Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 181704

Area Forecast Discussion
National Weather Service Flagstaff AZ
1004 AM MST Sun Jun 18 2017

.SYNOPSIS...An Excessive Heat Warning is in effect for the lower
elevations of Yavapai, Coconino and northern Gila counties
through Thursday, with a Heat Advisory for the remainder of
Coconino, Yavapai, Navajo, and Apache counties. Isolated showers
or thunderstorms with gusty winds could develop over the higher
terrain from Flagstaff eastward each afternoon through Tuesday.


The current short-term forecast of hot temps and a slight chance
of dry thunderstorms over the mountains looks in good shape with
no significant updates anticipated this morning.


.PREV DISCUSSION /304 AM MST/...Forecasts for record or near
record high temperatures remain on track with Excessive Heat
Warnings at lower elevations and Heat Advisories at higher
elevations through Thursday. Only minor changes have been made to
the forecast with this morning`s package. Limited moisture
filtering in from the north combined with very strong surface
heating will lead to some cloud buildups later this afternoon over
the higher terrain. A slight chance of some dry thunderstorms was
added to the forecast for this afternoon for the Mogollon Rim and
White Mountains including the Flagstaff area. Any storms that
develop will be capable of gusty winds but little if any rain. By
Monday and Tuesday, this moisture becomes a bit more pronounced
over the higher terrain from Flagstaff eastward, and the chance of
showers & thunderstorms was increased into the 20-30 percent
range. Gusty winds and the threat of new fire starts with
lightning will be the main concerns with this activity. Still
thinking our forecast high temperatures are on track even with the
increased cloud cover at higher elevations, since these highs are
likely to be reached just before clouds/storms begin to form.
Toward the end of the week and the weekend, most model guidance
indicates the strong ridge shifting southward into northern
Mexico, with temperatures a few degrees lower for northern
Arizona, though still above normal.


.AVIATION...For the 18Z package...Isolated thunderstorms are
possible over high terrain areas this afternoon, which would be
capable of producing very strong wind gusts/downdrafts. Smoke from
area wildfires may briefly cause MVFR visibility near the ground,
especially overnight. Smoke may also affect flight paths.
Otherwise, VFR conditions are expected to persist for the next
twenty-four hours. Aviation discussion not updated for TAF


.FIRE WEATHER...Hot temperatures with afternoon RH in the single
digits and teens are expected today and Monday. High Haines
indices will promote rapid fire growth. There is a slight chance
of thunderstorms over the higher terrain this afternoon and Monday
afternoon. Any storms that do develop would produce minimal
rainfall with strong gusty winds.

Tuesday through Thursday...Thunderstorms producing gusty winds
will once again be possible on Tuesday. A few storms may occur
on Wednesday and Thursday. Hot temperatures, high Haines indices,
and low RH values will persist. Breezy southwest to west winds are
expected Wednesday and Thursday afternoons.


Thursday FOR AZZ004-007>017-039-040.

Excessive Heat Warning until 8 PM MST Thursday FOR




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