Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/07/20

Area Forecast Discussion...UPDATED

National Weather Service Albuquerque NM

 503 PM MDT Tue Oct 6 2020

.AVIATION...
00Z TAF CYCLE
Upper high centered over northern NM/southern CO next 24 hrs. Weak
surface low developing over se CO/ne NM. HRRR Smoke model suggests
elevated haze/smoke will become more impactful over the southern two
thirds of NM between 07/06-14Z, however generally VFR conditions are
expected.

&&

.PREV DISCUSSION...258 PM MDT Tue Oct 6 2020...
.SYNOPSIS...
Dry conditions with sunny skies will remain the dominant weather
pattern through the remainder of the work week. Temperatures will
remain well above normal with several high temperature records in
jeopardy each afternoon. A pattern change looks to finally happen
this weekend as a strong Pacific storm system crosses the central
Rockies. Outside of some light rain and snow showers for northern New
Mexico on Sunday, most of the area will remain dry. Wind will likely
be the bigger impact from this system as well as a significant drop
in temperatures. Temperatures look to finally be near normal by the
start of next week.

&&

.DISCUSSION...
SHORT TERM...(TONIGHT THROUGH WEDNESDAY NIGHT)...
Upper level high pressure over NM begins to weaken tonight, as
low pressure deepens across the TX borderland while a closed low
moves inland off the coast of CA. Even with the lower pressure
heights, temperatures will remain above average, with near-record to
record readings possible Wednesday afternoon. By Wednesday night,
upper level high pressure develops in the Baja, allowing a ridge
axis to center across NM. Light winds accompanied by clear skies and
very low relative humidity values are expected through Wednesday night.

LONG TERM...(THURSDAY THROUGH TUESDAY)...
The pervicacious H5 high will finally start to weaken on Thursday as
a trough starts to approach the CA coast. With the trough not
forecast to move into central CA until Saturday morning, not much
change in weather conditions is expected through the remainder of the
work week. While 500mb heights fall slightly as flow turns
southwesterly ahead of the trough, temperatures will remain well
above normal with near to record breaking temperatures likely each
day. Dry conditions will reign as the southwesterly flow likely
transports more haze from CA wildfires into the desert southwest.

Then, finally, a pattern change arrives. The 12Z operational runs of
the GFS and ECMWF continue to agree with the trough weakening into an
open wave as it quickly moves across the Great Basin and ejects into
the central Rockies by late Saturday. No precipitation is expected
with this system, but temperatures will cool a few degrees across
the west as heights continue to fall. A second Pacific trough
originating from the Gulf of Alaska is then forecast to deepen as it
digs southeast into the central Rockies, potentially forming into a
closed low over southeast CO late Sunday. Models continue to keep
most of the precipitation associated with this system farther north
into CO & WY, but the trend continues to depict some light rain and
mountain snow for northern NM. The wind will likely be the bigger
impact from this system thanks to the upper-level jet that will be
steered over the area. Widespread breezy to windy conditions look to
be a safe bet on Sunday and wind advisories may be needed. Finally,
an associated potent Pacific cold front will also race through the
state Sunday night which will bring a welcome relief from the heat
next week. While today`s 12Z guidance has seemingly come into better
agreement regarding this system, forecast changes are likely as the
details continue to be worked out. Calmer, drier conditions look to
be on tap to start next week with temperatures near to slightly below
normal.

12/15

&&

.FIRE WEATHER...
A ridge of upper level high pressure will allow warmer than average
and drier air will persist through the end of the week. Single digit
RH values will be common each afternoon with poor recovery
overnight. The pattern of light to moderate winds will continue
until a major pattern change impacts the region during the weekend.
Min RH values between 10 to 20% will be widespread moving into the
weekend. A longwave trough will dig into the Desert Southwest Saturday
night, bringing with it strong winds across the state. Winds currently
appear to peak Sunday afternoon, likely bringing the potential for
critical fire weather conditions to much of the forecast area,
especially east of the central mountain chain.

