Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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314 FXUS61 KCLE 141102 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 702 AM EDT Sun Jul 14 2024 .SYNOPSIS... High pressure exits to the southeast today as a frontal boundary sets up across the Great Lakes. This front will push southeast across the area as a cold front Tuesday night. High pressure will build in Wednesday through Saturday. && .NEAR TERM /THROUGH MONDAY/... A pair of MCSs are ongoing to our west/northwest at 7 AM, one approaching I-75 (that is rapidly decaying) and another over WI, with the WI MCS tied to a convectively-enhanced shortwave. How these MCSs evolve will heavily dictate our weather today. It is unclear how far rain with this lead MCS will survive into our area as it is moving into a dry and stable environment, though do at the least expect some lighter showers into northwest OH this morning. By this afternoon, locations west of approximately I-77 that do not get clouds/rain from this morning`s decaying MCS will begin destabilizing enough that a combination of any boundaries left by the MCS and forcing from the convectively-enhanced shortwave dropping out of the upper Midwest may spark renewed convective development. This activity would continue east-southeast through early evening. Isolated strong winds can`t be ruled out mainly west of I-77 if we do see thunderstorm development this afternoon, though generally modest thermodynamics and shear will make it difficult to see any sort of organized severe threat during the day today. Ultimately, have chance (40-50%) POPs spreading into the I-75 corridor this morning dropping off to 30-40% farther east/southeast. Ramp things back up to 50-60% in some of our southern counties from Marion-Mansfield over towards Akron/ Canton for a few hours this afternoon, where potential for renewed development seems highest. We will likely see a relative lull in shower/storm potential later this afternoon into this evening. Lowered high temperatures a bit for today, especially across northwest Ohio. Still have most of the area reaching the upper 80s to near 90 with peak heat index values generally in the low to mid 90s. We should start this evening relatively quiet. A bowing MCS is blasting across SD early this morning and is associated with the next shortwave that will push across the southern Great Lakes tonight. While any convective development this afternoon will have ripple effects on the environment and placement of boundaries into tonight, leading to uncertainty, there is a decent likelihood that this next shortwave will spark convection to our west/northwest by this evening that congeals into an MCS that spreads east-southeast towards our area late this evening into the overnight. Placement and intensity of this activity tonight is quite uncertain due to the aforementioned sources of uncertainty. However, we will be on the edge of a very unstable airmass tonight and a strong MCS can locally enhance the shear. Concern for severe weather, mainly in the form of damaging winds, is higher tonight than during the day today. Given the uncertainty the current SPC outlook maintains a Marginal Risk (risk level 1/5) though do see potential for that to trend up in future updates, particularly across parts of northwestern Ohio. Expect muggy lows tonight ranging from the upper 60s in northwest PA to the low to mid 70s in Ohio. Showers/thunder may still be ongoing to start Monday, particularly from eastern OH into PA. Subsidence and a worked over atmosphere behind any MCS would likely lend to a period of drier weather for a number of hours on Monday once any morning activity exits, potentially through most of the afternoon. Trended POPs down for several hours late Monday morning through most of the afternoon. The airmass should recover by later Monday afternoon or evening from the west and southwest, aided by increasing wind fields and warm air advection ahead of the next shortwave approaching out of the upper Midwest. The combination of dew points warming into the 70s, steep mid-level lapse rates of 6.5-7.5C/km, and hot temperatures should yield very strong (2000-3000+ J/KG of MLCAPE) with large values of DCAPE just to our west by Monday afternoon and evening. Lift associated with the aforementioned shortwave will likely spark additional convection to our west-northwest Monday afternoon that spreads towards the upper Ohio Valley late Monday into Monday night with severe weather potential. Begin ramping POPs up in our western counties early Monday evening, though the greatest likelihood for activity will probably come in the Monday night timeframe. Due to potential for an extensively worked-over airmass and lingering clouds behind any MCS earlier Monday, lowered high temperatures and dew points a bit for Monday. Still have highs ranging from the mid 80s in northwest PA to the lower 90s in our western counties. Peak forecast heat index values range from the mid 90s to near 100 west of I-77 (greatest potential for near 100 from Toledo to Marion points southwest) to the upper 80s/lower 90s in extreme northeast OH and northwest PA. A Heat Advisory may be needed for western portions of the area on Monday but confidence is low. