The talk in the weather-land is what will happen with an extended period of overrunning evolving midweek as a cold front slides slowly southeast and stalls over the Northern Ohio Valley. First let me say; this is not a typical low pressure system developing in the Ohio Valley, deepening and moving northeast into the Eastern Lakes and out of the area. True; heavy amounts of snow usually are associated with that system but its affect is shorter-lived, usually about 12-18 hours depending on movement. If the system gets "stacked" all levels of the atmosphere as it matures, it can hold longer. That usually happens in the Northern Lakes, Canada or Northeast.
Overrunning in a "Sling-Shot" Fashion
What
is expected to happen this week is the cold front moves down into the
Ohio Valley back into the southern Midwest and stalls. In the meantime;
weak waves of low pressure and extensive overrunning occurs in and
southwest to northeast trajectory as the front gets hung up and becomes
parallel to this basic "sling-shot" pattern. Energy in the upper levels
of the atmosphere are forecast to stream out from the South-Southwest
Region to the Northern Ohio Valley. Years ago in my early days I learned
about this "Sling Shot" pattern from a few of the Old Timer Forecasters
when a upper air trough formed over the Southwest in the Arizona/New
Mexico and energy ejects and streams northeast into the Great Lakes/Ohio
Valley. When copious moisture was available for a longer term stalled
system, I can hear the phase "Someone's gonna' get Clobbered"
back in the old days from a revered forecaster back in his day: Frank
Grabowski of Livonia (I assume he since has passed away, he would be
around 100). I always looked forward working with him as he was smart,
good intuition, loved electronics, down to earth and sometimes
unintentionally; humorous, one of my favorite forecasters - but I
intentionally digress.
As cold Polar or Arctic air hovers over the Northern Plains and Great Lakes while milder air, sometimes with copious moisture, streams over the stationary front that forms at the surface and aloft; then causes precipitation mainly north of the front into the colder air as light to heavy light snow (depending on moisture that is available) many times from the Gulf of Mexico. The forecasters can be leery of this setup because it can last for long periods and what falls can be damaging; especially freezing rain as the cold air hugs the ground and above freezing air flows up in the atmosphere and liquid precipitation accumulates on the ground as ice. Forecasters can also be leery for another reason when this pattern was forecast; WHO will get clobbered? It's very easy to miss on this forecast because as we know, the atmosphere sometimes doesn't do what our models suggest. That is why it's better to step into this forecasted pattern (and various outcomes have already come up with different models) slowly and not be too extreme days ahead. Thus a Winter Storm Watch was issued by the NWSDTX today - and one of the reasons it was developed decades ago.
Ok; so what are we in Southeast Lower Michigan looking at with this winter system? Well; I've pretty much explained the pattern expected so lets look at the model projections. As you will see there is a wide ranging snowfall amounts expected just in our region, alone. The important thing is this latest run, the models are coming more inline; especially our big ones GFS & Euro with NAM and Canadian joining the pack, Both Euro and Canadian have come more inline with GFS. All models are from 12Z /7am est/ Mon 1/31 except NAM which is the later run at 18Z. Also Euro snowfall is the standard 10/1 ratio. Snowfalls are expected to sharply fall off into the northern areas of Southeast Michigan.7Am Update, Wed- 2/1/22 (Forecast section) Previous thinking of second wave of Low Pressure just clipping the SE corner /Ann Arbor to Metro Detroit, south/ still looks likely . A slower change-over to snow overnight due to warmer column of air before the change over - and break in the action overnight Thursday will cut in snowfall amounts somewhat across mainly the southern region. Forecast wording and snowfalls lowered for ranges. Snow, moderate to heavy at times is expected today with a lull in the action overnight. Snow picks up again across extreme SE Mich Thursday diminishing off to flurries Thursday evening.
Snowfalls -
1-Ohio border north through Adrian and Monroe to I-94 corridor; Total snow accumulations 9 - 14" with isolated pockets of higher totals possible.
2-Ann
Arbor into Detroit /north of I-94 to I-696 region/ including Detroit's
immediate northern suburbs into Lake St Clair communities; 8 - 12” with isolated pockets of higher totals possible.
3-
Further north extending from northern areas of 2, up into the Flint
area across I-69 corridor through Lapeer into Port Huron and Southern
Lake Huron communities; 6 - 10".
Bill Deedler - SEMI_WeatherHistorian