12

&&

.ABQ WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$




Area Forecast Discussion

National Weather Service Denver/Boulder CO

 843 PM MDT Tue Oct 6 2020

.UPDATE...
Issued at 837 PM MDT Tue Oct 6 2020

The mountain fires produced a large smoke plume again this evening
which impacted much of northeast Colorado and will continue to
overnight. Low relative humidity and warm temperatures continue to
drive elevated fire danger and increased smoke production. No
changes were made to the forecast this evening.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 1251 PM MDT Tue Oct 6 2020

Warm and dry in the near term period. 500 mb ridge builds east and
becomes centered over the forecast area on Wednesday. 700 mb temps
on Wednesday bump up about a degree over today, however a surface
based wind shift should bring in slightly cooler air and keep temps
a degree or two below what we are seeing this afternoon. Northerly
winds set to arrive east of I-25 mid day, and remain mainly over the
northeast plains. Wind out there shifts to east 2-4 pm timeframe and
that will back in to the I-25 corridor metro area. Still quite dry
through the colum, and RH drops down into the single to low double
digits. Warm temps and low humidity will keep firest active and big
smoke producers. Will continue trend of mention smoke based on the
HRRR smoke products. Near surface smoke extends east and south
across the northern plains, then pushes south on Wednesday on
northerly surface flow likely reaching as far south as Palmer
Divide. Afternoon easterly surface winds will then push smoke
back into the foothills Wednesday afternoon.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 1251 PM MDT Tue Oct 6 2020

Upper level high pressure is progged to be centered over southern
Colorado Wednesday night. Upper ridging stays over the CWA
Thursday through Friday night. There is neutral energy in the
synoptic scale on the QG omega fields Wednesday night through
Friday night. The low level wind and pressure fields keep showing
normal diurnal low level winds for the CWA into the weekend.
Again, moisture is quite lacking through Friday night. The
precipitable water values are in the 0.20 to 0.40 range through
Friday night. Cross sections continue to show a decent warm layer
in the mid levels. There is no CAPE progged either. No measurable
precipitation on the QPF fields. No pops through Friday night. For
temperatures, Thursday`s and Friday`s readings will stay well
above normals, but not sure is they will get to record highs. For
the later days, Friday through Tuesday, southwesterly flow aloft
is in place Saturday, then a decent upper trough is progged to
move into and across Colorado Sunday and Sunday night. Monday
shows strong northwesterly flow aloft with more upper troughing
transitioning in on Tuesday. Saturday will be the last warm day,
then Sunday through Tuesday`s temperatures should be at or below
seasonal normals for a change. The GFS seems too warm Monday and
Tuesday with the upper pattern expected. The ECMWF`s thickness
and temperatures fields seem more reasonable with the upper
troughing expected. The GFS has decent moisture over much of the
CWA on Sunday and Sunday night, the ECMWF keeps the moisture
mainly in the mountains those period. Hopefully the CWA will get
precipitation.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 837 PM MDT Tue Oct 6 2020

Clear skies with VFR conditions overnight. Some smoke may impact the
terminals so it has been kept in the TAFs but still without reduced
visibility. Winds are relatively light and turning to normal
drainage. Tomorrow, expect light and variable winds in the
morning to become easterly around midday.

&&

.FIRE WEATHER...
Issued at 1251 PM MDT Tue Oct 6 2020

Fire weather concerns remain elevated to near critical through
Wednesday. Poor RH recovery overnight with minimum RH only rising
into the 30s-40s. With temperatures in the 70s and 80s and surface
dewpoints in the 20s, minimum RH in the upper single digits to
low teens. Fortunately wind speeds 10 mph or less, however a few
gusts in the higher terrain in the mid teens. Still well below Red
Flag criteria, however with dryness and warm temperatures fire
growth will continue to be an issue.

