Area Forecast Discussion
Issued by NWS Newport/Morehead, NC
Issued by NWS Newport/Morehead, NC
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558 FXUS62 KMHX 112238 AFDMHX Area Forecast Discussion National Weather Service Newport/Morehead City NC 638 PM EDT Thu Jul 11 2024 .SYNOPSIS... A cold front will remain stalled across the region through Saturday with moist southerly flow bringing periods of heavy rain. The front will dissipate early next week with hot temps and the potential to heat indices in excess of 105 degrees returning. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 635 PM Thursday... - Flood/flash flood risk continues through tonight The organized convection from earlier today which produced Flash Flooding over the coastal plain has dissipated with the character of the precipitation becoming more disorganized and showery this evening. Expect this showery type regime to persist for most of the night then possibly becoming more organized again toward daybreak. This evening, a frontal boundary stretches SW to NE across the coastal plain of ENC. Showers and thunderstorms continue to redevelop along and east of this boundary thanks to a continued influx of a extremely moist, and very unstable, airmass into the area. Where showers and thunderstorms develop, the combination of 2000J/kg+ MUCAPE, 2-2.5" PWATs, and training of showers and storms will favor intense rainfall rates and an increased risk of flash and river flooding. While it has been dry of late, the rainfall rates will be high enough to overcome the dry soils, supporting the flood risk. In general, urban areas will be the most susceptible to flooding, but the risk won`t be limited to those areas only. Through this evening, then, the greatest risk of flooding will be over the coastal plain where earlier heavy rains occurred. Expect the flood threat to spread late tonight and especially Friday as an additional influx of moisture off the Atlantic will combine with an area of low pressure approaching the Carolina coast from the south, with a renewed round of showers and thunderstorms appearing likely per recent short-term guidance. There is still some uncertainty regarding where the strongest forcing will be focused, as this is where the heaviest rainfall rates, and highest risk of flooding, will be. Earlier, the Flood Watch was extended east to include most of ENC. For now, we left Ocracoke and Hatteras Islands out of the watch as confidence in rainfall amounts is lower there comparatively. We`ll re-assess those areas later as additional guidance comes in. Rain aside, winds are forecast to increase along the coast as southeasterly winds increase ahead of the approaching coastal low. For now, it appears winds will top out in the 20-35 mph range along the coast tonight. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... As of 230 PM Thursday... - Renewed flood/flash flood threat Friday A coastal low will approach ENC from the south and will interact with a stalled frontal boundary, a very moist airmass (2-2.5" PWATs), and moderate instability, leading to additional rounds of showers and thunderstorms capable of intense rainfall rates. Instability Friday looks lower than today, but increased forcing is expected along/near the track of the coastal low, which should still be supportive of heavy rainfall rates/amounts. Ensemble guidance suggests 3-6" of rain for much of the area, with higher end amounts up to 7-10" where thunderstorms are the most intense/persistent. We`ll continue to refine the risk areas through Friday, but confidence is high enough to warrant a continuation of the Flood Watch into Friday evening. Breezy onshore winds will continue along the coast as well, as the coastal low approaches from the south. Southeasterly winds of 20-35 mph will be common. If the low were to deepen more than currently forecast, those winds would top out a bit higher. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... As of 330 AM Thursday... Key Messages: -Very wet period expected into Saturday, with heavy rain chances likely (70-80%) at times with localized flooding possible. Severe threat remains relatively low at this time. 4-6 inches of rain possible west of highway 17. -Warm and humid conditions continue. Sunday through Wednesday heat indices of 105-110 degrees are possible each day. Not many changes to the forecast over the last 24 hours. Wet and warm will be the story for the long term forecast as a frontal system extending southward into the Carolinas remains nearly stationary through Saturday. This feature will remain between high pressure offshore and lower pressure to the north and west. This