033
FXUS65 KFGZ 051807
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1107 AM MST Wed Jun 5 2024

.SYNOPSIS...Much warmer temperatures and mainly dry conditions
are expected through Friday as high pressure builds over the
Southwest. There remains a slight chance for isolated
thunderstorms to develop Thursday afternoon with the likelihood of
dry lightning along the high terrain. Temperatures begin to cool
gradually for this weekend with the potential for additional
showers and thunderstorms.

&&

.DISCUSSION...Tranquil weather conditions are taking place across
northern Arizona as a high pressure ridge strengthens over much of
the western half of the country. High temperatures this afternoon
are forecast to be around 10 degrees above average, followed by
roughly 15 degrees above average for Thursday and Friday. This is
shaping up to be the warmest temperatures of the year so far and
taking place quite early in the summer season. Excessive Heat
Warnings remain in effect for Thursday and Friday for lower
valleys and canyons below 4000 feet. Much, if not all, of northern
Arizona will experience uncomfortable heat for the next two days.
Be prepared.

Global models show the ridge axis migrating eastward on Thursday,
resulting in a switch to light south to southeast flow. This flow
should allow for a slight increase in moisture advection in the
mid-levels with PWAT values near average (~0.50"-0.60") for this
time of year. Slight chances (15-20%) for isolated showers and
high-based thunderstorms remain in the forecast for Thursday
afternoon and evening, mainly confined to the Kaibab Plateau, San
Francisco Peaks, Mogollon Rim, and the White Mountains. Due to the
sufficient surface heating expected and lack of surface moisture,
any showers and/or thunderstorms that do develop over the high
terrain will likely be on the dry side with lightning and gusty
outflow winds (30-40 mph) being the main threats. The classic
"inverted-V" signature in various model soundings suggest this
potential for Thursday afternoon. With this in mind, new fire
starts will be possible. The good news is that outside of any
erratic outflows from storms, winds should generally be light,
10-20 mph, from the south and west on Thursday. Afternoon winds
thereafter are forecast to remain in the 10-20 mph range with
occasional gusts of up to 25 mph from the southwest. According to
both GEFS and EPS guidances, there are no strong wind events on
the horizon, which is good just in case there is an undetected
lighting fire start. Flow becomes more southwesterly on Friday
with moisture advection confined to the White Mountains and along
the AZ/NM border.

A slight cooling trend develops on Saturday with daytime highs
forecast 5-10 degrees above average, returning to near average
(within 5 degrees) on Sunday as geopotential heights decrease in
response to weakening high pressure and the potential for a low
pressure trough to move inland from the Baja coast. Isolated
showers and dry storms are forecast (15-30% chances) on Sunday as
the weak trough moves overhead from the southwest. Additional
chances are anticipated on Monday before drying out by mid-next
week. With that said, confidence continues to increase in another
warming and drying trend for the 8-14 day period. No indications
of any significant moisture to the region on the horizon at this
time.

&&

.AVIATION...Wednesday 05/18Z through Thursday 06/18Z...VFR
conditions continue through TAF period with generally light,
variable winds.

OUTLOOK...Thursday 06/18Z through Saturday 08/18Z...Expect VFR for
much of the outlook period. However, isolated -TS/-SHRA are possible
Thursday afternoon along and near a KGCN-KFLG-KJTC line, and again
Friday afternoon near KSOW-KSJN-KJTC. W-SW winds at 10-15 kts in the
afternoons with strong, gusty winds expected near storms. Light,
variable winds return overnight.

&&

.FIRE WEATHER...Thursday and Friday...Hot as daytime temperatures
will be 10 degrees or more above average. There is a slight chance
(10-25%) for showers/thunderstorms, mainly for higher terrain.
Expect dry lightning and gusty winds with most of these storms. Away
from storms, light west-southwest winds become a bit breezy Friday.
Look for minimum RH values between 5-15%.

Saturday through Monday...Temperatures cool this weekend into next
week. Slight chances (10-15%) for showers/thunderstorms remain for
eastern Arizona and along the Mogollon Rim with the best chances
(30-40%) near the White Mountains. West-southwest winds generally
at 10-20 mph. Minimum RH of 5-15% Saturday increases slightly to
10-20% Sunday and Monday.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...

Excessive Heat Warning from 10 AM MST /11 AM MDT/ Thursday to 8
PM MST /9 PM MDT/ Friday for AZZ005-006-037.

&&

$$

PUBLIC...LaGuardia
AVIATION...Mazon
FIRE WEATHER...Mazon

For Northern Arizona weather information visit
weather.gov/flagstaff