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SPC - No watches are valid as of Fri Sep 22 17:54:01 UTC 2017

No watches are valid as of Fri Sep 22 17:54:01 UTC 2017.


SPC - No MDs are in effect as of Fri Sep 22 17:54:01 UTC 2017

No Mesoscale Discussions are in effect as of Fri Sep 22 17:54:01 UTC 2017.


SPC Sep 22, 2017 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1116 AM CDT Fri Sep 22 2017

Valid 221630Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
UPPER PENINSULA OF MICHIGAN...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NORTHWEST MINNESOTA AND NORTHEAST NORTH DAKOTA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE PLAINS STATES AND UPPER MIDWEST...

...SUMMARY...
Isolated severe hail and wind storms are possible from the Upper
Midwest to the southern High Plains, mainly during the late
afternoon and evening.  The greatest threat today is over parts of
the Upper Peninsula of Michigan.  This afternoon and evening, the
threat will focus over northwest Minnesota.

...WI/MI today...
An ongoing cluster of strong/severe storms has been affecting
northern WI for several hours.  This cluster is in an environment
where continued weak low level warm/moist advection and daytime
heating will help destabilize the boundary layer.  Given the
persistent nature of the storms, and the slowly increasing mesoscale
organization of the activity, have added a SLGT risk for wind damage
across parts of the MI Upper Peninsula.  

...ND/MN...
The overall forecast for this region remains unchanged.  A very
moist/unstable air mass will develop this afternoon in the warm
sector of a low over northwest MN and eastern ND.  Vertical shear
profiles will also be quite strong across this region with forecast
soundings suggesting a conditional risk of supercells and tornadoes
in warm sector.  However, virtually no 12z CAM guidance shows robust
convective initiation in the warm sector.  Instead, all storms form
along and northwest of the warm front, affecting northwest MN and
northeast ND this afternoon and evening.  Supercell storm structures
are still expected in the elevated-convective regime, with stable
near-surface lapse-rates likely limiting the tornado and wind damage
potential.  Large hail is expected to be the main threat.

..Hart/Picca.. 09/22/2017

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SPC Sep 22, 2017 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook
      
Day 2 Outlook Image
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1224 PM CDT Fri Sep 22 2017

Valid 231200Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS CENTRAL NEBRASKA
TO CENTRAL MINNESOTA...

...SUMMARY...
Isolated damaging wind gusts are possible from central Nebraska
northeastward to central Minnesota Saturday afternoon and evening.

...Synopsis...
A large-scale trough will encompass the western U.S. on Saturday,
with the eastern extent advancing slowly into the central and
northern Plains.  Meanwhile, a strong mid- to upper-level ridge will
persist east of the Great Plains.  Between these two systems,
strong,meridionally oriented mid-level flow will extend from the
southern Rockies/High Plains northward to the Dakotas and northern
MN.
 
At the surface, an expansive surface anticyclone, generally anchored
over the central and southern Appalachians, will persist from the
East Coast and Great Lakes to the southern Plains and Gulf of
Mexico.  A weak low located in vicinity of the CO/KS border should
move little this forecast period, while a stationary front extends
through central NE to central MN.  A weak lee trough/dryline will
extend southward across eastern NM.  A broad area of southerly winds
across the warm sector will maintain an unseasonably moist
environment from NE into the Upper Midwest, with surface dew points
in the lower 60s in NE and around 70 F in MN.
  
...Central Nebraska northeastward to central Minnesota...
The strongest flow aloft and deep-layer shear are expected to
generally lag the stationary front this forecast period.  The
presence of a moisture rich environment (including precipitable
water values up to 1.5 inches) in vicinity of the stationary
boundary and surface heating in the warm sector should result in
moderate buoyancy.  However, modest mid-level lapse rates (near 7
C/km) and the lack of better forcing for ascent during peak heating
suggest the strength of updrafts should be tempered.  These factors
preclude an increase in severe probabilities with this outlook
issuance.

