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LU9DCE > ALERT 06.12.20 16:01z 178 Lines 9638 Bytes #999 (0) @ WW
BID : 42491_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 06 12
Path: HB9ON<IW8PGT<IZ3LSV<IK5FKA<IK5FKA<LU9HGS<LU9DCE
Sent: 201206/1600Z 42491@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 1146
PM CST Sat Dec 05 2020
Valid 061200Z - 071200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE FLORIDA
KEYS AND EVERGLADES...
...SUMMARY... A few strong to locally severe storms may occur
across the Florida Keys and Everglades tonight.
...FL Keys and Everglades... A mid-level trough, initially near
the TX coast this morning, will move east into the northeast Gulf
of Mexico by early Monday morning. A belt of stronger mid-level
flow will overspread the eastern Gulf of Mexico after dark as a
minor mid-level disturbance embedded within this flow approaches the
Keys by late Sunday night. Southerly low-level flow is forecast to
strengthen coincident with this impulse arriving during the 06z-12z
period. A cluster of showers and thunderstorms is forecast to move
west to east across the Keys and the Everglades. Although lapse
rates will remain modest, enlarging hodographs will conditionally
support a risk for a few of the stronger thunderstorms to exhibit
transient rotation and perhaps a marginal wind/tornado threat.
Elsewhere across the Lower 48 states, conditions will be hostile
for thunderstorms.
..Smith/Lyons.. 12/06/2020
SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1147
PM CST Sat Dec 05 2020
Valid 071200Z - 081200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY... Isolated thunderstorms are expected across the far
southern Florida peninsula and Keys Monday morning.
...Southern FL and the Keys...
The base of an upper trough over the eastern U.S. will pivot
northeast on Monday, moving across the eastern Gulf Coast vicinity,
and eventually offshore from the Atlantic coast Monday night. A
weak surface low is forecast to be located near the FL Keys at the
beginning of the period, with a cold front extending across southern
FL. Showers and thunderstorms will likely be ongoing near the Keys
and far south/southeastern peninsula. A narrow corridor of mid/upper
60s F dewpoints and a couple hundred J/kg SBCAPE may overlap with
sufficient low level shear to foster a couple of strong storms.
However, forecast guidance varies, with faster solutions showing
strong storms south and east of the Keys and the southern Peninsula
by 12-13z while slower solutions bring a band of convection through
by 15-16z. Thunderstorm activity will quickly diminish toward midday
as the front pushes offshore. Uncertainty in short-duration severe
potential in the first 2-3 hours of the forecast period will preclude
Marginal risk probabilities at this time. However, if confidence
increases in a slower eastward progression of thunderstorms,
low-end wind and possibly tornado probabilities may be necessary
in later outlooks.
..Leitman.. 12/06/2020
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0115
AM CST Sun Dec 06 2020
Valid 081200Z - 091200Z
...NO THUNDERSTORM AREAS FORECAST...
...SUMMARY... Thunderstorms are not expected on Tuesday.
...Synopsis...
An upper trough over the eastern U.S. will continue to shift eastward
over the Atlantic while upper ridging spreads across much of the rest
of the CONUS. A cutoff low also will persist offshore from southern
CA/northern Baja. At the surface, high pressure will encompass
much of the country, and a cold front will push southward into the
southern Gulf of Mexico. This will result in dry, stable conditions
and thunderstorms are not expected across the CONUS on Tuesday.
..Leitman.. 12/06/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0253 AM CST Sun Dec 06 2020
Valid 091200Z - 141200Z
...DISCUSSION... An upper ridge will spread eastward across the
Plains toward the MS River on Day 4/Wed as a shortwave trough digs
south and east across the Pacific Northwest and northern Rockies. At
the same time, the persistent cut-off upper low off the southern
CA/northern Baja coast will develop eastward along the international
border. This will bring increasing chances for rain and perhaps a
few thunderstorms to portions of the southwestern U.S. Wednesday
and Thursday.
