RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Mon Jul 24 12:25:02 UTC 2017.
No Mesoscale Discussions are in effect as of Mon Jul 24 12:25:02 UTC 2017.
Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0500 AM CDT Mon Jul 24 2017
Valid 271200Z - 011200Z
...DISCUSSION...
Medium-range models appear to be in fairly good large-scale
agreement through roughly Day 6/Saturday, in depicting fairly
substantial amplification of the upper flow field. The eventual
result will be troughing/cyclonic flow covering the eastern half of
the U.S. and a large ridge over the West.
Prior to establishment of the longer-wavelength eastern trough, an
initial short-wave trough will advance steadily across the Great
Lakes and into the Northeast day 4/Thursday, accompanied by a
similarly progressing surface cold front. While the front should
focus a zone of showers and storms, questions regarding overall
degree of warm-sector instability exist. While the Ohio vicinity
may be a focus for somewhat greater severe risk given hints of ample
CAPE/shear, confidence is not great enough to add an areal highlight
at this time.
An isolated severe risk may also evolve across portions of the high
Plains region day 4, as a weak disturbance cresting the ridge may
enhance convective potential within a low-level upslope flow regime.
However,instability appears likely to remain limited across this
area as well.
As the front moves offshore day 5, and ridging amplifies days 5-6
over the west, the High Plains would likely remain the primary focus
for isolated severe storms. However, substantial/organized severe
risk is not evident at this time.
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SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0314 AM CDT Mon Jul 24 2017
Valid 241200Z - 251200Z
...CRITICAL FIRE WEATHER AREA FOR DRY THUNDERSTORMS ACROSS SOUTHERN
OR...NORTHEAST CA...SOUTHWEST ID...FAR NORTHERN NV...
...CRITICAL FIRE WEATHER AREA FOR DRY THUNDERSTORMS ACROSS FAR
EASTERN ID INTO SOUTHWEST MT...
...Synopsis...
An upper trough off of the northern California coast is expected to
remain nearly stationary or drift slowly eastward today, while a
stronger upper trough and associated surface low/cold front move
eastward across the southern Canadian Prairies and northern High
Plains.
...OR/Northern CA northeast into MT - Dry Thunderstorm Threat...
Scattered thunderstorms are expected across a broad zone from
Oregon/northern CA northeast into portions of MT, as the slow-moving
upper trough gradually moves inland and smaller-scale features ahead
of the primary trough move from the Great Basin into the northern
Rockies. Thermodynamic profiles will favor a mix of wet and dry
thunderstorms, though with coverage expected to be relatively high
in an area where fuels are quite dry, this activity is expected to
pose a substantial fire weather threat.
Two critical areas were delineated - one across southern OR/northern
CA/southwest ID, in closer proximity to the primary upper trough,
and also from eastern ID into southwest MT, where a smaller-scale
embedded trough and terrain-enhanced circulations may favor the
development of a forward-propagating thunderstorm cluster this
afternoon/evening. An isolated dry-thunderstorm threat will extend
potentially as far east as eastern MT, depending on the timing of
convection moving in from the southwest. Strong and erratic outflow
winds may accompany any of the thunderstorm activity across the
region, especially across portions of southwest into central MT.
...Portions of Montana into the western Dakotas - Elevated Wind/RH
Threat...
Somewhat cooler temperatures are expected across portions of MT and
eastern ID into the western Dakotas compared to Sunday. However, dry
westerly/northwesterly post-frontal flow will allow for low RH
(potentially down to critical levels) to develop during the
afternoon. In conjunction with these low RH values, anticipated
sustained wind speeds of 15-20 mph (with locally higher gusts) will
result in the potential for elevated to locally critical conditions.
Confidence in the development of critical wind speeds remains too
low for a critical upgrade (for wind/RH concerns) at this time.
However, erratic thunderstorm outflow winds will also be possible
across primarily southern portions of the elevated area (see section
above for discussion of thunderstorm potential) during the late
afternoon and evening.
..Dean.. 07/24/2017
...Please see www.spc.noaa.gov/fire for graphic product...
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SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0314 AM CDT Mon Jul 24 2017
Valid 251200Z - 261200Z
...Synopsis...
Little change to the overall pattern is expected on Tuesday, as a
slow-moving upper trough edges eastward into northern California and
the Great Basin, while an upper ridge remains in place across the
Southwest into portions of the southern/central Plains. At the
surface, a trough will extend across much of the Plains south of a
surface low near Hudson Bay, while high pressure settles into the
Northeast. Generally weak surface features are expected across most
of the West.
...OR/Northern CA eastward into southern MT...
Scattered to numerous thunderstorms are again expected from
OR/northern CA eastward into southern MT, with the slow-moving upper
trough and embedded smaller-scale features remaining in the
vicinity. Thermodynamic profiles are again expected to support a mix
of wet and dry thunderstorms, with perhaps a slight tendency for
greater rainfall potential given gradually increasing moisture with
time and low-level cooling in some areas from repeated rounds of
convection. Given uncertainties regarding the dryness of the
thunderstorms, no critical area has been introduced for the threat
at this time, though there will definitely be a threat of
lightning-induced ignitions in areas where rainfall remains
relatively light.
...Portions of eastern MT into the western Dakotas...
Locally elevated conditions will be possible across portions of
eastern MT into the western Dakotas within a dry post-frontal
airmass. However, winds are not expected to be particularly strong
and confidence in the concurrence of stronger winds and
near-critical RH is too low for an elevated area at this time.
..Dean.. 07/24/2017
...Please see www.spc.noaa.gov/fire for graphic product...
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