Models keep the minimum relative humidities both Thursday and
Friday afternoons quite low for the CWA. Progged wind speeds are
not very strong however. Fire danger will remain elevated.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Direnzo/Meier
SHORT TERM.......Hanson
LONG TERM........RJK
AVIATION...Direnzo/Meier
FIRE WEATHER.....Hanson/RJK



Area Forecast Discussion

National Weather Service Cheyenne WY

 541 PM MDT Tue Oct 6 2020

.SHORT TERM...(This evening through Wednesday)
Issued at 215 PM MDT Tue Oct 6 2020

Current satellite imagery shows clear skies across most of the
CWA while the smoke plume from the Mullen Fire continues to pick
up this afternoon. Smoke transport continues across southern
Albany and Laramie Counties as westerly winds prevail. An Air
Quality Alert is in effect through midday Wednesday as wildfire
smoke continues to degrade air quality across southeast Wyoming.
HRRR Smoke near-surface smoke concentrations remain elevated
through the entire 48-hr forecast run as dry conditions continue
to aid the Mullen Fire this week. Red Flag Warning remains in
place through 8 PM MDT as wind gusts 30-35 MPH continue into the
early evening. The 500-mb ridge slides more overhead Wednesday
resulting in weaker winds than Tuesday. Despite this, a few 25 MPH
wind gusts may be possible across Carbon County which will need to
be watched for possible fire weather headlines.

In addition to fire weather and air quality concerns, above
average temperatures continue across the CWA today and Wednesday.
Temperatures across the NE Panhandle range from the mid to upper
80s while Cheyenne just broke the record high (unofficially)
reaching 82 at this hour. Wednesday will be slightly cooler, but
will still see temperatures in the 80s east of the Laramie Range
and 70s west as 700-mb temperatures climb into the 10-14C range.

.LONG TERM...(Thursday night through Monday)
Issued at 300 AM MDT Tue Oct 6 2020

The dry and unseasonably warm weather will persist through
Saturday with a wsw upper flow over the region and lee troughing
resulting in dry downslope flow. Changes on the way however as a
significant upper trough will move into the far western CONUS by
late Saturday and then progress east across the region Sunday
bringing much cooler temperatures and at least sctd showers and
some higher mtn snow showers. Monday looks to be mainly dry but
cool and breezy under a fast wnwly upper flow with some snow
showers possible over the higher mtns.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 534 PM MDT Tue Oct 6 2020

VFR flight conditions will prevail for most terminals this evening
through 6Z. LAR and CYS will have MVFR flight conditions due to FU
from the nearby wildfires. Fluctuations for LAR between MVFR/IFR
through 2Z possible. TEMPO group has been added for CYS and LAR
due to this being present while there is still daylight. VFR
conditions are likely for all terminals after 2Z, but amendments
for SE WY terminals may occur if smoke takes longer to move out of
the area. Wind gusts should stay within 10 knots or less, with RWL
seeing gusty winds up to 20-25 knots between 0Z and 1Z only.


&&

.FIRE WEATHER...
Issued at 215 PM MDT Tue Oct 6 2020

Afternoon relative humidities will remain low over the next few
days between 7 to 15 percent with windy conditions Today and
Thursday resulting in critical fire weather conditions. In
addition to very dry afternoon humidity, overnight recoveries will
be poor with spots only rising back up into the 20s through
Friday. Stronger flow looks to arrive Saturday ahead of a passing
upper level wave that could result in another day of near critical
fire weather conditions before some relief arrives Sunday in the
form of seasonable temperatures and precipitation.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning until 8 PM MDT this evening for WYZ302>310.

NE...None.
&&

$$

SHORT TERM...MB
LONG TERM...RE
AVIATION...BW
FIRE WEATHER...MB



Area Forecast Discussion

National Weather Service Grand Junction CO

 521 PM MDT Tue Oct 6 2020

.SHORT TERM...(Tonight through Wednesday night)
Issued at 130 PM MDT Tue Oct 6 2020

High pressure continues to dominate over the western CONUS.
Forecast guidance remains locked in with afternoon high
temperatures running near 10 degrees above average at nearly all
major observation sites. With clear skies and extremely dry
surface conditions, overnight lows will end up near seasonal
averages. This has been the case over the past several days and
will remain the same through the end of the week. Elevated smoke
from wildfires to our west will result in another evening of hazy
skies today. HRRR smoke guidance supports additional lofted smoke
and haze on Wednesday, which has been added to forecast grids.
Forecast confidence is high through the short-term period.

.LONG TERM...(Thursday through Tuesday)
Issued at 130 PM MDT Tue Oct 6 2020

High pressure continues to drive a persistent weather pattern to
kick off the long term period. The distribution of individual
max/min temperatures from ensemble members only fluctuate 1 to 3
degrees, meaning, confidence in above normal temperatures during the
day and near normal lows remain high. The temperature distribution
and, therefore level of uncertainty, spread by Saturday with notably
large variability Sunday into Monday. This, however, should not come
as a surprise with the upcoming weather disturbances and
uncertainties that lie with the low pressure systems arriving this
weekend.

