textproduct: Cleveland

WHAT HAS CHANGED

Confidence is increasing in widespread showers and thunderstorms this afternoon through tonight with scattered to numerous severe storms across the area. Much of the area has been upgraded to an Enhanced Risk (Level 3 of 5) of severe weather from the Storm Prediction Center to best reflect the severe potential later today.

KEY MESSAGES

1) Severe weather is expected this afternoon through tonight with all severe hazards possible (i.e. - damaging wind gusts, large hail, and tornadoes). Storms will be fast moving but will also train over the same areas, which may allow for locally heavy rainfall and isolated flooding.

2) Cool, but dry, weather is expected on Friday and Saturday. A resurgence in warmer temperatures will begin on Sunday with unsettled weather following in on Monday, allowing for periodic rain chances for much of the week.

DISCUSSION

KEY MESSAGE 1... The combination of a warm front and strong low level jet entering the area this morning will allow for two windows of showers and thunderstorms later today with all severe hazards of damaging wind gusts, large hail, and tornadoes possible. The first window is from 1 to 4 PM for far NE Ohio and NW PA with a conditional, isolated severe window with the warm front. The second window is from 5 PM to Midnight, when showers and storms will be expected areawide, moving from the northwest to the southeast, as the warm front returns south as a cold front. Much of the area has been upgraded to an Enhanced Risk (Level 3 of 5) of severe weather from the Storm Prediction Center to best reflect the severe potential later today.

The warm front is over central Illinois and southern Indiana this morning and will continue pushing northeast toward the forecast area. This front has generated a fair amount of elevated convection that may bring some morning rain to the forecast area. The front will largely stall out over Lakes Michigan and Erie and temperatures for much of the forecast area will surge into the 60s and 70s this afternoon. When combined with dew points in the mid to upper 50s, instability should be able to build considerably with 1000-1500 J/kg of MLCAPE over northern Ohio. Behind the front, a strong 50 kt 850 mb low level jet will also enter the region and allow for wind shear to increase with 0-6 km bulk shear values in the 50 to 60 kt range and 0-3 km SRH values of 200-300 m2/s2, suggesting some more organized low-level wind shear. Overall, many of the ingredients will be coming together to support a severe weather threat across the forecast area.

For the first window this afternoon from 1 to 4 PM in NE Ohio and NW PA, the convection will be specifically tied to the warm front. As the warm front progresses through the forecast area this morning, much of the convection will be elevated and may not amount to more than a scattered rain chance. However, by afternoon, there may be potential for some this convection try to become more surface-based and intensify into an organized severe weather threat. The dynamic environment along and ahead of the warm front will be fairly favorable for any surface based storms that do end up developing. There will be very favorable wind shear with the warm front advancing from the southwest, the westerly low level jet, and the northwesterly upper level flow and it would be possible that surface-based storms would be supercells with the potential for large hail, damaging winds, and even a tornado. While concerning, the threat is both conditional and a very short window, as the warm front surges toward Lake Erie. It is possible that some of the elevated convection that will move through this morning will work over the atmosphere just enough to prevent these stronger, surface-based storms. In addition, the entire system continues to trend just a touch faster with each model cycle and that could also indicate that the front could reach Lake Erie before initiating new convection over the region. In the end, there is plenty of conditionality to this setup, but if it materializes, there would be a couple sneaky severe storms ahead of the main show below.

The main show with the Enhanced Risk will be from late afternoon onward, as the warm front will be pushed back south as a cold front and initiate widespread showers and thunderstorms across northern Ohio. These new thunderstorms will take advantage of a relatively favorable atmosphere, as described above, and present a severe threat to much of the forecast area. For this window, the main storm mode will likely be linear with a touch less shear south of the frontal boundary. This line of storms will push east-southeast, moving parallel to the boundary through the evening hours. The main threat with this line will be damaging wind gusts. However, the increasing low level jet during the evening hours will enhance the low level shear once again and QLCS tornadoes will be possible within the line. The severe threat should be south of the forecast area after Midnight.

With showers and thunderstorms moving parallel to the frontal boundary and precipitable water values approaching 1.5", storms will produce efficient rainfall and train over the same areas this evening. There may be some locally heavy rainfall and isolated flooding, but flash flood guidance remains somewhat high for late March near 2 inches. In addition, storms will be moving quickly, given the strong flow aloft, and flooding does not appear to be as high as a concern as other severe weather hazards at this time.

