Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/28/21

Area Forecast Discussion

National Weather Service Denver/Boulder CO

 816 PM MDT Fri Aug 27 2021

.UPDATE...
Issued at 814 PM MDT Fri Aug 27 2021

Position of weak upper level jet, in WSW flow aloft, combined with
some influx of tropical moisture, was allowing for widely sct
weak tstms this evening. In addition a Denver cyclone was
enhancing low level convergence, east of DIA, with a developing
line of storms.

Latest HRRR wants to consolidate this activity, into a small
cluster of storms, which will move across the far nern plains by
08Z. Based on current radar trends this trend is probably going to
be correct.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 232 PM MDT Fri Aug 27 2021

A closed low over Canada has a trailing trough with with some weak
perturbations in the flow pushing across Colorado late tonight and
Saturday. Conditions will clear out overnight after a few isolated
showers and storms move through during the evening hours before a
weak surge pushes south Saturday morning. Main impacts from any
storms that form will be gusty winds up to 40 mph with brief light
rain. The surge that pushes through early Saturday looks to be
pretty moisture starved but it will bring a slightly cooler
airmass and keep high temperatures in the upper 80s to lower 90s
for the plains. This cooler boundary layer will also help to cap
the atmosphere for Saturday and keep storms at bay and conditions
dry. Will maintain some low POP chances over the southern
mountains and foothills for late Saturday for isolated storms that
could form over southern portions of the state and push
northeast.

.LONG TERM...(Saturday night through Friday)
Issued at 256 PM MDT Fri Aug 27 2021

Saturday night features flat upper ridging for the CWA with an
upper trough moving eastward to the north of Colorado. This
trough will usher in a cold front Saturday evening. Flat upper
ridging remains in place with pretty weak west-southwesterly flow
aloft through Monday night. In the low levels, winds will keep an
easterly component to them much of Sunday. Normal diurnal wind
patterns are expected Sunday night through Monday night. The QG
Omega fields show benign synoptic scale energy all five periods.
Moisture is pretty sparse over the mountains through the periods.
There is some low level moisture with the upslope over the plains
Saturday night and Sunday. However, instability is lacking with a
strong cap in place. For Monday, there is substantial warming and
there is a notable cap around 500 mb. Not to excited for pops
Saturday night through Monday night.  For temperatures, Sunday`s
highs are 3-6 C cooler than Saturday`s. Monday`s readings warm-up
5-7 C.

For the later days, Tuesday through Friday, models have the upper
ridge push east and southeast of the CWA through periods, with a
significant upper trough over the western U.S. coast Wednesday
through Friday. The flow increases a bit and becomes more
southwesterly by mid week. Moisture increases a bit Tuesday into
early Wednesday, then is it increases significantly for Wednesday
through Friday. Tuesday looks pretty hot as far a temperatures
go, then it cools down to around seasonal readings for Wednesday
through Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 814 PM MDT Fri Aug 27 2021

A Denver cyclone was in place with weak convection to the east of
DIA.  There were also a few weak storms to the west as well.  Have
put in VCTS thru 04z in case one develops near the airport.  Winds
were northeast due to the circulation around the cyclone but still
expect them to go more southeast to south after 04z.

&&

.HYDROLOGY...
Issued at 232 PM MDT Fri Aug 27 2021

Drier conditions today compared to yesterday with just a few high
based storms possible. Dry for Saturday with no flood threat
expected for burn areas.

There isn`t a threat of flash flooding Saturday night through
Monday night. With the increasing moisture from Tuesday through
Friday, the threat of flash flooding will increase, especially
over the burn areas.

&&

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

$$

UPDATE...RPK
SHORT TERM...Bowen
LONG TERM....RJK
AVIATION...RPK
HYDROLOGY....Bowen/RJK



Area Forecast Discussion

National Weather Service Grand Forks ND

 958 PM CDT Fri Aug 27 2021

.UPDATE...
Issued at 958 PM CDT Fri Aug 27 2021

Upstream thunderstorms/showers decreased in coverage as they
moved towards our CWA this evening, however a few may hold
together through late evening. There looks lot be little in the
way of organized forcing overnight, but convergence along surface
trough and WAA aloft may be enough to support additional shower or
thunderstorm development as RAP still shows potential for
1000-1500 J/KG elevated CAPE axis overnight. However, there really
isn`t a noticeable LLJ and latest CAMs have backed off on
coverage/potential through 03Z. Better potential tonight will be
as clusters of showers/storms (currently in northwest SD) move
across the souther RRV. Patchy fog is being reported over parts of
our area with 3-6sm vis and Td depressions are approaching zero
across the region. Due to recent rains and light southeast flow BL
saturation may occur and short range guidance is showing potential
for fog. I made adjustments to timing of PoPs for the overnight
and added fog mention based on these trends.

UPDATE Issued at 635 PM CDT Fri Aug 27 2021

Showers are still lingering over our eastern CWA, but are
transitioning out in line with CAMs consensus. There should be a
lull in precipitation, the rest of the evening and there will be
at least some potential for smoke to advect back into the region
behind the departing showers. There is till a signal for possible
nighttime convection along an elevated CAPE axis/prefrontal
trough around midnight tonight into the early morning hours,
however there is very little consensus with a large spread in CAMs
regarding evolution or even development (more members show no
precip tonight than do show it). If something per to develop we
still could be in line for a few strong to severe elevated storms
as effect shear will be very high and elevated instability around
1500 J/KG. Worth monitoring, but confidence still isn`t high (will
monitor trends).

