Special Weather Statement, NWS Phoenix, AZ

Area Forecast Discussion
National Weather Service Phoenix AZ
543 AM MST Sun Oct 7 2018

.UPDATE...Updated aviation discussions.

&&

.SYNOPSIS...
A Pacific weather system will bring good chances for showers and
thunderstorms over central and eastern portions of Arizona today
with lingering chances into Monday. Cooler temperatures are
expected behind this system with afternoon highs struggling to get
out of the 70s through Tuesday. Temperatures will remain below
normal for all of next week with precipitation chances returning
late Thursday and Friday as remnants of Hurricane Sergio possibly
affects our area.

&&

.DISCUSSION...

An unseasonably strong upper level trough of low pressure is
currently digging down the West Coast this morning and is aided by a
120 kt northerly jet (at 250 mb) that extends from Washington
down through Northern California. This trough can clearly be seen
in water vapor imagery with thunderstorms firing off along a
trailing surface cold front. As expected, storm motion has been
parallel to the front early this morning which has caused some
training of storms and nuisance flooding in northern La Paz and
Maricopa Counties. We are expecting this sort of training to
continue throughout the morning which could bring flash flooding
to localized areas, especially those places in favorable upslope
flow. Subsequently we will continue the Flash Flood Watch for
northern Maricopa and portions of Gila County. Finally, a large
amount of shear exists along this front which will create an
environment conducive to rotating storms. This could produce
severe storms and perhaps a brief funnel cloud on the northern
edge of our CWA but given the time of day, expecting this to be
isolated.

The aforementioned front will continue to progress eastward today
and will push through the Phoenix metro between 9 and 13 UTC and
into Gila County by late morning. The best precipitation chances
today will be associated with this front although post frontal
showers will bring another shot of precipitation to south-central
Arizona this afternoon. Additionally, cooler air will filter in
behind this front bringing high temperatures down into the 70s
this afternoon for the lower elevations of south-central Arizona
with 80s in SE California.

This trough will be slow to exit our area which means showers and
storms, mainly for the higher elevations, will linger into Monday.
A gradual warming trend is then forecast for Tuesday and Wednesday
as the trough kicks out and the airmass modifies under the early
October sun. Despite the warming, daytime highs and overnight
lows will still be 5 to 10 degrees below average.

Much uncertainty exists for Thursday and Friday as the remnants of
what is currently Hurricane Sergio moves towards our area. Latest
ensembles still track the remnants through far southeast Arizona
but matters are complicated as the moisture interacts with a
trough passing by late next week. Over the past several days the
GEFS has significantly trended down on precipitation amounts over
Phoenix with only a quarter of an inch falling over the metro
Thursday and Friday with even less over Yuma. However, a shift in
the track, notably to the north, would bring substantially more
rain and a widespread flash flooding risk. At this point, it is
still too early to discount widespread impacts over our CWA from
this passing tropical system but chances are becoming less likely
with each passing model run. For now, please stay tuned to the
forecast as we iron out the details which will hopefully become
more clear in the coming days.

&&

.AVIATION...

South-Central Arizona including KPHX, KIWA, and KSDL:

A cold front associated with a strong area of low pressure is
currently moving through the terminals bringing periods of heavy
rain and low visibility. The back edge of this precipitation band
will be out of all TAF sties by 8 am with ceilings improving
rapidly behind. Daytime heating combined with low level moisture
may be enough to generate another round of showers and
thunderstorms this afternoon but would be rather isolated in
nature. Because of this, have left the mention of additional
showers/storms out of the TAF.

Southeast California/Southwest Arizona including KIPL and KBLH:

West to northwest flow will dominate at both TAF sites today with
gusts around 20 to 25 kts this afternoon at both KIPL and KBLH.
Lingering moisture combined with daytime heating could be enough
to generate a shower or storm at KBLH today but confidence is low
enough to exclude it from the TAF. Other than this, expect FEW to
BKN cumulus to develop this afternoon around 10 kft.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday:
Expect below normal temperatures and few fire weather concerns
through the period. Drier conditions on Tuesday will be replaced
by an increasing moisture trend starting Wednesday. Remnants of
what is currently Hurricane Rosa will bring an elevated chance of
precipitation Thursday afternoon through Friday but the track is
still somewhat uncertain. Currently, Pinal and southern Gila
Counties have about a 50% shot at seeing a wetting rain with much
lower chances elsewhere. Throughout the period winds will be
rather light with the exception of some breezes in southeast
California during Wednesday and Friday afternoon.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flash Flood Watch through this afternoon for AZZ541-545-547-556-
     557.

CA...Wind Advisory until 8 AM PDT this morning for CAZ560-562.

&&

DISCUSSION...Wilson
AVIATION...Wilson
FIRE WEATHER...Wilson/Sawtelle

<!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>