Weekend storm likely to bring 1st snow
It had to happen sooner or later.
A low pressure system spinning up from the south will bring a mixed bag of cold rain and snow to Minnesota this weekend. The big question...how much will fall as rain vs. snow?
The system:
An upper level low pressure system is spinning through the desert southwest today, and will move into the southern plains and wind up a surface low Friday. The low will deepen and move north into Iowa and Wisconsin Saturday.
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The precip shield:
Latest indications are the rain shield will spread slowly north Friday from Iowa into far southeast Minnesota. There are still significant model differences, but trends indicate the northern edge of the rain shield should move into the greater metro area late Friday night or in the wee hours of Saturday morning.
Computer models are cranking out a potential .50" and 1" of precipitation for central Minnesota, through the metro and into western Wisconsin with this system.
NAM model cranks out .50" to near 1" precip near the metro by early Sunday.
Rain or snow?
The temperature profile with this storm will be the single biggest factor deciding who gets a cold rain...or a pile of heavy, wet, plowable snow and slush.
Right now it appears the critical 32 degree temperature threshold (or rain/snow line) will set up very close to the Twin Cities metro Saturday. This could mean mostly rain in the east metro, and mostly snow in the west metro Saturday, with a trend toward all snow by early Sunday morning.
NAM 850 millibar temp profile shows critical freezing line (rain/snow) very near the Twin Cities Saturday.
Some of the forecast models paint a relatively narrow band of heavy snow from near Fairmont, to Mankato into the far west metro toward Mora and Hinckley. Willmar and St. Cloud may also fall into the heavy snow area under this scenario.
If the rain/snow line sets up through the metro...there could be a HUGE difference in snowfall amounts. There may literally be an inch or less in the east metro....and maybe 5" to 10"+ just west of the Twin Cities.
NAM model snowfall paints a scary scenario of heavy snow just west of the metro by Sunday morning.
The bottom line is...be READY for wintery weather and poor travel conditions this weekend from the metro west and north.
We'll try and pin things down a bit late on Friday as we get another day's worth of model runs (which come in every 6 hours) to grab onto the system as it moves out of the southwest. A change in the rain snow line of 40 miles could mean the difference between mostly rain...and a pile of heavy wet snow in the metro!
Stay tuned....
A trend toward milder Minnesota Novembers?
Our recent warm spell has Minnesotans talking about the weather.
There is evidence of a distinct trend over the past decade toward milder weather during November in Minnesota. Check out these numbers.
-Wednesday's record high of 68 degrees in the metro was 25 degrees above average for the date. 68 is the average high in the metro for May 11th!
-November 2010 temperatures running +9.2 degrees through the first 10 days in the metro.
-The 4 consecutive days of 60 degree plus temperatures this month marks the 3rd latest (tie) date on record that such warmth has occurred.
-4 of the 6 latest (and longest) stretches of November warmth have occurred since 2001, including the past 3 years in a row. (2001, 2008, 2009, 2010.)
-Every November since 2004 has been warmer than average in the metro. Temperatures during that time have ranged from +1.5 to +9.6 degrees during November.
-Every November since 2004 has featured below average snowfall in the Twin Cities. November average snowfall in the metro is about 10". November metro snowfall has ranged from a trace to 5.1" during past 6 years.
Twin Cities AMS presents Minnesota Tornadoes 2010:
The Twin Cities chapter of the American Meteorological Society offers a presentation entitled "Minnesota Tornadoes of June 17, 2010: A Review and Discussion" this Friday evening at The University of St. Thomas in St Paul at 6:30pm.
The event is free and open to the public, and all are encouraged to attend.
PH