March 13-15 Ohio Snow Discussion

Here is my “abbreviated” write-up regarding the upcoming snow event to northern Ohio…

There was a definitely a reduction in QPF on the overnight/early morning models.  We’ll see if that trend continues and how it affects snow totals…

For the synoptic snow late this afternoon through early Tuesday the models are generally showing 0.25 to 0.40″ of QPF across the Cleveland/Akron areas with perhaps a tad more in far NE OH.  This will still be a long duration synoptic snow event as the 850mb and 700mb lows track right across northern OH between this evening and Tuesday morning keeping relatively modest large scale lift going from late this afternoon through early Tuesday.  We will see several hours of isentropic lift/mid-level warm air advection starting late this afternoon leading to what will likely be mainly light snow ahead of the mid-level low followed by getting into a relatively weak deformation zone late tonight through Tuesday morning, which should also keep light snow going.  With a shallow unstable layer over the lake and frictional convergence along the western shore with a ENE to NE flow after midnight tonight some lake enhancement could occur there overnight and allow for totals to be an inch or two higher than they would otherwise be.  Snow ratios could actually start out fairly high late this afternoon into early this evening as the best lift is focused in the mid-levels in the DGZ, though the flakes could get pretty small overnight as the best lift is focused below the DGZ.  Ratios should improve again early Tuesday as the low levels begin to cool, expanding the bottom of the DGZ quite a bit.  This improvement in ratios may align with the weak deformation zone along with some lake enhancement swinging through Cleveland/Akron and the snowbelt late tonight into early Tuesday.  Given all of this, average ratios of around 13-15:1 seem likely tonight which when combined with the model QPF suggests 3-6″ of widespread snow across the northern couple tiers of counties in north-central and NE OH.  NW OH will not see as proglonged of a period of modest lift tonight so they may see more like 2 to locally 4″.  Given the best large scale lift will be east of the western lakeshore, I think even with lake enhancement they should stay in the 3-6″ range through early Tuesday.  Because the deformation zone appears fairly weak and because lake induced instability won’t quite develop until later Tuesday morning, I don’t expect widespread 6″+ totals across the Cleveland area or snowbelt through early Tuesday, but some of the higher terrain could be pushing 6″ if everything goes well.

As the mid-level lows go by Tuesday morning the low-level flow will gradually come around to the NNW and a deepening layer of instability will develop in the low levels over the lake which should allow lake enhancement and orographic lift to really ramp up by later Tuesday morning.  Synoptic snow should be rather light by this point, though with some mid-level frontogenesis as a steep 700mb temp gradient moves overhead on the backside of the 700mb low along with vorticity advection and mid-level height falls ahead of the approaching closed 500mb low there will be some large scale lift present which should keep some light synoptic snow going Tuesday morning into the early afternoon.  This weak synoptic snow combined with improving lake induced instability and terrain enhancement should allow widespread light to moderate snow to continue downwind of the lake through Tuesday afternoon.  Ratios should remain OK as the DGZ lowers into the low levels where the best lift with the lake and terrain enhancement will be.  These factors should allow another 2-3″ of snow to fall during the day Tuesday, particularly in the higher terrain, with perhaps only an inch near the immediate shore and well inland.  Far NE OH could see 3-4″ during the day Tuesday as better snow will linger a bit longer there into Tuesday morning…pushing totals thus far to 5-9″ in the higher terrain through Tuesday afternoon and 4-7″ elsewhere.

As we head into Tuesday evening lake effect conditions improve more with equilibrium levels rising to 10k feet for much of the night with good moisture to over 10k feet as well.  One concern is a somewhat strong and sheered flow beneath the equilibrium level possibly hurting band organization.  With that said the thermodynamic profile will be quite favorable for good snow downwind of the lake and several vort maxes with the closed 500mb low will move overhead, adding some large scale lift and possibly enhancing the lake effect snow.  Snow ratios will be high with any lake effect snow that occurs.  I suspect either higher terrain or an upstream connection will be needed to get notable additional accumulations with the lake effect Tuesday night into Wednesday with the short fetch and somewhat stronger/sheered flow.  With some large scale lift I think even the shore sees at least another inch or two Tuesday night into Wednesday, but could struggle to see more.  The higher terrain should see at least a general 2-4″ Tuesday night through Wednesday morning given the prolonged favorable upslope flow, thermodynamic environment, and periods of better large scale lift with vort maxes rotating overhead.  The key to getting significant lake effect given the short fetch and stronger than perfect winds/sheer in the low levels will be upstream connections to Lake Huron.  The models initially have this connection going into the west side early Tuesday evening before gradually swinging to central Cuyahoga and Summit Counties and points east overnight.  With a NNW flow I’d expect this connection to be more persistent east of Cleveland and into western Lake/Geauga/Portage Counties.  Snow rates of 1-2″ per hour could occur with any band with an upstream connection that forms, so 3-7″ of additional snow seems possible wherever this connection sets up…likely a bit east of Cleveland proper.

The large scale lift ends Wednesday morning as the closed 500mb low moves away and mid-levels really dry out.  The low levels remain pretty unstable so LES snow showers with a little additional snow will continue through the day, but additional amounts after 8am Wednesday should largely be 2″ or less and confined to the higher terrain.  All of this adds up to totals near the shore of 5-9″…most likely in the lower half of that, but if some better lake enhancement occurs or if a Huron band affects certain areas the upper half is possible…and a general 8-13″ in the higher terrain just inland from southern Lorain County east through the secondary and primary snowbelt.  Locations that see the better lake effect likely with the potential Huron connection will see totals of 10-16″ in the higher terrain.  NW PA should see a more prolonged period of synoptic snow and better terrain enhancement, so should see 6-10″ near the lakeshore and a widespread 10-18″ inland.


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