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LU9DCE > ALERT 13.08.20 02:07z 313 Lines 18201 Bytes #999 (0) @ WW
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Subj: STORM PREDICTION CENTER 12 08
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Sent: 200813/0201Z 23315@LU9DCE.TOR.BA.ARG.SOAM LinBPQ6.0.20
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
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SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1128
AM CDT Wed Aug 12 2020
Valid 121630Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND EVENING ACROSS PARTS OF WESTERN AND NORTHERN NORTH DAKOTA...
...SUMMARY... Widely scattered strong storms may impact portions of
the the northern and central Great Plains late this afternoon into
tonight, accompanied by at least some risk for severe hail and wind.
Other thunderstorms with locally strong wind gusts are possible
near and east of the Blue Ridge Mountains into the northern Mid
Atlantic coast vicinity.
...Synopsis... A belt of westerlies emanating from northern
mid-latitude Pacific has undergone some amplification, and
this appears likely to transition eastward near/north of the
Canadian/U.S. border today through tonight. This includes
large-scale troughing across western Canada and the Pacific
Northwest, gradually shifting east of the Canadian and northern
U.S. Rockies, through the Canadian Prairies and higher portions of
the northern U.S. Great Plains. Downstream ridging is forecast
to continue to build across lower portions of the northern Great
Plains, Upper Midwest and adjacent Great Lakes region through the
Hudson Bay vicinity.
In lower latitudes, mid-level subtropical ridging will remain
influential across much of the central and southern tier of the U.S.,
including a prominent high centered over parts of the Southwest
into the southern Great Plains.
Steep lower/mid tropospheric lapse rates associated with a plume
of warm and capping elevated mixed-layer air will be maintained
across much of the Great Plains. Seasonably high moisture content
lingers south of a weak surface front extending across parts of
the Northeast into the Ohio Valley, and generally to the east of
weak mid/upper troughing within the larger-scale ridging across
the lower Mississippi Valley.
...Great Plains... Coverage of thunderstorm development and
associated severe weather potential remain unclear for today
through tonight. Stronger forcing for ascent associated with a
short wave impulse migrating northeastward out of the base of the
larger-scale troughing appears likely to remain mostly north of the
international border, but could perhaps extend southward into the
vicinity of lee surface troughing across parts of northwestern North
Dakota late this afternoon and evening. Otherwise, the lee surface
trough extending southward through central portions of the higher
plains could provide a focus for widely scattered late afternoon and
early evening thunderstorm initiation. Additional thunderstorms
may initiate, aided by warm advection, later tonight, east of the
warmer and more strongly capping elevated mixed-layer air across
parts of northern and central Minnesota, as well as portions of
the central Great Plains.
Where storms form, thermodynamic profiles characterized by steep
mid-level lapse rates and sizable CAPE, coupled with perhaps modest
shear, may provide support for severe hail and locally strong
surface gusts.
...Northern Mid Atlantic into central Appalachians... Orographic
forcing along the Appalachians may provide the primary support
for thunderstorm initiation this afternoon, along with perhaps
weak pre-frontal low-level convergence extending east of the higher
terrain, across southern Pennsylvania into the northern Mid Atlantic
coast region. Although deep-layer ambient mean flow is generally
on the order of 10 kt or less, seasonably high moisture content and
sizable CAPE may contribute to heavy precipitation loading and the
risk for potentially damaging wind gusts in the stronger storms.
..Kerr/Cook.. 08/12/2020
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252
PM CDT Wed Aug 12 2020
Valid 122000Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND EVENING ACROSS PARTS OF WESTERN AND NORTHERN NORTH DAKOTA...
...SUMMARY... Widely scattered strong storms may impact portions of
the the northern and central Great Plains late this afternoon into
tonight, accompanied by at least some risk for severe hail and wind.
Other thunderstorms with locally strong wind gusts are possible
near and east of the Blue Ridge Mountains into the northern Mid
Atlantic coast vicinity.
