Wednesday, July 20, 2016

Summer Heat Across The US

A rather common summertime pattern is setting up across the United States bringing with it lots of heat and thunderstorms.  This pattern hasn't really developed since the super warm summer of 2012 and as a result many locations in the Central US are forecast to see their highest temperatures since then.  Here in Southern New England we will be largely spared that type of heat.  In fact yesterday and today are in the low to mid 80's with dew points in the 40's/50's.  The National Weather Service has issued a statement warning of elevated fire danger today.



If you are one to complain about that then there is nothing we can do for you as a human being.  The heat and another chance for thunderstorms will return Friday.

General Overview
First lets start off at the surface.  High pressure is currently onshore in the Northeast and building in the Rockies.  Both will slide east over time
WPC Surface Analysis 11 AM
The boundary draped across the Carolina's through Kentucky and into Missouri and Iowa is keeping the heat and humidity away from the Northeast.  Here are temperatures as of 12 PM
RTMA 2 m temps 12 PM
Some showers and thunderstorms are keeping temperatures down in Illinois and Iowa but these will pass and temps will sky rocket this afternoon there.  The upper atmosphere shows 1 upper trough off the Pacific Northwest and one off of New England.  The rest of the country is under the influence of a ridge.
12z NAM 500 mb vort, heights 2 PM (image NCEP/NOAA)
Because of this configuration the storm track is largely through Cali and then up into the upper plains then through the great lakes.  The advancing ridge (the warm front) is also producing storms.  Here is the US water vapor satellite.
GOES_Composite Water Vapor Loop (Image NOAA)
As hot as it will be in the South/Central/West US there shouldn't be too many record high temperatures set.  Here is tomorrow's NWS highs with potential records circled
NWS Forecast temps Thursday-record highs circled (image credit Weatherbell)
Getting back to New England high pressure moves offshore so tonight is a bit warmer than last night.  The humidity will also be a bit higher but it will not be unbearable.  High temps will again be in the mid to upper 80's.  Urban areas should push closer to 90.  If you plan on heading to the beach there will not be much of a sea breeze.  It is a good day to hit the shore.
NWS Northeast High Temps Thursday (image Weatherbell)
Some more active weather is possible Friday.  First here is the upper air chart for Friday 2 PM
12z NAM 500 mb vort, heights Friday 2 PM
There is a disturbance tracking through Southern Ontario.  At the surface we see an approaching cold front.
WPC Surface Forecast Friday 8 AM
It will be much more hot and humid Friday in New England.  Some models are forecast dew points near 70 which is unbearable.  Here is the forecast high temps for the Northeast
NWS max temps/records Friday (image Weatherbell)
Although it will be much hotter in the Mid Atlantic they should be protected by the ridge.  New England on the other hand will have to deal with this cold front passage.  As a result the Storm Prediction Center (SPC) has already placed New England in a severe thunderstorm risk area.
SPC Friday severe thunderstorm outlook 
The thunderstorm coverage should be scattered like it was on Monday.  That means not everyone will get severe storms or even rain.  At this range it is difficult to pinpoint where the highest risks are.  It will depend on AM cloud cover and atmospheric stability.  Northern New England is closer to the cold front/low so they should see more coverage.

The cold front will sweep off the coast overnight Friday into Saturday.  Temperatures do not cool off however.  Saturday is mostly sunny with a high near 90.  Sunday will have a chance of PM thunderstorms but most of the day looks good.  High temperatures also near 90.  We are in the heart of summer.

-Zack Green

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