Severe Thunderstorm Warning 99, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
350 PM MDT Sun Jul 24 2022

.SHORT TERM...(This evening through Monday)
Issued at 350 PM MDT Sun Jul 24 2022

Current radar pictures are showing quite a convergence line
with thunderstorms stretched along what had been the Denver
Cyclone boundary from Morgan County to southern Douglas County.
Elsewhere, convection has and is developing over the foothills,
Summit and Park Counties. The convection is moving north-
northeastward. Low level moisture is good with dew point readings
in the 50s to lower 60s F for all the CWA, even the high country.

Current forecast looks pretty good, will keep pops "likely" for
much of the CWA into the evening. Moisture over the forecast will
remain abundant for the first period. Heavy rainfall is a good
bet and well as flash flooding, certainly in the alpine burn
areas. The convection is expected to taper off from west to east
through the evening. There may some lingering over the eastern
and southern CWA border areas past midnight.

On Monday, the upper ridge builds back to the west a bit and there
will be weak west-southwesterly flow aloft.  There is little
synoptic scale energy on the QG Omega fields. The main change
will be a moisture decrease for the CWA. The precipitable water
fields show moisture to decrease, especially over the
northwestern half of the CWA and in the lower levels of all the
forecast area. Surface dew points are progged to be 15-25 F less
than today over some areas. The QPF fields have a bit of
measurable rainfall for the southern third of the CWA late day
Monday; but that's it. Will go with way less pops on Monday.
Monday's high temperatures look to be 1-4 C warmer than today's
highs.

.LONG TERM...(Monday night through Sunday)
Issued at 252 PM MDT Sun Jul 24 2022

Drier air will remain over the western slope on Tuesday, with some
increase of low level moisture east of the mountains. Afternoon
convection will likely be mainly over the east slopes, though it
could progress onto the plains into the low level moisture
advection by evening. Wednesday is probably still similar, though
the moisture could be better east of the Divide. If so, there
could be more of a flash flood threat for the Front Range burn
areas on this day as the steering winds will still be light and
the low level convergence could provide some anchoring or
redevelopment along the foothills.

There's still some disagreement of the timing and structure of a
weak short wave and its associated cold front late Wednesday into
early Thursday. This could cut into the high temperatures
Wednesday afternoon if it's fast enough, but probably not. It's
also probably doesn't provide enough cooling to kill convection
behind it on Thursday, especially since there will probably be a
little cooling aloft and maybe even more low level moisture.
There's been some convergence towards an intermediate solution on
how much the ridge pushes eastward over our area on Friday. This
is pretty favorable for convection again, with slight drying
bringing some surface heating but still a fair amount of moisture
as well. We'll carry pretty high PoPs for Thursday and Friday as
there's not much to stop the diurnal convection. The main question
is the timing of how much there will be on the plains in the
afternoon and how late it will continue into the night.

Another shortwave in the northwesterly flow over the northern
plains should bring some drier air aloft in from the west.
Heights/temperatures aloft will build a bit behind this as well.
This should bring less convection and warmer temperatures over the
weekend. The forecast temps throughout the period look reasonable,
with the middle of the ensemble range in the later periods also
looking good.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 1155 AM MDT Sun Jul 24 2022

The center of the Denver Cyclone looks to be just east of the
airport at this time. Models show pretty weak winds the rest of
the afternoon. Northeasterlies seem to be the best chance for
direction right now. Winds may eventually become more south-
 later this evening and not true drainage direction overnight.
The showers and thunderstorms are still a good bet after 20Z this
afternoon. WInd gusts to 35 knots are also possible. As far as
ceilings go, there could be some BKN040 this afternoon with the
thunderstorms. After 10Z tonight, some models indicate low
ceilings below BKN010 and visibilities 2SM BR for a 3 or 4 hours
until 15Z Monday morning.

&&

.HYDROLOGY...
Issued at 252 PM MDT Sun Jul 24 2022

Heavy rainfall will continue to be a threat late this afternoon
and evening for much of the CWA. Rainfall rates of 1.5 inches per
half hour can be expected with the strongest storms. The threat
of flash flood is significant for the CWA and over the burn
areas. On Monday, there will be little threat of burn area flash
flooding.

For Tuesday and Wednesday, there will be a bit more moisture with
the storm threat focused on the east side of the Front Range.
Slow storm motions are possible on these days so there will be
some increase in the flood threat. For Thursday and Friday, some
increase in storm activity is expected but faster storm motions
are also expected so a limited flood threat is expected. Some
drying will bring decreasing storm activity for the weekend,
though at least isolated storms with a small burn area flood
threat are still expected.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Flood Watch until midnight MDT tonight for COZ041-046-047-049.

Flash Flood Watch until midnight MDT tonight for COZ030-032>035.

&&

SHORT TERM...RJK
LONG TERM....Gimmestad
AVIATION.....RJK
HYDROLOGY....RJK/Gimmestad

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1057 AM MDT Sun Jul 24 2022

COZ030>051-251700-
Jackson County Below 9000 Feet-
West Jackson and West Grand Counties Above 9000 Feet-
Grand and Summit Counties Below 9000 Feet-
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Central and Southeast Park County-
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Northeast Weld County-Central and South Weld County-Morgan County-
Central and East Adams and Arapahoe Counties-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County-
Southeast Elbert County Below 6000 Feet/South Lincoln County-
Logan County-Washington County-Sedgwick County-Phillips County-
1057 AM MDT Sun Jul 24 2022

...FLASH FLOOD WATCH THIS AFTERNOON AND EVENING FOR THE RECENT
BURN AREAS, PALMER DIVIDE, AND ADJACENT PLAINS OF EAST CENTRAL
COLORADO...

This hazardous weather outlook is for northeast and north central
Colorado.

.DAY ONE...Today and Tonight

There is a threat of flash flooding this afternoon and evening
for the recent burn areas in the mountains and foothills, as well
as locations from the Palmer Divide east and northeast across
East Central Colorado.

The thunderstorms in the mountains will be capable of producing up
to 1.5 inches of rain in 30 minutes. If one of those stronger
storms moves over a burn area, significant flash flooding can be
expected.  On the plains, stronger thunderstorms are expected to
develop by mid to late afternoon. The stronger storms will be more
numerous over the Palmer Divide and points eastward, and be
capable of producing torrential rainfall on the order of 2-3
inches in an hour. Even portions of the Denver metro area and I-25
Corridor could see heavy rain and street flooding.

Stay weather aware today and be ready to take action. The storms
will decrease through the evening hours, with tranquil weather but
patchy fog expected overnight.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Monday and Tuesday will be warmer and drier, but there will still
be a chance of afternoon and evening thunderstorms both days. The
threat of flash flooding in the burn areas will be limited. The
rest of the week will be cooler again with a better chance of
showers and thunderstorms.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight. However,
any reports of heavy rainfall or flooding will be appreciated.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
402 PM MDT SUN JUL 24 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0329 PM     FLASH FLOOD      3 SSW BUCKHORN MOUNTAIN 40.57N 105.35W
07/24/2022                   LARIMER            CO   EMERGENCY MNGR

            SHEEP CREEK HAS OVERTOPPED 44H.

&&

AD

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
406 PM MDT SUN JUL 24 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0329 PM     HEAVY RAIN       4 SSE GLEN HAVEN        40.41N 105.41W
07/24/2022  M0.94 INCH       LARIMER            CO   PUBLIC

            SLEEPY HOLLOW RAIN GAUGE IN BIG THOMPSON
            CANYON.

&&

AD

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>