Area Forecast Discussion
Issued by NWS Wakefield, VA
Issued by NWS Wakefield, VA
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722 FXUS61 KAKQ 262021 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 421 PM EDT Thu Sep 26 2024 .SYNOPSIS... Hurricane Helene intensifies today, making landfall on the Florida Gulf Coast early tonight. The remnants of Helene will then pass well west of the area on Friday. Drier conditions briefly return on Saturday, followed by unsettled weather Sunday through next Tuesday. && .NEAR TERM /THROUGH FRIDAY NIGHT/... As of 330 PM EDT Thursday... Key Message: - Isolated to scattered showers redevelop this afternoon, mainly W of I-95, with only a slight chance to the east. - Widespread showers and isolated thunderstorms expected Friday, associated with the remnants of Tropical Cyclone Helene. Heavy rain and brief tornadoes are the main threats. The main wx story regionally (and nationally) remains Hurricane Helene in the eastern Gulf of Mexico. As of a 230 PM special NHC advisory, max sustained winds have increased to near 120 mph. Ahead of Helene, high pressure is gradually shifting further offshore from Atlantic Canada, leading to rather light SE/ESE flow over the region. An expansive shield of precip extends northward from Helene, with a predecessor (PRE) rainfall event ongoing in the higher terrain of SC/NC/VA. Aloft, a sprawling upper low is situated over the mid MS Valley. Temps are generally around 80 F this afternoon and highs will average 80-82, except upper 70s along the immediate coast. Light radar echoes are noted over our far western counties, but this does not appear to be reaching the ground as of this writing. For the rest of this afternoon into this evening, showers currently over central NC are forecast to spread northward into our SW and W counties as rich tropical moisture advances ahead of Helene. The highest coverage remains W of our area, but have 30-40% PoPs W of I-95, with 10-20% PoPs further E. Helene will make landfall in the FL Big Bend region tonight, moving inland along the southern spine of the Appalachians Friday morning. The remnant sfc circulation will then interact with the upper low over the MS Valley, eventually pivoting NW into the OH Valley. Isolated-scattered showers or light rain are expected through around sunrise, with the bulk of the rain forecast to hold off until the late morning and afternoon hours Friday. Rain chances ramp up quickly heading into this timeframe and PoPs of 70-90% have been continued areawide. Per the latest consensus across the CAMs, the bulk of the precip will be associated with a northward/northeastward pivoting band of heavier showers and embedded thunderstorms along a warm front-type feature. Given the tropical moisture source, PWATs of at least 2-2.2" will overspread the region and very heavy rain can be expected in any shower or storm. The duration of heavy rain is expected to remain on the shorter side, so aerial rain totals will range from 0.25-1.0" across the area (highest across the Piedmont). However, the very heavy rain rates could quickly drop an inch or two of rain in localized areas. There could be isolated instances of flash flooding in urban areas, but the overall flooding risk remains marginal per the latest WPC excessive rainfall outlook. The other side to the forecast, and perhaps the more concerning aspect, is the tornado potential. With sfc dew points surging into the mid 70s and temps in the upper 70s or lower 80s, there could be a narrow axis of higher sfc-based instability along and just ahead of the line of showers/storms. Forecast sounding show large, looping hodographs with plentiful 0-1 and 0-3 km SRH. If enough instability can be realized, a tornado threat could materialize. The highest threat is over central and southern VA and NE NC, where SPC has expanded the slight risk. A marginal risk borders the slight risk to the N and it is questionable how much destabilization there will be in these areas. The lowest tornado threat appears to be on the Eastern Shore. With strong winds aloft (850 and 925 mb winds of ~60 and ~40 kt, respectively), any convective core could also mix down some of these winds to the sfc, especially if low-level lapse rates can be sufficiently steepened in areas that see sfc heating and/or cloud breaks. Highs Friday range from the lower 80s across the E and S, with mid-upper 70s across the W and N. Skies average mostly cloudy to overcast. Lows Friday night in the mid-upper 60s, with slowly clearing skies and PoPs tapering off (though a few showers may remain). && .SHORT TERM /SATURDAY THROUGH SUNDAY/... As of 355 PM EDT Thursday... Key Messages: - Mainly rain-free and warm/humid Saturday. - Cloudier and slightly cooler Sunday, with chances for a few showers returning. On Saturday, the remnants of (weakening) Helene will be located well off to our west over western KY and the remnant sfc circulation will slowly fill in underneath the upper low. Drier weather returns outside of some low- end rain chances across the NW late. High temps warm into the low-mid 80s under a mostly sunny sky. Lows Sat night in the mid 60s. Conditions turn more unsettled more Sunday as the upper low/trough over the OH Valley translates eastward. Therefore, expecting more in the way of cloudiness and chances for showers (especially NW). Some uncertainty surrounds rainfall coverage, with the 12z GFS showing more precip than the ECMWF. The GFS solution would lead to cooler high temps vs. the ECMWF. For now, will go with NBM highs, which is a few degrees cooler than Saturday and in the upper 70s-low 80s (mid 80s possible far SE). Lows Sun night in the 60s. