July 18: Heat Wave This Week, Daily Links

WEATHER

The first half of July brought us a persistently “unsettled” weather pattern, with several instances of severe weather and flooding.  Nashville has received almost 5″ of rain this month, putting us about two inches above-average to this point in the month.  Despite the wet pattern, temperatures have still been hot — we’re running two degrees above average for the month overall.  We’ll add a degree or two to that number as we head through this week, as a genuine heat wave settles into the middle of the country.  We’re far from alone in this — if misery loves company, there’s going to be plenty of love to go around:
HEAT WAVE
The big blue “H” stands for “high pressure” — a phrase you probably hear meteorologists use, and a phrase you probably don’t completely understand.  Atmospheric pressure refers to the literal weight of the air on top of us — when the pressure is high, the atmosphere is pushing down on us to a greater extent (and vice versa for low pressure).  Sinking air heats up, which is why summertime high pressure areas are associated with heat waves.  We’re not talking about record-setting heat, but temperatures today should still easily reach the mid 90s:
MONDAY HIGHS
Factor in the humidity, and the heat index will eclipse 100 degrees:
MONDAY HEAT INDEX
The National Weather Service doesn’t issue heat advisories until the heat index reaches 105 — we’ll be close to that territory today, but those advisories are more likely to be issued later this week.  Regardless of whether the technical heat advisory criteria are met, you’ll need to stay in the “dangerously hot” mindset: find some shade (or better yet, some A/C), stay hydrated, and take plenty of breaks if you have to be outside.  Common sense stuff!  And make sure your furry friends are taken care of — outdoor pets should have a shady spot to avoid the heat, and a supply of cool water as well.

The sinking air overhead will also suppress our storm chances to around 20% — most of the clouds that try to grow into full-fledged thunderstorms will be squashed by the weight of the high-pressure air mass.  However, a few of those clouds will be able to break the lid on the atmosphere, which gives at least a chance of some brief relief from the heat.  The HRRR model pictured here isn’t enthusiastic about those chances:
hrrr_2016071811_ref_nashville
That forecast model does try to bring some storms into our northeastern counties — those storms are north of the Ohio River this morning, diving down to the southeast.  It’s not likely that they’ll hold together and impact the WSMV viewing area, but I can’t cross it off the list of possibilities just yet.

It’s more likely that we’ll see some storms dropping in from the north late tonight, as the RPM model depicts here:
RPM 12A TUE RPM 2A TUE RPM 4A TUE
Our overnight storm chances will dictate our storm chances later in the day Tuesday — as the pre-sunrise storms diminish, they’ll lay down a boundary that will be the focus for additional storms later in the day.  Figuring out exactly where that boundary will shape up is really tricky — Futurecast shows a reasonable pattern, but the exact timing and placement remains in question:
RPM 10A TUE RPM 12P TUE
A few of the storms tomorrow could be strong to possibly-severe — the Storm Prediction Center has outlined a “Marginal Risk” (level 1 of 5) for severe thunderstorms in southern Kentucky and northeastern Middle Tennessee:
PAUL SEVERE RISK REGION

The rest of the week will bring us our typical summertime 20-30% daily storm chances, along with plenty of heat and humidity.  The hottest days will likely be Thursday and Friday — Thursday’s record high is exactly 100 degrees, and we’ll give it a run:
WSMV 7 Day AM

 

LINKS

An easy way to beat the heat — stay inside with some nerdy reading material…

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About paulheggen33

Morning meteorologist for WSMV-TV in Nashville.
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