SPC - No watches are valid as of Thu Feb 22 10:08:02 UTC 2018

No watches are valid as of Thu Feb 22 10:08:02 UTC 2018.


No Mesoscale Discussions are in effect as of Thu Feb 22 10:08:02 UTC 2018.

SPC Feb 22, 2018 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1130 PM CST Wed Feb 21 2018

Valid 221200Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few strong thunderstorms are possible today through tonight,
mainly across parts of the southern Plains.  However, the risk for
severe storms still appears negligible.

...Discussion...
It appears that positively tilted, large-scale mid/upper troughing
will be maintained across the West today, as another significant
short wave trough digs southeast of the Pacific Northwest, toward
the southern Great Basin.  A preceding short wave is already in the
process of accelerating northeast of the lower Colorado Valley. 
Models indicate that it will continue across the Four Corners region
early today, and through the mid Missouri Valley into the Upper
Midwest by late tonight.

Forcing for ascent associated with the lead feature is expected to
remain well to the west and north of a sharp surface frontal zone
now stalled across the Cumberland Plateau through the lower
Mississippi Valley and Texas Gulf coast region.  Models are
suggestive that some erosion of the shallow leading (southeastern)
edge of the cold surface-based air mass is possible from portions of
southeast Texas into the lower Ohio Valley, beneath anticyclonic
mid-level flow on the northwestern periphery of persistent strong
subtropical ridging centered off the south Atlantic coast.  However,
generally weak mid-level lapse rates and forcing for ascent are
expected to limit potential for appreciable boundary layer
destabilization and vigorous thunderstorm development.

Highest thunderstorm probabilities seem likely to remain focused
above the residual cold surface-based air to the north of the
frontal zone, from portions of the southern Plains northeastward
toward the Ozark Plateau.  One wave of thunderstorm activity may
form in association with forcing accompanying the aforementioned
impulse emerging from the Southwest, spreading across and northeast
of the Red River Valley this afternoon.  Another wave of
thunderstorm activity appears possible late tonight, near and
southeast of the Texas Hill Country into northeast Texas.  This
latter convection is expected to be supported by low-level warm
advection downstream of the primary short wave digging into the
Great Basin, and perhaps forcing associated with an impulse within
the subtropical stream.  This may occur in the presence of at least
somewhat more substantive steepening of mid-level lapse rates than
with the earlier convection.  However, it remains unclear whether
mid-level destabilization will be sufficient to support an
appreciable severe hail risk.  Given the late night (end of period)
timing, less than 5 percent severe probabilities will be maintained
for now.

..Kerr/Leitman.. 02/22/2018

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SPC Feb 22, 2018 0700 UTC Day 2 Convective Outlook

SPC 0700Z Day 2 Outlook
      
Day 2 Outlook Image
Day 2 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
1233 AM CST Thu Feb 22 2018

Valid 231200Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

CORRECTED FOR GENERAL THUNDERSTORM GRAPHIC

...SUMMARY...
Showers and a few thunderstorms are expected from a portion of the
Southern Plains to the lower and middle Mississippi and Ohio Valley
regions Friday.

...Discussion...

Upper pattern will remain characterized by a synoptic trough over
the western U.S. and a downstream low-amplitude ridge in the east.
Weak vorticity maxima embedded within the broad southwesterly flow
regime will interact with baroclinic zone that should initially
extend from south TX into the OH Valley. Most thunderstorms should
remain confined to zone of isentropic ascent and weak instability on
cool side of this front. Deep convection will struggle to develop in
warm sector due to weak forcing and a very marginal thermodynamic
environment with warming temperatures aloft. However a few lightning
strikes cannot be ruled out with showers that might initiate in
confluence zone from southern LA into southern MS.

..Dial.. 02/22/2018

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SPC Feb 22, 2018 0830 UTC Day 3 Severe Thunderstorm Outlook

SPC 0830Z Day 3 Outlook
      
Day 3 Outlook Image
Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0219 AM CST Thu Feb 22 2018

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM A PORTION OF
EAST TEXAS INTO THE LOWER MISSISSIPPI...TENNESSEE AND OHIO
VALLEYS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM A PORTION
OF THE SOUTHERN PLAINS THROUGH THE OHIO VALLEY AND SOUTHEAST
STATES...

