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SPC Forecast Products

Storm Prediction Center

Published: Tue, 24 Oct 2017 06:53:02 +0000

Last Build Date: Tue, 24 Oct 2017 06:53:02 +0000

Copyright: None

SPC - No watches are valid as of Tue Oct 24 06:53:02 UTC 2017

Tue, 24 Oct 2017 06:52:06 +0000

No watches are valid as of Tue Oct 24 06:53:02 UTC 2017.

SPC - No MDs are in effect as of Tue Oct 24 06:53:02 UTC 2017

Tue, 24 Oct 2017 06:52:05 +0000

No Mesoscale Discussions are in effect as of Tue Oct 24 06:53:02 UTC 2017.

SPC Oct 24, 2017 0600 UTC Day 1 Convective Outlook

Tue, 24 Oct 2017 05:34:21 +0000

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1230 AM CDT Tue Oct 24 2017

Valid 241200Z - 251200Z



A few severe thunderstorms are possible today across a portions of
the Northeast, particularly across New Jersey northward through the
Hudson Valley.  These storms will be accompanied by a risk for a few
strong to damaging wind gusts and possibly a tornado or two.

Shortwave trough currently moving through the upper OH Valley is
expected to pivot northward/northwestward through the Lower Great
Lakes region and into far eastern Ontario before maturing further
over the Upper Great Lakes. An additional shortwave trough,
currently moving into the middle MS Valley, will continue
eastward/southeastward through the TN Valley and Southeast States.
Evolution of this pair of shortwaves will result in the
amplification of the parent upper trough over much of the central
and eastern CONUS. 

At the surface, low associated with the upper OH Valley shortwave
trough will further occlude and remain largely in place over the
Great Lakes as the overall cyclone matures. Attendant cold front
will gradually progress eastward across the Northeast and off the
Mid-Atlantic coast. By 00Z Wednesday, this front will likely extend
from VT southward to off the NC coast. 

Low-level moisture is expected to increase across the region as
southeasterly low-level flow encourages moisture advection ahead of
the approaching cold front. General expectation is for mid 60s
dewpoints to be in place by early morning across southern portions
of the Northeast (i.e. NJ and Hudson Valley ) with lower 60s
dewpoints likely extending as far north as southern VT. Despite this
favorable low-level moisture, the lack of strong forcing for ascent
and leading stratiform character to the convective line will result
in poor lapse rates, limited heating, and moist profiles, all of
which will act to limit instability. HREF suggests SBCAPE will
remain below 500 J/kg across the majority of the area. The only
exception is across NJ where higher dewpoints will likely support
slightly stronger instability. 

In contrast to the marginal thermodynamic environment, strong wind
fields, particularly below 700 mb, will provide a favorable
kinematic environment for strong/severe storms. Guidance suggests
850 mb winds will be near 55 kt and 0-1 km SRH will be around
250-300 m2/s2 within the warm sector. The resulting low CAPE/high
shear environment will likely support sporadic/transient strong
updrafts capable of damaging wind gusts. Additionally, given the
strength of the low-level wind fields, a tornado or two is also

..Mosier.. 10/24/2017

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SPC Oct 24, 2017 0600 UTC Day 2 Convective Outlook

Tue, 24 Oct 2017 05:35:19 +0000

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1145 PM CDT Mon Oct 23 2017

Valid 251200Z - 261200Z


Thunderstorms may impact eastern portions of southern New England
Wednesday, accompanied by at least some risk for potentially
damaging wind gusts.

Relatively low predictability to short wave developments within the
larger-scale flow remains evident in the model output.  In general,
though, the pattern appears likely to remain amplified, but initial
large-scale troughing over the East may slowly begin to lose some
amplitude and accelerate northeastward across the Atlantic Seaboard.
 This is expected to occur as an upstream short wave trough begins
to amplify southeastward across the central Canadian/U.S. border
area and northern Plains, as the crest of large-scale ridging west
of the Pacific coast builds northward through parts of the northeast
Pacific and western Canada.

It still appears that a cold front associated with the remnant
eastern U.S. troughing may be in the process of advancing into New
England, east of much of the middle and southern Atlantic coast, and
through the southern Florida Peninsula by 12Z Wednesday.  It is
expected to continue eastward into the western Atlantic through
Wednesday night, although progression through eastern portions of
New England is becoming a bit more unclear.  In the wake of the
front, generally dry and stable conditions are forecast to prevail
across much of the nation.

...New England...
Portions of the region, particularly eastern portions of southern
New England, may still be located within a narrow pre-frontal plume
of seasonably moist air, with at least weak instability rooted
within the boundary layer or just above the boundary layer. 
Coincident with a corridor of 40-60 kt southerly flow in the 850-500
mb layer, the environment may be conducive to the risk for
convection capable of enhancing the downward transport of higher
momentum, accompanied by potentially damaging surface gusts.  It
still appears that this threat could impact the Boston/Providence
area through midday, and the Cape Cod area through Wednesday

..Kerr.. 10/24/2017

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SPC Oct 24, 2017 0730 UTC Day 3 Severe Thunderstorm Outlook

Tue, 24 Oct 2017 06:52:10 +0000

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0150 AM CDT Tue Oct 24 2017

Valid 261200Z - 271200Z


The risk for severe thunderstorms appears negligible across the
U.S., Thursday through Thursday night.

Mid/upper flow appears likely to remain amplified across the eastern
Pacific into North America through this period.  Within this regime,
a significant mid/upper high center may develop near the Pacific
Northwest coast, within larger-scale ridging building as far north
as the Canadian Yukon and Northwest Territories.  Downstream,
cyclonic flow is forecast to continue to sharpen near/ east the
length of the U.S. Rockies through the Mississippi Valley.
The initial Eastern large-scale trough is expected to continue to
lose amplitude while accelerating northeast of the Atlantic
Seaboard.  However, it now appears that a vigorous remnant short
wave impulse could support significant surface cyclogenesis along a
frontal zone across parts of eastern Maine into eastern
Quebec/western New Foundland and Labrador.