No changes were made to the previous outlook.
..Jewell.. 08/12/2020
.PREV DISCUSSION... /ISSUED 1128 AM CDT Wed Aug 12 2020/
...Synopsis... A belt of westerlies emanating from northern
mid-latitude Pacific has undergone some amplification, and
this appears likely to transition eastward near/north of the
Canadian/U.S. border today through tonight. This includes
large-scale troughing across western Canada and the Pacific
Northwest, gradually shifting east of the Canadian and northern
U.S. Rockies, through the Canadian Prairies and higher portions of
the northern U.S. Great Plains. Downstream ridging is forecast
to continue to build across lower portions of the northern Great
Plains, Upper Midwest and adjacent Great Lakes region through the
Hudson Bay vicinity.
In lower latitudes, mid-level subtropical ridging will remain
influential across much of the central and southern tier of the U.S.,
including a prominent high centered over parts of the Southwest
into the southern Great Plains.
Steep lower/mid tropospheric lapse rates associated with a plume
of warm and capping elevated mixed-layer air will be maintained
across much of the Great Plains. Seasonably high moisture content
lingers south of a weak surface front extending across parts of
the Northeast into the Ohio Valley, and generally to the east of
weak mid/upper troughing within the larger-scale ridging across
the lower Mississippi Valley.
...Great Plains... Coverage of thunderstorm development and
associated severe weather potential remain unclear for today
through tonight. Stronger forcing for ascent associated with a
short wave impulse migrating northeastward out of the base of the
larger-scale troughing appears likely to remain mostly north of the
international border, but could perhaps extend southward into the
vicinity of lee surface troughing across parts of northwestern North
Dakota late this afternoon and evening. Otherwise, the lee surface
trough extending southward through central portions of the higher
plains could provide a focus for widely scattered late afternoon and
early evening thunderstorm initiation. Additional thunderstorms
may initiate, aided by warm advection, later tonight, east of the
warmer and more strongly capping elevated mixed-layer air across
parts of northern and central Minnesota, as well as portions of
the central Great Plains.
Where storms form, thermodynamic profiles characterized by steep
mid-level lapse rates and sizable CAPE, coupled with perhaps modest
shear, may provide support for severe hail and locally strong
surface gusts.
...Northern Mid Atlantic into central Appalachians... Orographic
forcing along the Appalachians may provide the primary support
for thunderstorm initiation this afternoon, along with perhaps
weak pre-frontal low-level convergence extending east of the higher
terrain, across southern Pennsylvania into the northern Mid Atlantic
coast region. Although deep-layer ambient mean flow is generally
on the order of 10 kt or less, seasonably high moisture content and
sizable CAPE may contribute to heavy precipitation loading and the
risk for potentially damaging wind gusts in the stronger storms.
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1220
PM CDT Wed Aug 12 2020
Valid 131200Z - 141200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS NORTHWEST
MINNESOTA AND PARTS OF EASTERN NORTH DAKOTA...
...SUMMARY... Severe thunderstorms with large hail and damaging wind
are likely from North Dakota and northern South Dakota into northern
Minnesota, with isolated activity to the south and west. Isolated
severe storms are also possible from eastern Kansas and Oklahoma
into western Arkansas.
...Synopsis... An upper trough will move from the northern Rockies
into the northern Plains with the main speed max and strongest
lift moving across MT, WY, and the Dakotas from evening into the
overnight. Meanwhile to the south, an upper high will remain over
AZ,NM and west TX, with enhanced northwesterly winds aloft from
the central Plains into the Ozarks.
At the surface, a front is forecast to extend from the Red River
of ND/MN into western NE during the afternoon, with low pressure
redeveloping over eastern MT/WY in advance of the upper trough.
Southerly winds will maintain a moist and very unstable air mass east
of the low, from the Dakotas into MN. The combination of instability
and increasing lift should result in damaging wind and hail over
parts of the region.
