Wintery Mixed Precipitation to Accompany Warm Air Advection Wednesday

Epilogue:
System behaved itself with generally light amounts of snow and sleet reported over northern areas of Southeast Lower Michigan; and a bit of snow with more sleet and freezing rain central and southern areas. Most of the freezing rain was over central areas of the region with ice totals remaining below a 1/4".

http://forecast.weather.gov/product.php?site=DTX&issuedby=DTX&product=LSR&format=CI&version=2&glossary=0

http://forecast.weather.gov/product.php?site=DTX&issuedby=DTX&product=LSR&format=CI&version=1&glossary=0

blog:

At this time, it looks as though central and northern Southeast Lower Michigan...or a line roughly from north of Ann Arbor into Detroit's northern suburbs and areas northward...could see the longest period of mixed precipitation before the changeover. While light amounts of snow, sleet and freezing rain are expected, the sleet and freezing rain will be most problematic with ice amounts less than 1/4" in freezing rain areas. 

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Initial blog below:

Look for weather conditions to deteriorate after midnight during the early morning hours of Wednesday /29th/ as strong warm air advection aloft pushes into Southern Lower Michigan. This increasingly moisture-laden warmer air will trigger snow, then sleet and freezing rain as it rides over the colder air at and just above the ground. The storm center bringing the snow, sleet and freezing rain will move west of the region over southern Minnesota but will act as a pin-wheel; advecting the warmer, moist air into the region from the south. Blizzard conditions are expected out over the Upper Midwest with heavy snow into the Northern Lakes with this storm.

Much of the mixed precipitation should fall from the early morning hours into the forenoon hours of Wednesday as it moves in from the south and works its was north. The mixed precipitation will change to light rain, drizzle with just cloudy conditions thereafter in the afternoon.  In addition, a moderate east to southeast wind will accompany the event. While there will be strong warmer air riding aloft; indications are the colder air near the surface will begrudgingly give way over portions of Southeast Lower Michigan. At this time, it looks as though central and northern Southeast Lower Michigan...or a line roughly from north of Ann Arbor into Detroit's northern suburbs and areas northward...could see the longest period of mixed precipitation before the changeover. While light amounts of snow, sleet and freezing rain are expected, the sleet and freezing rain will be most problematic with ice amounts less than 1/4" in freezing rain areas. However; this is subject to change if more moisture works in or change-over is delayed.

A sharp temperature-gradient will form over Southeast Lower Michigan on Wednesday with readings rising into at least the 40s behind the surface warm front, while hovering in the lower to mid 30s ahead of it. Look for the warmer air to overtake the entire region during the after as readings rise into the 40s, to around 50 in the south. Then; look for colder air and snow showers to move back into the region Wednesday night.

Motorists be advised driving conditions will deteriorate rapidly as the mixed precipitation encompasses Southeast Lower Michigan during the early morning hours while temperatures are at/or below freezing.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian

Review of Winter Storm: February 23-24th, 2012

Epilogue 2/23-2/24/12 Storm:

Thursday 2/23 model runs on the system pivoted the storm further south than my initial projection across Northern Indiana and Northern Ohio.  In accordance; I raised snowfalls to 4" - 8" rather than the 2"- 4" with pockets of 3" - 6" forecast a day earlier on Wednesday. In retrospect, the low tracked closer to my original thinking; south of Tuesday's model projections over Illinois/Indiana but wound up further north of Thursday's model projections, over the corner of Southeast Lower Michigan early Friday. Just as important however, was the track of the upper air support which /vorticity max/ which tracked right across Southeast Lower Michigan. This was northwest of the surface low and provided maximum lift and dynamics for the system. Heaviest snow generally falls to the left (or north-northwest) of the vorticity center which was across Saginaw Valley into the Thumb (where 3" - 5" of snow with maximum pockets of 6" was observed). Heavier amounts were observed further northwest into central and northern Michigan.             
                                                      Snowfall Amounts & Map from DTX

What was learned in this event?

Just because they are the latest model runs (versions); doesn't mean they are the most accurate. Sometimes your earlier and initial analysis on a snow forecast is the better one and you must have faith to stick with it; even in the face of "model contrariness". On that premise, I failed by changing my original snowfall amounts Thursday. On the positive: I alerted the public of a storm that would impact Southeast Lower Michigan and the Great Lakes days ahead of the storm. The storm did develop and affected residents of Southeast Lower Michigan; in a winter that has been virtually "stormless"; see initial 2/21/12 blog below. 
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Blog: 2/23
Latest indications continue to show the winter storm first written about here on Tuesday will indeed affect all of Southeast Lower Michigan as she tracks eastward and then northeastward through the Northern Ohio Valley. Nearly all the models now paint an intensifying cyclone, shifting from southern Indiana northeast through central Ohio and then toward the Cleveland area by Friday afternoon. This more southerly track is in accord with earlier thinking and then some with the track now proficient for the likelihood of heavy snow across much of Southeast Lower Michigan.

While the track will be south of Southeast Lower Michigan, enough warm air will be drawn up ahead of the system to bring rain or rain mixed with snow up into the region toward sunset across the far south and this will move northeast;  encompassing all of Southeast Lower Michigan during the evening hours. Much of Southeast Lower Michigan should receive 4" to 8" of snow with this system with the highest amounts likely north of I-94. Heaviest snow inducing lower visibilities should occur toward the midnight hour and continue through the early morning hours.

