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LU9DCE > ALERT 11.08.20 16:15z 293 Lines 17100 Bytes #999 (0) @ WW
BID : 23264_LU9DCE
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Subj: STORM PREDICTION CENTER 11 08
Path: HB9ON<IW8PGT<IZ3LSV<DB0ERF<DB0RES<ON0AR<VK6HGR<GB7CIP<N7HPX<LU9DCE
Sent: 200811/1600Z 23264@LU9DCE.TOR.BA.ARG.SOAM LinBPQ6.0.20
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
LINUX - HELLOCODELINUX@GMAIL.COM
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SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1224
AM CDT Tue Aug 11 2020
Valid 111200Z - 121200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF SOUTH DAKOTA AND NEBRASKA...
...SUMMARY... Scattered strong/severe convection is expected across
portions of the Plains from late afternoon into the overnight hours,
especially across portions of South Dakota and Nebraska. Hail and
wind are the primary threats. Marginally severe storms are also
possible across parts of the mid-South and over northern Maine.
...South Dakota/Nebraska...
Early-evening water-vapor imagery depicts a short-wave trough along
the ID/WY border, shifting east in line with 00z model guidance.
This feature is forecast to translate east across WY into western
SD/NE Panhandle by mid-late afternoon. In response, boundary-layer
moisture that has been shunted south into KS should be drawn
northwest as lee trough becomes established from the western Black
Hills into eastern CO. Strong boundary-layer heating is expected
along the lee trough and forecast soundings suggest convective
temperatures will be breached around 21-22z. 500mb flow on the order
of 30-35kt will be maintained at this latitude, along the southern
edge of the stronger westerlies. As a result, forecast shear appears
at least somewhat supportive of supercell structures. Latest CAMs
are reasonably consistent with scattered convection developing ahead
of the short wave with eastward propagating storms across SD during
the overnight hours, being maintained by a LLJ and warm advection.
...Mid-South...
High-Plains convection that developed from western KS into the TX
Panhandle is shifting east across south-central KS/central OK early
this morning. Remnants of this activity should migrate into eastern
OK by daybreak. It's possible a weak MCV could evolve along the
northern extent of this convection, and this may encourage downstream
convection from southeast OK into AR later in the day. Models also
suggest a weakness in the mid-level height field will evolve over
the Ozarks and drift south. This will also prove favorable for
scattered storms as a reservoir of instability currently resides
across this region that has not been overturned.
...Northern Maine...
Remnants of Monday's Derecho have progressed across the OH Valley and
mostly dissipated. However, MVC remains intact over northern lower
MI and an associated short-wave trough is ejecting toward southern
ON. This feature should translate north of the international border
into southwestern QC by 18z. Scattered convection should evolve
ahead of this short wave and the southern extent of this activity
could spread across northern Maine. Locally strong winds would be
the primary threat with these storms.
..Darrow/Squitieri.. 08/11/2020
SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100
AM CDT Tue Aug 11 2020
Valid 121200Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS...
...SUMMARY... Severe thunderstorms with wind damage and isolated
large hail will be possible across parts of the northern Plains on
Wednesday afternoon and evening. Marginally severe thunderstorms
will be possible in parts of the lower to mid Missouri Valley.
...Northern Plains... An upper-level trough will move across the
northwestern U.S. on Wednesday as southwest mid-level flow becomes
established across the northern Plains. A 55 to 65 kt mid-level jet
will move northeastward from the northern Rockies into southern
Saskatchewan. At the surface, a cold front will advance eastward
across the northern High Plains. A moist airmass will be in place
across much of the Dakotas where moderate to strong instability is
forecast by afternoon. Thunderstorms appear most likely to develop
across far western North Dakota by late afternoon with this activity
moving east-northeastward into west-central North Dakota during
the evening.
NAM and GFS Forecast soundings in western North Dakota near and to
the north of Dickinson for 00Z/Thursday have surface dewpoints in
the lower 60s F with MLCAPE around 2000 J/kg. 0-6 km shear values
are forecast to be near 30 kt with 700-500 mb lapse rates near
8.5 C/km. This environment would be marginal for supercells. But
organized multicells or semi-organized rotating storms will be
possible. Isolated large hail and wind damage will be the primary
threats.
The main problem with this forecast is model inconsistency concerning
convective coverage. 700 mb temperatures are forecast to gradually
warm during the day across western North Dakota, which would
inhibit convective initiation. The time most likely for convective
initiation would be during the late afternoon or early evening as
low-level flow ramps up across the region. Although the potential for
severe thunderstorm development appears conditional, the presence of
the mid-level jet to the northwest should help increase convective
coverage in the evening. For this reason, have placed a small slight
risk far parts of the northern Plains for this outlook.
