Updraft: April 26, 2012 Archive

March Flashback: Blustery & colder; Rain to S-N-O-W Friday night?

Posted at 8:32 AM on April 26, 2012 by Paul Huttner

19 degrees - wind chill at International Falls at 7am this morning

45 degree temp crash in most of Minnesota in about 36 hours

Rain system moves in Friday

Cold enough for all snow Friday night?

Source: Twin Cities NWS

Major Pattern Change:

Well that was nice while it lasted.

This week's 70 degree temps are long gone, replaced by a blustery attention getting cold front. You can feel the chill today, the shorts are history and jackets are now in vogue.

A cold wintery pool of air is pouring south from Canada today.

Source: University of Illinois

Temps will struggle to reach the 40s up north today, and the 50s in the south. With the wind, it feels like March again, with May just around the corner. You had to know this might happen when we hit 80 on St. Patty's Day.

The big question in the weather lab this Thursday is... are snowflakes far behind?

Rain to snow Friday night?

The forecast models are split on just how far north a rainy swipe will push Friday into Friday night.

The NAM is more aggressive, bringing a swath of rain from southern Minnesota up into the metro Friday night, then injecting enough cold air in the system to change a cold over to all snow. The NAM suggests possible accumulations by Saturday morning in the metro, central Minnesota and western Wisconsin.

Source: Iowa State University

NAM model hints at possible accumulating snow by Saturday morning
Source: NOAA/wxcaster.com

The GFS holds back a bit, keeping the bulk of the moisture just south of the Twin Cities, and easing up on the colder air. The resulting solution favors less, if any significant snow for the metro area.

Either way it's going to be chilly and potentially wet Friday night into early Saturday.

It's just too early to make a "credible" meteorological call yet...we need to see more model data on Friday, and hopefully more agreement on a potential solution.

We really shouldn't be shocked by the potential for snow in April, in an average April we see about 3.1" of snowfall in the metro. For all the breathless talk of climate change, it appears there are some things in Minnesota that just don't change. Late spring snowfall potential appears to be one of them.

As we say in the weather biz...stay tuned. And don't be surprised if you hear a lot of different solutions in the next 24 hours!

PH

Rumors of snow; Cool weekend; Milder next week

Posted at 5:15 PM on April 26, 2012 by Paul Huttner

Frost & freeze advisories north & east of the metro Friday morning

Growing snow chances close to the metro overnight Friday into Saturday AM?

"Temperature critical" - models right on the freezing line for rain/snow early Saturday

Cool weekend highs in the 50s at best

64/43 average high/low for the Twin Cities this weekend

Warming trend next week - a return to 70s?

Frost/freeze adviosries early Friday
Source: NWS

Frosty start Friday:

Right on schedule. This weekend is on average the date of the last frost of season at MSP Airport. Cool Canadian high pressure is nosing into just in time to keep us "close to average" with another shot of frost close to home this weekend.

Frost is likely in the metro suburbs tonight, especially on the north & east side. A hard freeze is likely for Mille Lacs, Mora and Rice Lake.

After our record warm March, it's easy to wave our hands and scream "extreme weather, extreme weather" with frost this time of year...but it's absolutely as normal as normal gets to see frost in late April in these parts.

Source: MN Climate Working Group

So, what about snow?

Sometimes in Minnesota it seems we need to be reminded where we live. It snow here in April, sometimes even in late April. MSP Airport average about 3.1" of snow in a "typical" April. So far this April? Just a trace at MSP, closer ot a foot in some places up north.

There are still big model differences on our chances for snow near the metro overnight Friday night into Saturday morning. Here's the best breakdown of the system at this time.

The system:

Low pressure tracking from near Kansas City Friday night through northern Missouri into Illinois by Saturday. The NAM suggests closer track to MN. The GFS and European models seem to suggest a track farther south.

Moisture:

The system will draw up some moisture from the Gulf of Mexico and inject it into southern Minnesota. Drier air at the surface will eat away at the northern edge of the system in Minnesota. One of the big questions with this system remains how far north will moisture be able to ride as it bucks the dry intrusion from the north? This result will be a rapid cutoff in rain/snow and the cloud shield on the systems northern edge.

Temperature profile:

This is the biggest question with this system.

Models agree the system will be warm enough for all rain Friday and Friday evening. Sometime around midnight, forecast models strongly suggest that enough cold air will work into the system that a changeover to all snow will occur on the systems northern edge...probably over southern Minnesota.

The NAM model is the most aggressive with this changeover, and with pushing moisture north toward the Twin Cities. It suggests a few inches of wet slushy snow are possible by Saturday morning. It could be on to something, or it could be "model terrorisim." Sometimes the NAM gets a little hyped about potential snowfall.

Check out the (gulp) graphic below.

NAM model: A few inches of slushy snow by Saturday morning?

The GFS is less impressed, and suggest maybe a few wet snowflakes mixed with rain...and most of the heavier precip remains south of the metro.

Bottom line? At this point there is a chance of rain mixing with or changing to snow Friday night into Saturday morning. Let's see if the models can come up with a more consistent solution by Friday evening.

Cooler weekend:

Any way you slice it, this weekend is going to feel a lot colder than our flirtation with 70s earlier this week. Morning will trend frosty in clear areas, and Saturday may have trouble climbing out of the 40s.

Sunday still looks to be the slightly nicer day this weekend with some clouds and sunny peeks...but temps will remain cool with highs in the 50s.

Warmer next week?

Overall the pattern appears to shift for the warmer, and wetter next week.

Warming trend next week
Source: Iowa State University

Slow moving low pressure may set up in Nebraska and pump warmer air..and more moisture into Minnesota. We could see a few bouts of showers and T-Storms next week. We need the rain, and if that GFS suggested pattern holds, some places in Minnesota could get heavy soaking rains next week.

Source: NOAA

As long as it's at night, during the week right? If only I had the power to "schedule" our weather to make people happy. Wait, I'm not sure I'd want that job either!

PH