Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/08/21
Area Forecast Discussion
National Weather Service Boise ID
845 PM MDT Tue Sep 7 2021
.DISCUSSION...Tons of smoke was released from fires to our west
and southwest this afternoon, and a good portion of that will move
into our area over the next day or two. There is still some hope
for improvement Friday, but there are so many fires out there now
that virtually any direction our upper level flow comes from will
bring at least some smoke into the area. Latest guidance shows a
slightly increased chance for showers/thunderstorms Thu aft/eve,
and this will be examined by the overnight shift in the next full
forecast package, once the remaining 00Z guidance arrives. No
changes are planned at this time.
.AVIATION...Widespread smoke layers with periods of MVFR-IFR
visibility and terrain obscuration. Surface winds: 10 kts or less
overnight, then SW 10-20 kts across SE Oregon and the mountains of
SW Idaho, and SE 10-20 kts across the Snake River Plain after
08/15Z, becoming W to NW area-wide after 08/21Z. Winds aloft at
10k ft MSL: NW 10-20 kts becoming SW 10-20 kts early Wednesday
SHORT TERM...Tonight through Thursday night...Air quality
advisories due to wildfire smoke have been posted for all of our
CWA by the Idaho DEQ and Oregon DEQ. In eastern Oregon the
advisory runs through at least Thursday afternoon. In Idaho the
advisories for southwest Idaho and south-central Idaho will be
updated Wednesday before 1 PM MDT. Latest HRRR smoke model
continues smoke throughout our CWA through at least Thursday
morning. Above-normal high temperatures will also continue through
Thursday as the upper ridge over the Great Basin shifts very
slowly east. Temperatures would be several degrees higher if not
for the smoke. Late Thursday night a Pacific upper trough will
reach the northwest coast. The trough will begin a chance of
showers and thunderstorms in Harney County/OR as early as
Thursday afternoon, and eastward into the Idaho Mountains late
Thursday night. Clouds will inhibit cooling Thursday night before
a cold front and showers arrive Friday morning. West winds will
increase Wednesday afternoon in eastern Oregon and in the higher
terrain of western Idaho. Humidity will stay low and the winds and
dryness will increase fire danger.
LONG TERM...Friday through Tuesday...Model guidance remains in
close agreement with an embedded shortwave passage on Friday.
Good upper level support and sufficient moisture should allow for
thunderstorms development. Precipitable waters approaching 90-95
percentile would suggest these storms could produce measurable
rainfall across much of the area along with gusty winds.
Temperatures will drop about 10 degrees behind the system. Showers
may linger in the mountains on Saturday as the flow turns more
northwesterly, rather than southwesterly, which should help to
push some of the smoke and haze out of the area, and allow
temperatures through the weekend to get down to near normal. The
ensembles still have quite a bit of variation in solutions beyond
Sunday, but appears to be a bit more supportive of weak
troughiness and cooler temperatures for early next week, rather
than a return to a strong ridge.
ID...Red Flag Warning from noon to 9 PM MDT Wednesday IDZ402-403.
PREV SHORT TERM...LC
PREV LONG TERM....JDS
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
655 PM CDT Tue Sep 7 2021
.DISCUSSION...(This evening through Tuesday)
Issued at 242 PM CDT Tue Sep 7 2021
Quiet weather continues this week. The cold front has pushed well
south of the area, and the entire area is seeing gusty north
winds in its wake. Skies remain clear aside from some haze from
the high level smoke just behind the front. Fortunately, satellite
analysis and the HRRR smoke model indicate that clearer air will
move in from the north by this evening.
Tonight, decreasing winds and relatively dry air will promote
efficient radiative cooling. In fact, some guidance takes the
typically cold portions of the area (Valley/Dawson counties) into
the upper 40s. This would make tonight the coolest night in quite
some time. Ord Airport has actually not been in the 40s since
There is high confidence that the rest of the workweek will
remain dry and warm. In fact, none of the 51 EPS ensemble members
produce any QPF for the area through Friday. Temperatures will
also remain above-normal as the western ridge slowly translates
eastward. Tomorrow and Thursday will be in the 80s for most, with
temperatures likely reaching the 90s in many spots by Friday as
the upper ridge centers over the area.
