The pattern shaping up across the US this week is likely to end up being the overall June setup a lot of with heat over the West while an astern trough allows shots of cool, dry air down over the Great Lakes into the Northeast and Mid-Atlantic.

True summer heat is now in place over the Southwest after a coolish spring with highs nearing 110 in Phoenix yesterday while Las Vegas topped 105. It’s as that ridge and bubble of hot builds north, keeping any cloud and disturbed weather out this week that cooler air and troughiness is driven SSE from Canada into the Upper and Lower Midwest with daytime temperatures held in the 60s and 70s along with low humidity. Nights are very comfortable and allowed to cool with dew points in the 40s.

It got chilly last night with lows dropping into the mid-30s over North Dakota and low 40s even down into Chicago this morning. You can always tell the air is nice and dry when you’ve got those kinds of readings at this time of year.

Here are highs from yesterday.

Note the 109 in Phoenix beneath the powerful ridge while it hit a chilly 61 in Chicago beneath the trough and NW flow.

Here are this morning’s lows.

Check out the 30 in Intl Falls, MN and the 32 at Marquette, MI.

While it was chilly with frost over the Upper Midwest last night, the chill spreads east tonight and tomorrow night and believe it or not but frost is possible over south-central parts of New York state and Pennsylvania tonight and tomorrow night following highs in the upper 80s the past 3-4 days.

Here’s the forecasted lows off the GFS for tomorrow morning.

Tuesday AM.

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Wednesday AM.

A Hot West Which Will Get Hotter!

While it may be hot now over the Southwest, the western ridge is set to build and build north through this week and particularly by late week into next week. According to the ECMWF thicknesses and 850 temperatures will rise over the Southwest which should drive highs up for such cities as Phoenix and Las Vegas, the two largest population centers. Just how hot may it get? Well going by ther ECMWF and it’s projected upper level heights and 850mb temperatures, I wouldn’t be surprised to see 116 in Phoenix and 112 in Las Vegas by the weekend or early next week while Reno, Spokane and Boise top 100.

Death Valley could top 125. These scorching temperatures may not just come and go as longer range modelling suggests the 5-15 degree above normal temperatures may stick around over this region through the next 10-20 days and look likely to hold on a hot note throughout the summer given the soil moisture content across the US. See my US summer forecast.

Check out the late week into early next week 850 temperatures.

Friday

Sunday

Monday

Tuesday

Notice the trough over the Central US extending east into the Ohio Valley with the western periphery of the Bermuda high keeping a SW flow up the East Coast.

The Northern Tier will remain cool with highs holding in the 50s and 60s with some rain and shower activity thanks to low pressure never far away.

Unfortunately a hot West and Cool east means the potential for storminess over the Plains this week and the SPC does have a slight risk over the next few days.

Tuesday

Wednesday

Storms blossoming over the Plains suggest severe weather and although the risk isn’t quite as high as late last week, there is always the threat for additional tornadoes particularly over Oklahoma and Kansas. The greatest threat however is likely damaging winds, large hail and flooding rains.

Speaking of heavy rains. Here’s the QPF for the next 72 hours.

Notice the continued soaking rains from Montana across the southern Wisconsin and of course the 1-3 inches of additional rains centred over Oklahoma up into eastern Kansas. The model is seeing the thunderstorms that should fire over the next few days in this region.

As for the big rains SW of Florida, well that’s the tropical system seems by the models.

Florida Flood Threat

Recent posts have made mention of the tropical stirrings down over the Caribbean with a lot of moisture streaming from Mexico and Cuba up into Florida. We of course saw Hurricane Barbara make landfall on the Mexican west coast last Friday. The reminant circulation from this feature looks to drift out into the Bay of Campeche Tuesday and Wednesday. Now there is a large area of fairly low pressure over the southern Gulf with water temps in the 80-84 degree range. That’s warm enough for development to occur.

As for shear, well as a trough now dips down to the US Gulf Coast, this is enhancing mid and upper winds across the Gulf but as this feature lifts out, so winds should slacken over the Gulf, allowing any feature moving ENE across the southern Gulf an oppertunity to organise and try to develop.

Here’s the current satellite image of the system.

Models have a system trying to organise by Thursday with a landfall over Florida this weekend.

The trouble with this situation is not just this feature on Florida but there is a LOT of moisture already streaming north over Florida and so before this even gets to the state, there will alreadt have been 2-4, locally 6 inches of rain down and if this tracks across the state, an additional 3-6, locally 10 inches is possible.

Below is the GFS with the system coming onshore near Cedar Key, perhaps as a weak storm. I don’t see this thing being a particularly strong feature except for producing gales over the Gulf and up against the coast. The big threat with this will be flooding rains.

By Saturday the system is seen tracking NE, parrelling the Carolina coast with the core of wind and heavy rain appearing to be offshore.

While in recent posts I have alluded to the possibility of this tropical system merging with an eastbound frontal system over the US which could present a significant flood threat all the way to Maine. Well right now, it looks like the system stays east of the front and so tropical moisture doesn’t get picked up by the front. This is a fluid and changable situation though and one cannot rule out an East Coast flooding event this weekend.

Here’s the latest QPF rain totals for the next 7 days. There’s been a lot of rain fall over South Florida in the past 10 days and a heck of a lot more is on the way and for points further north, where it’s needed but as per usual, this will likely be a little too much of a good thing.

A lot of lot for the Eastern Seaboard too as one front is now off the coast while another will arrives late week. Tropical connection or not, we may see a widespread area of 2-4 inches from the Appalachains to the coast.

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Tags: Florida flooding, florida tropical storm, hurricane season 2013, hurricanes, Invest 91L, June heatwave, us weather, Western heatwave