SPC - No watches are valid as of Tue Sep 19 11:08:01 UTC 2017

No watches are valid as of Tue Sep 19 11:08:01 UTC 2017.


No Mesoscale Discussions are in effect as of Tue Sep 19 11:08:01 UTC 2017.

SPC Sep 19, 2017 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook
      
Day 3 Outlook Image
Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0217 AM CDT Tue Sep 19 2017

Valid 211200Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
NORTH DAKOTA AND NORTHERN/CENTRAL PORTIONS OF MINNESOTA...

...SUMMARY...
A few hail-producing storms are possible in portions of Minnesota
and eastern North Dakota Thursday night.

...Synopsis...
An amplifying longwave trough across the West will become nearly
stationary with time, while a mid/upper ridge becomes established
across the Great Lakes and Ohio Valley.  At the surface,
cyclogenesis will begin in earnest across the northern Plains as a
ridge becomes dominant across the Northeast and Appalachians. 
Southerly low-level flow across much of the center of the country
will result in a moist low-level airmass retreating northward, with
60s F dewpoints reaching the Minnesota/Ontario border overnight.

...Eastern North Dakota and northern/central Minnesota...
The amplification of the long-wave trough in the West will result in
backing mid/upper flow and subtle height rises during the day, which
should keep daytime convective potential at a minimum.  In the
evening, however, strengthening low-level flow will occur in
conjunction with a 50-55kt 850mb jet across the central Plains, and
convergence on the nose of this synoptic-scale feature will foster
scattered thunderstorm development primarily after 00Z.  Steep
mid-level lapse rates and kinematic profiles will result in
primarily a hail threat with elevated convection occurring across
the region.  Marginal (5%) severe probabilities have been added to
address this threat, and later outlooks may needed higher
probabilities if more focused corridors of hail potential become
apparent.

..Cook.. 09/19/2017

Read more

SPC Sep 19, 2017 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook
      
Day 4-8 Outlook Image
Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0339 AM CDT Tue Sep 19 2017

Valid 221200Z - 271200Z

...DISCUSSION...
A persistent longwave trough over the West will be key to most
severe weather concerns for the extended forecast period.  This
trough will spread south-southwesterly mid/upper flow across the
Plains and into the Upper Mississippi Valley for much of the
forecast period, with a slowly moving surface boundary separating
cooler continental air to its north from modified tropical airmass
to its south.  Some severe risk will be likely on D4/Friday
afternoon and evening, where models focus convective potential in
portions of Minnesota and vicinity within a strongly sheared,
moderately unstable airmass.  Some difference in depiction of key
synoptic features preclude Slight/15% probabilities for this
outlook, although the region will be monitored.

From D5/Saturday and beyond, the aforementioned surface boundary
will migrate slowly southward across portions of the High Plains and
likely provide a focus for deep convection.  At least a Marginal
severe risk is likely with this activity, although subtle
differences in guidance continue at this time range and widespread
clouds/precipitation may limit the degree of destabilization in some
areas.  These factors preclude 15% or higher severe probabilities at
this time.

Read more

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
0227 AM CDT Tue Sep 19 2017

Valid 191200Z - 201200Z

...CRITICAL FIRE WEATHER AREA FOR EASTERN CO...WESTERN KS...FAR
SOUTHWEST NE...
...CRITICAL FIRE WEATHER AREA FOR NORTHWEST NM...

...Synopsis...
One strong mid/upper-level trough will move from the northern
Rockies into the northern High Plains today, while another trough
moves into the Pacific Northwest. At the surface, a cyclone and
attendant trough will move eastward across the Plains. Dry and windy
conditions will overspread much of the Southwest into the southern
High Plains, resulting in a broad area of elevated to potentially
critical conditions. 

...Four Corners Region into the Southern/Central High Plains...
As low/midlevel flow increases in response to the upper trough and
associated surface low, relatively strong low-level southwesterly
flow is expected to develop from the Southwest into the High Plains.
As sustained winds increase into the 20-30 mph range this afternoon,
substantial drying/mixing will result in the development of
potentially critical RH values from northeast AZ eastward into
western KS. 

While this pattern would typically result in a widespread critical
fire weather threat from the Southwest into the southern/central
Plains, generally marginal fuel conditions should mitigate the
potential for a more substantial threat in many locations. Two
critical areas have been delineated in this outlook. The first
critical area covers portions of eastern CO, western KS, and far
southwest NE where recent rainfall has been somewhat less than
surrounding areas, and also where there is high confidence in
several hours of critical wind/RH. A second critical area has been
included across portions of northwest NM, where recent fuel guidance
suggests the presence of somewhat drier fuels. 

Surrounding the critical areas, much of the Four Corners region
eastward into northeast NM into the OK/TX Panhandles will also see
critical wind/RH, but no upgrade has been made in these areas due to
generally marginal fuel conditions. Locally critical conditions may
also develop further north into portions of southeast WY, the NE
Panhandle, and perhaps southwest SD, though considerable uncertainty
remains in these areas with regard to timing of the cold front and
the duration of any critical wind/RH conditions.

..Dean.. 09/19/2017

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

Read more

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
0227 AM CDT Tue Sep 19 2017

Valid 201200Z - 211200Z

...Synopsis...
The large-scale upper trough over the West is expected to amplify on
Wednesday, as an embedded shortwave trough drops southeastward from
the Pacific Northwest into portions of CA/NV. Relatively dry and
windy conditions will persist over portions of the Southwest, while
weaker winds are expected over the central/southern Plains as a
strong cyclone moves away from the region. 

...Northeast AZ/Northwest NM into the Four Corners Region...
Sufficient residual low-midlevel flow and dry conditions will result
in the development of elevated to locally critical wind/RH
conditions over portions of AZ/NM into southern UT/southwest CO.
Fuels are generally not very dry across this region, though some
curing of finer fuels will have occurred on D1/Tuesday. An elevated
area has been delineated over portions of northeast AZ/northwest NM
into the Four Corners region, where the most substantial wind/RH
conditions appear likely to develop.

..Dean.. 09/19/2017

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

Read more