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LU9DCE > ALERT 29.11.20 16:13z 257 Lines 14859 Bytes #999 (0) @ WW
BID : 41990_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 29 11
Path: HB9ON<IW2OHX<IQ2LB<IQ5KG<IZ3LSV<IW8PGT<LU4ECL<VK2RZ<W0ARP<KF5JRV<
N7HPX<LU9DCE
Sent: 201129/1600Z 41990@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 1200
AM CST Sun Nov 29 2020
Valid 291200Z - 301200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
AND EASTERN GULF COAST REGION...AND THE SOUTHEASTERN U.S. ATLANTIC
COAST...
...SUMMARY... Isolated strong to severe thunderstorms remain
possible today and tonight across southern portions of the Gulf
Coast states into the eastern Carolinas. A couple of tornadoes,
and a few locally damaging wind gusts, are the main threats.
...Synopsis... An upper low initially over Oklahoma is forecast
to move eastward to the mid/lower Mississippi Valley through the
first half of the period, but will gradually become absorbed by
a northern-stream trough digging east-southeastward out of the
northern Plains/upper Mississippi Valley into the Midwest/middle
Mississippi Valley overnight.
At the surface, a weak low is forecast to move across the northern
Gulf of Mexico near the Louisiana coast toward Mobile Bay during
the day, along a pre-existing baroclinic zone. Thereafter, the
low is progged to turn northeastward and move quickly northward
along the Appalachians, deepening rapidly as it reaches the West
Virginia vicinity by the end of the period/Monday morning.
...Central and eastern Gulf Coast/southeastern Atlantic coast...
Widespread precipitation is forecast to be ongoing at the start
of the period ahead of the advancing upper low, from southern and
eastern Texas across Arkansas and Louisiana into southern Mississippi
and vicinity. The substantial precipitation and cloud cover --
that should persist through the day -- over the central Gulf
Coast states/mid South should maintain a stable boundary layer.
Any potential for surface-based convection appears likely to
remain confined to southeast Louisiana, southeast Mississippi,
and into southern Alabama and the Florida Panhandle through the
daylight hours. A separate area of storms may evolve during the
afternoon across eastern South Carolina and into the southern
Atlantic, near a developing warm front.
During the evening and overnight, as the surface low deepens/shifts
rapidly north-northeastward, surface-based convection will spread
eastward across southeastern Alabama and roughly the southern half
of Georgia, and northern portions of the Florida Peninsula ahead of
the strengthening cold front. Meanwhile, surface-based convection
will shift northward across the eastern Carolinas and eventually
into southeastern Virginia, east of the surface low as the warm
front shifts northward.
Instability is forecast to remain quite limited inland, with
generally less than 300 to 500 J/kg mixed-layer CAPE expected.
However, increasingly strong and veering flow with height will
evolve with time, in tandem with surface cyclogenesis, yielding
shear profiles sufficient for supercells. While modest CAPE
should remain a limiting factor, a couple of tornadoes will be
possible, within a broad SLGT risk area from southern Mississippi
east to northern Florida, and north across the eastern Carolinas
to southeast Virginia. A few stronger storms may also produce
gusty/locally damaging winds, particularly if small bowing segments
can evolve locally. Risk will taper off from west to east along
the Gulf Coast through the evening, but may linger through the end
of the period across portions of Florida, and particularly along
the Atlantic Coastal portion of the outlook.
..Goss/Moore.. 11/29/2020
SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1210
AM CST Sun Nov 29 2020
Valid 301200Z - 011200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS FAR
SOUTHEAST VA AND COASTAL NC...
...SUMMARY... Isolated strong to severe thunderstorms capable of
producing damaging winds and perhaps a couple of tornadoes appear
possible on Monday from parts of Florida and coastal Georgia into
the Carolinas and Mid-Atlantic.
