Getting Ready For A Heat Wave After An Active Saturday
by Angela Schilling, Meteorologist
April 22, 2012 8:26 PM
The record books have been closed for the last several weeks as far as temperatures are concerned, however, we may just have to open them back up again come this week. After an active Saturday we were left with a lot of wind and cooler temperatures on Sunday. Now as we head into the workweek a mini heat wave is in store.
We started this weekend with unsettled weather in southwestern Minnesota and northwestern Iowa. The image to your left shows the preliminary reports as of Saturday night, the red dots represent tornadoes. The setup on Saturday was a cold front moving east, with showers and storms developing out ahead of it. Dewpoints were in the upper 40’s to the lower 50’s out ahead of the front with marginal moisture and a decent amount of shear. Cape values or instability is what you need to feed the storms, and shear can get storms to rotate. With marginal moisture and a lot of shear, we didn’t see huge storms with tall updrafts, but rather shallow storms with brief spin ups. Throughout the afternoon several funnel clouds were reported with brief touch towns. As far as tornado reports go, we had a couple in Clay county, Iowa about three miles south of Spencer, and one just north of Cottonwood County in southwestern Minnesota.
Behind the front, drier air filtered into the region and so did the wind. Our winds transitioned to out of the north behind the front, and in return funneled in colder air for Sunday. Highs on Sunday made it up to the upper 50’s east of the James and lower 60’s up and down the Missouri River. Much warmer air could be found in the Pacific Northwest for the later half of the weekend, thanks to a strong ridge of high pressure aloft…over the next couple of days the ridge will continue to slide eastward and will eventually be knocking on our door by Monday afternoon, and peaking on Tuesday.
So in the upper levels of the atmosphere, where the jet stream is found, we’ll have a ridge building, and at the surface we will be in what’s known as the warm sector. The images below are from three different models, each forecasting temperatures for Tuesday afternoon. Notice how the second model or NAM is much warmer than the GFS.
GFS Model...warmest west of the James with highs in the 80's...70's in the Sioux Empire
NAM for Tuesday Afternoon warmer air moves farther east
Euro = blend between GFS and NAM
In general we’re expecting highs around 80 degrees in the southeast and temperatures close to 90 degrees up and down the Missouri River.
Now compare these forecasted numbers to the observed temperatures we saw this time last year, and it’s a good 10 to 20 degree difference. The warmest day in Sioux Falls last year during the month of April was 75, and the all time record for April in Sioux Falls is 98 degrees.