Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/01/21
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1034 PM EDT Tue Aug 31 2021
.SYNOPSIS...
A comfortable night expected across the region under variable
cloudiness as weak high pressure comes across upstate New York.
However, the remnants of Ida across Tennessee and Kentucky are
forecast to approach Wednesday into Wednesday night with a
period of rainfall, especially south of the Adirondacks. The wet
weather is expected to end during Thursday as a brisk northerly
wind evolves.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 1030 pm, with this forecast update, PoPs were tweaked in
the 09-15Z timeframe to allow for a faster increase over the
southern tier of counties based on the latest couple of runs of
the HRRR/NAM3. It does appear that Fgen will bring in precip by
12Z if not a bit earlier. Also increased cloud cover once again
based on latest obs showing thickening cirrus. Temps have fallen
off quickly over the North Country where clouds are thinner, so
we adjusted the temps in the near term as well. These should
stabilize as the clouds thicken.
Previous discussion...
As of 4 pm, diurnally driven CU/SC deck seen in the GOES
imagery was under a thin and opaque CI/CS. As the loss of
daytime heating occurs, so will the decrease in CU/SC but the
CI/CS will likely linger across southern areas. There will be an
increasing trend from south to north overnight as combination
of Ida and ongoing convection along the frontal zone near I80
begins to advect northward. Overnight lows will be a challenge
as portions of the Dacks may be a bit cool with mid-upr 40s to
lower 60s for the mid-Hudson Valley and southern Litchfield
County.
Looking at the latest HRRR, the chance for rainfall increases a
bit toward the southern zones near sunrise as mid-upr flow
becomes increasing confluent across these areas.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
.A Flash Flood Watch expanded to include northern Berkshire
County and remains in effect for Greene, Columbia, Ulster,
Dutchess, Litchfield and southern Berkshire counties from
Wednesday afternoon through Thursday afternoon...
Extensive collaboration today between neighboring offices and
national centers as we closely watch the approach and potential
impacts from Ida. 12Z NCEP Model Suite and international
guidance have trended northward with expected FGEN, upper jet
dynamics and expected QPF. Rain is expected to increase from
south to north as the combination of increase interaction with
frontal boundary and isentropic lift gets underway. The rain
shield will likely have a sharp cut-off where portions of the
Dacks may remain mainly dry from this event.
Cross sections depict a rather impressive FGEN band(s) may
develop and impact the southern 1/2 or 1/3rd of the region late
Wednesday into Wednesday night. Local research from colder
season events, suggest rainfall rates could be rather
significant and a layer of negative EPV seen in the cross
sections south of Albany could aid in precipitation efficiency.
Due to the northward shift, and per coordination, we expanded
the flash flood watch to include northern Berkshire County.
The other concern could also be the wind gust potential,
especially across the terrain. Latest 18Z run of the HRRR and
NAM3km surface wind gust forecast suggests values of 30-40kts
across portions of Ulster, Dutchess and Litchfield Counties. But
a closer look at forecast point soundings, boundary layer may
remain just stable enough to limit mixing potential. Regardless,
we will make a mention in the HWO given the hazard of wet soil
and any higher wind gust(s) could topple trees.
The rain should quickly exit to the east of the CWA shortly
after 12Z Thursday. Thereafter, a brisk northerly flow of drier
and cooler air mass advects into the region. H850 temperatures
drop back into the single digits as mixing layer heights climb
to aid with close to 20kt gusts...especially into the Hudson
River Valley locations.
High temperatures Wednesday will only reach the mid-60s to mid-
70s with lows Wednesday night in the upper 40s to near 60. Highs
Thursday will range from the lower 60s in some higher terrain
areas to the lower 70s in some valleys. Lows Thursday night in
the upper 40s to mid-50s.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
As the remnant low from what was once Ida lifts across Atlantic
Canada, a large closed off upper level trough will be over northern
New England and will be slowly moving towards the Gulf of St.
Lawrence for Thursday night through Saturday. Although this closed
low will be far enough to the northeast to avoid any rainfall for
our area, its cyclonic flow will influence the area with a cool,
northerly flow. The lower heights will keep temps aloft rather low
as well, which will keep daytime temps in the mid 60s to mid 70s
across the area. Overnight lows will generally be in the 50s,
although some upper 40s are possible for the highest terrain on
Thursday and Friday nights. While it should be dry, there will be
some diurnal cumulus that forms thanks to chilly temps aloft.
The closed low will move away for Saturday night into Sunday,
allowing the flow aloft to flatten out and temps aloft to rise.
However, another upper level disturbance north of the Great Lakes
will begin approaching the area and this may allow for some showers
and possibly a thunderstorm for late Saturday night into Sunday.
Best chance may wind up being north/west of the Capital Region,
especially during the diurnal favored afternoon hours on Sunday.
Temps should be slightly milder for Sunday, with highs mainly in the
lower to middle 70s across the area. Dewpoints may be creeping back
up into the 60s by late Sunday as well.
As the upper level disturbance slides across southern Canada, will
keep slight to low CHC POPs across the area for Monday into Tuesday,
especially during the daytime hours. Any precip looks fairly
scattered in coverage and mainly brief in duration. Temps will
remain seasonable, with valley temps still reaching into the mid 70s
for daytime highs.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
High clouds will thicken and gradually lower tonight as upper
level moisture associated with the remnants of TC Ida
approaches. Clouds should be relatively less thick at KGFL which
will allow a window for some radiational fog/mist to develop,
especially after 06Z (but possibly sooner). VFR conditions
should prevail otherwise, but a few high-based showers will be
possible at KPOU/KPSF late tonight toward sunrise Wednesday.
Flight conditions may deteriorate fairly quickly at KPOU as a
rain associated with tropical moisture and a frontal circulation
spreads in. Brought in MVFR cigs/vsby at 14Z and kept levels
there through the day, but would not be surprised if some brief
IFR conditions occurred depending on where the heaviest rain
bands set up. Conditions should fall to MVFR at KPSF later in
the afternoon as the front inches northward, and currently
expect KALB to remain VFR through the TAF period with the lower
cigs/vsbys staying just south. Rain is expected to remain south
of KGFL through the TAF period. Heaviest rainfall and worst
flight conditions are still expected just after the 00Z TAF
cycle.
Winds will be light and variable, becoming north to
northeasterly around 5 kt Wednesday (increasing to around 10 kt
late in the period at KPOU).
Outlook...
Wednesday Night: High Operational Impact. Chance of RA.
Thursday: Moderate Operational Impact. Chance of RA.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Moderate Operational Impact. Chance of SHRA.
&&
.FIRE WEATHER...
Mainly dry, seasonable and less humid conditions are expected
across the region through tonight under a partly to mostly
cloudy sky. Rain associated with Ida will brush portions of the
region Wednesday into Thursday with a period of moderate to
heavy rain likely for areas south and east of Albany. Drier and
fall-like weather then moves in to end the week.
RH values rebound to 90 to 100 percent tonight. RH values only
lower to 60 to 80 percent on Wednesday.
Wind will be out of the west 7-14 mph with some higher gusts
possible through this evening, then become variable at 7 mph or
less tonight through Wednesday.
&&
.HYDROLOGY...
A comfortable night expected across the region under
variable cloudiness as weak high pressure comes across upstate New
York. However, the remnants of Ida across Tennessee and Kentucky
are forecast to approach Wednesday into Wednesday night with a
period of rainfall, especially south of the Adirondacks. The wet
weather is expected to end during Thursday as a brisk northerly wind
evolves.
