Storm Prediction Center Forecast


RSS Mesoscale Discussions from Storm Prediction Center

SPC - No watches are valid as of Wed Oct 23 07:32:01 UTC 2019

No watches are valid as of Wed Oct 23 07:32:01 UTC 2019.


SPC - No MDs are in effect as of Wed Oct 23 07:32:01 UTC 2019

No Mesoscale Discussions are in effect as of Wed Oct 23 07:32:01 UTC 2019.


SPC Oct 23, 2019 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
1142 PM CDT Tue Oct 22 2019

Valid 231200Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

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

...Synopsis...
A deep upper trough covering much of the eastern CONUS is forecast
to lift northeastward through the period, as an attendant cold front
moves eastward across New England and southward into the southern FL
Peninsula. A few elevated thunderstorms are possible across portions
of eastern New England this morning, along and ahead of the cold
front. Isolated thunderstorms will also be possible across the
southern FL Peninsula through much of the period, as the cold front
stalls out and begins to return northward as a warm front tonight. 

Further west, another upper trough will amplify into portions of the
central/southern Rockies and Plains as a vigorous shortwave drops
southward into the Four Corners region. A cold front will move
southward across the Plains in conjunction with this system. North
of the front, isentropic ascent related to an increasing low-level
jet will result in an expanding precipitation shield by late tonight
from north-central TX into OK. Embedded convective elements within
this area of rainfall will be capable of producing at least isolated
lightning strikes, with weak but sufficient MUCAPE (250-500 J/kg) in
place. More substantial elevated instability will reside over
northwest TX, where a conditional risk of a few stronger storms will
be present late tonight. However, confidence in deep convection
across this region is low, with large-scale ascent expected to
remain focused further northeast through 12Z Thursday morning.

..Dean.. 10/23/2019

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SPC Oct 23, 2019 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook
      
Day 2 Outlook Image
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1145 PM CDT Tue Oct 22 2019

Valid 241200Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY
AFTERNOON AND EVENING ACROSS PARTS OF CENTRAL TEXAS...

...SUMMARY...
Strong thunderstorms may impact parts of central Texas Thursday
afternoon and evening, perhaps accompanied by some risk for severe
hail.

...Synopsis...
The mid-latitude westerlies may trend more zonal along the
Canadian/U.S. border during this period, as the progression of a
couple of short wave perturbations begins to flatten initially
amplified, positively tilted mid-level ridging across the Canadian
Rockies and parts of the Pacific Northwest.  One of these
perturbations may be rounding the crest of the larger-scale ridging,
across far northern British Columbia early Thursday, before
continuing rapidly eastward through the central Canadian provinces. 
There appears good consensus among/within the various model output
that a much more vigorous short wave impulse will accelerate
eastward into the British Columbia coast vicinity by late Thursday
night.

Downstream developments, across and to the east of the Rockies,
remain more unclear, due to continuing sizable model spread,
particularly concerning a significant short wave trough initially
digging to the east of the ridging, near the Colorado Rockies at 12Z
Thursday.  Some model output suggests that rather pronounced digging
of this impulse could continue, with the evolution of a mid-level
closed low possible, mainly near or just east of the southern
Rockies through the period.  Other guidance, continues to suggest
less amplification and a more progressive system, gradually pivoting
east-northeastward across the south central Plains.  

Regardless of the solution, though with subtle differences, models
indicate that cold surface ridging will continue to nose southward
through the remainder of the southern High Plains and lower Rio
Grande Valley by late Thursday night.  Any frontal wave development
within preceding surface troughing across the lower Rio Grande
Valley into the southern Plains Red River Valley likely will remain
weak.

...Central Texas...
It does appear that the cold front will be preceded by modest
low-level moisture return, including mid/upper 60s surface dew
points, across parts of the Edwards Plateau and Big Country into the
Interstate 35 corridor, where steepening low-level lapse rates with
daytime heating may contribute to mixed-layer CAPE in excess of 1000
J/kg.  In the presence of modest, but sheared deep-layer flow, the
pre-frontal environment seems likely to become at least marginally
conducive to organized severe thunderstorm development.

There now appears reasonably better consensus among the model output
(through at least the 21-00Z time frame Thursday) concerning the
progression of the cold front into this region, which could aid the
initiation of late afternoon thunderstorm development.  Although
convection will probably tend to be undercut by the front, there may
be a window of opportunity for storms to remain strong enough to
pose a risk for severe hail as they spread southeastward through
early Thursday evening.

...MAXIMUM RISK BY HAZARD...
Tornado:  <2%     - None
Wind:     <5%     - None
Hail:      5%     - Marginal

..Kerr.. 10/23/2019

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SPC Oct 23, 2019 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
0227 AM CDT Wed Oct 23 2019

Valid 251200Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms may impact the north central Gulf coast, northward
through portions of the lower Mississippi Valley, Friday through
Friday night.  At this time, severe weather potential appears low.

...Discussion...
A significant short wave impulse, progressing inland of the British
Columbia coast early in the period, appears likely to contribute to
larger-scale mid/upper trough amplification east of the Canadian
Rockies late Friday through Friday night.  It appears that this will
contribute to fairly strong surface cyclogenesis across the Canadian
Prairies, with deepening surface troughing extending south of the
international border, across the Dakotas/Minnesota into the central
High Plains.  A cold front trailing the cyclone may begin surging
southeast of the northern U.S. Rockies by 12Z Saturday.