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 317 PM CDT Fri Aug 27 2021

Showers continue pushing northward this afternoon, with much of the
activity now in northwestern Minnesota. Quiet weather is expected
through the remainder of the afternoon as this exits the region to
the northeast. Through the early overnight period, scattered showers
develop through around midnight. Looking at CAMs, the majority of
guidance prevents the development of severe thunderstorms; however,
a handful of high resolution ensemble members bring a rather strong
line of thunderstorms through the area during the pre-dawn hours
Saturday morning. MUCAPE will be in the 1000 to 1500 J/Kg range,
with good 0-6 km speed shear upwards of 50 kt. Impacts would be
possible if this line strengthens along the cold front, with
damaging wind gusts being the primary risk.

Through the remainder of the day on Saturday, look for scattered
shower activity across portions of the region in the post-frontal
environment. Highs will climb into the lower to middle 70s. Showers
gradually work to the east, with clearing expected heading into
Saturday night.

.LONG TERM...(Sunday through Friday)
Issued at 317 PM CDT Fri Aug 27 2021

During the long term the pattern aloft makes some noticeable changes
that affect the propagation of troughs for the Northern Plains.
Through the weekend and into early next week, a ridge begins to
develop in the southern United States providing a SW return of
moisture from the SW. This helps provide decent monsoonal moisture
to the area and the translation of a trough into the region. Chances
for thunderstorms increase middle of the week as a trough moves in
from the SW. During the end of the week the pattern turns more NW
cutting moisture off from the south and amplifying a potential ridge
back into the SW United States.

Sunday and onward...

Dry and calm conditions end the weekend, with a zonal flow aloft
helping keep temperatures cooler across the region. Zonal flow
continues into Monday, with chances for thunderstorms during the
afternoon but on an isolated basis as a weak short wave moves in
from the Pacific NW. Isolated storms are possible Tuesday afternoon
before the flow aloft turns SW allowing for more moisture and better
signal of thunderstorms in the Northern Plains.

Thunderstorms are possible across the area Wednesday into Thursday,
with a deepening trough out west. Latest ensemble runs indicate
monsoonal moisture and part Gulf moisture interacting with the
system over the plains. Instability between ensembles have varied,
with low chances of CAPE exceeding 2000 j/kg. Majority of ensembles
have the probabilities of CAPE exceeding 1000 j/kg ranging from 40-
60%. Shear is rather weak in the lower levels compared to sfc to 8km
shear. This could inhibit some development of thunderstorms across
the region.

Uncertainty continues to lie in the timing of the system and how
much moisture it can tap into. Ensembles continue to show the system
affecting portions of western ND during the afternoon and evening,
with limited instability and daytime heating in the Red River
Valley. This would lower the risk of any stronger storms in the
region. Other scenarios show the trough moving faster along allowing
for eastern ND and western MN to tap into the heating and
instability during the afternoon. Moisture shows a surge from the
southwest, but how much there actually is is dependent on how
amplified the ridge may be in the southern United States.
Probabilities of precipitation exceeding 0.5 inches ranges from 30-
50% across the area, with the best chance closer to the
international border. After the system moves out further chances for
storms are possible to close out the work week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 635 PM CDT Fri Aug 27 2021

Variable flight conditions as a result of lingering stratus
across eastern ND and northwest MN, while showers are exiting
northwest MN early in the TAF period. There are clearing areas
with VFR conditions, but these are not likely to prevail as
stratus is shown by guidance to fill back in and IFR returns
overnight into Friday morning. Additional showers or thunderstorms
(some possibly severe) can`t be ruled out tonight, but better
chances are across southeast ND and west central MN Saturday.


&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$

UPDATE...DJR
SHORT TERM...Lynch
LONG TERM...Spender
AVIATION...DJR



Area Forecast Discussion

National Weather Service Grand Junction CO

 826 PM MDT Fri Aug 27 2021

.UPDATE...
Issued at 826 PM MDT Fri Aug 27 2021

Latest observations in northwest Colorado indicate that winds are
diminishing and relative humidities are increasing as surface
inversions take hold. Thus, have allowed the ongoing Red Flag
Warning to expire as scheduled.

&&

.SHORT TERM...(Tonight through Saturday night)
Issued at 255 PM MDT Fri Aug 27 2021

A few isolated thunderstorms have blossomed along the southern
foothills of the San Juans early this afternoon, favoring areas
with higher PWAT values and within the bullseye of elevated
SBCAPE. Slow moving storms will move off higher terrain to the
east-northeast, decreasing in coverage by 6 PM MDT. Main impacts
from said storms will be frequent lightning and gusty outflow
winds. PWAT values decrease as you move north across the Western
Slope, dropping from 0.8 inches to 0.4 over northeast Utah and
northwest Colorado. A dry slot, most noticeable at mid levels,
will support a deep mixing layer up to nearly 500 mb this
afternoon. As a result, gusty afternoon winds, 15 to 20 mph, are
likely across much of the forecast area. Meanwhile, an upper level
jet, rounding the belly of a low pressure system to the north,
has tightened the pressure gradient over northeast Utah and
northwest Colorado. As this piece of energy rotates across the
Northern Rockies, dry conditions and enhanced winds will generate
critical fire weather conditions over regions with susceptible
fuels (i.e. northwest Colorado). Winds will begin to relax in the
wake of the upper level jet this evening, and more-so once the
surface decouples after sunset. Therefore, the current fire
highlight remains untouched with this forecast package, dropping
off at 8 PM MDT.