A Flash Flood Watch was extended to include northern Berkshire
County and remains in effect for Ulster, Dutchess and
Litchfield counties and has been expanded to include Greene,
Columbia and southern Berkshire counties. Storm total rainfall
of 2 to 4 inches in these areas could result in flash flooding.
Some river rises are expected with some possible rising to
flood stage, as latest NERFC highlights significant river
flooding possible for Ulster, Dutchess and Litchfield Counties.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...Flash Flood Watch from Wednesday afternoon through Thursday
afternoon for CTZ001-013.
NY...Flash Flood Watch from Wednesday afternoon through Thursday
afternoon for NYZ058>061-063>066.
MA...Flash Flood Watch from Wednesday afternoon through Thursday
afternoon for MAZ001-025.
VT...None.
&&
$$
SYNOPSIS...BGM
NEAR TERM...BGM/Thompson
SHORT TERM...BGM
LONG TERM...Frugis
AVIATION...Thompson
FIRE WEATHER...BGM/Rathbun
HYDROLOGY...BGM/Rathbun
Area Forecast Discussion
National Weather Service La Crosse WI
1040 PM CDT Tue Aug 31 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 236 PM CDT Tue Aug 31 2021
Early this afternoon a shortwave trough was passing across
eastern Iowa with upstream ridging developing across the northern
plains. Most of the associated showers have remained just south of
the local area, although some thicker mid/high clouds were
impacting northeast Iowa into southwest Wisconsin with A few
showers/sprinkles possible through the afternoon. As the wave
continues to pass to the southeast, the clouds will decrease late
this afternoon with mostly clear skies heading into tonight.
Tranquil weather will continue into Wednesday as mid-level ridging
gradually builds eastward, while Canadian high pressure centered
to the northeast will advect seasonably dry air across the region.
Some patchy fog could develop once again tonight in favored
valley/low-lying areas. Little change in thermal fields is
expected through Wednesday with lows tonight mainly in the upper
40s and 50s and seasonable highs Wednesday in the 70s to low 80s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 236 PM CDT Tue Aug 31 2021
The next chance for some rain continues to be centered on
Thursday night into Friday. The upper level ridge axis will be
retreating off to the east allowing a short wave trough to come
out of the Desert Southwest and move across the region. As it
does, it looks to start getting ingested into a large upper level
low moving across southern Canada, that some of the models are
suggesting could cause the wave to start breaking apart and
loosing energy. There should still be enough left of the wave to
produce at least some weak pv advection in the 500-300 mb layer
late Thursday night into Friday morning, with the better forcing
going off to the north. This same weakening trend is evident in
the low levels as a weak area of low pressure along the incoming
cold front looks to dissipate as it approaches the area early
Friday morning. However, before it does, there is a decent signal
that the activity could produce some locally heavy rains. The
instability looks to very low, so most of the activity should just
be showers, but there is a good low level moisture transport feed
into the region ahead of the short wave trough. Precipitable
water amounts should increase into the 1.5 to 1.75 inch range,
with the 31.00Z NAEFS indicates is close to 2 standard deviations
above normal. With warm cloud depths of 4 to 4.5 km, would expect
the showers to be efficient rainfall producers. Fortunately, this
system looks to be progressive and with the line coming in
oriented north/south the potential for training looks to be rather
low, so would not expect this to be much of a flash flooding
threat.
Once this system clears out of the region, the weather through
the upcoming weekend into early next week looks to be rather
tranquil. A couple of small chances for some rain with passing
systems both Sunday and Monday afternoon. Friday looks to be
coolest day with highs mainly in the 60s with seasonable highs
mainly in the 70s otherwise. And as a sure sign that fall in
approaching, overnight lows look to consistently drop into the 40s
and 50s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1040 PM CDT Tue Aug 31 2021
Cigs: generally skc/sct conditions through the period. Some
potential for a few hour window of bkn002 at KLSE, centered around
12z, in response to fog developing in the river valley. This outcome
is highly dependent on the low level wind field...with some meso
models suggesting they will be too high, while the RAP is trending a
bit lighter (favoring low cigs). More on that below...
WX/vsby: another clear, light sfc wind night will promote fog in the
river valleys. Winds just off the sfc though increase to 10+ kts by
300 ft or so in the NAM/HRRR soundings, holding there through the
night. This generally prevents any fog spreading off the river and
onto the airport. That said, trends over the past few hours in the
RAP is a decrease in these winds overnight...suggesting a greater
likelihood of some vsby impacts and associated low cigs. For now,
going to lean the forecast toward the low cigs rather than lower
vsbys - but as always in these scenarios - which watch trends closely
and update as needed.
Winds: light easterly through the period, getting a bit more
southeast on Thu.
&&
.HYDROLOGY...
Issued at 236 PM CDT Tue Aug 31 2021
The flood waters continue to slowly recede with water levels
having gone down enough to drop the warnings along the Turkey
River. Warnings remain in place along portions of the Black and
Yellow Rivers. See the latest flood statements for details.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...JM
LONG TERM...04
AVIATION...Rieck
HYDROLOGY...04
Area Forecast Discussion
National Weather Service Boise ID
830 PM MDT Tue Aug 31 2021
.DISCUSSION...Upper trough passing by to our north has cleared
smoke out of the northwest half of our CWA. The smoke, from
several large wildfires fires in eastern California, still covers
the southeast corner of Oregon, and Idaho south of Boise-Salmon.
According to the HRRR smoke model, northwest winds will clear the
near-surface smoke out of all of southwest Idaho overnight, but
will bring lesser amounts in from the northwest Wednesday.
Meanwhile, smoke aloft is forecast continue into Wednesday except
in northern-most areas. Northwesterly flow at the surface and
aloft should keep the denser California smoke away through Friday,
but southwesterly flow after that may bring it back into at least
our southern areas. Other than the smoke, we see another clear,
cool night as the upper trough passes by, then similar temps to
today on Wednesday and Thursday before warming Friday and
Saturday. Current forecast has this so no updates. As for our next
rain we see no realistic chance through at least next Wednesday
when GFS brings a weak Pacific trough inland. But even that looks
doubtful as ECMWF maintains a dry upper ridge through the end of
next week.
&&
.AVIATION...Mainly VFR. Areas of MVFR in the Magic Valley due to
wildfire smoke. Smoke reducing visibility aloft and in the mountains
south of a KREO-KBOI-KSNT line. Surface winds: variable 10 kt or
less overnight. Winds aloft at 10kft MSL: W to SW 10-20 kt.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Thursday night...An upper trough
along the WA/Canada border will track eastward on Wednesday while
a weaker trailing low will swing through the Intermountain NW on
Thursday. Neither of these systems will bring a chance for
precipitation but they will keep temperatures slightly below
normal through Thursday. Mid-upper level flow will act to confine
the smoke across southern portions generally south of a Burns-
Ontario-Stanley line.