Deterministic models are aligning well with the overall trend of the
arrival of a Two-Punch system. First, a cutoff-low moves inland the
SoCal coast Friday night into Saturday. However, this system quickly
weakens into an open wave as it`s absorbed into the stronger and
deeper trough digging along the Pacific NW. We`ll notice in uptick
in southwesterly winds due to this initial disturbance, but little
moisture reaches the forecast area and will minimize any chance for
precipitation until Punch Two. The secondary trough drives into the
Pacifc NW Saturday evening/overnight, carrying substantially more
moisture. Both the GFS and Euro develop precipitation across the
higher terrain in western Colorado late Saturday evening, with the
bulk of the moisture arriving across the northern half of the CWA
by Sunday morning. The central and and northern mountains are
initially favored with this event, and forecast QPF fields reflect
that with nearly a half inch greater in total moisture content
than southern ranges. However, all northwest facing slopes
stretching down into the Northwestern San Juans will have a better
chance of accumulation under northwest flow. In addition, a
strong cold front tied to this trough would drop temps 15-20
degrees Sunday in comparison to Monday.

Much cooler temperatures and strong northwest flow flood the
forecast area in the wake of the weekend`s cold front. If this
scenario comes to fruition, majority of the forecast area could see
some form of precipitation...valley rain and a transition to snow in
post frontal conditions up high. Max temperatures drop below normal
as we enter the coming week, with lows dipping into the mid 30`s
across valley floors and subfreezing temperatures forecast across
higher terrain. Stay tuned, as finer details will be plucked apart
as the system evolves...and as mentioned previously...A wide
distribution in ensemble members illustrates the complexity of such
an event, which also reflects a lower confidence level in snow/QPF
totals this far out.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 513 PM MDT Tue Oct 6 2020

VFR conditions will persist for the next 24 hours. Evening
breezes over the higher terrain will diminish over the next hour
or two with light drainage flows taking control overnight. Expect
another mostly sunny and dry day on Wednesday with afternoon
breezes developing in the higher terrain once again.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...MAC
LONG TERM...ERW
AVIATION...MDM




Area Forecast Discussion

National Weather Service Goodland KS

 950 PM MDT Tue Oct 6 2020

.SHORT TERM...(This evening through Wednesday)
Issued at 222 PM MDT Tue Oct 6 2020

500mb RAP analysis and satellite imagery showed northwest flow over
the High Plains today, with upper ridging to the west. Meanwhile at
the surface, high pressure pushed southeast of the area. Sunny yet
hazy skies were observed across the region this afternoon, with
west to southwest winds at 10 to 15 mph. Gusts near 20 mph were
reported at some locations. At 2:00 PM MT, temperatures ranged in
the 80s.

High pressure continues to trek southeast tonight as temperatures
fall into the 40s to low 50s. The upper ridge begins to slide south
and east into the Plains. Any haze/smoke present during the day
should get pushed north of the region as winds shift overnight.

On Wednesday, ridging flattens as it spreads across the CONUS, and
nearly zonal flow develops aloft. Expect highs in the 80s to low
90s. Dry conditions remain in place, with relative humidity values
as low as 10 to 20 percent across the area in the afternoon from
west to east. Fortunately, winds will be light, at 10 to 15 mph, and
no fire weather highlights are expected at this time. Smoke and haze
from wildfires in north central Colorado and south central Wyoming
look to return to the region, particularly north of I-70, during the
day before improving Wednesday night. Temperatures fall into the
40s/low 50s once again overnight, with mostly clear to partly cloudy
skies developing after midnight.

