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... Surface low pressure centered near Hudson Bay this afternoon will continue eastward across northern Quebec this evening. This will push a trailing cold front slowly across Lake Erie, but the front will stall near the southern shore tonight in response to another mid/upper shortwave progressing through the central Great Lakes and inducing a weak surface wave on the front.

Regional radar loops this afternoon show a band of scattered showers and some embedded weak convection along the front from SW Ontario to far NW Ohio and northern Indiana. This activity will gradually sink across Lake Erie this evening, but the latest HREF CAMS are trending toward a less inland push to the showers, keeping them confined to close to the lakeshore. This makes sense given the stalling boundary tonight, so tweaked POPS to keep the rain chances over the northern counties. Most of this will just be light nuisance rain showers, but afternoon mesoanalysis shows 500 J/Kg of SBCAPE in north central and NE Ohio, with 100-250 J/Kg of MLCAPE. This weak instability coupled with 25-30 knots of effective shear could support a few embedded convective cells with a few lightning strikes and gusty winds over 40 knots. Overall low impact with no severe weather expected.

The showers will gradually shift out over Lake Erie and north of the region late tonight as the front lifts slightly north in response to the secondary wave developing upstream. Since the mid/upper jet support associated with this wave will be farther south compared to this evening's initial push of the front, expect coverage of rainfall to be much more widespread Friday as the weak low crosses the southern Great Lakes and pushes the frontal boundary slowly southward. 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 some embedded convection is possible in the southern counties Friday afternoon, no severe weather is expected. Any convection would just produce locally heavier rain. Total QPF Friday should average 0.35 inches or less except locally higher where any convection occurs, so no flooding is expected.

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 /18Z Thursday THROUGH Tuesday/

A cold front brings isolated to scattered showers after 21Z today, lifts back north briefly, then settles back into the area for Friday and higher chances for rain after 12Z Friday. VFR conditions turn to IFR/MVFR in lowering ceilings west of CLE-MFD line and visibilities dropping in precipitation as well. Wind gusts through 23Z at 20-30kts cease tonight with another period of LLWS possible after 05Z. Gusts resume at 20-30kts after 13Z Friday out of the southwest.

Outlook...Non-VFR expected in periodic rain showers and thunderstorms through Friday evening and again Sunday night through Monday.

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.