LONG TERM...Friday through Tuesday...Zonal to southwest flow
aloft will develop Friday through Sunday associated with upper
level ridging over the Desert Southwest and troughing across
Canada. Temperatures on Friday will be 3-5 degrees below normal
behind a departing upper trough, then rebound to several degrees
above normal Saturday and Sunday. Smoke from wildfires in
California and Oregon may be transported into our area under this
flow pattern. The upper ridge will amplify Monday and Tuesday
across the Great Basin, with the flow aloft becoming northwest and
bringing a couple degrees of cooling. Dry conditions will continue
through the period with breezy afternoon winds.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
www.weather.gov/Boise
www.facebook.com/NWSBoise
www.twitter.com/NWSBoise
DISCUSSION...LC
AVIATION.....SH
PREV SHORT TERM...DG
PREV LONG TERM....ST
Area Forecast Discussion
National Weather Service Denver/Boulder CO
732 PM MDT Tue Aug 31 2021
.UPDATE...
Issued at 707 PM MDT Tue Aug 31 2021
Updates were added to include surface smoke increasing in northern
counties such as Weld and Larimer through Wednesday morning.
Sustained winds and wind gusts were increased across the eastern
plains to include the potential of a boundary set up stretching
across the county warning area (CWA). Maximum temperatures in the
mountains were decrease to reflect the incoming moisture through
the late afternoon to evening.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 350 PM MDT Tue Aug 31 2021
Satellite pictures are showing some developing convective clouds
over the mountains, foothills and Palmer Ridge. Radar was showing
a couple of weak cells over far eastern Lincoln County.
Models have the upper ridge to push southeastward tonight and
Wednesday with increase southwesterly flow aloft by Wednesday
afternoon. There is weak upward vertical velocity progged for the
CWA in the synoptic scale tonight and Wednesday. Models bring in
some of the mid and upper level moisture into the CWA tonight. The
lower level moisture doesn`t get into the western CWA until
Wednesday afternoon. There is no low level moisture over the
plains tonight or Wednesday. Will bring pops into the western CWA
by Wednesday afternoon. QPF fields are not excited about
precipitation amounts. There is more west of the forecast area.
Concerning smoke, the HRRR model shows a decrease with the smoke
over the CWA on Wednesday. Will leave it out. For temperatures,
Wednesday`s highs look 2-5 C cooler than today`s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 229 PM MDT Tue Aug 31 2021
We`ll have the shortwave and deepest moisture coming over our area
Wednesday night. The timing isn`t great for strong convection, and
the moisture is accompanied by warming in the mid levels. Forecast
soundings for 00Z Thursday actually have an inversion around 500
mb. So while we`ll have 1-1.25 inches of precipitable water at the
peak, other factors such as the prospect for sustained strong
updrafts as well as mean winds around 15 knots do not favor heavy
rainfall. The greatest threat would likely be just a blob of
moderate to heavy rain that takes some time to move across a spot,
or a couple of shower bands that are close together in time, that
could produce a half inch to inch of rain in an hour or two. This
would more likely be decaying convection that formed in western
Colorado earlier in the day. This would still be a problem for
our new burn areas, but the flooding risk looks low otherwise.
We`ll still have fairly high PoPs for when this forcing moves
over. Another complication is that as the lift moves over the I-25
corridor, there will also be post-frontal winds that will likely
have a downslope component.
Thursday is looking a little drier, as the deep moisture will be
shifting east of our area. The EC and NAM are more aggressive
with this that the other models. If they`re right, there will be
quite a bit less convection on Thursday as CAPEs will only be a
few hundred J/kg over the mountains and the plains will be weakly
capped.
For Friday, it appears there`s another weak shortwave trough. Mid
level moisture is limited, but we will likely have more moisture
again over the plains from low level southerly flow. The steering
winds are still probably at least 15 knots, so the flash flood
threat will not be that great. There could also be some threat of
severe storms on the plains this day with CAPEs up to 1000 J/kg
and an adequate hodograph.
It will be drier and warmer for the weekend, though some lingering
moisture and convergence could produce diurnal Front Range storms
on Saturday. It could be quite hot and dry again for Sunday and
Monday. There`s decent agreement on a shortwave dropping over the
ridge into the northern plains about Tuesday that would bring some
cooling. Our model blend looks alright with all of this.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 525 PM MDT Tue Aug 31 2021
VFR conditions will persist through the TAF period at all
terminals. Tonight, a shortwave will bring wind gusts up to 21kts
to KDEN and KAPA through 07Z. Wildfire smoke will continue to
impact slant visibility aloft; although, it will begin to
decrease through Wednesday afternoon due to incoming showers.
Challenges within the forecast begin Wednesday afternoon as
incoming moisture arrives in the mountains but struggles to reach
the TAF sites until 0Z. Direction of sustained winds are also a
forecast challenge due to a boundary short-term models have placed
within the area of the TAF sites. Depending on the placement of
the boundary through Wednesday afternoon, sustained winds could
become northerly instead of southerly at KAPA and vice versa at
KDEN through early Thursday morning.
&&
.HYDROLOGY...
Issued at 350 PM MDT Tue Aug 31 2021
There will no threat of flash flooding tonight and Wednesday
morning. With increasing moisture over the mountains Wednesday
afternoon, the chance of showers and thunderstorms will increase
there. There will be a slight threat of flash flooding over the
burn areas during the late afternoon.
There will be an increased risk of heavy rainfall over the
mountains Wednesday evening as an upper level trough with better
moisture moves across the area. Rainfall rates of up to an inch
in an hour will be possible even though storms should be moving.
This will create a moderate flash flood risk for the new burn
areas, while the threat elsewhere will be low.
For Thursday and Friday, scattered storms are expected over the
mountains. They should have decent storm motions, but could
produce brief heavy rainfall and a low flash flood risk for the
burn areas. Drier weather is expected this weekend with little or
no thunderstorm activity.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...AD
SHORT TERM...RJK
LONG TERM....Gimmestad
AVIATION...AD
HYDROLOGY....RJK/Gimmestad
Area Forecast Discussion
National Weather Service Grand Forks ND
630 PM CDT Tue Aug 31 2021
.UPDATE...
Issued at 630 PM CDT Tue Aug 31 2021
There are just a few cumulus clouds left across the FA early this
evening. The setting sun is also showing a little bit of high
level smoke, which is much thicker over eastern Montana and
western South Dakota. The HRRR model shows this thicker smoke
pushing into the area tonight into Wednesday. Winds were also
pretty gusty over the western Dakotas, and that will also spread
into the FA Wednesday.
&&
.SHORT TERM...(This evening through Wednesday Night)
Issued at 305 PM CDT Tue Aug 31 2021
Minimal impacts in the short term with attention being primarily
in the long term wrt to storms and heavy rainfall potential.
With western high plains troughing developing overnight will see
southeasterly winds persist helping keep temps a bit warmer than
the past couple morning`s with lows in the mid and upper 50s. As
the pressure gradient tightens with the approach of the western
SFC trough winds will increase Wednesday with southeasterly gusts
at 25 to 35mph. Highs will be in around 80 with increasing upper
level clouds moving into the area in the late afternoon.
Models continue to key in on a lead shortwave ejecting NE in the
mean flow from SD into SE ND and as it does will see thunderstorm
chances increase late Wednesday fueled by an increasing low level
jet. If a complex does develop activity may lift northeast into
SE ND late in the evening or after midnight. If this occurs there
will be the possibility of marginally severe wind or hail
overnight.
.LONG TERM...(Thursday through Tuesday)
Issued at 305 PM CDT Tue Aug 31 2021
Moderate to Heavy Rain Chances...
Wednesday night through Friday morning a trough moves in from the
Pacific NW, with a quick moving shortwave ahead of the main system.
