textproduct: Cleveland

WHAT HAS CHANGED

Winds have further trended up along the lakeshore from Cuyahoga to Erie County, PA tonight and Sunday morning. Wind gusts of 35 to 45 mph are likely at times. Rainfall amounts have slightly decreased tonight and Sunday.

KEY MESSAGES

1) Periods of rain and breezy conditions are expected tonight through Sunday associated with the remnants of Isaias. Winds will be highest along the lakeshore from Cuyahoga to Erie County, PA, where gusts of 35-45 mph are possible.

2) Unseasonable warmth Monday and Tuesday before a cold front moves in late Tuesday, bringing some showers and thunderstorms.

3) Cooler and unsettled the rest of the week.

DISCUSSION

KEY MESSAGE 1... Quiet and pleasantly mild conditions will continue for the remainder of the afternoon and evening as surface high pressure over New England gradually departs east. This will start to strengthen the southeasterly pressure gradient between the high and the remnant low of Isaias, so some gusts up to 20 or 25 mph are possible by mid evening, especially where downsloping is favored in a SE low-level flow set up from northern Cuyahoga County to northern Erie County, PA. Otherwise, clouds will just continue to increase.

The main impacts from Isaias will occur tonight and Sunday as a strong mid/upper trough progressing into the West Coast deepens mid-level southwesterly flow across the central CONUS. This mid-level jet will start to eject the remnants of Isaias ENE at a pretty good clip. The remnant low is currently moving into Middle Tennessee and will lift across West Virgina Sunday afternoon before exiting the Mid Atlantic coast Sunday night. In terms of winds, breezy conditions are still expected as the pressure gradient tightens and an area of 35-40 knot 850-925 mb winds moves overhead late tonight and Sunday morning. However, RAP forecast soundings show conditions becoming fairly saturated rapidly after 06Z, and this combined with a slowly weakening wind field will limit most gusts to around 30 mph. The exception will be where the SE low-level flow set up leads to downsloping from northern Cuyahoga County to northern Erie County, PA. This will locally increase wind gusts, so gusts to 35-45 mph are possible there. Winds will increase after 06Z, with peak gusts in the 08 to 18Z Sunday window. Winds will turn N to NE behind the departing low late Sunday afternoon and rapidly diminish. In terms of rain, the shield of steady rain is still expected to lift across the region tonight and Sunday morning, with additional showers wrapping around the back side Sunday afternoon. However, QPF is trending lower due to a slightly farther SE track of the low and mid-level dry air wrapping farther north. Some locally heavy convective banding is still possible, especially along a KCAK to KYNG line, but most of the rain will be light to moderate stratiform. There remains an unusually high amount of QPF variability in HREF and RRFS guidance and individual members, including run to run flips, so confidence in exact rainfall amounts is lower than normal. The overall trend has been lower, so used a blend of NBM and WPC for the final QPF forecast which is a close compromise of HREF and RRFS ensemble QPF. This gives a few tenths to 0.25 inch in NW Ohio, 0.50 to 0.75 inch in north central Ohio, and 0.75 to 1 inch in NE Ohio (east of I-77) and NW PA. Probabilities for locally higher amounts are greatest near that KCAK to KYNG line. These rainfall amounts and low stream flows combined with drying ground should prevent any flooding except for areas that may have blocked drains or culverts. The showers will start to move in from south to north after 03Z, with the steadiest rain in the 06Z to 15Z Sunday window. The rain will be more intermittent Sunday afternoon as the low pulls away.

After drying out Sunday evening, it is possible to see some additional scattered, light showers Sunday night as an inverted surface trough and some low-level moisture hangs back across the area. This is shown by a few HREF members, so added low POPS Sunday night. Another showers will quickly end by Monday morning.

KEY MESSAGE 2... Broad mid/upper ridging will briefly flex over the eastern CONUS Monday and Tuesday as the aforementioned western CONUS trough evolves into a cut off low. This combined with surface high pressure settling over the Mid Atlantic region will support deep southerly flow and well above normal temperatures. Look for highs to reach the 75 to 80 degree range in NW Ohio Monday and upper 60s to low 70s in NE Ohio and NW PA. Most of the CWA will see mid 70s to low 80s Tuesday. A shortwave dropping through the central/eastern Great Lakes late Tuesday into Wednesday will push a cold front into the region. This front is trending slower as the cut off low over the West keeps mid/upper ridging in place across the Tennessee Valley and Southeast CONUS. The front should still manage to push through late Tuesday or Tuesday night before stalling near the Ohio Valley, so showers and thunderstorms are possible ahead of the front. There will be some instability ahead of the front to support thunder given the warmth, but a later trend should limit any strong/severe potential. Will need to watch for gusty winds though given favorable shear.

KEY MESSAGE 3... As mentioned above, the front will become quasi-stationary near the Ohio Valley by Wednesday and linger through the end of the week as it runs into lingering mid/upper ridging. High pressure over the northern Great Lakes will bring seasonably cooler and drier overall air, but occasional showers are still possible given the boundary nearby. The next more significant system may come Friday as a stronger northern stream mid/upper trough captures the old Western CONUS cut off low and potentially leads to a strong frontal passage across the Great Lakes. This would bring better chances for rain, gusty winds, and potentially the coolest air of the season so far late Friday into Saturday if it materializes.

AVIATION /18Z Saturday THROUGH Thursday/

A shield of rain and lower ceilings will overspread the area overnight tonight into Sunday as the remnant low pressure from Isaias lifts towards the Ohio Valley. VFR conditions will continue through this evening and the first half of tonight. There will be some MVFR vis restrictions with more intense showers late tonight into Sunday, with potential for brief IFR vis with heavier showers and/or with a steadier period of rain, especially towards MFD, CAK, and YNG. Ceilings will fall to MVFR as showers become widespread early Sunday, with most sites likely to drop to IFR at some point during the day Sunday. Timing of the drop to IFR ceilings is less confident at CLE, ERI, and YNG due to downsloping winds, and have a slower ceiling drop at those sites compared to the rest. Kept CLE low MVFR until 18z when winds begin shifting more E-NE with this update.

Winds will generally remain southeast through the TAF period, before beginning to shift more east-northeast later Sunday into Sunday night. Speeds will generally be 5-10kt through the first half of tonight, increasing slightly late tonight into Sunday. Due to downsloping, some 25-30kt wind gusts can occur at ERI overnight tonight and Sunday morning.

Outlook...Showers and low ceilings with potential for widespread IFR continue late Sunday and Sunday night, with gradual improvement from west to east late Sunday night into Monday. Non-VFR possible Tuesday with scattered showers/storms.

MARINE

Southeasterly winds will increase on Lake Erie tonight and Sunday morning as the remnants of Isaias pass to the south. Winds in the 15-20 knot range are mostly expected, with periods of 20-25 knots possible from Avon Point to Ripley. Issued marginal Small Craft Advisories tonight from Avon Point to Ripley, with the best potential for criteria to be reach at times between about 02 and 10Z. Winds will rapidly decrease Sunday morning, becoming NE at 5-10 knots by late afternoon then NW at 5-10 knots Sunday night.

Light winds are expected Monday as high pressure builds in before SSW winds increase to 15-25 knots Monday night and Tuesday ahead of a cold front. Winds will turn NW behind the front Tuesday night and decrease before a period of possibly stronger NE winds by late Wednesday and Thursday as high pressure tries to build from the north.

CLE WATCHES/WARNINGS/ADVISORIES

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