...Northern Plains... MUCAPE in excess of 4000 J/kg is likely
over a large area from the eastern Dakotas into MN, east of the
front/wind shift and beneath persistent southerly 850 mb winds which
will increase boundary-layer moisture depth. Explosive development
is likely along the boundary, from northwest MN into eastern ND
and northeast SD. Damaging winds appear likely, and areas of large
hail will be possible as well despite weak shear, mainly with the
initial development.
Other severe storms with large hail are expected as the main lobe
of forcing for ascent moves from southeast MT into North Dakota.
Lengthening hodographs and cold temperatures aloft will favor large
hail, and a few of these storms may also produce damaging winds.
...KS/OK/MO/AR Borderlands... Enhanced midlevel northwesterlies of
35-40 kt are forecast from KS into AR, around the eastern periphery
of the upper ridge. Hot temperatures will develop from TX into
southwest OK near a surface low, with a very moist air mass farther
northeast where surface winds will remain backed. Strengthening warm
advection during the evening will likely induce a swath of storms
from southeast KS into AR, oriented northwest to southeast. Veering
winds with height in the effective cloud layer suggest isolated
supercells will be possible, most likely elevated. If sufficient
storm coverage can form, cold pool generation may support a few
strong gusts as well.
..Jewell.. 08/12/2020
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
1135 AM CDT Wed Aug 12 2020
Valid 121700Z - 131200Z
...CRITICAL FIRE WEATHER AREA FOR DRY AND WINDY CONDITIONS ACROSS
THE NORTHERN GREAT BASIN... ...CRITICAL FIRE WEATHER AREA FOR DRY
THUNDERSTORMS ACROSS EASTERN IDAHO AND WESTERN WYOMING...
...Dry Thunderstorms ID/WY... Scattered storm coverage is expected
across southern Idaho and western Wyoming. A dry boundary-layer
beneath a plume of 250-500 J/kg of MUCAPE will support scattered
dry strikes over very receptive fuels. As such, the scattered
dry thunder area will remain in place with no changes. The latest
forecast guidance depicts drier air across the northern Great Basin.
Because of the decrease in moisture content, the isolated dry thunder
area has been trimmed eastward toward the most likely corridor of
thunderstorm activity. The rest of the forecast remains valid with
no major changes.
..Lyons.. 08/12/2020
.PREV DISCUSSION... /ISSUED 0150 AM CDT Wed Aug 12 2020/
...Synopsis... A mid-level trough and associated stronger flow
aloft will traverse the northwest CONUS and overspread a deep,
dry boundary layer through the period. Downward momentum transport
of the stronger flow aloft, combined with downslope and channeled
flow in terrain favoring locations, are expected to support dry and
windy conditions across portions of the northern and central Rockies
into the Great Basin/Four Corners regions, where wildfire spread
concerns will exist. Large-scale lift and adequate instability along
a west-east band of mid-level moisture will also support isolated
to scattered thunderstorm development across the northern Great
Basin into the northern Rockies.
...Northern Great Basin into the Northern/Central Rockies - Dry
Thunderstorms... During the afternoon, the aforementioned lift
from the trough and diurnal heating should support thunderstorm
development atop a deep, dry sub-cloud layer, as depicted by multiple
model guidance members via classic inverted-V vertical profiles and
precipitable water values in the 0.50-0.75 inch range. Guidance
consensus also depicts enough instability within the -20 to -30C
layer to support several strikes, with relatively strong flow in the
sfc-500 mb layer to support faster moving storms. As such, a fair
number of strikes could be dry. While isolated dry thunderstorm
development is expected across much of the northern Great Basin
into the Central/Northern Rockies, the latest high-resolution
guidance depicts relatively greater storm coverage in southeast
Idaho into west-central Wyoming. Here, instability is maximized,
and fuels appear to be quite receptive to fire spread. A Critical
area for scattered dry thunderstorms was added to account for the
high dry strike coverage atop receptive fuels.