Monsoonal moisture is driven through the low to mid levels into the
northern Plains, with PW values approaching 1.25-1.75inches. Along
the front associated with the trough temperature/moisture advection
is strong across ensembles. Frontogenesis is relatively strong along
the front, with the potential for a deformation zone developing
allowing for the prolonged rain to continue past the front.
Cluster analysis shows higher confidence in the chances for heavier
rain, but lacks in the axis of formation of the precipitation. This
is caused by the timing and propagation of the system. Faster and
earlier passage doesn`t allow for further moisture/temperature
advection into the northern valley limiting precipitation amounts.
While a slower progression would allow for moisture to flow further
toward the International border, with higher instability. This
allows for higher amounts to spread across a majority of the region.
Current ensembles indicator the faster propagation, with higher rain
rates along I-94 points SE. At this time, chances for exceeding 0.5
inches across the area is 40-80%. High end scenario is exceeding
3.0 inches, which falls in around a 10-20% chance for areas south
and east of Fargo.
The Holiday Weekend...
Conditions turn cooler and drier through the weekend, with highs in
the mid 70s as a ridge builds west. Conditions remain dry through
the holiday before rain chances increase next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 630 PM CDT Tue Aug 31 2021
This set of TAFs still has minimal impacts. The main issue will
be increasing wind speeds Wednesday morning. The strongest winds
will be felt Wednesday afternoon. Left out any mention of
precipitation due to low confidence, but something is possible
around KDVL by late Wednesday afternoon.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Godon
SHORT TERM...JK
LONG TERM...Spender
AVIATION...Godon
Area Forecast Discussion
National Weather Service Goodland KS
540 PM MDT Tue Aug 31 2021
.SHORT TERM...(This evening through Thursday night)
Issued at 249 PM MDT Tue Aug 31 2021
Across the region this afternoon, skies are mainly sunny, albeit for
the high thin veil of smoke that has been draped over the area
today. A line of cumulus has formed on a boundary over portions of
Kit Carson/Cheyenne counties and extending back west of Limon. Temps
are currently in the 90s area-wide, albeit for extreme northwest
Yuma county where upper 80s are present. With a surface low/trough
meandering over the CO/KS border, winds are light for all except
eastern locales where southerly flow prevails.
For the remainder of the afternoon into this evening, the wx focus
remains on fire wx concerns with low RH readings over portions of
the area, and the threat for some thunderstorms to develop.
First off, with winds light not looking for any major fires to take
place, although we have monitored since spot fires have cropped off
over the past several days. For thunder chances, some activity is
getting going confined to south of the Interstate. The latest HRRR,
NamNest have been showing some differences to start...coverage and
so on for this activity, but the HRRR seems to be panning out
better, albeit an hour or so early. While there might be some pea-
sized hail and locally heavy downpours, the main threat looks to be
strong wind gusts from the high DCape values on the SPC analysis and
inverted-V soundings over the area. The activity is set to shift
eastward and dissipate around the 03z Wednesday timeframe. Have
opted for a 20 pop for isolated coverage this afternoon/evening,
thinning out as the evening progresses.
Despite the smoke thinning out afternoon sunshine some, it does not
seem to be mixing to the ground, so will leave out mention at this
time in the forecast tonight.
Going into Wednesday, the upper ridge that had been over the south
central portion of the country for the past several days, amplifies
over the Plains on Wednesday and eventually shifts east enough to
set up a SW flow aloft. At the surface, lee-side trough sets up over
the eastern Rockies, and with high pressure east, a tight southerly
gradient will ensue during the day. Gusts up to 30-40 mph are
possible. The combined surface/upper flow will give the region a dry
afternoon, allowing for fire wx concerns to crop up. Please refer to
the Fire Wx section below.
By Wednesday night on into Thursday night, precip chances on the
rises area-wide. The aforementioned lee-side trough begins a trek
eastward Wednesday night, in tandem with a shortwave. These will
allow for some rw/trw to form. Initially in the west but coverage
expands east going into Thursday as the trough shifts over the CWA
and stalls as a frontal boundary. This will be the focus for further
development. Some of the storms that do develop, mainly east, could
be strong to severe, prompting a Marginal Risk area from SPC.
For temps, highs on Wednesday still expected to remain above normal
in the mid to upper 90s. On Thursday, increased chances for
clouds/precip will have highs range only in the 80s, warmest areas
east and south. Overnight lows will range mainly in the 60s tonight
and Wednesday night. By Thursday night, mid 50s to mid 60s.
For heat indices, 90s on Wednesday with highest numbers east, 80s on
Thursday.
Please refer to the Climate section below for information on the
near record/record high temperature potential.
.LONG TERM...(Friday through Tuesday)
Issued at 242 PM MDT Tue Aug 31 2021
At the start of the extended period, forecast models show the CWA
beginning with west-southwesterly flow aloft being between an upper
air trough to the north and a subtropical ridge to the south. By
Saturday, the CWA`s flow aloft has turned westerly as the top of the
southern ridge moves over the CWA. On Sunday, the ECMWF shows the
upper air flow turning northwesterly as the front part of a ridge
over the Pacific Northwest moves over the CWA with a trough moving
over the Northern Plains/Great Lakes/New England regions. The ECMWF
more or less shows this pattern continuing into Monday and Tuesday
as well. While the GFS depicts this same pattern as the ECMWF for
Sunday through Tuesday, it also shows an upper air trough developing
over UT on Sunday evening that moves over southeastern CO on Monday
morning and continues southeast into TX by Tuesday. The situation
will be monitored in future runs as long term models show some
differences going into next week.
At the surface, the CWA looks to see chances for precipitation to
start the long term period with the remainder seeing relatively dry
conditions. The CWA sees sees chances for showers and thunderstorms
during the afternoon and evening hours of Friday ahead of a backdoor
cold front that is expected to move across the area. Saturday shows
chances for diurnally-driven precipitation for the southwestern half
of the CWA as models display a moist air mass moving in from the
south at 800 mb. As previously mentioned, Sunday through Tuesday
look to stay mostly dry with possible elevated fire weather concerns
seen on Monday for areas along and west of the CO border. Current
forecasted minimum RH values look to go as low as 16% in parts of
this area, but the limiting factor looks to be winds as they do not
look to meet criteria at this time. This will be monitored in case
conditions change. Also worth noting, models suggest another
possible backdoor cold front moving through the CWA on Tuesday. As
this is late in the extended period, timing of this possible front
remains uncertain should the pattern pan out.
The Tri-State area should see high temperatures on Friday in the low
to middle 80s followed by Saturday seeing high temperatures around
the 80 degree mark. Sunday`s highs expect to be in the middle to
upper 80s followed by Monday warming to the lower 90s. Tuesday`s
daytime highs return back to the lower 80s. Tri-State area overnight
lows for Friday, Saturday and, Monday look to stay between the
middle 50s to lower 60s. Overnight lows on Sunday stay in the upper
50s to lower 60s range with Tuesday night lows being in the lower to
middle 50s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 535 PM MDT Tue Aug 31 2021
VFR conditions are expected through the forecast period at KGLD.
Visibility may be slightly reduced to 6SM due to smoke in the
area. Winds become southerly overnight under 12kts. Winds remain
southerly on Wednesday, increasing to 14-18kts with gusts to 25kts
by 17Z.
