SPC - No watches are valid as of Sat May 21 09:02:02 UTC 2022

No watches are valid as of Sat May 21 09:02:02 UTC 2022.


No Mesoscale Discussions are in effect as of Sat May 21 09:02:02 UTC 2022.

SPC May 21, 2022 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
1241 AM CDT Sat May 21 2022

Valid 211200Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN
PLAINS THROUGH THE OHIO VALLEY INTO NORTHERN NEW ENGLAND...

...SUMMARY...
Scattered severe thunderstorms capable of producing both damaging
winds and large hail should develop Saturday afternoon and evening
from parts of the southern Plains into the mid Mississippi Valley,
Midwest, and Northeast.

...Discussion...

Large-scale pattern is not expected to change appreciably through
Saturday with a corridor of strong southwesterly flow at mid and
high levels forecast to extend from the central Rockies-mid MS
Valley-Great Lakes. Most of this stronger flow will remain along the
cool side of a notable cold front that will be oriented in a similar
fashion, but displaced 100-200 mi southeast of the jet.

Early this morning a weak short-wave trough was evident over UT.
This feature will shear northeast with minimal suppression to the
height field, except late in the period over northern latitudes. As
a result, warm-sector heating and weak low-level warm advection will
be the mechanisms instrumental in convective development. At 0530z,
scattered thunderstorms are gradually expanding north of the front
from northern OK-mid MS Valley-lower MI. Isentropic ascent will
continue to aid elevated convection through sunrise and hail remains
a threat with the most robust storms. With time, clusters may
ultimately evolve which could lead to locally enhanced convergence
for potentially strong/severe thunderstorms as the boundary layer
begins to warm by late morning. Models suggest a weak surface wave
may form near the Arklatex which could lead to more concentrated
storms just downstream over AR. With a weak LLJ focused across AR
into southern IL this may be a corridor where a tornado or two could
evolve if supercells form. At this time the scenario is not clear
enough to increase tornado probabilities across this region.

Otherwise, a seasonally moist PW plume will extend from TX-OH
Valley-northern New England. Scattered strong to potentially severe
thunderstorms are expected along this corridor where modest
shear/buoyancy will be noted. Isolated hail and locally strong winds
are the primary risks.

..Darrow/Moore.. 05/21/2022

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SPC May 21, 2022 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
1253 AM CDT Sat May 21 2022

Valid 221200Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL
LOUISIANA...SOUTH-CENTRAL MISSISSIPPI AND WESTERN ALABAMA...

...SUMMARY...
Isolated severe storms with wind damage and hail will be possible
across parts of the Northeast on Sunday. A marginal severe threat
may also develop in parts of the lower Mississippi Valley and
central Gulf Coast states.

...Northeast/Mid-Atlantic...
West-southwest to southwesterly mid-level flow will be in place on
Sunday across much of the central and eastern U.S. A shortwave
trough will move northeastward across the lower Great Lakes. At the
surface, a cold front will advance southeastward across the
Northeast. Ahead of the front, surface dewpoints in the 60s F will
result in moderate destabilization by afternoon. Thunderstorms are
forecast to first develop near the front on the western edge of the
moist airmass in western and northern New York during the early
afternoon. The storms are expected to move quickly eastward from
eastern New York into western and northern New England by late
afternoon. Forecast soundings ahead of the front around 21Z from
central Maine southwestward into western New England have MLCAPE
peaking in the 2000 to 2500 J/kg range. 0-6 km shear is forecast to
be in 30 to 40 knot range along this corridor, with 0-3 km lapse
rates peaking near 8.0 C/km. This should be favorable for multicells
with wind damage potential. Supercells with isolated large hail will
also be possible in areas that heat up the most. The severe threat
should be closely tied to the front, with the threat moving from
west to east across the region during the late afternoon and early
evening.

Further to the south into the Mid-Atlantic, a corridor of moderate
instability is forecast to develop by afternoon. Although
large-scale ascent will remain weak, MLCAPE in the 2000 to 3000 J/kg
range and 0-3 km lapse rates exceeding 8.0 C/km should be favorable
for marginally severe wind gusts. Hail may occur with the stronger
updrafts as well.

...Lower Mississippi Valley/Central Gulf Coast States...
West-southwesterly mid-level flow will be in place across much of
the southern U.S. on Sunday. At the surface, a cold front will
advance southeastward into the lower Mississippi Valley and central
Gulf Coast states. Surface dewpoints ahead of the front in the 70s
F, should result in moderate instability by afternoon from Louisiana
northeastward into central Mississippi and western Alabama. This
combined with steep low-level lapse rates may be enough for a
marginal wind-damage threat, with storms that form along and near
the front late Sunday afternoon.

