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LU9DCE > ALERT 22.06.21 18:37z 144 Lines 7265 Bytes #999 (0) @ WW
BID : 951_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 22-JUN2021
Path: HB9ON<IW8PGT<IZ3LSV<I3XTY<I0OJJ<EA2RCF<LU9DCE
Sent: 210622/1830Z 951@LU9DCE.TOR.BA.ARG.SOAM BPQ6.0.21
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
Copyright 2021 Eduardo A. Castillo
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Storm Prediction Center
en-us
None
Tue, 22 Jun 2021 13:56:01 +0000
Tue, 22 Jun 2021 13:56:01 +0000
general
1
No watches are valid as of Tue Jun 22 13:56:01 UTC 2021.
Tue, 22 Jun 2021 13:55:09 +0000
No Mesoscale Discussions are in effect as of Tue Jun 22 13:56:02 UTC 2021.
Tue, 22 Jun 2021 13:55:08 +0000
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0750 AM CDT Tue Jun 22 2021
Valid 221300Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
IOWA AND EASTERN NEBRASKA...
...SUMMARY...
The greatest severe-thunderstorm threat will be for gusts and hail
this afternoon into tonight over portions of Nebraska and Iowa.
...Synopsis...
In mid/upper levels, the CONUS will remain characterized by a
high-amplitude pattern of progressive eastern troughing and western
ridging, and a slowly meandering cyclone of the norther CA
coastline.A series of shortwaves will pivot through the expansive
area of cyclonic flow related to the eastern trough -- including one
now apparent in moisture-channel imagery from near the IN/OH line
south-southwestward to MS.That perturbation should eject
northeastward across the central Appalachians to the Mid-Atlantic
and western New England by 00Z.A weak shortwave trough evident
over the northern CA/southwestern OR region should move slowly
north-northeastward over OR today and penetrate the broader-scale
ridge over ID tonight.
The 11Z surface analysis showed a seasonally strong cold front from
Maine to central VA, western NC, central AL, central LA, south-
central TX, and northern Chihuahua.This front should move offshore
from New England by 00Z, while reaching eastern NC, central GA,
southern AL and southern LA, while decelerating/stalling from LA
westward over south TX.Overnight, the front should stall over
southern SC, southern GA and southern AL, while moving back north as
a warm front and weakening farther west over TX.A separate,
developing warm front was drawn from a weak low over eastern WY
across the Pine Ridge area of southern SD, to east-central NE and
the MKC area.This boundary should move slowly northeastward
through this evening.
...NE/IA region...
Isolated to scattered thunderstorms are possible from late this
afternoon into this evening, mainly along and northeast of the
surface warm front, with the larger potential coverage (but amidst
weaker surface-based instability) being over the eastern parts of
the outlook in IA.Hail and isolated strong to damaging gusts are
possible.A more-conditional yet potentially greater-magnitude
hail/wind threat exists near the Missouri River and westward over
eastern NE, where strong surface heating and residual moisture
(dewpoints reaching the 50s F) will erode most or all of the MLCINH
and create well-mixed boundary layers amendable to maintaining hail
and intense downdrafts to the surface.MLCAPE 500-1500 J/kg should
develop across much of the outlook area.
The eastward shift of the major synoptic trough, related height
rises in this region, and lack of substantial northwest-flow
perturbations to contribute large-scale ascent aloft, collectively
impart some concern about enough convective coverage/longevity for a
severe threat.Low-level flow generally will be weak, until a 30-40
kt LLJ ramps up after 00Z to support nocturnal convective potential
in IA.Still, progs have been consistent in the idea of generating
at least isolated surface-based convection near the warm-frontal/
surface convergence zone, and in a supercell-favorable wind profile.
Forecast soundings reasonably suggest 21-00Z effective-shear
magnitudes in the 45-55-kt range, given the veering with height in
the lowest 300 mb and the favorably strong mid/upper-level
northwesterlies.
...Southeastern CONUS...
An ongoing swath of precip -- with embedded convection including
widely scattered thunderstorms -- should continue to shift eastward
across the southern GA/eastern FL Panhandle/northern FL region
through the afternoon.Other isolated to scattered thunderstorms
are possible today, northeastward across parts of the Carolinas to
the Delmarva/Tidewater area, and perhaps in a zone of near-frontal
airmass recovery behind the morning activity over parts of
GA/southeastern AL and the FL Panhandle.The latter area appears to
be the most conditional, given the extensive clouds/precip now over
that region.Isolated damaging to marginally severe gusts are
possible.
A richly moist prefrontal air mass is in place, with surface dew
points in the upper 60s to mid 70s F.Modest midlevel lapse rates
will limit buoyancy, however, with MLCAPE generally in the 800-1200
J/kg range.Weak low-level shear will exist over most of the area,
though portions of the outlook from northern NC northeastward will
have strong flow in upper levels and greater cloud-layer shear to
aid in local storm organization.Convective/severe potential should
diminish gradually after dark.
...Northeastern NM and vicinity...
Isolated to widely scattered, high-based thunderstorms may form
through the afternoon over the eastern slopes/foothills of the
Sangre de Cristo Mountains of NM,as well as eastward over the Raton
Mesa.Activity should move southeastward a short distance across
the adjoining plains, mesas and canyons, offering isolated severe
gusts.Relatively warm midlevel temperatures near the upper ridge
will keep lapse rates aloft modest.Still, available/marginal
low-level moisture and strong diabatic surface heating of higher
terrain should minimize MLCINH and support higher-elevation
convective development beginning early this afternoon.Deep, well-
mixed subcloud layers beneath 500-800 J/kg peak MLCAPE, along with
enough directional shear to support effective-shear magnitudes
around 35-40 kt, will support some organization before activity
weakens near the eastern parts of the outlook area.
...Interior Northwest...
Isolated to widely scattered, high-based thunderstorms are forecast
to develop across the outlook area this afternoon and move northward
to northeastward, offering a threat for isolated severe downdrafts.
Low/middle-level moisture will be favorable, with PW values near an
inch, while diurnal heating and large-scale lift related to the
slow-moving shortwave trough contribute to favorably steep low/
middle-level lapse rates.The result should be an area of
preconvective MLCAPE in the 500-800 J/kg range, atop a deep and
well-mixed boundary layer conducive to downdraft acceleration.
Effective-shear magnitudes of 30-40 kt in forecast soundings support
some potential for organized convection.
..Edwards/Broyles.. 06/22/2021
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Tue, 22 Jun 2021 12:59:36 +0000
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