textproduct: Cleveland

WHAT HAS CHANGED

A Marginal Risk for severe thunderstorms has been introduced for Saturday afternoon and evening across much of the area.

KEY MESSAGES

1) Cool and rainy late this afternoon through tonight across much of the area, with the least rain across Toledo and along the lakeshore.

2) After a drier and warmer morning and early afternoon, showers and thunderstorms move across the area later Saturday afternoon and evening. There is a Marginal Risk (level 1 of 5) for isolated severe weather in the form of damaging winds and hail up to quarter-sized.

3) Drier weather works in from the northwest Sunday and Sunday night, with cooler, dry weather expected to start next week. Some frost is possible Sunday and Monday nights.

DISCUSSION

KEY MESSAGE #1:

A warm front is currently pushing into our far southwestern counties this afternoon and will slowly lift across the area this evening into tonight. A flat shortwave will move through the region tonight and early Saturday morning, which will combine with the front and a band of moisture advection to squeeze out a round of mainly stratiform rain. Already seeing some rain across interior portions of our area this afternoon (though some low-level dry air is keeping it quite light for now), and expect rain to gradually expand and turn steadier through the first half of tonight. Rain will then gradually exit to the east and southeast late tonight/early Saturday. There will be a sharp cut-off to the rain this evening, with the Toledo area and even northern Erie County PA quite possibly staying dry. The heavier rain amounts will be just south of Cleveland this evening, though there are decent odds (80%) for lighter (but still measurable) rain in Cleveland this evening. The swath of better QPF across our inland counties will produce 0.30-0.75" through tonight, dropping off to the north. This will be another soaking rain with minor river rises, though shouldn't be more significant than that. Lows will generally be in the upper 40s and lower 50s tonight.

KEY MESSAGE #2:

The forecast for Saturday has trended more impactful, especially during the later afternoon and early evening hours. We are still looking at a window of warmer and dry weather to start, with tonight's rain expected to exit by early Saturday. Once we dry out early Saturday, rain chances don't ramp back up until closer to 2-6 PM from northwest to southeast. Highs should push to near or a bit better than 70 in the well-mixed warm sector ahead of the approaching cold front and showers/storms later in the afternoon. Synoptically elevated southwest breezes may gust up to 30 MPH in the warm sector.

Turning our attention to the more active weather, a flat shortwave will zip across the southern Great Lakes Saturday afternoon and evening as low pressure tracks across the northern Great Lakes. This will push a cold front into the local area. The lift associated with the shortwave and front coinciding with peak daytime heating leads to higher confidence in a round of showers and storms with good coverage, particularly across Lake Erie and adjacent Northeast OH and Northwest PA where the forcing from the shortwave will be most favorable. Storms may begin developing across southeastern Michigan around midday, with activity then expected to develop and/or spread into the local area after 2 or 3 PM from the west-northwest.

With dew points ahead of the front struggling to push above the lower 50s, the amount of moisture and resultant instability will be marginal for severe weather. However, strong surface heating beneath chilly air aloft should yield steep low-level lapse rates and 500-1000 J/KG of low-topped MLCAPE during the afternoon. This, along with moderate deep-layer shear as flow above 600mb increases to 50-60kt, may be enough for a few strong to severe storms. While the strong forcing does argue for a more linear mode, shear vectors are favorable for a more cellular mode. Most hi-res models suggest an initial mix of cells and short line segments gradually congealing into a more linear mode. The moderate to strong flow aloft and resultant fast storm motions, when combined with the expectation of well-mixed low- levels, suggests strong to locally severe wind gusts are the main severe weather risk...particularly with more organized linear convection. With colder air aloft and sufficient deep-layer shear, a few more robust cells may also pose a risk for marginally severe hail. The tornado risk is not truly zero, but marginally high LCL heights, unidirectional low-level flow, and a likely messy/mixed storm mode should keep the tornado threat rather minimal.

