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LU9DCE > ALERT 02.12.20 16:05z 223 Lines 12476 Bytes #999 (0) @ WW
BID : 42227_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 02 12
Path: HB9ON<IW8PGT<LU4ECL<JE7YGF<VE3UIL<LU9DCE
Sent: 201202/1601Z 42227@LU9DCE.TOR.BA.ARG.SOAM LinBPQ6.0.20
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
CASTILLOEDUARDO@OUTLOOK.COM.AR
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SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1158
PM CST Tue Dec 01 2020
Valid 021200Z - 031200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ALONG THE MIDDLE
AND UPPER TEXAS COAST...AND COASTAL SOUTHWESTERN LOUISIANA...
...SUMMARY... A couple of severe thunderstorms are possible over
the middle/upper Texas Coast and far southwest Louisiana today.
...Synopsis... A large upper cyclone over the northeastern
U.S. is forecast to shift northward into Quebec today, as a
second evolves/lingers over the southern Rockies/southern Plains.
Meanwhile, sharp ridging will remain over the West, though a
short-wave trough is expected to approach the West Coast late in
the period.
At the surface, high pressure will prevail over much of the country,
as the main surface low retrogrades across northern Quebec. A much
weaker surface low is forecast to shift northeastward along the
western Gulf Coast through the period.
...Middle and Upper Texas Coast to southwestern Louisiana...
Showers and embedded thunderstorms are expected to evolve early
this morning, prior to the start of the period -- largely over the
western Gulf, but with elevated convection spreading northward
across portions of East Texas by the start of the period. As a
weak surface low shifts northeastward near or just offshore during
the day, southeasterly/easterly low-level flow should permit
some inland advance of a partially modified Gulf boundary layer.
Combined with very limited heating, mixed-layer CAPE of 500 J/kg
could evolve across portions of the Upper Texas Coast and eventually
coastal southwestern Louisiana, with perhaps 1000 J/kg along the
Middle Texas Coast. This will support an increase in convection
during the late morning and into the afternoon, particularly over
the immediate coastal counties. While relatively weak lapse rates
aloft will likely limit hail risk, a couple of stronger storms will
be capable of producing gusty/possibly damaging winds.
Additionally, veering of the low-level flow with height near the
low and attendant warm front, beneath strengthening mid-level
west-southwesterlies will result in shear profiles supportive of
updraft rotation -- including low-level circulations and possibly
an inland tornado with one or two sustained storms.
Limited severe risk may spread eastward across coastal southern
Louisiana into the evening/overnight while gradually diminishing
over coastal Texas, though more widespread/intense storms should
remain largely offshore through the end of the period.
..Goss/Moore.. 12/02/2020
SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1245
AM CST Wed Dec 02 2020
Valid 031200Z - 041200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY... Isolated thunderstorms are possible across portions
of the Lower Mississippi Valley and Southeast on Thursday.
...Synopsis and Discussion... An elongated upper trough is forecast
to extend from the Mid MS Valley southwestward through the Southwest
early Thursday morning. A mature mid-latitude cyclone will be
embedded within this upper trough, starting the period centered over
eastern OK. The cyclone is expected to gradually shift northeastward
while evolving into an open wave. To the west of this cyclone, an
embedded shortwave is forecast to progress southwestward from the
AZ/NM border into northwest Mexico. Evolution of these systems will
result in long corridor of enhanced mid-level flow, from northern
Mexico into the Northeast States, throughout the eastern periphery
of the upper trough.
Occluded surface low associated with the upper cyclone will begin
the period over southeast OK before moving eastward and weakening
throughout the day. Secondary low will likely develop over the
immediate southern LA coast or just offshore early Thursday. This
low is expected to move eastward along the immediate coast or just
offshore throughout the period.
Isolated, predominantly elevated thunderstorms are possible along
and ahead of the occluded front as it moves gradually eastward
through the Lower MS Valley and into the Southeast throughout the
day. Given the anticipated location of the secondary surface low,
inland penetration of the warm sector will be minimal, limiting
the potential for surface-based storms. The strongest shear will
also be displaced north of the better instability. These factors
will keep the severe threat very low.
..Mosier.. 12/02/2020
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0208
AM CST Wed Dec 02 2020
Valid 041200Z - 051200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY... Isolated thunderstorms are possible across the
Southeast, Florida, and the eastern Mid-Atlantic States on Friday.
...Synopsis... A positively tilted shortwave trough will likely
extend from the Mid MS Valley southwestward into north TX early
Friday morning. Expectation is for this shortwave to progress
eastward through the TN Valley and Southeast, eventually moving into
the Mid-Atlantic States by early Saturday morning. As the shortwave
progresses eastward, it will pivot into a negative tilt while also
developing strong mid-level flow from its based throughout its
eastern periphery.
Surface low accompanying this shortwave is forecast to begin the
period over coastal MS/AL before quickly moving northeastward. This
low is expected to end the period over central VA. Modest moisture
advection is anticipated ahead of this low and attendant cold front,
with low 60s dewpoints expected across the FL Panhandle Friday
afternoon and across the coastal Mid-Atlantic Friday night into
Saturday morning. Even with this moisture, abundant clouds will
limit heating and poor lapse rates will suppress overall buoyancy.