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Earlier blog 2/22/12 of model and my positions:

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Initial Blog: 2/21

Latest model trends are converging on an intensifying Eastern Great Lakes low pressure system late Thursday into Friday. This system will be brought about as strong Pacific energy aloft aligns with/and phases with Polar energy diving in from central Canada.

On to the particulars; Strong energy aloft at varying levels is projected to dive east southeast from the Pacific into the Midwest by late Thursday. At the 250 MB /35,000 Ft/, the core wind max is expected to be at least around 130 knots! This upper level energy will proceed generally east and align itself along a potent stationary frontal boundary that will form and extend from the southern Great Lakes east into Pennsylvania and then, off the East Coast. At this time it looks a though a few waves of low pressure will be induced along the front while rippling east with time. As this scenario becomes more established across the southern Great Lakes and northern Ohio Valley; additional moisture will be drawn northward from the Ohio Valley and then subsequently, westward from the Atlantic. This moisture, in conjunction with the strong upper level dynamics and surface boundary, will be aiding and a betting with the development of the main Eastern Great Lakes cyclone or low pressure system by Friday. How quickly this above scenario takes place will have a lot to do with the final outcome of the weather to affect Southeast Lower Michigan.

On the projected 7 pm Thursday weather maps below; 

Map 1 from the GFS model denotes the 250 MB wind jet at 35,000 feet and speeds. The first jet core /1/ will help with the initial development of our frontal boundary and low pressure system as phasing commences; while the second jet core /2/ comes in from the rear to deepen and intensify the system during the day Friday. The second GFS map places the main developing low pressure near the tri-state area of Michigan-Indiana-Ohio also at 7pm Thursday. I feel the GFS may be too far north with the main surface low and its track could be further to the south; over the northern half of Indiana and Ohio rather than the border area.

                                                                          Map - 1

                                                                              Map - 2

Of course, this a projection of a few days out and therefore will be attentively watched and analyzed as updates from various models zero in on this system. Not only do the usual problematic winter storm specifics apply here; such as track and available moisture but also the temperatures in the lower levels of the atmosphere and surface which will dictate initially the amount of rain and snow and later, potential snow accumulation. At this time is does look as though the worst of the system will be east of Southeast Lower Michigan but it still bears watching, so stay tuned.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian

Another Arctic Air Pest To Visit For The Weekend / Epilogue-2-11-12/

The Forecast:

"The very latest indications are enough moisture will be transported into Southeast Michigan as a weak wave of low pressure transverses the front (see second map) to bring 1 to possibly 3 inches of snow across the region. Gusty north winds and falling temperatures later on Friday will exacerbate driving problems. Motorists driving Friday up through Michigan should be prepared for this winter weather and any subsequent lake effect snows with higher amounts."

Epilogue: System was a bit of a overachiever as she wound up in the eastern lakes feeding on the better moisture as the Arctic cold wrung out the moisture. Generally; a one notch higher 2-4" category would have been the most accurate call (some isld 5"s ). Overall, my Friday AM forecast did indicate the stronger trends, along with the timing and driving conditions being spot on. Enjoy the winter wonderland this weekend; now on to the next challenge.....

recent snow amounts /per NWS/
Snow map

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 Previous blog:
In a winter where true Arctic air infiltrations (a.k.a. pests this winter ;-)) have been as rare as its snowstorms, an impressive plunge of Arctic air will again be our weekend guest, arriving this Friday. Ironically, it was exactly a month ago in January on Friday the 13th, when the first in a series of Arctic waves surged south into the Great Lakes. In any other winter, these plunges of Arctic air and resulting temperatures would not be very noteworthy but given the extraordinary mild winter thus far, they are and it will be noticed! High temperatures will actually drop to below normal levels for a couple of days in the teens and 20s. Normally as we move into the second week of February, our highs across Southeast Lower Michigan average in the 30 to 35 degree range while lows place between 15 to 20.  

                                                   250 MB Upper Jet

                                                                       Surface Map

Likewise as in that first mid January visit, this new Arctic air pest will take its harshness out on the inhabitants of Southeast Michigan late Friday into Saturday but then; quickly begin to slide off to the northeast as the weekend comes to a close on Sunday. Snow showers and squalls we also accompany this latest blast (as it did back in January). The very latest indications are enough moisture will be transported into Southeast Michigan as a weak wave of low pressure transverses the front (see second map) to bring 1 to possibly 3 inches of snow across the region. Gusty north winds and falling temperatures later on Friday will exacerbate driving problems. Motorists driving Friday up through Michigan should be prepared for this winter weather and any subsequent lake effect snows with higher amounts.

                                                                        Surface Map

After this weekend, indications are the action will focus back to our southwest early in the week as the Jet Stream begins to re-group out over the Plains. At this time it looks as though some light snow or mixed precipitation may move back into the region toward Valentine's Day.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian

Wicked winter weather remains at bay on Ground Hog Day over Southeast Lower Michigan. Reasons why remain just as relevant now as discussed in my Mid Winter Outlook.

Mid Winter Weather Outlook Update issued 1/22/2012