At KMCK, expect a wind shift from east to southeast between 02Z
and 04Z as an outflow boundary moves through the region.
Widespread thunderstorms are not expected at this time. Winds
become easterly after midnight, turning to the southeast by mid-
morning. Winds increase tomorrow evening to 14-18kts gusting to
25kts.
&&
.FIRE WEATHER...
Issued at 249 PM MDT Tue Aug 31 2021
Today, Elevated to Near Critical fire weather conditions are
expected along and west of Highway 27 this afternoon. Humidity
values will reach criteria in the lower to mid teens, while winds
will stay below criteria.
On Wednesday, Near Critical fire weather conditions are expected
along and west of Highway 27 in the afternoon. Winds expected to
reach or exceed criteria(30-40 mph), while humidity values will only
drop into the upper teens to around 20 percent.
&&
.CLIMATE...
Issued at 249 PM MDT Tue Aug 31 2021
Here are the sites with potential to reach or break record highs for
Tuesday, August 31st:
Goodland KS 102F/1985+
Burlington CO 99F/1985
Yuma CO 101F/1948
(+) denotes multiple years for a record
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JN
LONG TERM...076
AVIATION...AW
FIRE WEATHER...JN
CLIMATE...JN
Area Forecast Discussion
National Weather Service Pendleton OR
847 PM PDT Tue Aug 31 2021
.UPDATE...A low pressure system over northern Washington is
forecast to drift into n Idaho overheard. A few showers were
associated with the low pressure but these are expected to remain
north of the region and the breezy winds from earlier are forecast
to lessen overnight. With the decreasing winds and mainly clear
skies this will allow for good radiational cooling and
temperatures are forecast to dip into the 40s with upper 20s and
30s across the higher elevations. Minor changes were done to sky
and temps and winds and now the present short term forecast
appears on track.
&&
.PREV DISCUSSION... /issued 440 PM PDT Tue Aug 31 2021/
SHORT TERM...Tonight through Thursday night...An upper trough
will continue to slowly move across the region tonight and
Wednesday. This will keep temperatures on the cool side with
breezy afternoon winds, especially along the Cascade gaps and
passes into the adjacent valleys to the east. However, there will
be less wind on Wednesday than today, and temperatures will be a
degree or two warmer than today. The deterministic models are in
good agreement with the short range ensembles such as the HREF,
SREF and HRRR with the movement of this trough. The trough will
linger a bit on Thursday and then exit to the east Thursday night
into Friday. Expecting mostly clear and cool nights with frost in
the higher mountain valley/meadow locations tonight and again
Wednesday night. A slow warming trend will continue into Thursday
and going into the extended forecast period. Lower elevation max
temperatures will climb into the mid 70s to lower 80s by Thursday
afternoon, and mid 60s to mid 70s in the mountains. Air Quality
Advisories/Alerts will remain in effect for Yakima County and
Deschutes county due to smoke from regional wildfires through at
least midday Wednesday. 88
LONG TERM...Friday through Tuesday...An upper ridge will build
over the region behind the departing upper trough on Friday. This
will cause a more pronounced warming trend to take place Friday
and Saturday according to the NBM guidance. The deterministic and
ensembles are still in good agreement with this pattern as it
evolves. Also, WPC Cluster Analysis shows not much variance each
day in the extended period, especially on day 6 and 7. Afternoon
maximum temperatures by Saturday will be in the lower to mid
80s...possibly approaching 90, in the lowest elevations and 70s to
lower 80s in the mountains. However, there will be a slight
chance of showers in the central WA Cascades and east slopes, as
the upper ridge transitions to a more west to northwest zonal flow
type pattern on Saturday through Sunday. However, precipitation
amounts are expected to be very light. There will be a slight cool
down in temperatures as well on Sunday and Monday. After that, a
stronger upper high pressure system is advertised, by both the
deterministic models and their ensembles, to develop by late
Monday into Tuesday, with another warming trend beginning on
Tuesday. This upper high pressure system may eventually have the
potential to bring the forecast area back up into the 90s next
week, but it is too far out into the future to have high
confidence in that. In any case, summer looks like it will hang on
into the first part of September, as is often the case in this
region. Regional wildfires will likely continue to cause smoke
issues during the extended period as well. 88
AVIATION...vfr conditions will persist at all taf sites for the
next 24 hours. However brief wind gusts between 20 to 25 kts are
possible at taf sites kdls and krdm and kykm until around 04z.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 40 72 44 77 / 0 0 0 0
ALW 45 75 48 80 / 0 0 0 0
PSC 47 76 50 81 / 0 0 0 0
YKM 40 75 46 80 / 0 0 0 0
HRI 44 76 47 81 / 0 0 0 0
ELN 44 75 46 79 / 0 0 0 0
RDM 32 73 38 75 / 0 0 0 0
LGD 42 73 42 75 / 0 0 0 0
GCD 38 79 41 80 / 0 0 0 0
DLS 48 79 54 84 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&
$$
SHORT TERM...97
LONG TERM....99
AVIATION...97
Area Forecast Discussion
National Weather Service Phoenix AZ
511 PM MST Tue Aug 31 2021
.UPDATE...Updated 00Z aviation discussion.
.SYNOPSIS...
Scattered to widespread showers and thunderstorms will occur today
over the entire region before mainly being confined to southwest
and south central Arizona tonight into Wednesday. Locally heavy
rainfall capable of producing flash flooding is expected, but
localized damaging wind gusts will also be possible. A Flash Flood
Watch is in effect through late tonight for southeast California
and Yuma and until late Wednesday night for the rest of southwest
and south central Arizona. A drying trend will begin on Thursday,
but lingering chances for isolated storms will remain over the
Arizona high terrain into the weekend. Well below normal
temperatures are expected through Thursday and warming back near
or just below normal by the weekend.
&&
.DISCUSSION...
Abundant moisture is being observed and analyzed across the region
this afternoon with deep southerly flow. A 19Z sounding in Yuma
sampled 2.1" PWATs and mesoanalysis shows most of the lower
deserts around 2" with 14-16 g/kg mean mixing ratios. This will
result in efficient rain producing showers and storms through
this afternoon and continuing through Wednesday. 1-2"/hr rain
rates will be common, with isolated higher rates in stronger
showers and storms. The 18Z sub-hourly HRRR is even suggesting the
potential for 3-4"/hr rates with this afternoon`s storms in parts
of southeast CA and southwest AZ. This will surely lead to rapid
runoff into creeks/streams, washes, and low-lying areas with the
potential for flooded roadways. One thing that is already evident
with ongoing storms is the tendency to redevelop and persist over
the same areas for extended periods. This will only added to the
flooding concerns and drive up localized rainfall amounts. This is
expected to be a common feature across the region through the
event with the deep southerly flow and enhanced dynamic forcing.
The same 19Z Yuma sounding also calculated over 2000 J/kg SBCAPE
and it has already been realized in the area with strong storms
having developed. There is a threat for wet microbursts through
the afternoon with the high moisture content, instability, and
DCAPE values over 900 J/kg. So, in addition to the flash flood
threat there is a marginal severe wind threat. The 12Z HREF has a
70% chance for wind speeds in excess of 35 mph and 10% chance for
speeds over 58 mph in Imperial County. With this strong of winds,
there will also be a threat for blowing dust and/or sand, which
could lead to reduced visibilities. The severe wind threat
decreases east of the Colorado river, but strong downdraft winds
will still be possible with any storms through this event.
