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SPC Forecast Products



Storm Prediction Center



Published: Tue, 23 May 2017 09:04:02 +0000

Last Build Date: Tue, 23 May 2017 09:04:02 +0000

Copyright: None
 



SPC - No watches are valid as of Tue May 23 09:04:02 UTC 2017

Tue, 23 May 2017 09:03:05 +0000

No watches are valid as of Tue May 23 09:04:02 UTC 2017.



SPC - No MDs are in effect as of Tue May 23 09:04:02 UTC 2017

Tue, 23 May 2017 09:03:04 +0000

No Mesoscale Discussions are in effect as of Tue May 23 09:04:02 UTC 2017.



SPC May 23, 2017 0600 UTC Day 1 Convective Outlook

Tue, 23 May 2017 06:07:17 +0000

SPC 1200Z Day 1 Outlook
(image)
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0100 AM CDT Tue May 23 2017

Valid 231200Z - 241200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTH
TEXAS...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL AND
SOUTHERN PORTIONS OF GEORGIA AND ADJACENT SOUTHERN SOUTH CAROLINA
AND SOUTHEAST ALABAMA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTH
TEXAS AND THE TEXAS COASTAL PLAIN...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST...

...SUMMARY...
Strong/locally severe storms are forecast across portions of
southern and eastern Texas today.  Severe risk also exists across
portions of the Southeast, focused on the southern half of Georgia
and adjacent portions of southeast Alabama and southeast South
Carolina.

...Synopsis...
A large upper trough will continue affecting the central and eastern
U.S., as it digs slowly southeastward with time.  Multiple
disturbances will rotate through the cyclonic flow field, promoting
multiple areas of convection.

At the surface, a nearly stationary front will linger from the
Carolinas west-southwest across the Gulf coastal areas and into
south Texas, and the front will again serve as a focus for
widespread convection through the period.

...South Texas and the Texas Coastal Plain...
Diurnal heating of a moist airmass residing over south Texas near
the remnant front will occur, which will support moderate afternoon
destabilization.  Resulting instability will fuel development of
multiple bands of eastward- to southeastward-moving thunderstorms as
ascent increases through the afternoon in conjunction with mid-level
height falls ahead of a short-wave trough digging into the southern
Plains.

Greatest risk -- mainly in the form of large hail -- appears to
exist across south Texas, but may extend northward across parts of
the mid and upper Coastal Plain.  Several bands of storms are
expected to traverse the area through the afternoon and evening,
before storms shift into the western Gulf and lower Mississippi
Valley through midnight.

...The Southeast...
Widespread showers and thunderstorms are progged to be moving across
the southeast U.S. through the early morning hours, along the
stalled surface front.  While the ongoing clouds/precipitation will
likely hinder destabilization potential as weak lapse rates combined
with limited heating, enough diurnal CAPE development is expected --
at least locally -- to support an early- to mid-afternoon increase
in storm activity.

Convective development will likely be aided by a zone of
quasi-geostrophic ascent currently crossing the central Gulf Coast
region and expected to spread across GA and SC during the afternoon.
 With enhanced deep-layer southwest flow, potential for locally
damaging winds is evident with stronger storms/bands of storms.  An
isolated tornado also cannot be ruled out, where locally backed
surface winds may exist ahead of a weak frontal wave accompanying
the zone of ascent.  Storms may shift northeastward into the evening
toward the North Carolina Outer Banks, and thus have expanded 5%
probability for wind across coastal North Carolina.

..Goss.. 05/23/2017

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SPC May 23, 2017 0600 UTC Day 2 Convective Outlook

Tue, 23 May 2017 06:08:33 +0000

SPC 0600Z Day 2 Outlook
(image)
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
0100 AM CDT Tue May 23 2017

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF
FLORIDA...CENTRAL AND EASTERN GEORGIA...AND SOUTHERN SOUTH
CAROLINA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT RISK OVER PORTIONS OF THE SOUTHEAST AND MID-ATLANTIC
STATES...