...Lower to Mid Missouri Valley... A shortwave ridge is forecast to
move eastward across the central Plains on Wednesday. A moist and
unstable airmass will be in place beneath the ridge from eastern
Kansas north-northwestward into southern South Dakota. Due to the
upper-level ridge and limited large-scale ascent, convective coverage
is expected to remain isolated. In spite of warm air aloft, 0-6 km
shear is forecast to be in the 20 to 30 kt range near the upper-level
ridge axis. This combined with steep lapse rates may be enough for
a marginal wind damage and hail threat late Wednesday afternoon.
..Broyles.. 08/11/2020
SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0216
AM CDT Tue Aug 11 2020
Valid 131200Z - 141200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS...
...SUMMARY... Severe thunderstorms with isolated large hail and wind
damage will be possible in parts of the northern Plains Thursday
afternoon and evening. Marginally severe thunderstorms will be
possible from parts of the central Plains and lower Missouri Valley
northward into the the lower to mid Missouri Valley.
...Northern Plains... An upper-level trough is forecast to move
eastward across the northwestern United States on Thursday as
southwest mid-level flow is maintained in the northern Plains. At
the surface, a cold front is forecast to move eastward across the
northern Plains with a moist airmass located ahead of the front
from eastern Nebraska northward into the eastern Dakotas. Surface
dewpoints from the mid 60s to lower 70s F will likely result in
moderate to strong instability by afternoon. Although a cap should
suppress convective development during the day, thunderstorms appear
likely to form along and just ahead of the front during the late
afternoon and early evening as the cap weakens. Model forecasts
suggest that a line of thunderstorms will organize during the
early evening and move across eastern North Dakota and northeastern
South Dakota.
NAM and GFS Forecast soundings in eastern North Dakota at 21Z on
Thursday show MLCAPE in the 2000 to 3000 J/kg range and have 0-6 km
shear of 30 to 35 kt. This combined with mid-level lapse rates near
8.5 C/km would support a severe threat. Supercells with isolated
large hail would be possible with discrete cells that form ahead
of the front near any instability maximum. A potential for wind
damage would be most likely with line segments that organize along
the front. The severe threat should continue into the early and
mid evening, eventually affecting parts of northwest Minnesota.
One problem with the forecast is that the models are not in agreement
concerning convective coverage. Of the NAM, GFS and ECMWF, the
ECMWF is the most aggressive solution concerning this issue.
This solution suggests that MCS development will be possible
across parts of the northern Plains by Thursday evening. Due to
this possibility, a slight risk area has been introduced.
...Central Plains/Lower to Mid Missouri Valley... A slow-moving
upper-level ridge is forecast to be located in the central Plains
on Thursday. Beneath the ridge, a very moist airmass will result in
moderate to strong destabilization by afternoon. Although a cap is
forecast across the instability corridor, isolated thunderstorms
may be able to overcome the cap during the late afternoon and
early evening. Any cells that can become rooted in the stronger
instability could produced marginally severe wind gusts and hail,
mainly due to the steep lapse rates in place.
..Broyles.. 08/11/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0252 AM CDT Tue Aug 11 2020
Valid 141200Z - 191200Z
...DISCUSSION... ...Friday/Day 4 and Saturday/Day 5... The
medium-range models including the ECMWF, GFS, UKMET and Canadian are
in general agreement, moving a cold front from the northern Plains
into the Upper Mississippi Valley on Friday. Thunderstorm development
will be possible along and ahead of the front during the afternoon
and evening. The models suggest that instability and deep-layer shear
will be sufficient for a severe threat. However, uncertainty exists
concerning the distribution of instability and timing of the front,
so a forecast area can not be added at this time.
From Saturday into Saturday night, the models move an upper-level
trough across the north-central states. An associated cold front
is also forecast to move southeastward across parts of the Upper
Midwest. Thunderstorms will again be possible along the front,
with some having the potential to be severe. The model solutions
vary on the exact timing of the front. For this reason, uncertainty
is substantial concerning the magnitude and spacing of any severe
threat for Saturday.
...Sunday/Day 6 to Tuesday/Day 8... From Sunday to Tuesday, the
models move an upper-level trough across the Great Lakes region as
a cold front advances southeastward from the central U.S. into the
Southeast. A moist airmass is forecast ahead of the front which
could make isolated severe thunderstorms possible each afternoon
and evening. The severe threat would be possible from near the front
southeastward across parts of the unstable airmass. Considering that
deep-layer shear is forecast to be weak across much of the central
and southeastern U.S. any wind damage threat would probably remain
unorganized. However, uncertainty is considerable late in the day
4 to 8 period.
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0206 AM CDT Tue Aug 11 2020
Valid 111200Z - 121200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN WASHINGTON
AND NORTHERN OREGON...