..Broyles.. 05/21/2022

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SPC May 21, 2022 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
0222 AM CDT Sat May 21 2022

Valid 231200Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
TEXAS...

...SUMMARY...
Isolated wind damage and large hail will be possible across parts of
central Texas Monday afternoon and evening. Marginally severe storms
with strong wind gusts and hail could also occur across parts of
north and east Texas.

...Texas...
An upper-level trough is forecast to move eastward into the southern
and central High Plains on Monday. At the surface, a trough is
forecast to develop across central Texas. Ahead of the surface
trough, a moist and unstable airmass will be in place with surface
dewpoints from the upper 60s to the mid 70s F. In response, moderate
instability is expected across much of the moist sector by
afternoon. Although thunderstorm development will be possible across
a large portion of the southern Plains, the strongest convection is
expected along the western edge of the moderately unstable airmass.
Thunderstorms are forecast to increase in coverage during the
afternoon and move eastward into the stronger instability across the
Texas Hill country and north Texas. 

Forecast soundings Monday afternoon, near the axis of strongest
instability, have MLCAPE peaking in the 2500 to 3500 J/kg range. 0-6
km shear is forecast to range from about 30 knots in north Texas to
around 40 knots in the Texas Hill Country. This combined with steep
low to mid-level lapse rates should be sufficient for an isolated
severe threat. Wind damage would be the greatest of the threats if
an organized line segment can develop. If cells remain more
discrete, then supercell development will be possible. At this time,
the models show the best severe-weather parameters over southwest
and central Texas, where there could be a slightly greater potential
for wind damage and isolated large hail than further to the north.
If tomorrow's model runs continue to show more potential for severe
storms in central and southwest Texas on Monday, then a slight could
be added in an upcoming outlook.

..Broyles.. 05/21/2022

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SPC May 21, 2022 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook
      
Day 4-8 Outlook Image
Day 4-8 Convective Outlook RESENT 1
NWS Storm Prediction Center Norman OK
0359 AM CDT Sat May 21 2022

Valid 241200Z - 291200Z

...DISCUSSION...
...Tuesday/Day 4 to Thursday/Day 6...
An upper-level trough is forecast to move into the southern High
Plains on Tuesday. Ahead of the trough, a moist airmass will be
located across parts of central and east Texas, where moderate
instability is expected to develop by afternoon. Thunderstorm
formation will be possible over a large part of the southern Plains
eastward into the lower Mississippi Valley. An MCS may organize
along the northern edge of the stronger instability and pose a
severe threat during the afternoon and evening. At this time, there
is a large spread in the model solutions concerning where this MCS
could potentially form. This combined with the fact that mesoscale
influences will be a strong contributor to any severe threat, makes
for a lot of uncertainty. There will likely be need for a severe
threat area once the model solutions key in on a specific area with
greater potential.

On Wednesday, the upper-level trough is forecast to move slowly
eastward across the southern Plains. A moist and unstable airmass
should be in place from the Texas Coastal Plains eastward into the
central Gulf Coast states. Moisture advection will also take place
across the Ohio and Tennessee Valleys. A potential for strong
thunderstorm development will be possible along the northern edge of
the stronger instability, somewhere from east Texas eastward into
lower Mississippi Valley. Other strong thunderstorms could form
ahead of a cold front from the mid Mississippi Valley northeastward
into the Ohio Valley. Mesoscale influences and the distribution of
instability will again have a strong impact any severe threat that
develops Wednesday afternoon.

The upper-level trough is forecast to move into the lower to mid
Mississippi Valley on Thursday, as a moist airmass remains to the
east of the system. Thunderstorm development will be possible over a
large area from the central Gulf Coast states northward into the
Ohio Valley. Isolated strong thunderstorms will again be possible
along this corridor in areas that heat up the most, and in areas
where mesoscale factors are favorable.

From Tuesday to Thursday, predictability is too low to add a threat
area, due to the uncertainties previously mentioned.

...Friday/Day 7 and Saturday/Day 8...
On Friday and Saturday, the upper-level system is forecast to move
slowly eastward toward the East Coast. Thunderstorms will again be
possible each day across a broad area ahead of the system. Although
strong thunderstorms will be possible in some areas of the eastern
U.S. each afternoon and evening, the range in the forecast is too
far out to make any solid conclusions concerning specific threat
areas.