However, low-level moisture return to this system, from the Gulf of
Mexico, will be interrupted by a preceding short wave trough, which
may be in the process of pivoting east-northeastward across the
southern Plains at 12Z Friday, accompanied by cold surface ridging
advancing east of the southern Plains and southeastward across the
Texas Gulf coast.

Although perhaps not as large as prior runs, sizable spread remains
evident within the various model output concerning the evolution and
progressiveness of the southern trough.  It now seems probable that
this will include strengthening wind fields associated with a
deepening embedded lower/mid tropospheric cyclone.  However, it
still appears that any surface frontal wave development, focused
along the baroclinic zone at the leading edge of the colder air,
will remain weak.

It also remains unclear to what extent dew point increases within
surface troughing, along/just ahead of the cold front, will become
supportive of boundary layer destabilization.  It appears that
considerable convection may be ongoing at the outset of the period. 
While this may be mostly post-frontal, guidance is suggestive that
this could be preceded by widespread precipitation associated with a
perturbation and influx of mid-level moisture from the lower
latitudes.  This probably will result in thermodynamic profiles
generally characterized by weak lapse rates and a large degree of
saturation.

While weak CAPE for boundary layer and elevated moist parcels may be
maintained, and supportive of some thunderstorm activity across
parts of the lower Mississippi Valley Friday through Friday night,
the potential for severe storms appears low at this time.

..Kerr.. 10/23/2019

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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
0224 AM CDT Wed Oct 23 2019

Valid 231200Z - 241200Z

...CRITICAL FIRE WEATHER AREA FOR PARTS OF NORTHERN CALIFORNIA...
...CRITICAL FIRE WEATHER AREA FOR PARTS OF SOUTHERN CALIFORNIA...

...Synopsis...
A positively tilted mid-level trough will amplify across the western
CONUS throughout the period. In turn, surface high pressure will
intensify across the Pacific Northwest into the Great Basin,
resulting in a formidable strengthening of a pressure gradient
across the state of California. As the gradient strengthens, both
northerly flow in northern California and offshore flow in southern
California (particularly late in the period) will ramp up
considerably, promoting windy and dry conditions quite supportive of
large wildfire spread/growth.

...Northern California...
Widespread elevated to critical conditions (20+ mph sustained
northerly surface winds and 15-20% RH) are expected to first be
realized in northern portions of the Sacramento Valley given
downslope flow off of the lee of the northern Coast Ranges, and
persist into the early evening hours. By mid-late evening, high
pressure will intensify further across the Great Basin, promoting a
stronger easterly component of flow. Critical wind/RH conditions
will then develop immediately west of the northern Sierra and
portions of the Coast Ranges, just north of the Bay area, and
continue to the end of the period. 

...Southern California... 
Elevated fire weather conditions (widespread 15-20 mph sustained
northeasterly surface winds amidst 15-25% RH) will transpire for
much of the day into the early-mid evening hours across portions of
the southern Transverse Ranges. Critical conditions will become
apparent shortly before sunrise, as RH will drop to near critical
thresholds and winds increase. As such, a critical area was added
for eastern portions of Ventura County into Los Angeles and
Riverside county for the 09-12Z Thursday period.

..Squitieri.. 10/23/2019

...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
0226 AM CDT Wed Oct 23 2019

Valid 241200Z - 251200Z

...EXTREMELY CRITICAL FIRE WEATHER AREA FOR EASTERN VENTURA COUNTY
TO RIVERSIDE COUNTY CALIFORNIA...
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...

...Synopsis...
A positively tilted mid-level trough will eject into the Plains
states on Day 2/Thursday, with surface high pressure continuing to
intensify across the Great Basin and the Inter-mountain West. A
strong pressure gradient will remain in place across the state of
California, where strong offshore flow will promote windy/dry
conditions. As such, a potentially volatile environment for
wildfire-spread may take shape across the southern Transverse Ranges
(especially early Day 2/Thursday). Similarly, early parts of Day 2
will also be when the most windy/dry conditions are expected to
occur across portions of northern California, prolonging some
wildfire-spread potential from late Day 1/Wednesday into early Day
2/Thursday.

...Southern California...
The most volatile period for rapid wildfire growth/spread will be
the first half of the period, where both coarser and finer
resolution model guidance depict widespread critical conditions (20+
mph sustained northeasterly winds and 10-20% RH) across all of the
southern Transverse Ranges. Portions of eastern Ventura County
(mainly parts of the Ventura Valley), to southern Riverside County
(in proximity to the Santa Ana Mountains) have received an extremely
critical delineation, as widespread winds over 30 mph (with locally
higher gusts) and 10-20% RH are expected from early-mid morning to
at least the early afternoon hours.

...Northern California...
At least widespread elevated/locally critical conditions are
expected to continue across much of the northern Sacramento Valley
and immediate adjacent areas of the northern Sierra and northern
Coast Ranges. 15-25 mph sustained north/easterly flow amidst 15-20%
RH are depicted by much of the latest guidance through the morning
hours. Some of the latest high-resolution guidance even suggests
some short-term widespread critical conditions from Day 1/Wednesday
will persist through at least mid-morning. Consistency in guidance
will continue to be evaluated for the consideration of adding a
critical to this region in future forecasts.

..Squitieri.. 10/23/2019

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

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