KEY MESSAGE 2... High pressure will build south across the region on Friday behind the cold front from this evening's severe weather event. Temperatures will fall back below normal with highs in the 30s and 40s on Friday and 40s on Saturday. High pressure will allow for dry conditions.

For Sunday, the high pressure system will push east and allow for another warm front to enter the region, allowing temperatures to return to the 50s. The warmer air will continue to build on Monday with moist, return flow entering into the region. Rain chances will start again on Monday with daily rain chances expected. The best opportunities for rain at this time would be Tuesday with a reinforcing warm front and Wednesday with a cold front.

AVIATION /18Z Thursday THROUGH Tuesday/

VFR conditions are seen across much of the region currently. There is a cloud deck around 030-050 across central to northern Ohio periodically dropping down to MVFR conditions that will be moving to the east through this afternoon. The main impacts this TAF period will be the severe weather threat this evening bringing the potential for strong wind gusts up to 65 knots and damaging hail. Guidance on the timing of the thunderstorms has slowed down when it will enter the region from the north-northwest and will begin around 20-22Z for the most northern terminals at KTOL, KCLE, and KERI. It will exit to the south-southeast by 02-03Z. The line will bring heavy rainfall at times that could drop conditions down to IFR to LIFR. The thunderstorm potential could last for a few hours after initiation before moving to the southeast. Behind frontal passage, lingering rain showers are expected to persist for a few hours into the early morning tomorrow keeping conditions down to MVFR/IFR. The widespread rain showers will move out of the region starting around 08Z for the northern sites and 12Z for sites to the south. Non-VFR ceilings are expected to continue for most sites through mid-day tomorrow when ceilings begin to rise.

Winds across the region are currently out of the southwest gusting to 20-30 knots. They will slowly veer to be more west-southwesterly through the early evening before shifting to be out of the north with frontal passage. Winds will increase ahead of the front, gusting up to 35 knots with stronger gusts likely within the thunderstorms with gusts up to 65 knots possible. The stronger winds will generally be out of the west, but erratic gusts associated with the thunderstorms are possible. Behind the front, as winds shift to be northerly, they will diminish to around 10 knots sustained, gusting to around 20 knots and will continue through the remainder of the TAF period.

Outlook...Non-VFR ceilings expected through Friday afternoon with periodic rain showers possible in the morning. Non-VFR possible on Monday with rain showers/thunderstorms.

MARINE

A Small Craft Advisory has been issued for these nearshore U.S. waters:

- Reno Beach to Willowick from 11 PM EDT today to 4 PM Friday - Willowick to Conneaut from 2 AM to 4 PM Friday

Primarily S'erly to SW'erly winds around 10 to 15 knots are expected through most of this afternoon as a high pressure ridge exits slowly SE'ward. Waves remain 3 feet or less. A strong cold front should sweep SSE'ward across Lake Erie late this afternoon through early evening and cause SW'erly winds to veer quickly to N'erly to NE'erly and freshen to around 10 to 20 knots through the remainder of this evening as waves build toward 2 to 5 feet. Behind the front, a strong high pressure ridge builds from the northern Great Plains and vicinity through Friday and will cause winds to vary between NW'erly and NE'erly. Initial wind speeds around 15 to 25 knots should ease gradually to 5 to 15 knots by midnight Friday night. Waves initially as large as 3 to 6 feet should subside to 3 feet or less by midnight Friday night.

On Saturday through Sunday, the ridge should continue to impact Lake Erie as the embedded high pressure center moves from the Upper MS Valley toward VA and vicinity. This will allow a warm front to drift generally N'ward across Lake Erie Saturday night. Accordingly, winds around 5 to 15 knots should back gradually from N'erly to SW'erly to S'erly. Waves should remain 3 feet or less. On Monday, the ridge should exit SE'ward as a cold front eventually settles SE'ward over Lake Erie. The cold front passage should cause S'erly to SW'erly winds around 10 to 20 knots to veer to N'erly. Waves should be mainly 3 feet or less, but occasional 4 to 5 footers are forecast currently. We will continue to monitor Monday's forecast for the potential need for another Small Craft Advisory.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...Small Craft Advisory from 11 PM this evening to 4 PM EDT Friday for LEZ143>146. Small Craft Advisory from 2 AM to 4 PM EDT Friday for LEZ147- 148.