finally begin to overspread ENC for at least a brief time period Tue afternoon and evening. If this forecast were to hold, this would bring heavy rain (with HREF neighborhood probs of >5" of rain over 24 hours close to 40-60% along the Crystal Coast and closer to 10-30% further north), a low end severe threat, gusty winds with the potential for widespread 25- 35+ mph E`rly wind gusts, dangerous marine conditions, minor coastal flooding, beach erosion, and ocean overwash to ENC. (SEE COASTAL FLOODING AND HYDRO SECTION FOR MORE INFORMATION) Have two important caveats to the above however. The first is, regardless if this system remains non-tropical or gains sub- tropical or tropical characteristics, impacts will be similar so don`t latch on to whether it become tropical or not. The second is, even with us getting close to the time this low will begin to impact the area, there still remains lower than average confidence with the lows eventually track and strength which will have significant impacts to the conditions we see from this low. Latest 00Z guidance has shifted south with GFS ensembles latching on to more of a southern NC or even SC landfall as early as tonight while EURO ensembles still promote a threat from SC to the Crystal Coast while also being weaker and slightly slower to reach the coast than the 12Z ensemble guidance. With this in mind continue to keep a close watch on the latest forecast as any shifts in this lows eventual track and timing will have significant impacts on the forecast going forward. Otherwise expecting below avg temps across ENC Mon and Tue with highs only getting into the 70s to low 80s each day while lows get down into the 60s to low 70s. 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 is increasing uncertainty with the forecast as the upper trough over the Eastern Seaboard looks to cutoff into an upper low in the Southeast as upper ridging builds across the Northeast but there is a rather large spread in timing and depth of the cutoff low this weekend across all available guidance so the forecast beyond Friday is low confidence. Either way, daily chances for showers and thunderstorms will remain possible across ENC into the weekend as troughing continues to remain a focus for shower and tstm activity. Will note however, winds will finally ease by Wed as the pressure gradient relaxes as a weakness in the ridge centered to our north briefly develops, though a second ridge of high pressure does begin to extend south into the area by Friday. Otherwise continued onshore flow will keep clouds around the region while temps remain at or below avg. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... SHORT TERM /through 06Z Mon/... As of 145 AM Sun...Primarily MVFR conditions in place early this morning in steady northeasterly flow between the inland wedge of high pressure and a developing low a couple hundred miles offshore to our south. Cig heights have been drifting lower this morning and would not be surprised to see some brief drops to IFR in the pre-dawn hours. Expanded TEMPO IFR forecast to both PGV and ISO. Along the coast, weak band of broken showers will continue through much of the period, posing a risk mainly for EWN/OAJ. Conditions are forecast to improve to VFR during the day as winds increase markedly, gusting up to 20-25 kt in the afternoon hours inland (and up to 30 kt for OBX terminals) with shower and iso thunder risk persisting, still focused along the southern coast. Lower cigs return from south to north tonight into Mon morning as low lifts towards the Carolina coast, although confidence in their onset timing is lower than average. LONG TERM /Sunday Night through Wednesday/... As of 4 AM Sun... Continued unsettled weather will bring daily chances for sub-VFR conditions across ENC especially Mon and into Tue as a low pressure system is forecast to impact the area bringing a threat for widespread shower and thunderstorm activity as well as low clouds and reduced visibility. Winds will generally remain NE-E at 10-20 kts with gusts up near 20-30 kts through Monday before winds shift to a more SE`rly direction and become much lighter closer to 5-10 kts Tue into Wed as the aforementioned low moves to the north. After the low moves to the north we will still see at least a low end threat on Wed and Thurs for sub-VFR conditions as daily chances for afternoon and evening showers and thunderstorms will remain. && .MARINE... SHORT TERM /through Sunday/... As of 420 AM Sun...Roughly marine conditions already in place this morning