ZCZC SPCFWDDY1 ALL
FNUS21 KWNS 261601
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1101 AM CDT Wed Jul 26 2017
Valid 261700Z - 271200Z
The ongoing isolated dry-thunderstorm area has been adjusted in two
areas to reflect the latest observational/guidance trends. First,
the area has been removed from portions of southern Idaho, where
tropospheric moisture content appears too high for a substantial
dry-thunderstorm threat today. Regardless, gusty outflow winds may
lead to erratic behavior with ongoing fires. Second, the western
portion of the dry-thunderstorm area has been expanded towards the
northern Sierra Nevada. As the northern California impulse lifts
east/northeast, ascent along its leading edge will bolster
convective development on higher terrain today. The 12Z REV sounding
sampled 0.74" of PW this morning, indicating an environment still
favorable for a few dry storms and related ignitions.
..Picca.. 07/26/2017
.PREV DISCUSSION... /ISSUED 0220 AM CDT Wed Jul 26 2017/
...Synopsis...
The slow-moving midlevel low centered over northern CA is forecast
to begin ejecting northeast today, though otherwise the pattern will
change little compared to previous days, with an upper ridge
persisting across the Southwest into the southern Plains. A weak
surface ridge will settle into portions of the central and northern
Plains in the wake of a cold front, resulting in light winds and
slightly cooler conditions.
...OR/Northern CA eastward into southern MT...
Scattered thunderstorms are expected over many of the same areas
that have been affected on previous days, in advance of the
persistent midlevel low over northern CA. Thermodynamic profiles
will may be slightly cooler and more moist compared to previous
days, due to the cumulative effects of repeated rounds of
convection. However, widespread wetting rainfall is not anticipated,
and some threat for lightning-related ignitions will continue where
dry fuels remain across the region. As a result, the dry
thunderstorm area is maintained across the area with only minor
adjustments.
...Please see www.spc.noaa.gov/fire for graphic product...
ZCZC SPCFWDDY2 ALL
FNUS22 KWNS 261849
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0149 PM CDT Wed Jul 26 2017
Valid 271200Z - 281200Z
No changes to the ongoing forecast are necessary. See below for more
details.
..Picca.. 07/26/2017
.PREV DISCUSSION... /ISSUED 0221 AM CDT Wed Jul 26 2017/
...Synopsis...
The midlevel low/trough that has persisted for several days near
northern CA is expected to weaken and become absorbed into broad
southwesterly flow ahead of a strong cyclone over the northeast
Pacific. At the surface, in response to the ejecting system, low
pressure is expected to deepen slightly over portions of
Alberta/Saskatchewan and the northern Rockies/High Plains, with
generally weak surface features elsewhere across the CONUS.
...Northern OR into Central/Eastern WA...
Dry and breezy conditions are expected in the lee of the Cascades of
WA/OR on Thursday, in the wake of a cold frontal passage. Current
guidance suggests the potential for westerly winds of 15-20 mph and
minimum RH values of 15-25%, sufficient for an elevated fire-weather
risk. A modest increase in anticipated wind speeds would result in a
critical threat across the area, but at this time confidence in
sustained winds greater than 20 mph is too low for any upgrade.
...ID into Western/Central MT and Northwest WY...
Scattered thunderstorms are again expected as the aforementioned
ejecting system moves across the area. Forecast thermodynamic
profiles continue to suggest the potential for a mix of wet and dry
thunderstorm activity, resulting in some threat for ignitions in
areas of dry fuels.
...Northern/Eastern MT into the Western Dakotas...
A modest increase in surface winds is possible across portions of
northern/eastern MT into the Western Dakotas, in response to
developing low pressure over portions of AB/SK. Meanwhile, with
low-level moisture expected to remain rather limited, strong heating
could result in near-critical RH values during the afternoon. These
factors could result in elevated fire weather conditions over
portions of the region. However, quite a bit of uncertainty remains
regarding the strength of low-level flow across the area, so no
elevated delineation has been made at this time.
...Please see www.spc.noaa.gov/fire for graphic product...