Overall, feel the broad SPC Marginal Risk (level 1 of 5) for severe weather across the area in the new Day 2 outlook captures the threat well. While a small corridor of more focused severe potential could play out with a more linear storm mode, particularly across Northeast OH and Northwest PA, the marginal overall thermodynamics and some model disagreement on where the most organized convection will occur currently precludes anything more than the Marginal Risk. As mentioned above, these showers/storms and attendant severe risk begin spreading in as early as 2-3 PM from the west-northwest. Any severe risk should subside by about 9 PM as forcing shifts off to the east and as the low-levels become worked over and more stable.

The front will slowly push southeast through Saturday night, though may not completely clear our area until early Sunday. Another weak shortwave will bring an uptick in shower potential late Saturday night/early Sunday across the area. Lows Saturday night will generally range from the mid 40s to near 50.

KEY MESSAGE #3:

Drier weather should continue working in from the northwest on Sunday as high pressure approaches and the front exits. High pressure builds overhead to start next week, keeping us dry through at least much of Tuesday. There's decent agreement in a system of some kind around midweek, bringing our next potential for rain.

A cooler airmass is expected to start next week, with highs likely stuck in the 50s for most of the area on Monday before a gradual warm up starts on Tuesday. Overnight lows in the 30s and 40s are expected, bringing frost concerns on any nights with more favorable radiational cooling conditions. Some frost is possible as early as Sunday night if clear/calm conditions develop quickly enough, with perhaps better potential Monday night with high pressure overhead.

AVIATION /18Z Friday THROUGH Wednesday/

The main weather concern and potential impact to aviation will be ceilings lowering tonight and some visibility reduction of 3sm to 5sm due to scattered rain showers and light fog developing overnight. As of mid afternoon, VFR ceilings are starting off this TAF period. By this evening after 00z, there will be an area rain showers and isolated thunder possible moving from west to east across the region. This round of showers will move through overnight with ceilings gradually lowering to MVFR late this evening. The MVFR ceilings and visibilites are highlighted by PROB30 between 00z and 09z for each TAF site. Later tonight into early Saturday morning after the showers move out, areas of light fog and low stratus will likely develop with most locations seeing IFR ceilings between 09z and 13z. Ceilings will gradually lift and improve to either MVFR or VFR category by late Saturday morning and the end of the TAF period.

Winds will start off from the west or southwest this afternoon 5 to 12 knots. A weak lake breeze has developed this afternoon at CLE and ERI with a light northerly wind 5 to 8 knots is expected through about 21z or 22z. Light southwesterly winds will resume at CLE and ERI by early evening. Light south or southwest winds around 5 to 8 knots is expected overnight through early Saturday morning. Towards the end of the TAF period, gusty southwest winds will return 10 to 15 knots gusts to 25 after 15z Saturday morning.

Outlook...Non-VFR expected this weekend with scattered showers mainly Saturday afternoon through Sunday morning. A few scattered thunderstorms may be possible Saturday afternoon into Saturday evening. Non-VFR possible with showers and isolated thunder Tuesday night into Wednesday.

MARINE

Overall marine weather and the conditions on Lake Erie will be somewhat quiet this weekend into early next week. There will be a couple weather systems moving through the Great Lakes over the next several days that will bring wind shifts and some rain chances. Winds are rather light and variable this afternoon with a weak low level flow over the lake at this time. A weak area of low pressure will skirt south of Lake Erie tonight with a round of showers and possible isolated thunder. Winds will resume a southerly flow late this afternoon into tonight 5 to 12 knots and waves 1 to 2 feet. A cold front will approach the area late Saturday and southwesterly winds will increase 15 to 20 knots during the day. Waves will increase 1 to 3 feet mainly in the open waters of the basin. The front will push across the lake Saturday night and a northwesterly will follow behind it 10 to 15 knots into Sunday. Waves will continue 1 to 2 feet on Sunday.

Another secondary surface trough or cold front will move through the eastern Great Lakes Sunday night into early Monday with a slight reinforcing push of northerly to northwesterly winds 10 to 15 knots and waves 2 feet or less. High pressure builds in with lighter winds Monday night and early Tuesday. A light southerly flow 5 to 12 knots will return by Tuesday.

CLE WATCHES/WARNINGS/ADVISORIES

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