as a Gulf Stream low meanders south of a persistent high pressure ridge over the central Carolinas, resulting in breezy northeasterly winds across the waters. Latest observations show speaks of 15-25 kt with frequent gusts up to 30 kt. Seas are now averaging 7-10 feet across all zones. Winds will continue to slowly increase through the day as the aforementioned low begins to lift north. Guidance shows high probabilities (>80%) of Gale force gusts starting across the outer portions of Raleigh and Onslow Bays by sunrise this morning, persisting for the next 24 hours. Because of this, upgraded the Gale Watch to a Warning for the waters south of Cape Hatteras. Strong SCA conditions are still expected across all remaining waters, and no other changes to headlines were made. Seas continue to build, reaching a peak of 10-15 feet just before dawn on Monday south of Hatteras. LONG TERM /Sunday Night through Wednesday/... As of 4 AM Sun... Dangerous marine conditions are still forecast across our waters on Mon and Tue as a low pressure system impacts the Carolinas during this timeframe. Latest guidance suggests we start the period out with widespread 20-30 kt NE-E winds with gusts up around 30-35 kts as well as widespread 8-12 ft seas across our coastal waters. This will keep any ongoing SCA`s in place on Mon and while recently hoisted gale warnings should end by 12Z Mon there is a low end threat if aforementioned low is slightly stronger than currently forecast low end gale conditions could persist into Monday morning across our southern waters before easing. As low moves inland Mon night into Tue expect marine conditions to 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. This should allow our inland rivers and sounds to fall below SCA criteria by Tue morning. Winds and seas fall even further Tue and 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 425 AM Sun...Widespread heavy rain is expected late tomorrow through Tuesday as low pressure develops to our south and pushes northward. Abundant tropical moisture with this system will lead to extremely heavy rainfall rates over areas that have become saturated over the last week. Where the heaviest rainfall sets up remains uncertain due to larger than average spread in model guidance, but confidence in heaviest rainfall remains highest along the Crystal Coast where storm total 4-6 inches of rain is possible. A more widespread 2-4 inches is forecast for the rest of ENC. Because of the aforementioned model spread, opted to delay any flood headlines until later today. && .TIDES/COASTAL FLOODING... As of 435 AM Sun...There will be potential for minor to moderate coastal flooding early this week as winds strengthen in association with a developing low pressure system to our south over the Gulf Stream. Additionally, coastal flooding may be worsened due to the astronomically high tide cycle we are entering. Ahead of this system, strong NE/ENE winds will buildup water along the SE portion of the Pamlico Sound as well as the Neuse, Bay, and Pamlico Rivers. Oceanside, high water levels in addition to strong wave run up will likely produce ocean overwash along NC 12 on the Outer Banks at times of high tide. The severity of these potential impacts is not yet fully known due to the difference in track and intensity solutions for this low pressure system. Additionally with this system we can expect a high threat of rip currents, rough and dangerous surf/shore break, and beach erosion. Forecast impacts changed little this morning. Coastal Flood Advisories for 1-2 feet of inundation above ground level remain for the Outer Banks as well as areas along the aforementioned inland rivers, running from this afternoon to late Monday. A High Surf Advisory remains for all area beaches running until Tues AM. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...Coastal Flood Advisory from 2 PM this afternoon to 9 PM EDT Monday for NCZ080-094-194>196-199-203>205. Beach Hazards Statement from 8 AM EDT this morning through this evening for NCZ195-196-199-203>205. High Surf Advisory from 2 PM this afternoon to 8 AM EDT Tuesday for NCZ195-199-203. High Surf Advisory until 8 AM EDT Tuesday for NCZ196-204-205. MARINE...Small Craft Advisory until 8 AM EDT Tuesday for AMZ131-135>137- 230-231. Small Craft Advisory until 8 AM EDT Wednesday for AMZ150-152. Gale Warning until 8 AM EDT Monday for AMZ154-156-158. && $$ SYNOPSIS...MHX NEAR TERM...MS SHORT TERM...MS LONG TERM...RCF AVIATION...MS/RCF MARINE...MS/RCF HYDROLOGY...MHX TIDES/COASTAL FLOODING...MHX