textproduct: Cleveland

WHAT HAS CHANGED

Adjustments were made to temperatures, winds/gusts, rain chances and amounts over the next several days based on the latest guidance. There have been no wholesale changes to the general messaging.

KEY MESSAGES

1) Rounds of showers and thunderstorms are expected this afternoon and tonight as a cold front progresses through the region. Some thunderstorms this afternoon and evening may be severe.

2) A general 0.75 to 1.50" of rain is expected through Wednesday with locally higher amounts with any training thunderstorms. This rain may cause some flooding, mainly in typically more prone locations.

3) The next system lifts through the Great Lakes Thursday and Friday, bringing another push of warmer temperatures and periodic shower/thunder potential. Overall, this looks like a lower-impact system locally.

4) The weather pattern remains active this weekend as another low pressure lifts through the Great Lakes, dragging a stronger cold front through the local area. Warmer conditions with shower and storm chances will continue ahead of the cold front.

DISCUSSION

KEY MESSAGE #1: A combination of a low-amplitude shortwave and decaying convection may bring scattered showers/thunder across Lake Erie and portions of adjacent northern Ohio/northwestern Pennsylvania early this morning. Confidence is not extremely high given upstream radar/satellite trends overnight. After this, there should be at least a few if not several hours of completely dry, warm, and breezy/windy weather across the area ahead of the next round of convective potential tied to an approaching cold front. Highs will surge well into the mid- upper 70s today, with a few sites possibly reaching 80. Wind gusts of 30-40 MPH (strongest west of I-71) remain likely this afternoon, with a few gusts over 40 MPH possible in Northwest OH.

The main convective potential will be later this afternoon and evening. A number of models on Monday suggested that convection may develop in Northeast OH/Northwest PA in the early-mid afternoon today, potentially sparked by an outflow boundary from ongoing upstream convection. Overnight guidance has generally backed off on this scenario, though some models (especially the RRFS) still do have convection well-ahead of the front this afternoon. A flat shortwave and right-entrance quadrant of an upper-level jet streak will spread greater large scale lift in from the west late this afternoon into this evening as the front also approaches. This will yield greater convective potential spreading in from the west- northwest late this afternoon and this evening. The front pushes through tonight into early Wednesday, though it will be a rather shallow front. Isentropic lift over the shallow/sloped frontal surface should continue some rain and even thunder chances overnight tonight into Wednesday on the cold side of the front, particularly late tonight and Wednesday morning as another modest shortwave moves through and enhances the large scale lift for several hours.

Environmentally, fairly strong surface heating beneath an elevated mixed layer (EML) plume will likely yield very steep (8-9C/km) 0-3km lapse rates with moderately steep (6.5-7.5C/km) 500-700mb lapse rates aloft. However, rather modest moisture profiles will likely limit the amount of instability to 500-1000 J/KG of MLCAPE, with locally up to 1500 J/KG of sufficient low-level moisture pooling can occur ahead of the front. Deep-layer shear will increase to a respectable 40-50kt this afternoon and evening, including 30-40kt of 0-3km shear and effective storm relative helicity values in the 150-250 m2/s2 range. Given initially modest forcing and deep-layer shear vectors that cross the incoming front at a 45-60 degree angle, initial activity will likely be cellular/discrete. Gradually increasing forcing with time, along with well-mixed low-levels supporting sub-cloud evaporation and cold pool development, should allow for gradual upscale growth into small lines/clusters this evening. Initial cellular convection will likely include rotating updrafts and some supercells, capable of large hail and isolated damaging winds. As upscale growth occurs, the hail potential will decrease as wind potential increases. While the amount of shear can support both supercellular and QLCS tornadoes, high LCL heights and veered surface flow should keep the tornado risk fairly limited.

The SPC now has our entire forecast area in a Slight Risk (level 2/5) for severe weather, with damaging winds and large hail leading the way with tornadoes a lower (but non-zero) threat. The most likely window for severe is between 4 PM and 10 PM coming in from the west, though we will need to monitor for more limited activity a bit earlier across Northeast OH/Northwest PA that may bring an isolated severe risk. Nocturnal cooling and convection gradually working over the atmosphere should lead to decreasing severe potential after 10 PM, though shear remains strong overnight so any convection that can remain surface based could pose a lingering isolated threat through about midnight. The main uncertainties evolve around any afternoon convection potentially working over parts of the area and limiting the later (and likely main) convective potential. Models also offer typical uncertainty over where convection will fire closer to the cold front and then subsequently track through our area. The overall setup certainly supports severe potential later this afternoon into tonight, though with some typical caveats/uncertainty, likely meaning that parts of the area will largely skirt around trouble (as is common in most severe setups).

