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LU9DCE > ALERT 30.11.20 16:05z 241 Lines 13871 Bytes #999 (0) @ WW
BID : 42056_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 30 11
Path: HB9ON<IW8PGT<IZ3LSV<DB0ERF<DB0RES<ON0AR<GB7CIP<N7HPX<LU9DCE
Sent: 201130/1600Z 42056@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 1150
PM CST Sun Nov 29 2020
Valid 301200Z - 011200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE EASTERN
CAROLINAS INTO SOUTHERN NEW ENGLAND...
...SUMMARY... Isolated strong to severe thunderstorms capable of
producing damaging winds and a couple of tornadoes will be possible
today from parts of Florida into the Carolinas, Mid-Atlantic and
southern New England.
...Synopsis... Remnants of an upper low crossing the southern
Appalachians region early in the period will continue to be absorbed
by a sharp northern-stream trough, progged to be crossing the
upper Great Lakes/Mississippi Valley at the start of the period.
As this trough advances, and fully ingests the remnant upper low,
the trough is expected to gradually close off and become its own
large upper cyclone -- which will reach the central Appalachians
area by the end of the period.
As the upper flow field evolves, a deepening surface low crossing
western North Carolina/Virginia early in the period will move quickly
northward, reaching central New York by 01/00Z where it will then
begin to occlude. The trailing cold front associated with the low
will move across the Atlantic Coast states through the day, likely
clearing the coast from the Mid Atlantic region to Florida through
the evening, while a warm sector lingers onshore over southern New
England into the overnight hours.
...Eastern Carolinas to southern New England... Widespread showers
and embedded thunderstorms are forecast to be ongoing at the start
of the period over the eastern U.S., with the main band of frontal
convection stretching from West Virginia/western Virginia to the
Florida Peninsula early. Limited/local severe potential will be
ongoing, with a gradual, modest increase in threat expected through
late morning/early afternoon from eastern North Carolina northward
into the Mid Atlantic region as at least 500 J/kg mixed-layer
CAPE spreads northward across the coastal Mid-Atlantic/Chesapeake
Bay region.
Very strong flow through a deep layer suggests potential for damaging
winds, where stronger storms can transport momentum downward.
Meanwhile, favorably increasing/veering flow with height through
the lower troposphere will also support potential for low-level
rotation -- and thus a couple of tornadoes appear possible where
sustained supercell storms can evolve.
By mid evening, convection will have largely moved off the Mid
Atlantic Coast, while some severe risk lingers over southern New
England -- possibly into the overnight hours.
...Central Florida... As the cold front shifts southeastward across
Florida through the day, a band of showers and thunderstorms is
likewise forecast to cross the Peninsula. Storms will likely be
ongoing within this frontal band at the start of the period, but
modest CAPE expected ahead of the front suggests that most of the
convection should remain sub-severe. Still, with amply strong
(around 50 kt) mid-level westerly flow atop the frontal zone,
gusty/locally damaging winds may occur with one or two of the
strongest storms, before convection weakens into the afternoon
hours in the wake of the passage of a weak vort max.
..Goss/Moore.. 11/30/2020
SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1157
PM CST Sun Nov 29 2020
Valid 011200Z - 021200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY... Severe thunderstorms are not expected on Tuesday.
...Synopsis... A mature mid-latitude cyclone, with strong flow
throughout its eastern half, is forecast to be centered over the
upper OH Valley early Tuesday morning. This system is expected to
move northward/northeastward throughout the day while continuing
to occlude. Shortwave ridging is anticipated in its wake over the
MS Valley while a pair of cyclones drop southward/southeastward
into the Plains. By early Wednesday morning, the southernmost
cyclone will likely be centered over the TX Panhandle while the
northernmost cyclone will likely be centered over the eastern MT/WY
and the western Dakotas.
Short wavelength between the lead cyclone and pair of cyclones in
its wake will lead to a persistence of the cold, continental air mass
over the central and eastern CONUS. The only exception is across the
TX Coast, where southerly low-level flow will promote moisture return
ahead of an approaching cold front. Enough instability and lift will
be present for isolated lightning flashes. Offshore trajectories
will maintain stable conditions across the western CONUS.
..Mosier.. 11/30/2020
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0152
AM CST Mon Nov 30 2020
Valid 021200Z - 031200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY... Isolated thunderstorms are possible over the Texas
Coastal Plain and southern Louisiana on Wednesday.
...Synopsis and Discussion... A deep upper trough, with two
embedded cyclones, is forecast across the central CONUS early
Wednesday morning. Complex interaction between these cyclones
is anticipated during the day as the southernmost cyclone moves
eastward over OK towards the Ozark Plateau and the northernmost
cyclone moves south-southwestward toward the Four Corners.
Surface low attendant to the southern cyclone will likely begin the
period over TX Red River Valley, but guidance differs on how fast
this low, and its associated cold front, will progress throughout
the day. Low-level moisture return ahead of the front is expected to
bring low 60s dewpoints to the middle/upper TX coast and potentially
southern LA. Uncertainty exists regarding the extent of the moisture
return into LA, largely as a result of differences within the
guidance regarding how fast the surface low progresses eastward. A
slower eastward progression would allow greater moisture return
and higher potential for enough instability to support thunderstorms.
Kinematic profiles support updraft rotation, particularly later in
the period and with eastern extent, if updrafts are able to persist
and deepen. However, abundant cloud cover will curtail heating
and instability, adding to the uncertainty regarding potential
severe thunderstorms. As a result of this low predictability,
severe probabilities will not be added to this outlook, although
probabilities may be needed in later outlooks once the mesoscale
details become more clear.
