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LU9DCE > ALERT 27.12.21 23:30z 277 Lines 13091 Bytes #999 (0) @ WW
BID : 690_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 27-DIC.21
Path: HB9ON<IW8PGT<LU4ECL<HR1PAQ<TI0RC<W0ARP<KF5JRV<VE3CGR<LU9DCE
Sent: 211227/2231Z 690@LU9DCE.TOR.BA.ARG.SOAM LinBPQ6.0.22
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
Copyright 2021 - Eduardo A. Castillo
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SPC Forecast Products Storm Prediction Center en-us None
spc.feedback@noaa.gov (spc.feedback@noaa.gov)
spc.feedback@noaa.gov (spc.feedback@noaa.gov) Mon, 27 Dec 2021
12:01:02 +0000 Mon, 27 Dec 2021 12:01:02 +0000 general 1
SPC Forecast Products
SPC - No watches are valid as of Mon Dec 27 12:01:02 UTC 2021 No
watches are valid as of Mon Dec 27 12:01:02 UTC 2021. Mon, 27
Dec 2021 12:00:08 +0000
SPC MD 2063 MD 2063 CONCERNING FREEZING RAIN FOR PORTIONS OF
FAR WESTERN MD...WESTERN/CENTRAL PA...AND FAR SOUTHWESTERN NY
Mesoscale Discussion 2063 NWS Storm Prediction Center Norman OK 0558
AM CST Mon Dec 27 2021
Areas affected...Portions of far western MD...western/central PA...and
far southwestern NY
Concerning...Freezing rain
Valid 271158Z - 271700Z
SUMMARY...Freezing rain rates may exceed 0.05 inch per 3 hours through
the morning, before precipitation gradually transitions to rain from
west to east this afternoon.
DISCUSSION...A fairly broad area of precipitation is moving eastward
this morning from eastern OH into western PA and vicinity. This
activity is being aided by strong warm/moist advection associated with
a 45-50 kt southwesterly low-level jet over the OH Valley. This
feature is expected to shift eastward across the central Appalachians
over the next several hours in tandem with the ongoing precipitation
shield. Dry air in the low/mid levels noted on the 00Z sounding from
PIT still exists across parts of western/central PA and vicinity. But,
gradual moistening of the low levels will occur this morning with
light to moderate precipitation continuing to overspread this region.
Surface temperatures are generally below freezing, and wet bulb
cooling will likely aid in sub-freezing temperatures being maintained
through much of the morning, especially across higher terrain. A warm
nose aloft associated with the strong low-level warm advection will
likely support partial to total melting of hydrometeors. An initial
mix of snow/sleet should transition fairly quickly to mostly freezing
rain this morning. Freezing rain rates around 0.05 inch per 3 hours
may occur, with locally greater rates possible in higher terrain. The
freezing rain should gradually transition to rain from west to east
from late morning into the early afternoon.
..Gleason.. 12/27/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BUF...CTP...LWX...PBZ...
LAT...LON 40407916 40967918 41027941 41197970 41377987 41587958
41777918 41947890 42147859 42157822 41757801 41257758
40607777 39787837 39577884 39397918 39487940 40407916
Read more
Mon, 27 Dec 2021 11:59:04 +0000
SPC Dec 27, 2021 0830 UTC Day 3 Severe Thunderstorm Outlook SPC
0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM
CST Mon Dec 27 2021
Valid 291200Z - 301200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
MISSISSIPPI RIVER VALLEY TO NEAR THE CUMBERLAND PLATEAU...
...SUMMARY...
Severe thunderstorms are possible for portions of the Deep South into
the southwestern Appalachians.
...Synopsis...
A mid-level shortwave trough will move from the central/southern High
Plains Wednesday morning to the Great Lakes by early Thursday. A lee
cyclone is expected to develop near the Oklahoma Panhandle and move
east along the surface front into the mid-Mississippi Valley and
eventually the western Ozarks by Thursday morning. In addition, most
guidance hints at a weak mid-level shortwave moving out of northern
Mexico and over the warm sector Wednesday afternoon/evening.
...Deep South into the Southwestern Appalachians...
Most guidance suggests some convection may be ongoing at the beginning
of the period near the Red River across northeast Texas. In that
area, isentropic ascent will be increasing as the low-level jet
strengthens in response to the ejecting mid-level shortwave trough. As
these thunderstorms continue east-northeast, they will encounter an
increasingly unstable airmass across southern Arkansas and northern
Louisiana, where mid 60s dewpoints will be present by mid to late
morning. Supercell wind profiles are expected across the entire warm
sector with 50 to 65 knots of effective vertical shear. Therefore,
this activity could be severe during the morning hours across portions
of southern Arkansas and northern Louisiana.
Regardless of the evolution of this early day storm activity,
additional storm development is expected during the afternoon hours.
Then, the influence of the weak southern stream mid-level shortwave
trough overspreads the warm sector, and the surface low moves out of
the Plains and into the Mid-Mississippi Valley. There are still
uncertainties with respect to storm coverage, given the low-amplitude
nature of mid-level features and the strength of the associated
surface low. These uncertainties also impact expected storm intensity
due to the influence on the low-level wind field. Most guidance shows
a broad 40 knot low-level jet with a peak around 50 kts eventually
moving into eastern Tennessee Wednesday night. However, the weak
surface low results in light surface winds across much of the warm
sector. This would be a limiting factor to the tornado threat, and
especially the significant tornado threat, which would be greater with
a stronger surface low such as is depicted by the 00Z NAM.
Given the uncertainties mentioned above, a slight risk seems justified
at this time. However, if model guidance trends toward a stronger
system or if more widespread warm sector convection appears likely, an
enhanced risk may be needed in later outlooks.
