Big weekend weather changes 

Posted: 6:05 am Friday, April 13th, 2018

By Kirk Mellish

Warmer than normal temperatures continue Saturday (average is now 72) but noticeably cooler Sunday, and then Monday highs will struggle to reach 60 with lows in the upper 30s to low 40s Tuesday morning.

We need to monitor heavy rainfall potential (looks like an average of 1 inch, with isolated higher totals) and maybe some severe thunderstorms in the warm to chilly transition.

SATURDAY AFTERNOON SURFACE WEATHER CHART:

Screen Shot 2018-04-13 at 5.37.12 AM

SUNDAY SURFACE WEATHER CHART:

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SURFACE WEATHER CHART MONDAY MORNING:

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ESTIMATED AVERAGE RAINFALL SATURDAY:

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ESTIMATED AVERAGE RAIN AMOUNTS SATURDAY NIGHT:

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ESTIMATED AVERAGE RAIN SUNDAY:

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SEVERE WEATHER OUTLOOK LATE SATURDAY AFTERNOON/SATURDAY NIGHT:

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SPC SUNDAY SEVERE WEATHER OUTLOOK:

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Here is the forecast discussion from the National Weather Service Atlanta office in Peachtree City:

“NAM model soundings indicating convective development could be
suppressed somewhat Saturday afternoon/early evening from a 800-
750mb cap so thunder chances may end up being more isolated, though
enough deep layer shear to keep a stray strong to severe storm from
being ruled out.

Hi-res consensus keeps the main line of development just west
of the CWA border until after midnight. Based on shear parameters
for the early morning Sunday, feel that the previous thoughts on
threat potential are still there for primarily damaging winds and a
few brief tornadoes along any bowing segments. Some isolated
flash flooding cannot be ruled out too given the slower
progression of the moisture and mean flow having little
directional change out of the SSW”.

 

There is often a trade-off between sufficient instability and wind shear in deciding the degree of severe weather threat, especially here in the Southeast U.S. and especially with systems that enter a wedge pattern or that come into the area in the morning when the atmosphere is cooler and thus generally less unstable.

So MOST of us stay dry Saturday but an isolated strong storm can’t be ruled out, especially NW suburbs, with more widespread rain and some storms likely during Sunday. Obviously the timing and threat level can change so stay tuned. I’ll be on the radio with updates through the weekend.

Follow me on Twitter @MellishMeterWSB.

 

 

 

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