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... Won`t restate a lot of the details from the near term discussion, but the general large-scale pattern and environment remains unchanged into Monday night (northwest flow aloft, lots of instability, marginal deep-layer shear). The evolution (timing and areal coverage) of a potential MCS moving east-southeast across the area Monday night is quite uncertain and is largely dependent on what happens with convection Sunday through Monday. Currently, most model guidance has a convectively-enhanced shortwave trough moving across the area with an MCS some time Monday night. If an MCS does move through, the environment would support a marginal severe weather threat, despite the unfavorable diurnal timing. Strong to damaging winds would be the primary weather hazard. By Tuesday, a large upper-level trough digs down into the Great Lakes region with a surface cold front sagging down just north of the forecast area (from southern Ontario southwest across lower Michigan, northern Indiana, etc). A very moist airmass (dew points in the low 70s) will contribute to moderate to high instability across the forecast area by Tuesday afternoon with model guidance generally forecast MUCAPE exceeding 2000 J/kg (but possibly as high as 4000 J/kg). Synoptic-scale forcing from the approaching upper- level trough and surface cold front will likely lead to convective development sometime Tuesday afternoon through late Tuesday night. Deep-layer shear is expected to be somewhat marginal (20-30 kts) but sufficient for organized severe convection. Damaging winds is once again likely to be the primary weather hazard. The approaching front might stall or slow down a bit as the opposing low-level jet strengthens Tuesday evening. Continued synoptic-scale forcing and cloud-layer winds parallel to the front could lead to backbuilding and training of thunderstorms. Combined with very high PWAT (ensemble mean of 1.9 inches, which is very high for an ensemble mean), flash flooding is going to be possible Tuesday afternoon through Tuesday night. This is supported by the continuation of the slight risk ERO centered on our forecast area. Added heavy rain to the forecast to account for this threat. Eventually, the front makes southward progress, clearing the forecast area by Wednesday afternoon. Until thing, lingering isolated thunderstorms could be possible Wednesday morning to early Wednesday afternoon, mainly for the southern portion of our forecast area. Heat indices on Tuesday are expected to be in the mid to upper 90s before thunderstorms develop. Post-frontal, cooler temperatures are expected on Saturday, with highs down into the low 80s. && .LONG TERM /THURSDAY THROUGH SATURDAY/... High pressure builds in behind the departing cold front, ushering in a cooler, dryer airmass. Temperatures likely to remain in the 70s on Thursday before a gradual rebound to the low to mid 80s on Friday and Saturday. No precipitation expected in the long term period. && .AVIATION /12Z Sunday THROUGH Thursday/... Limited patchy fog will quickly lift through 13z. Otherwise mainly VFR through this evening with the main concern being timing and intensity of showers/storms. A weakening cluster of rain (no lightning) is approaching TOL and FDY and may bring some showers with few or no restrictions this morning. Some isolated to scattered showers and thunder may re-develop farther east/southeast this afternoon, especially in the vicinity of MFD, CAK, and perhaps FDY, YNG, and CLE. Confidence in how much thunder this activity has is low and coverage will likely be isolated to scattered, meaning odds of hitting a given terminal are low. Given all of this, handled with VCSH mentions, though it is possible AMDs or the next full cycle needs to hit this afternoon`s convection a bit harder at a couple of TAF sites. Generally then expect a lull in activity into this evening before another potential cluster of showers and storms spreads in from the west later this evening. Have broad windows for showers with vicinity thunder and MVFR vsby late this evening into the overnight at all sites except for ERI. Future cycles will almost certainly need to refine the timing and potential restrictions with this activity. Light southerly winds turn more south-southwest at 6 to 12 knots with a few 15-20 knot gusts this afternoon. Winds remain generally south- southwest but subside to 4 to 8 knots outside of any thunderstorms tonight. Outlook...Mainly VFR outside of occasional thunderstorms tonight through Tuesday evening. && .MARINE... Southwest winds will be on the increase today, generally in the 10- 15 knot range through at least Tuesday night. There could be brief periods of stronger southwest winds to 20 knots. Latest model guidance suggests the best chance of this occurring would be Monday night into Tuesday, though there is very low confidence in this right now, and would likely depend on the evolution of thunderstorms over the next couple days. A cold front moves south across Lake Erie late Tuesday night into Wednesday morning with winds becoming north to northwest Wednesday through Friday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Sullivan NEAR TERM...Sullivan SHORT TERM...Saunders LONG TERM...Saunders AVIATION...Sullivan MARINE...Saunders