It has been a great run of low humidity and sunshine for the last three days but that is changing this weekend. Humidity, temperatures, and storm chances are all on the rise.
Image above is a visible satellite shot from Friday afternoon. Both jet stream troughs that will impact our weather locally are in view. Each one is labeled accordingly. Saturday’s “ripple of energy” looks to be a little less amplified than Tuesday’s, thus packing less potential punch. However, it will help lay the ground work for the evolution of Tuesday’s trough.
The image above is an upper level analysis map with shaded wind contours. Notice how the lead trough (over Minnesota at the time of this analysis) has a jet maxima on the East side of the trough. Meanwhile the trough over British Columbia has a jet maxima around both sides of the troughs base. This gives that trough more potential to “deepen”, thus having more energy.
In regards to Saturday, the Storm Prediction Center has portions of our region highlighted in a level 1/5 risk for severe storms (lowest rating – only an isolated severe storm risk). Timing (per high resolution NAM pictured above) holds off on storms until Saturday evening. Much like what happened this past Tuesday, most storms will behave themselves with just one or two of them carrying the potential for damaging wind gusts. Don’t cancel your outdoor plans. Much of the day is fine. Evening plans, especially in the Northern Tier, keep a watchful eye to the sky and on our Interactive Radar in the Stormtracker 16 App (available on our website as well).
Overall the impact of Saturday’s storms don’t appear to be more than your typical strong summer storms. There isn’t much “shear” so the threat for rotation (i.e. tornadoes) is essentially zero.
Pictured above are forecast dew points for Tuesday afternoon from the GFS model. Fear not. These are likely overdone (by several degrees) and their placement doesn’t necessarily jive with the available ensemble data from the same model.
This is the ensemble GFS (known as GEFS) for dew point values exceeding 70. Two things to note here. 1. you don’t see a high chance for 70+ degree dew points in New England like you do in the operational model. 2. the placement for higher chances is noticeably further East. This lends credence to my theory that we’ll see the operational GFS show the cold frontal timing speed up a bit from what the operational run shows.
The contours ahead of the cold front show CAPE (Convective Available Potential Energy). Think of that like high octane fuel. The more that’s available, the stronger a storm can be. However, lots of CAPE doesn’t always translate into violent storms. Much like race cars need competent drivers to be pushed to the limits properly, CAPE needs a “driver”. That “driver” is lift which in this case will come from the cold front. CAPE largely hinges upon how much sunshine we see Tuesday.
Tuesday’s Bottom Line:
At this point I’m not as concerned about severe storms (damaging wind, hail, etc.) as I am for exceptionally heavy downpours. Keep in mind, these are thunderstorms that we’re talking about, and not everyone will see them. Those that do could see a very quick inch or two of rain depending upon the cold front’s speed.
There’s a lot to watch, your Stormtracker 16 Team will be doing that for you through the weekend. Make it a great one.
Stormtracker 16 Meteorologist John Hickey
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