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LU9DCE > ALERT    17.08.18 09:15l 177 Lines 9831 Bytes #8 (0) @ WW
BID : 25667_LU9DCE
Subj: Storm Prediction Center 17 08 2018
Sent: 180817/0701Z @:LU9DCE.TOR.BA.ARG.SOAM #:25667 [TORTUGUITAS] $:25667_LU9DC

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 SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1243
AM CDT Fri Aug 17 2018
Valid 171200Z - 181200Z
...SUMMARY...  Isolated severe thunderstorms with mainly a strong
to damaging wind threat will be possible this afternoon and evening
across parts of the Northeast. Additional storms may produce sporadic
strong wind gusts from the central High Plains to the Ohio and
Tennessee Valley vicinity, and across parts of the northern Rockies.
A larger-scale upper trough will shift eastward across the Midwest
and Northeast today. Several embedded shortwave impulses will
provide focus of strong to severe thunderstorms today from the
southern Plains into the OH/TN Valley vicinity and portions of
the Northeast. Additional strong storms are possible across the
central/southern High Plains in moist upslope flow regime as a weak
perturbation drops south/southeast on the eastern periphery of the
Rockies upper ridge. Isolated strong wind gusts also are possible
across parts of the northern Rockies as a weak shortwave impulse
provides support for isolated high-based thunderstorms.
A warm front will quickly lift northward across northeast NY
and VT/NH this morning. South of the front, surface dewpoints in
the upper 60s to low 70s are expected. Modest heating, with highs
generally from the upper 70s into the 80s, will be sufficient for the
development of 1000-2000 J/kg MLCAPE. Deep-layer south/southwesterly
flow will increase with the approach of the upper trough and
thunderstorms are expected by early afternoon in the vicinity of a
prefrontal trough across eastern PA/NY, as well as along the warm
front across VT/NH into southern New England. 25-35 kt effective
shear will be sufficient for organized clusters and marginal
supercell structures capable of strong, locally damaging wind
gusts and marginal hail. While low-level shear is not particularly
impressive, backed low-level winds in the vicinity of the surface
trough and warm front, coupled with forecast mean mixing ratios
around 16 g/kg, a brief tornado or two can not be ruled out.
Additional thunderstorms may develop later in the evening as
a surface cold front shifts southward from Quebec, but severe
potential will be limited as boundary-layer stabilization ensues
with loss of daytime heating.
...AR into the OH/TN Valley Vicinity...
Ongoing convection at the beginning of the period will impact where
stronger storm develop/re-intensify later this afternoon. Current
best guess is that convection moving into the lower OH valley
vicinity this morning may persist and re-strengthen across KY/TN
where a moist and unstable airmass is in place.  Modest deep-layer
shear will result in multicell clusters and downburst winds will be
the main concern with any surging/bowing line segments that develop.
Additional convection is possible along residual outflow across AR
into western TN/MS.  Shear will become even weaker with southward
extent, but strong instability combined with PW values near 2
inches will continue to foster downburst wind potential with any
stronger clusters.
...Central/Southern High Plains...
Thunderstorms will develop in weak upslope flow regime as a weak
impulse migrates across the central Rockies. Strong heating and
modest boundary layer moisture will result in a corridor of moderate
instability across eastern CO into parts of the OK/TX Panhandles.
High-based convection will mainly pose a strong wind threat as cells
struggle to maintain intensity due to lack of stronger deep-layer
shear. Additionally, some marginally severe hail is possible with
any stronger cell that can develop given steep midlevel lapse rates.
...Northern Rockies...
Strong heating and modest boundary-layer moisture beneath steep
midlevel lapse rates will promote isolated thunderstorm develop
during the afternoon and evening. High-based thunderstorms will
mainly pose a dry microburst threat given inverted-v thermodynamic
profile, and a few strong wind gusts are expected.
..Leitman/Dean.. 08/17/2018
 SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1149
PM CDT Thu Aug 16 2018
