Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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857 FXUS61 KCLE 130822 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 422 AM EDT Sat Jul 13 2024 .SYNOPSIS... High pressure remains in control of the local weather through tonight. A warm front lifts across the area on Sunday before stalling across the central Great Lakes region on Monday and Tuesday. The front will move southeast across the area as a cold front Tuesday night or early Wednesday. && .NEAR TERM /THROUGH SUNDAY/... Warm and mainly dry weather is in store for today with weak surface high pressure in control. Patchy fog is developing across a few valleys early this morning but will quickly mix out after sunrise. Water vapor imagery reveals a weak vort max over southern Lake Michigan that should move through this afternoon. Very modest ascent ahead of this feature should combine with the development of weak to moderate and uncapped instability to yield a cumulus field and at least a few attempts at showers or storms this afternoon or early evening. The greatest potential for activity to pop will be along a lake breeze that will push inland this afternoon, though hilltop convergence may contribute as well. The minimal forcing, a warm layer around 600mb and dry mid-levels will be limiting factors for shower/storm development today though most hi-res models manage to develop at least isolated activity. Given this, maintain the slight chance (20%) POPs that we`ve been carrying in the forecast away from the lakeshore and a smaller area of chance (30%) POPs from approximately a Medina to Millersburg line points east-northeast across the Youngstown and Warren area. Highs today will generally reach the mid to upper 80s with dew points in the mid to upper 60s. Given steep lapse rates above 600mb, long/straight hodographs in the hail growth zone, large amounts of DCAPE and steep low-level lapse rates there is a low but non-zero pulse severe concern (marginal hail/downbursts) if one or two cells are able to punch through the mid-level warm layer and develop stronger cores aloft. It seems more likely that the warm/dry mid-levels and minimal forcing keep any cells too weak to realize this potential, though some hi-res models such as the 0z 3km NAM and RRFS do have a couple of more robust cells that could realize such potential. Something small for us to watch for. Quiet weather is expected tonight with lows generally ranging from the mid 60s to near 70, though some rural valleys from far Northeast OH into Northwest PA may get slightly cooler. Patchy fog is possible again late tonight, though with a weak wind developing fog should generally be limited to valleys in far Northeast Ohio and Northwest Pennsylvania. Sunday will begin a stretch of more active weather, with generally low predictability of timing/magnitude of rain and thunderstorm chances due to dependence on upstream convective evolution over the Upper Midwest and western Great Lakes. Guidance agrees on a shortwave approaching from the northwest Sunday morning and moving through Sunday afternoon. Where guidance disagrees is on whether or not some form of decaying MCS will accompany this shortwave. Many models show any MCS falling apart before moving in on Sunday, though some (such as the 6z run of the HRRR) maintain an MCS through much of our area Sunday morning/early afternoon. MCS/s have a habit of occasionally propagating faster and dissipating a bit slower than models suggest, so do have POPs spreading in from the northwest Sunday morning/early afternoon. If the MCS falls apart before making it in or doesn`t arrive until Sunday afternoon, renewed development or re-intensification would be possible in the afternoon with a modest severe potential given some increase in instability and shear Sunday afternoon. However, if the MCS is faster/more robust (such as the aforementioned 6z HRRR) we`d likely see showers/thunder during the morning and early afternoon with minimal to no severe risk given a generally stable/dry environment overhead Sunday morning. This solution would leave us with a worked over atmosphere, limiting any afternoon convection. All this to say that we have broad 30-50% chance POPs spreading in from the northwest beginning Sunday morning and continuing through the afternoon. Lowered highs on Sunday just a bit given potential for clouds/precip, though still range from the upper 80s to lower 90s. The POP, QPF, sky, and temperature/heat index forecasts Sunday remain subject to further adjustment and a window of higher POPs may be needed. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... On the synoptic scale, northwest flow continues aloft, with surface high pressure centered over southern Appalachia, and generally across much of the southeast CONUS through Monday, before this high departs to the east over the Atlantic. Broadly, this pattern will consist of heat and humidity, with thunderstorm chances in each period. Getting into the details, most models have a convectively-induced shortwave trough overhead with a thunderstorm complex exiting the area at the start of the short term period Sunday night. Most models have another convective complex developing upstream and then moving across the area again very late Sunday night into Monday morning. A lot of these features are being driven on the mesoscale however, so very low confidence in this exact setup/scenario because these small things can change very easily this far out. We`ll have to pay attention to the mesoscale details upstream over the next couple days, which can hint at how the forecast could change. Generally though, the environment will be favorable for severe weather, particularly damaging winds as surface dew points in the low 70s and mid-level lapse rates of 6.5-7 C/km result in moderate instability. Deep layer shear is uncertain, but is in the 20-30 knot range, which is marginal but sufficient for severe weather, especially if there is greater instability. By Monday, uncertainty increases as we continue to depend on mesoscale features to drive the forecast. Still though, the general environment will be favorable for severe thunderstorms and instability is actually expected to increase by Monday. CSU-ML has its max severe weather probabilities on Monday (15% for entire area and 30% probabilities touching Northwest Ohio), driven completely by it`s wind probability forecast. Heat and humidity is expected to peak Monday, with heat indices in the mid to upper 90s areawide, with some spots along and west of I-77 touching 100. It`s possible we may need a heat advisory but this is highly dependent on the precipitation forecast. By Tuesday, a broad upper-level trough and associated surface cold front approaches the Great Lakes region from the northwest, providing some synoptic-scale forcing and greater confidence in thunderstorm development. Have highest PoPs of the short term period Tuesday through late Tuesday night with most of the forecast area up into the 60-70% range. Severe thunderstorm will be possible again Tuesday and Tuesday night. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... The cold front is expected to cross the region late Tuesday night into Wednesday morning, ushering in a pattern change to the region as the high pressure building in will be accompanied by a cooler and drier airmass. Afternoon temperatures in the upper 70s to low 80s are expected Wednesday through Friday with no precipitation expected (outside Wednesday when some lingering showers and thunderstorms will be possible). && .AVIATION /06Z Saturday THROUGH Wednesday/... Patchy fog is beginning to develop early this morning. Not expecting widespread dense fog, though a few terminals may see a couple or few hours of restrictions. Any fog/mist will mix out by 12 or 13z. Isolated to widely scattered showers and thunder will attempt to develop this afternoon away from the Lake Erie shoreline. Coverage will be low and any thunder or restrictions will be very hit or miss, so just maintained a VCSH mention at a few sites. If confidence in thunder or restrictions increases we may add at a site or two in future cycles. Like Saturday, any activity should dissipate by 0z this evening. Winds through the period will be light - largely variable through morning and favoring north to northwest for Saturday afternoon. Outlook...Periodic rounds of showers and thunderstorms with non-VFR may be possible this Sunday through Tuesday. && .MARINE... Quiet conditions are expected today and tonight as high pressure remains over the area, with a weak afternoon lake breeze. As high pressure departs to the southeast, southwest winds in the 10 to 20 knot range develops on Sunday, lasting through at least Tuesday evening. Speeds will be variable, with any 20 knots winds expected to be brief, although can`t necessarily rule out the need for any short small craft advisories and any point this week. A cold front moves southeast across the lake Tuesday night with winds veering to out of the northwest and north Wednesday through Thursday. Current indications suggest these winds should hold under 20 knots, but onshore flow will certainly make it choppy despite the otherwise nice weather these days. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Sullivan NEAR TERM...Sullivan SHORT TERM...Saunders LONG TERM...Saunders AVIATION...Sullivan MARINE...Saunders