Another lobe of PV and its associated jet maxima roll through
Idaho and into western Wyoming by tomorrow morning. Though this
system slides to our north, the northwesterly winds upstream will
start to push a rather thick plume of smoke from NorCal fires
back into our CWA. East central to northeast Utah and northwest
Colorado will see impacts first, early Saturday morning with the
plume extending southward throughout the day. Patchy smoke could
extend down to the Four Corners region, however higher
concentrations of smoke will likely hover along and north of the
I-70 corridor. Unfortunately, winds aloft shift to zonal flow by
Saturday afternoon, maintaining the swath of poorer air quality
overhead.

Temperatures will remain a few degrees over season normals
through the short term. However, if the HRRR smoke Vertically
Integrated Smoke Column comes to fruition, max temps across the
north may be a little too aggressive.

.LONG TERM...(Sunday through Friday)
Issued at 255 PM MDT Fri Aug 27 2021

A quiet start to the long term period will end on an active note as
the remnants of Tropical Storm Nora trek across the Desert
Southwest. Sunday will see quasi-zonal flow set up overhead
resulting in another warm, quiet day across eastern Utah and western
Colorado. A ridge of high pressure will build to our south on Monday
and gradually expand on Tuesday. Meanwhile, another upper level
trough will dig into the Pacific Northwest while the decaying Ida
continues to progress inland across the southeastern United States.
As a result of this synoptic shift, expect an increase in southwest
flow aloft with subtropical moisture streaming north on the backside
of the ridge. Early on we will see an increase in mid and high level
clouds over our forecast area before an uptick in shower and
thunderstorm coverage looks possible as early as Tuesday afternoon
and evening. This unsettled flow and increase in convection will
continue on Wednesday as Nora treks along the Baja coast. The
aforementioned Pacific trough will continue to elongate along the
western CONUS, shifting the ridge further east towards the Southern
Plains on Thursday. In response, the remnants of Nora will continue
to progress further inland across the southwestern states. As
mentioned, this additional swath of moisture could cause PWATs to
exceed 1 inch for a good portion of the area and possibly reach 1.5
inches for some locations. Though things could change, confidence is
increasing in the potential for widespread moderate to heavy
rainfall over the course of mid to late next week. We will continue
to remain vigilant over the coming days, most notably in regards to
how this increased convection could affect the high-impact Grizzly
Creek burn scar along I-70. Be sure to stay tuned to the latest
forecast!

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 537 PM MDT Fri Aug 27 2021

A few showers and storms continue over the San Juans but they will
quickly dissipate in the next hour or so. No concerns for TAF
sites. Few to scattered skies will become clear overnight as smoke
starts to filter back into the area. Do not anticipate any
restrictions to visibility but there will be smoke across the
area. Expect a few gusty surface winds tomorrow afternoon reaching
20 to 25kts from the west-northwest. VFR conditions will continue.

&&

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

$$

UPDATE...MDM
SHORT TERM...ERW
LONG TERM...MMS
AVIATION...TGR



Area Forecast Discussion

National Weather Service Goodland KS

 535 PM MDT Fri Aug 27 2021

.SHORT TERM...(This evening through Sunday night)
Issued at 309 PM MDT Fri Aug 27 2021

Across the region this afternoon, most of the area is under sunny
skies except for east/southeast locales as they still fall under the
influence of a trough that has been meandering over the CWA all day.
Temps are ranging in the 90s area-wide with winds mostly variable,
but a few locales are seeing gusts to 20 mph at times.

For the remainder of the afternoon, the wx focus will be on the
remnants of the trough that has been meandering about the CWA all
day. Latest analysis has shown this to shift a bit west this
afternoon. Areas of cumulus continue to pop up along and east of
this with some shower activity showing up. The latest HRRR is
showing a few hours of some activity, with a northeast movement
should anything get going and persist. Any storms will have sub
severe gust potential along with hail and locally heavy rainfall.

Going into Saturday, the focus shifts to an approaching frontal
boundary associated with a low/trough set to move off the Rockies
during the afternoon hrs. Model timing of this system will affect
areal coverage of any potential strong to severe storms that do
develop. SPC has almost all of the CWA under a Marginal risk for
wind/hail. The track of the system puts the CWA on the tail-end of
best instability, but daytime heating ahead of the arrival will
trigger storms. Model DCape values will peak in the 1500-2000 j/kg
range in the east/southeast around 18z. Threats will be mainly wind
with 60-70 mph possible, but hail around an inch is also possible.

Convection is expected to wane from west to east into the evening
hours as high pressure builds across the region overnight.
Persistent low clouds are probable going into Sunday morning due to
the positioning of the ridge axis and exiting front. Cooler air
persists thru the day as the ridge transitions east of the CWA late
in the day into the overnight hours.

For temps, highs on Saturday will be similar to this afternoon. 90s
area-wide expected. Warmest locales along/east of Highway 25. Sunday
will have a slightly cooler airmass with 80s expected. Overnight
lows tonight will be highly dependent on any lingering clouds from
any precipitation received. A wide range from the lower 60s west to
around 70F east is expected. For Saturday night, upper 50s west to
upper 60s east. And for Sunday night, upper 50s west to mid 60s east.

Concerns for high heat indices will only focus on the Saturday
timeframe. areas west of Highway 25 will see 90s, while along/east
of there will have upper 90s to even low 100s in spots especially
east of Highway 83.

