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LU9DCE > ALERT 25.11.20 16:24z 194 Lines 11308 Bytes #999 (0) @ WW
BID : 41714_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 25 11
Path: HB9ON<IW0QNL<VE2PKT<GB7YEW<LU9DCE
Sent: 201125/1600Z 41714@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 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256
AM CST Wed Nov 25 2020
Valid 261200Z - 271200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS
OF COASTAL/EAST TEXAS INTO LOUISIANA...
...SUMMARY... Isolated large hail may occur with thunderstorms
that develop across parts of east Texas and Louisiana, mainly from
Thursday night into early Friday morning.
...Coastal/East Texas into Louisiana... A positively tilted upper
trough is forecast to move southeastward over the western/central
CONUS, with the southern portion of this system closing off over
the Southwest late Thursday. Ahead of this feature, low-level
moisture return should occur across parts of coastal/east TX and
the lower MS Valley through the period. 700-500 mb lapse rates
around 7-7.5 C/km emanating from the higher terrain of west TX and
northern Mexico may overspread this region late Thursday into early
Friday morning. Latest guidance suggests MUCAPE around 1000-1500
J/kg may develop along/north of a warm front, with strengthening
west-southwesterly mid/upper-level flow with height that should
support 40-50 kt of deep-layer shear. Confidence has increased
that mainly elevated storms may form by late Thursday evening in a
modestly strengthening low-level warm advection regime over parts
of east TX into LA, generally to the north of the warm front. The
forecast combination of sufficient instability, steep mid-level lapse
rates, and strong speed shear in the mid/upper levels suggest that
isolated large hail may occur with any elevated supercells that can
develop. The potential for surface-based storms along the immediate
upper TX Coast and southwestern LA remains too uncertain to include
any probabilities for strong/gusty winds at this time.
...East Coast... A de-amplifying shortwave trough should move
across the Mid-Atlantic and southern New England on Thursday. A weak
surface low associated with this feature is forecast to fill further
through the day. An eastward-moving cold front should extend from
the Mid-Atlantic southwestward along parts of the East Coast and
into the Southeast. The stronger mid-level flow attendant to the
shortwave trough should remain displaced to the north of greater
low-level moisture across the Carolinas and Southeast. Although
enough weak instability may develop across eastern portions of
the Mid-Atlantic and southern New England to support isolated
thunderstorms Thursday afternoon, truly surface-based convection
still appears unlikely. From the Carolinas into the Southeast,
additional storms may occur through the day along/ahead of the cold
front. These areas will remain generally to the south of stronger
forcing for ascent tied to the previously mentioned shortwave trough,
with overall storm coverage expected to remain fairly low.
..Gleason.. 11/25/2020
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228
AM CST Wed Nov 25 2020
Valid 271200Z - 281200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL/COASTAL TEXAS INTO LOUISIANA AND SOUTHWESTERN MISSISSIPPI...
...SUMMARY... Isolated strong to severe thunderstorms may occur
Friday across parts of central/coastal Texas, Louisiana, and
southwestern Mississippi.
...Coastal Texas into Louisiana and Southwestern Mississippi...
Mainly elevated thunderstorms may be ongoing to the north of a warm
front at the beginning of the period across parts of east TX and LA.
This activity should be supported by modest low-level warm advection,
which is forecast to weaken through Friday morning. Still, given
the forecast combination of adequate instability/mid-level lapse
rates with strong deep-layer shear, this convection may continue
to pose an isolated hail threat mainly through the morning hours
across LA and perhaps southwestern MS before diminishing.
As a closed upper low slowly pivots across the Southwest through
the period, a belt of enhanced west-southwesterly mid-level winds
will remain over much of central/coastal TX into parts of the lower
MS Valley. A east-west oriented surface boundary should be located
over these areas, with rich low-level moisture to its south. It
appears that this boundary will serve a focus for potentially robust
convection through the day, possibly beginning by early afternoon
across central TX as small-scale mid-level perturbations embedded in
the westerly flow aloft overspread this region. Weak to potentially
moderate instability along/near the front coupled with strong
deep-layer shear should support some organized convection. Isolated
large hail and strong to locally damaging wind gusts should be the
main threats as storms move slowly south-southeastward in tandem
with the surface front through Friday evening.