Most active areas of showers and storms through the rest of the
afternoon are favored out in southeast CA and southwest AZ, as
well as in the northern AZ high terrain and southeast AZ, before
transitioning more to south-central AZ later this evening. 12Z
HREF is showing the greatest potential for heavy rain in Maricopa,
Pinal, and Gila counties Wednesday morning with 3 hr neighborhood
probabilities (for PMM) of greater than 1" of rain reaching
40-50% between 2 AM and 11 AM. Upslope regions and terrain
features are likely to experience the highest rainfall totals, but
there is still uncertainty in where bands of heavier rain will
align, especially over the lower desert locations like the Valley.
Based on the latest forecast from WPC and HREF QPF is expected to
increase quickly east of Phoenix. Most likely rainfall in Phoenix
continues to come down and is now only showing around 0.1-0.6"
(higher to the east), but again there is still a 10% chance
(based on NBM) some localized areas could receive 1.5-2" and there
is equally a 10% many areas receive no measurable rain. The
biggest concern Wednesday morning will be the potential for burn
scar flooding, especially the highly prone Telegraph burn scar.
Catastrophic flooding is certainly a possibility as the 12Z HREF
LPMM is suggesting the potential for QPF up to 4-6" in this area.
In coordination with WPC a moderate area for excessive rain was
introduced this morning to cover the areas of greatest concern.
.PREVIOUS DISCUSSION...
Much drier air aloft should spread over much of the area
Wednesday night into Thursday as PWATs fall to around 1.0-1.2" in
south central Arizona and even lower further west, likely ending
rain chances across the lower deserts by Thursday morning. Another
upper level trough is forecast to approach the California coast
late in the week, keeping our region mostly under southwesterly
flow aloft. Lingering boundary layer moisture should prevail over
the higher terrain of eastern Arizona Friday into the weekend
keeping at least slight chances for afternoon storms in the
forecast. Model ensembles are also starting to agree on another
round of monsoonal moisture and storm chances moving back into the
region late in the weekend into early next week.
&&
.AVIATION...Updated at 0011Z
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
There are multiple aviation weather concerns through the TAF period.
Latest radar imagery is showing an area of light-moderate
rain/showers moving into the Phoenix area at this hour. The
stratiform nature of the rain appears to be keeping TS well off to
the east of the terminals at this point, but an isolated TS cannot
be ruled out. The main impact from the rain early this evening will
be to lower CIGS at times, perhaps as low as BKN040 with lower SCT
layers at times in the heavier showers. Winds through the early
evening are expected to remain out of westerly direction, with some
gustiness at times. Latest High-res models are showing that -RA/-
SHRA will diminish somewhat after 03-04Z as the 1st batch of rain
moves off to the north, but confidence in the timing of this semi-
break is low-moderate at best.
A more substantial period of showers is anticipated to begin shortly
after midnight, then continue into the early/mid morning hours on
Wednesday. Chances for a sanguined period of CIGS aob 4k feet (with
lower SCT layers) are in the 30-40% range. An isolated TS cannot be
ruled out, but confidence is far too low to include TSRA/VCTS in any
of the TAFs at this point. Wind directions during this period are a
bit uncertain, but likely will favor a light southerly direction at
this point. Gradual improvement in the CIGS is expected during the
late morning/early afternoon hours on Wed as drier air moves into
the region from the west. Winds are expected to become westerly by
late afternoon as well. Wed evening will feature clearing skies
with a more typical diurnal easterly wind returning by mid/late
evening.
Southeast California/Southwest Arizona including KIPL and KBLH:
There are multiple aviation weather concerns through this evening.
Storms and showers over the region are expected to continue to
affect the KIPL area thru about 02-03Z and the KBLH area thru about
05-06Z. Direct storm impacts will include lightning, strong
downbursts, and temporarily reduced cigs and visibility. Drier air
moving in from the south will then bring clearing skies and end the
TS threat by late tonight. Dry conditions are then forecast for Wed
with just some SCT-BKN mid-level CIGS in the TAFs. Once the TS
activity ends, winds at KIPL will become mainly southeasterly and
southerly at KBLH thru the remainder of the TAF period.
&&
.FIRE WEATHER...
Thursday through Monday:
After wetting rains fall across much of the region on Tuesday and
Wednesday, drying conditions are expected from west to east on
Thursday to temporarily end rain chances for all but the eastern
Arizona high terrain. After mostly slight chances for isolated
showers and thunderstorms across the higher terrain on Friday and
Saturday afternoon, storm coverage should increase across the
higher terrain by Sunday or Monday. Outflows from these storms and
another potential weather disturbance from the east may trigger
storms over the lower deserts of south central Arizona on Sunday
and the entire region on Monday. Winds will generally follow
diurnal trends aside from stronger gusts in thunderstorm outflows.
Minimum Minimum RHs will remain above 25-30% for south central
Arizona, whereas southeast California and southwest Arizona may
briefly dip to 15-20% on Friday and Saturday. Maximum RH values
will recover into a 40-70% range for most locations each night.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flash Flood Watch through late Wednesday night for AZZ530-531-
533>563.
Flash Flood Watch through late tonight for AZZ532.
CA...Flash Flood Watch through late tonight for CAZ560>570.
&&
$$
DISCUSSION...Benedict
PREVIOUS DISCUSSION...Hopper/Kuhlman
AVIATION...Percha/AD
FIRE WEATHER...Hopper
Area Forecast Discussion
National Weather Service Reno NV
242 PM PDT Tue Aug 31 2021
.SYNOPSIS...
Breezy conditions on Wednesday bring lingering concerns for rapid
fire spread for portions of the Sierra and far western Nevada.
Lighter winds are on tap Thursday into early next week. Smoke and
poor air quality will continue to plague portions of northeast CA
and western NV. A gradual cooling trend is expected through
Thursday before temperatures gradually warm through the weekend.
&&
.DISCUSSION...
An upper low over the northwestern CONUS and southwestern Canada
will slowly move northeast into the central Canadian provinces
Wednesday-Thursday. A residual weak trough will remain over the West
late week before an upper ridge strengthens over California and
Nevada over the weekend into early next week.
After above average highs today (lows remain seasonably cool to
chilly), the residual trough will serve to keep temperatures
moderated to near average through Friday before they gradually
rise through Monday under the building ridge. Highs look to top
out around 4-8 degrees above average (valleys 80s to lower 90s)
early next week.
Winds through Wednesday along with smoke for the foreseeable
future continue to be the main concerns for northeast CA and
western NV. Details below...
* WINDS: Breezy southwest-west to continue into this evening with
gusts 25-35 mph, locally to 40 mph, in valley locations and up
to 50 mph over high ridges across northeast CA and far western
NV. Winds are lighter out in west-central NV at this time but
should pick up some for late afternoon and evening as the
pressure/thermal gradient maximizes. The breezy conditions will
cause lake chop, today in particular when advisories remain in
effect for some area lakes. Winds on Wednesday will be lighter
than today, more similar in speeds to what we saw on Monday with
gusts 20-30 mph, locally up to 35 mph in wind prone locations.
Lighter winds still are expected for Thursday as some cooling
across the region diminishes thermal gradients. Friday into
early next week, generally light winds are on tap.