.LONG TERM...(Thursday through Monday)
Issued at 252 PM MDT Tue Oct 6 2020

At the start of the forecast period, forecast guidance shows an
upper air ridge just east of the CWA with a shallow trough in the
west traveling towards the CWA on Thursday. The trough passes over
the CWA early Friday leaving a westerly zonal flow aloft going into
Saturday. On Saturday evening, models show an upper air trough
beginning to reach the western parts of the CWA which will turn the
flow aloft southwesterly going into Sunday. Model solutions begin to
deviate Sunday night in regards to the progression and intensity of
this trough. The ECMWF produces a 918 mb low over eastern CO on
Sunday night as the front end of the trough continues to move over
the CWA. The trough continues moving eastward placing the CWA just
north of the base of the trough on Monday night. The GFS shows the
front of the trough passing over the CWA on Sunday night and
developing a 925 mb low over the CWA on Monday morning. The trough
continues moving east giving the CWA a northwesterly flow aloft due
to being under the back end of the trough on Monday night. Due to
the model uncertainty currently seen, this situation will be
monitored to see if future model runs come into agreement.

At the surface, the Tri-State area expects to see dry conditions
continue through the end of the week followed by a chance
precipitation for the CWA to start next week. There is a chance for
showers and thunderstorms starting in the NW portion of the CWA on
Sunday evening that will gradually spread across the remainder of
the CWA through Monday afternoon as a slow moving cold front passes
through the CWA. Thursday afternoon shows potential for near
critical fire weather conditions for areas along and west of KS-25
as area RH values are expected to be below 20% with wind gusts
ranging from 15-25 mph. Elevated fire weather conditions are
possible not only this same area on Friday, but also for areas along
and west of KS-27 on Saturday as minimum RH values are forecasted to
be less than 20% with winds under 20 mph. Due to the frontal
passage, surface winds in the CWA on Sunday and Monday will be
coming from the NW with gust speeds possibly surpassing 30 mph in
some areas.

The Tri-State area expects to have high temperatures in the middle
80s to lower 90s on Thursday and Friday followed by highs in the
lower to middle 80s on Saturday. Sunday will see highs in the upper
70s to lower 80s followed by highs dropping to the lower to upper
60s range on Monday after the cold front passes. Tri-State overnight
low temperatures on Thursday and Saturday are forecasted to be in
the middle 40s to middle 50s range with Friday`s overnight lows
staying in the middle to upper 40s. Lows for Sunday night range from
the upper 30s in the far western CWA areas to the upper 40s in the
far eastern CWA areas. On Monday night, areas along and west of KS-
27 will see lows in the middle to upper 30s while the rest of the
CWA will see lows in the lower 40s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 950 PM MDT Tue Oct 6 2020

For KGLD and KMCK, vfr conditions expected through the period.
Winds generally begin the period from the southwest up to 10kts
with an expectation of veering to the west at similar speeds
around 12z then northwest and north near 10kts by 17z. After 18z
winds continue to veer to the northeast, east and southeast at
speeds under 10kts.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

SHORT TERM...JBH
LONG TERM...076
AVIATION...99



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

 619 PM CDT Tue Oct 6 2020

.SHORT TERM...
1259 PM CDT

Through Wednesday Night...

There are once again no weather impact concerns in the short term
period. Fast moving low pressure tracking near or just north of
Lake Superior tonight will trail a cold front into our area, with
the cold front moving across the area from the pre-dawn hours
north and after daybreak south. Out ahead of the cold front, a
stout low level jet will move overhead and likely get close enough
to ground level to yield some gustiness in the late evening and
overnight. Winds staying elevated as well as at least patchy mid
cloud shifting over the area will support above normal lows in the
50s area wide, with upper 50s in/near Chicago, setting the stage
for another mild day on Wednesday.

There will be modest cold advection up at 850 mb behind the front
on Wednesday, but we won`t cool much at 925 mb, so with the mild
start, deep mixing, and mild low level thermal progs, highs should
reach into the 70s again area wide, and some locations south of
I-80 could make a run at 80 degrees. Also expecting the dew points
to mix out into the 40s during the afternoon as northwesterly
winds temporarily gust up to 20-25 mph, possibly as high as 30 mph
at times. For this reason, with very dry fuels and low minimum RH
values, there will a slightly elevated risk of brush fire spread.
High pressure will quickly shift overhead on Wednesday night,
with light winds and clear skies enabling seasonably cool lows in
the 40s.

Castro

&&

.LONG TERM...
308 PM CDT

Thursday through Tuesday...