.LONG TERM...(Monday through Friday)
Issued at 317 PM MDT Fri Aug 27 2021

At the start of the long-term period, the CWA lies underneath an
upper air ridge over the central CONUS which expects to be between a
trough in the east and a trough building in the Pacific Northwest.
This pattern aloft gives the flow over the CWA a westerly direction
to begin that changes to northwesterly by the evening as the troughs
squeeze the ridge. This trough-ridge-trough pattern continues going
into Tuesday with the western trough moving a bit eastward. The
eastward trough progression appears to continue into Wednesday and
begins to push the ridge to the east with the base of the trough
beginning to strengthen in the northwestern CONUS. By Thursday
morning, the flow over the CWA looks to turn southwesterly as the
CWA is underneath the inflection point between the upper air trough
to the west and the upper air ridge to the east. This northwesterly
flow continues going into Friday though the ECMWF shows the trough
beginning to progress eastward Friday afternoon with the GFS
starting the trough progression late Friday. The situation will be
monitored to see if better agreement will come about in future runs.

At the surface, the CWA looks to start with dry conditions followed
by some chances for precipitation through the end. Monday and
Tuesday look to have minimal chances of precipitation with possible
near-critical fire weather conditions seen on Tuesday for areas
along and west of the CO border during the afternoon. Minimum RH
values as low as 15% are seen in these areas, but the below criteria
maximum wind gust values continue to be the limiting factor. Chances
for precipitation return Wednesday morning as models show a possible
surface trough setting up in eastern CO along with increased
moisture coming in from the south at 850mb. A surface low pressure
system appears to develop in eastern CO on Thursday that moves
slowly northeastward through the CWA on Friday. This system looks to
show early signs for precipitation chances on both days, but models
show differences in how it plays out and will need to be monitored
in the upcoming runs.

The Tri-State area should see high temperatures on Monday between
the lower and upper 90s. On Tuesday and Wednesday, daytime highs
look to be between the middle to upper 90s followed by Thursday and
Friday seeing highs in the middle 80s to lower 90s. Tri-State area
overnight lows for Monday and Thursday look to stay in the upper 50s
to middle 60s with lows on Tuesday and Wednesday in the lower to
middle 60s. Friday`s overnight lows expect to be the coolest with
lows in the upper 50s to lower 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 529 PM MDT Fri Aug 27 2021

VFR conditions are expected through the forecast period at both
terminals. Winds become southerly this evening around 10-15kts
at KGLD with a period of low-level wind shear possible from
05-09Z. Southerly winds persist through mid-morning where they
become south-southwesterly around 13-17kts with gusts to 21kts.

At KMCK terminal, southerly winds prevail through the TAF period
with winds remaining generally under 12kts through 17Z. Winds are
expected to increase at that time as a boundary moves through the
area. A period of low-level wind shear may be possible from
05-12Z.

&&

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

$$

SHORT TERM...JN
LONG TERM...076
AVIATION...AW



Area Forecast Discussion

National Weather Service Green Bay WI

 610 PM CDT Fri Aug 27 2021

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 238 PM CDT Fri Aug 27 2021

Cloudy skies along with showers continued this afternoon. A few
thunderstorms were noted across east-central Wisconsin. The rain
and clouds kept temperatures down, ranging from the lower to
middle 60s north to the lower to middle 70s south.

A warm front south of the area will be the focus for showers and
thunderstorms through tonight. The combination of 850mb warm
advection, along with a low level jet cranking up will bring
rounds of showers and thunderstorms to the area. Convection in
response to the low level jet is expected to develop across
Minnesota and western Wisconsin and then move east across the area
later this evening and overnight.

Really thought long and hard about a Flash Flood Watch for
portions of central and northeast Wisconsin, especially in areas
that saw heavy rain last night. Based on the regional radar
trends, current thinking is the heavy rain axis will fall from
central Wisconsin northeast into Marinette, Oconto and Door
County. The meso models, especially the HRRR continue to move
around the axis of heavy rain thus the confidence was too low to
issue a Flash Flood Watch. Do believe there will be a band of
rain with rainfall totals of at least 1 to 2 inches in the above
mentioned area. As the complex rolls through the area, some of the
storms could become strong or severe with damaging winds as the
primary risk. Could not rule out an isolated large hail event.

The warm front will lift north into northern Wisconsin on
Saturday. The area should be capped, thus the risk of
thunderstorms through mid afternoon will be very low. By late
afternoon, the cap may erode enough for thunderstorms to develop,
especially across the north where there is 2,000 to 3,000 J/KG of
CAPE. If storms do develop, they will likely become strong or
severe with strong winds and possibly large hail. Highs will be in
the 80s to around 90. The combination of the heat and humidity
will cause the heat index value to climb into the middle 90s to
around 100F Saturday afternoon.

.LONG TERM...Saturday Night Through Friday
Issued at 238 PM CDT Fri Aug 27 2021

Severe weather and heavy rainfall potential Sunday evening, and
a continued threat of severe storms Sunday afternoon, will be the
main forecast concerns in the extended forecast.

A very unstable air mass will reside over the forecast Saturday
evening, with CAPE of 1500-2500 j/kg. The main focus for severe
weather and heavy rainfall should be over northern WI, where a 30
to 40 knot LLJ will intersect a surface warm front. Deep layer
shear of 35 to 40 knots will be supportive of organized
convection, including supercells. SPC has expanded the SLGT Risk
over most of northern WI, and this looks reasonable. Models show a
decent signal for heavy rainfall over northwest and parts of
north central WI, and this is where the core of the LLJ takes aim.
Not expecting much more than an urban flooding concern in north
central WI, as they have not received much rain in the past couple
weeks, and much of the region has sandy soils.

A cold front will sweep across the region on Sunday, accompanied
by a short-wave trough. Instability is expected to increase over
eastern WI by midday, with CAPE around 1500 j/kg. Scattered strong
to severe storms will be possible in the afternoon over northeast
and east central WI. SPC has outlooked this area in a Marginal
Risk of severe storms.