* SMOKE: Based on what occurred last night and this morning along
with the latest HRRR smoke models, the places that look to be
hardest hit (longest duration, worst air quality) from Caldor
Fire smoke through early Thursday include areas near/south of
Highway 50 across western NV, and north of Alpine County
including Lake Tahoe for eastern CA. As happened this morning,
substantially degraded air quality looks to work its way into
the Reno-Sparks area again Wednesday morning and probably
Thursday morning as well, although afternoon westerly winds
should again clear the air for Wednesday afternoon and evening.
Downwind of the Dixie Fire, areas across portions of Lassen
and Plumas counties into northern Washoe County and east into
Pershing and northern Churchill counties look to be most
affected.
As we go into late week, flow in the smoke-bearing layer up to
around 700 mb go more southerly. While smoke modeling is not
yet available (only goes out to late Thursday morning), the
flow aloft along with lighter surface flow would suggest
worsening smoke and air quality for areas north of Lake Tahoe
and into the Reno-Sparks area as daytime mixing works smoke
aloft from the Caldor Fire down into valleys.
-Snyder
&&
.AVIATION...
Greatest concerns through Wednesday across northeast CA and western
NV continue to be gusty SW-W winds and the continued smoke and
haze. Wind gusts into this evening should peak 25-35 kts. Winds
at FL100-140 forecast to be sustained around 20-35 kts through
Wednesday with turbulence across and downwind of the Sierra. A
shear layer may also be present tonight and Wednesday morning
downwind of the Sierra as winds remain elevated aloft. Winds will
be slightly weaker for Wednesday, similar to yesterday`s speeds
with gusts 20-25 kts.
Smoke to continue to bring terrain obscuration and slantwise
visibility reductions to many areas. Based on HRRR smoke models,
the places that look to be hardest hit through Wednesday include
areas from KTVL-KMEV-KNFL with sub-minimum landing criteria likely
for large amounts of time for KTVL/KMEV. Also, as happened this
morning, substantially degraded VIS (MVFR at least) looks to work
its way into the KRNO area again Wednesday morning before the air
clears for the afternoon with westerly winds. Downwind of Dixie,
areas across portions of Lassen and Plumas Counties into northern
Washoe County and east toward KLOL and KWMC look to be most
affected.
-Snyder/Dawn
&&
.FIRE WEATHER...
* Red Flag Warnings continue through this evening for northeast CA
including the Dixie Fire, Tahoe Basin including the Caldor Fire,
and into northwest NV for gusty winds and low humidity.
* Gusty winds and low humidity will exacerbate ongoing fires and
increase the threat of significant fire growth for much of the
region. Please listen to all advice from local authorities,
especially if you are in the path of the Caldor and Dixie Fires.
* Red Flag Warnings remain in effect through Wednesday evening for
the Tahoe Basin (including the Caldor Fire), Sierra Front, and
northern Mono County.
* Poor overnight recoveries for mid slopes and ridges occurred
overnight and are expected again tonight.
Wind gusts are starting to surface across the region with observations
generally in the 25-30 mph range. This will continue through the
early evening with the strongest gust potential of up to 30-40 mph
through about 6-7pm this evening particularly along US 395/I-580
along the Sierra Front.
As a dry slot moves across the region, a very dry and unstable air
mass is currently overhead yielding an environment supportive of
plume dominated growth with a Haines index of 5-6 in place region
wide. Winds remained elevated in thermal belts and along ridgelines
overnight and similar conditions are anticipated tonight as well.
Winds will be a bit weaker Wednesday, similar to what was experienced
Monday with gusts 25-30 mph, locally to 35 mph in wind prone locations.
Unstable conditions will also prevail on Wednesday, which along
with the very receptive fuels means the high fire danger continues
through Wednesday. Fuentes/Dawn
&&
.REV Watches/Warnings/Advisories...
NV...Red Flag Warning until 11 PM PDT Wednesday for Lake Tahoe in
NVZ420-421.
Lake Wind Advisory until 9 PM PDT this evening NVZ003-004.
Red Flag Warning until 11 PM PDT this evening NVZ458.
CA...Red Flag Warning until 11 PM PDT Wednesday for Lake Tahoe in
CAZ272.
Lake Wind Advisory until 9 PM PDT this evening CAZ073.
Red Flag Warning until 11 PM PDT this evening CAZ270-271-278.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Springfield MO
702 PM CDT Tue Aug 31 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 215 PM CDT Tue Aug 31 2021
Remnants of convective complex were rapidly falling apart over
southern MO early this afternoon as it moved into less favorable
atmospheric conditions. Still could see a few showers/storms
develop along the outflow over southern MO this afternoon. CAMS
models develop some additional convection tonight, but are having
a difficult time with placement of convection. The HRRR seems too
far east, as the better instability and moisture should be over
our far western CWA late tonight. Will continue low end pops over
the western half of the CWA for now. Lows tonight should dip into
the mid 60s in the east and around 70 out west.
Upper ridge will then begin to build into the area on Wednesday
and should end the precipitation chances. Temperatures will range
from the mid 80s in the northeast to the mid 90s in the southwest.
The southwest corner of MO and the southeast KS counties may be
around 100 for the heat index on Wednesday.
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 215 PM CDT Tue Aug 31 2021
The upper level ridge axis will be from Texas into the western
great lakes on Thursday. Will see temperatures from the mid 80s in
the east to the low 90s out west and possibly some mid to upper
90s heat index values out west.
From Thursday night through Saturday, we`ll see a shortwave trough
push across the northern plains, upper Mississippi valley and into
the Great Lakes region which will flatten out the ridge and bring
a surface front into the area Friday night into Saturday. The
front will aid in scattered shower/thunderstorm development late
Friday into Saturday in the upcoming holiday weekend. High
pressure behind the front will slide to the east of the area on
Sunday with a return to southerly winds on Sunday night and
Monday.
Another shortwave will track southeast across the upper
Mississippi valley on Tuesday bringing another cold front into the
area with additional rain chances.
Less confidence in temperatures in the later periods with larger
variance in ensembles. Sticking with the NBM at this time which
continues to yield mid 80s to low 90s across the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 652 PM CDT Tue Aug 31 2021
KSGF/KJLN/KBBG tafs: Generally VFR for the period with two
possible brief exceptions. High based/sparse coverage
showers/thunderstorms may develop in the 10z-14z time frame over
parts of southwest Missouri in response to lift with a veering
low level jet/flow and elevated instability. Some light ground
fog/haze will also briefly be possible toward 12z in some low
terrain areas/lakes with weak low level winds/surface
(radiational) cooling. Otherwise, light northeast-east winds will
continue with a ridge of high pressure extending from the western
Great Lakes to the Ozarks.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
SHORT TERM...Lindenberg
LONG TERM...Lindenberg
AVIATION...DSA
Area Forecast Discussion
National Weather Service Topeka KS
548 PM CDT Tue Aug 31 2021
...AVIATION UPDATE...
.DISCUSSION...
Issued at 304 PM CDT Tue Aug 31 2021
Outflow from the early-day convection has pushed southwest into
south-central Kansas and southern Missouri as of 19Z. Modest lee
troughing was over the central and northern High Plains under better
westerlies still to the north. Weak surface high pressure and
easterly flow was over the upper Mississippi Valley with some areas
of stratus. Upstream water vapor imagery showing a large upper low
over southern British Columbia and another weaker wave off Baja with
several areas of convection in western Mexico.
