FXUS65 KFGZ 250434

Area Forecast Discussion
National Weather Service Flagstaff AZ
934 PM MST Sat Aug 24 2019

.SYNOPSIS...A warming trend will begin on Sunday and persist into
the early portion of the work week next week with dry conditions
continuing for much of the region. Moisture will gradually return
to the area starting in the mid-week. This increase in monsoonal
moisture could help to bring a return of showers and thunderstorms
to the area.


.UPDATE...Dewpoints have increased across portions of the
higher terrain from Flagstaff and southeastward along the
Mogollon Rim to Springerville. Surface dewpoints in these
portions of the High Country range from the low to mid-fifties
currently. As overnight temperatures continue to decrease towards
the elevated dewpoints, be sure to keep an eye out for any
patchy fog that could form. Any patchy fog formation would likely
be in the early morning hours on Sunday. Confidence is on the
lower end for patchy fog formation, so it was kept out of the
weather grids with the evening forecast update.

The isolated thunderstorms from earlier this evening have either
diminished in coverage or moved out of the County Warning Area.
This change in storm coverage over the southern portions of the
CWA prompted a reduction in the chances of precipitation and an
increase in sky cover over the next few hours. A warming trend is
still expected to begin tomorrow afternoon and last into the early
part of the work week.


.PREV DISCUSSION /251 PM MST/...Short Term (Saturday through
Monday)...Low level moisture has pushed into the southern part of
the area with dewpoints in the 60's across Gila and southern
Yavapai Counties. A fairly strong subsidence cap over the area
will discourage most convection, but the strong daytime heating
will be enough to break the inversion along the Mogollon Rim. We
are seeing some activity already south of Prescott, east of Forest
Lakes and over the White Mountains. A high pressure to our west
off the California coast will keep northern Arizona in a
northerly dry flow through Monday, decreasing our chances for
thunderstorms Sunday and Monday. The question is whether the
moisture just below the Mogollon Rim will push off to the south or
stay in place. The current forecast is for it to move south with
the flow around the high to give us dry conditions. But if the
moisture stays in place, we can expect isolated thunderstorms
again Sunday afternoon and Monday. Currently forecasting isolated
thunderstorms this afternoon along and south of the Mogollon Rim
due to the available low-level moisture, with that moisture
diminishing Sunday and Monday. Stay tuned to see how it turns
out. Otherwise, expect mostly clear skies with cool morning and
very warm afternoon temperatures into Tuesday across northern

Long term (Tuesday through Saturday)...Temperatures are expected
to peak on Tuesday as very warm air aloft is centered over
northern Arizona. Expect daytime temperatures around 10 degrees
above normal, similar to what we have seen in our hot days over
the past couple weeks. Excessive heat products may be necessary on
Tuesday, especially across the lower elevations of Yavapai County
and the Grand Canyon. We did lower the highs a degree or two along
the higher terrain Tuesday as it looks like enough mid level
moisture will be in place for a fair bit of cumulus development in
the afternoon. This may keep temperatures from reaching their full
potential. Regardless, it will still be very warm. Be sure to
drink plenty of fluids and delay any outdoor activity to the
cooler times of the day if at all possible. A gradual cooling
trend is expected through the rest of the week as monsoonal
moisture slowly returns.

Moisture begins to gradually return around mid-week and this will
continue through Labor Day weekend. The returning moisture will
bring a few high-based showers and storms over the higher terrain
on Tuesday, with chances increasing and becoming more widespread
through the second half of the week. Latest operational models and
ensemble guidance indicate a decent monsoon pattern setting up
Friday and into Labor Day weekend as high pressure shifts
northward. While confidence is tampered a bit based on how the
season has gone so far, this does show promising signs in bringing
some much needed rainfall to northern Arizona.


.AVIATION...For the 06Z package...VFR conditions will prevail over
the next 24 hours. Smoke from area wildfires may be present in
spots, but significant impacts are not anticipated. Surface
dewpoints have risen and may cause patchy fog from 10-14Z.
Isolated showers and thunderstorms 20-24Z over the White
Mountains, otherwise dry. Aviation discussion not updated for TAF


.FIRE WEATHER...Breezy afternoon winds can be expected this weekend.
Isolated showers and thunderstorms over the White Mountains Sunday
and Monday...otherwise hot and dry.

.Tuesday through Thursday...Expect increasing chances of showers
through the period. Near record high temperatures will be possible






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