Valid 181200Z - 191200Z
...SUMMARY...  Isolated severe storms will be possible across the
High Plains region on Saturday afternoon and evening.
...High Plains..  A shortwave trough should slide southeast from
ID into the central High Plains, although guidance does differ in
both amplitude and spatial location of the trough by 12Z Sunday. The
bulk of enhanced mid-level northwesterlies should spread from the
eastern Great Basin to the southern Rockies with weaker flow with
eastern extent across the Great Plains.
Scattered to numerous storms are expected from western SD south
into eastern NM/TX Panhandle vicinity during the late afternoon and
evening along the lee trough. The modest deep-layer wind profiles
will largely support multicell clusters with a mix of isolated severe
hail and wind. A conditional risk for a few supercells will also
exist across the southern High Plains. Here, late D1 convection
could linger Saturday morning, yielding a mesoscale outflow
boundary and increased low-level SRH to its north. In addition,
a 30-35 kt southerly low-level jet will promote MCS development
Saturday evening. This appears to be the most likely region for
a focused upgrade to SLGT risk in later outlooks if confidence
increases regarding mesoscale boundary placement.
...MAXIMUM RISK BY HAZARD...  Tornado:   2%     - Marginal Wind:
5%     - Marginal Hail:      5%     - Marginal
..Grams.. 08/17/2018
 SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0140 AM CDT Fri Aug 17 2018
Valid 171200Z - 181200Z
...Synopsis...  An upper-level trough is expected to move eastward
from the Pacific Northwest into the northern Rockies today, bringing
an increase in midlevel flow and also the potential for scattered
thunderstorms. At the surface, a modestly enhanced pressure gradient
will develop across portions of the Columbia River basin in the
wake of the upper trough.
...Interior Northwest into the Northern Rockies...  Thunderstorms may
be ongoing this morning across portions of ID/eastern OR/eastern
WA, with additional development expected this afternoon/evening
expanding into a larger portion of the northern Rockies as the
upper trough moves eastward. At least scattered coverage of
thunderstorms is expected, with PW values sufficient for some
wetting rainfall. However, given the potential for substantial
lightning activity across a region of receptive fuels, the threat
for ignitions is sufficient to maintain an isolated dry-thunderstorm
delineation across this area.
...Columbia River Gorge...  Elevated conditions are possible across
the Columbia River Gorge and vicinity, with the increased pressure
gradient resulting in winds of 15-20 mph as RH values drop below 20%.
...Northern Great Basin...  A modest increase in low-to-midlevel flow
is expected across parts of the northern Great Basin in the wake
of the upper trough passing to the north. Wind speeds of 15-20 mph
combined with RH values dropping below 15% will result in elevated
fire weather conditions.
..Dean.. 08/17/2018
...Please see for graphic product...
 SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK
0141 AM CDT Fri Aug 17 2018
Valid 181200Z - 191200Z
...Synopsis...  An upper trough is expected to move eastward from the
northern Rockies into the northern/central Plains on Saturday. Drier
and somewhat cooler conditions are expected in the wake of a cold
front across the northern Rockies. Relatively weak low-level flow
is expected to generally limit the fire-weather threat.
...Southern ID...Northern UT...Southwest WY...  Locally elevated
conditions will be possible across portions of the Snake River
Plain on Saturday, potentially extending into parts of northern
UT/southwest WY, as modest low-level westerly flow develops in
the wake of the upper trough and RH values drop into the 10-25%
range. However, given uncertainty regarding the strength of the winds
across the Snake River Plain, and the extent of RH reduction across
southwest WY, no Elevated delineation has been made at this time.
..Dean.. 08/17/2018
...Please see for graphic product...


Put a pot of chili on the stove to simmer.  Let it simmer.  Meanwhile,
broil a good steak.  Eat the steak.  Let the chili simmer.  Ignore it.
		-- Recipe for chili from Allan Shrivers, former governor
		   of Texas.

\\\     Eduardo Castillo  --- ---     \\\
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