FXUS61 KCLE 130531 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 131 AM EDT Mon May 13 2024 .SYNOPSIS... High pressure over the Ohio Valley this evening will exit offshore of the Mid Atlantic coast tonight allowing a weak cold front to drop to the vicinity of Lake Erie. This front will return north as a warm front Monday as low pressure moves across the Mississippi Valley. The low will then lift across the Great Lakes Monday night and Tuesday extending a cold front into the area. && .NEAR TERM /THROUGH TODAY/... No changes to the forecast at this time. Previous Discussion... Clouds that lingered much of the day over NE Ohio and NW PA have cleared nicely allowing for a fair but cool afternoon as mid/upper troughing lingers over the eastern Great Lakes. We only have to look to the west and northwest to find our next weather makers though in the form of a mid/upper shortwave trough in the Upper Midwest and a southern stream closed low over the southern High Plains. Surface high pressure currently over the Ohio Valley will quickly move offshore of the Mid Atlantic coast tonight allowing the upstream shortwave over the Upper Midwest to progress across the northern and central Great Lakes. This will push a weak cold front southward into Lake Erie late tonight before stalling in response to the southern stream closed low and associated weak surface low approaching the Mid Mississippi Valley. The cold front will be displaced well south of the synoptic forcing tonight leading to very limited convergence and moisture return, so expect any showers or rumbles of thunder to be very isolated. However, with the boundary dropping into the area, have slight chance to chance PoPs for lakeshore areas late tonight and Monday morning, mainly in the 06-12Z timeframe. The boundary will likely not make it any farther south than the south shore of Lake Erie before it retreats back north as a warm front Monday morning in response to the system over the Mid Mississippi Valley. That closed low will become more of an open shortwave trough as it lifts across Missouri and into Illinois during the day Monday. Strong warm air advection ahead of this system will lead to much warmer conditions and a sharp change to well above normal temperatures Monday. NAM and RAP forecast soundings suggest a weak cap in the 850-700 mb layer Monday afternoon, so do not expect to see much in the warm sector, and low- level moisture is also slow to return limiting MLCAPE values to a couple hundred joules. However, the 3-KM NAM hints at some convection near a lake breeze boundary in far NE Ohio and NW PA in the afternoon, so it cannot be entirely ruled out. Most areas will just be warm and dry Monday though. Precipitation chances will expand east into the area Monday night as the weak surface low associated with the shortwave rides up the boundary across northern Illinois, finally supporting stronger moisture advection and isentropic ascent into the southern Great Lakes. This will support fairly widespread showers, and there will be enough elevated instability for pockets of thunder, so have likely PoPs in most areas Monday night. Lows tonight will be milder ranging from the mid/upper 50s in NW and north central Ohio to the mid 40s to low 50s in NE Ohio and NW PA. Highs Monday will rise into the upper 70s/low 80s. Lows Monday night will only fall into the upper 50s/low 60s. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... Unsettled Tuesday in southwest flow aloft, a warm front draped lengthwise along the Lake Erie axis, and the slow moving upper trough axis just to the west of the CWA. Modest instability and shear, but a drier layer sitting above 600mb in which the limited instability could still tap into could make the convective scenario slightly tricky. Will need to see how these details unfold a little more going forward. System finally moves through late Tuesday night into early Wednesday, transitioning to northeasterly flow into the region with some lingering POPs in onshore low level moisture advection. High pressure gradually builds into the Great Lakes Wednesday night, and dries out the forecast as it does so. && .LONG TERM /THURSDAY THROUGH SUNDAY/... After brief ridging in the area Thursday, the next low pressure system moves in for the end of the week and the first part of the weekend. Significant differences exist in the evolution of this system, so the details are not there right now but will carry POPs in the extended that peak in the Friday/Friday night time frame. Should get a little warmer from the short term into the long term forecast period, and too early for now to try to dive into any sort of storm threat for the long term. && .AVIATION /06Z Monday THROUGH Friday/... VFR conditions will persist through this period with high pressure remaining in control. Currently, a low pressure system centered near Ontario/Quebec is moving an associated warm front east across the Great Lakes region which is the focus for shower development across Michigan. As this moves east, some of these showers may clip far NW PA possibly impacting KERI. However with lack of confidence in these showers maintaining themselves have opted to handle the window of possible precipitation with VCSH between 9-12Z. Throughout the day on Monday, a developing low pressure system over the Midwest will gradually push east towards the Ohio River Valley, but recent model guidance suggests this system slowing down and resulting in rainfall not expected until after this period. Southwest winds of 5-10 knots will increase this afternoon to 10-12 knots, locally up to 15 knots for western terminals. Gusts up to 20 knots are possible along and west of I71 this afternoon, but will calm as winds weaken to 5-10 knots and shift to become southerly. Outlook...Non-VFR possible in showers and thunderstorms late Monday night through Wednesday. && .MARINE... Offshore winds 10-20kts through Monday weaken to 5-15kts Monday night. Immediate nearshore waters less than a foot while the open waters will reach 1-3ft during this time frame. A low pressure system moves through Tuesday turning winds northeasterly 10-15kts, increasing to 15-20kts Wednesday. Central and western basin wave heights will be higher during this period as well where the higher winds exist, pushing 2-4ft Wednesday. Onshore winds continue through Thursday, but in lighter flows, waves subside to 1-3ft. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Garuckas NEAR TERM...Garuckas/Sefcovic SHORT TERM...26 LONG TERM...26 AVIATION...Campbell MARINE...26