..Gleason.. 11/25/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0354 AM CST Wed Nov 25 2020
Valid 281200Z - 031200Z
...DISCUSSION... Medium-range guidance has come into better
agreement regarding the eastward advance of an upper low over the
southern Plains on Day 4/Saturday. Any severe potential Saturday
appears to be confined along/south of a surface boundary which should
be located across parts of coastal/south TX and perhaps southern
LA. Some phasing of this upper low with a northern-stream upper
trough over the Midwest seems probable on Day 5/Sunday. A northward
advance of a partially modified Gulf airmass may occur over parts of
the Southeast Sunday, with an associated isolated/marginal severe
risk. Differences in the evolution of a highly amplified upper
trough/low over the eastern states become apparent in medium-range
guidance by Day 6/Monday. Regardless, a continued isolated/marginal
severe threat may exist Monday across the warm sector of a deepening
surface cyclone from parts of FL and the Southeast along the East
Coast and potentially extending into the Mid-Atlantic. For Day
4/Saturday through Day 6/Monday, too much uncertainty currently
exists regarding inland destabilization to include 15% severe
probabilities for any day.
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0132 AM CST Wed Nov 25 2020
Valid 251200Z - 261200Z
...Synopsis... A mid-level trough will deepen across the
Inter-mountain West as a trough aloft de-amplifies across the
eastern CONUS. The eastward advance of the western upper trough
will induce surface lee-troughing across the southern High Plains
during the day and building surface High Pressure across the Pacific
Northwest and western Great Basin by the end of the period. Dry
and breezy conditions are expected to accompany the lee-troughing
across the southern High Plains, with a surface pressure gradient
becoming established across California, marking the beginning of
a multi-day offshore flow event conducive to wildfire spread.
...Southern High Plains... The latest model guidance consensus
depicts 15-20 mph sustained westerly surface winds and 15-25% RH by
afternoon peak heating along the lee of the southern Rockies towards
the Trans Pecos range. However, these conditions are expected
to be relatively localized in most places given upper ridging and
associated lack of upper support. Guidance consensus does depict a
larger region of Elevated conditions across east-central New Mexico,
where confidence is high enough to maintain an Elevated highlight.
...Portions of southern California... After 06Z Thursday, the
aforementioned pressure gradient is expected to intensify across
portions of southern California, encouraging at least widespread
15-25 mph sustained offshore flow. However, these stronger winds are
expected to arrive in advance of the drier airmass, with surface
RH values in the 25-35% range expected before 12Z (end of the
period). Given the delay of the arrival of drier air, an Elevated
area has been withheld this outlook. Shortly after 12Z, drier air and
even stronger winds are expected to promote considerable wildfire
spread potential. Please see the latest Day 2 Fire Weather Outlook
for more information regarding Thursday's wildfire-spread potential.
..Squitieri.. 11/25/2020
...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
0206 AM CST Wed Nov 25 2020
Valid 261200Z - 271200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...
...Synopsis... A positively tilted mid-level shortwave trough is
expected to dig into the southwest CONUS, with strong northwesterly
flow aloft overspreading parts of southern California during the
Day 2/Thursday period. At the surface, a pressure gradient is
expected to peak in intensity. The strong pressure gradient and
reinforcing upper support will both contribute to very strong/dry
offshore flow across the southern California Transverse Ranges,
promoting considerable wildfire-spread potential. Meanwhile, weak
lee troughing is expected across the southern High Plains prior to
the passage of a cold front, with very modest dry/breezy conditions
accompanying downslope flow along the lee of the southern Rockies.
...Portions of southern California... Between 15-18Z, offshore
surface winds are expected to increase to 25+ mph, with widespread
gusts easily exceeding 40 mph as the surface pressure gradient
strengthens to -3 to -5 mb (LAX to DAG gradient) per latest guidance
consensus. These stronger winds are expected to coincide with 10-20%
RH, atop fuels that are at least modestly receptive to fire spread
(having been devoid of at least two weeks of meaningful precipitation
accumulations). Through Thursday Night/Friday Morning, guidance
consensus depicts a critically strong pressure gradient persisting
to the end of the period, with poor RH recovery expected. As such,
a Critical area has been introduced where confidence is highest in a
high-end Critical event occurring, where stronger winds overlapping
the lower RH and more receptive fuels is expected during the day
through overnight.
...Parts of the southern High Plains... Weak lee-troughing is
expected to persist across the southern High Plains, but with
mediocre upper support. The latest guidance shows regions of
localized 15-20 mph sustained westerly winds overlapping 15-25%
RH across eastern New Mexico into southwest Texas. However, given
the isolated, brief nature of the overlapping favorable surface
winds/RH, fire weather highlights have been withheld this outlook.
..Squitieri.. 11/25/2020
...Please see www.spc.noaa.gov/fire for graphic product...
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"A power so great, it can only be used for Good or Evil!"
-- Firesign Theatre, "The Giant Rat of Summatra"
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