Pleasant and unseasonably warm weather is expected to continue at
least through the weekend. Wednesday`s cold frontal passage will
result in cooler overnight temperatures throughout the region,
likely bottoming out at around 50 in the heart of the Chicago metro
and in the low-mid 40s elsewhere. Additionally, with 40s dew points
and light winds expected overnight, there will be some potential for
at least patchy fog Thursday morning. Despite mostly clear skies,
expect high temperatures to not climb quite as high on Thursday as
they will on Wednesday given the cooler temperatures to start the
day, and thus have highs in the upper 60s/low 70s across the area.

Breezy southwesterly to south-southwesterly winds will build in
Friday afternoon as a low-level jet strengthens to our north.
Limited cloud cover will allow for sufficient mixing that will
likely tap in to 35-40 kt 850-900 mb flow by mid-late afternoon,
which would support wind gusts upwards of 30 mph at the surface. A
low-level subsidence inversion may play a role in inhibiting the
vertical extent of the diurnal mixing, and in turn, potentially
keeping high temperatures and winds lower than currently progged,
but with 30+ kt winds forecasted 1000 ft AGL, it will not take much
heating to start mixing in to some gustier winds.

Temperatures will peak on Friday afternoon with some locations
potentially hitting 80 for what would seem like the final time this
year before another weak, dry cold front comes through on Saturday,
stunting high temperatures from achieving their full diurnal
potential and leaving them a few degrees lower than Friday`s highs.
Increasing cloud cover from the approaching what-will-be remnants of
Hurricane Delta could also play a role in limiting high
temperatures, particularly for the southeastern portion of the CWA.
Sunday will look similar to Saturday, but a few degrees cooler,
slightly more cloud cover, and mostly easterly winds instead of
westerly.

The start of the work week looks to be a bit more active than this
week`s status quo with a high-amplitude upper trough expected to dig
southeast across the Rockies and into the southern Great Plains late
Sunday into Monday, spurring a surface low to develop somewhere over
the upper Great Plains. An associated cold front is then expected to
sweep across the central CONUS and bring us cooler temperatures
along with our next chances for precipitation sometime Monday and/or
Tuesday. Long range guidance currently doesn`t show much consistency
in how these features will evolve both spatially and temporally, so
have maintained slight chance PoPs as outputted by the NBM as
they seem reasonable for now, and will continue to monitor how
this system is projected to evolve in the coming days.

Ogorek

&&

.AVIATION...
For the 00Z TAFs...

Aviation forecast concerns:

* LLWS overnight.

* Northwest winds gusting around 20 kt Wednesday afternoon.

* Some chance of lake breeze shift to NNE at ORD and MDW late
  Wednesday.

Surface low pressure was over the arrowhead of Minnesota early
this evening, with a cold front trailing across the northern
Plains. Breezy west-southwest winds across the forecast area will
likely drop off briefly with the approach of sunset this evening,
though are expected to increase and become somewhat gusty again
from the southwest late evening/overnight as the surface low
deepens off to our north across the northern Lakes. A low level
jet of 45-55 kts is expected to spread across the area around and
after midnight, setting up the potential for a period of non-
convective low level wind shear (LLWS). While mechanical mixing
in the near-surface winds may limit the degree of shear somewhat,
HRRR/RAP and NAM soundings all indicate the potential for a brief
period of 50-55 kt west winds in the 1500-2000 ft range after
midnight which support maintaining a mention of LLWS.

The deepening surface low moves off to our northeast Wednesday
morning, allowing the low level jet to also shift east of the
terminals. The surface cold front will move through the area just
after sunrise, with a wind shift to the northwest. Winds will
likely gust around 20 kts by afternoon as deeper mixing develops,
with a few gusts into the mid-20s possible if the mixing depth is
higher than forecast. Gradient then weakens during the late
afternoon hours, allowing winds to diminish. HRRR forecasts
suggest a lake breeze may develop and push into MDW and ORD in the
23-00Z (6-7 pm) time frame, though no other models bring the
boundary that far west. For now not expecting the lake breeze to
make it, but will of course continue to assess for later
forecasts.

Otherwise, dry atmosphere will continue to support VFR conditions
through the period.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742...10 PM Tuesday to 4
     AM Wednesday.

