SUMMER LOOMS, SO DOES ITS STEAM....

Summer is officially a week away but don't tell that to mother nature. A summery weather pattern is rapidly in the making and a 3-4 day heat wave gets underway Friday. The driving force behind the warmth will be a building high pressure aloft that forms over the Ohio Valley. That combined with a western trough will allow heat and humidity to surge into the Midwest. Here's the forecast 500mb jet stream structure Sunday morning. You can follow the heights from the Gulf right into central Iowa.

PWAT's (precipitable water vapor) are shown exceeding 2" on the western flank of the ridge from NW Iowa into Minnesota.

That's about twice the normal levels of water vapor which translates to lots of humidity.

As for highs, it appears 90 degree readings are likely around my area the next 4 days. Sunday (father's day) is expected be the warmest with highs projected to go into the mid 90s in spots.

The EURO actually shows a few points in SE Iowa and WC Illinois touching 100. That's probably a bit high but the ongoing dry conditions there will produce locally hotter temperatures in that part of the Midwest. Heat index values of 100-105 degrees are possible and heat advisories are likely.

Here's the odds of a 100 degree high Sunday on the EURO.

The NWS in Des Moines has already issued heat advisories for much of central and western Iowa. These should be expanded further east in coming days.

The strength of the warm air aloft should sufficiently cap the atmosphere and keep storms out of my area through Sunday evening. So even with a great deal of instability dry conditions are expected over the weekend. The NAM shows this for total rainfall through Sunday.

The weekend heat looks transient as a stout cold front dives southeast Monday. That should bring rain chances to much of the central Midwest at that time. If the front progresses as expected, any rain should be gone by Tuesday. The 500mb jet shows the ridge flattening, breaking down, and drifting east. NW flow will bring seasonal temperatures.

Highs Tuesday may not get out of the 70s in spots.

To some it up, it's not officially summer but you'll be hard pressed to know that this weekend. Happy Friday, stay cool, and roll weather...TS