THE WAKE UP CALL...

1 minute ago

3 min read

Like it or not, there comes a time each fall when the alarm awakens you to the fact that summer is done, put a fork in it! That's not to say we won't have some more very nice days ahead, but highs of 80 or above are likely done with until late March or April. Not only that, the wind driven chill that's descended on us tonight is just the tip of the iceberg of what our future holds the next 5 months. This little cold shot should come as no suprise though with Thanksgiving week little more than a month away.

Getting straight to the change, wind chills at 10:00pm Thursday are already in the 30s from NW Iowa into the Dakotas.

Driving the chill are winds gusting 40-50 mph over much of North and South Dakota. That's underneath the core of the strong cold air advection that settles over us by daybreak Friday. Gusts locally are likely to reach 40mph (perhaps 45) Friday morning at their peak.

Despite much drier air Friday temperatures at 5,000 ft. (850mb) will dip below freezing. That very cold air just above the surface will generate steep lapse rates and enough instability for considerable cloudiness and some spotty brief light showers. Thanks to continued cold air advection and passing clouds temperatures will move little during the day Friday remaining in the range of 45 NW to 50 SE. Winds again gusting in that 30-40 mph range will see to it that wind chills are in the 40s. By Friday evening, they've dipped into the low to mid 30s on the 3k NAM. Time for the coat.

The critical part of the forecast for the local growing season comes Friday night. High pressure advances on the region allowing winds to decouple. Under fair skies and dew points that could reach the upper 20s, frost looks inevitable. The bigger question is whether or not temperatures can dip low enough to establish a freeze (32). My counties north of HWY 30 are most at risk with readings from I-80 south more in the 33-35 degree range.

As it stands now, the NWS has a freeze watch in effect for many of my counties north of I-80 late Friday night and early Saturday. That could be refined a bit if warranted at some point Friday.

Saturday itself is a transition day featuring a gradual return of W/SW winds. This will have big repercussions Sunday with highs jumping from the low to mid 50s Saturday to the low to mid 60s Sunday. Monday night as you can see below, the 500mb jet builds back to the north and we are off to the races with another extended period of pleasant weather.

It won't be anything as warm as recently but it sure looks like mid 60s to low 70s will rule during the period Monday through Thursday of next week. That's 10-15 degrees above normal. The Climate Prediction Center has well above normal temperatures indicated in it's 6-10 day outlook. A no brainer.

Just for fun, I dialed up the U.S. based climate model the CFSv2 to see what it does with long range temperatures. I was somewhat surprised to see it being very bullish on colder weather east of the Rockies in its 30-day outlook spanning the period October 30th to November 29th. (The EURO is much warmer by the way). it would be easy to discount the CFSv2 except that as I mentioned in my last post, El Nino's are often front loaded with early bursts of cold in November and December. It's a trend I wouldn't bet on but it may have some merit. I'll keep an eye on it going forward.