Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/03/21
Area Forecast Discussion
National Weather Service Wichita KS
632 PM CDT Thu Sep 2 2021
.SHORT TERM...(This evening through Sunday night)
Issued at 313 PM CDT Thu Sep 2 2021
Bottom line up front: Periodic showers and thunderstorms, with
heavy rainfall possible tonight through Sat. Slightly cooler
temperatures for the holiday weekend.
Low level moisture transport continues to feed into the elevated
showers and thunderstorms, located across central KS. Slow movement
and training nature of the storms is leading to pockets of heavy
rainfall along I-70. As the afternoon progresses, expect this
initial area of showers to lift E-NE of the forecast area. The
concern will be if portions of central KS can recover enough for
additional showers and thunderstorms for this afternoon into this
evening, as a weak frontal boundary lingers across this area.
Think we will see additional showers develop for the remainder of
the afternoon hours, as most of central KS becomes uncapped to
surface based development. As the evening continues, areas just to
west of the forecast, across central KS, will eventually become
uncapped enough for additional shower/storm development, with this
convection moving back into central KS. Think the showers/storms
will become more widespread late this evening and overnight,
especially for areas north of highway 50, as the short range RAP
shows low level moisture transport increasing with the low level
jet, as the main synoptic front pushes into central KS. Think heavy
rainfall and localized flooding will be the main concern, given the
anomalous high precipitable water (PW) values of 180-190 percent of
normal moving into central KS. Cannot completely rule out a few
strong to marginally severe storms, given bulk shear values of 30-40
kts and modest instability, which could lead to some downburst winds
of 50-60 mph and dime to quarter size hail. Will have to keep an eye
on the flooding risk across central KS, as this area picked up over
an inch of rainfall this morning, on top of the 3 to 4 inches they
got last week. So I am concerned additional rainfall tonight may
cause areal flooding and flash flooding tonight. I considered a
flood watch for portions of central KS, but consensus with
neighboring offices was to hold off. So will pass this concern along
to the evening shift.
Position on the frontal boundary will be uncertain for Fri, as
convective outflow from tonights showers may push the front further
south. For now expect the frontal boundary to make slow progress
into southern KS on Friday. Think most of the forecast area will see
another round of periodic chances of showers/storms for Friday
afternoon thru Friday night, as another weak shortwave moves across
KS in the zonal flow. Placement of the heaviest rainfall is
uncertain, with CAM solutions all over the place on where the
heaviest rainfall will occur. For now will mention the potential for
heavy rainfall in the grids/zones/hazardous weather outlook, given
the high PW values expected to remain across KS. Think portions of
central and south central KS may see QPF amounts of 1 to 2 inches,
with pockets of 3 to 4 inches possible as well.
Position of the frontal boundary will continue to be uncertain for
Sat, as convection on Fri night, may push the effective frontal
boundary, further south into northern OK, or possibly linger it over
southern KS. For now, plan on keeping solid chance pops across
southern KS, until location of the front becomes more clear. If the
front should linger across southern KS, another chance of showers
/storms is possible for Sat afternoon/evening as well.
With the front pushing south for Sat night into Sun, Looks like a
shot of cooler air will move into most of the forecast area. This
will lead to a little taste of fall-like temperatures for central
KS, with max temps in the middle to upper 70s on Sat. Could see
quite a temperature gradient for Sat afternoon, if the frontal
boundary hangs up over southern KS, with max temperatures along
the KS/OK border, along the front, near 90.
After the potential for some lingering showers across southern KS
for Sunday morning, most of the area will see drier and cooler air
move into the area for the rest of Sunday afternoon/evening.
.LONG TERM...(Monday through Thursday)
Issued at 313 PM CDT Thu Sep 2 2021
Upper ridge looks to build over the Rockies for the end of the
holiday weekend into the beginning of the week. This will lead to
most of plains shifting into more a NW flow pattern by Mon into Tue.
This will lead to dry and seasonal conditions to start the week.
Another modest cool down could return by Tue-Wed, as a deepening
Great Lakes trough drives Canadian high pressure south. The ECMWF
continues to be more bullish with this scenario than the GFS, so
continued a middle ground forecast for now. this will lead to the
dry pattern continuing for much of the work week.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 626 PM CDT Thu Sep 2 2021
Thunderstorms and heavy rain will bring MVFR and IFR conditions to
most terminals at some point in this TAF period. KCNU is the only
terminal that is expected not to have any significant thunderstorm
activity through this TAF period. The remaining terminals are
expected to see at least some of this activity. Winds are not
expected to exceed 45kts at this time but very heavy capable of
producing ponding water on runways is possible with this activity
during the overnight hours. Thunderstorm threat after 12Z remains
in question and could see some changes here with subsequent TAFs.