A shortwave will flatten out the ridge on Saturday and push a
cold front through the area. Exact model solutions vary, but it
appears this will bring at least a low chance for a few showers
and thunderstorms to portions of Nebraska Saturday night. This
will also knock temperatures back into the 70s and 80s for Sunday.
A second trough then pushes through the central/northern Plains
during the Sunday-Monday timeframe, bringing slightly better
chances for showers/storms for the beginning of next week.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 643 PM CDT Tue Sep 7 2021
VFR conditions will continue throughout the TAF valid period with
clear to mostly clear skies. The wind will be fairly light tonight
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
945 PM CDT Tue Sep 7 2021
02Z surface analysis showed a cold front extending from west
central OK, to extreme southeast KS and southern MO. Storms
developed rapidly along the front late this afternoon, aided by
dewpoints around 70F, and afternoon highs in the lower 90s.
This front remains on track for passage through the Midsouth on
Wednesday. Moisture pooling near the front (expected surface
dewpoints near 65F and 925mb dewpoints near 18C) will result in a
narrow strip of higher precipitable water values, near 1.8 inches
in the vicinity of the front. Modest mixed layer instability, at
or below 500 J/KG CAPE is progged by the HRRR north of I-40 during
the morning, and a little north of 1000 J/KG over north MS
Wednesday afternoon. NBM hourly precip-probability index appeared
underdone, but higher than earlier today. For those areas that do
see rain Wednesday, it will be sufficiently brief that measuring
more than a trace may be a challenge.
Forecast remains on track at this time, following minor adjustments.
.PREV DISCUSSION... /issued 621 PM CDT Tue Sep 7 2021/
Updated to include 00Z Aviation Discussion.
PREV DISCUSSION... /issued 251 PM CDT Tue Sep 7 2021/
Northwest flow aloft continues across the Mid-South downstream of
the anomalous ridge over the Intermountain West. This ridge is
quite strong with 500 mb geopotential heights among max
climatological values across NV/UT. Meanwhile, a fairly strong
trough is digging over the Great Lakes leading to a +PNA synoptic
pattern. We tend to see less in the way of precipitation during
this pattern with little in the way to temperature variability.
Precipitable water is near 0.6" across the Mid-South which is
below the 10% percentile for early September. This is allowing
dewpoints to fall into the mid/upper 50s, and will result in a
terrific evening across the region.
In the near-term, the trough digging across the Great lakes will
send a weak cold front through the Mid-South tomorrow. Low-level
moisture return ahead of this system will be scant, but we do
anticipate an uptick in column moisture along/ahead of the cold
front with a band of PWATs near 1.75". Instability appears pretty
mediocre with MUCAPE in the 500 J/kg range for most of the area.
There is an increase in instability across north MS during the
afternoon and the GFS/NAM both try to erode the cap by 21z as the
boundary approaches Tupelo. Some of the CAMs are hinting the
potential for a thin, broken line of weak convection across
portions of west TN and northeast MS. Will carry 20 PoPs to
account for this.
The western ridge shifts a bit eastward over the Southern Rockies
by the end of the week, finally breaking down late in the
weekend and allowing the westerlies to sink farther south across
the CONUS. However, the dry, post-frontal air mass will drop PWATs
back below 0.75" Thursday, with little increase through Saturday.
Dry and warm conditions will prevail during this time with
afternoon temperatures in the 80s (with some 90s over the weekend)
and lows in the 50s and 60s.
The ridge holds a tenuous grip on the Mid-South weather through
early next week, but the latest guidance indicates a trough
swinging through the area around midweek. This may be our next
notable chance for showers and thunderstorms across the region.
Patchy fog may produce temporary MVFR conditions at TUP between
08/08-12Z. Otherwise, VFR conditions expected to prevail at TAF
sites through the period. A cold front will move through the area
on Wednesday with light winds increasing to NW winds between 7-11
kts with a few higher gusts. VCTS also possible late Wednesday
morning at MKL and Wednesday afternoon at TUP.
Area Forecast Discussion
National Weather Service Pueblo CO
248 PM MDT Tue Sep 7 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 247 PM MDT Tue Sep 7 2021
Hazy and very warm conditions were noted over the region at 2 pm.
Temperatures were primarily in the lower 90s across most of the
plains with 80s in the valleys. Skies were clear (of clouds) and
hazy/smoky skies were noted over most locations.
