RING AROUND THE ROSIE...
Once again the focus of our weather this week is closely tied to the the strength of a significant heat dome that resides over the Plains. Fortunately for us, we've been on the eastern flank of the heat where the NW flow aloft has kept the worst impacts to our west. A couple times we've gotten a taste of what could have been but were blessed by the passage of backdoor cool fronts that have kept temperatures and humidity from getting out of control for more than a day or two. In other words we've had some very warm days but in general not the blistering stuff that's found to our W/NW thanks to our little game of ring around the rosie with a heat dome.
In the 500mb jet stream depiction above you can see the NW to SE orientation around the ridge centered over Wyoming. That brought a front through Saturday evening that really knocked the humidity back Sunday and Monday after a stifling day Saturday. The ridge is expected to expand a bit and by Wednesday the core has moved from Wyoming to the Kansas Nebraska border. See Below.
That little nudge will cause heights to rise allowing warmer air and higher humidity to creep back into the area midweek. This is something I anticipated last week. Temperatures are likely to reach 90-94 Wednesday but the dew points will go into the 70s from the 50s and 60s we've seen since Sunday. This is going to jack heat index values back to very uncomfortable levels. How bad will be determined by just how high dew points get, any convective debris from storm clouds up north, and even smoke from distant forest fires. Currently models suggest a large variance in Wednesday's heat index potential from readings around 100 on the EURO and GFS to as high as 110 on the 12K NAM. Personally I would argue for the lower end of the spectrum as the hi-res CAMS have recently been overdoing dew points by several degrees. Here's a little sampling of what's out there.
The 12K NAM
No matter what, Wednesday looks to be a mean day with significant heat index values and most likely heat advisories
Wednesday night or early Thursday most models suggest another back door front that breaks the short siege of heat and brings readings back to seasonal levels later Thursday (and especially Friday through Sunday). These are the day 4-9 temperature departures on the EURO (July 30th-August 4th).
The day 10-15 departures are also looking good with comfortable temperatures August 5-10th.
Here's the big change at 500mb that thwarts the heat from making inroads in my area past midweek.
The biggest issue on the table now is that Tuesday will mark the 12th ( in some spots 13th) consecutive day with no rain. This is stressing crops and grass alike, especially in parts of my northern counties which have seen far less rain than the south. With the back door front the potential is there for some showers and storms but timing and a strong and potentially suppressing summer cap (warm air aloft) will dictate coverage if we are lucky enough to get anything to fire.
In general, models are not providing much hope with total rainfall forecasts that look like this through Sunday.
Anyway, the transition to a couple very warm days is underway Tuesday but nothing like the EURO was showing last week when it had 90s from last Saturday to Sunday of this weekend...even a 100 degree day. Check it out below.
I never bought the EURO's extreme solution as we are in phase 6 of the MJO which does not favor heat of that magnitude. Here's what the new EURO is now showing which looks far more reasonable to me and fits my ideas from 6 days ago. It may still be a few degrees to warm.
Well, that's all I have for you today as we finish out the last week of July. Where has the summer gone? Roll weather...TS