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 73 89 70 83 / 40 60 70 60
Hutchinson 71 87 68 79 / 60 60 70 50
Newton 71 86 68 79 / 40 70 70 60
ElDorado 73 87 70 81 / 30 70 70 60
Winfield-KWLD 75 92 72 88 / 20 50 60 60
Russell 68 83 63 80 / 70 40 60 30
Great Bend 69 82 65 77 / 70 50 70 40
Salina 71 84 66 79 / 70 50 70 40
McPherson 70 84 66 77 / 60 60 70 50
Coffeyville 73 94 73 91 / 10 40 50 50
Chanute 73 88 73 86 / 20 50 60 60
Iola 73 86 72 83 / 20 60 70 70
Parsons-KPPF 73 91 72 89 / 10 40 50 60
...Updated for Aviation Forecast Discussion...
Issued at 250 PM CDT Thu Sep 2 2021
Main concern is late this afternoon and tonight with the
potential for severe storms accompanied by heavy rainfall.
WV imagery was showing a shortwave trof approaching the Black Hills
with an attendant cold front arching through western NE. Convective
activity pushing ahead of the front occurring within area of moist
upglide. A glace at 88D mosaic was showing some development along
the boundary over north-central NE.
Threat for severe storms will increase over the area heading into
the early evening hours. The RAP/HRRR is suggesting notable
environmental shear/stout effective shear and ESRH/ by that time
with the maxima progged to run along I-80 within the CWA. Given
that the environment will at least be conducing for supercell
development, a tornadic storm or two cannot be totally ruled out.
Eventually as storm mode evolves, the primary threat will
transition to damaging winds.
As eluded to, storms will be accompanied by heavy rain. Mesoanalysis
was showing stout low level moisture transport underway into the
central Plains with PW values up to 2". Precip efficiency will be
maximized overnight with a deep low-level warm layer in place
coupled with continued strong inflow of moisture advection. With
time the RAP advertises PW values approaching 2.5" with KI soaring
to 40. At this point, there is somewhat of a signal that areas along
and south of I-80 may see the brunt of rainfall accumulation
where omega phases well with better instability and boundary layer
convergence. By events end Friday morning, areas south may well
see locally heavy amounts around 2" inches or so over portions of
Post-frontal thunderstorms will be possible Friday night mainly over
the southern CWA in association with several minor impulses
Otherwise, very pleasant conditions with mild temperatures and
plenty of sunshine expected.
Fri - mid/upper 70s
Sat - mid 70s
Sun - upper 70s/lower 80s
Mon - lower/mid 80s
Tue - lower 80s
Wed - upper 70s/lower 80s
Thu - upper 70s/lower 80s
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 620 PM CDT Thu Sep 2 2021
Expect fairly widespread MVFR conditions at the TAF sites this
evening, likely continuing through early Friday afternoon. Some
periods of IFR possible in TSRA and then again later tonight
behind the cold front that will move through the region. Did
mention some gusts 35-40 knots possible at KLNK and KOMA. Storms
will probably be strongest 02z to 06z at those two sites. Trend
should be toward VFR conditions developing Friday afternoon.
Issued at 411 PM CDT Thu Sep 2 2021
Have issued a Flash Flood Watch for the southern half of eastern
Nebraska. Our total forecast QPF is on the order of 0.75 and 2.00
inches, but could see pockets of locally heavier rainfall if
training of storms occurs. Also, recent rains have saturated soils
over much of the area. Given this combination, felt it worthy of a
heads-up for the potential of rapid runoff leading to flash
NE...Flash Flood Watch through Friday morning for NEZ042>045-050>053-
Area Forecast Discussion
National Weather Service Portland OR
259 PM PDT Thu Sep 2 2021
.SYNOPSIS...A dying front will bring a chance for light rain to the
north coast this weekend. Upper level ridging will bring above
average temperatures to the interior valleys through early next week
before cooler temperatures arrive towards the middle of next week.
There is also a chance for some showers to move into the area
sometime between late Tuesday and late Wednesday.
.SHORT TERM...Tonight through Saturday night...Satellite observations
from Thursday afternoon showed clear skies across all of northwest OR
and southwest WA, aside from slightly hazy conditions due to upper
level smoke drifting westward from fires burning in the Oregon
Cascades. Surface visibility observations and air quality index
values suggested minimal smoke was near the surface, at least across
the Willamette Valley where visibility and air quality remained good.