Rest of Today and into Tonight...
Main concern will be haze/smoke. Several runs of the HRRR smoke
forecast indicate the worst of the smoke along the I-25 corridor and
the mountains will will occur this afternoon and into the early
evening, with the smoke decreasing with time thereafter.
Although the front has gone by, it remains very dry and no precip is
anticipated through tonight. breezy winds this afternoon over parts
of the region will decrease, except in the San Luis valley where
easterlies will push over the southern mtns, causing breezy
conditions in the valley this evening.
Lows tonight will be in the 50s plains and 40s valleys.
Smoke will increase once again although it is not anticipated to be
as dense as this afternoon. Temperatures tomorrow are expected to
nearly identical to todays max temps. It will also remain dry.
Likewise, expect highs on the plains to be in the upper 80s across
the divides (Palmer and Raton), with generally mid 90s across the
lower Ark Rvr valley. Valleys will be in the 80. /Hodanish
.LONG TERM...(Wednesday night through Tuesday)
Issued at 247 PM MDT Tue Sep 7 2021
Thursday - Friday... The start of the long term period is expected
to bring a torrid pattern to the area, especially over the eastern
plains. A large ridge/high pressure will continue to crawl its way
eastward Thursday through Friday. This large high pressure will
advect dry low to mid level air into the region throughout these
couple of days. Given the synoptically sinking air directly over the
area and the dry air being pushed into the region, precipitation
chances will be negligible. The main impacts from this pattern will
be the increase in temperatures, especially Friday, when the ridge
center/axis will be sitting directly over Colorado. High
temperatures will easily be near or above record values Thursday and
Friday, with the best potential for this on Friday.
Saturday - Tuesday... Heading further into the long term period, the
GEFS and EPS ensemble models are good agreement about the evolution
of the pattern over the next several days. Saturday will bring the
first reprieve from the hot temperatures. A short wave trough will
pass just to the north of Colorado. This trough will transition
winds aloft to become more westerly and bring better forcing aloft.
The trough will also bring a modest increase to low to mid level
moisture over the region. With the increased synoptic forcing,
orographic lifting, and moisture present, precipitation chances will
increase over the mountains. Out over the plains, a weak cold front
will drop southward as the short wave treks eastward. This will drop
temperatures down away from record values, but still above average.
Sunday another trough will begin materializing to the north. The
wave will have limited impacts on Sunday though, with a slight
decrease in moisture behind Saturday`s short wave and stronger
forcing staying further to the north. Isolated precipitation will be
possible over the central part of the Continental Divide as winds
aloft are still westerly and focused into the mountains. Diving into
Monday, the aforementioned trough from Sunday will begin digging
southward over the central plains. A stronger cold front is expected
to drop southward in response to this, and will bring cooler
temperatures again. Moisture will also slightly increase behind the
cold front, and given the easterly winds behind it, upsloping along
the eastern mountains may produce precipitation during the
afternoon. During the last day of the long term period, Tuesday, a
weak upper level ridge will push eastward over the region, before
beginning to fatten out. Drier air will be advected in with this
ridge and precipitation chances will drop as compared to the past
few previous days.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 247 PM MDT Tue Sep 7 2021
Some smoke and haze will be an issue at the taf sites this period.
The densest smoke/haze is expected to be this afternoon with it
decreasing somewhat this evening into tonight, with the smoke
increasing somewhat once again tomorrow. This may cause visibility
to down to 5-6sm at times at the taf sites. Otherwise no other
sensible weather is anticipated.
At KALS, breezy east winds are anticipated this evening. Otherwise
expect diurnal flow the next 24 hours.
Area Forecast Discussion
National Weather Service Riverton WY
550 PM MDT Tue Sep 7 2021
.SHORT TERM...(This Afternoon through Wednesday Night)
Issued at 242 PM MDT Tue Sep 7 2021
Northwest flow aloft over the region this afternoon as an upper-
level ridge sets up shop in the Great Basin. Cirrus clouds rotating
around the periphery of the ridge have been drifting across the
forecast area. Otherwise, wildfire smoke has caused reductions to
visibility at times as it settles into the valleys and basins
without much wind to mix the lower atmosphere. This trend continues
overnight as northwest flow persists. Another night of good
radiational cooling, so minor adjustments made for low temperatures
and relative humidity in the western valleys and basins.