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 330 PM EDT Thursday... Key Messages: - Multiple low-end chances of rain Sunday through Tuesday early from the post tropical remnant of Hurricane Helene. - Drier and cooler air arrives mid to late next week. The latest model guidance indicates the remnant low of Hurricane Helene will gradually shift to the east through Tue after stalling near the TN valley on Sunday. This will keep conditions unsettled, with chcs for showers and a few tstms. High temperatures Mon-Wed will be in the mid-to-upper 70s with lows in the low 60s Mon-Tue night. A dry cold front is expected around Tuesday night. There is some model differences on the timing, but cooler overnight lows in the low-to-mid 50s across the piedmont and inland and upper 50s near the coast for Wed-Thur night are possible. After the cold front, significantly lower humidities are expected. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... As of 230 PM EDT Thursday... Scattered showers remain to the NW of RIC. High clouds from Hurricane Helene with VFR conditions are present across the area. Some lower clouds (around 2,000ft) are present across most of the area, but they are mainly scattered. Winds are primarily SE at 5- 10kt. MVFR CIGs will begin overnight with the piedmont reaching lower heights first. Patchy fog near SBY and PHF is possible before sunrise. Cloud heights will decrease throughout the day to IFR and locally LIFR as rain chcs increase. There is a chc for scattered storms/tstms starting tomorrow afternoon but timing and coverage are uncertain. Locally reduced visibility and higher winds are expected in any shower or storm. After sunrise, winds will pick up and gusts around 20kt are possible across the area. Outlook: The direct impacts of Hurricane Helene and its remnant low are somewhat uncertain, but Friday afternoon and into overnight has a continuing chc of storms. While Friday is likely wet, Saturday will be drier. A chc of showers is possible with unsettled wx Sun- Mon. && .MARINE... As of 400 PM EDT Thursday... - Small Craft Advisories have been extended across all waters for Friday for increasing southeast winds. - Southeast winds increase on Friday bringing Small Craft conditions in the Chesapeake Bay, Rivers and Currituck Sound. East to Southeast flow persists this afternoon with winds generally 10 kt. Southeast winds will gradually increase after midnight and continue to increase through Friday morning as Helene pushes north. Major Hurricane Helene continues to intensify and accelerate northward and is forecast to make landfall along the Florida Big Bend later tonight. Helene will continue to move quickly north into Georgia early Friday then into Tennessee later Friday. Winds increase to 15-20 kt with gusts to 25 to 30 kt Friday into Friday evening and SCA headlines have been hoisted for all waters. The gradient relaxes early Saturday as the remnant circulation from Helene gets shunted NW on the northern periphery of an upper level low over Tennessee. Waves in the bay increase quickly to 2-3 ft Friday with 3-4 ft in afternoon. Calmer conditions are expected on Saturday and even into early Sunday. Seas will likely remain elevated though so SCAs may linger into Sat and Sun for the ocean waters. A secondary low may develop along the coast late Sunday into Monday bringing a potential return on SCA conditions to the Bay early next week. High rip current risk continues for all beaches today and Friday given 3-5 ft nearshore waves and swell periods 10-12 seconds. && .TIDES/COASTAL FLOODING... As of 4 PM EDT Thursday... Key Messages: -Tidal departures continue to fall across the region. - Coastal flooding persists at Bishops Head and Tangier and will continue for the next several high tides. - Back Bay of VA Beach will likely go into minor flooding Friday as southeast winds increase. Tidal departures continue to fall this afternoon, but remain highest (1.5-1.75 ft) in the upper Chesapeake Bay from Tangier to Bishops Head. Water levels will fall further at most locations over the next 24 to 48 hours. Lastly, will continue to watch areas adjacent to the Currituck Sound (including Back Bay of VA Beach) and the Albemarle Sound through Friday as SE winds could push already elevated water levels up further into minor flooding thresholds. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...Coastal Flood Advisory until 8 AM EDT Saturday for MDZ021-022. NC...None. VA...None. MARINE...Small Craft Advisory from 7 AM Friday to midnight EDT Friday night for ANZ630>638. Small Craft Advisory until 1 AM EDT Saturday for ANZ650-652- 654-656-658. && $$ SYNOPSIS...LKB/SW NEAR TERM...SW SHORT TERM...LKB/SW LONG TERM...KMC AVIATION...KMC/LKB MARINE...RHR/JAO TIDES/COASTAL FLOODING...