Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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033 FXUS61 KCLE 270012 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 812 PM EDT Thu Sep 26 2024 .SYNOPSIS... After Hurricane Helene makes landfall along the northeastern Gulf Coast tonight it will lift into the Ohio Valley by Friday night while rapidly weakening. Weak low pressure associated with the remnants of Helene will then drift across the Ohio Valley through the weekend before dissipating early next week. && .NEAR TERM /THROUGH FRIDAY NIGHT/... The forecast for tonight remains on track with overcast skies and mild temperatures. No significant changes made at this time. Previous discussion...An active near term forecast period is in store as the interaction between Hurricane Helene and a non- tropical closed low over the mid- Mississippi/lower-Ohio Valleys brings clouds, some rain, and very stiff east-northeast breezes to the local area. While the weather will be active / unsettled it will also be relatively low-impact from a hazards perspective. Mainly dry weather is expected through tonight as a small ridge axis aloft briefly builds between the aforementioned closed low to our southwest and a longwave trough to our northeast. Some weak mid-level isentropic lift and moisture advection will continue into our far southern counties tonight, but the lift is overall quite weak so just carry 20% POPs and no or very minimal QPF from approximately Findlay to Millersburg points south/west. Farther north it will be mainly cloudy but should be rain-free outside of perhaps a spotty sprinkle. Low temperatures tonight will be unseasonably mild, generally in the low to mid 60s but with a few 50s possible in interior Northwest PA. It will remain overcast on Friday as Helene becomes entangled with the closed low to our southwest and accelerates towards the Ohio Valley. Helene will quickly be weakening and undergoing extra- tropical transition through Friday. Despite this weakening trend, a surge of stronger moisture advection and tightening pressure gradient will bring light rain and increased winds and gusts to the area. Rain chances will begin quickly increasing from south to north- northwest after midday Friday, with the most widespread rain expected during the late afternoon and evening hours. A mid-level dry slot will begin wrapping in from the south-southeast Friday night, allowing rain to become much spottier/lighter from the south- southeast overnight. Have categorical POPs (80-90%) across most of Northwest and Central OH, dropping off to high-chance to likely (50-70%) elsewhere. This is a slight increase from the prior forecast. Essentially all guidance has most or all of the area seeing a bit of rain, though with light amounts (<0.25") given the ridge axis aloft persisting ahead of Helene`s remnants and causing the rain to begin weakening as it spreads in. A strong low-level jet and tight pressure gradient will lead to gusty winds across the area, mainly Friday afternoon and evening. Most models have the tightest gradient and 40-45 knots of 925mb flow across much of Northwest Ohio, along with across our far southern counties (i.e. Marion to Knox). In this area, a period of 35-40 MPH gusts is feasible, with 25-35 MPH peak gusts elsewhere. While the NBM and HREF actually depict a 30-50% chance of exceeding advisory- criteria (46 MPH) gusts across this part of our area, widespread clouds and incoming rain during the period of strongest winds should limit mixing heights significantly. It also helps that the system will be quickly weakening as we see our strongest winds. Did add a Hazardous Wx Outlook mention for wind gusts up to 40 MPH in some of our western/southwestern counties, but ultimately don`t expect us to need any wind headlines barring notable changes to the big picture. It will remain mild on Friday with highs in the mid to upper 70s ahead of the rain. Lows Friday night will remain in the 60s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... The remnant of tropical cyclone Helene will meander over the Lower Ohio Valley this weekend. The center or the low pressure system will slowly track eastward across the Ohio Valley into the Mid-Atlantic region through Sunday night. Scattered showers will be likely for much of the weekend with the greatest rain chances Saturday afternoon through Sunday afternoon. There could be an isolated thunderstorm or two but mostly rain showers are expected. Average QPF this weekend will be between a quarter and a half an inch of rainfall. The heaviest rainfall with this system will stay south of our local area. Afternoon high temperatures will be in the 70s this weekend. && .LONG TERM /MONDAY THROUGH THURSDAY/... There will be lingering rain chances into Monday associated with the remnants of Helene. The higher POPs will be over the eastern CWA. A quick moving cold front will push through the region on Tuesday with additional chances for showers. Temperatures for early next week and ahead of the cold front will be in the 70s for afternoon highs. Cooler weather will follow behind the cold front by the middle of next week with highs in the 60s. && .AVIATION /00Z Friday THROUGH Tuesday/... Overcast skies are in place tonight with a few pockets of MVFR at 00Z. Generally expecting some improvement with VFR conditions for most of the night with ceilings lowering to MVFR on Friday. This is likely to occur in the morning in the western and southern terminals and later in the day at CLE and possibly not at all at ERI. Increasing northeast winds during the day on Friday will be the main concern as the remnants of Helene make their way into the lower Ohio Valley. Winds are likely to increase to 15-20 knots with gusts of 30 knots or higher. The strongest winds are likely at TOL off Lake Erie and possibly FDY or MFD where gusts may reach 35 knots. Otherwise, rain will spread north into the area generally between 16-22Z and restrictions to visibility developing. Outlook...Periods of non-VFR are possible with scattered rain showers and low ceilings Friday night through Monday. && .MARINE... Winds will be from the northeast 10 to 15 knots this afternoon and evening. The low level flow and surface winds will increase over Lake Erie as Tropical cyclone Helene moves inland along the Gulf Coast late tonight and move quickly into the southern Appalachians on Friday. Winds will increase 15 to 20 knots late tonight and peaking at 25 to 30 knots with gusts to up to 35 knots by Friday afternoon and evening. The highest winds and waves will be in the western and central basins of the lake Friday and Friday night. This strong northeasterly flow may increase water levels Friday evening through Saturday morning. Northeast winds diminish to 10 to 20 knots Saturday and 10 to 15 knots on Sunday. Small Craft Advisories will be issued for Friday morning through Saturday morning. The SCA may need to be locally extended for portions of the western basin of Lake Erie Saturday into Sunday. Winds will become from the southeast 5 to 10 knots by Monday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Beach Hazards Statement from 5 AM EDT Friday through Saturday morning for OHZ003-007-009>011. Beach Hazards Statement from Friday morning through Saturday morning for OHZ012-089. PA...Beach Hazards Statement from Friday morning through Saturday morning for PAZ001. MARINE...Small Craft Advisory from 5 AM Friday to 8 AM EDT Saturday for LEZ142>146. Small Craft Advisory from 8 AM Friday to 8 AM EDT Saturday for LEZ147>149. && $$ SYNOPSIS...Sullivan NEAR TERM...KEC/Sullivan SHORT TERM...Griffin LONG TERM...Griffin AVIATION...KEC MARINE...Griffin