SPC Oct 31, 2026 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Sat Oct 31 2026

Valid 312000Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast through tonight.

...20z Update...
Broad/diffluent southwesterly flow aloft continues to overspread the
Southwest. Visible satellite shows high clouds entering the region,
with filtered insolation resulting in some destabilization (200-300
J/kg MLCAPE) and cumulus development amid a moist boundary layer
across portions of southern AZ and across southern NV. Despite ample
shear that will increase throughout the remainder of the day, the
notably weak instability (perhaps peaking near 500 J/kg) will limit
the severe potential with any thunderstorm activity. Nonetheless,
general thunderstorm potential has been extended into parts of
southern NV.

Otherwise, the previous forecast remains on track. See the
discussion below for more details.

..Karstens.. 10/31/2026

.PREV DISCUSSION... /ISSUED 1126 AM CDT Sat Oct 31 2026/

...Synopsis and Discussion...
Downstream of weak mid-level troughing, isolated to scattered
thunderstorms will be possible through tonight across parts of the
lower MS Valley into the FL Panhandle and Peninsula as low-level
moisture gradually advances northward across these regions. Limited
overlap of sufficient instability and deep-layer shear to support
organized updrafts should preclude severe thunderstorms across these
areas.

Across the western CONUS, isolated convection appears possible
through the period across parts of central CA into the northern
Great Basin, and portions of southern/central AZ. Southwesterly
mid-level flow is forecast to strengthen across both of these
regions as upper troughing amplifies over the West Coast and as a
mid/upper-level subtropical jet overspreads the Southwest. However,
weak instability and modest mid-level lapse rates will likely hinder
severe thunderstorm potential through early Sunday morning.


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SPC Oct 31, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1126 AM CDT Sat Oct 31 2026

Valid 311630Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast through tonight.

...Synopsis and Discussion...
Downstream of weak mid-level troughing, isolated to scattered
thunderstorms will be possible through tonight across parts of the
lower MS Valley into the FL Panhandle and Peninsula as low-level
moisture gradually advances northward across these regions. Limited
overlap of sufficient instability and deep-layer shear to support
organized updrafts should preclude severe thunderstorms across these
areas.

Across the western CONUS, isolated convection appears possible
through the period across parts of central CA into the northern
Great Basin, and portions of southern/central AZ. Southwesterly
mid-level flow is forecast to strengthen across both of these
regions as upper troughing amplifies over the West Coast and as a
mid/upper-level subtropical jet overspreads the Southwest. However,
weak instability and modest mid-level lapse rates will likely hinder
severe thunderstorm potential through early Sunday morning.

..Gleason/Chalmers.. 10/31/2026


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SPC Oct 31, 2026 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0755 AM CDT Sat Oct 31 2026

Valid 311300Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast across the U.S. today or
tonight.

...Synopsis...
Deep upper troughing currently extends from a cyclone just off the
Pacific Northwest southward into the eastern Pacific Ocean.
Extensive southwesterly flow aloft exists across much of the western
CONUS, which is situated between the aforementioned deep upper
troughing and upper ridging that extends from the Canadian Prairies
into the Southeast states. A trio of shortwave troughs is currently
moving within the broad southwesterly flow into the western
periphery of the upper ridging. Surface analysis reveals a building
warm sector downstream of these shortwaves from the southern Plains
into central Plains and Mid MO Valley.

Warm air advection within the northern portion of this warm sector
coupled with large-scale ascent attendant to the shortwave trough
moving across KS is currently supporting showers and isolated
thunderstorms from eastern SD across southern MN and
northern/eastern IA. Isolated thunderstorms will likely continue in
this region through the morning into the early afternoon before the
elevated buoyancy becomes to weak and shallow to support lightning.

Thunderstorm coverage is generally expected to increase from south
to north from the upper TX/LA coast into the Mid-South as low-level
moisture increases ascent from the KS shortwave glances northern
portions of the region. Modest buoyancy and weak shear should keep
the severe thunderstorm potential very low.

Thunderstorms are possible from the western Great Basin into eastern
ID/western WY where strong mid-level southwesterly flow and
persistent forcing for ascent are anticipated. Limited buoyancy
should keep minimize storm depth and persistence, although any
mature updrafts could produce strong gusts and/or small hail. Severe
coverage is expected to be very low.

A low-amplitude shortwave trough is forecast to move into the
south-central AZ this evening, interacting with the anomalous
moisture and modest buoyancy to support isolated thunderstorms. A
few storms could also occur across the central/southern FL Peninsula
amid the moist low to mid-level northeasterly flow.

..Mosier/Moore.. 10/31/2026


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SPC Oct 31, 2026 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0733 PM CDT Fri Oct 30 2026

Valid 310100Z - 311200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHERN AND CENTRAL ARIZONA...

...SUMMARY...
Thunderstorms with isolated severe wind gusts and hail will be
possible this evening in parts of southern and central Arizona.

...Arizona...
The latest water vapor imagery shows a shortwave trough over the
Desert Southwest with a notable dry slot extending from southern
California into western Arizona. At the surface, a 1004 mb low is
located in the Sierra Nevada of eastern California with a trough
extending southeastward into southwestern Arizona. Surface dewpoints
along the surface trough are in the upper 50s to mid 60s F.
Low-level convergence along the surface trough and large-scale
ascent associated with the upper-level system have contributed to
recent convective development across parts of western and central
Arizona. Cell initiation will continue to be possible near the
surface trough for much of the evening. In addition, the RAP has an
axis of instability extending from northern Mexico into central
Arizona, where MLCAPE is estimated in the 1000 to 1200 J/kg range.
The WSR-88D VWP at Phoenix is sampling the wind profile east of the
instability axis and has 0-6 km shear around 30 knots with gradually
veering winds with height in the low to mid-levels. This should
support an isolated severe threat with rotating cells. Isolated
severe wind gusts and hail will be the primary threats over the next
few hours.

..Broyles.. 10/31/2026


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