textproduct: Cleveland

WHAT HAS CHANGED

No major changes to the forecast with this update.

KEY MESSAGES

1) Scattered showers and isolated thunderstorms expected near the lakeshore this evening into tonight followed by more widespread rain Friday. Severe weather is not expected.

2) Much above normal temperatures Sunday through most of next week with gradually increasing chances for showers and thunderstorms.

DISCUSSION

KEY MESSAGE 1... W'erly flow aloft and embedded shortwave disturbances continue to affect our region through daybreak Friday. At the surface, a front has stalled in vicinity of the Toledo metro area and the southern shore of Lake Erie in our CWA. After about 9 PM EDT this evening, the front is expected to begin to shift back N'ward as a warm front and become located near the northern shore of Lake Erie by daybreak Friday as one frontal low wobbles E'ward across northern QC and another frontal low wobbles NE'ward from northern KS to southeastern Lower MI. Primarily dry weather is expected through daybreak Friday as the boundary layer stabilizes via nocturnal cooling. However, isolated rain showers and thunderstorms are expected over and very near Lake Erie in our CWA, especially prior to midnight EDT tonight, as moist isentropic ascent along the upper-reaches of the front releases weak and elevated CAPE. Low temperatures should reach mainly the lower to mid 50's around daybreak Friday as net low-level WAA behind the front contributes to somewhat limited nocturnal cooling.

Expect favorable mid/upper-level jet streak dynamics and associated large-scale tropospheric ascent to permit the coverage of rainfall to be much more widespread on Friday as the weak low crosses the southern Great Lakes and pushes the front generally southward as a cold front in our CWA. The right entrance region of a 90-100 knot H3 jet streak crossing Lower Michigan will generate a swath of fairly steady rain across Illinois, Indiana, and Lower Michigan Friday morning that will slowly sink across the region during the day. In terms of timing, expect rain to reach a Sandusky to Findlay line by 14Z and an Erie, PA to Mansfield line by 18Z. The swath of rain showers will then continue sinking slowly southward the rest of the afternoon and evening. Abundant cloud cover and rain will keep instability very low Friday, so while isolated thunderstorms are possible in our southern counties Friday afternoon, no severe weather is expected. Any storms will produce locally heavier rain. Total rainfall on Friday should average 0.35 inches or less in our CWA, but localized higher amounts are possible from thunderstorms. Even so, flooding is not expected. A few peeks of sunshine and low-level WAA ahead of the cold front should allow daytime highs to reach mainly the 60's to lower 70's.

KEY MESSAGE 2... The frontal boundary will briefly be forced south to the Ohio River Valley Saturday behind the low as Canadian high pressure at the surface builds down across the Great Lakes. This will bring cooler temperatures, especially near the lakeshore, as low-level winds turn NE. The change will be short lived though as the front already lifts back northward Sunday in response to a strong mid/upper low progressing into the California/Oregon coasts forcing strong amplification of mid/upper ridging over the eastern CONUS. This will set up a broad southwesterly flow pattern through most of next week leading to very warm and increasingly humid conditions. Temperatures will climb into the low to upper 70s Sunday and Monday and upper 70s to low 80s Tuesday and Wednesday. The next cold front continues to trend slower, so temperatures will likely stay well into the 70s through Thursday.

In addition to this being an unseasonably warm pattern, it will also be an active pattern as the aforementioned closed low slowly progresses into the Plains by midweek and evolves into a broad mid/upper trough. This will eject weak shortwaves across the Mississippi and Ohio Valleys in the broad SW flow, and given the increasing low-level moisture and instability, periods of showers and thunderstorms will result. There will not be much in the way of forcing until the main piece of the remnant trough approaches toward the end of the week, so expect convection to be scattered and peak during the afternoon/evening diurnal cycles until perhaps a more organized round toward Wednesday or Thursday depending on how the trough and associated cold front evolve. Again, the trend has been slower.

AVIATION /00Z Friday THROUGH Tuesday/

W'erly flow aloft and embedded disturbances affect our region through 00Z/Sat. Variable amounts of low/mid/upper-level cloud cover will precede the disturbances' axes. At the surface, a front has stalled in vicinity of KTOL and the southern shore of Lake Erie as of 23:30Z/Thurs. This front should begin to drift N'ward as a warm front after 00Z/Fri and near the northern shore of Lake Erie by 12Z/Fri as a low wobbles NE'ward from northern KS to southeastern Lower MI. The low should then wobble farther NE'ward to near the QC/ME border and strengthen through 00Z/Sat. This should allow the trailing cold front to sweep SE'ward across our region between ~16Z/Fri and 00Z/Sat. Behind the cold front, a ridge builds from the north-central United States.

Prior to the cold front passage, our regional surface winds should trend S'erly to SW'erly around 5 to 15 knots and gust up to about 25 knots at times after ~14Z/Fri. Note: the development of a nocturnal and SW'erly low-level jet of ~40 to 60 knots at/near 925 mb is expected to result in a period of low-level wind shear overnight tonight until ~14Z/Fri. Behind the cold front, our regional surface winds veer to NW'erly and then toward N'erly while remaining around 5 to 15 knots in response to the building ridge.

Mainly dry weather and VFR are expected for the time being. However, periods of light to moderate rain and isolated thunderstorms with brief MVFR to IFR are possible along and near the southern shore of Lake Erie through ~05Z/Fri as the aforementioned stalled front eventually begins to shift N'ward. This includes KTOL, KCLE, and KERI. Ahead of and along the cold front at the surface and aloft, widespread light to moderate rain and lower ceilings should overspread our region generally from west to east between ~13Z/Fri and ~17Z/Fri. Once the rain arrives, conditions should deteriorate to MVFR to IFR fairly quickly. As the surface ridge builds behind the cold front, rain should end generally from northwest to southeast at/near KTOL and KCLE after ~21Z/Fri, but widespread MVFR to IFR ceilings should persist.

Outlook...Non-VFR expected with periodic rain showers Friday night and again this Sunday through Tuesday. Periodic thunderstorms should occur this Sunday through Tuesday.

MARINE

A cold front will drop down into the southern Great Lakes this evening, and will push completely through the region Friday. Offshore winds will become onshore behind the cold front as wave heights increase to the 1-3ft range through Saturday. Winds become offshore once again through Sunday night, and then increase out of the southwest to the 15-25kts range Monday through Tuesday. During that time frame, wave heights will increase rapidly with distance from shore and will be in the 3-5ft range in the open water zones.

CLE WATCHES/WARNINGS/ADVISORIES

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