..Bentley.. 12/27/2021
Read more
Mon, 27 Dec 2021 08:31:03 +0000
SPC Dec 27, 2021 Day 4-8 Severe Weather Outlook Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0347
AM CST Mon Dec 27 2021
Valid 301200Z - 041200Z
...DISCUSSION...
...Day6/Saturday - Deep South into the Tennessee Valley...
Global operational and ensemble guidance has come into better
agreement for the western CONUS trough, which has been persistent for
the past 7 to 10 days, to advance eastward this weekend. A maritime
tropical airmass is expected across much of the Southeastern United
States by Wednesday as low-level trajectories from the Caribbean will
remain for the entire week. A very moist airmass will be in place
ahead of this trough as it advances east. Therefore, severe weather
is possible across portions of the Deep South and Tennessee Valley on
Saturday.
Despite improved agreement with respect to the timing of the
upper-level trough, there remains significant disagreement regarding
the evolution of the pattern. The UKMET and operational GFS show a
more phased upper-level pattern, and therefore a stronger and
farther-north surface low. The ECMWF, however, shows a lead wave
moving through the Ohio Valley followed by a second wave moving
through the Tennessee Valley Sunday night. The GEM and ECMWF ensemble
mean show a surface low moving along the Ohio River and more than half
the individual GEFS members show something similar. Therefore, the 15
percent probabilities were drawn with the expectation of a surface low
tracking along the Ohio River. Changes to the evolution of the system
are expected, and later outlooks will adjust probabilities as
necessary. At this time, the 15 percent contour highlights the
corridor with the greatest confidence for thunderstorm coverage in an
unstable and strongly sheared environment.
Read more
Mon, 27 Dec 2021 09:50:12 +0000
SPC Day 1 Fire Weather Outlook SPC Day 1 Fire Weather
Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0106
AM CST Mon Dec 27 2021
Valid 271200Z - 281200Z
...Synopsis...
Early-morning surface observations across the High Plains/Southern
Plains show poor overnight RH recovery (with RH values in the teens to
30s) after strong downslope winds Sunday afternoon. Further north,
surface pressure rises are noted across the Plains in the wake of a
departing surface low, indicating building high pressure that will
keep the dry air mass in place for today. Aloft, southwesterly flow is
expected to gradually weaken, but will maintain a strong enough zonal
component for modest lee troughing this afternoon. The resultant
pressure gradient will induce breezy winds along the High Plains on
the western periphery of the dry air mass, yielding fire weather
concerns for a region with antecedent dry fuels.
...Central High Plains...
Guidance continues to show reasonably high agreement in southerly
winds increasing to 15-25 mph from eastern CO/western KS into the NE
Panhandle. While most ensemble members suggest RH reductions to 20%
are probable, drier conditions with RH values in the teens are more
likely to the east across central KS/southern NE where winds will be
somewhat weaker. This slight displacement of the lowest RH and
strongest winds, in conjunction with modest boundary-layer flow and
increasing afternoon clouds, yields low confidence in the potential
for widespread critical conditions (though localized/transient
critical conditions will likely evolve within this region).
...Eastern New Mexico...
Across eastern NM, downslope winds combined with warm temperatures
under the low-level thermal ridge will likely result in a few hours of
elevated wind/RH conditions. Although afternoon cloud cover casts some
uncertainty into the forecast, strong model consensus and receptive
fuels warrant the southward expansion.
...Western Oklahoma...
Winds are forecast to increase during the morning hours as the
pressure gradient temporarily tightens across the southern Plains.
This may result in areas of 20-25% RH with 15 mph winds by around 18
UTC. However, the regional pressure gradient is expected to weaken
through the afternoon during peak diurnal warming, which will limit
the duration of the fire weather threat.
..Moore.. 12/27/2021
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
Mon, 27 Dec 2021 07:07:38 +0000
SPC Day 2 Fire Weather Outlook SPC Day 2 Fire Weather
Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0155
AM CST Mon Dec 27 2021
Valid 281200Z - 291200Z
...Synopsis...
An upper-level shortwave, currently noted in water-vapor imagery off
the West Coast, is forecast to propagate through the southwesterly
mean flow over the Rockies early Tuesday morning. As this occurs, a
surface low is expected to deepen over the central Plains and tighten
the regional pressure gradient. The net result will be increasing
west/southwesterly winds between 15-20 mph across the central/southern
High Plains into the southern Plains Tuesday. Antecedent dry fuels
and minimal moisture return will support another day of elevated, to
potentially critical, fire weather concerns.
...Southern/Central High Plains...
Guidance over the past 24 hours has trended towards an earlier passage
of the main synoptic disturbance and places the strongest
boundary-layer flow over the MS River Valley by the afternoon hours.
Despite this displacement of the strongest flow, mostly clear to
partly cloudy skies should yield sufficient mixing to support frequent
gusts between 25-35 mph. With RH values in the 15-25% range, elevated
conditions appear likely. Critical conditions are possible, but will
most likely occur under any axes of stronger 850-700 mb flow. While
confidence in the placement of such axes is low, deterministic
solutions, backed by some ensemble guidance, suggest the most likely
corridor for critical conditions lies along and north of the I-20
corridor across west TX. A Critical risk area may be introduce in
subsequent outlooks if confidence in this corridor increases.
...Kansas...
A southward-moving cold front is expected to push across KS through
the day Tuesday. Elevated fire weather conditions are likely ahead of
this front, but the duration of the threat will be determined by the
timing of the frontal passage. Uncertainty in the longevity of fire
weather conditions increases with northward extent, and refinement of
the current risk area is possible. Regardless, the northerly wind
shift, coupled with dry post-frontal air, may impact any ongoing fire
suppression efforts.
..Moore.. 12/27/2021
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
Mon, 27 Dec 2021 07:57:40 +0000
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