Wind profiles support a severe risk with any sustained, surface-based
updrafts, but occurrence of such an updraft will depend on mesoscale
factors difficult to predict at this forecast length. Most likely
locations for severe storms currently appear to be over the central
FL Panhandle on Friday afternoon and along the Carolina coast late
Friday night/early Saturday. However, given the predictability
issues, no areas will be delineated with this forecast.
..Mosier.. 12/02/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0347 AM CST Wed Dec 02 2020
Valid 051200Z - 101200Z
...DISCUSSION... Severe potential appears minimal this weekend
through at least the middle of next week. Shortwave trough over
the northern Mid-Atlantic States early D4/Saturday is expected to
continue progressing northeastward off the Northeast coast. Another
shortwave trough is expected to drop from the northern Plains/Upper
MS Valley into the Mid MS/Lower OH Valley on D5/Sunday and D6/Monday,
with another shortwave likely following. This series of shortwave
troughs coupled with persistent upper ridging across the western
CONUS will help maintain a dry, stable air mass east of the Rockies
through at least D8/Wednesday.
The only severe potential appears to be early on D4/Saturday from the
Carolina coast into the Delmarva. Some of the guidance has trended
less progressive with a shortwave trough and its attendant surface
low, resulting in modest low-level moisture ahead of an approaching
cold front. Variability within the guidance curtails predictability,
but even the less progressive solution yields only limited overall
severe potential.
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
1231 AM CST Wed Dec 02 2020
Valid 021200Z - 031200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF COASTAL SOUTHERN
CALIFORNIA...
...Synopsis... A fairly strong region of surface high pressure,
recently analyzed over the northern Rockies, is forecast to gradually
shift southward today. This feature will generally follow behind an
upper-level low as it continues to dig southward and deepen through
the day. As the surface high migrates to the south, offshore pressure
gradient winds are forecast to increase across southern California
(where warm and dry conditions have been ongoing for the past
several days).
...Southern California... Surface observations from the higher
elevations of Los Angeles and Ventura counties show poor overnight
RH recoveries (RH values in the low teens) and sustained winds
in the upper teens for a few locations. These elevated conditions
will persist through the day and most likely increase in coverage
as the aforementioned surface high shifts further into the Great
Basin. Initially isolated pockets of critical conditions will also
see an increase in coverage across southern CA, especially this
evening after roughly 03 UTC Thursday when mid-level winds are
forecast to increase and may yield stronger wind gusts (up to 35-45
mph in a few locations). Guidance remains in good agreement that the
12-15 UTC Thursday period should see the strongest pressure-gradient
winds, but areas of persistent critical conditions appear likely
as early as late tonight and into the early morning hours Thursday.
..Moore.. 12/02/2020
...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
0200 AM CST Wed Dec 02 2020
Valid 031200Z - 041200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF COASTAL SOUTHERN
CALIFORNIA...
...Synopsis... Fire weather concerns will continue for southern
California where a moderate Santa Ana wind event is expected early
Thursday. This event will largely be driven by the reinforcement
of surface high pressure over the central Great Basin as a mid to
upper-level shortwave trough propagates southward over the Southern
Rockies on the periphery of an upper-level low over the Southern
Plains. Critical fire weather conditions appear likely for the
higher elevation of coastal southern California, areas of elevated
fire weather conditions may occur over southern Arizona.
...Southern California... Early morning guidance remains in fairly
good agreement that the strongest pressure-gradient winds will
occur during the 12-15 UTC period Thursday morning, but may linger
through 18 UTC before diminishing somewhat during the afternoon
hours. As such, critical conditions will likely be ongoing from
Los Angeles/Ventura counties southward to the Mexican border
with elevated conditions on the periphery. Sustained wind speeds
between 20-40 mph (with gusts up to 70 mph) will be possible for
a few locations in the higher terrain. Given forecast RH values
in the low teens and single digits, a few pockets of extremely
critical conditions are possible. Hi-res guidance suggests
that the most likely locations for this to occur are portions
of Los Angeles/Ventura counties and perhaps areas of San Diego
county. Widespread elevated conditions, with embedded areas of
critical conditions, will likely persist through at least early
Friday morning.
...Southern Arizona... Antecedent warm and dry conditions over
eastern AZ over the past few days have allowed for ERC values
to climb above seasonal normal for a few locations. With little
moisture return into the region, RH values in the teens, and
possibly single digits, appear likely for Thursday afternoon. A
general increase in pressure-gradient winds appears likely by the
afternoon hours across southeast AZ. Recent model solutions suggest
that the region of strongest winds may not coincide with the area of
lowest RH, but a few locations across southern AZ may see favorable
overlap of winds and RH to support pockets of elevated fire weather
conditions. Given the uncertainty regarding the coverage of these
conditions, no additional highlights are introduced.
..Moore.. 12/02/2020
...Please see www.spc.noaa.gov/fire for graphic product...
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Twenty Percent of Zero is Better than Nothing.
-- Walt Kelly
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