Posted: 6:18 am Friday, July 20th, 2018
By Kirk Mellish
As I pointed out in my last blog post a couple days ago the main summer “heat ridges” have generally been to our East and out West leaving Georgia in a “weakness” aloft with relative low pressure. This has allowed above normal humidity, clouds and rain chances along with normal to a tad below normal high temperatures most days.
10 of the past 11 days have been 90 or a tad above, hardly unusual. Because of high humidity overnight low temperatures are running warmer than normal in the top 5 in many areas. But we have had virtually no 95 or 100+ days at all this summer and none in sight.
This pattern is about to be reinforced as an atypical jet stream pattern brings a trough of low pressure or even a “cut-off” low to much of the East and Southeast over the next week or two. This will result in anything but hot and dry.
Since a good chunk of Georgia has already had above-average rain this summer, the continuation means that some areas in the state will probably end up reaching or exceeding normal yearly annual rainfall totals sometime next month!
5-10 inch rain totals over a two week or so period somewhere in parts of Georgia and/or adjacent states would not be a shock, although exactly where the most will occur can not be determined.
Meanwhile, some of the same energy aloft (abnormal for this time of year slicing into unstable air) responsible for the Iowa tornado and other Midwest severe weather last night is heading Southeast (charts: PivotalWeather):
500mb jet stream vorticity and winds end of day yesterday:
This system is expected to be somewhat WEAKER when it reaches Georgia by Saturday, but we need to stay vigilant should that turn out not to be the case.
End of day Saturday:
This puts much of the Southeastern U.S. in a favorable “jet streak” jet stream pattern for enhanced lift or upward vertical motion in the atmosphere.
This should result in scattered showers and thunderstorms Saturday, some strong storms, and damaging winds in a few spots.
However, the details are yet to be determined as a variety of scenarios are possible. Nothing widespread is expected as of now. However, these “NW Flow events” can be tricky so that could change.
HRRR MODEL SIMULATED SATELLITE LATE FRIDAY NIGHT:
SPC SEVERE WEATHER OUTLOOK FRIDAY-FRIDAY NIGHT:
Looks like MOST activity stays Northwest of Atlanta Friday night, although the chance is here after 1a.m.
SEVERE WEATHER OUTLOOK SATURDAY-SATURDAY NIGHT:
(Level 2 is the “standard” or run of the mill risk level)
The risk lessens and pushes Southeast of Atlanta on Sunday:
PRELIMINARY indications are that the worst of the severe weather will miss the Metro Atlanta area Saturday and Saturday night, but this could change so stay tuned.
Either way, the system is expected to weaken here compared to the Midwest, Ohio River Valley and Tennessee River Valley. In fact, some models show almost nothing here.
At any rate it does not look like a washout Saturday. Plenty of dry hours and dry areas before and after any rain or storm both Saturday and Sunday!
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