By Day 5/Thu, the northern Rockies trough and the southwestern upper
low will merge into a larger-scale trough, and eject eastward from
the Rockies into the Plains by early Day 6/Fri. In response, lee
cyclogenesis is forecast over the southern/central Plains. Strong
southwesterly deep layer flow will overspread the southern Plains
into the mid MS Valley late Thursday, and southerly Gulf return flow
will develop across the south-central U.S. As this system shifts
eastward through Day 6/Fri and Day 7/Sat, thunderstorm potential
will increase across portions of the southern Plains into the lower
MS Valley, and perhaps as far north as the mid-MS/lower OH Valleys.
However, severe potential is uncertain. The quality of low level
moisture return could be limited to a small portion of the Sabine
and lower MS Valleys, and may be ill-timed with the passage of the
upper trough and surface cold front. Additionally, medium range
guidance varies in the intensity of the developing surface cyclone,
and in timing of the eastward-advancing cold front from the Plains
into the Midwest. As such, predictability is too low to include
any severe probabilities.
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0143 AM CST Sun Dec 06 2020
Valid 061200Z - 071200Z
...Synopsis... Blocking high pressure will remain in place across
the western US as an upper low is forced southward into northern
California. Dry and warm conditions will support elevated fire
weather potential across southern California as a Santa Ana wind
event is forecast to begin late in the period.
...Southern California... The offshore pressure gradient that has
plagued the area over the past several days will reach a minimum in
intensity Day1/Sunday afternoon, as surface high pressure strengthens
over the region. Winds will remain weak, and primarily terrain
driven through the morning and afternoon hours. Abundant dry air
will keep humidity values low (10-15%), supporting some local
elevated fire weather conditions.
The offshore pressure gradient is forecast to slowly re-intensify
overnight Day1/Sunday and early Day2/Monday ahead of the southward
moving upper low. Regional cross sections show the pressure
gradient reaching 6 to 8 mb by 4 am PST. This should result in gusty
Santa Ana winds developing across the higher terrain of southern
California. Humidity recoveries will be enhanced ahead of the upper
low, as mid-level moisture and cloud cover enter from the north.
Regardless, the increasingly gusty 20-30 mph winds and humidity
in the 20-30% range should support elevated to near critical fire
weather potential late in the forecast period.
..Lyons.. 12/06/2020
...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
0146 AM CST Sun Dec 06 2020
Valid 071200Z - 081200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...
...Synopsis... An intensifying upper ridge and surface high pressure
across the Great Basin will interact with an upper low near the
coast of California leading to strong offshore flow through the
forecast period. Very strong and dry downslope winds will increase
fire weather concerns across portions of southern California.
...Southern California... A Santa Ana wind event is forecast to
start late in the Day1/Sunday forecast period and carry over through
Day2/Monday. Offshore winds will intensify through the afternoon
and into the overnight hours, as the southward moving upper low
drifts along the coast. Humidity values will remain somewhat elevated
(20-25%) through much of Monday, as cooler temperatures and mid-level
moisture are advected in from the upper low. Despite the slightly
higher RH, widespread elevated and critical fire weather conditions
are forecast to develop across much of southern California by Noon
PST Monday.
RH will begin to drop (7-15%) overnight Day2/Monday, as the Santa
Ana winds continue to intensify. Moderate easterly mid-level flow
will overspread the robust offshore pressure gradient supporting
winds of 30-40 mph (gusts to 70+ mph) in the mountains and canyons.
The strong winds and drier air from the downslope flow will create
dangerous fire weather conditions across the higher terrain of
southern California overnight and into early Day3/Tuesday. There
is some potential for localized extremely critical conditions to
develop where humidity values are able to drop into the single
digits. However, the lack of model consensus on widespread very
low humidity values precludes the addition of an extremely critical
area at this time.
..Lyons.. 12/06/2020
...Please see www.spc.noaa.gov/fire for graphic product...
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