Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 191024
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
324 AM MST Mon Jun 19 2017

.SYNOPSIS...Hot conditions will continue through much of the week.
Isolated to scattered showers or thunderstorms with gusty winds
could develop each afternoon through Tuesday over the higher
terrain, mainly from Flagstaff eastward.

&&

.DISCUSSION...The moisture increase on Sunday (dewpoints in the
30s vs sub-zero values a day or two before) led to some isolated
high-based thunderstorms during peak heating along the Mogollon
Rim and White Mountains. High cloud bases and hot sub-cloud
layers with these storms caused gusty outflow winds, with a couple
reports of 50 mph gusts. This pattern remains in place today and
Tuesday, with slightly higher amounts of moisture expected to lead
to an increase in shower/storm coverage. A slight chance of
showers or storms was added to the forecast farther west and
north, including Grand Canyon/Kaibab Plateau, the Prescott area,
and Gila County for this afternoon. Gusty winds and lightning
(with new fire starts possible) will be the main storm threats
today and Tuesday. Even with this moisture, extreme heat will
continue to be the big story with Excessive Heat Warnings at lower
elevations and Heat Advisories for higher elevations all the way
through Thursday. Higher elevation areas where clouds develop
first should still be able to reach their forecast high
temperatures. Wednesday could end up being the hottest day as
moisture decreases. Several locations are forecast to reach
within a few degrees of all-time record highs. Model guidance
continues to indicate the ridge shifting south of the area late in
the week and the weekend, allowing temperatures to drop a few
degrees (though remaining well above normal).

&&

.AVIATION...For the 12Z package...Isolated to scattered
thunderstorms are expected to develop over high terrain 18Z-02Z. Any
storm will be capable of producing strong wind gusts/downdrafts to
40-45kts. Smoke from area wildfires may briefly cause MVFR
visibility near the ground, especially overnight.  Smoke may also
affect flight paths. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Scattered thunderstorms with little rainfall and
the potential for very strong wind gusts are expected to develop
over the high terrain areas of northern Arizona today and Tuesday.
Temperatures will become a few degrees hotter, intensifying the risk
for heat illness to wildland firefighters. Low surface humidity will
persist.

Wednesday through Friday...The chances for thunderstorms is expected
to decrease through the end of the week. Record daily to all time
record high temperatures are possible on Wednesday before
temperatures slowly begin to decrease late this week. Expect breezy
southwest to west winds each afternoon.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Heat Advisory until 8 PM MST
Thursday FOR AZZ004-007>017-039-040.

Excessive Heat Warning until 8 PM MST Thursday FOR AZZ005-006-
018-037-038.

&&

$$

PUBLIC...JJ
AVIATION...MAS
FIRE WEATHER...MAS

For Northern Arizona weather information visit
weather.gov/flagstaff



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