...SUMMARY...
Severe storms will be possible Wednesday and Wednesday night across
much of Florida, central and eastern Georgia, and southern South
Carolina. More isolated severe storms will be possible from portions
of eastern Alabama northeast into North Carolina.

...Synopsis...
An upper-level low will move southeast over the mid-Mississippi
Valley Wednesday while a trough of low pressure rotates around the
upper low across the southeast U.S. This will result in
strengthening mid-level flow across Florida and the southeast U.S. 
Surface low pressure over the Tennessee Valley region will deepen as
it lifts north towards the lower Great Lakes. A trailing
occluded/cold front will move east through the southeast states
while a warm front lifts north across the Mid-Atlantic region.  

...Southeast/Mid-Atlantic states...
South/southwest low-level flow of a seasonably moist air mass will
result in mid 60s to lower 70s surface dew points across much of
warm sector Wednesday. Widespread cloud cover and precipitation is
likely early in the day from the northern Florida peninsula north
into the Carolinas associated with a lead upper-level impulse, with
pockets of more robust heating/destabilization expected during the
afternoon. Weak/locally moderate surface-based instability combined
with strengthening wind fields/ample effective shear will result in
a favorable environment for severe storms including linear and
supercell modes. 

Diurnal intensification of ongoing storms and new storm development
should occur along the cold front Wednesday afternoon and evening as
height falls/large-scale forcing for ascent overspreads the
pre-frontal air mass. A linear storm mode should eventually be
favored with damaging winds possible, and the stronger storms may
also produce large hail given the magnitude of deep-layer shear and
cool mid-level temperatures. Strengthening low-level wind fields
during the evening will result in at least some potential for a
tornado or two. Guidance is suggestive of a weak secondary surface
low developing along the front in the vicinity of the western
Carolinas during the late afternoon/evening, which would potentially
result in backed low-level winds and a more favorable hodograph for
low-level storm rotation with any discrete storms that may form. The
severe threat should continue to progress across much of peninsular
Florida Wednesday night with a continued risk for severe wind and
hail.

..Bunting.. 05/23/2017

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SPC May 23, 2017 0730 UTC Day 3 Severe Thunderstorm Outlook

Tue, 23 May 2017 07:30:59 +0000

SPC 0730Z Day 3 Outlook
(image)
Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0229 AM CDT Tue May 23 2017

Valid 251200Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL HIGH PLAINS...

...SUMMARY...
Isolated severe storms will be possible Thursday and Thursday night
across portions of the central High Plains.

...Synopsis...
A seasonably strong upper-level trough will lift northeast across
the eastern U.S. Thursday, while upper-level ridging over the
central U.S. becomes more zonal by Thursday night. A low-amplitude
shortwave trough will move through the central High Plains late in
the day. Southerly low-level flow will become established over the
central/southern Plains resulting in a northward transport of
partially modified gulf moisture.

...Central High Plains...
A cold front will likely extend from the upper Midwest into the
central/southern High Plains late Thursday as an upslope low-level
flow component becomes established north of the southern/western
portion of the front. Surface dew points in the 50s and steep
mid-level lapse rates should result in at least modest instability
across the central High Plains. Strong/isolated severe thunderstorms
may develop during the late afternoon as ascent associated with the
weak upper-level impulse translates east within the moderately
strong mid-level flow. An increase in warm advection Thursday night
should contribute to MCS development across portions of the central
Plains with a risk for large hail and strong/damaging winds.

..Bunting.. 05/23/2017

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SPC May 23, 2017 Day 4-8 Severe Weather Outlook

Tue, 23 May 2017 09:03:07 +0000

Day 4-8 Outlook
(image)
Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0400 AM CDT Tue May 23 2017

Valid 261200Z - 311200Z

...DISCUSSION...
A low-amplitude mid-level flow pattern will develop at the beginning
of the Day 4-8 time frame across much of the central/eastern U.S.,
gradually evolving into a broadly cyclonic regime around an upper
low between the Great Lakes and Hudson Bay by Tue/May 30th.