As the old tropical system continues northeast out of the
southeastern states and the northwestern low nudges east, upper flow
locally become more northerly as surface winds back to a east-
northeast direction. Models continue to struggle on where the best
resulting isentropic lift will focus tonight with decent signals on
the 310 and 305 K surfaces, though most solutions have it in far
eastern Kansas into western Missouri and have increased precip
chances in the eastern counties. Instability also varies
considerably, though the mean would less than 1000 J/kg. Effective
shear also limited by weak overall flow and this combination should
keep any storms from being too strong. Can`t rule out some training
convection in this setup for some locally heavy amounts with PW
values around 1.5 inches. Any precip should weaken in the early
morning though another round can`t be completely ruled out Wednesday
night but ascent is weaker.
The western circulations earlier noted work east and northeast,
respectively, tonight into Thursday. A weak front is nudged into the
area Thursday night into Friday as very warm air aloft and quite
high and deep moisture advects in. PW values from the NAM and GFS
are near record values though ESAT values near not quite as
impressive but trending up. CAPE values get limited somewhat as a
result and the main impact from this front could be heavy rain with
the front becoming aligned with the upper flow Thursday night into
Friday along with some indications of another shortwave passing
Friday night. The Canadian low moves into the Great Lakes by late
Saturday and should help usher drier conditions in for the remainder
of the holiday weekend. Thursday looks to be warmest day of this
forecast with some locations returning to the mid 90s ahead of the
front. Labor Day may also be on the warm side as southwest winds
look to return ahead of another front in northwest flow Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday)
Issued at 548 PM CDT Tue Aug 31 2021
The RAP and NAM continue to show a narrow axis of isentropic
upglide near the terminals overnight. Forecast soundings indicate
a fair amount of elevated instability with some bulk shear, but
the CAMs are not that excited about coverage of storms and are hit
or miss with regards to the terminals. May include a VCTS in the
forecast and wait to see where the upglide sets up to be more
specific. An easterly low level wind is expected to advect a moist
boundary layer into central KS overnight. This should lead to some
MVFR stratus forming through the mid morning hours.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...65
AVIATION...Wolters
Area Forecast Discussion
National Weather Service Las Vegas NV
801 PM PDT Tue Aug 31 2021
.SYNOPSIS...Moisture from the remnants of Nora will lead to a risk
of heavy rain through Wednesday. A Flash Flood Watch is in effect
for parts of Clark and San Bernardino Counties and all of Mohave
County. Deep moisture exits to the east later this week for
decreasing chances for thunderstorms. However, that may be brief as
moisture and storm chances could return by the end of the holiday
weekend.
&&
.UPDATE...Scattered thunderstorms will continue through the evening
and into the overnight period mainly east of the I-15 corridor. Some
of the storms this evening over San Bernardino and Mohave counties
have been producing rainfall rates in excess of 2 inches per hour
indicating the ample moisture that remains in place, and no changes
have been made to the Flash Flood Watch that is currently in place.
The deeper moisture will begin to move farther east tomorrow
decreasing the heavy rain threat from west to east. Additionally,
the latest HRRR smoke model continues to show smoke from the Caldor
fire moving into Esmeralda county overnight and the weather grids
have been updated to reflect this. No other major changes to the
grids were needed this evening. &&
.PREV DISCUSSION...
109 PM PDT Tue Aug 31 2021
.SHORT TERM...through Thursday night. Multiple circulations evident
on satellite loop today, with at least two MCVs over our CWA and the
main upper low spinning just west of Baja. New convection has been a
little slow to develop, but the extra lift from the circulations
plus the eroding debris clouds will allow storms to pop this
afternoon, mainly near and east of a line from Morongo Valley to
Mount Charleston to Rachel. Instability should persist much of the
night, and there should be just enough shear to keep storms going
all night with a threat of pulse severe, but not long lived
organized severe. Flash flooding remains the biggest concern, as the
aforementioned instability and shear coexist with deep tropical
moisture (precipitable water of 1.5 inches as far north as Laughlin
and 1.8 inches at Lake Havasu City as of late morning). The areal
extent of the Flash Flood Watch looks good, but the timing may be in
question. As the upper low off of Baja slowly drifts inland
tomorrow, the deepest moisture should be redirected farther east,
possibly ending the flash flooding threat early. However, there is
not enough confidence in this to change the valid time of the Watch.
Will monitor and cancel early if needed. Once the flash flooding
risk is finally over Wednesday night (or perhaps earlier), Thursday
will see precip chances limited to the eastern half of Mohave County
and possibly the Spring Mountains. Temperatures will be below normal
today and Wednesday, especially in areas that see clouds and rain,
with a warming trend beginning Thursday as the moisture shifts east.
.LONG TERM...Friday through Tuesday.
Dry conditions are expected Friday and Saturday with weak
southwesterly flow in place across the area. Both the GFS and ECMWF
ensembles are showing high pressure rebuilding across the Four
Corners region by the end of the weekend. Southeasterly monsoonal
flow associated with this high will push higher PWAT levels into the
Colorado River Valley by Sunday afternoon, returning the chance of
thunderstorms to Mohave County. Moisture should spread further west
Monday and Tuesday, increasing thunderstorm chances across southern
Nevada and eastern California.
&&
.AVIATION...For McCarran...Increasing confidence that there will be
moderate impacts due to thunderstorms in or around the Las Vegas
Valley today. Best chances for thunderstorms impacting KLAS &
surrounding terminals will be between 22-01Z today. Vicinity showers
and thunderstorms will be possible thereafter as well, potentially
remaining through Wednesday morning. Potential impacts associated
with storms in and around the Las Vegas Valley include brief heavy
rainfall that could result in reduced visibility over the terminal,
gusty outflow winds, and lightning. Outside of thunderstorm
influences, winds should be favoring a southeast to southerly
direction around 8-10 knots with occasional gusts to around 15-20
knots through the afternoon. Winds will decrease overnight, becoming
light and variable. SCT to BKN aoa 10-12 kft this afternoon with BKN
aoa 7-8 Kft persisting overnight. There`s a non-zero chance that
ceilings could drop to around 5 Kft overnight/early tomorrow
morning.
For the rest of southern Nevada, northwest Arizona and southeast
California...Isolated to scattered thunderstorms are possible again
this afternoon, with better chances later tonight across
southeastern portions of our region, including in and around the
Colorado River Valley and potentially KDAG. High confidence on
storms impacting KIFP, KEED at some point tonight between 03-07Z
Wednesday. Low confidence on any storms impacting KDAG directly, but
vicinity thunderstorms maybe within 15 miles at times. Main concern
would be heavy rainfall reducing visibilities over the terminals,
outflow winds, and frequent lightning. SCT to BKN aoa 10-12 kft this
afternoon with BKN to OVC aoa 7-8 Kft persisting overnight for KIFP
& KEED. There`s a non-zero chance that ceilings could drop to around
5 Kft overnight/early tomorrow morning impacting KIFP & KEED.
Further northwest, expect FEW-SCT aoa 12 Kft with some occasional
breezy winds in the afternoon. That said, haze from distant wildfire
smoke will reduce slant range visibility at times, especially across
the Sierra and parts of the southern Great Basin. Not anticipating
smoke/haze to impact KBIH overnight tonight/early tomorrow morning
at this time.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Planz
SHORT TERM...Morgan
LONG TERM...Planz
AVIATION...Peters
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