WW 689 SEVERE TSTM AZ 212035Z - 220400Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 689
NWS Storm Prediction Center Norman OK
135 PM MST Wed Oct 21 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Central and Southern Arizona
* Effective this Wednesday afternoon and evening from 135 PM
until 900 PM MST.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Scattered damaging wind gusts to 70 mph possible
A tornado or two possible
SUMMARY...Thunderstorm coverage is expected to increase this
afternoon and evening across portions of central and southern
Arizona. Recent sounding from PHX sampled an unstable and strongly
sheared environment supportive of supercells. Primary hazards with
these storms are large hail and strong gusts. Isolated very large
hail (i.e. 2"+ in diameter) and a brief tornado could also occur.
The severe thunderstorm watch area is approximately along and 55
statute miles north and south of a line from 55 miles northwest of
Gila Bend AZ to 35 miles east of Safford AZ. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU9).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 688...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
21035.
...Mosier
WW 688 TORNADO AZ 211700Z - 220100Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 688
NWS Storm Prediction Center Norman OK
1000 AM MST Wed Oct 21 2026
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
Northern and Central Arizona
* Effective this Wednesday morning and evening from 1000 AM until
600 PM MST.
* Primary threats include...
A few tornadoes possible
Scattered large hail and isolated very large hail events to 2.5
inches in diameter likely
Scattered damaging wind gusts to 70 mph possible
SUMMARY...Thunderstorm coverage is expected to increase across
northern and central Arizona this afternoon. Strong vertical shear
will support supercells thunderstorms capable of all severe hazards,
including 2"+ diameter hail and tornadoes. The threat for severe
weather will persist throughout the afternoon and into the evening.
The tornado watch area is approximately along and 70 statute miles
north and south of a line from 95 miles west of Grand Canyon AZ to
45 miles east of Winslow AZ. For a complete depiction of the watch
see the associated watch outline update (WOUS64 KWNS WOU8).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.
&&
AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 2.5 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean
storm motion vector 22035.
...Mosier
WW 0689 Status Updates
STATUS FOR WATCH 0689 HAS NOT BEEN ISSUED YET
WW 0688 Status Updates
STATUS REPORT ON WW 688
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 2388
..WEINMAN..10/21/26
ATTN...WFO...FGZ...VEF...
STATUS REPORT FOR WT 688
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
AZC005-015-017-025-212140-
AZ
. ARIZONA COUNTIES INCLUDED ARE
COCONINO MOHAVE NAVAJO
YAVAPAI
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
MD 2389 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR NORTHWESTERN NEW MEXICO
Mesoscale Discussion 2389
NWS Storm Prediction Center Norman OK
0441 PM CDT Wed Oct 21 2026
Areas affected...northwestern New Mexico
Concerning...Severe potential...Watch unlikely
Valid 212141Z - 220015Z
Probability of Watch Issuance...20 percent
SUMMARY...Storms are expected to increase in coverage and intensity
through the afternoon across northwestern New Mexico. The strongest
storms will be capable of producing large hail and damaging winds,
but the severe coverage is expected to be too isolated to warrant a
watch.
DISCUSSION...Surface heating throughout the day has resulted in
modest destabilization across western New Mexico. As a result,
thunderstorms have developed over the area and will continue to
increase in coverage and intensity over the next few hours as they
move to the northeast. While low-level moisture (low 50s surface
dewpoints) is limiting instability and updraft strength, deep-layer
shear is sufficient to support organized updrafts, including
supercell structures. The strongest and longest-lived updrafts will
be capable of producing large hail and strong wind gusts, but the
overall threat is expected to remain too isolated for a watch.
..Jirak/Smith.. 10/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ABQ...FGZ...
LAT...LON 34690912 35730915 36340893 36700828 36940766 36960674
36020647 35480652 34850688 34340725 34000816 34120867
34690912
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Wed Oct 21 2026
Valid 212000Z - 221200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL ARIZONA...
...SUMMARY...
Severe thunderstorms capable of producing large hail, a few
tornadoes, and damaging winds remain possible today and tonight
across parts of Arizona and vicinity. Isolated severe gusts and
perhaps a tornado may also occur along the central/southern
California Coast.
...20z Update...
No changes were made to the existing outlook with this update as the
forecast remains generally on track. Convective activity/severe
potential is generally expected to peak this afternoon/early evening
coincident with peak diurnal heating/destabilization. However,
additional rounds of thunderstorm development and the potential for
supercells capable of primarily large hail are likely to continue
into the late evening/overnight hours, especially across
central/northern Arizona, amid a continuing southerly, warm-air
advection regime. See MCDs #2387 and #2388 along with the discussion
below for additional short-term details.
..Chalmers.. 10/21/2026
.PREV DISCUSSION... /ISSUED 1122 AM CDT Wed Oct 21 2026/
...Southwest...
Recent satellite imagery continues to show deep southwesterly flow
aloft from the central Baja Peninsula through AZ and the Four
Corners region. Warm-air advection associated with this
southwesterly flow aloft has contributed to showers and
thunderstorms across central/northern AZ this morning. The low-level
airmass here is still relatively cool and stable, but strong
vertical shear has still resulted in several supercells. As
mentioned in MCD #2385, additional/isolated thunderstorms are
possible within this low-midlevel moisture plume, potentially aided
by embedded speed maxima moving north-northeastward. Strong vertical
shear will persist as well, suggesting several of these storms could
become supercellular. Large hail will remain the primary risk until
the low levels destabilize.
