Arizona Snowbowl

000
FXUS65 KFGZ 211151
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
451 AM MST Wed Oct 21 2026

.SYNOPSIS...A very active period of weather is anticipated over
the next two days. A strong weather system is bringing widespread
showers and thunderstorms this morning, and will continuing 
through Thursday. The primary concerns are flooding and flash 
flooding, severe thunderstorms, and even a few tornadoes. Drier
conditions with lingering slight chances for showers are expected
by Friday into the weekend.

&&

.DISCUSSION...A concerning situation will evolve across Arizona 
over the next two days, with threats of flooding/flash flooding, 
severe thunderstorms, and tornadoes. A strong low pressure system 
off the California coast is beginning to move inland. This is well
positioned to carry a deep moisture surge of tropical and 
subtropical origins, as well as provide an ideal environment for 
severe weather. The low eventually lifts through the Great Basin 
on Thursday, dragging a cold front through the region late 
Thursday into Friday.

This morning...The first surge of tropical moisture has arrived, and 
activity is ramping up quickly early this morning. Current 
mesoanalysis shows a 50-55kt jet overhead at 500mb, as well as a 
strengthening southeasterly low-level jet advecting warm air and 
high dewpoints into northern AZ. This has allowed for increasing 
instability south of the Rim during the overnight hours, with MLCAPE 
values currently around 250-500 J/kg in Yavapai and Gila counties. 
Coupled with bulk shear around 50kts and storm relative helicity 100-
200 m2/s2, we are seeing scattered discrete supercell thunderstorms 
initiating along the terrain as of 2 AM MST. This is expected to 
decline in extent over the next few hours as conditions become 
slightly more unfavorable, however continued thunderstorms activity 
is expected especially further west. Severe thunderstorms bringing 1-
2 inch hail have remained the primary threat thus far. A secondary 
threat of flash flooding is also in play this morning given the 
arrival of deep moisture. However fast storm motion and scattered 
coverage will allow rain accumulations to likely remain below flash 
flooding concerns outside of sensitive burn scars.

Today through Thursday evening...Threats of flash flooding and 
severe thunderstorms continue through the period. For flooding, 
we will remain in a continuous fetch of deep tropical/subtropical 
moisture with modest instability and enhanced low-level flow. 
Precipitable Water (a measure of atmospheric moisture) will rise 
to 0.8-1.2 inches across most of our area. This is highly 
anomalous for mid-October. Despite the fast expected storm 
motion, periods of training or back-building storms are possible 
and could lead to locally heavy rainfall rates with flash flooding
concerns. Also several rounds of heavy rain are expected for 
most, and longer duration flooding of rivers, streams, normally 
dry washes, drainage basins, etc is possible. This is exacerbated
further by very saturated surface conditions for all of northern 
AZ. As a result, a Flood Watch will be in effect beginning at 5 AM
MST today and continuing through 11 PM MST Thursday. The threat 
of flooding ends on Thursday evening as a cold front sweeps from 
west to east and brings much drier air in its wake.

For the severe threat, an unstable environment with an impressive 
shear profile will be maintained through the period. The jet at 
500mb will continue to strengthen on Wednesday as the low pressure 
system slowly approaches. Despite cloud cover to limit 
destabilization, hi-res guidance remains adamant that CAPE values
up to 1000-1500 J/kg will develop by Wednesday afternoon with 
help from low-level moisture advection and steepening mid-level 
lapse rates. Several rounds of severe weather are possible, with 
the peak threat window beginning late Wednesday afternoon through 
evening. Stronger supercell storms will be capable of large 2+ 
inch hail, damaging wind gusts, and even a few tornadoes. SPC 
maintains an Enhanced risk (level 3 out of 5) of severe weather 
centered along the Mogollon Rim on Wednesday. Into Thursday, the 
severe threat looks to shift a bit further east towards the 
Eastern Mogollon Rim and White Mountains with potential for strong
storms along the propagating cold front. 

Be prepared and have a way to receive warnings!

Friday and onward...Activity is expected to trend downward by Friday 
into the weekend after the main trough axis pushes past Northern AZ 
and drier air moves in. A closed low may linger across western AZ, 
and slight chances for showers and thunderstorms remain in the 
forecast each day. Expect lighter winds and temperatures remaining 
below normal otherwise.

&&

.AVIATION...Wednesday 21/12Z through Thursday 22/12Z...Scattered 
to numerous showers and thunderstorms this morning, becoming
widespread by the mid-to-late afternoon. Drops to MVFR/IFR, 
especially near heavier showers or thunderstorms. Occasional 
severe storms with large hail or damaging wind are expected. 
Gusty and erratic winds near thunderstorms, else winds are SE-S 
10-20kts gusting to 30 kts after 18Z Wednesday. 


OUTLOOK...Thursday 22/12Z through Saturday 24/12Z...Periods of 
widespread showers and thunderstorms continue Thursday, then activity
diminishes from west to east late Thursday night. Some severe 
storms with large hail or damaging winds expected. Drops to 
MVFR/IFR, especially near heavier showers or thunderstorms. Much
drier by Friday, with slight chances for lingering showers. Winds
S-SW 10-20 kts with gusts to 30 kts Thursday, SW-W 10-20kts 
Friday. Gusty and erratic winds near storms.

&&

.FIRE WEATHER...This morning through Thursday...Increasing showers 
and thunderstorms this morning becoming widespread on Wednesday and 
Thursday. Some storms may produce very heavy rainfall leading to 
flooding or flash flooding both days. Some stronger storms may 
produce strong winds and large hail. Outside of storms, expect south 
winds 10-20 mph with gusts 30-40 mph on Wednesday, becoming south 
through southwest on Thursday. Daytime temperatures near to below 
normal.

Friday through Sunday...Isolated showers and thunderstorms are 
expected for Friday through Sunday. Southwest through west winds 10-
15 mph with gusts to 25 mph on Friday, then light northerly winds 5-
15 mph on Saturday and Sunday.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Thursday evening for AZZ004>018-037>040.

&&

$$

PUBLIC...Lewandowski
AVIATION...Lewandowski
FIRE WEATHER...Lewandowski

For Northern Arizona weather information visit
weather.gov/flagstaff