This latter development may be accompanied by some risk for
generally weak thunderstorm activity across parts of Maine. 
Potential for thermodynamic profiles to become supportive of an
appreciable severe weather risk still seems low at this time.  

Ahead of another cold front advancing across and southeast of the
southern Plains and Ozark Plateau by late Thursday night, some
northwest Gulf of Mexico boundary layer moistening and inland
advection appears possible.  However, it currently appears unlikely
to contribute to sufficient destabilization to support an
appreciable risk for thunderstorm activity.

..Kerr.. 10/24/2017

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SPC Day 1 Fire Weather Outlook

Tue, 24 Oct 2017 04:50:48 +0000

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1149 PM CDT Mon Oct 23 2017

Valid 241200Z - 251200Z


The overall surface synoptic pattern will be characterized by
expansive high pressure across much of the West, a deeply occluded 
and nearly stationary low over the Great Lakes, and a weak surface
trough along the California coast.  Each of these atmospheric
features will contribute to heightened fire weather concerns across
portions of southern California, the Lower Colorado River Valley,
and central Plains.

...Coastal Ranges of southern California...
Northeasterly surface flow will continue to remain strong across the
region owing to a continued strong surface pressure gradient between
the western high and the coastal trough.  Wind speeds will range
from 15-25 mph in most areas, with gusts perhaps reaching 50 mph in
terrain-favored canyons and valleys.  Overnight recovery will remain
poor, and latest model guidance suggests that critical (i.e.,
10-15%) RH values will exist especially within the critical area
during the early morning before falling into the single digits in
several areas during peak-heating hours as temperatures approach
90-100 F.  The combination of very warm afternoon temperatures,
gusty winds, low RH, and dry fuels all support elevated to critical
fire weather areal delineations as the risk of rapid fire spread
will remain high.

...Lower Colorado River Valley...
Strong high pressure across the Great Basin will continue to favor
gusty northerly flow across the region, with areas of 15-25 mph flow
becoming common by mid-afternoon (strongest within the critical
delineation).  RH values will also remain low (7-12%) as
temperatures rise in 80s and low 90s.  Where fuels are dry, elevated
to critical fire weather conditions will exist.

...Central Great Plains and vicinity...
A strong surface pressure gradient across the region will favor
development of 20-25 mph surface flow (with a few higher gusts)
through the early evening in a broad area of the central Plains. 
Insolation/surface heating will result in temperatures rising into
the 50s to near 60 F.  RH values will remain mostly above critical
thresholds (20-25%) during peak heating hours.  Although elevated
atmospheric fire weather conditions will exist in many areas of the
Plains, the elevated delineation was confined to areas of western
Nebraska, western Kansas, and eastern Colorado where fuels were
driest and could support fire growth/spread.  Farther south into
western Oklahoma and western Texas, locally elevated fire weather
conditions will exist where fuels are dry.

..Cook.. 10/24/2017

...Please see for graphic product...

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SPC Day 2 Fire Weather Outlook

Tue, 24 Oct 2017 04:58:37 +0000

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1157 PM CDT Mon Oct 23 2017

Valid 251200Z - 261200Z


The stout anticyclone initially centered over the Great Basin will
weaken throughout the day as a surface low and trough rapidly deepen
across the Canadian Prairies southward into the central Great
Plains.  Meanwhile, a trough will remain situated along the
California coast.  Fire weather concerns will remain high in coastal
ranges of southern California, while rapidly increasing D2/Wednesday
afternoon in the lee of the northern and central Rockies in response
to the aforementioned deepening low/trough.

...Coastal Ranges of Southern California...
With weakening high pressure across the Great Basin, the overall
pressure gradient in the region will weaken substantially throughout
the day.  However, enough of a gradient will remain through midday
in many areas for continued gusty northeasterly surface flow
(gusting to 40+ mph in terrain favored areas) along with areas of
very poor recovery and near-critical RH values persisting through
the morning.  A critical area has been introduced where winds will
be strongest during the morning hours amidst this dry airmass,
although winds should lessen progressively throughout the day.

...Portions of the northern Plains and adjacent Rockies from
Southeast Wyoming northward through much of Montana...
A dangerous fire weather scenario appears to be taking shape
especially across Montana D2/Wednesday afternoon.  The deepening
surface low/trough across the Dakotas and adjacent Canadian Prairies
will tighten the surface pressure gradient substantially throughout
the day, with surface flow also being strengthened by vertical
mixing of very strong flow aloft (60-70 kts at 500 mb).  20-30 mph
westerly flow will become common, with some areas gusting above 50
mph during peak heating hours.  Mid to upper 70s F surface
temperatures, 10-20% RH values (highest from central into
southeastern Montana), and dry fuels (evidenced by at least one
ongoing large fire) suggest the presence of a critical burn
environment with rapidly spreading fires becoming likely.

Surface flow will become progressively weaker farther south of
Montana D2/Wednesday afternoon, although a fairly localized area of
20+ mph surface flow will develop for several hours near the Laramie
Range of Wyoming and adjacent areas of western Nebraska.  Here,
guidance suggest that RH values will fall just below 15% for a few
hours during the evening, and with dry fuels across the region,
critical fire weather conditions are expected.  Farther west and
north (from central into northeastern Wyoming), latest guidance
suggest that strongest surface flow will not coincide with
sufficiently low RH for a critical delineation, although this
scenario will continue to be monitored.

..Cook.. 10/24/2017

...Please see for graphic product...

Read more