Ridge axis reaches the western Wyoming border late Wednesday. Cirrus
cloud cover dissipates through the day leaving another mostly clear
sky. Daytime highs inch upward Wednesday as 700mb temperatures climb
toward +15C. Readings 5F to 10F above normal will be widespread
across the entire forecast area. There will be little wind Wednesday
with the ridge in place. Smoke will continue to pose a problem with
HRRR vertically integrated smoke forecasts showing smoke from
central Idaho wildfires filtering into the state Wednesday and
Wednesday night. Again made adjustments to low temperatures and
overnight relative humidity in the western valleys and basins.
.LONG TERM...(Thursday through Tuesday)
Issued at 358 PM MDT Tue Sep 7 2021
The beginning of the extended forecast period will continue with
near record warm temperatures. Thursday may see the latest 90+
degree temperatures on record for some areas. Widespread 90s across
areas east of the Divide with upper 80s across the lower elevations
elsewhere. A trough across the Pacific NW will begin to break down
the ridge over the next few days and also increase winds across the
region as the gradient tightens. The big concern with this will be
increasing the fire weather concerns Thursday and even more so
Friday. Thursday, the RH will be the slam dunk with very dry air
still present ahead of the impending system, but the wind will be
marginal as the trough is still progged to remain off the Pacific
Coast into Friday morning. That being said, winds will still be
gusty enough to potentially warrant fire weather highlights across
prone areas. Friday will be the opposite story, with winds being the
slam dunk element and the RH being a bit more marginal. Nudged lower
on RH in the grids for Friday due to the gusty dry winds ahead of
the trough, which likely will drop RH lower than what the best guess
of the models is. So, Friday may see more widespread fire weather
highlights. Friday also will be quite warm, though not as warm as
A cold front will move through Friday night, dropping temperatures
and bringing some precipitation across the region. Gusty northwest
winds and increased dewpoints will occur with and behind the frontal
passage, but the exact timing is still uncertain as models are still
in some disagreement with this. Saturday, chances of precipitation
with and behind the front are possible across the region, but again
exact locations and timing of this are still uncertain at this
point in the forecast. Sunday, some precipiation is again possible
across the region as the unsettled pattern continues. More seasonal
temperatures and general northwest to westerly flow will dominate the
remainder of the forecast period. Some isolated precipitation will
remain possible as shortwaves in the flow could impact the region.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 550 PM MDT Tue Sep 7 2021
Other than MVFR visibility due to wildfire smoke at a few terminals,
all locations will be VFR through the forecast period with high
pressure in control. This will limit wind with 10 kts or less at all
sites through 00Z/Thursday.
Issued AT 242 PM MDT Tue Sep 7 2021
A ridge of high pressure in the Great Basin dominates the regional
weather picture through Thursday. Temperatures gradually warm the
next few days, peaking Thursday with record or near-record warmth.
Lower elevations east of the Continental Divide will see readings in
the 90s and it is possible any records set could be the warmest seen
that late in the summer. To the west, seasonal daytime highs average
70 to 75. Expect highs Thursday to be 10 to 15F warmer than that.
Gusty wind does not appear to be much of an issue through
Thursday with the high pressure in control. Other than some high
clouds and smoke from western US wildfires, there will be little
cloud cover through Thursday.
The ridge begins to breakdown Friday and moisture returns to western
Wyoming in southwest flow aloft. This will lead to at least isolated
showers and thunderstorms across western Wyoming. However, a dry
lower atmosphere may take a bit to moisten, so these showers and
storms may not provide much rainfall. Associated cloud cover and
cooler temperatures aloft combine to help cool the far west several
degrees. The story may be different across southwest and central
Wyoming. Temperatures, while a tad cooler, are likely to remain well
above normal for this time of year. The favorable southwest flow
aloft will lead to increasing wind of 15 to 30 mph, particularly
across the High Desert District and central Wyoming. Given the low
relative humidity, Friday is a prime candidate for elevated to
critical fire weather conditions. Temperatures trend closer to
seasonal averages for Saturday with a slight chance of showers and
thunderstorms regionwide. The gusty wind and slightly above normal
temperatures may return for Sunday.