Summer is set to officially start this week but it won't look or feel like it in the northern and central Rockies where snow is in the forecast. Here's what the EURO shows for accumulations centered on the Teton's of NW Wyoming..
This larger perspective shows snow covering the peaks of the Rockies from Colorado to Canada.
The fact that it's snowing in late June is a huge tip-off that a major trough with plenty of cold air is digging into the western U.S. You can see the scope of the trough below centered on SE Montana Friday evening.
Downstream of the trough moisture will be streaming into the Midwest from the Gulf. Here's the forecast PWATs (precipitable water vapor) from the EURO Friday evening. Greater than 2.2" around the Quad Cities.
Dew points in Missouri are into the mid 70s, very moist!.
Highs Friday are shown into the low 90s to the SW tip of Iowa.
The heat and humidity will create ample CAPE (instability) which should fuel strong convection capable of very heavy rains and all modes of severe weather over parts of the Midwest Friday and Saturday.
Already the Storm Prediction Center has issued a risk area Friday for parts of Iowa, Kansas, Missouri and Nebraska. This will likely be expanded further east on Saturday in later outlooks.
Most of the long range models indicate the potential for the pattern to remain active well into next week. With the increase in convection will come the possibility of widespread heavy rains. The GFS shows this for 16 day total precipitation.
The EURO has this for 10 day amounts.
Short term I don't see much for rainfall through Thursday in my area. A few spotty showers are possible but they look very widely scattered and confined mainly to the late afternoon hours. Temperatures will continue on the cool side with highs mainly in the 70s. Wednesday could end up extremely fresh as a surface low tracks across Missouri and Illinois. The resultant easterly winds could hold highs in the low 70s (even the upper 60s), at least 10 degrees below normal. The Missouri surface low may also also generate some significant severe storms Wednesday but they are likely to remain south of the Iowa border. Roll weather...TS