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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
1247 AM CDT Sat May 21 2022

Valid 211200Z - 221200Z

...Synopsis...
Early-morning surface observations reveal a cold front continuing to
push southward across the southern Plains. Behind this front,
pressure rises denote a building surface high across the central
High Plains, which is forecast to migrate into the southern Plains
over the next 24 hours. Consequently, weaker winds and cooler
temperatures will limit fire weather concerns compared to previous
days for most of the southern High Plains. Regional fire weather
concerns are expected for parts of the Southwest where warm/dry
conditions will persist. 

...Central to southern New Mexico...
Poor overnight RH recovery is noted across central to southern NM
with RH values generally between 10-20%. These dry conditions will
linger into the afternoon as the cold front stalls to the east due
to terrain blocking. Despite persistent zonal flow aloft, the
building surface high will limit any lee troughing to northern NM
where a weak low is noted in morning observations. This low will
likely undergo slight thermally-induced deepening through the day.
As a result, the tightening regional pressure gradient over
central/southern NM and parts of far eastern AZ should support
sustained winds between 15-20 mph. Diurnal RH reductions to well
below 15% are likely, and will support elevated fire weather
conditions. Localized critical conditions are possible, but are most
likely to occur through the lower desert terrain (roughly along the
I-25 corridor) where fuel loading is minimal. Additionally, poor
upper-level wind support will mitigate the potential for
sufficiently widespread/persistent critical conditions.

..Moore.. 05/21/2022

...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
0145 AM CDT Sat May 21 2022

Valid 221200Z - 231200Z

...Synopsis...
Fire weather concerns appear likely for Sunday afternoon across
parts of the Southwest and Four Corners region. An upper-level
disturbance embedded within the mean trough will approach the Four
Corners region on Sunday. Falling heights aloft will support surface
pressure falls over the central Rockies, which should boost regional
pressure-gradient winds from the eastern Great Basin, into the
Southwest, and across the High Plains. Increasing winds within an
antecedent dry air mass with receptive fuels will support at least
elevated fire weather concerns, though some regional details remain
uncertain. 

...Arizona into New Mexico...
Sustained winds between 15-20 mph appear likely across eastern AZ
into western NM by late Sunday afternoon amid surface pressure falls
to the north across UT/CO. An antecedent dry air mass will support
widespread RH reductions to 10-15% by peak heating, and already
receptive fuels will contribute to the fire weather potential. Good
agreement among ensemble and deterministic solutions yields high
confidence in elevated conditions, and areas of critical conditions
are possible across parts of northeast AZ/northwest NM where
sustained winds may exceed 20 mph. Somewhat weak mid/upper-level
winds limits confidence in this scenario at this time, but a
Critical risk area may be introduced if the potential for widespread
sustained 20+ mph winds increases. 

...Eastern Nevada into Utah...
Most deterministic solutions hint at areas of 15-20 mph winds
overlapping with 15-25% RH values across eastern NV into much of UT
Sunday afternoon. However, considerable spread in both the coverage
and duration of these conditions is noted, and similar spread is
observed in ensemble solutions. Furthermore, the coverage of
receptive fuels across this region is patchy based on recent ERC
analyses, so the overlap of elevated fire weather conditions with
receptive fuels is somewhat unclear. This uncertainty precludes
highlights at this time, but the potential for elevated fire weather
conditions is noted and a risk area may be introduced in subsequent
forecast updates. 

...Central/Southern High Plains...
A dry return-flow pattern is expected for Sunday afternoon with
winds increasing to 15-20 mph from western OK and the TX Panhandle
into western KS/eastern CO. The recent frontal intrusion into the
Southern Plains will limit moisture return with 20-30% RH likely
across the region. However, ongoing rainfall (as of early Saturday
morning) across parts of western OK, northwest KS, and eastern CO
introduce some uncertainty regarding fuel status by Sunday
afternoon. Fuel trends will be monitored over the next 24 hours, and
highlights may be needed if confidence in the fire weather potential
increases. 

...Sacramento Valley...
A northerly, down-valley flow regime is expected Sunday afternoon
for the Sacramento Valley. An unseasonably dry air mass currently
over northern CA (where dewpoints are currently near the 10th
percentile for mid/late May) will linger into Sunday and support RH
reductions down to 15-20%. Ensemble guidance suggests winds between
10-15 mph are likely, which may support areas of elevated fire
weather concerns.

..Moore.. 05/21/2022

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

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