textproduct: Cleveland

WHAT HAS CHANGED

The forecast has changed little. A few severe thunderstorms with damaging hail are possible in our region late this morning through early evening, especially from roughly the latitude of Cleveland and points south. Damaging wind gusts are also possible from a few severe thunderstorms this afternoon through early evening, especially roughly along and south of U.S. Route 30.

KEY MESSAGES

1.) Unusually-warm temperatures precede a strong cold front passage today. A few severe thunderstorms are possible along and ahead of the cold front, especially this afternoon through early evening.

2.) Variable air temperatures are expected tonight through Sunday, March 29th. Periods of precipitation are expected tonight and again Wednesday night through Friday.

DISCUSSION

KEY MESSAGE 1... Cyclonic W'erly to NW'erly flow aloft and embedded shortwave troughs affect our region today. At the surface, a low wobbles ESE'ward from Lower MI and southern ON to near southern New England by sunset this evening. This low track will allow the trailing surface cold front to sweep SE'ward through our CWA during the mid-morning through late afternoon hours. Peeks of sunshine and daytime heating, low-level WAA, and appreciable low-level moisture advection from the Gulf are still expected to allow highs to reach mainly the 60's to 70's ahead of the front. The same processes should allow weak to moderate boundary layer CAPE and steep low-level lapse rates/moderate DCAPE to materialize in the warm sector, especially roughly along and south of U.S. Route 30, where longer residence time in the warm sector and greater diurnal heating are expected. Low-level convergence/moist ascent along the cold front and any downshear outflow boundaries are expected to trigger isolated to scattered showers and thunderstorms along and ahead of the surface front. Moderate to strong effective bulk shear will allow storms to be organized (i.e. organize into multicells and supercells). The thermodynamic and kinematic environment in the warm sector should allow a few storms to become severe with damaging straight-line wind gusts. For several hours following the surface cold front passage, moist isentropic ascent along the upper-reaches of the cold front should release weak to borderline moderate and elevated CAPE amidst continued moderate to strong effective bulk shear, which should result in the development of isolated to scattered, organized, and elevated showers and thunderstorms. Small to damaging hail remains a concern with surface-based storms along and ahead of the surface cold front, and elevated storms along the upper-reaches of the front due to steep mid-level lapse rates associated with an EML plume, which should contribute to large MUCAPE in the hail growth zone. Some forecast model soundings, when compared to the SARS (Sounding Analog Retrieval System), suggest severe hail up to 2" in diameter is not out of the question with any discrete supercells that manage to develop in roughly the Knox County to Mahoning County corridor in our CWA. Note: based on the expected evolution of MUCAPE, including within the hail growth zone, the greater potential for severe hail exists along and roughly south of the latitude of Cleveland. However, isolated instances of marginally-severe hail are possible farther north in our CWA.

KEY MESSAGE 2... Cyclonic W'erly to NW'erly flow aloft and a stronger embedded shortwave trough will impact our region tonight as a surface ridge builds slowly from the north-central United States. Additional periods of rain are expected via moist isentropic ascent along the upper-reaches of the cold front and ahead of the shortwave trough axis. This rain should end from northwest to southeast between roughly 9 PM this evening and 1 AM Monday based on expected evolution of the cold front passage and stabilizing subsidence accompanying the surface ridge. It now appears rain will end before having the chance to mix with or change to snow via sufficient CAA at the surface and aloft. Lows should reach the upper 20's to mid 30's around daybreak Monday.

Current odds favor dry weather in our CWA this Monday through Wednesday as a ridge at the surface and aloft builds from the north-central United States and vicinity through Monday night and then begins to exit slowly E'ward on Tuesday through Wednesday. As the ridge exits E'ward, a warm front should sweep N'ward through our region on Tuesday. Despite moist isentropic ascent along the upper-reaches of the front, any resulting precip should be in the form of virga due to a dry low-level atmospheric column in the cold sector. Continued CAA at the surface and aloft should be accompanied by highs reaching the mid 30's to 40F in NW PA and the upper 30's to mid 40's in northern OH Monday afternoon. Overnight lows should reach the lower 20's to lower 30's around daybreak Tuesday. WAA at the surface and aloft develops across our region, ahead of and behind the surface warm front, on Tuesday through Wednesday. Afternoon highs should reach the 40's to mid 50's Tuesday and mainly the 50's on Wednesday. In between, overnight lows should reach the 30's Tuesday night.

During Wednesday night through Friday, cyclonic W'erly to NW'erly flow aloft and embedded shortwave troughs should impact our region. The aforementioned surface ridge should continue to exit slowly E'ward before a cold front sweeps SE'ward across our region late Thursday. Behind the front, another surface ridge should build from the north-central United States. Periods of precip, mainly in the form of rain, are expected due to the following: moist isentropic ascent ahead of shortwave trough axes and along the upper-reaches of the front; low-level convergence/moist ascent along the surface cold front. Above- normal lows and highs are expected in the warm sector Wednesday night and Thursday, respectively. Behind the cold front, near to below-normal lows and below-normal highs are expected Thursday night and Friday, respectively, amidst low-level CAA.

During Friday night through this upcoming weekend, the above- mentioned ridge at the surface and aloft should build from the west and eventually crest E'ward over our region. On the backside of the ridge, another warm front should sweep N'ward through our region Friday night into Saturday. Latest trends in NBM forecast guidance suggest this front passage will be dry for the same reasons as Tuesday's warm front passage. An overall warming trend in air temperatures is forecast Friday night through Sunday due to the eventual development of low-level WAA, ahead of and behind the surface warm front.

AVIATION /06Z Sunday THROUGH Thursday/

LLWS overnight before mixing occurs and can get gusts to the surface Sunday. Cold front will sink southward sparking showers and thunderstorms across the region, likely in two different waves, generally after 17Z. The thunder aspect of this forecast is particularly tricky, and have opted for this issuance with a more conservative forecast and covering it mostly with SHRA. This may be altered for the 12Z set that goes out later this morning. Behind the cold front as it sinks southward, the ceilings should drop to MVFR and eventually IFR after 00Z.

Outlook...Non-VFR in stratus and perhaps a few lake effect flurries or snow showers continues Sunday night into Monday, with high pressure bringing improving conditions late Monday.

MARINE

A cold front dropping across Lake Erie from north to south today will brings a wind shift to the north later this afternoon through tonight 15-25kts. Due to the due north orientation of this wind, wave heights will briefly approach Small Craft Advisory criteria for the western and portions of the central basin of the lake. Looking at wave heights 3-4ft for these areas, generally limited to the late evening and overnight time frame. Into Monday, winds turn northwesterly, but decrease to 10-20kts and wave heights down to 2-4ft. Winds become offshore Tuesday with high pressure moving east of Lake Erie and wave heights less than a foot, becoming easterly Wednesday around 10-15kts and wave heights in the western basin increasing to 1-3ft.

CLE WATCHES/WARNINGS/ADVISORIES

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