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LU9DCE > ALERT 23.12.20 17:33z 200 Lines 11369 Bytes #999 (0) @ WW
BID : 306_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 23 12
Path: HB9ON<IW2OHX<IQ2LB<IR2UFV<IZ5FSA<IK5FKA<LU9HGS<LU3DVN<LU9DCE
Sent: 201223/1701Z 306@LU9DCE.TOR.BA.ARG.SOAM LinBPQ6.0.21
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
LU9DCE@GMX.COM
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SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252
AM CST Wed Dec 23 2020
Valid 241200Z - 251200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS FAR EASTERN
SC...EASTERN NC...AND FAR SOUTHEAST VA...
...SUMMARY... Severe thunderstorms are expected across the
Mid-Atlantic States Thursday afternoon and evening. Isolated severe
thunderstorms are also possible across portions of southeast Alabama,
southwest Georgia, and Florida Thursday.
...Synopsis... A deep upper trough will extend from western
Ontario southwestward through TX early Thursday morning. A shortwave
trough embedded within the larger upper trough is expected to eject
eastward across the Lower MS Valley before arcing more northeastward
into the TN Valley. Evolution of the embedded shortwave will help
induce a neutral tilt to the upper trough by Thursday afternoon,
and a slightly negative tilt and closed upper circulation over the
OH Valley by late Thursday night/early Friday morning.
The maturing process of the upper trough will also result in further
strengthening of the winds throughout its periphery. By early Friday
morning, 100+ kt 500-mb winds will likely extend from the mid MS
Valley southeastward/eastward through the base of the trough over
the Southeast and then back northeastward into the Northeast. Very
intense low-level flow is also expected, with 60+ kt at 850-mb
extending from the Carolinas through the Mid-Atlantic into Quebec.
Surface low associated with the embedded shortwave trough is forecast
to begin the period over central AL before racing northeastward
throughout the day. By early Friday morning, this low will likely
be over western NY. This low is also expected to deepen during the
period, helping to induce moisture return across the Mid-Atlantic.
...Mid-Atlantic States... Moisture return ahead of surface low and
its attendant cold front is expected to net low 60s dewpoints across
the Carolinas and southeast VA by the late afternoon/evening. Heating
will be tempered by widespread cloud cover and lapse rates will
remain modest. However, the anticipated moisture return should
still be sufficient for modest instability by the afternoon. At
the same time, very impressive kinematic profiles will be in place
over the warm sector, with 50-70 kt 850+ mb flow contributing
to large, looping low-level hodographs. 0-1 km storm-relative
helicity will likely exceed 250 m2/s2 over the warm sector. Any
discrete/semi-discrete storms that develop within this environment
should become supercellular and pose a threat for tornadoes. However,
several factors are difficult to ascertain at this forecast range,
including the speed of the cold front, quality of the moisture
return, and coverage of surface-based, warm-sector storms. These
factors preclude introducing higher tornado probabilities with this
outlook, but upgrades may be needed in subsequent outlooks.
Additional severe potential will exist along the front as it moves
through the region. Both damaging wind gusts and QLCS tornadoes are
possible along the front as it moves through the region. Higher
wind probabilities may also be needed in later outlooks once the
amount of buoyancy ahead of the front become more certain.
...Portions of GA and FL... Modest severe potential is anticipated
early Thursday along and ahead of the front as it moves across the
FL Panhandle and southeast AL/southwest GA. In this region, modest
instability and strong flow will likely support a few strong/severe
storms. Similar environmental conditions, but with less low-level
shear, could also contribute to a few strong/severe storms across
the FL Peninsula as the front moves through.
..Mosier.. 12/23/2020
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0214
AM CST Wed Dec 23 2020
Valid 251200Z - 261200Z
...NO THUNDERSTORM AREAS FORECAST...
...SUMMARY... Thunderstorms are not expected on Friday.
...Synopsis... A deep upper trough, with an embedded closed
circulation over the middle OH Valley, will cover the eastern CONUS
early Friday morning. Very strong flow aloft will surround this
system as it gradually moves eastward throughout the day. An
associated surface low will begin the period over eastern
Ontario/southern Quebec. A cold front will extend southeastward
from this low to just off the southern New England coast before
arcing more southward. With the front already offshore by early
Friday morning and stable conditions in its wake, no thunderstorms
are expected across the central and eastern CONUS.
Farther west, upper ridging initially in place over the western CONUS
will gradually progress eastward as a shortwave trough approaches the
Pacific Northwest. Strong forcing for ascent and cold temperatures
aloft will accompany this shortwave, and a lightning flash or
two may occur in the deeper convection within the frontal band
offshore. However, any lightning is not expected to continue once
the band moves onshore.