...Northern/Central Rockies into the Great Basin/Four Corners - Dry
and Windy Conditions... During the afternoon, the aforementioned
boundary-layer mixing and downslope flow will contribute
to widespread 15-20 mph sustained southwesterly surface winds
overlapping 10-20% RH across the northern Rockies southwestward into
the Great Basin, as well as from the central Rockies southwestward
into the Four Corners, necessitating the maintenance of Elevated
delineations. At least locally Critical conditions may also manifest
by afternoon peak heating in terrain favoring areas within both
Elevated areas.
For at least a few hours, relatively more widespread Critical
conditions (20+ mph sustained westerly surface winds along with
10-15% RH) are expected to the lee of the Sierra, with a Critical
delineation maintained along the Nevada/Oregon/Idaho border areas.
The Critical highlight also encompasses an area that has accumulated
a modest amount of rainfall, but with quite a few lightning
strikes on Day 1. While fuels might have been slightly dampened in
some spots, areas with minimum rainfall and multiple strikes are
especially sensitive to wildfire spread, as holdover fires from
Day 1 strikes may rapidly grow with the strong winds/low RH.
...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
0145 PM CDT Wed Aug 12 2020
Valid 131200Z - 141200Z
...CRITICAL FIRE WEATHER AREA FOR DRY AND WINDY CONDITIONS ACROSS
EASTERN IDAHO AND WYOMING...
...Snake River Plain and eastern Idaho... Model consensus has
increased enough that widespread elevated and critical fire
weather conditions appear likely over much of Idaho and Wyoming
Day2/Thursday. Mid-level flow along the southern end of the passing
trough will help increase mixing of higher momentum to the surface
bolstering sustained surface winds to 20-25 mph. The strengthening
flow in conjunction with receptive fuels and RH of 10 to 15% will
support any holdover fires from the previous few days of lightning
activity. The elevated and critical areas have been expanded
over eastern Idaho and western Wyoming where stronger winds and
the highest confidence in broad critical conditions are expected
to develop.
..Lyons.. 08/12/2020
.PREV DISCUSSION... /ISSUED 0212 AM CDT Wed Aug 12 2020/
...Synopsis... A mid-level trough will continue to slowly progress
eastward across the northern Rockies during the Day 2/Thursday
period. Stronger mid-level winds associated with the trough will
overspread a deep and dry boundary layer during the afternoon hours,
supporting dry and windy conditions conducive to wildfire spread
across portions of the central/northern Rockies.
...Central/Northern Rockies... From the far northeast corner of
the Great Basin, across the Snake River Plain, and into the Great
Divide Basin, at least 15 mph sustained westerly surface winds will
coincide with 10-20% RH, with an Elevated area introduced. However,
widespread 20-25 mph sustained westerly winds and near single-digit
RH may overlap for multiple hours during the afternoon across the
Great Divide Basin, with a Critical area added. At least locally
critical conditions may also occur across eastern parts of the Snake
River Plain, but the relatively confined nature of the Critical
conditions precludes a delineation, though a Critical area may
need to be added in future outlooks should guidance trend towards
greater coverage of such conditions.
The aforementioned dry and windy conditions may occur over spots that
may have experienced lightning on Day 1. The dry/windy conditions
may agitate holdovers, particularly in areas with the driest fuels
that have received minimal rainfall with lightning strikes.
...Lower Great Basin... Some of the latest model guidance
depicts locally to potentially widespread elevated conditions (15
mph sustained southwesterly winds overlapping 10-20% RH) across
portions of the lower Great Basin by afternoon peak heating. Given
the southward displacement of such conditions from the mid-level
shortwave trough and associated upper support, an Elevated
delineation has been withheld. An Elevated area addition may be
considered in future outlooks if model consensus shows a stronger
signal for widespread Elevated conditions.
...Please see www.spc.noaa.gov/fire for graphic product...
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Hacer preguntas es prueba de que se piensa.
-- Rabindranah Tagore. (1861-1941) Filosofo y escritor indio.
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