pattern will facilitate extremely efficient moisture transport off of the Atlantic over the Carolinas. This is highlighted by the ECMWF extreme forecast index which is showing anomalously high precipitation values over the Carolinas. In addition model soundings show PW values approaching 2.5 inches at times. While there will also be a chance for thunderstorms each day, the chances for severe weather remain underwhelming. While there will certainly be enough moisture and instability to initiate convection, shear values are lacking. Thus the heavy rain is the primary threat during this time period. Not to be overlooked in the long term is the threat for extreme heat, particularly beginning on Sunday through Wednesday. Expect high temperatures in the low to mid 90s inland with upper 80s to low 90s along the coast. Heat index values will push or exceed 105 degrees each day in most locations except the extreme coastal areas. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... SHORT TERM /Through Friday/... As of 635 PM Thursday... - TSRA and sub-VFR conditions to impact ENC through Friday The combination of a stalled front, a coastal low approaching from the south, and a very deep moist airmass will support an increased risk of SHRA and TSRA through Friday for much of Eastern NC. Timing out the greatest chance of SHRA and TSRA at any one TAF site will be complicated, but occasional to frequent showers should be a threat for the next 36-48 hours. Where TSRA occur, periods of LIFR/IFR conditions can be expected due to very heavy rainfall rates. Gusty winds will be possible as well, especially along the coast as the low approaches. The aviation ceiling guidance is indicting varying ceilings through the period with MVFR being the prevailing category through Fri. LONG TERM /Friday night through Tuesday/... As of 330 AM Thursday... For Saturday expect periods of sub VFR conditions as heavy rain is expected across eastern NC. Precipitation will affect ceilings and visibilities during the heaviest rainfall and overnight periods. Rain is expected to continue through Saturday and possibly into Sunday before tapering off early next week. Thunderstorms are also possible during this time, particularly in the afternoons but severe weather is unlikely. Winds will keep a southerly component at 5-10 knots gusting to 15 kts. && .MARINE... SHORT TERM /Through Friday/... As of 635 PM Thursday... - Deteriorating boating conditions through Friday A coastal low approaching from the south will lead to building winds and seas tonight into Friday, with 15-30kt southeasterly winds, and seas peaking as high as 4-8 ft. Of note, the potential exists for stronger winds and higher seas depending on the strength of the low as it approaches the southeast coast. SCA headlines continue to cover these hazards, with adjustments made to account for recent trends in model guidance (ie. mainly to increase winds). LONG TERM /Friday night through Tuesday/... As of 330 AM Thursday...Small craft conditions will likely continue across the central and southern waters through Saturday afternoon with wind gusts approaching 25 kts and seas near 6 ft. For Pamlico Sound, expect SCA conditions to relent Saturday morning. Waves and winds will relax for Sunday and into the middle part of next week. && .HYDROLOGY... As of 230 PM Thursday... Despite high flash flood guidance values (3-5") across much of ENC, intense rainfall rates of 2-3"/hr have been overcoming the dry soils of late, leading to increased runoff and flood/flash flooding impacts. This has especially been the case in urban areas where dry soils have less of an impact. A Flood Watch has been issued for much of ENC, and is in effect through late Friday evening. This may need to be adjusted in time and area depending on how conditions evolve over the next 24-36 hours. Ensemble guidance shows rainfall amounts of 3-6" through Friday night, with amounts as high as 7-10" where rainfall is the most persistent and where thunderstorms materialize. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...Flood Watch through Friday evening for NCZ029-044>047-079>081- 090>092-094-193>196-198-199-203. Beach Hazards Statement until 8 PM EDT this evening for NCZ195- 196-199-204-205. MARINE...Small Craft Advisory until 8 PM EDT Saturday for AMZ135-152- 154-156-158. Small Craft Advisory from midnight tonight to 6 PM EDT Friday for AMZ136-137. Small Craft Advisory until 6 PM EDT Saturday for AMZ150. Small Craft Advisory until 8 PM EDT Friday for AMZ231. && $$ SYNOPSIS...MHX NEAR TERM...RM/JME SHORT TERM...RM LONG TERM...RTE AVIATION...RTE/RM/JME MARINE...RTE/RM/JME/RCF HYDROLOGY...MHX