850 FXUS61 KCLE 180808 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 408 AM EDT Thu Jul 18 2019 .SYNOPSIS... High pressure will ridge northward from the southeastern United States today then remain nearly stationary through Saturday. A cold front will slide southeast across the region Saturday night with a reinforcing surge of cooler air arriving Sunday night. High pressure will build south toward the area early next week. && .NEAR TERM /THROUGH FRIDAY/... Increasing heat remains the main story for this forecast. All locations will warm today with NW Ohio being the hottest. Western areas will only hit heat advisory levels (Heat indices 100-104) today but the cumulative impacts of the heat will begin this afternoon and continue into Saturday. The elevated afternoon heat indices will reach into the heat warning criteria (greater than 105) on Friday and Saturday with a few locations seeing 110 or higher for a few hours across the west. So these high heat indices combined with lows above 75 degrees will cause a cumulative impact on the region through Saturday. This is the reason we hoisted the warning for NW Ohio starting today. It will be very warm to hot elsewhere today but the extreme heat likely wont arrive until Friday into Saturday. So we will continue with the excessive heat watch for now. There is some uncertainty about the highest heat index values across the region with convective debris cloudiness moving over the region from the west. There are also some low chances that some thunder could move into NW Ohio or maybe even across Lake Erie into NW PA early Friday morning. Outflow from this convection combined with a lake boundary that will be along the lakeshore from Lake County to Erie County, PA may generate enough low level convergence to produce isolated/scattered thunderstorms. Did not go widespread with the thunderstorm chances since 5H heights are at least 591 dm across the region. This typically greatly reduces the convective coverage and may be enough to keep it from developing. If thunderstorms can develop they will have the potential to produce strong winds and maybe some small hail, especially on Friday across NW PA. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... The upper level ridge and heat wave will be in full force going into Saturday. The center of the heat wave will be over the Ohio River Valley region. Overnight low temperatures Friday night into Saturday morning will be near record high minimums for the date. Some locations will remain in the upper 70s to near 80 for overnight low temperatures, especially around urban areas. A frontal boundary will start drifting southward across the Upper Great Lakes region on Saturday. We may see a few more clouds and a slight chance for a shower or storm along our northern areas. But only a lucky few may see a cooling spot rain shower. The main story will still be the dangerous heat wave Saturday. Afternoon temperatures will top out in the middle 90s again with heat indices between 100 to 110. The ridge starts to break down Saturday night into Sunday. We will see that frontal boundary make progress moving southward. Widespread showers and storms are likely Sunday into Sunday night. Temperatures will still be warm ahead of the front but more typical warmth. We will have to keep an eye out for a few stronger to severe storms possible Sunday afternoon and evening. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... A big weather pattern change is heading our way for the early and middle of next week. A big amplified weather pattern sets up with a large ridge in the western U.S. and a deep trough develops over the Great Lakes region. We will see a refreshing northerly flow with cooler and drier weather coming down from Canada. Some clouds and a few showers may still be around early on Monday before the drier airmass moves in. We will see dewpoints drop into the lower 50s and be very comfortable. Overnight low temperatures will be in the 50s to around 60. Afternoon high temperatures will be in the middle 70s to lower 80s. We will be able to give the A.C. a break and open the windows! && .AVIATION /06Z Thursday THROUGH Monday/... Areas of fog will be a minor impact until just after sunrise. Most of the issues will be for KCAK and KYNG, but MVFR fog will be possible elsewhere. Some lower clouds were also moving into the vicinity of KERI with a brief period if IFR ceilings likely. Otherwise it appears there will be periods of convective debris cloudiness from the west with some afternoon cumulus mixed in with it. Winds will be rather light today. Lake breeze will likely impact KERI and may attempt to reach KCLE. OUTLOOK...Non-VFR possible in showers and thunderstorms Saturday night into Monday. && .MARINE... Weak high pressure over the lake this morning is giving us light and variable winds. Southerly winds 5 to 10 knots will return later today and tonight. Southwesterly winds 10 to 20 knots will be over the lake on Friday and we may get close to a Small Craft Advisory due to wind speeds. Southwesterly winds 10 to 15 knots will continue into Saturday ahead of an advancing cold front. Winds on Sunday may be somewhat erratic and changing with a frontal boundary slowly moving across the lake as well as interacting surface boundaries from convection. A stronger high pressure system moves in for Monday through early next week with a northerly flow over the lake 10 to 20 knots. We may see a day or two early next week with Small Craft Advisory conditions with higher wind speeds and higher waves near the north facing lakeshore. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Excessive Heat Watch from Friday afternoon through Saturday evening for OHZ009>011-019>023-029>033-038-047. Excessive Heat Warning from noon today to 8 PM EDT Saturday for OHZ003-006>008-017-018-027-028-036-037. PA...None. MARINE...None. && $$ SYNOPSIS...MM NEAR TERM...MM SHORT TERM...Griffin LONG TERM...Griffin AVIATION...MM MARINE...Griffin