125
FXUS65 KFGZ 200920
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
220 AM MST Thu Jun 20 2024

.SYNOPSIS...Daily chances for showers and thunderstorms are
forecast through the weekend and into early next week, along with
warming temperatures.

&&

.DISCUSSION...Today...A large area of high pressure sits over the
eastern-half of the United States, with a trough situated over
much of the west. Meanwhile, Tropical Storm Alberto is approaching
the eastern coast of Texas and Mexico. As Alberto moves across
Mexico, the trough over the west begins to lift northward and the
ridge begins to retrograde. As a a result, a surge of sub-tropical
moisture is initiated into Arizona.

Surface dewpoints have already begun to rise into the 50s F and 60s
F across much of New Mexico and into far eastern Arizona, as the
moisture begins to inch closer to Arizona. PWATs look to rise to
around 0.75-1.00 inches over Arizona by this afternoon, well above
the 90th percentile for this point in the year. 00Z HREF guidances
shows strong support for destabilization later this afternoon,
with 700-1200 J/Kg of surface-based CAPE. 0-6km shear is a bit on
the lower-end but with the influence of the trough, areas across
northern Arizona could potentially see a few stronger
thunderstorms with 25-35 kts of shear.

Latest CAM guidance has the bulk of the activity this afternoon north
of a Grand Canyon to St. Johns line, with lesser coverage along the
Mogollon Rim as well. The greatest threat from this storms will be
gusty outflow winds, brief heavy downpours, and small hail. However,
a couple strong to severe thunderstorms can not be ruled out.

Friday...The greatest moisture looks to move in on Friday, with PWAT
values of around an inch for much of northern Arizona to upwards of
1.2 inches in the Lower Deserts. Even with the increased moisture,
coverage still looks best over northern and eastern Arizona during
the afternoon on Friday, and to a lesser extent over central Arizona.

HREF and CAM guidance does show an increase in 0-6 km shear as the
trough lifts northward. Thus, the threat for a couple of stronger
thunderstorms remains. Localized flash flooding will also remain
a possibility through the Four Corners region given the amount of
moisture available, however storm motions of 20-25 kts may limit
the residency time of any one storm.

Saturday into Next Week...By the weekend the ridge has shifted full
into New Mexico, moisture remains in place, keeping daily chances
for showers and thunderstorms in the forecast. However, as the
heights continue to rise with the ridge building into the Southwest,
temperatures begin to warm once again for the start of next week.
Coverage and intensity of showers and thunderstorms may begin to
wain into next week as subsidence increases aloft.

&&

.AVIATION...Thursday 20/06Z through Friday 21/06Z...VFR conditions
will persist through much of the TAF period, but periods of MVFR
conditions are likely after 18Z due to SHRA/TSRA. Greatest chances
for showers/thunderstorms will be along and east of a KPGA-KPAN
line. Gusty and erratic winds will be possible near thunderstorms,
with S-SW winds 15-25 kts expected otherwise.

OUTLOOK...Friday 21/06Z through Sunday 23/06Z...Look for
continuous periods of SHRA/TSRA through the outlook period. VFR
conditions will prevail outside of brief MVFR conditions in
heavier storms. Gusty outflow winds will be possible, but S-SW
winds 10-20 kts are forecast for Friday before becoming lighter on
Saturday.

&&

.FIRE WEATHER...Today and Friday...Increasing chances for
showers/thunderstorms from east to west today and Friday. South to
southwest winds 15-25 mph, with gusty and erratic winds in the
vicinity of storms. Increasing RH values from 15-30% today to 30-50%
on Friday.

Saturday through Monday...Chances for showers and thunderstorms each
day. South to southwest winds around 5 to 10 mph Saturday and Sunday
becoming more westerly at 5 to 15 mph Monday. Gusty and erratic
winds possible in the vicinity of storms. Decreasing moisture will
result in lower RH values, generally between 20-30%.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

PUBLIC...Humphreys
AVIATION...Konieczny
FIRE WEATHER...Meola

For Northern Arizona weather information visit
weather.gov/flagstaff