Say goodbye to El Nino - at Least for the Next Week or Two as a "Changing of the Guard" Takes Place

The unseasonably mild weather of December, for the most part, has held into the first week of January. Temperatures across Southeast Lower Michigan still remain 3 - 5+ degrees above normal for January and the new year. This has been due to two main hemispheric weather patterns; a stiff El Nino jet crossing the Pacific and flooding (some times quite literally) the country with mild and moist Pacific air and an absent Polar Vortex which has been mainly hanging around in its stomping grounds - obviously in and around the North Pole. This is in the process of changing this weekend as these dominant patterns, highlighted in the Winter Outlook for Southeast Lower Michigan  with reverse dominance over Southeast Lower Michigan. This was expected this winter when I discussed the overall winter pattern, in my interpretation of analogues and local data and thus - it was not going to be all comfy and warm due to El Nino.

As the Polar Vortex dives south toward southern Canada in the upcoming days; it will usher in the cold air that has been charging-up the first third of the winter up over the Pole while we basked in unseasonably mild air the past five weeks or so. Have faith though; the polar/arctic air associated with these Polar Vortex's is not as severe as last February's nor January, in the Winter of 2013-14. The cold air will surge south along with the Polar Vortex into mainly the North-central and Northeast part of the country. This "Changing of the Guard" will bring more typical winter weather into the region with normal to even below normal temperatures at times. At this time; the coldest of the air will come in waves with the first due tomorrow, then a reinforcement scheduled for Tuesday into Wednesday. Latest indications are a moderating trend is likely by weeks end before another shot of colder air pushes into the country next week.

The initial fanfare of the mixing of the air masses (mild, Pacific and Gulf air with Polar and Arctic air) will brew a deep but somewhat moisture limited storm over the southern Great Lakes and Northeast. While this storm will deepen nicely, there is not a great moisture supply feeding it, so all precipitation in the form of rain and then snow will be light to moderate.

As far as snowfall, generally light amounts of mainly 1 - 2" can be expected over most of Southeast Lower Michigan with patchy 3" areas over the Saginaw Valley into Monday. Be advised, heavier snows due to lake enhanced moisture will fall over on the west side of Lower Michigan and Northern Indiana this week where several inches will fall in the snow belt regions! If heading out that way; keep abreast to those regions GRR forecast IWX.  

The worst of the weather over Southeast Lower Michigan will be the plummeting temperatures along with the light snow and snow squalls and wind on Sunday which will undoubtedly give rise to worsening driving conditions due to the formation of ice underneath on untreated roads. Temperatures will dive down through the 20s on Sunday. Reading will fall further into the teens by Monday morning. Look for temperatures to be in the teens and 20s for highs this week while lows fall to around zero to the single digits on the coldest mornings.


Maps for placement of the storm and weather Sunday morning and Monday morning.

Gone But Not For Good

El Nino's not gone for good across much of the country - just temporarily. However; I do believe he will be challenged more than recently by the pattern changes and the cold winds over the far northern hemisphere, as agreed upon in my Outlook for mid and late winter. As of now;  he's taking a imposed vacation as the Polar Vortex and associated colder air takes up residence up in the northern part of the country. A split flow will hold sway of the country the next week or two with the aforementioned area reverting back to more typical winter weather, while the southern areas are more dominated by El Nino enhanced sub-tropical jet. Here are recent long term trajectory upper wind weather maps into next week. Of course the further out, the less reliable but their use for trends are decent. Any development of significant storms with these pattern variations are possible and thus, will be monitored the next few weeks.

Try to get out and enjoy winter while we have it - as later in the month is less certain at this time. Look for updates regarding pattern reversals and/or resulting storms.

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