This was not the case closer to the fires where surface smoke
continued to degrade air quality and visibility, especially in the
Oakridge area and along/near Highway 22 from Mehama to Detroit.
Expect this trend to continue tonight and tomorrow as light easterly
winds around 850 mb keep pushing smoke westward. Light offshore flow
will also result in a warm day tomorrow, with afternoon temperatures
most likely rising into the mid to upper 80s for the interior
lowlands. The coast should rise into the upper 60s to lower 70s by
the late morning or early afternoon before a sea breeze circulation
develops and knocks temperatures down into the low to mid 60s.
Flow should become westerly by Saturday afternoon, which will help
clear any lingering smoke/haze out of the area. This should make for
another mostly sunny day on Saturday, and the NBM suggests high
temperatures will be nearly the same as Friday. This seems reasonable
given little to no change in 850 mb temperatures. Low-level onshore
flow will keep the coast cool with highs generally in the 60s.
The 12Z NAM/GFS/EURO are in good agreement that a dying Pacific front
will begin pushing into the south WA/north OR coast Saturday night
into early Sunday morning, bringing a chance for light rain or
drizzle. Given the front will be weakening as it pushes inland, would
not expect rain for areas away from the north coast and Willapa
Hills. Models and their ensembles generally back this up by producing
very little to no QPF for inland valleys. -TK
.LONG TERM...Sunday through Wednesday night...The 12Z GFS/EURO both
depict nearly the same synoptic scale pattern over the western CONUS
Sunday into Monday, with a notable upper level high over interior
California strengthening as it builds northeastward into the Great
Basin region. The WPC`s cluster analysis for 500 mb heights suggests
confidence is high for this pattern to materialize as models and
their ensembles are in relatively good agreement when it comes to the
strength and timing of the upper high. This setup will result in
rising heights across the Pacific Northwest with southwest flow
aloft. 850 mb temperatures will also be on the rise, most likely
increasing to 20-22 degrees Celsius by Monday afternoon. As a result,
temperatures will be quite warm with highs around 10-13 degrees above
normal for early September. The NBM suggests highs will be well into
the 80s for inland valleys on Monday, if not around 90 degrees in the
Eugene area. Tuesday should be slightly warmer with widespread highs
in the upper 80s to lower 90s. In fact, temperatures in the mid 90s
cannot be completely ruled out just yet. Although unlikely, there is
a 9 percent chance temperatures will reach 95 degrees or warmer in
Portland, a 20 percent chance in Salem, and a 26 percent chance in
Eugene. Regardless of the outcome, record-breaking heat is not
expected. In addition, overnight temperatures will provide
significant relief to those without air conditioners as temperatures
fall into the mid 50s to lower 60s Tuesday night. Wednesday still
looks cooler with temperatures near seasonable normals as upper flow
transitions to westerly and low-level onshore flow strengthens. For
those wondering if the coast will get hot too, the chance looks very
slim at this point. There are no signs of offshore flow strong enough
to allow temperatures to warm much above the upper 60s to mid 70s
along and near the coast through the middle of next week.
Also worth mentioning is what appears to be a short duration of 500
mb southerly flow over the area Tuesday into early Wednesday morning
before flow transitions to westerly. This will help increase moisture
at mid-levels of the atmosphere, increasing the potential for
showers. Pattern recognition suggests there would also be a non-zero
chance for thunderstorms, but model guidance continues to indicate
that moisture and instability sufficient enough for thunderstorms
will reside to the east of the Cascade crest. Overall confidence is
low at this time and the potential will need to be monitored over the
next several days. -TK
.AVIATION...VFR with nearly cloud free skies with a few notable
exceptions. Shallow stratus hugging the coastline and has been
filling in over the past few hours. There is enough onshore
component to the wind to bring the stratus a little inland at the
coast tonight for IFR or LIFR conditions with clearing by mid
morning Fri. Smoke from wildfires in the Cascades are drifting
westward as the low to mid level wind is coming from the east.
HRRR smoke forecast shifts the smoke back towards the east Fri.
Otherwise VFR expected to prevail next 24 hours with diurnal
northwest to north breezes gusting to 15 kt in the evening.
For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse
KPDX AND APPROACHES...VFR prevailing next 24 hours. May see
increase in elevated smoke/haze later tonight and Friday.