Generally quiet weather is expected from Sunday night through
the middle of the next work week, as weak high pressure remains
over the region. Temperature should return to near-normal during
this period, along with more comfortable humidity levels.

As the high pressure shifts east of the region, return flow will
bring a chance of showers and storms Wednesday night into Thursday.
A cold frontal passage will continue the chance of showers and
storms Thursday night into Friday.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 609 PM CDT Fri Aug 27 2021

Several rounds of showers and thunderstorms are expected this
evening into Saturday morning. Some of the storms tonight could
produce strong winds, hail and torrential rainfall. Conditions
will vary widely due to convection and lingering low stratus
clouds. Expect a mix of IFR/MVFR CIGS across central and north-
central with some VFR/MVFR possible in east-central Wisconsin.
Showers and thunderstorms will lower conditions as they pass
through. Easterly winds will gradually veer to the south late
tonight into Saturday morning. Southerly winds could gust to
around 25 knots Saturday afternoon.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....Eckberg
LONG TERM......Kieckbusch
AVIATION.......Kurimski



Area Forecast Discussion

National Weather Service Grand Rapids MI

 1034 PM EDT Fri Aug 27 2021

LATEST UPDATE...
Update

.SYNOPSIS...
Issued at 316 PM EDT Fri Aug 27 2021

- Chance of storms north tonight

- Hot Saturday

- Better chance of storms Sunday, possibly strong

- Cooler and much less humid air by mid week

&&

.UPDATE...
Issued at 1033 PM EDT Fri Aug 27 2021

Our strong to severe thunderstorms episode between Baldwin and Big
Rapids has come to an end. However as typical of a slow moving
warm front, every mid-level wave creates more thunderstorms. There
are currently two more complexes of thunderstorms, one over Iowa
and the other Wisconsin that are heading toward the northern 1/3
of Michigan between now an sunrise. The moisture transport vectors
suggest the storms will largely stay north of our CWA tonight.
That idea is also supported by HRRR and RAP models. However the
glitch is we have the NAM suggesting the warn front stalls
overnight and we have surface east winds down to I-94. If that
were to really happen, we may see convection develop after 3 am
near US-131 and last until after sunrise. The HRRR however turns
the east winds to the south southwest south of Route 20 by 3 am.
If that happens, the convection would stay farther north. I am
going with that later idea and believing the warm front is strong
enough to keep the convection farther north tonight.

Given the precipitable water is near 2 inches currently, any
storm could produce locally heavy rain as we have seen for at
least 5 days in a row now. That more than anything would likely be
our biggest overnight impacts.




&&

.DISCUSSION...(This evening through next Friday)
Issued at 316 PM EDT Fri Aug 27 2021

-- Chance of storms north tonight --

A warm front lifted through the cwa today and is now just north of
the cwa. Ongoing convection has been mostly over Wisconsin, but one
small bowing segment crossed over the lake and is currently
weakening. Mesoanalysis shows 35-40kts of shear and 1500+ j/kg
mlcape. We`ll continue to monitor the progress of this storm. CAMs
don`t show much pcpn the remainder of this afternoon through the
evening. After that, another are of storms may try to make a run at
the northern cwa after midnight. The HRRR/NAMNest/HREF show a line
of storms moving across northern Lake MI and then diminishing as
they get to the east side of the lake. The LLJ will remain over
Wisconsin tonight so once the storms move out of that favorable
environment, they should diminish. Overnight timing of the pcpn also
should lead to less instability so we don`t anticipate anything
severe overnight.

-- Hot Saturday --

We`ll remain in the soupy airmass Saturday. A decent amount of
sunshine coupled with dewpoints in the lower 70s should push
apparent temperatures to around 100. Because of that we issued a
Heat Advisory from 18z-00z. The stagnant airmass has also prompted
the Michigan Department of Environment, Great Lakes, and Energy to
issue an Air Quality Alert for Saturday.

-- Better chance of storms Sunday, possibly strong --

A cold front is expected to move across Lower Michigan Sunday
afternoon. Ahead of it, models indicate we`ll have sbcape around 2k
j/kg along with abundant low level moisture. It`s worth noting
though, that the short wave driving the front moves from Wisconsin
northeast across Lake Superior, so dynamical support may wane a bit.
However, the lift from the front should be enough to fire some
storms. I`d expect the strongest storms to be over the northern half
of the cwa. A Slight Risk of severe storms was noted by SPC north of
I-94 Sunday.

-- Cooler and much less humid air by mid week --

Behind the cold front, a little bit of an upper trough develops over
the Great Lakes early next week. This trough may be enhanced by the
passage of the remnants of Ida as it moves across the Ohio/Tennessee
Valleys. This will help to pull in some cooler and much less humid
air. Highs in the 70s and dewpoints in the 50s are expected.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 709 PM EDT Fri Aug 27 2021

At this point it seems to me VFR with scattered clouds is the best
forecast for our TAF sites through Saturday evening. Some light
fog is possible toward sunrise, I put 4-5SM BR for that. There
should be enough wind in the boundary layer to keep any thicker
fog from developing overnight.

Numerous waves of thunderstorms will continue to track eastward
(more or less) along the warm front tonight into Saturday but with
the front slowly lifting north, it would seem rather unlikely any
storms could get as far south as our TAF sites. Saturday should
be mostly clear with a few cumulus clouds that lack any serious
vertical development. The next threat for storms would be with the
cold front later Sunday.