     Small Craft Advisory...LMZ743-LMZ744-LMZ745...10 PM Tuesday to 9
     AM Wednesday.

&&

$$

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Area Forecast Discussion

National Weather Service Pueblo CO

 245 PM MDT Tue Oct 6 2020

.SHORT TERM...(This evening through Wednesday)
Issued at 245 PM MDT Tue Oct 6 2020

An upper level ridge will be centered over the area tonight and Wed,
keeping the weather dry.  The HRRR is forecasting an increase in
smoke in the air over much of the southeast plains late tonight
through Wed, but not really including the I-25 corridor.  Temps on
Wed will be above average, with highs in the 80s to lower 90s over
the plains and mostly in the 70s in the high valleys, and in the
upper 60s and lower 70s in Teller County.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 245 PM MDT Tue Oct 6 2020

Wednesday Night through Friday:

Upper-level zonal to southwesterly flow aloft will stay in place
from Wednesday night through Friday. The result will be dry
conditions across all of southern Colorado throughout this time
period. The southwesterly flow aloft will keep high temperatures
over the plains in the upper 80s to low 90s, the mountain valleys in
the mid-to-upper 70s, and the mountains in the 40s to 50s. The dry
air associated with the ridge will keep low temperatures at night at
seasonal values or slightly below the seasonal values. Some near
critical fire weather conditions may form over the far eastern
plains on Thursday afternoon, but confidence is low for that to
form.

Saturday and Sunday:

Main Points:

Low pressure system to arrive late Saturday.
Confidence - High

Seasonal temperatures return to southern Colorado by Saturday afternoon.
Confidence - High

Snow over the Continental Divide.
Confidence - High

Rain over the plains.
Confidence - Medium

Fire weather conditions over the I-25 corridor on Sunday.
Confidence - Medium

There is quite a bit of discrepancy within deterministic models of
the upcoming low pressure passage coming this Saturday and Sunday.
The ensembles do a better job of highlighting the timing of when the
low will reach southern Colorado. The thought is that a smaller
shortwave will pass over the region on Saturday morning, which cool
off the high temperatures on Saturday afternoon over the plains to
the low 80s, whereas the mountains and mountain valleys will stay
the same. The larger closed low is anticipated to reach southern
Colorado on Sunday morning, which will likely bring light to
moderate snow over the Continental Divide. As the low moves east,
ensembles are picking up on light QPF over the Palmer Divide and
over the plains during the later evening hours. Confidence leans towards light QPF
over the Palmer Divide, in the form of rain, whereas the rest of
the plains remains dry, with some isolated light rain showers. Before
the onset of precipitation, downslope winds may create critical
fire weather conditions along the I-25 corridor on Sunday
afternoon.

Monday and Tuesday:

Post low pressure system pattern will be from the northwest, which
will keep the air right around seasonal, with high temps in the 70s
over the plains, the 50s and 60s over the mountain valleys, and the
20s to 40s over the mountains. Dry conditions are expected otherwise.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 245 PM MDT Tue Oct 6 2020

KALS, KCOS and KPUB should have VFR conditions through the forecast
period, with generally light winds, mainly under 10 kts through
midday Wed.  Wed afternoon, winds at KCOS and KPUB will
probably be around 10 kts from the southeast.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...28
LONG TERM...SKELLY
AVIATION...28




Area Forecast Discussion

National Weather Service Reno NV

 232 PM PDT Tue Oct 6 2020

.SYNOPSIS...

High pressure gradually weakens into Thursday with mild afternoons
and crisp mornings, dry conditions, and mainly light winds. A
shift to cooler, breezy, and wet conditions is likely for the
upcoming weekend, with a drier pattern and a slow warming trend
returning for early next week.

&&

.SHORT TERM...

Not much change to the short term forecast this cycle. High
pressure remains the dominant feature through Thursday meaning a
few more days of above average high temperatures, dry conditions,
and typical winds. With some high level moisture expected to push
through from the south tonight thanks to a weak upper-level low
off the southern California coast, overnight low temperatures were
increased a few degrees across most of the region. The chillier
low temperatures look to return for Wednesday and Thursday nights.

