Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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496 FXUS61 KCLE 170223 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 1023 PM EDT Tue Jul 16 2024 .SYNOPSIS... A ridge exits southeastward from our region as a weak cold front drifts southeastward across northern Ohio and northwest Pennsylvania this evening through late Wednesday morning. Behind the front, another ridge builds slowly from the north-central United States and vicinity through the end of this week. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... Coverage of showers has been pretty limited this evening but would expect to see some expansion as the front crosses Lake Erie. Will continue with slight chance/chance pops overnight with some low level moisture advection feeding in ahead of the front. Coverage of thunderstorms is expected to remain limited. Previous discussion... Cyclonic W`erly flow aloft and embedded shortwave disturbances affect our CWA through Wednesday night as a mid/upper-level low wobbles southeastward from northern ON to southwestern QC. At the surface, a ridge exits SE`ward as a weak cold front drifts SE`ward through our region from around sunset this evening through late Wednesday morning. Behind the front, another ridge builds slowly from the north-central United States and vicinity through Wednesday night. However, subtle trough axes associated with the aforementioned shortwave disturbances will also traverse our region generally from northwest to southeast on Wednesday. Overnight lows tonight are expected to reach the mid 60`s to lower 70`s around daybreak Wednesday morning. Late afternoon highs are forecast to reach the upper 70`s to lower 80`s on Wednesday as intervals of sunshine and daytime heating are partially-offset by net low-level CAA behind the weak cold front. Overnight lows are expected to reach the upper 50`s to mid 60`s around daybreak Thursday morning as a cooler/drier air mass associated with the aforementioned surface ridge continues to overspread our region. Primarily fair weather is expected. However, isolated showers and thunderstorms are possible through this early evening, roughly south of U.S. Route 30. This is where CAM`s continue to suggest residual differential heating-related mesoscale fronts may act as a focus for convection initiation amidst weak to moderate boundary layer CAPE, moderate DCAPE around 500 to 900 J/kg, steep low-level lapse rates, and moderate effective bulk shear. If storms develop in this area, they may produce a few damaging convective gusts. Additional isolated showers and thunderstorms are possible along/just ahead of the cold front this evening through late Wednesday morning as the front encounters a warm/moist sector comprised of weak to moderate boundary layer CAPE and moderate effective bulk shear. Severe thunderstorms are unlikely to accompany the front given continued weak mid-level lapse rates and weakening DCAPE/low- level lapse rates via nocturnal cooling. Behind the cold front, isolated showers/thunderstorms remain possible through the early evening hours of Wednesday as the aforementioned surface trough axes encounter moderate effective bulk shear and a "cool sector" boundary layer comprised of surface dew points mainly in the 60`s and weak to moderate CAPE. However, model soundings suggest that low-level CAA partially offsetting daytime heating and abundant cloud cover will limit the magnitude of DCAPE/low- level lapse rates as mid-level lapse rates remain poor. As a result, severe thunderstorms are not a concern on Wednesday, but trends in forecast model data will continue to be monitored. Fair weather is expected CWA-wide later Wednesday evening through daybreak Thursday due, in part to a lowering/stabilizing subsidence inversion accompanying the surface ridge. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... The pattern change will be fully in place by Thursday signaling the beginning of a period of spectacular weather that will last through the weekend. A deep mid/upper trough axis across the central Great Lakes and Ohio Valley will gradually shift east Thursday night and Friday, however, broad longwave mid/upper troughing and associated NW flow will persist across the Great Lakes and Northeast US into the weekend downstream of a strengthening mid/upper ridge (heat dome) over the Intermountain West. This mid/upper level pattern will allow strong surface Canadian high pressure to drift from the Upper Midwest Thursday to over the central Great Lakes and Ohio Valley by Friday night. Lake-effect clouds will linger from north central Ohio into NW PA Thursday morning, but increasing amounts of dry air and subsidence will lead to mostly sunny skies by afternoon, with mostly clear conditions then lingering through Friday night. The NW flow aloft and Canadian high pressure will bring below normal temperatures for a change with highs in the low/mid 70s Thursday and mid 70s to near 80 Friday. Lows Thursday night and Friday night will be impressively cool due to the clear skies and light winds promoting radiational cooling. Expect lows in the mid/upper 50s both nights, with some low 50s in sheltered valleys of interior NE Ohio and NW PA and along the US 30 corridor. && .LONG TERM /SATURDAY THROUGH TUESDAY/... The relatively cool pattern will continue this weekend, but gradual warming with an increase in humidity is expected early next week as the surface high drifts into the eastern Great Lakes Saturday and Sunday and eventually offshore of the East Coast by Tuesday. This is in response to rising heights across the Appalachians and Ohio Valley as the Bermuda High strengthens off the SE coast ahead of a shortwave gradually progressing out of the Plains early next week. Deterministic and ensemble guidance are struggling to time this shortwave as it may evolve into a closed low over the midsection of the country, and that affects how soon a warm front and associated warm air advection may set up across our region. The trends have been slower, so kept dry conditions through Sunday with increasing clouds, with slight chance PoPs for isolated showers and thunderstorms reaching the US 30 corridor Monday. The better surge of moisture and greater chances for diurnal showers/storms will probably be delayed until Tuesday. Highs will warm into the low 80s Saturday and low to mid 80s Sunday, but humidity levels will remain comfortable with dew points in the 50s. Highs in the low to mid 80s are expected Monday and Tuesday with a noticeable increase in humidity as dew points rise into the 60s. && .AVIATION /00Z Wednesday THROUGH Sunday/... Scattered showers have developed just south of a line from FDY to MFD this evening with some low level moisture advection ahead of a cold front that will settle south across the area overnight. Any thunderstorm this evening will have brief heavy rainfall if they hit a terminal with brief IFR possible, but coverage of thunderstorms is expected to be low. We do expect scattered showers to also accompany this cold front but confidence in which terminals may be impacted is low so backed off from prevailing showers in most cases to tempo for light rain showers. An expansion of cloud cover is also likely ahead of the front and may be MVFR for inland locations. It is not out of the question that a few pockets of IFR are also possible between 09-12Z, mainly at MFD or CAK. The front is generally slow to cross the area with a wind shift to the northwest reaching northern terminals between 7-10Z, and inland terminals between 12-14Z. Ceilings will improve to VFR by midday and then scatter out late, except TOL/MFD which will scatter out during the morning. Outlook...Non-VFR possible with isolated showers/thunderstorms Wednesday afternoon through evening. && .MARINE... The winds and waves have diminished on Lake Erie as the MCV has moved well to the east, so allowed the headlines to expire at 20Z. This will leave SW winds of 10-15 knots in place tonight, shifting to N by Wednesday morning while diminishing to 5-10 knots through the day as a cold front pushes south of the lake. N winds will continue Wednesday night and Thursday with an increase to 10-15 knots Thursday before diminishing to 5-10 knots again Thursday night and Friday. Winds will generally turn light and variable on the lake this weekend. Overall, very quiet marine conditions are expected, however, there will be a near 14 C lake to 850 mb temp differential Thursday morning, so cannot rule out an isolated waterspout or two. The boundary layer dries quickly, and short fetch N flow is expected, so will leave this out of the HWO for now, but it`s something to further investigate. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Jaszka NEAR TERM...KEC/Jaszka SHORT TERM...Garuckas LONG TERM...Garuckas AVIATION...KEC MARINE...Garuckas