textproduct: Cleveland

WHAT HAS CHANGED

No major changes to the forecast.

KEY MESSAGES

1) Showers and thunderstorms will develop along and ahead of a cold front on Sunday. Some storms may be strong to severe, mainly along and east of the I-71 corridor.

2) A stronger low pressure system is expected to develop and move east through the Great Lakes Wednesday night into Thursday. Some stronger storms are possible, especially Wednesday night.

DISCUSSION

KEY MESSAGE 1... Shower and thunderstorm chances will return later tonight into Sunday as a compact shortwave traverses the axis of a broad upper-level trough rotating near southern Hudson Bay. Some uncertainty exists on the overall coverage of strong to severe storms with lingering overnight scattered convection and cloud cover expected to arrive east into the area Sunday morning. The current thinking is that two rounds of showers and storms are expected on Sunday with strong to damaging wind gusts being the primary severe hazard, given generally straight and long hodographs.

The first round of showers and storms will likely initiate off of the remnant overnight convection, generally east of the I-77 corridor from around Noon to 3 PM and should carry the higher strong to severe storm chances. The second round appears to initiate along the advancing cold front, generally along and east of the I-71 corridor between 1 to 6 PM. Although the downstream environment won't be as favorable with the second round of storms along the cold front, could still see a few isolated instances of stronger wind gusts given modest 700 mb westerly flow of 35 to 40 knots. A lesser threat exists for flash flooding, though anomalously- high PWATS and generally skinny CAPE profiles will lead to heavy rain.

KEY MESSAGE 2... Continuing to monitor the potential for a highly-anomalous low pressure system to develop and move east through the Great Lakes late Wednesday into Thursday. Model guidance is beginning to come into agreement for mid to upper-level trough placement and strength, though specific surface features still remain uncertain. Low-level moisture is forecast to quickly increase ahead of the advancing surface low Wednesday night, with dew points climbing into the 60s.

At this time, it appears the most favorable CAPE/shear overlap (reflected by ENS probs of MUCAPE > 1000 J/jg) and the highest potential for severe weather will reside just to the south and southwest of the area, though will continue to monitor trends for this potentially significant system. Do think the severe potential on Thursday (currently highlighted by the SPC SWODY6), is decreasing across our area, with the pace of the low pressure system and associated outflow boundaries appearing to favor higher severe weather chances further south and east of the area.

In addition to the threat of strong to severe storms, we may also have to contend with the strong associated wind field of this system, with currently low to medium probs (20 to 40%) for wind gusts to exceed 45 mph Wednesday night into Thursday afternoon.

AVIATION /00Z Sunday THROUGH Thursday/

VFR will prevail through the overnight, but showers and associated lowering of cigs will begin to spread in from west to east after sunrise Sunday morning. This will eventually lead to MVFR in all areas by mid morning or early afternoon as the showers expand in coverage. Embedded thunderstorms are expected to develop in north central and NE Ohio during the mid to late morning then gradually move into NW PA during the afternoon, so have the greatest coverage of TSRA at KCLE, KCAK, KYNG, and KERI from mid morning through mid afternoon. These areas will also see periods of IFR during the afternoon. Drier air and improving cigs/vis will gradually work in from west to east Sunday evening.

SW winds will decrease to 5-15 knots tonight before gradually turning NW and increasing to 15-25 knots as a strong cold front drops across the region late Sunday morning through the afternoon.

Outlook...Periodic showers and thunderstorms with non-VFR are forecast Tuesday afternoon through Thursday.

MARINE

Southwest winds 6 to 12 knots are expected through today with winds increasing by a few knots overnight into early Sunday. A cold front will cross the lake on Sunday, allowing winds to shift to the northwest. A period of winds to 15 to 20 knots is likely in the western basin of Lake Erie Sunday afternoon/evening, but confidence in Small Craft Advisory conditions occurring is low at this point. Headlines may be needed if winds trend a bit higher.

From there, Small Craft Advisories/Beach Hazards Statements may be needed as southwest flow deepens ahead of an approaching strong cold front Wednesday. NBM guidance suggests that winds could reach or exceed 30 knots on Thursday so will need to continue to monitor forecast trends in the upcoming days.

CLE WATCHES/WARNINGS/ADVISORIES

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