Severe Thunderstorm Warning 9, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
529 PM MDT Sat May 10 2025

Aviation Section Updated.

.KEY MESSAGES...

- Isolated thunderstorms this afternoon through early this
  evening will produce strong to severe wind gusts.

- On Sunday there will be showers and thunderstorms producing
  strong to severe wind gusts and small to large hail.

- On Monday it will be windy in Southwestern Montana with the
  strongest winds in north-south oriented valleys.

- Sunday evening through Wednesday there will be a series of
  upper-level disturbances that will bring lower-elevation rain
  and mountain snow.

&&

.DISCUSSION...
/Issued 250 PM MDT Sat May 10 2025/

 - Meteorological Overview:

This afternoon an upper-level ridge is over North-central, Central,
and Southwestern Montana. Due to an approaching upper-level trough
combined with warm daytime temperatures, there will be isolated
thunderstorms this afternoon through this evening across the area.
These thunderstorms will move quickly from the southwest to
northeast beginning this afternoon. The primarily threat from any
thunderstorm will be strong to severe winds. Little to no rainfall
is expected with these thunderstorms.

Sunday afternoon/evening a surface cold front associated with an
upper-level trough will begin to move through North-central,
Central, and Southwestern Montana. This will lead to widespread
showers and thunderstorms across the area on Sunday. Isolated
thunderstorms will produce strong to severe wind gusts and small
hail. The greatest risk for any severe thunderstorm will be east of
the continental divide. On Sunday due to the cold front temperatures
will be around 10 to 15 degrees colder across the area but still
above seasonal averages. On Sunday due to a strong surface pressure
gradient it will be windy in Southwestern Montana. However, any
stronger wind gust would be convectively driven. Sunday evening rain
will move into the Rocky Mountain Front and adjacent plains. Some of
the higher peaks along the Rocky Mountain Front will receive some
snow.

Monday through Wednesday the upper-level trough will remain over
North-central, Central, and Southwestern Montana. This will bring
daily rain chances to the area Monday through Wednesday with cooler
temperatures. On Monday due to a strong surface pressure gradient
and strong mid and upper-level winds it will be windy in
Southwestern Montana. On Thursday an upper-level ridge begins to
move over North-central, Central, and Southwestern Montana. This
will allow temperatures to warm up slightly and showers to gradually
end on Thursday. On Friday the upper-level ridge will remain over
the area this will allow the area to dry out with slightly warmer
temperatures.

 - Forecast Confidence & Scenarios:

There is a 15 - 30% chance for thunderstorms today across North-
central, Central, and Southwestern Montana. The Storm Prediction
Center (SPC) has a Marginal Risk for severe wind (5% chance for a
wind gust of 58 mph or greater within 25 miles of a point) today
across much of the area. There is a 20 - 40% chance for
thunderstorms tomorrow across North-central, Central, and
Southwestern Montana. The SPC has a Marginal Risk for severe wind
and hail (5% chance for a wind gust of 58 mph or greater and a 5%
chance for hail 1 inch or larger within 25 miles of a point) Sunday
across much of the area.

On Monday there is a 50 - 70% chance for wind gusts of 55 mph or
greater and a 30% chance for sustained winds of 40 mph or greater
south of I-90 in Southwestern Montana. As a result a High Wind Watch
was issued for Southwestern Montana south of I-90 except for
Northwestern Beaverhead County from 9 AM Monday to 6 PM Monday.

Sunday through Monday there is a 10 - 30% chance for a quarter inch
of rain or greater across North-central, Central, and Southwestern
Montana excluding the Rocky Mountain Front. Along the Rocky Mountain
Front Sunday through Monday there is a 50 - 70% chance for a quarter
inch of rain or greater. Tuesday through Thursday There is a 50 -
80% chance for a half inch of liquid precipitation or greater across
Central and Southwestern Montana and along the Rocky Mountain Front.
There is a 30 - 60% chance for a quarter inch of rain or greater
across the lower-elevations of North-central Montana. There is
greater than a 70% chance for 6 inches of snow or greater across the
mountains of Southwestern Montana Tuesday through Thursday. -IG

&&

.AVIATION...
11/00Z TAF Period

Outside of any thunderstorms VFR conditions will prevail during this
TAF period. Thunderstorms/outflow winds will affect the KBZN, KHLN,
KGTF, KHVR, and KLWT terminals for the next couple of hours. Any
thunderstorm will produce a brief heavy downpour, frequent
lightning, and wind gusts up to 58 mph. Between 11/18Z and the end
of this TAF period across all terminals there is a 30 - 50% chance
for showers and thunderstorms. These thunderstorms will produce
frequent lightning, a brief heavy downpour, wind gusts up to 58 mph,
and small hail. -IG

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  51  77  49  72 /  20  50  40  30
CTB  49  72  45  63 /  10  50  80  40
HLN  52  80  50  72 /  30  50  30  40
BZN  50  77  45  73 /  30  30  20  10
WYS  43  66  38  65 /  20  60  40  10
DLN  50  73  46  69 /  20  40  10  10
HVR  50  82  48  76 /  50  40  50  30
LWT  52  77  51  73 /  50  40  20  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Monday morning through Monday afternoon for
Beaverhead and Western Madison below 6000ft-Gallatin and Madison
County Mountains and Centennial Mountains-Madison River Valley-
Ruby Mountains and Southern Beaverhead Mountains.

&&

http://www.weather.gov/greatfalls

<!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>

<!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>