...Synopsis... A mid-level trough will amplify across the Pacific
Northwest throughout the period, with strengthening flow aloft
overspreading a warming/mixing boundary layer through the afternoon
hours. The stronger flow aloft is expected to mix down to the surface
to encourage dry and windy conditions supportive of wildfire spread
across portions of the Pacific Northwest and northern Rockies.
Large-scale lift associated with the mid-level trough is also
expected to support thunderstorm development within a west-east
band of mid-level moisture across the northern Great Basin into the
central Rockies, where dry lightning may also encourage new wildfire
ignitions. Finally, modest flow aloft associated with a small impulse
overspreading the southwest CONUS may also support surface dry and
windy conditions, where some wildfire spread potential may be noted
by afternoon peak heating.
...Pacific Northwest and parts of the Northern Rockies...
By afternoon, downslope along the lee of the Cascades will promote
at least 15 mph sustained westerly winds and 15-25% RH across much
of the Columbia and Harney Basins. High-resolution model guidance
continues to indicate Critical conditions (with 20 mph sustained
westerly winds) across southern parts of the Columbia Basin, along
the Washington/Oregon border, with a Critical area maintained.
Farther east in the Northern Rockies, downslope flow combined
with downward momentum transport, should contribute to widespread
Elevated conditions (15+ mph sustained westerly winds and 10-25%
RH) during the afternoon hours. Locally critical conditions may
briefly occur in the most terrain favoring locations, including
the Snake River Plain and Great Divide Basin.
...Northern Great Basin into the Central Rockies... With diurnal
heating and increasing upper support, isolated to potentially
scattered thunderstorm development is expected, especially
to the lee of the Sierra in northern Nevada. Storms will be
high-based given a deep sub-cloud layer. Training storms and slow
storm speeds may allow for some localized appreciable rainfall
accumulations, precluding a scattered dry thunderstorm upgrade.
Farther east, along the aforementioned band of mid-level moisture,
isolated dry thunderstorms are expected as far east as central
Wyoming. Aforementioned dry/windy conditions across Wyoming may
serve to aggravate fire starts associated with dry strikes.
...Portions of the Southwest CONUS... Guidance continues to indicate
widespread Elevated to locally Critical dry/windy surface conditions
across southwest portions of the Colorado Plateau, with 15-20 mph
sustained southwesterly winds overlapping with 10-20% RH for at least
a few hours during the afternoon. The primary negating factor in
upgrading to Critical is the lack of more discernible upper-support.
..Squitieri.. 08/11/2020
...Please see www.spc.noaa.gov/fire for graphic product...
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0209 AM CDT Tue Aug 11 2020
Valid 121200Z - 131200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHEAST OREGON INTO
NORTHWEST NEVADA...
...Synopsis... The mid-level trough across the Pacific Northwest
(mentioned in Day 1) is expected to progress eastward towards
the northern Rockies during Day 2/Wednesday. Downward momentum
transport of the stronger flow aloft via a well-mixed boundary layer
will encourage dry and windy surface conditions across portions of
the northern Rockies southward into the central Rockies and Great
Basin, where conditions favorable for wildfire spread will be a
concern. Deep-layer lifting of a mid-level moisture plume will also
encourage thunderstorm development into the central/northern Rockies.
...Northern/central Rockies and Great Basin - Dry/Windy Conditions...
With the onset of diurnal heating, downward momentum transport and
downslope flow along higher terrain will encourage widespread 15+ mph
sustained southwesterly flow amidst 10-20% RH across lower terrain
areas in the Intermountain West. Western/central Montana into Nevada,
and central Wyoming into southern Nevada are the most likely regions
to see favorable surface wind/RH overlaps for prolonged periods
of time during the afternoon, where Elevated highlights have been
introduced. This is especially the case given the receptive fuels
in place from the central Rockies south/westward. Some terrain
favoring areas typically susceptible to enhanced surface winds may
experience locally Critical conditions by afternoon peak heating.
More widespread Critical conditions (20+ mph sustained westerly
winds and 15% RH) are expected along the lee of the Sierra by
mid to late afternoon, hence the Critical highlight. With dry
strikes likely across portions of the northern Great Basin into
the central/northern Rockies on Day 1, concern exists for Day 2
dry/windy conditions to enhance wildfire spread by aggravating new
lightning-induced fire starts.
...Northern Great Basin into the central/Northern Rockies - Dry
Thunderstorms... Modestly strong mid-level flow and moisture
will overspread a deepening dry boundary layer, where coverage
of high-based thunderstorms is expected to increase through the
afternoon. Storm speeds are expected to be a bit faster than previous
days, with dry strikes also likely occurring over very to critically
receptive fuels. As such, new fire starts are likely with any dry
strikes that may occur, warranting the introduction of an isolated
dry thunderstorm delineation.
..Squitieri.. 08/11/2020
...Please see www.spc.noaa.gov/fire for graphic product...
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El pasado no es sino la prefiguracion del futuro.
-- Eliade.
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