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Storm Prediction Center Forecast


RSS Mesoscale Discussions from Storm Prediction Center

SPC - No watches are valid as of Fri May 29 09:01:01 UTC 2020

No watches are valid as of Fri May 29 09:01:01 UTC 2020.


SPC - No MDs are in effect as of Fri May 29 09:01:01 UTC 2020

No Mesoscale Discussions are in effect as of Fri May 29 09:01:01 UTC 2020.


SPC May 29, 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
1226 AM CDT Fri May 29 2020

Valid 291200Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHEASTERN UNITED STATES...

...SUMMARY...
Scattered thunderstorms, some severe, are possible across an area
centered over PA/NY Friday afternoon through Friday evening. A few
strong storms are also possible across the northern Rockies region.

...Northeastern US...

Early-morning water-vapor imagery depicts a well-defined mid-level
vort/short-wave trough over the Mid-South lifting northeast in line
with short-range model guidance. This feature should begin to eject
quickly over the next 24hr as 500mb flow increases across the
central Appalachians this morning before translating into New
England overnight. This increase in mid-high level flow is expected
to enhance the likelihood for organized convection later today.

While mid-level lapse rates are not forecast to be particularly
steep, latest guidance suggests a corridor of strong boundary-layer
heating should develop across the Appalachians, which should result
in surface readings breaching convective temperatures around 17-18z.
Thunderstorms should develop by noon along a corridor from OH into
Upstate NY ahead of a pronounced cold front. This activity will
evolve within a strongly sheared southwesterly flow regime. While
vertical shear seems supportive of supercells, and a few may
develop, it appears thunderstorm clusters and line segments may be
the more common storm mode. Damaging winds, some hail, and perhaps a
tornado or two can be expected with pre-frontal convection as it
spreads toward New England late this afternoon.

...Northern Rockies Region...

Short-wave ridging will dominate the northern Rockies during the
day1 period; although, a strong upper low should approach the
central CA Coast by 30/12z. Prior to this upper low, diurnal heating
and orographic forcing will be the mechanisms by which scattered
convection develops across this region. A few high-based
thunderstorms are expected by late afternoon along an arcing
corridor from OR-central ID-northwestern WY. Gusty winds and
marginally severe hail are possible with the strongest convection.

..Darrow/Karstens.. 05/29/2020

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SPC May 29, 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
0108 AM CDT Fri May 29 2020

Valid 301200Z - 311200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE PACIFIC
NORTHWEST...

...SUMMARY...
Isolated severe thunderstorms are expected Saturday
afternoon/evening particularly across the Pacific Northwest, with
severe storms also possible across the High Plains and Mid-Atlantic
States.

...Pacific Northwest to northern High Plains...
An upper low and related mid/high-level jet streak are expected to
be located over central California Saturday morning, with these
features expected to steadily accelerate north-northeastward toward
Washington/Oregon/Idaho by Saturday morning, with strong surface
cyclogenesis expected east of the Cascades. The air mass should
moderately destabilize by afternoon especially from
north-central/northeast Oregon into central/eastern Washington, with
ample forcing for ascent expected to contribute to an initial uptick
of intensifying thunderstorms Saturday afternoon across
north-central/northeast Oregon. Very strong southerly winds through
a deep layer will could allow for a few supercells and more
prevalent northward-moving linear segments, which will likely spread
into central/eastern Washington by evening. Isolated severe hail and
severe-caliber wind gusts will be possible across the region. 

...Northern/central High Plains...
Lee-side cyclogenesis and a sharpening lee trough will enhance moist
low-level easterly upslope flow across the region. Widely scattered
thunderstorms should develop/increase through mid/late afternoon
near the Rockies Front Range from Colorado into Wyoming/Montana.
Moderate destabilization and 30-40 kt effective shear will allow for
a few supercells and sustained multicells capable of isolated large
hail and strong wind gusts.

...Mid-Atlantic States/Carolinas...
Showers and thunderstorms are expected early in the morning across
the region, but precipitation should end with some clearing into the
afternoon ahead of a secondary cold front and weak surface wave.
Although some uncertainties exist regarding the timing of the front
and the degree of pre-frontal destabilization, adequate
heating/destabilization (upwards of 1000 J/kg MLCAPE) into the
afternoon could allow for a few severe thunderstorms with wind
damage as the primary hazard.

...Northern/eastern Maine...
A cold front will steadily progress eastward across Maine Saturday
morning/early afternoon. Although southwesterly winds through a deep
layer will be strong, the early day passage of the cold front and
expectations for little or no surface-based buoyancy preceding it
suggest that the potential for severe-caliber wind gusts/hail should
remain low.

..Guyer.. 05/29/2020

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SPC May 29, 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
0231 AM CDT Fri May 29 2020

Valid 311200Z - 011200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTHERN/CENTRAL HIGH PLAINS...

...SUMMARY...
Isolated severe thunderstorms may occur across the northern/central
High Plains Sunday afternoon and evening.

