Big Heat Week into July 4th Weekend

[MN Transplant]

My annual warning for reading the 5-minute obs.  Because of rounding, a 5-minute reading of 99 could mean 98 or 99.  A reading of 100 is 100.

[Eskimo Joe]

14 minutes ago, TSSN+ said:

100+ should happen unless it clouds up at all.  

Per the 12z IAD sounding, the convective temp is 95°. We are slightly warmer at 700mb compared to yesterday, and there's weak warm air advection noted as well between 600mb - 800mb. That should work to maintain a reasonably stout cap throughout the day. 

[WxUSAF]

1 hour ago, TSSN+ said:

It’s hazy as hell this morning 

Super hazy. 
 

But note that it’s sunny, hazy, hot and humid as shit, and we don’t have air quality alerts. Pollution control works! We should keep doing it!

[Eskimo Joe]

Just now, WxUSAF said:

Super hazy. 
 

But note that it’s sunny, hazy, hot and humid as shit, and we don’t have air quality alerts. Pollution control works! We should keep doing it!

Yup. I remember the heat waves in Philly during the 90s. The air was brown and it smelled like ash or batteries (ozone?). Just the worst.

[WEATHER53]

A general rule of thumb in heat situations like this is add 10F to the  10am temp at DCA for its high and it’s at 92 at 10am 

[DDweatherman]

There shall be no struggle to reach 100 today I suspect. 
 

BWI is already at 93. I wouldn’t be surprised to see 103-104 in some areas. Stations over here east of 15 in S PA/N MD are torching. 

[MN Transplant]

One good thing that I'm seeing is that the new RRFS seems to be handling this a lot better than the HRRR.  The HRRR is out of control with mixing out the boundary layer, with places like Fredericksburg with something like 108/55 tomorrow.  Conversely, the RRFS is a reasonable 102/69 for tomorrow.

[Eskimo Joe]

7 minutes ago, MN Transplant said:

One good thing that I'm seeing is that the new RRFS seems to be handling this a lot better than the HRRR.  The HRRR is out of control with mixing out the boundary layer, with places like Fredericksburg with something like 108/55 tomorrow.  Conversely, the RRFS is a reasonable 102/69 for tomorrow.

Yea the RRFS may be a formula for better future CAMs. I still like the HRRR because it shows what would happen if we overmix by some chance, almost like a goalpost kind of scenario.

[MN Transplant]

10:30am and we have our first couple of mesonet sites hitting 110 HI.

[DDweatherman]

6 minutes ago, MN Transplant said:

10:30am and we have our first couple of mesonet sites hitting 110 HI.

Could approach some records today.

[kgottwald]

42 minutes ago, WxUSAF said:

Super hazy. 
 

But note that it’s sunny, hazy, hot and humid as shit, and we don’t have air quality alerts. Pollution control works! We should keep doing it!

In the seventies and eighties, a typical HHH summer day would have a milky-white sky with the sun not even visible! The only sign that a thunderstorm was approaching was the white gradually darkening. As a kid, I didn't know what was meant by references in books to "seeing the storm clouds gathering".

[MN Transplant]

6 minutes ago, DDweatherman said:

Could approach some records today.

IAD is almost certainly going to get their record daily high today.  This airmass isn't historic enough to challenge all-time highs, but daily records at any time in July is impressive.  And the lows will challenge records too.

[JakkelWx]

112 heat index and its only 10:59 AM. category 5 swamp ass.

[weatherCCB]

94/75

[pazzo83]

1 hour ago, Eskimo Joe said:

IAD and BWI are probably a lock. DCA will always be heavily dependent on a river wind. That being said, I would tend to agree with you.

DCA actually hit 100 a few times in 2024 with a south wind, so it still can happen.

[pazzo83]

DCA is 94/76 at 11am.  Absolutely brutal.

[George BM]

1 minute ago, pazzo83 said:

DCA is 94/76 at 11am.  Absolutely brutal.

IAD 93/76 at 11am.

[pazzo83]

1 hour ago, MN Transplant said:

My annual warning for reading the 5-minute obs.  Because of rounding, a 5-minute reading of 99 could mean 98 or 99.  A reading of 100 is 100.

yep - gotta think in Celsius (bc of the backwards way they do the F -> C -> F conversion):
98.6 -> 37C
100.4 -> 38C
102.2 -> 39C
104 -> 40C
105.8 -> 41C

[Paleocene]

Mesonet picking up a DP of 79 with air temp 94 in college park.  cooking. "apparent temp" (is that heat index? @Eskimo Joe) 111!

 

@dailylurker are you doing a heat hike

[pazzo83]

1 hour ago, WxUSAF said:

Super hazy. 
 

But note that it’s sunny, hazy, hot and humid as shit, and we don’t have air quality alerts. Pollution control works! We should keep doing it!

yeah if this was back in the 90s, there'd be crazy alerts.

[MN Transplant]

I was assuming that we were looking at more of a 2024 or 2010 like heat where the focus wasn’t on the humidity, but this is damn near 2011.

[WxUSAF]

My son and I did 45 mins outside working on the deck. That was plenty. Shirt soaked in sweat.

[SolidIcewx]

1 minute ago, Paleocene said:

Mesonet picking up a DP of 79 with air temp 94 in college park.  cooking. "apparent temp" (is that heat index? @Eskimo Joe) 111!

Just north of there working. Can confirm. Its cooking and im already soaked lol

[dailylurker]

Already 97 in Crofton and 96 here east of Crofton in the woods. Wild DP and heat in the South River watershed. 

[pazzo83]

DCA at 95 now.

[Paleocene]

1 hour ago, WxUSAF said:

Super hazy. 
 

But note that it’s sunny, hazy, hot and humid as shit, and we don’t have air quality alerts. Pollution control works! We should keep doing it!

 

Hear hear - I work in urban planning so think about this stuff a lot. 2025 versus 1995 for the AQI... great visualization tool on this page  https://www.epa.gov/outdoor-air-quality-data/airdata-tile-plot (which I think I got off this site years ago). sorry for the digression..

 

 

 

edit - adding 1980 for fun - thanks clean air act

[pazzo83]

regional round up:
BOS at 91 (low of 78)
EWR is at 96 already lol (low of 82)
NYC at 94F (low of 82) - should be the first 100 there since the 2010s
LGA at 94F (low of 84) - the Queens/Brooklyn heat island is absolutely fierce.
PHL at 94F (low of 80)

This is a proper Acela corridor heat wave.

[Eskimo Joe]

7 minutes ago, Paleocene said:

Mesonet picking up a DP of 79 with air temp 94 in college park.  cooking. "apparent temp" (is that heat index? @Eskimo Joe) 111!

 

@dailylurker are you doing a heat hike

Yes apparent temp is a combo map. It's heat index when it's hot, wind chill when it's cold. All credit goes to @wxmeddler

[Eskimo Joe]

7 minutes ago, pazzo83 said:

regional round up:
BOS at 91 (low of 78)
EWR is at 96 already lol (low of 82)
NYC at 94F (low of 82) - should be the first 100 there since the 2010s
LGA at 94F (low of 84) - the Queens/Brooklyn heat island is absolutely fierce.
PHL at 94F (low of 80)

This is a proper Acela corridor heat wave.

NYC is the Central Park site, yes? The NYC subforum has been screeching for years about poor vegetation management on that location. For NCY to be 94° in essentially an over shaded, sheltered location at 11am bodes we for an upper 90s kind of day.

[LongRanger]

Would be nice to do pollution control without letting in more sun and heat.