FXUS62 KMHX 190005 AFDMHX Area Forecast Discussion National Weather Service Newport/Morehead City NC 805 PM EDT Wed Sep 18 2024 .SYNOPSIS... A weak cold front will cross the region tonight through Thursday producing unsettled conditions across eastern NC. High pressure will then build over the area over the weekend into early next week with mostly fair weather conditions expected. && .NEAR TERM /OVERNIGHT/... As of 745 PM Wednesday... - Monitoring potential for fog overnight Radar, satellite, and surface obs this evening reveal a cold front sagging slowly south across the NRN OBX/Albemarle Sound vicinity. Showers and thunderstorms associated with this front have shown a quick weakening trend over the past 30-60 minutes, likely due to increasing inhibition. Meanwhile, to the south scattered showers and thunderstorms are ongoing from NE SC into SE NC. This appears to be associated with a weak area of low pressure that has been drifting east along the NC/SC border over the past 24 hours. Downstream of this low, the airmass is only modestly unstable, and inhibition is increasing. In general, I expect this to keep the risk of thunderstorms low over the next few hours. However, as the low begins to lift NE into ENC, there may be just enough lift and instability to allow a few showers and isolated thunderstorms to fester through the evening and into tonight. This may especially be the case as the above- mentioned cold front continues to sag south, perhaps increasing low-level convergence and lift. The previous forecast handles this fairly well, so no significant changes were needed. We'll continue to monitor the shower/thunderstorm potential through the night, as some adjustments to the chance may be needed. Regarding the fog potential, recent guidance appears to be favoring more of a low stratus scenario, and less of a fog signal. Satellite imagery shows low clouds already beginning to spill slowly south out of NE NC, and this should continue to expand across the area overnight. I left a mention of fog in the forecast, but the risk of dense fog appears to be lowering. PREVIOUS FORECAST...Upper troughing persists with the remnants of PTC #8 over far western NC and SC. Off the VA/NC coast, a secondary low is gradually moving northeast. A stalled boundary across ENC will begin moving eastward this evening, which could spark some widely scattered showers and some isolated thunderstorms across the CWA. The best chance for this activity will be across far western and northern counties (north of Highway 70 and west of Highway 17). A slight chance (15-20%) of widely scattered showers will persist overnight with lows in the upper 60s to low 70s. Light winds and saturated soils will prime the environment for another round of fog and low stratus beginning around or just after midnight. The coastal plain will likely experience the most impactful fog with visibility down to a mile or less at times. && .SHORT TERM /THURSDAY/... As of 3:30 PM Wednesday...The mid/upper trough will deepen as it moves slightly to the east tomorrow. At the surface, two low pressure systems will be offshore: one off the SC/NC coast and another near DE/MA. Guidance shows a surface low developing over eastern North Carolina as the base of the trough swings through, which will be the main forcing mechanism for any shower or thunderstorm activity. Chances will increase through the day and peak in the afternoon (45-50% for the coastal plain, 25-40% for the beaches). Modest instability (MLCAPE 500-1500 J/kg) could support a few stronger thunderstorms, but these would be isolated in nature. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... As of 300 AM Wednesday...Mid/upper level trough lingering over the region through the end of the work week brings daily precip chances through Friday, and ridging starts moving in from the north and west through the weekend as a low spins up well offshore confining precip chances generally east of hwy 17 through the remainder of the long term period. Seasonable (or just below) temps through the period. Thursday: Mid and upper level trough starts shifting eastward over ENC Thursday and its surface counterpart low pressure system starts to strengthen offshore of the delmarva peninsula and NJ. We will have enough mid and upper level forcing directly above us paired with PWATs near 1.75" and CAPEs near 500-750 J/kg for scattered showers and thunderstorms (PoPs near 50%). Current expectation is for most of the convection to remain thunder free with lower instability, but if CAPEs start trending higher thunderstorm coverage would increase as a result. Deep Layer Shear generally below 20 kts will limit the severe potential and storms aren't expected to become tall enough for damaging microbursts. If there is any hazard to be mindful of Thursday, it would be slow to moderate storm motions allowing for rainfall to accumulate over areas that