textproduct: Cleveland

WHAT HAS CHANGED

With this update, slowed the progression of showers east across the area today given current trends and placement of the boundaries. Widespread precipitation is still expected tonight into Sunday with similar rainfall totals as previous forecasts.

KEY MESSAGES

1) Showers with isolated thunderstorms will gradually spread east across the area today, becoming more widespread tonight. Heavy rainfall and localized flooding remain the primary concerns.

2) An unsettled weather pattern lingers through much of next week bringing the potential for multiple rounds of precipitation and cooler temperatures.

DISCUSSION

KEY MESSAGE 1... This morning, a mid-level ridge over the Gulf Coast is resulting in a near zonal flow over much of the upper US with a developing trough over the Rocky Mountain region. Widespread showers are being observed upstream of the area as an upper level shortwave provides energy for development on the northern periphery of the aforementioned ridge. This pattern will slowly drift east, resulting in the showers to gradually spread east across the area today. Initial showers this morning are expected to only impact the western/southwestern counties as development and storm motion follows the instability gradient. However, with a weakening high pressure centered over the northern Great Lakes pushes east, a warm front associated with a surface low over Midwest will be able to nudge further north towards the CWA. This boundary will likely become the focus for additional shower development and will ultimately act as a path that the low pressure will follow into the southern Great Lakes region. As this boundary and the low get closer to the area tonight, showers are expected to become widespread across the entire area with periods of heavy rain possible overnight. On Sunday, this low will drag a strong cold front southeast through the area, again enhancing shower and possible thunderstorms development along it. Conditions should begin to dry out from north to south on Sunday afternoon as this boundary pushes through.

There remains some uncertainty with this forecast, especially in regards to how far north the aforementioned warm front will lift, however confidence continue to grow in regards to the potential for heavy rainfall and the potential for localized flooding. The current forecast through Sunday afternoon has 1-1.5 inches of rain falling along a line from Cleveland to Youngstown and west with portions of far NE OH and NW PA expected to get between 0.75-1 inch of rainfall. Deepening warm cloud layers and anonymously high PWAT values are expected to couple with storm motion parallel to the flow and result in showers training. In areas impacted by this training, high QPF values can be expected. To highlight this concern, WPC has placed much of the area in a Day 1 Slight (2 of 4) ERO with portions of NE OH and NW PA in a Day 1 Marginal (1 of 4) ERO. Given the potential for showers, widespread cloud cover, and the area likely staying north of the warm front, there is minimal risk of severe weather although a few rumbles of thunder cannot be ruled out. High temperatures today and Sunday will climb into the 70s with overnight lows tonight dropping into the 60s.

KEY MESSAGE 2... An active weather pattern is expected to persist through much of next week as multiple midlevel troughs move east across the northern US, bringing the chance for multiple rounds of precipitation and the first real taste of fall. Some models have continued to suggest a cut off low developing over the region midweek and persisting through late week. This pattern would support a northerly flow, keeping cool temperatures around, but given model divergence this far out and the inherent uncertainty, timing of any precipitation after midweek and the exact temperatures may adjust some in coming forecasts. The current forecast suggests that highs beginning on Monday into next weekend will be in the 60s with overnight lows dropping into the 50s with patches in the 40s across NWPA.

AVIATION /06Z Saturday THROUGH Wednesday/

The challenge through the TAF period will be timing rain as it moves if from the northwest today and determining the potential for thunderstorms at any of the terminals. Conditions are starting off VFR at all sites with mid and high level cloud in the 12-20K range. Light showers can be seen upstream across lower Michigan and will try to approach TOL after 10Z and FDY after 11Z. Dry air in the low levels is delaying the arrival of showers at the surface as some is being lost to evaporation. Rain is expected to fill in along the I-75 corridor between 14-18Z and included a tempo at TOL/FDY for moderate showers. Instability is limited and confidence is low in thunderstorms today. We are watching a larger complex of thunderstorms located over southern Wisconsin and this will tend to track towards SW Ohio this afternoon. Otherwise, impacts from showers will be limited today as rain will be light as it expands eastward through the afternoon. Did include a tempo for showers at CLE in the 18-21 time frame. Ceilings will tend to remain VFR at most terminals into tonight with lower confidence at TOL where they may see some MVFR cloud by late afternoon. A more organized area of showers and possibly thunderstorms is expected to move into northern Ohio between 06-12Z Sunday.

Northeast winds of 5-10 knots will shift out of the east today and southeast at southern terminals.

Outlook...Non-VFR possible with showers and occasional thunderstorms through Wednesday.

MARINE

As high pressure begins to shift out of the region, a warm front is expected to slowly push north towards the southern Great Lakes today. This will allow winds to remain from the east at 5-15 knots with nearshore waves 2 feet or less. This aforementioned front will act as a path for a low pressure system to travel from the Midwest towards Lake Erie by Sunday. This will result in shifting and strengthening winds to be from the northeast at 15-20 knots by Sunday afternoon. This will result in waves building to 3-5 feet and this period will likely be the start of prolonged hazardous marine conditions across Lake Erie. As this low slowly shifts east, a surface trough with a strong gradient will result in northeast winds increasing to 20-25 knots beginning Sunday night and possibly persisting into mid-week. At times, these winds may even approach Gales, although the timing and duration of that potential remains low. As these winds increase and persist, waves across Lake Erie are expected to build to 6-8 feet with locally higher waves possible. This period will be extremely dangerous to small crafts and will likely increase rip currents along the southern shore of the lake. A long duration Small Craft Advisory will be needed as well as a Beach Hazards Statement through at least Wednesday and will have to monitor for any additional time.

CLE WATCHES/WARNINGS/ADVISORIES

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