...Day 4/Friday...
Rich gulf moisture returns to the central/southern Plains and
western gulf coast in advance of a cold front from the upper Midwest
into the southern High Plains, and east of a dryline over
Oklahoma/north Texas. A plume of steep mid-level lapse rates and
attendant capping inversion will also likely be in place, casting
uncertainty on the potential for thunderstorm development along the
southern High Plains dryline and in advance of the cold front. 
Somewhat higher confidence exists for strong/severe storms to
develop in the easterly surface flow north of the front across the
central High Plains late in the day, moving east Friday night with a
developing/veering low-level jet. Severe probabilities will likely
be warranted in future outlooks as confidence on specific risk areas
increases. 

...Day 5/Saturday and Day 6/Sunday...
Severe potential may accompany the southern Plains dryline, and cold
front as it moves south/eastward across the Great Lakes/Appalachians
into the southern Plains during the weekend. Unstable/favorably
sheared conditions will exist over a broad area from the
central/southern Plains eastward into portions of the mid-Atlantic
states. Uncertainty regarding timing of upper-level impulses and
effects of prior convection preclude severe risk areas with this
outlook.

...Day 7/Monday and beyond...
Thunderstorms will be possible along a weakening frontal boundary
extending from the northeast U.S. south/west into Texas, with
substantial uncertainty regarding daily risk areas.

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SPC Day 1 Fire Weather Outlook

Tue, 23 May 2017 07:01:08 +0000

SPC Day 1 Fire Weather Outlook
(image)
Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0155 AM CDT Tue May 23 2017

Valid 231200Z - 241200Z

...NO CRITICAL AREAS...

...Synopsis...
Cold front currently moving southward across the Plains will
continue southward throughout the day. By 00Z Wednesday, the cold
front will likely extend from a surface low over the middle OH
Valley southwestward to deep south TX. At the same time, upper low
currently over MN will drop southward into the middle MS Valley as
the flow aloft through its base strengthens. 

Widespread showers and thunderstorms are expected across portions of
the Southeast and mid-Atlantic and ahead of the cold front across
the southern Plains. High surface pressure is anticipated across the
Plains in the wake of the cold front, acting to enhance the surface
pressure gradient across portions of the Southwest. Resulting breezy
conditions will overlap antecedent dry conditions across northwest
NM to support some locally elevated fire weather conditions. Small
areal extent and short-duration of the threat as well as only
moderately dry fuels preclude introducing an outlook area with this
forecast. Fire weather conditions are not anticipated elsewhere
across the CONUS.

..Mosier.. 05/23/2017

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

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SPC Day 2 Fire Weather Outlook

Tue, 23 May 2017 07:05:40 +0000

SPC Day 2 Fire Weather Outlook
(image)
Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0200 AM CDT Tue May 23 2017

Valid 241200Z - 251200Z

...Synopsis...
Upper trough covering much of the central and eastern CONUS at the
beginning of the period is expected to shift eastward into more of
the eastern CONUS while the embedded upper low moves across the
middle MS Valley into the TN Valley. Upper ridging is expected
across the Plans in the wake of the upper trough with another
shortwave trough following behind the upper ridge across the
northern Rockies and Canadian prairie provinces. At the surface, a
large area of low pressure will drift across the eastern CONUS while
lee troughing deepens across the High Plains. Cyclogenesis is
anticipated within this lee troughing across eastern WY.

...Southwest...
A more progressive upper pattern will foster a modest increase in
westerly flow aloft over the region. A tightening of the surface
pressure gradient is also expected as lower pressures from the High
Plains westward are paired with higher pressures across the Plains.
Deep boundary-layer mixed within this environment will result in
gusty winds across a large portion of the Southwest states. In
addition to increased wind speeds, a very dry antecedent airmass
will support afternoon RH values in the low teens and upper
single-digits. The combination of low RH and gusty winds will likely
result in meteorological conditions supportive of a critical fire
weather threat. However, fuel guidance continues to show ERC values
around the 60-75th percentile and above-average 100-hr and 1000-hr
fuel moisture, mitigating the overall fire weather threat. As a
result, elevated fire weather conditions are expected across a large
part of the Southwest. Some locally critical conditions are possible
in areas where fuels are sufficiently dry.

..Mosier.. 05/23/2017

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

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