textproduct: Cleveland

WHAT HAS CHANGED

Current forecast remains on track compared to previous forecast cycle.

KEY MESSAGES

1) Shower and thunderstorm chances increase across the area late Saturday through Sunday. Heavy rainfall possible at times with strong to severe storms Sunday afternoon.

2) Unsettled weather pattern for the first half of next week, with periodic shower and thunderstorm chances.

DISCUSSION

KEY MESSAGE 1...

Aside from a few stray showers that could develop across portions of north central and northeast Ohio later this afternoon into early evening, dry conditions expected until shower chances increase through the day on Saturday. A positively tilted upper trough/closed low and attendant surface low pressure will slowly move east from the mid Mississippi valley into the Ohio valley Saturday through Sunday.

Shower and storm chances increase late tonight into early Saturday morning from west to east. The best chances for precip during the daytime will generally be west of the I-71 corridor, particularity in the far southwest portion of the forecast area from Findlay to Marion. Precip chances will increase across the rest of the area Saturday night as the low level jet ramps up and convergence increases across the area. Heavy rainfall will be possible with any convection, as PWAT values increase to 1.75-2.00 inches across the area. Hi-res guidance seems to focus the heaviest precip west of the area on the northwest flank of the surface low, but this precip maxima could sneak into the I-75 corridor by early Sunday morning depending on the evolution of the system. WPC is highlighting the far western part of the area in a slight risk of excessive rainfall Saturday and Saturday night.

As the upper trough amplifies over the region Sunday, mid/upper flow will increase a bit on the downstream side of the trough. Shower and storm activity will impact the forecast area as the surface low slowly pivots eastward. WPC continues to highlight a slight risk of excessive rainfall for much of the forecast area on Sunday with the combination of slow moving/training storms and intense rainfall rates leading to an increase in flash flood potential. SPC is highlighting areas east of the I-77 corridor with a marginal risk of severe weather. Deep layer effective shear of 30-35 kts during the afternoon, combined with MLCAPE values of 1000-1500 j/kg, could lead to some strong to severe thunderstorms as the convection tracks east out of the area into the evening. Damaging winds would be possible, and a tornado or two cannot be ruled out with low LCLs and somewhat favorable hodographs.

KEY MESSAGE 2... Confidence increasing in unsettled weather across the area Monday through Wednesday, as aforementioned mid/upper trough cuts off over the Ohio valley Monday. This will bring diurnally driven shower/storm chances through Wednesday before the low fills and lifts northeast into New England ahead of a northern stream shortwave moving into the northern Great Lakes region. This will also keep conditions humid and temperatures near seasonal normals. Areas that see heavy rainfall over the weekend could be vulnerable to an increased risk of flash flooding with any slow moving or training storms during this period.

AVIATION /18Z Friday THROUGH Wednesday/

VFR conditions are expected this evening with cumulus clouds around 4-6kft lingering through the rest of the afternoon/evening. A few light are possible near KMFD, KCAK, and KYNG over the next couple hours.

A low pressure system approaches from the southwest, with rain showers overspreading the area west to east starting near the I-75 corridor Saturday morning and continuing across the rest of the area through the afternoon/evening hours. There may be periodic non-VFR conditions with heavier showers but prevailing conditions should be mainly VFR still. Lightning isn't expected until the late afternoon hours of Saturday, and even then the probability is low at this point (~20%).

A lake breeze brings northerly winds to KCLE and KERI this afternoon, otherwise light and variable winds through the overnight hours. Southeast winds develop Saturday morning and approach 10 knots by Saturday afternoon.

Outlook...Non-VFR conditions in showers and thunderstorms are expected Saturday afternoon through Sunday night. Scattered showers and thunderstorms continue Monday through Wednesday, primarily during the afternoon hours.

MARINE

Low pressure approaches from the west, potentially moving eastward south of or across Lake Erie Sunday into Monday. There is good deal of uncertainty with this forecast update regarding the low pressure system track, which greatly influences the wind and waves forecast for Saturday night through Monday. There is moderate confidence that there will be a period of east to northeast flow sometime Saturday night through Sunday, followed by higher confidence in northeast to north flow on Monday. It's becomingly increasingly likely that there will be a period of 15-20 knot onshore flow with waves in the 3 to 5 ft range, especially east the Island towards the Cleveland area, but there is a lot of uncertainty in exact timing. We will have to continue to monitor for possibly dangerous conditions for swimmers and small craft, especially in the central basin of Lake Erie.

Conditions on Lake Erie are likely to improve by midweek.

CLE WATCHES/WARNINGS/ADVISORIES

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