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Storm Prediction Center


10/25/2020 03:33 AM
SPC - No watches are valid as of Sun Oct 25 07:34:02 UTC 2020
No watches are valid as of Sun Oct 25 07:34:02 UTC 2020.
10/25/2020 03:33 AM
SPC - No MDs are in effect as of Sun Oct 25 07:34:02 UTC 2020
No Mesoscale Discussions are in effect as of Sun Oct 25 07:34:02 UTC 2020.
10/25/2020 01:23 AM
SPC Oct 25, 2020 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
1216 AM CDT Sun Oct 25 2020

Valid 251200Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for severe thunderstorms appears negligible across the U.S.
Sunday through Sunday night.

...FL to the Carolina/Virginia Coastal Vicinity...

An upper shortwave trough will be advancing northeastward early in
the period while a cold front drops southward to the lee of the
Appalachians across the Piedmont. Meanwhile, the southern extent of
the front across FL will become increasingly diffuse over the
Peninsula. Moist southerly low-level flow ahead of these features
amid weak instability and modest forcing for ascent should result in
isolated thunderstorms through the afternoon.

...Four Corners into the Southern Great Plains Vicinity...

A series of shortwave troughs will dig southward across the western
U.S. and across the northern Plains on Sunday, bringing a belt of
strong southwesterly mid/upper level flow from the southwestern U.S.
northeastward across the Plains. As an intense surface high builds
over the northern Rockies and adjacent High Plains, a strong cold
front will surge southward across the central and southern Plains. A
somewhat shallow intrusion of seasonably cold air will surge
southward behind the front, while southerly low/mid level flow
maintains moist advection aloft. Isolated elevated thunderstorm
activity appears likely during the evening and overnight in this
warm advection regime, atop the shallow cold layer in the vicinity
of the midlevel baroclinic zone, from parts of western TX through OK
and into parts of the Ozarks.

Further west across the Great Basin, forcing for ascent will
increase over the Four Corners vicinity as the upper trough digs
southward across the western Great Basin. As this occurs, cooling
aloft will result in steepening lapse rates amid modest midlevel
moisture. This should result in weak, but adequate instability for
isolated thunderstorm development Sunday afternoon and evening
across the Four Corners vicinity.

..Leitman.. 10/25/2020

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10/25/2020 01:25 AM
SPC Oct 25, 2020 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
1219 AM CDT Sun Oct 25 2020

Valid 261200Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast on Monday across the
contiguous United States.

...Synopsis...
A mid-level trough located initially over UT will evolve into a
closed mid-level low and move south into southern AZ during the
period.  Meanwhile, a mid-level anticyclone will reside over FL.  In
the low levels, a prominent surface high over the central High
Plains will favor a cold front pushing south through central TX and
the TX Hill Country.  Weak elevated instability is forecast north of
the surface front where the risk for isolated thunderstorms will
extend from the Edwards Plateau of TX, north and northeastward into
the Ozark Plateau.  Isolated to widely scattered diurnal
thunderstorms are possible across the FL Peninsula.

..Smith.. 10/25/2020

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10/25/2020 03:14 AM
SPC Oct 25, 2020 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
0211 AM CDT Sun Oct 25 2020

Valid 271200Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not currently forecast across the
contiguous United States on Tuesday.

...Synopsis...
A closed mid-level low will migrate slowly eastward from southern AZ
to far west TX during the day 3 period.  In the low levels, a cold
front draped from deep south TX northeast along the TX coast and
into the LA, will feature an unseasonably cool airmass to its
northwest over the central and southern Great Plains.  A developing
tropical cyclone is forecast to move into the central Gulf of Mexico
during the day.  As the tropical cyclone gradually approaches the
mouth of the MS River (see the latest National Hurricane Center
forecasts for the expected track and timing information), a maritime
tropical airmass will slowly advance northward in the lower MS
Valley.  The gradually destabilizing airmass over the Gulf coastal
plain will become more favorable for isolated thunderstorms to
develop on the outer periphery of the tropical cyclone.  The
expected strengthening of the wind field that would support a
conditional risk for rotating storms near the mouth of the MS River,
will probably not occur until after dawn Wednesday.

..Smith.. 10/25/2020

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10/25/2020 02:41 AM
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
0139 AM CDT Sun Oct 25 2020

Valid 251200Z - 261200Z

...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHERN
CALIFORNIA INTO THE BAY AREA...
...CRITICAL FIRE WEATHER AREA FOR SURROUNDING THE EXTREME AREA
ACROSS NORTHERN/CENTRAL CALIFORNIA...
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...
...CRITICAL FIRE WEATHER AREA FOR SOUTHWESTERN NEW MEXICO...