...North-central High Plains...
The region will largely be influenced by upper-level ridging,
although weak height falls may occur across parts of Montana on the
periphery of a shortwave trough spreading over the Canadian Rockies.
A modestly moist (50s F surface dewpoints) boundary layer will be
maintained to the east of an eastward-moving cold front across
Montana, and near/east of a lee trough extending southward across
the northern/central High Plains. Differential heating in the
vicinity of higher terrain and zones of modest convergence will
influence isolated thunderstorm development Sunday afternoon,
initially across eastern portions of Montana/Wyoming southward to
the Colorado Front Range. Moderate buoyancy and 30-40 kt effective
shear will support some high-based supercells/sustained multicells
capable of large hail and strong wind gusts.

..Guyer.. 05/29/2020

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SPC May 29, 2020 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
0351 AM CDT Fri May 29 2020

Valid 011200Z - 061200Z

...DISCUSSION...
An amplified upper-level pattern will prevail across the CONUS
through the early/middle part of next week. An upper ridge will
remain centered over the south-central CONUS, with prevalent
upper-level troughing over the Southwest States and western
Atlantic. A semi-progressive belt of westerlies will be relegated to
the northern tier of the CONUS and Canada. While severe
thunderstorms will be possible each day, sub-optimal ingredients
and/or mesoscale-related uncertainties preclude any 15+ percent
outlook delineations at this time.

For Day 4/Monday, an unstable air mass is expected near an
east/southeastward-moving front across the northern Plains and Upper
Midwest including parts of the Dakotas/Nebraska into Minnesota.
While at least some severe risk may exist, there are key
uncertainties including the degree of mid-level capping and
coverage/likelihood of thunderstorms.

On Day 5/Tuesday, the previously mentioned front may be a focus for
severe thunderstorm development as it decelerates/stalls from the
north-central High Plains to the Upper Mississippi Valley vicinity.

Into Day 6/Wednesday and Day 7/Thursday, a more favorable pattern
for MCS development may materialize across parts of the Midwest/Ohio
Valley to central Appalachians and Mid-Atlantic States as an
increasingly moist/unstable air mass will reside along and south of
a roughly west/east-oriented front across these regions. The
north-central High Plains may also be a continued regional focus for
at least isolated severe thunderstorms.

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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
0152 AM CDT Fri May 29 2020

Valid 291200Z - 301200Z

...Synopsis...
An upper-level ridge will be present over the western CONUS to start
the forecast period. Throughout the day, a compact upper-level
closed low will quickly move onshore while beginning to phase with
and break down the aforementioned ridge. A zone of enhanced
mid-level flow (70-80 kt) will coincide with the base of the trough
throughout its on-shoring progression. At the surface, enough
residual moisture will be present to assist in the development of
diurnally driven convection over much of the Intermountain West.

...Southern Great Basin...
Diurnal heating and vertical mixing of the emerging zone of enhanced
mid-level flow over the region will result in hot/dry/breezy
conditions, yielding sustained surface wind speeds of 15-20 mph,
with locally higher gusts. RH values should fall into the teens,
with a few pockets dipping to 10-15% possible amid at least
marginally receptive fuels. Thus, elevated fire-weather conditions
are expected, with locally superimposed critical conditions.

...Arizona and New Mexico into Colorado and Utah...
As previously mentioned, diurnally driven convection is expected
across a large area of the Intermountain West. Coverage of these
storms is expected to remain predominately isolated amid PWAT values
at or below 0.75 inches. Thus, isolated dry thunderstorms can be
expected, and an area delineating this potential has been confined
to areas with at least marginally receptive fuels.

..Karstens.. 05/29/2020

...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
0153 AM CDT Fri May 29 2020

Valid 301200Z - 311200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF EAST CENTRAL NEVADA
AND FAR WESTERN UTAH...

...Synopsis...
An upper-level closed low situated over the California coast will
continue moving onshore while merging with the upper-level ridge
anchored over the West. As this process occurs, the closed low will
transition into an open wave while lifting northeastward into
portions of the Pacific Northwest.

...Portions of the Great Basin...
The core of the mid-level jet streak is forecast to be situated atop
the region by mid afternoon on Saturday, resulting in stronger
sustained surface wind speeds of 20-30 mph, gusting to 40-50 mph.
Meanwhile, RH values should fall into the teens and approach the
single digits in a few spots. Fuels in the region will remain
receptive to large-fire spread, given further drying that will take
place on D1/Friday. Thus, critical fire-weather conditions can be
expected over much of east-central Nevada into far western Utah.
This region is surrounded by potential for elevated fire-weather
conditions, where sustained surface winds are expected to remain in
the 15-20 mph range.

...Four Corners Region...
A continuation of diurnally driven isolated convection is expected
in areas under the influence of the upper-level ridge and where
residual moisture is present. PWAT values are expected to remain
near or below 0.75 inches over the region, supporting the notion of
dry thunderstorm potential and lightning-induced fire ignitions
where fuels are receptive.

..Karstens.. 05/29/2020

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

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