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LU9DCE > ALERT 30.12.20 17:36z 245 Lines 13712 Bytes #999 (0) @ WW
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Subj: STORM PREDICTION CENTER 30 12
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Sent: 201230/1700Z 784@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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MD 1889 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF
NORTHERN IL...FAR SOUTHEASTERN WI...FAR NORTHERN IN...AND SOUTHERN
LOWER MI
Mesoscale Discussion 1889 NWS Storm Prediction Center Norman OK
0115 AM CST Wed Dec 30 2020
Areas affected...Portions of northern IL...far southeastern WI...far
northern IN...and southern Lower MI
Concerning...Winter mixed precipitation
Valid 300715Z - 301315Z
SUMMARY...A mix of freezing rain, sleet, and snow will move west
to east this morning while gradually transitioning to all rain.
Freezing rain rates may exceed 0.05 inch per 3 hours across parts
of southern Lower Michigan.
DISCUSSION...Ahead of a positively tilted mid/upper-level trough,
strong ascent associated with a 50-60+ kt southwesterly low-level
jet is supporting a broad swath of precipitation across the Midwest
early this morning. Multiple sites across northern IL and vicinity
are reporting freezing rain as the predominant precipitation type,
with some locations recording ice accretion in excess of 0.05 inch
in 3 hours. Current expectations are for this moderate to heavy
precipitation plume to spread eastward into far northern IN and
southern Lower MI over the next several hours this morning in tandem
with the eastward evolving low-level jet. As the low-level thermal
profiles continue to warm with strong low-level warm advection
occurring, a transition from snow/sleet to freezing rain and
eventually plain rain will occur from southwest to northeast across
this region as surface temperatures eventually rise above freezing.
Parts of southern Lower MI should be slower to have this transition
occur given current surface temperatures in the mid to upper 20s,
with greater potential for freezing rain rates to exceed 0.05 inch
per 3 hours.
..Gleason.. 12/30/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DTX...IWX...GRR...LOT...MKX...
LAT...LON 43418453 43458324 43298280 43008281 42618318 42218376
41858451 41498740 41438825 41578908 41938942 42378930 42688885
43128729 43418453
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127
PM CST Tue Dec 29 2020
Valid 301200Z - 311200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE LOWER AND MIDDLE TEXAS COASTAL PLAIN VICINITY THIS AFTERNOON
INTO TONIGHT...
...SUMMARY... Thunderstorms -- and limited severe potential --
will affect portions of the Texas Coastal Plain and Hill Country
this afternoon into the overnight hours.
...Synopsis...
A progressive but split flow regime is in place over the CONUS
today. An upper shortwave trough over the Upper Midwest will shift
eastward across the Great Lakes to the Northeast. Meanwhile, in the
southern stream, an upper shortwave trough over northwest Mexico and
the southern Rockies will develop an upper low over northern Mexico,
and pivot eastward toward the Rio Grande in TX by Thursday morning.
Another shortwave trough will move over the Pacific Northwest
overnight, and could bring isolated thunderstorms to the WA/OR coast.
...Middle and Lower TX Coastal Plain vicinity...
A southeastward-advancing cold front will extend from northwest
AR into southeast OK and towards the Edwards Plateau of TX. Low
level southerly flow will continue to transport Gulf moisture
northward ahead of the front. Instability will be limited however,
due to ongoing showers and thunderstorms and general cloudiness
precluding stronger insolation ahead of the front. Additionally,
a warm layer is evident around 700 mb in most forecast guidance
and point forecast soundings. This warm layer is also evident
in 00z RAOBs. While cooling aloft will occur, it likely will be
ill-timed with frontal passage. As a result, this should act to limit
updraft intensity. Nevertheless, strong shear will be in place, an
a couple of storms capable of marginally severe hail are possible
across parts of the Edwards Plateau to the middle and lower TX coast.
During the evening and overnight hours, a surface low will develop
east/northeast along the lower and middle TX coast. As this occurs,
low level winds will become more southeasterly, resulting in
favorably curved low-level hodographs supporting rotating storms.
This threat should remain confined closer to the coast and just
ahead of the cold front. While instability will remain limited,
favorable low-level and bulk shear could result in a couple of
storms capable of producing a tornado or locally damaging wind gusts.
..Leitman.. 12/30/2020
SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1238
AM CST Wed Dec 30 2020
Valid 311200Z - 011200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
FAR SOUTHEAST TEXAS...THE LOWER MISSISSIPPI VALLEY AND CENTRAL GULF
COAST STATES...
...SUMMARY... Severe thunderstorms associated with a tornado threat
and wind damage will be possible Thursday into Thursday night from
far southeast Texas into the lower Mississippi Valley and across
the central Gulf Coast States.
...Far Southeast Texas/Lower Mississippi Valley/Central Gulf Coast
States... An upper-level low will move from northern Mexico into
central Texas on Thursday. The associated upper-level trough will
become negatively-tilted as a 70 to 90 kt mid-level jet rounds
the base of the system. During the day, the moist sector will
extend from the far southeast Texas eastward across Louisiana,
southern Mississippi and southern Alabama. A surface low will
move north-northeastward across the far western edge of the moist
sector. Near the surface low, a large cluster of thunderstorms
will be ongoing in the Texas Coastal Plain at the start of the
period. This convection will be supported by large-scale ascent
associated with the nose of the mid-level jet. The cluster of storms
will move east-northeastward to the upper Texas Coast by afternoon
and into the lower Mississippi Valley by early evening.