...SUMMARY...
Strong to severe storms will be possible Saturday from a portion of
northeast Texas through the lower Mississippi, Tennessee and Ohio
Valleys.

...Northeast TX into the lower Mississippi Tennessee and Ohio
Valleys...

A significant shortwave trough will eject northeast through the
central Plains and middle to upper MS Valley region Saturday and
Saturday night while taking on a negative tilt. In response to
forcing accompanying this feature, a surface low initially over the
southern Plains will deepen as it develops northeast through the
middle MS Valley, eventually reaching the Great Lakes toward the end
of the period. Warm front extending east from the surface low will
move northward, reaching the OH Valley Saturday night. A cold front
initially across west TX will advance through the Southern Plains
and middle to lower MS Valley during the day reaching the OH and TN
Valleys Saturday night. A strengthening low-level jet resulting from
the deepening cyclone will transport richer gulf moisture northward
with low 60s F dewpoints as far as the OH Valley and mid to upper
60s from east TX to the lower MS Valley. However, instability will
probably remain marginal due to widespread clouds and modest lapse
rates with MLCAPE likely to remain below 1000 J/kg over most of the
warm sector. 

A forced line of potentially strong to severe storms should evolve
in vicinity of cold front initially over north central or northeast
TX into southeast OK during the day. Activity will subsequently move
into the lower MS, TN and OH Valley regions as the low-level jet
strengthens to 60+ kt and shifts northeast through moistening warm
sector. Vertical shear and overall character of wind profiles will
be more than adequate for organized severe storms, with potential
for LEWP, bowing segments and a few embedded supercells capable of
damaging wind and a few tornadoes. An upgrade to higher
probabilities might be needed in later outlooks once uncertainties
regarding the thermodynamic environment have been mitigated.

..Dial.. 02/22/2018

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SPC Feb 22, 2018 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
0405 AM CST Thu Feb 22 2018

Valid 251200Z - 021200Z

...DISCUSSION...
Early day 4 (Sunday) at least a marginal severe threat may be
ongoing along remnant squall line from the southern Appalachians
into the Southeast States and possibly continuing into the Middle
Atlantic. However, tendency will be for the stronger forcing and
low-level jet to shift away from the more unstable portion of the
warm sector, limiting overall severe threat.

The cold front will move into the northern Gulf by day 5 (Monday)
leaving stable conditions inland. While elevated convection may
occur as this boundary retreats north as a warm front later day 6
(Tuesday night), overall severe weather threat should remain low.

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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
0126 AM CST Thu Feb 22 2018

Valid 221200Z - 231200Z

...NO CRITICAL AREAS...

...Synopsis...
An upper trough over the western U.S. will deepen and slowly shift
east over the Great Basin today. Downstream, a broad swath of deep
layer southwesterly flow will persist east of the Rockies. Strong
surface high pressure centered over the Great Lakes will track east
toward New England. Gulf moisture will slosh northeast as Wednesday
cold front retreats as a warm front across the lower Ohio Valley
into eastern TX. Fire weather concerns are not expected given
widespread precipitation over the last few days east of the Rockies,
and a general lack of strong surface winds aligning with low RH
values.

..Leitman.. 02/22/2018

...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
0126 AM CST Thu Feb 22 2018

Valid 231200Z - 241200Z

...Synopsis...
The western upper trough centered over the Great Basin will track
eastward to the southern/central Rockies on Friday. As heights fall,
deep layer southwesterly flow will increase and a weak surface
trough will develop across the southern High Plains. This will lead
to breezy southwest surface winds across much of NM. RH values also
will fall into the 15-25 percent range. This will result in elevated
fire weather potential across the eastern NM Plains into parts of
far southeast CO and southwestern TX. While gusty winds and low RH
will also exist across western and central NM, fuel conditions are
less favorable than further east, limiting fire weather concerns.

..Leitman.. 02/22/2018

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

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