..Mosier.. 11/30/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0313 AM CST Mon Nov 30 2020
Valid 031200Z - 081200Z
...DISCUSSION... A complex upper pattern is forecast to be in
place across the CONUS early D4/Thursday, with a mature cyclone
likely near the Ozark Plateau and another cyclone to its west over
the Four Corners. Model guidance quickly diverges regarding the
overall pattern evolution, with notable run-to-run variability,
particularly with the deterministic GFS. GEFS also shows very large
standard deviations over the eastern CONUS after D4/Thursday. Even
so, recent runs have trended towards consensus of a Rex block
pattern over the western CONUS by D6/Saturday.
Even with the uncertainty regarding the overall pattern evolution,
severe thunderstorm potential appears to be quite low. Low-level
moisture may advect far enough inland to support modest instability
across the central Gulf Coast on D4/Thursday and Mid-Atlantic Coast
on D5/Friday. However, severe potential is still expected to remain
quite low. Stable conditions are currently anticipated across the
CONUS this weekend.
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
1251 AM CST Mon Nov 30 2020
Valid 301200Z - 011200Z
...Synopsis... Upper-level ridging currently in place over roughly
the western half of the CONUS is expected to gradually weaken and
shift east through the day today as a progressive upper-level trough,
visible in early morning water vapor imagery off the WA/OR coast,
moves into the Pacific Northwest and northern Rockies by tonight and
early Tuesday. Although this wave will mostly bring precipitation
chances to the Northwest, it will also help induce areas of elevated
fire weather conditions for terrain-favored locations of eastern
Wyoming and southern California, where conditions have remained
dry for the past few days.
...Southern California... Early morning surface observations
show a few pockets of ongoing elevated fire weather conditions
for the higher terrain of Los Angeles and Ventura counties in
southern CA. This is largely the result of poor RH recoveries and
continued offshore pressure-gradient winds with gusts between 20-30
mph noted. However, the surface high pressure that has favored this
flow regime over the past few days has begun gradually shifting from
the central Rockies/northern Great Basin into the southern High
Plains, and will continue to do so through the day today. While
elevated conditions will likely continue for the morning hours,
winds may abate slightly during the mid afternoon hours. The passage
of the upper-level trough in the Northwest is forecast to help
re-establish the offshore pressure gradient and increase mid-level
winds late tonight into early Tuesday morning. This may result in the
continuation of elevated fire weather conditions within the higher
terrain of the southern CA coast through at least 12 UTC Tuesday.
...Eastern Wyoming... Modest surface pressure falls have been
noted this morning along the northern High Plains of MT/WY and the
western Dakotas. Lee troughing will likely continue through the day,
as strengthening flow becomes more zonal over northern Rockies and
the Northwestern upper-level trough approaches later in the day. This
will support westerly downslope winds off the front range of eastern
WY, which could support RH reductions into the low 20s, and perhaps
upper teens for a few locations, as winds gust into the 30-40 mph
range (higher for terrain-favored locations). These conditions,
combined with 50-80th percentile ERC values, should support a few
hours of elevated fire weather conditions this afternoon. There is
some uncertainty regarding the eastward extent of these conditions,
so further refinements are possible if guidance comes into better
agreement.
...Southern Arizona... Breezy easterly winds combined with RH values
in the low 20s and teens may support pockets of elevated fire weather
conditions for a couple of hours early this afternoon. Most guidance
continues to suggest that pressure-gradient driven winds will
diminish by the late afternoon hours during peak heating. As such,
no highlights are introduced for this outlook, though conditions
will continue to be monitored.
..Moore.. 11/30/2020
...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
0219 AM CST Mon Nov 30 2020
Valid 011200Z - 021200Z
...Synopsis... A deepening upper-level trough over the central
CONUS will bring windy and cool conditions to the Plains as well as
reinforce surface high pressure over the northern Great Basin for
Tuesday. The cooler air will mitigate the fire weather potential
over the drier locations in the Plains, but the building surface
high may strengthen offshore flow for the southern California coast.
...Southern California... The surface high over the Pacific
Northwest/northern Great Basin is forecast to gradually strengthen
through the day Tuesday and into early Wednesday. Most guidance
is in fairly good agreement that this will augment the pressure
gradient across southern CA. With no precipitation forecast
and poor moisture return and RH recovery, elevated fire weather
conditions will likely persist in higher elevations from Tuesday
morning through Wednesday morning. There are some indications that
the DAG-LAX pressure gradient may reach a maximum around 12 UTC
Wednesday, but it remains unclear whether or not the corresponding
increase in pressure-gradient winds will be sufficient for widespread
critical conditions. However, at least a few pockets of sustained 20+
mph winds appear possible by early Wednesday morning - especially
for northern Los Angeles and Ventura counties where ensemble and
deterministic guidance show the strongest potential for isolated
critical conditions.
...Southern High Plains... Westerly downslope winds are forecast to
increase across eastern NM ahead of a southward surging cold front
Tuesday afternoon. Some model solutions suggest that downslope
warming and drying may be sufficient for areas of elevated fire
weather conditions. However, scattered precipitation and relatively
cool temperatures over the past few days will likely yield modestly
receptive fuels by Tuesday afternoon. This factor, combined with
the potential for a faster southward progression of the colder air,
preclude the addition of a risk area for this outlook. An elevated
highlight may be introduced in later outlooks if fuels can become
adequately dry and confidence in the timing of the front increases.
..Moore.. 11/30/2020
...Please see www.spc.noaa.gov/fire for graphic product...
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Scrubbing floors and emptying bedpans has as much dignity as the Presidency.
-- Richard Nixon
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