SPC Forecast

RSS Mesoscale Discussions from Storm Prediction Center

SPC - No watches are valid as of Mon Dec 11 16:15:02 UTC 2017

No watches are valid as of Mon Dec 11 16:15:02 UTC 2017.


SPC - No MDs are in effect as of Mon Dec 11 16:15:02 UTC 2017

No Mesoscale Discussions are in effect as of Mon Dec 11 16:15:02 UTC 2017.


SPC Dec 11, 2017 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0640 AM CST Mon Dec 11 2017

Valid 111300Z - 121200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
No thunderstorm areas are expected today or tonight.

...Synopsis...
In mid/upper levels, a blocky upper-air pattern will continue
through the period, dominated by mean troughing and related cyclonic
flow over the East.  In the West, a Rex pattern has been taking
shape gradually overnight, as a large but weak cyclone moves over
Baja, south of a persistent high and ridge located over the Great
Basin and interior Northwest.  In between:  a well-defined "clipper"
perturbation in northwest flow was evident in moisture-channel
imagery over parts of the Dakotas and MN.  This feature should
proceed southeastward across the upper Mississippi Valley today,
then pivot up the Ohio Valley overnight.  Its vorticity field should
phase with a faster-moving, lower-amplitude perturbation now over
SK, leading to a 12Z trough position positively tilted from PA to
eastern TN to northern LA. 

At the surface, a low associated with the northwest-flow trough
aloft was located at 11Z over northern MN, with warm front
southeastward across southern Lake Michigan, and cold front
northwestward over eastern SK.  By 00Z, the low should move
southeastward toward northern IN as another develops over the Lake
Superior region.  Meanwhile, the cold front should move to the lower
Ohio Valley, AR, southern OK and eastern NM.  By 12Z, the lows
should consolidate over western NY, with cold front southwestward
over the western Carolinas and southern LA. 

...Upper Mississippi Valley...
Strong forcing for ascent, immediately preceding the shortwave
trough, should steepen midlevel lapse rates across this region and
weaken CINH, atop a high-RH layer located between 700-850 mb. 
Forecast soundings through the forenoon hours indicate related
development of around 50 J/kg MUCAPE is possible, astride the -20 C
isotherm.  As such, very isolated/short-lived thunder cannot be
ruled out.  However, an areal thunderstorm outline is precluded by
the lack of greater values of both buoyancy and inflow-layer
theta-e.

..Edwards.. 12/11/2017

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SPC Dec 11, 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
1010 AM CST Mon Dec 11 2017

Valid 111630Z - 121200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
No thunderstorm areas are expected today or tonight.

Dry and stable conditions are expected to preclude thunderstorm
activity across the nation today.

..Hart.. 12/11/2017

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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
0944 AM CST Mon Dec 11 2017

Valid 111700Z - 121200Z

The ongoing forecast is on track with no changes needed.  Gusty
offshore winds will continue in southern California - especially in
terrain-favored areas of Santa Barbara, Ventura, and Los Angeles
counties where 30+ mph wind gusts are possible.  Farther east, a
broad area of elevated fire weather conditions will develop by
mid-afternoon, with critical thresholds (25-35 mph and 12-15% RH)
being exceeded briefly in northeastern Colorado and vicinity before
sunset.

See the previous discussion below for more information.

..Cook.. 12/11/2017

.PREV DISCUSSION... /ISSUED 0136 AM CST Mon Dec 11 2017/

...Synopsis...
Mid-level ridging will persist across the western United States,
with a deep trough found across the East. A short-wave trough moving
through the mid-level flow across the East will help drive a surface
cold front south through the Plains. 

...Southern California...

Offshore winds will continue through Monday and Monday night, albeit
not as strong as in previous days. Coincident with this, warm
temperatures and a dry airmass will support minimum
relative-humidity values falling into the single digits and teens
across much of the area. Additionally, overnight recovery should
remain poor, leaving little reprieve from the low relative humidity.
The result will be elevated fire-weather conditions.

...Central United States...

Temperatures will quickly warm into the 60s and 70s ahead of a
surface cold front moving southward through the Plains on Monday.
Additionally, a very dry airmass in place as a result of several
days of northerly winds across the Plains and Gulf of Mexico
scouring out most of what little moisture existed. The dry airmass
is borne out in evening (00Z) soundings across the Plains where
near-record low precipitable-water values for this time of year are
observed. The result will be warm temperatures and relative-humidity
values falling to near-critical to critical levels. These warm, dry
conditions will combine with winds in the 10-20 mph range to result
in elevated to locally critical fire-weather conditions across the
region. Stronger winds may exist across northern portions of the
highlighted area, but cold-air advection behind the front will allow
for the relative humidity to increase, slightly offsetting the
impacts of stronger winds.

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

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