Thursday, July 4, 2013

Fourth forecast and a look ahead to next week

After a gloomy Wednesday afternoon the 4th of July is looking a lot better!  There will be a little fog early in the morning but once that burns off skies will become partly cloudy by the afternoon with temperatures rising into the low to middle 80s.  There will be a slight chance of a thunderstorm developing around 3pm/4pm this afternoon with the heating of the day but once the sun sets tonight any lingering storms should move out.  Mother Nature won't be providing her own fireworks tonight with skies remaining partly cloudy around 9pm and temperatures in the low 70s.

A very strong blocking pattern in the jet stream has been in place for the past week and will be slow to break down through the weekend.  The image on the left is the water vapor and outlined in red is where the jet stream is.  A ridge of high pressure brought record breaking heat up and down the west coast over the past several days and a ridge out east has kept moisture streaming north through the Ohio River Valley with numerous thunderstorms and flooding rains along the east coast.  We, however, have been stuck in the middle and that's why it's been fairly cool the past couple of days.

By next week the jet stream pattern will begin to break down with the strongest part of the jet stream riding along the U.S/Canadian border and weaker winds within the jet stream moving across the middle of the country. 
These weaker winds are what we call 'zonal flow' meaning they run west to east rather than from north to south.  Zonal flow is usually an indication of a weak jet stream and can sometimes cause frontal boundaries to stall in one particular area.  As we've seen in the past stalled boundaries usually lead to frequent thunderstorms and heavy rain potential.  It's still way too early to determine where exactly, if any, boundaries will set up across the U.S. next week, but if we get underneath one it could lead to some heavy rain next Monday through Wednesday.

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