&&

.MARINE...
Issued at 316 PM EDT Fri Aug 27 2021

A warm front is slowly moving north across the northern nearshore
zones. Winds are generally light from the south behind it. Other
than the potential for a few storms late tonight north of Whitehall,
no marine issues are expected until Sunday. At that point, southerly
flow will increase ahead of a cold front and waves may bump up to
small craft criteria north of Whitehall by Sunday morning. A Small
Craft Advisory may be needed then.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory from 2 PM to 8 PM EDT Saturday for MIZ037>040-
     043>046-050>052-056>059-064>067-071>074.

LM...None.
&&

$$

UPDATE...WDM
SYNOPSIS...04
DISCUSSION...04
AVIATION...WDM
MARINE...04



Area Forecast Discussion

National Weather Service Huntsville AL

 856 PM CDT Fri Aug 27 2021

.NEAR TERM...(Tonight)
Issued at 856 PM CDT Fri Aug 27 2021

Scattered thunderstorms are still ongoing at this relatively late
hour, with the most active storms focused SE of the HUN CWFA entering
Etowah and Cherokee Counties. 01Z mesoanalysis, 00Z BMX sounding,
and model soundings all suggest that the nocturnal inversion will be
rather slow to develop this evening, so storms may persist a little
later than usual. Otherwise, scattered cloud cover is creating a
broad temperature range across the area, with Tupelo having reported
87 at 01Z, and Decatur 73 at the same time.

The forecast has been updated a few times already this evening to
reflect ongoing radar trends, and one more update is needed to
account for the storms approaching from the SE. As mentioned earlier,
CAM trends and operational model soundings all suggest that these
storms may hang on a little longer than usual, so the forecast will
prolong PoPs into the late evening hours over eastern areas. It`s
entirely possible that this forecast is too conservative, though, as
the 00Z HRRR (which isn`t resolving the approaching cluster
specifically) brings isolated cells all the way into southern TN
before dissipating them around 06Z.

The rest of the forecast is in good shape, with low temperatures
expected to fall only into the mid 70s for much of the area.

.SHORT TERM...(Saturday through Sunday)
Issued at 312 PM CDT Fri Aug 27 2021

Chances for isolated to scattered thunderstorms will increase over
the weekend, especially on Sunday as an upper ridge continues to
shift west through the Carolinas and east/southeasterly flow results
in gradual moisture advection. These storms will be largely diurnally
driven as the lack of any real forcing mechanism limits coverage and
longevity. Will see little change in temperatures over the weekend,
as highs range from the upper 80s/lower 90s and overnight lows remain
in the low to mid 70s.

.LONG TERM...(Sunday night through Thursday)
Issued at 312 PM CDT Fri Aug 27 2021

All eyes will be focused on what is now Hurricane Ida, which is
expected to intensify into a major hurricane by landfall along the
southeast LA coast on Sunday night. Our impacts will start to ramp up
late in the day on Monday, as cloud cover and rainfall from the outer
feeder bands work their way closer to the Valley. This will moderate
temperatures a bit on Monday, keeping highs in the mid to upper 80s.
With the current forecast track, our main window for impacts will come
from early Tuesday morning through Tuesday evening. It is important
to keep in mind that even minor changes in the forecast track can
result in significant forecast changes as far as rainfall and severe
weather are concerned. For now, it looks like our main impacts will
come from flooding and a few tropical tornadoes also look possible.
Will have to keep our eyes on this system closely, as the track and
intensity will likely change at least some over the weekend. Do not
want to get too specific as far as rainfall amounts just yet, but
want those in the Tennessee Valley to be prepared for potential
flooding and review their severe/tornado safety plans.

Ida should exit the area by late Wednesday, where it looks like a
cooler, slightly more dry pattern will follow toward the latter half
of the week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 639 PM CDT Fri Aug 27 2021

Showers and perhaps a few embedded storms are lined up to impact
KMSL and perhaps brush KHSV between now and 01Z; for right now, TAFs
include VCTS with a short TEMPO group, but this may be adjusted and
amended further based on radar/lightning trends. Once these storms
weaken and dissipate, VFR conditions should mostly prevail thru
00Z/29. Scattered mid-level clouds should reduce the fog threat,
though brief patchy fog can`t be ruled out especially with storms
this evening. Scattered storms will develop again tomorrow afternoon.


&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

NEAR TERM...BCC
SHORT TERM...25
LONG TERM...25
AVIATION...BCC


For more information please visit our website
at weather.gov/huntsville.



Area Forecast Discussion

National Weather Service Elko NV

 246 PM PDT Fri Aug 27 2021

.SYNOPSIS...Dry weather with hazy skies from California wildfires
prevail through the weekend.

&&

.SHORT TERM...Tonight through Sunday evening.
Northern Nevada is on the southern fringe of a trough axis crossing
the northern Rockies. This changes the wind flow to west northwest
flow. This subtle change in wind direction may provide brief
respite to the smoky skies over northern Nevada. The HRRR smoke
model shows improving visibility tonight, primarily north of I80.
As the trough moves farther downstream, gradient winds return to
a westerly component and the smoke may return to northern Nevada
Saturday afternoon, and likely continuing into Sunday.  Breezes
increase to the 20-25 mph range Sunday afternoon as the next short
wave approaches the Pacific Northwest coast. With rising heights,
temperatures trend warmer the next two days.

.LONG TERM...Sunday night through next Friday

Hazy and smoky conditions are likely to continue through next week.
With an upper trough still expected to dig south from the Pacific Northwest
beginning early in the week, high temps are to gradually begin cooling
Monday. Expect high temps mostly in the mid to upper 80s by mid-week.
Overnight low temps look to reside in the low 50s for most Sunday
night before also creeping cooler with a return to mid to upper 40s by
mid-week.