Deep-layer shear of 20-30 kt near the front should support loosely
organized storm clusters and linear segments capable of producing
isolated damaging wind gusts, especially where storms can move
through a boundary layer with steep low-level lapse rates and
greater DCAPE.  Isolated hail cannot be ruled out with any of the
stronger storms.  The Marginal severe threat should wane after
sunset, given the loss of surface heating.

..Peters.. 09/22/2017

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SPC Day 1 Fire Weather Outlook

SPC Day 1 Fire Weather Outlook
          
Day 1 Fire Weather Outlook Image
Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1037 AM CDT Fri Sep 22 2017

Valid 221700Z - 231200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF EASTERN COLORADO...

...Portions of Eastern Colorado...

The critical fire weather area has been expanded north and eastward
this update to account for latest HRRR wind/RH guidance and surface
observation trends this morning. RH values are expected to fall into
the 12-15 percent range in the critical area with sustained wind
speeds in the 20-30 mph range with higher gusts for several hours
this afternoon. 

The surrounding elevated area from portions of central NM into the
central High Plains has been adjusted only slightly.  See previous
discussion below for more details.

..Leitman.. 09/22/2017

.PREV DISCUSSION... /ISSUED 0134 AM CDT Fri Sep 22 2017/

...Synopsis...
A large-scale upper trough will make only slow eastward progress
across the western CONUS today, while upper ridging remains over
much of the central and eastern states. At the surface, a weak low
will develop northeastward across the northern Plains today, while a
second area of low pressure redevelops across eastern CO. A surface
trough/dryline will extend southward from the low over eastern CO
across the central/southern High Plains.

...Portions of the Central/Southern High Plains...
Strong 40-50 kt mid-level southwesterly winds will be present across
much of the High Plains today in association with the previously
mentioned upper trough over the western CONUS. As diurnal mixing of
the boundary layer occurs, a broad corridor of strong/gusty surface
winds will develop this afternoon from portions of the Southwest
into the eastern Great Basin, central/southern Rockies, and adjacent
High Plains. Sustained south-southwesterly winds of 20-30 mph will
likely occur, with higher gusts possible, particularly in higher
terrain. RH values will become lowered mainly into the 15-25% range
through downslope warming/drying of low levels along/behind a
surface trough/dryline. Latest short-term guidance suggests these
lowered RH values will likely occur across parts of NM, and the
ongoing elevated area has been extended southward to account for
this risk. A small area of critical conditions now appears likely
across parts of southeastern CO for a few hours this afternoon where
RH values will fall into the 12-15% range. Coupled with receptive
fuels, these forecast meteorological conditions warrant the
introduction of a small critical area across parts of southeastern
CO.

...Please see www.spc.noaa.gov/fire for graphic product...

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SPC Day 2 Fire Weather Outlook

SPC Day 2 Fire Weather Outlook
          
Day 2 Fire Weather Outlook Image
Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1249 PM CDT Fri Sep 22 2017

Valid 231200Z - 241200Z

...NO CRITICAL AREAS...

No changes to the previous outlook are needed.  See discussion below
for more details.

..Leitman.. 09/22/2017

.PREV DISCUSSION... /ISSUED 0135 AM CDT Fri Sep 22 2017/

...Synopsis...
A large-scale upper trough/low centered over the Great Basin will
continue to move slowly eastward across the western CONUS on Day
2/Saturday. An upper ridge will persist over much of the eastern
CONUS. While enhanced mid-level winds will remain present over
portions of the Southwest into the High Plains Saturday afternoon,
RH values behind a surface cold front are generally expected to
remain above critical levels. Locally elevated fire weather
conditions may occur across parts of northern AZ and southeastern UT
where RH values could become lowered near 20% in conjunction with
strong/gusty surface winds. However, only marginally receptive to
unreceptive fuels across this region and cooler temperatures behind
the surface cold front preclude the introduction of an elevated area
at this time.

...Please see www.spc.noaa.gov/fire for graphic product...

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