KEY MESSAGE #2:

Thus far, we've lucked out with heavier rain overnight ending up north of our area and saving us initial some rain/QPF. However, the combination of a slowly sagging front, deep-layer flow trending more parallel to the boundary Tuesday night into Wednesday, skinny instability profiles (especially Tuesday night and beyond), and precipitable water values climbing to around 1.25" (which is safely above the 90th percentile of climatology for this time of year) do suggest that rain amounts may add up across parts of the area with future rounds of convection later today into Wednesday. Most of the area will likely see 0.75-1.50" of rain through Wednesday, which on its own would cause river rises and perhaps push a couple of prone points towards minor flood. However, localized corridors of 2-3" of rain are possible if any training occurs, which could lead to isolated flash flooding and perhaps some river flooding if enough of a basin sees those kinds of totals. Confidence in widespread flooding impacts remains too low for a Flood Watch at this time, though will need to keep the potential for at least some limited impacts in mind and monitor rainfall trends.

KEY MESSAGE #3:

The next trough ejects out into the Plains Wednesday night, with this trough taking on a negative tilt and lifting into the Upper Midwest on Thursday. This will drive another (fairly weak) area of low pressure through the upper Great Lakes Thursday night and Friday. Tonight's cold front will briefly settle across southern Ohio on Wednesday, before lifting back north as a warm front ahead of the next low Wednesday night/early Thursday. Occasional shower (and perhaps some thunder) potential continues along and north of the front Wednesday and Wednesday night, with drier weather spreading in from the south late Wednesday night into Thursday as the front lifts through. It is now looking less likely that the front actually moves back through on Friday as a cold front, as the next low pressure approaches quickly Friday into Saturday. However, periodic shower and thunder chances along and ahead of the cold front will lead to occasional rain potential across the area Thursday and Friday. It will trend quite warm on Thursday, with much of the area likely to see highs top out between the mid 70s and lower 80s. Friday also looks more likely to again be in the 70s across the area, given the front trending towards not even moving back through as a cold front.

Overall, the Thursday and Friday timeframe doesn't look extremely concerning from a severe weather or heavy rain perspective. However, it will remain unsettled overall with occasional rain potential.

KEY MESSAGE #4:

Unsettled weather continues this weekend as a more formidable upper trough and associated surface low swing out of the Plains and into the Great Lakes. Locally, it looks like this evolution will drag a fairly strong cold front through between late Saturday and early Sunday. It will remain very warm with shower and storm chances ahead of the cold front. This will be a more dynamic system, so severe weather and heavy rain potential with any cold frontal convection will need to be evaluated over the coming days. With that said, an overnight frontal passage could help limit that potential to an extent. Either way, much chillier and generally drier weather likely returns for Sunday and Monday behind the front.

AVIATION /12Z Tuesday THROUGH Saturday/

Mainly VFR across the TAF sites early this afternoon, though anticipate deterioration to MVFR and IFR vsbys from showers and thunderstorms later this afternoon and evening. A few thunderstorms could pose a strong to severe wind threat, especially later this afternoon.

A few areas to watch for thunderstorms this afternoon. The first area will be over the next couple of hours, generally east of the I-77 corridor as showers and thunderstorms develop along a residual nocturnal outflow boundary. This area of storms will primarily impact ERI. The second area will be a cluster of thunderstorms currently across Indiana this afternoon which is expected to reach the I-75 corridor by around 4 PM. This cluster of thunderstorms is expected to become better organized over the next several hours as it continues east, posing a strong to perhaps severe wind threat to all TAF sites (briefly 40 to 45 knots, perhaps isolated up to 50). The third area of concern will be along an approaching cold front later this evening, with widespread shower and thunderstorm development likely. The threat for strong to severe winds is lower with this area, though non- zero.

Winds are generally out of the southwest early this afternoon, 15 to 20 knots with periodic gusts of 30 to 35 knots. Winds will abruptly shift towards the northwest, then north behind a cold front later this evening and overnight, 10 to 15 knots.

Outlook...Non-VFR likely in showers and low ceilings Wednesday afternoon. Additional periods of non-VFR conditions possible in showers and thunderstorms Thursday through Saturday, though appears most likely on Saturday.

MARINE

A warm front lies north of the lake this morning and while the warm sector is doing well with winds on land. Winds on the lake are a touch muted with the dome of colder air thanks to chilly lake temperatures. Therefore, will continue to ride a 15 to 20 kt wind forecast through this evening and omit a Small Craft Advisory at this time. A cold front will sweep across the lake tonight and winds will shift to the northwest and diminish. This front will lift back north as a warm front on Wednesday night, allowing for enhanced easterly ahead of the front and then southerly flow on Thursday. A low pressure system will pass to the northwest on Thursday, enhancing the southerly flow a touch. This low will pass a cold front across the lake on Friday, shifting winds to the southwest. This front will quickly lift back north with another low pressure system moving through the region for the weekend.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...None.