COOL IS SOON TO BE THE NEW RULE...
Southerly winds brought summery temperatures back to the region Thursday. Highs reached the mid to upper 80s in most spots with the NWS office in Davenport reaching 89 degrees. The party has come to an end out west where parts of the Dakota's are in the 40s. Further west, snow is expected to develop in the Rockies where Denver is under a winter storm warning for 6-12" of heavy wet snow.
Higher elevations west of Denver could see amounts in the 18-24" range.
Snow is not unusual in May but the expected amounts are. This could very well turn out to be the largest late season snowfall in Denver history. Widespread power outages are likely since leaf out has occurred. Residents have been urged not to park or walk under trees with significant snow cover.
The cold air that may break records in Denver is on the move. You can see Thursday evening it was approaching NW Iowa. In South Dakota, Vermillion (near Sioux City) was at 95 while out west near Rapid City, it was at 39 and falling.
Out ahead of the cold front thunderstorms developed Thursday evening from NW Iowa into Minnesota. The storms never really organized into a cluster (or complex) with a cold pool that would sustain and drive them into the NW half of my area Friday morning. The latest runs of the GFS and EURO are not very enthused about storms holding together or producing much in the way of rainfall, especially compared to earlier runs. We shall see but at least there is a chance of some scattered showers and storms early Friday, especially NW of the Quad Cities. Here's what models we're suggesting for rain totals through Friday morning. Little if any rain is shown over the southern half of my area.
No matter what happens, much cooler air begins to make inroads into the region and scattered showers and considerable cloudiness will prevail during the day Friday. From the Quad Cities southeast the cold front does not hit until late morning or early afternoon allowing temperatures in this zone to reach the upper 70s to low 80s before falling after the passage of the front. The north never enjoys that degree of warmth as readings start in the mid to upper 60s and hold steady or even fall a few degrees during the day.
Some models have been trying to activate some late day or early evening storms along the cold front in the far southeast Friday. Most of what I've seen has the front long out of my area before storms fire. As I write this SPC has some of my Illinois counties in a slight risk area for severe storms. I'm playing that down and have a feeling SPC will shift the risk well to the east so keep that possibility in mind.
Friday night the front comes to a halt in central Illinois allowing a weak wave to move northeast along it as the primary trough ejects into the upper Midwest. By then we a in the cold sector and the over-running will generate clouds and scattered showers Saturday. Rain totals are likely to be light but with temperatures not getting out of the 50s in may areas, highs will be at least 30 degrees colder than what we saw Thursday. The hi-res HRRR is depicting temperatures in the mid to upper 50s, not too much above record cold maximums for the date.
Readings like that are a good 25 degrees below the norms. Look how widespread the chill is from here west.
Sunday should start with some sun but cold air aloft drives enough instability for afternoon cumulus development. Some low stratus and a few sprinkles might skim the north. It will be another cool day with readings ranging from the upper 50s far north to the low 60s elsewhere.
Monday should be a cool but decent day before the next system arrives Tuesday and part of Wednesday. There is good consensus that this will be another cool wet system with at least moderate rains. Most guidance keeps highs in the upper 50s to low 60s both Tuesday and Wednesday.
After that we can start thinking about Memorial weekend. We're still over a week out so it's too early to get detailed. Temperature trends are warmer on the EURO than the GFS but early indications are readings will be seasonal to a bit above normal if things hold. At least for now, the GFS and EURO are showing little if any rain but that is not something I would hang my hat on at this distance. So far so good is the way I would sum it up at this poin