Smoke and haze looks to stick around for the next couple of days
as well with new model guidance showing a general haze for most
locations in western Nevada with the worst conditions for areas
downwind of ongoing wildfires (i.e. most of Mono County (Creek
Fire), Lassen and northern Plumas counties (North Complex), and
the Truckee Meadows region (Baccarat Fire). With light flow under
the high pressure, this will make it difficult for smoke and haze
to clear, especially if current wildfires continue being active.
The HRRR smoke simulation has the Reno area only experiencing a
light haze for Wednesday afternoon, but confidence is low. By
Thursday afternoon, southwest winds are forecast to increase a
bit in response to a more developed surface gradient as the high
pressure weakens. This could lead to improved smoke conditions for
most areas, but also transport more smoke from the west depending
on fire activity. So, be prepared for at least hazy skies through
Thursday across western Nevada and the Sierra. -LaGuardia

.LONG TERM...Friday through Tuesday...

The focus remains on the incoming storm system for the weekend.
Model/ensemble guidance is still having its challenges trying to
resolve this system, which begins with a weak splitting low for
late Friday before the main trough passage Saturday-Saturday
night.

For Friday`s low: Yesterday there was a brief trend of the low
possibly tracking farther north across the Sierra and bringing a
short period of rain into Tahoe and parts of western NV. Today
that possibility was largely abandoned, with the latest consensus
keeping this low farther south and weaker with a slower arrival,
as the center moves onshore near Monterey Bay late Friday night.

For Saturday-Saturday night: We still anticipate three potential
scenarios, although the precip amounts for the most likely
scenario below have been scaled back a notch as the latest trends
show less moisture (but not zero precip) reaching eastern CA-
western NV.

1) Wetting rainfall (0.20"-0.60") for the Tahoe basin and areas
mainly north of I-80, with lighter rain (0.05"-0.25") spilling
into western NV from around I-80 southward, and extending south
into Mono County. Gusty winds with potentially elevated fire
weather concerns are expected Saturday afternoon-evening until the
rain arrives. The strongest winds are most likely from I-80
southward. 60% probability (trending higher).

2) Only a glancing blow for the area and more of a wind maker.
Little or no precip except maybe some lower end wetting rainfall
(0.10"-0.30") well north of I-80. With the gusty winds and drier
conditions, fire weather issues would become the primary concern.
30% probability (trending about the same).

3) A more direct hit of an atmospheric river for northeast CA into
the Tahoe basin (1-2" liquid possible), with efficient spillover
rain (0.25"-0.50"+) into much of western NV especially from US-50
northward, and southward into Mono County. Still breezy at times,
but this is the weakest wind scenario. 10% probability (trending
lower).

Most of the precip is projected to diminish later Saturday night
with a few light showers possibly lingering into Sunday. Snow is
unlikely to be much of an issue, with maybe a dusting of snowfall
above 9000 ft around Tahoe and above 10000 ft for Mono County.
Temperatures will remain about 5-10 degrees cooler than average
Sunday with highs mainly in the 60s, along with a modest northwest
breeze. Sunday night could have possible freezing conditions in
more areas, especially if skies clear out.

For early next week, ridging is expected to return in some form,
either with the center near or off the CA coast, or remaining flat
with the center well south of the Sierra. We`re expecting overall
dry conditions with a slow warming to near average by Tuesday,
although this variance in the rebuilding ridge could affect the
amount of warming and prevailing wind directions. MJD

&&

.AVIATION...

Biggest short term concerns will be continued areas of smoke and
haze, but main impacts are likely limited to the KMMH area from
Creek Fire, with CIGS/VIS lowering to MVFR at times mainly during
the afternoon-late evening hours through Wednesday. Aviation-
related impacts from the Baccarat fire north of Reno were minimal
at area terminals including KRTS/KRNO, and will likely be limited
to haze areas with reduced slantwise visibility above the surface.

Haze may continue into Thursday with smoke again most likely
around KMMH. Then attention turns to an approaching Pacific storm
still on track to affect the area late Friday into Saturday night
with some gusty winds and periods of MVFR CIGS with -RA mainly in
the northern Sierra. MJD

&&

.REV Watches/Warnings/Advisories...

NV...None.
CA...None.

&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno