532 FXUS61 KCLE 122300 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 700 PM EDT Mon Apr 12 2021 .SYNOPSIS... Low pressure centered over western Pennsylvania will move southeast off the Mid Atlantic coast tonight. High pressure will briefly build across the region late tonight through Tuesday night. Another slow moving low pressure system will move southeast into the Great Lakes late Wednesday and will linger over the region through Thursday. && .NEAR TERM /THROUGH TUESDAY NIGHT/... Scattered rain showers continue through the forecast area early this evening on the back side of the upper low complex. Some more perky showers are found in eastern Ohio into NW PA and will maintain a slight chance thunder mention while some localized instability exists over the next hour or two. Showers will taper as the low departs the region and will maintain a slight chance PoP for later tonight. Will leave in some patchy fog mentions across the area, although this may need to be evaluated for expansion in later forecasts. Previous Discussion... Vertically stacked low now over western PA this afternoon will continue to slide southeast through the evening, with showers across the southeast part of the forecast area gradually moving out of the region. Left slight chance thunder in the grids, although very little lightning activity has been observed and radar trends not too favorable for thunder. Pops will generally diminish for the area through the remainder of the evening, although have some slight chance pops redeveloping eastward across the area, associated with some weak low level frontogenesis and very weak elevated instability. Lows tonight will drop into the low to mid 40s across the area. The rest of the near term looks quiet for the area as high pressure briefly returns to the region late tonight through Tuesday night. Ample sun and WAA should allow for temps to recover back into the mid to upper 60s for much of the area on Tuesday. Dry conditions persist through Tuesday night, with low pressure moving just south of the Ohio valley, but precip associated with this system should remain well south of the area. Lows Tuesday night will be in the low to mid 40s across the area. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... A shortwave ridge will move east out of the area on Wednesday, ahead of a closed upper level low that is expected to move southeast across the Great Lakes region through the short term forecast period. The departing ridge will allow for mostly dry conditions to linger into Wednesday afternoon, before a surface low from the Midwest merges with a low pressure tracking up the East Coast on Wednesday. This merge will result in a broad surface low pressure with an associated cut off low. An increase in moisture across the area and associated upper level support will allow for scattered showers to develop across the area. Overnight on Thursday, winds will shift to become northwesterly, increasing CAA across the area. Models continue to bring 850mb temperatures of -4 to -6 across Lake Erie which, coupled with the warming lake temperatures, may result in lake enhanced showers particularly across NE OH and NW PA. Most showers will be primarily rain, however areas of higher elevation may experience a flurry or two mixing in. No widespread snowfall or snow accumulation is expected. These showers will diminish overnight on Thursday as the aforementioned low pressure continues to move further east and temperatures at 850 mb begin to increase. High temperatures on Wednesday will be in the mid to upper 50s with slightly cooler temperatures on Thursday only reaching into the mid 50s. Overnight lows are expected to be in the upper 30s. && .LONG TERM /FRIDAY THROUGH MONDAY/... A weak high pressure and associated upper level ridge will build over the area on Friday. Relatively drier air will allow for a break in precipitation on Friday. With lower moisture, overnight lows on Friday may be forecast a bit high with this update, but it will depend on where any moisture lingers and if strong radiational cooling will be able to be established. For the weekend, the Canadian and ECMWF continue to suggest a shortwave ridge building over the area, allowing much of Saturday to remain dry ahead of another low pressure system. The GFS has persistently kept a broad trough across the area with higher moisture values lingering for the start of the weekend. If the GFS pans out, most precipitation should remain to the south of the area. On Sunday, another shortwave trough ahead of the digging trough out west will allow for scattered showers. Exact timing and location of these showers remains rather uncertain. Temperatures look to be a bit warmer with low 60s forecast through the weekend and overnight lows dipping into the low 40s. && .AVIATION /18Z Monday THROUGH Saturday/... An upper low over the area continues to bring widespread SHRA and MVFR/IFR conditions for the eastern terminals, with some scattered SHRA and VFR/MVFR conditions for KTOL/KFDY. Conditions will generally improve through/after 00Z at most terminals with the low moving east of the area, however some IFR stratus off Lake Erie may impact KERI after 00Z, with some MVFR/IFR BR possible at KYNG toward daybreak. Mainly VFR conditions are expected at the other terminals after 06Z. Light, generally westerly winds will persist through the period. Outlook...Non-VFR possible in rain showers Wednesday afternoon through Thursday evening. && .MARINE... A broad surface low pressure will linger over the Great Lakes Region though at least Wednesday, bringing a cold front across Lake Erie Tuesday night into Wednesday. Winds through that period are expected to be south-southwesterly at 10-15 knots. Winds will shift to northwesterly at 10-20 knots behind the cold front, resulting in waves building 1-3 feet by Friday morning. On Friday, a shortwave ridge will move across the region, weakening the winds from the north to 5-10 knots. Generally good marine conditions will persist through Friday, with greater uncertainty in the forecast for the weekend. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Greenawalt NEAR TERM...Greenawalt/Sefcovic SHORT TERM...Campbell LONG TERM...Campbell AVIATION...Greenawalt MARINE...Campbell