Deep cyclone off the central/southern CA coast is forecast to
gradually shift east-southeastward today. As it does, southwesterly
flow aloft within its eastern periphery will strengthen, with
deep-layer vertical shear across AZ also strengthening in response.
Low-level moisture will advect northward as well. Even with
widespread cloudiness, this increased moisture combined with
filtered daytime heating will support gradual airmass
destabilization and the development of up to 1000-1500 J/kg of
MLCAPE across this region. Strongest buoyancy is anticipated in
south-central AZ.
Forcing for ascent will increase in tandem with airmass
destabilization and the general expectation is for increasing
thunderstorm coverage along and just south/west of the Mogollon Rim
this afternoon. Supercell wind profiles are in place, and large to
isolated very large hail (i.e. 2"+ in diameter) is expected to be
the primary hazard. However, storm motion will take these storms
north-northeastward, potentially interacting with the more
southeasterly low-level flow along/near the Rim. Resulting increase
in low-level shear will support an increased tornado potential. This
potential will be maximized from northwest into central AZ this
afternoon and early evening, but low-probability tornado potential
will extend to the southern AZ/NM border. Strong wind gusts are
possible as well, particularly from central into southeast AZ where
relatively stronger heating/mixing is possible.
Tornado threat is expected to diminish gradually with the loss of
daytime heating, but thunderstorms will likely persist throughout
the evening and overnight. Large hail will remain possible with this
overnight activity.
...Coastal Central/Southern California...
The large cyclone over the eastern Pacific will approach the
central CA Coast through the period, with a belt of strong southerly
flow at mid levels expected to overspread coastal central/southern
CA through the day. A low-topped line of convection may develop in
response and impact this region during the afternoon/evening.
Limited instability is forecast, and updrafts may struggle to reach
sufficient depth for charge separation and lightning production.
Even so, given modestly enhanced flow and low-level shear, an
isolated risk for severe gusts and perhaps a tornado may exist as
this convection moves onshore.
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0213 PM CDT Wed Oct 21 2026
Valid 231200Z - 241200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL NEW MEXICO...
...SUMMARY...
Isolated severe thunderstorms are possible across portions of
central into southern New Mexico on Friday.
...New Mexico...
Steady mid-level height falls are expected across the Southwest in
the wake of a departing shortwave trough. Low-level moisture will be
maintained on the western edge of an expansive eastern surface
ridge. Sufficient surface heating will allow 500-1500 J/kg MLCAPE to
develop during the afternoon (greater values with southward extent).
Cooling aloft, modest mid-level lapse rates, and moderate deep-layer
shear will support a mix of multicells and supercells. Large hail
and isolated severe gusts will be the main concerns within parts of
central New Mexico.
..Wendt.. 10/21/2026
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0207 PM CDT Wed Oct 21 2026
Valid 221200Z - 231200Z
...NO CRITICAL AREAS...
The forecast remains on track as previously described with no
changes necessary.
..Stearns.. 10/21/2026
.PREV DISCUSSION... /ISSUED 1159 PM CDT Tue Oct 20 2026/
...Synopsis...
An upper low will pivot into CA and the Great Basin D2/Thursday
bringing cloud cover, cooler temperatures and precipitation back
into the Southwestern U.S. during the day, reaching the Northern
Rockies by Thursday night. This will alleviate a broader fire
weather threat across much the West. An upper-level ridge situated
over the Plains accompanied by an expansive surface high pressure
across the eastern U.S. will persist through Thursday. Light
northerly flow will shunt Gulf moisture southward, leading to
appreciably low RH values of 15-20% during the day over the lower MS
River Valley and portions of the Southeast where fuels remain dry.
However, weak boundary layer flow will limit afternoon wind speeds
to less than 10 mph, mitigating significant fire weather concerns.
...Please see www.spc.noaa.gov/fire for graphic product...
SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0433 PM CDT Wed Oct 21 2026
Valid 231200Z - 291200Z
While upper-level high pressure persists across the middle of the
country, a significant trough will impact the western CONUS. This
pattern will continue near-normal temperatures amid dry conditions
over much of the Southeast US. Vegetation in this area will become
increasingly vulnerable to burning, especially across the southern
Appalachian Mountains and the lower Mississippi River Valley, where
ERCs are forecast to reach the 90-95th percentiles. However,
generally weak winds will limit the overall fire threat there.
The upper-level trough currently located off the CA coast will
slowly drift northeastward, placing its axis through the central
Great Basin on Day 3/Friday and eventually the Great Plains by Day
6/Monday. Expect resulting colder air and widespread precipitation
across a large portion of the Intermountain region, portions of the
Sierras, and the coastal CA mountains where fuels have been
persistently dry. However, relatively dry portions of the northern
High Plains will experience strong and gusty southwest winds
(sustained near 20-30 mph) amid borderline afternoon RHs of 20-30%
on Day 3/Friday. Even so, much warmer than normal temperatures ahead
of a cold front passage, expected to occur after sunset across the
region, will allow for elevated to near-critical fire weather
conditions from portions of north-central WY through far western SD.
Thus, an area of 40% probability of critical wind/RH was introduced
over portions of this region for Day 3/Friday.
Moving forward in time to next week, forecast uncertainty increases.
However, recent guidance trends indicate that an upper-level ridge
is likely to return to the Intermountain West by mid-to-late next
week. Embedded shortwave troughs will continue to propagate through
the flow, maintaining chances for precipitation across much of the
northwestern quadrant of the CONUS.
..Stearns.. 10/21/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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