Ahead of the cluster of storms, model forecasts increase MLCAPE
into the 500 to 1000 J/kg range over much of the moist sector. In
spite of the weak instability, the mid-level jet will create
strong deep-layer shear profiles, which will be favorable for
severe storms. A severe threat is forecast to first develop in far
southeast Texas early Thursday afternoon as a 50 to 60 kt low-level
jet moves inland across southwestern Louisiana. The severe threat
should be the greatest along and ahead of a pre-frontal trough,
which will progress eastward across southern Louisiana during the
late afternoon and early evening. At that time, low-level shear
is forecast to become maximized due to the presence of the 850
mb jet. The jet will create 0-3 km storm relative helicities
of 300 to 400 m2/s2, which will support a tornado threat with
the more dominant rotating storms. The tornado threat may become
maximized in southeastern Louisiana during the late afternoon and
early evening, near a pocket of moderate instability. Wind damage
will also be possible with the stronger thunderstorms embedded
in the cluster. The severe threat is expected to continue across
southern Mississippi and southern Alabama during the mid to late
evening. The threat may persist into the early overnight period,
especially if a line of strong thunderstorms can persist.
..Broyles.. 12/30/2020
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0154
AM CST Wed Dec 30 2020
Valid 011200Z - 021200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS
OF THE SOUTHEAST AND CAROLINAS...
...SUMMARY... Thunderstorms associated with marginally severe wind
gusts will be possible on Friday into Friday night from northern
Florida to southern North Carolina.
...Southeast/Carolinas... An upper-level low will move northeastward
into the mid Mississippi Valley on Friday as southwest mid-level
flow remains from the Southeast into the Carolinas. By afternoon,
a moist airmass will be located from eastern Alabama to South
Carolina. This airmass is forecast to remain weakly unstable
during the day. Thunderstorms are forecast to first develop in
Alabama during the morning and then spread eastward across Georgia
and South Carolina during the afternoon. Deep-layer shear of 40
to 50 kt across the moist sector will make conditions supportive
of marginally severe storms. The best chance for a severe threat
may develop in the early evening across parts of South Carolina as
moisture advection increases surface dewpoints into the mid to upper
60s F. As a result, MLCAPE may peak in the 500 to 750 J/kg range
across parts of southern and eastern South Carolina. The stronger
storms could have an isolated wind damage threat. A marginal tornado
threat will also be possible, associated with storms that remain
discrete. The marginal severe threat may affect parts of southern
North Carolina during the late evening and early overnight period.
..Broyles.. 12/30/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0226 AM CST Wed Dec 30 2020
Valid 021200Z - 071200Z
...DISCUSSION... ...Saturday/Day 4 to Sunday/Day 5...
An upper-level low is forecast to move across the mid Mississippi
Valley on Saturday as southwest mid-level flow remains over much
of the Southeast. At the surface, a cold front is forecast to move
across the eastern Gulf Coast States. Thunderstorm development will
be possible ahead of the front during the day from northern Florida
into southeastern Georgia and South Carolina. Although surface
dewpoints should be in the 60s F ahead of the front, instability is
forecast to be very weak suggesting that any severe threat should
be marginal.
On Sunday, an upper-level trough is forecast to move through the
central Appalachians as another upper-level trough moves into the
Ozarks and Arklatex. At the surface, a cold front is forecast to
advance southward across the Florida Peninsula. Marginally severe
storms will be possible along and ahead of the front in southern
Florida Sunday afternoon.
...Monday/Day 6 to Wednesday/Day 8... On Monday and Tuesday, surface
high pressure is forecast to be in place across the eastern third of
the nation, which should limit thunderstorm potential. On Wednesday,
the models suggest an upper-level trough will move eastward
across the southern U.S. The models have large spread concerning
the timing of the upper-level trough. Some moisture return could
occur ahead of the trough in the western part of the Gulf Coast,
where marginally severe storms can not be ruled out. However,
uncertainty is substantial at this range in the forecast period.
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0118 AM CST Wed Dec 30 2020
Valid 301200Z - 311200Z
...NO CRITICAL AREAS...
...Synopsis... Upper-level troughs will impact the upper Great Lakes
into the Northeast as well as the Texas Coastal Plains today. Cool
weather and precipitation will limit fire weather concerns across
much of the CONUS. In the West, a relatively amplified ridge
will exist across the Great Basin to start the period before an
upper-level trough digs southward along the California coast. This
pattern will once again mean a moderate offshore gradient will impact
portions of southern California into the afternoon. RH of 5-20% is
possible, especially in portions of the higher terrain, along with
the usual enhanced surface winds in wind-prone locations. Despite
these factors, significant fire weather concerns are not expected
given recent rain/snow across these areas. Given the amount of
precipitation that occurred, larger fuels (i.e., 1000-hour) that
have remained drier would be the primary fire carrier. Furthermore,
duration of these dry/windy conditions will also be limited. No
areas will be highlighted, though localized concerns are certainly
possible.
..Wendt.. 12/30/2020
...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
0125 AM CST Wed Dec 30 2020
Valid 311200Z - 011200Z
...NO CRITICAL AREAS...
...Synopsis... Two upper-level shortwave troughs will form a broader
cyclonic circulation across the south-central CONUS on Thursday. The
cooler weather and precipitation associated with these systems will
limit fire weather concerns across a large portion of the CONUS. In
the wake of the western-most shortwave trough, upper-level ridging
will build across the West Coast. With the Great Basin surface high
intensifying toward Friday morning, moderate offshore winds are
possible in southern California. Concern regarding moistened fuels
continues. RH also appears to be higher than on Wednesday. Even if
model guidance is too moist with surface conditions, it does not
appear that fire weather concerns will be more than localized to
the typical terrain-favored locations.
..Wendt.. 12/30/2020
...Please see www.spc.noaa.gov/fire for graphic product...
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If there is any better use for being famous and respected than
using that status to question orthodoxy, I haven't found it yet.
-- Eric S. Raymond, in "We Don't Need the GPL
Anymore"
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