June 25: Heat Advisory, Strong Storms Friday, Daily Links

1:30pm UPDATE: Thanks to some high clouds overhead that have filtered out the late-June sunshine, temperatures haven’t been quite as dreadful today as some of the model guidance was indicating.  But dew points have been running in the mid 70s, so it still feels like 100+ degrees.
gross_no_thank_you_supernatural

Regarding tomorrow evening’s severe weather potential, the Storm Prediction Center essentially left their Day 2 outlook unchanged with the early-afternoon update:
SPC-Day2-Cat

The analog guidance has trended in a hopeful direction — it now estimates a 40% chance of at least one severe report (wind or hail) in the Midstate:
SVRall_N1_110km_nam212F036

The newest model data still bring slowly weakening storms into the Midstate Friday evening — I’ll do a complete breakdown of that in tomorrow morning’s post, but I won’t inundate you with a ton of images for now.  One of the Futurecast models does bring some non-severe storms into the northern half of the Midstate overnight tonight, but I’m skeptical about that.  Tune in to Dan Thomas’ forecasts this evening for the latest analysis, and of course I’ll be on-air bright and early tomorrow morning from 4-7am.

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WEATHER

It’s a pretty simple weather story today…it’ll be hot:
PAUL RPM 4KM Temperature

It will be humid enough to make it feel ever hotter:
PAUL RPM 4KM HEAT INDEX

In fact, with the heat index approaching 105 degrees, the National Weather Service has issued a Heat Advisory for parts of the Midstate, including Metro Nashville:
PAUL WATCH

Not much of a storm chance today — 20% at best, so don’t count on any relief from Mother Nature.  The usual common-sense hot weather advice applies…find some shade, find some air conditioning, stay hydrated, and just generally take it easy.
turkey-coma1

It will still be hot and muggy on Friday, with highs in the low 90s.  Some scattered storms will likely develop Friday afternoon, as depicted on Futurecast:
RPM 4P FRI

Those afternoon storms will be of the typical summertime hit-and-miss variety — they won’t be very organized, so they won’t have much severe potential.  But a more organized storm complex will be taking shape to our northwest, knocking on the doorstep of our northwestern counties by Friday evening:
RPM 7P FRI

The storms will progress across the area from northwest to southeast Friday evening and Friday night.  Here’s Futurecast’s version of how that will play out — keep in mind, this is 36 hours away (as I’m typing this), so there will likely be at least some changes…but this is  a reasonable depiction:
RPM 9P FRI RPM 11P FRI RPM 1A SAT RPM 3A SAT

The severe weather potential will be greatest in the early evening, when the atmosphere is warmer and more unstable.  The storms will become gradually weaker as they move through — so if they move in faster, the severe threat will persist farther to the south.  If they move in more slowly, the severe threat will play out farther to our northwest.  For right now, the Storm Prediction Center has kept the “Slight Risk” (level 2 of 5) for severe thunderstorms just barely off to the north and west, with the northern half of the Midstate in a lower “Marginal Risk” (level 1 of 5):
PAUL SEVERE RISK REGION

The main threats will be from damaging straight-line wind gusts in excess of 60mph, and localized flooding due to heavy rain.  Cloud-to-ground lightning will also be a concern — the storms Tuesday night were very electrically active, and I think a similar scenario will unfold tomorrow evening.  The SPC will issue another outlook early this afternoon, and I’ll post a quick update at the top of this post when that happens.

The SPC’s SREF (Short-Range Ensemble Forecast) model depicts the best chance of organized more-likely-to-be-severe storms lining up with the Slight Risk area, running around 50-70% as the storms enter the Midstate Friday evening:
SREF_prob_combined_supercell__f039

The “analog forecast” (comparing Friday’s weather pattern to similar patterns in the past) shows a greater threat farther to the south — specifically, a 50-60% chance of at least one severe report in the Midstate:
SVRall_N1_110km_nam212F048

A look at the types of severe weather produced by those historical systems helps to confirm our thinking that straight-line winds will be the main threat (blue dots), but the analog forecast also thinks some hail will be possible (green dots):
SVRnam212F048

A little glimpse into the mind of a meteorologist…
Best-simpsons-gifs-homers-brain
…okay, but really.  One of the most important questions in the forecasting process is this: how could I be wrong?  That is, what are the most likely scenarios that would force me to adjust the forecast?  In the case of tomorrow evening, I think the most likely adjustment would be slower storm movement — the storms enter the Midstate later Friday evening, but they last longer than what the forecast models are estimating.  But we’ll wait and see on that.

Showers and a few thunderstorms will linger over the southeastern part of the Midstate Saturday morning, but by midday Saturday we should be dry, with decreasing clouds Saturday afternoon.  The humidity will be noticeably lower Saturday night through Monday morning.
yippie

An unsettled weather pattern shapes up again next week, but right now it’s looking like we’ll be able to avoid high temperatures in the 90s for several consecutive days:
7 Day PM

 

LINKS

So much stuff today.  SO MUCH SCIENCE!
science

About paulheggen33

Morning meteorologist for WNCN-TV in Raleigh.
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