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LU9DCE > ALERT 11.09.20 18:03z 92 Lines 4925 Bytes #999 (0) @ WW
BID : 25203_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 11 09
Path: HB9ON<IW8PGT<IZ3LSV<IR1UAW<I0OJJ<LU4ECL<VK2RZ<W0ARP<KF5JRV<N7HPX<
LU9DCE
Sent: 200911/1800Z 25203@LU9DCE.TOR.BA.ARG.SOAM LinBPQ6.0.20
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
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SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745
AM CDT Fri Sep 11 2020
Valid 111300Z - 121200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY... Organized severe thunderstorms are not expected today.
...Synopsis... In mid/upper levels, mean ridging over the
southeastern CONUS will be shunted eastward as a long-lived,
well-defined cyclone (now centered over southeastern WY) shifts
eastward. A fast-moving shortwave trough initially over northern BC
will cross central Canada through the period, spreading height falls
across south- central Canada to the northern border areas of ND/MN.
As this occurs, the cyclone will move across the central Plains,
with its 500-mb low near CDR by 00Z and approaching YKN by 12Z.
In the associated southwesterly-flow field to its southeast, a
subtle perturbation -- now apparent in moisture-channel imagery
over portions of western/central OK and central KS -- should
eject northeastward over parts of IA and northern MO through late
afternoon.
At the surface, 11Z analysis showed a low offshore ACK with cold
front across eastern MD, central/southern WV, and southern portions
of IL, becoming quasistationary through a sharp bend over central/
southern MO, south-southwestward over the Arklatex and near GLS,
to Gulf waters just offshore BRO. The frontal segment from MO
to east TX should move little through the day on broader scales.
However mesobeta-scale westward then eastward shift may occur
in MO today in response first to return flow and low-level warm
advection, then more directly influenced by the approach of the
mid/upper cyclone.
...MO, southeastern IA, extreme western IL... Widely scattered to
scattered thunderstorms are possible this afternoon into evening,
within a plume of convection and precip forecast to develop over
central/northeastern MO into eastern IA, and perhaps extreme
western IL. A few strong gusts may occur, but severe potential
still appears minimal.
Modest, marginally convectively unstable lapse rates aloft, and
limitations to surface heating by cloud cover, will preclude the
development of strong buoyancy, despite the rich low-level moisture
present and expected east of the front. In the absence of intense
diurnal mixing, a plume of surface-based parcels should maintain
upper 60s to low-70s F surface dew points, and PW in the 1.5-1.8-
inch range (consistent with latest GPS & sounding obs). This will
support MLCAPE potentially strengthening into the 500-1200 J/kg
range across central/northeastern MO into parts of southeastern IA
this afternoon.
Height gradients and large-scale lift will increase east of the
cyclone and near the ejecting minor perturbation, further supporting
the convective environment. However, the vertical wind profile
will be substantially unidirectional in alignment with the zone
of convective forcing, suggesting quick transition from initial
development into messy, training modes, with the contribution to 30-
40-kt effective-shear magnitudes mainly related to speed shear.
Given these offsetting factors, an isolated/brief strong storm
cannot be ruled out. However, the severe threat remains too low
to draw unconditional probabilities.
..Edwards/Broyles.. 09/11/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0305 AM CDT Fri Sep 11 2020
Valid 141200Z - 191200Z
...DISCUSSION... Severe potential appears low for much of the Day
4-8 period. Upper ridging will persist across the western states
and over the southeastern U.S. Progressive northern-stream flow
will flatten the upper ridge across the northern tier of the U.S.,
but guidance varies on how far south any of the stronger upper
shortwave troughs across Canada may develop into the U.S. There is
some indication that a deeper trough may shift southeast from the
Canadian Prairies and track across the Midwest and then eastward
across the eastern states by the Day 7 or 8 time frame. If this
occurs, a moist airmass will be in place across the Midwest/Great
Lakes vicinity, and thunderstorm activity would be likely with
any cold frontal passage. However, confidence in this scenario,
and any accompanying severe potential, is low given disparity among
forecast guidance.
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Una frase puede cambiar un destino.
-- George Fischer.
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