...Synopsis...
***Dangerous fire-weather conditions expected across northern and
central California today and tonight***

Very strong high pressure will spread southward across the northern
Rockies today as surface troughing/low pressure extends from the
West Coast southeastward through the Lower Colorado River Valley and
southern Rockies.  Given continued dry conditions across much of the
West and areas of extremely dry fuels, widespread elevated to
critical fire weather is expected.  A higher-end fire-weather event
is also expected across northern California today into tonight.

...Northern/central California and western Oregon...
Latest high-resolution guidance indicates areas of 30-40 mph surface
winds will develop early the forecast period across the northern
Sacramento Valley and spread southward toward the Bay Area
throughout the forecast period.  These strong winds will combine
with very low RH values (below 15%) areawide across California
(slightly higher in northern areas.  Dry fuels and very high ERCs
will result in a higher-end fire-weather event and Extremely
Critical areas are in place to address the threat.  It is worth
noting that some areas of the Extremely Critical risk will
experience very strong surface flow and dry surface conditions well
after dark, with recent high-resolution guidance depicting 30+ mph
surface winds through 12Z Monday in the Bay Area and vicinity.  

Farther north into Oregon, gusty northeasterly winds are expected to
foster an elevated fire-weather risk especially during the
afternoon, where 50s F surface temperatures and single-digit
dewpoints will favor fire spread where fuels are dry.

...Southern California...
Models indicate that strong offshore winds will commence especially
in the 09Z-12Z Monday timeframe (overnight) across the southern
Transverse ranges.  Gusts above 40 mph are expected.  These winds
will be accompanied by low RH values (below 20%) that will continue
into the D2/Mon forecast period.  The area of greatest concern is
mainly tied to the mountains and higher elevations across Ventura to
western Riverside Counties, where gusts as strong as 80 mph are
possible.  A critical fire-weather risk is in place for areas that
are likely to experience the strongest winds.

...Southern Nevada eastward to west Texas...
The combination of strong flow aloft, a strong surface pressure
gradient, and vertical mixing processes will result in a broad area
of 20-35 mph westerly flow, with higher gusts in terrain-favored
areas.  These surface winds will combine with low RH values -
perhaps as low as 15% or so across southeastern Arizona and southern
New Mexico.  Fuels are dry across the region, which has been devoid
of appreciable precipitation for as much as 6 weeks in some areas.  

Latest high-resolution guidance indicates that a few areas in
southwestern New Mexico and vicinity will fall below 15% for a few
hours during peak heating.  In coordination with affected local
offices, decided to introduce a small critical area for this
scenario.

..Cook.. 10/25/2020

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

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10/25/2020 03:33 AM
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
0231 AM CDT Sun Oct 25 2020

Valid 261200Z - 271200Z

...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN
CALIFORNIA...
...CRITICAL FIRE WEATHER AREA FOR SURROUNDING THE EXTREME AREA IN
SOUTHERN CALIFORNIA...
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHERN CALIFORNIA...

...Synopsis...
The center of a broad area of surface high pressure initially over
the northern Rockies will gradually shift south-southeastward
through the High Plains.  Meanwhile, surface troughing will persist
along the West Coast and southwestern U.S., maintaining an
appreciable surface pressure gradient across these areas.  The
resultant wind fields will support areas of elevated to extremely
critical fire weather - most potent in terrain-favored areas of both
northern and southern California.

...California, southern Nevada, and southern/western Arizona...
The aforementioned surface pressure pattern will favor several areas
of enhanced surface flow within the elevated delineation Monday
through Monday night.  This flow will occur within a dry low-level
airmass due to offshore flow and downsloping winds.  RH values will
fall below 15% in most areas - and perhaps as low as 5-10% across
the Sacramento Valley and areas of southern California.  

At this time, the greatest risk of critical fire weather exists in
the Sacramento Valley and vicinity in northern California and along
the Transverse Ranges in southern California.  In these areas,
terrain forcing will foster wind gusts exceeding 40 mph at times -
and potentially as high as 80 mph across southern California.  Dry
fuels in both areas will combine with the volatile atmospheric
conditions to foster potential for rapid fire spread in these areas.
The extremely critical area in southern California was introduced
based on the expected dry and windy conditions and after some
coordination with affected offices. 

Locally critical fire-weather may be observed across the Lower
Colorado River Valley, though the driest conditions may not overlay
the driest fuels (located in southeastern Arizona).

..Cook.. 10/25/2020

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

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