..Mosier.. 12/23/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0330 AM CST Wed Dec 23 2020
Valid 261200Z - 311200Z
...DISCUSSION... A relatively active upper pattern is anticipated
from this weekend through the middle of next week. A shortwave
trough will likely progress through southern Plains on D5/Saturday,
with another shortwave in its wake over the central/southern Plains
on D6/Sunday. Dry and stable conditions ahead of these shortwaves
will keep severe potential very low.
A third, potentially stronger system is expected to move from
central/southern CA eastward across the Four Corners region and
into the central/southern Plains early next week. Medium-range
guidance has varying solutions for the evolution of this system,
but some severe potential appears possible if enough moisture return
occurs ahead of it.
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0150 AM CST Wed Dec 23 2020
Valid 231200Z - 241200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...
...Synopsis... A highly amplified upper trough will move eastward
across the central CONUS today, eventually reaching the MS Valley
late tonight. Surface high pressure will remain over the Great Basin
beneath an upper ridge. Farther east, a cold front will move quickly
southeastward across the southern/central Plains through the day.
...Southern California and the Lower Colorado River Valley...
The surface pressure gradient across southern CA is expected
to continue strengthening this morning, and this gradient should
remain fairly strong through much of the period. Consensus of latest
guidance continues to suggest the LAX-TPH pressure difference should
reach -12 to perhaps -13 mb by the afternoon. This will support
critically strong offshore flow across much of coastal southern CA,
with sustained east-northeasterly winds of 20-35 mph likely in the
mountains/foothills. Stronger gusts up to 45-60 mph may also occur
in the higher terrain and favored passes. RH values will quickly
lower into the 5-15% range through the day as both diurnal heating
and low-level downslope warming/drying occur. Critical conditions
should continue this evening/tonight into early Thursday morning, as
poor overnight RH recovery occurs and the surface pressure gradient
remains strong. Fuels remain very receptive for large fire spread
across much of this region, and the ongoing critical delineation
has been maintained with only minor changes.
Across the lower CO River Valley, elevated conditions are expected
today, as northerly winds of 15-25 mph combine with lowered RH
values and at least marginally receptive fuels.
...Southern Plains... Strong/gusty north-northwesterly
winds of 15-30 mph are expected to occur mainly behind the
southeastward-moving cold front this afternoon. Although low-level
cold advection will occur behind the front, surface temperatures
should still reach into mid 40s to perhaps low 60s across parts of
the southern Plains with diurnal heating. Lowered RH values ranging
from around 15% across the High Plains to 25-30% across parts of
central/east TX and OK will combine with the strong/gusty winds and
at least marginally receptive fuels to promote widespread elevated
conditions this afternoon.
..Gleason.. 12/23/2020
...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
0154 AM CST Wed Dec 23 2020
Valid 241200Z - 251200Z
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA...
...Synopsis... A large-scale upper trough over the central CONUS
should evolve into a closed low as it moves slowly towards the
eastern states through the period. A surface cold front will likely
have cleared coastal TX by early Thursday morning. An upper ridge
is forecast to build over much of the western CONUS, as a shortwave
trough moves across southern/central CA and parts of the Southwest
Thursday evening/night. A strong surface high will remain centered
over the Great Basin Thursday morning, before slowly weakening
through the day.
...Southern California... A modestly enhanced surface pressure
gradient should support continued strong/gusty winds of 20-25 mph
Thursday morning, mainly across the mountains/foothills of coastal
southern CA. Higher gusts will be possible as well. This pressure
gradient should gradually relax by midday, with a corresponding
decrease in wind speeds expected. RH should remain lowered owing to
poor overnight recovery and continued mixing of the boundary layer,
with widespread RH values of 10-15% likely. Have included a critical
delineation for Thursday morning across the same areas of southern
CA as Day 1/Wednesday, as critical conditions appear likely to
persist for at least the first few hours of the Day 2 period.
...Southern Plains... Strong/gusty northwesterly winds will likely
develop across parts of the southern Plains on Thursday, as enhanced
flow at mid levels on the back side of the upper trough/low reaches
the surface through diurnal mixing of the boundary layer. Sustained
winds of 15-25 mph appear probable, with higher gusts possible. Even
though surface temperatures should remain rather cool behind a
prior frontal passage, RH values should lower enough (to around
15-25%) to support widespread elevated conditions for a few hours
Thursday afternoon from parts of the TX Panhandle into southern OK
and central/east TX. The occurrence of critical conditions appears
too limited in both space and time to include a critical area.
..Gleason.. 12/23/2020
...Please see www.spc.noaa.gov/fire for graphic product...
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Sorry. I just realized this sentance makes no sense :)
-- Ian Main
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