July 11: Stormy Pattern Continues, Daily Links

WEATHER

The rain chances shifted southward over the weekend, but now the unsettled pattern is drifting back to the north to start the new work week.  Scattered showers and thunderstorms are pretty likely today and tomorrow…that’s the easy part of the forecast.  The hard part of the forecast is trying to figure out when and where the best chance of storms will develop.

I’ve written (probably hundreds of times) about how forecast model data is useful for showing us the pattern of storm development, but not all that useful for the specific timing and placement of those storms.  That’s usually the case in the summer, when the atmospheric boundaries that help to enhance our storm chances are poorly-defined at best.  The problem today is that the various forecast models can’t even reach a consensus regarding the pattern, much less the specifics.  Our in-house RPM model shows the best chance of scattered storms to the north of I-40:
RPM 10A MON RPM 12P MON RPM 2P MON RPM 4P MON RPM 6P MON
While another model, the WRF, shows the best chance south of I-40:
WRF 10A MON WRF 1P MON WRF 4P MON
And yet another model, the HRRR, doesn’t really show much rain at all!
hrrr_2016071110_ref_nashville

That lack of any kind of consensus is, of course, a wee bit frustrating to forecasters.  First we do this…
mad
…then we settle into this:
no-answer

The truth is likely somewhere in between the various forecast model opinions.  I think the best chance of getting at least SOME rain in your backyard rain gauge will be in northern Middle Tennessee and southern Kentucky:
PAUL RAIN TIMING
It’s not like you’ll be dry farther south…in fact, the larger gaps in between the scattered storms will allow for additional heating, which will spell a slightly greater threat of stronger storms.  Overall, the Storm Prediction Center has categorized it as a “Marginal Risk” (level 1 of 5) for severe thunderstorms:
PAUL SEVERE RISK REGION
In terms of timing, the midday and early afternoon time frame looks most-favorable for the most-widespread showers and storms:
PAUL DAYPART POPS

A little July sunshine goes a long way toward heating us up, so I expect temperatures to reach the upper 80s, with heat indices running in the upper half of the 90s:
PAUL DAYPART GRAPH
As always, your hour-by-hour temperatures will be determined by whether or not it’s raining at your specific location.

More of the same tomorrow — once again, I think the best storm chances will take shape in the northern half of the Midstate, with maybe a few stronger storms mixed in:
RPM 7A TUE RPM 10A TUE RPM 1P TUE RPM 4P TUE RMP 7P TUE

Our rain chances drop to a seasonally-appropriate 20-30% Wednesday and Thursday, but that means temperatures will heat up to well above 90:
WSMV 7 Day AM
The next good chance of thunderstorms heads our way Friday, and could linger into Saturday.  The Storm Prediction Center hasn’t included us in any extended-range severe weather outlooks, but the “analog” forecasts (comparing this week’s forecast pattern to similar historical patterns) point toward a decent chance of strong/severe storms on Friday:
PRALLC01_gfs215F120

You should look at the Friday-Saturday-Sunday part of the forecast as “informed speculation” at this point — with this type of weather pattern, the day-by-day storm chances have a tendency to rearrange the atmospheric setup, which has a cascading effect on the forecast down the line.  Stay plugged into the forecast for revisions throughout the week.  Yes, that’s annoying to hear when you’re trying to make outdoor plans…but that’s summertime reality around here!

 

LINKS

A short list of nerd-links this morning, since I’m a little pressed for time…

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About paulheggen33

Morning meteorologist for WSMV-TV in Nashville.
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