.MARINE...High pressure will remain centered offshore through
Fri, with lower pressure well inland and along the north
California coast. The pressure gradient indicating marginal Small
Craft Advisory conditions the outer zones and central coast
nearshore water through this evening, so will leave the advisory
Wind speeds diminish Fri as the northerly surface gradients
weaken. May get some 20 kt gusts over the south zones Fri
afternoon, but not anticipating advisory conditions. Wind speeds
weaken even more Fri night and Sat as a weak frontal system moves
through the waters. Gradients tighten again early next week with
small craft advisory northerly wind conditions likely.
Seas will continue to be primarily wind-driven through Fri with
seas around 4 ft. Guidance shows wave heights 5 to 7 ft Sat
through Sat night, but then falling below 5 ft again by late Sun.
PZ...Small Craft Advisory until 11 PM PDT this evening for Coastal
waters from Cascade Head to Florence OR out 10 NM-coastal
waters from Cape Shoalwater WA to Florence OR from 10 to
Area Forecast Discussion
National Weather Service Las Vegas NV
644 PM PDT Thu Sep 2 2021
.SYNOPSIS...A few thunderstorms will linger over eastern Mohave
County this evening. Otherwise, expect dry weather with a warming
trend, peaking early next week as strong high pressure builds
overhead. A low-grade push of moisture could bring isolated
thunderstorms to the higher terrain around the middle of next week.
.UPDATE...A few stray thunderstorms popped up this afternoon in
southern Mohave County where some modest lingering moisture
remained over the region. They only lasted a few hours before drier
air and westerly flow helped knock them down and push the better
moisture and instability east. By the evening, dry conditions with
mostly clear skies were seen across the area. South to southwest
breezes were reported at times, with gusts generally 20-30 MPH
through much of southern Nevada and southeast California.
Expecting the winds to dissipate overnight with clear skies likely
across the region. Smoke may drift south into Inyo County overnight,
especially in northern portions of the Owen Valley. Overnight lows
will be similar to last night`s low temperatures.
.PREVIOUS DISCUSSION...217 PM PDT Thu Sep 2 2021
.SHORT TERM...through Friday night. Early afternoon satellite loop
showed a lone thunderstorm east of Kingman, scattered flat cumulus
over the rest of eastern Mohave County, and a few clouds on the
higher terrain of Lincoln, Clark, and San Bernardino counties.
Surface obs showed drier air moving in from the west, with a sharp
dewpoint gradient from 35F at Las Vegas to 55F at Boulder City at
noon. The HRRR captured the lone thunderstorm almost perfectly, and
the only other region with a mentionable chance of development this
afternoon is likely to be the Mount Trumbull area. Even less
activity is expected tomorrow, which could be a dry day CWA-wide.
The dry air and lack of clouds will bring a warming trend, which
will be discussed further in the long term section.
.LONG TERM...Saturday through Wednesday.
Building heat will be the main concern through the weekend and early
next week as high pressure reorganizes over the Colorado River
Valley. As the high strengthens into early next week, high
temperatures will climb several degrees above normal and pockets of
moderate to high heat risk begin to increase across the lower desert
elevations. Will need to monitor the trends for possible heat
headlines, mainly in the Colorado River Valley and adjacent lower
By Tuesday and Wednesday, the high pressure ridge amplifies and
shifts more into Utah and the Four Corners region, which will
introduce a more easterly or southeasterly flow pattern into the
region, potentially opening the door for additional monsoonal
moisture intrusions. However, ensemble members are split on
advancing deeper moisture into the region versus maintaining drier
conditions and a more dominant ridge overhead. NBM pop trends have
backed off a bit on their previous outlooks, now limiting
mentionable storm chances to Northwest Arizona and the highest
terrain of southern NV and Southeast California by mid-week.
.AVIATION...For McCarran...Gusty south to southwest winds through
sunset with speeds 20-25 kts. Gusts will fall off after sunset with
wind speeds up to 10kts continuing overnight. Light and variable
winds Friday early morning becoming easterly in the late morning. No
operationally significant cloud cover through the TAF period.
For the rest of southern Nevada, northwest Arizona and southeast
California...Southerly winds with gusts 20-25 kts across the
southern Great Basin and across the Las Vegas Valley TAF sites
through the afternoon. Southerly winds with isolated gusts at KIFP
and KEED. KDAG will gust around 20 kts from the west. Wind speeds
will drop off after sunset. No operationally significant cloud cover
through the TAF period.
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
For more forecast information...see us on our webpage:
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