Mostly dry thunderstorms with only a few wet storms possibly
mixed in continues to be expected for the Tuesday to Thursday time frame
with slightly greater activity likely on Wednesday. This will affect the
southeast portion of the forecast area. Be aware that there is still some
uncertainty in the amounts of moisture expected to reach central/eastern
Nevada. This is based on the additional factor of how much residual
tropical moisture may be pulled northward from the potential remnants
of Nora. Confidence remains relatively low at this time.

&&

.AVIATION...
Visibility may improve to 10+ statute miles this evening at KWMC,
KBAM and KEKO as surface winds shift from the northeast. VFR
conditions are expected to prevail, although brief periods of
5SM/6SM may occur in smoke or haze at any given time.

&&

.FIRE WEATHER...
Westerly gradient flow increases early next week with a trough
axis positioned along the Pacific Northwest coast. On Sunday,
appears winds stay below critical thresholds. Northwest Nevada,
particularly zone 437 may exceed the wind threshold on Monday and
Tuesday with local gusts reaching 30 mph. With the trough axis
moving inland, these afternoon wind gusts may expand its territory
and include all of northern Nevada. Afternoon humidities stay dry
with values around 10% (or less).

&&

.LKN WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

88/92/88/88



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

 922 PM CDT Fri Aug 27 2021

.UPDATE...
922 PM CDT

No significant changes to going forecast tonight. Thunderstorm
potential continues to look fairly low across the local area
tonight, and while perhaps a non-zero chance far northwest toward
morning, will maintain a dry forecast through the night.

Evening surface analysis depicts a warm front stretching from low
pressure over the Black Hills region, eastward along the IA/MN
border and into southern WI. Low level air mass south of this
boundary remains very warm/humid, though with some drier mid-level
air as noted in DVN`s 00Z RAOB. 35 kt low level jet was evident
from southwest IA into western WI, coincident with a narrow axis
of somewhat deeper moisture. Focus for evening convection has been
on the nose of the low level jet and along/north-northeast of the
warm front across northeast IA/southeast MN and parts of WI.
Strong storm over Grant county in southwest WI is expected to
weaken as it continues to track slowly east-southeast out of the
better low level jet winds and into the slightly drier mid-level
environment across southern WI/northwest IL. While not completely
out of the question some remnant could approach the far northwest
part of the cwa toward midnight, guidance trends continue to
focus best continued convective potential to remain across the
IA/MN border and into western WI within the low level jet axis.
New 00Z 3 km WRF and 01Z HRRR runs suggest there may be an
eventual southeastward sag of this activity as a consolidated cold
pool forms later tonight, though indicate weakening/dissipation of
updrafts along the outflow as it moves into northwest IL toward
sunrise. Based on these observational and recent CAM trends, will
maintain dry forecast at this time.

Otherwise, a warm and humid night is in store with temps in the
70s. Other than a few minor tweaks to hourly evening temps, no
significant changes made to going forecast which appears to be in
good shape.

Ratzer

&&

.SHORT TERM...
305 PM CDT

Through Saturday night...

Very warm and humid conditions will continue across the area
through Sunday. Similar to today, temperatures both Saturday and
Sunday afternoons will top out around, or just above, the 90
degree mark. This heat, combined with oppressive surface
dewpoints mid 70s, will result in heat indices topping out in the
100 to 105 degree range, especially for Saturday. While a heat
advisory is not currently anticipated (local criteria is a heat
index of 105+), it will definitely be a uncomfortable day to be
outside in the sun.

Thunderstorm chances tonight and on Saturday afternoon remain low,
but not zero. Tonight we will have to keep an eye on convective
trends to our northwest across northern IA and southern MN. This
activity could try to push an outflow boundary southward over
southern WI tonight. If it does so, some storms could accompany
this outflow boundary, but the better chances for this continues
to be north of the area in WI. I did maintain some slight chance
pops for storms late tonight, mainly near the WI state line.
Otherwise, it appears most areas will remain precipitation free
tonight. We will then have another slight chance for a few
isolated storms during peak heating Saturday afternoon, similar
to what is going on this afternoon. However, a majority of the
area is likely to remain dry.

By far our best chance for showers and thunderstorms this weekend
will be Sunday afternoon and evening as a surface cold front
begins to shift into the area. It appears this front will move
across northern IL during the evening hours of Sunday, and this is
likely to be the focal point for scattered strong thunderstorms.
Strong gusty winds and the threat for heavy rainfall will be the
primary hazards associated with these storms late Sunday.

KJB

&&

.LONG TERM...
310 PM CDT

Monday through Friday...

Confidence is fairly high in the front stalling by Monday in a
west-to-east nature somewhere within the Lower Great Lakes to Ohio
Valley region. This slowness and eventual stalling is aided by
the likely landfalling of tropical system Ida along the Gulf Shore
and progressing northward (see official NHC forecast). There may
be somewhere north of the hurricane on/near Tuesday that could see
some interaction of the tropical system`s high moisture and the
front, but at this distance that is an extremely low confidence
target, and only a handful of 00Z GEFS and ECE ensemble members
show a swath of higher precip north toward central Illinois and
central Indiana, and a majority of those are south of the CWA.

High pressure centered over the northern Lakes does look to expand
its influence southward into the CWA during midweek, with
northeast winds prevailing. Highs in lakeside counties look to be
shy of 80 for a couple days. The northeast winds may be enough to
bring waves to around a 4 ft average and present a heightened
risk of dangerous swimming conditions.