...Synopsis... A deep upper trough is forecast to extend from
eastern Ontario into the Lower MS Valley early Monday morning. An
embedded shortwave trough will likely be centered over the
southern Appalachians, with another shortwave trough in its wake
centered over the Ozark Plateau. Quick northeastward progression
is anticipated by the lead wave with the Ozarks shortwave digging
southward and then eastward across the Southeast. This pattern
evolution will be accompanied by strengthening low to mid-level flow
and cyclogenesis. By the end of the period, a mature mid-latitude
cyclone will likely be centered over the central Appalachians, with
strong, deep-layer flow extending throughout its eastern periphery
along the East Coast.
Surface low associated with this cyclone is forecast to begin to
the period over the central Appalachians with a cold front extending
southward/south-southwestward to the FL Big Bend. This surface low
is then expected to move north-northeastward and become increasingly
occluded throughout the day. At the same time, the attendant cold
front will sweep eastward off the East Coast.
...Much of the East Coast... Dewpoints in the low 60s will
likely extend as far north as the VA Tidewater region early Monday
morning. Mid to upper 60s dewpoints are expected to be in place
farther south across southeast GA and most of FL, with mid 50s
dewpoints extending up into the Delmarva. The overall environment
ahead of the cold front will be characterized by abundant cloud
cover, moist profiles and poor mid-level lapse rates. Even so,
the modest low-level moisture is expected to result in limited
instability and the potential for a few deeper updrafts capable
of either damaging wind gusts and/or brief tornadoes. This
potential severe threat will exist along the length of the
front, from the Mid-Atlantic into FL, but the threat appears
to be maximized over coastal NC Monday morning. In that area,
southerly/south-southeasterly surface winds beneath strong
(i.e. 50-55 kt) 850-mb winds will result in low-level kinematic
profiles very supportive of rotation. Previously mentioned limited
instability will result in predominantly transient updrafts,
particularly ahead of the front in warm sector, with limited depth
and persistence. However, any deeper, more persistent updrafts may
be able to produce damaging wind gusts and/or a tornado or two.
Farther north (from the Delmarva into coastal southern New England),
the primary severe threat will be later into the afternoon as the
triple point moves across the region. Low probability potential
exists for the development of a narrow and shallow line of convective
along the cold front extending southward from the triple point. Even
less instability is anticipated here than farther south and any
convection will likely become elevated above a low-level stable
layer, but the very strong wind fields suggest than even a shallow,
elevated storm may be able to produce a strong gust at the surface.
..Mosier.. 11/29/2020
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0137
AM 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 aloft
throughout its eastern half, is forecast to be centered over the
Upper OH Valley early Tuesday morning. This cyclone will likely move
northeastward into the Lower Great Lakes region while occluding. As
it does, shortwave ridging will move eastward into the MS Valley
and another cyclone will develop over the Plains. This upper pattern
progression will reinforce the stable continental air mass already
in place, limiting low-level moisture and precluding the instability
needed for deep moist convection and lightning production.
The only lightning potential during the period appears to be early
Wednesday morning along the TX Coast as low-level moisture returns
ahead of an approaching cold front. In this area, broad warm-air
advection amid weak instability may result in a few lightning
flashes.
..Mosier.. 11/29/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0303 AM CST Sun Nov 29 2020
Valid 021200Z - 071200Z
...DISCUSSION... Medium-range guidance is in good agreement that a
pair of cyclones, one centered over the central Plains and the other
centered over southwest Quebec, will be in place over North America
D4/Wednesday morning. The current expectation is Quebec cyclone to
eject northeastward D4/Wednesday and D5/Thursday while the Plains
cyclone gradually drifts southward/southeastward. After D5/Thursday,
the Plains cyclone is expected to become more progressive, moving
eastward across the TN Valley/Southeast from D6/Friday through
D7/Saturday. However, deterministic and ensemble guidance shows
significant spread in the speed and location of this cyclone as
it ejects eastward. Some severe potential could result over the
Southeast/FL if the moisture return ahead of the cyclone is robust
enough. However, predictability is currently too low for much
forecast confidence past D5/Thursday.
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
1240 AM CST Sun Nov 29 2020
Valid 291200Z - 301200Z
...Synopsis... The upper-level flow regime is expected to amplify
through the day today, featuring a deepening trough across the
eastern third of the US and continued upper-level ridging over
much of the West. A surge of colder air and a strengthening surface
high are expected across the Plains that will bring gusty winds and
perhaps brief fire weather concerns for a few locations. Persistent
offshore flow over southwest California will continue to support
elevated fire weather conditions.
...Southern California... Areas of elevated fire weather conditions
are expected to continue for today within the higher elevations
of southern CA. Early morning surface observations show pockets
of elevated conditions ongoing across the Santa Susana and western
San Gabriel mountains. This is mainly due to the maintenance of an
offshore pressure gradient that is associated with a surface high
over the north/northeastern Great Basin that is forecast to largely
remain in place for most of today. Poor overnight RH recoveries
and little to no moisture return will support another day of RH
values in the low teens and single digits. However, weak mid and
upper-level winds will continue to limit the potential for elevated
and/or brief critical conditions to just terrain-favored locations
where winds may locally be stronger.
...Western Kansas... Winds are expected to increase behind a
southward surging cold front later this afternoon across the
Plains. Strong low-level cold advection will aid in mixing down
30-40 mph 850 mb winds to the surface across a broad swath of
KS, OK, and the OK/TX Panhandles. Despite this, most guidance
suggests that the cooler air will limit RH reductions for most of
the region. A few locations across western KS may see periodic RH
reductions to near 20% due to slightly drier air on the western
periphery of the polar air mass. This idea is supported somewhat
by upstream post-frontal observations that show dewpoints in the
teens across the northern High Plains (versus 20-30 F dewpoints
to the east). However, given little support by most guidance,
confidence in the coverage and duration of elevated fire weather
conditions remains low and precludes the addition of a risk area.
..Moore.. 11/29/2020
...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
0142 AM CST Sun Nov 29 2020
Valid 301200Z - 011200Z
...Synopsis... A dominant surface high over the central CONUS
will gradually shift south through the day Monday. This will
have the affect of bringing calmer and cool conditions to much
of the Plains as well as help weaken the pressure gradient over
the Southwest. Fire weather concerns will largely be limited to
locations that typically experience terrain-augmented winds across
parts of southern California and possibly along the foothills of
eastern Wyoming.
...Southern California... The gradual shift of the surface high
from the central Rockies/northern Great Basin into the southern High
Plains will help alleviate the offshore pressure gradient across
southern California to a degree. Despite an improving synoptic
pattern, mid-level winds are forecast to strengthen as a progressive
upper-level trough glances the region to the north. Afternoon
boundary-layer mixing will likely support 15-25 mph winds down to
the surface within the higher elevations, which, when coupled with
antecedent low RH values and dry conditions, will foster areas of
elevated fire weather conditions through Monday afternoon. Surface
high pressure is forecast to become re-established over the northern
Great Basin by late Monday/early Tuesday in the wake of Monday's
upper-level trough passage. This may result in a re-intensification
of the offshore pressure gradient and allow for pockets of elevated
fire weather conditions to linger into early Tuesday.
...Eastern Wyoming... The same upper-level shortwave trough that
will bring an uptick in mid-level winds to the Southwest will also
help drive lee troughing along the northern High Plains Monday
afternoon. This troughing, combined with increasing 850-700 mb
westerly flow, will help drive areas of gusty west/southwesterly
winds. Downslope warming and drying may allow a few locations to see
elevated fire weather conditions, but this is expected to largely be
confined to the immediate leeward side of elevation features. Recent
ensemble guidance suggests that the most likely location for this
to occur is across the foothills of eastern WY where ERC values
are slightly elevated, but a lack of support from deterministic RH
solutions and only modestly receptive fuels yields low confidence
in the fire weather potential at this time. As such, no highlights
are introduced, but trends will continue to be monitored.
..Moore.. 11/29/2020
...Please see www.spc.noaa.gov/fire for graphic product...
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