already have saturated soils from the recent rainfall. Northerly flow would allow the sea breeze to remain close to the coast (if it develops at all), which could cause problems for Carteret County as the sea breeze would provide additional stationary forcing. However this a low probability outcome and we will have a better idea once more hi-res guidance comes in. Showers and Tstorms will scour our with the loss of daytime heating Thursday evening/night. Friday: Mid/upper level trough starts moving offshore to the east Friday PM as high pressure starts moving in from the west. Decreased forcing and a drop in PWATs will lead to clearing skies and precip chances highest offshore and along OBX. Thunder possible offshore, but expecting just showers over land Friday. Rain chances east of hwy 17 are 20-30% Friday with drier condition expected for the coastal plain. Low continues meandering off the delmarva coast, sandwiched between ridging from all directions. The Weekend: Low precip chances, 10-20% for offshore and OBX, as low continues meandering to our east. Substantial ridging builds in over ENC from the north, which provides a stronger pressure gradient through the weekend and early next week. This will result in a slight uptick in winds, but skies are expected to remain partly/mostly cloudy through the weekend. Monday-Tuesday: Ridging and drier conditions continue through Monday, and Tuesday the high shifts offshore reintroducing slight chances of rain again. && .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... SHORT TERM /through 00z Friday/... As of 745 PM Wednesday... - Risk of IFR conditions expected to increase through the night - LIFR conditions possible tonight (30-50% chance) A weak cold front is forecast to sag slowly south through eastern NC late this evening and overnight, with an increased risk of IFR, or lower, conditions. IFR/LIFR CIGs are already ongoing across parts of the Northern OBX, and the expectation is for this to expand south through the remainder of ENC overnight. Guidance has trended more towards low CIGs/stratus, with a lower risk of FG. In light of this, I continued with more of a low stratus/BR scenario in the TAFs. If the low CIGs end up not as widespread overnight, then the risk of FG would increase. With daytime heating/mixing, CIGs should gradually improve, with MVFR conditions becoming increasingly likely by mid- morning. Lastly, the front moving in from the north, plus a weak low moving up from the south, will lead to a risk of SCT SHRA and a few TSRA. The highest TSRA risk is expected to be early this evening and again on Thursday. Confidence in TSRA is too low to mention in the TAFs for now, though. LONG TERM /Thursday night through Monday/... As of 400 AM Wednesday...Continued unsettled weather will bring a chance for brief/occasional sub- VFR conditions across ENC Thursday due to widely scattered to scattered mainly afternoon and early evening showers and thunderstorms. Friday onward VFR conditions expected, although Saturday morning could see some fog as skies clear and winds calm. && .MARINE... SHORT TERM /Through Thursday/... As of 745 PM Wednesday... - Quieter boating conditions Seas across the coastal waters are laying down quicker than anticipated, and the forecast has been adjusted to reflect this trend. PREVIOUS DISCUSSION...Sub-SCA conditions persist through the period. 3-5 ft seas will decrease to 2-4 ft by Thursday morning. Winds will remain around 10 kt or less through the period with variable wind directions becoming northwesterly by late tonight and northerly by Thursday afternoon. LONG TERM /Thursday night through Monday/... As of 400 AM Wednesday...Northerly winds increase to 10-15 kt Fri then become 15-20 kt Sat. and 20-25 kt Sunday. There is a 30-40% chance of seeing gale force gusts for the central and northern waters and the Pamlico Sound Sunday into early Monday. The strength of the winds depends on the position and strength of the low developing offshore to our northeast, and how strong the ridging pushing in from the north is. Seas will be 2-4 ft through Friday, then increase to 3-6 ft Saturday and 4-7 ft Sunday as gusty winds + the low offshore results in higher swell. && .TIDES/COASTAL FLOODING... As of 4 PM Wednesday...Coastal flooding will continue to be a risk given the higher than normal astronomical tide cycle. The Coastal Flood Advisory for Ocracoke has been extended and new Coastal Flood Advisories have been issued for all remaining oceanside coastal areas, which are currently set to last through Saturday. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...Coastal Flood Advisory until 10 PM EDT Saturday for NCZ195-196- 199-203>205. Beach Hazards Statement through Thursday evening for NCZ196- 203>205. MARINE...None. && $$ SYNOPSIS...MHX NEAR TERM...RM/OJC SHORT TERM...OJC LONG TERM...RJ AVIATION...RM/RJ MARINE...RM/OJC/RJ TIDES/COASTAL FLOODING...MHX