MTF

&&

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

Tonight, south winds will prevail with mostly clear skies. Winds
will become southwesterly after daybreak and gust 15-20 kt during
the late morning and afternoon hours. A spotty cumulus deck
rooted near 4000 feet will develop by early afternoon and fade
toward sunset. While no precipitation is expected through the TAF
period, a very small (<10%) possibility exists for thunderstorms
ongoing in northeastern Iowa to develop a cold pool and track
east-southeast toward the Illinois/Wisconsin state line during the
predawn hours of Friday. The most likely scenario, by far, is for
all convection to remain well to the northwest of all terminals
tonight.

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&

$$

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Area Forecast Discussion

National Weather Service Lubbock TX

 615 PM CDT Fri Aug 27 2021

.AVIATION...
VFR until further notice. Check density altitude.

Sincavage

&&

.PREV DISCUSSION... /issued 205 PM CDT Fri Aug 27 2021/

SHORT TERM...
Impressive cumulus cloud field across the area this afternoon
although short-term solutions remain nearly void of showers or
thunder. A couple solutions indicate shower chances developing near
the New Mexico border in far northwestern Parmer County early this
evening, while the HRRR lately has been indicating isolated coverage
of showers or thunder across the extreme southern South Plains. Weak
low level convergence does exist mainly on the Caprock, while
southeast low-level wind components are leading to a few healthier
cumulus or cumulus congestus over the north-central South Plains
especially close to the Caprock escarpment. Forecast soundings
indicate a likely subsidence bump around 9 to 10 thousand feet above
the ground, weaker near the New Mexico border, but will make it
difficult for updrafts to climb above this altitude. This is
consistent with the indications for a weak upper level ridge
overhead as well. For now, we are siding with the majority lack of
support for showers and retaining a dry forecast for the evening.
Overnight should remain mild with light southeast or southerly flow,
and also modestly moist so areas of stratocumulus mostly near 5000 to
6000 feet above the ground could occur.

Saturday, the weakness in the upper ridge is expected to remain
overhead. And conditions otherwise look mostly unchanged other than
a slight additional moisture increase. Again, solutions are lacking
significant shower or thunderstorm signals for our area along with
persistent though slightly weaker mid level subsidence bump. Perhaps
could argue support for low thunder chances in the southwest
Panhandle near the New Mexico border, but will keep forecast dry
with temperatures off another degree or so owing to the gradual
improvement in moisture. RMcQueen

LONG TERM...
The trend for showers and thunderstorms is gradually decreasing as
the Polar Jet flattens and becomes zonal across the northern half of
the CONUS during the day Sunday, out ahead of land falling Ida. A
weak synoptic trough will still linger from a disturbance north of
the Great Lakes region. Weak upslope flow across the South Plains
combined with little to no capping inversion will favor isolated
convection along the NM/TX state line in our northwest zones Sunday
afternoon. Less forcing to the east looks to leave deeper boundary
layer moisture untapped into the Rolling Plains. A stout ridge
builds in between Ida to the east and the remnants of Nora to the
west, when temperatures climb back into the low/mid 90s amid a dry
air mass on Tuesday and Wednesday. H50 heights lower slightly for
the end of next week as as the center of the ridge shifts east.
Monsoonal moisture should fuel convection across the mountains of
New Mexico, into next weekend, with any precipitation likely to
remain well west of our CWA.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

09



Area Forecast Discussion

National Weather Service Melbourne FL

 1029 PM EDT Fri Aug 27 2021

.DISCUSSION...

Current-Overnight...Radar trends show scattered showers and isolated
lightning storms over the local coastal waters. These will still
develop and occasionally move onto the coast overnight, but many
will diminish before making it too far inland. Most of the interior
should remain mostly dry overnight, but cannot rule out a stray
shower or two here. Primary threats from any heavy showers or storms
will be occasional lightning, isolated wind gusts to around 40 mph,
and torrential downpours leading to minor/nuisance flooding.
Movement remains from the southeast toward the northwest at 20 to 25
mph. Overnight lows in the mid to upper 70s.

Saturday...Previous Modified...After a dip in PW overnight, values
return to 2.00" and above as the surface high over the coastal
Carolinas begins to sink southward and Hurricane Ida continues its
drift northwestward in the Gulf of Mexico. Locally, deep easterly
flow will prevail once again and a similar setup with scattered to
numerous onshore moving showers and isolated to scattered
thunderstorms. Activity looks to be a little more favored across the
interior, so will maintain PoPs up to 50-60% in the late afternoon
hours. Highs will reach near 90F to the lower 90s across ECFL.

&&

.AVIATION...Generally VFR conditions, though MVFR invof showers and
isolated lightning storms thru Sat. Mainly dry over the interior
overnight and occasional scattered onshore moving showers/storms,
but they will likely diminish before they move too far inland.
Latest HRRR showing drier conditions on Sat so will be interesting
if this trend continues. Have "Vicinity" wording included in TAFs,
but confidence not there yet for any tempo groups. Cell steering
flow remains from the southeast toward the northwest. A tighter
pressure gradient exists on Sat so will see our (E/ESE) surface
winds a bit stronger with more gusts than this past day.

&&

.MARINE...Overnight-Sat...Continuing Cautionary Statements for one
more period (offshore), though it remains marginal. ESE winds 15-20
kts at times offshore with a diminishing trend thru the late night.
Seas 4-6 ft offshore becoming 4-5 ft by daybreak Sat morning. Seas
continue to subside to 3-4 ft near shore and 4-5 ft well offshore
through the day on Sat. Scattered WNW moving showers/isolated
lightning storms.

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&

$$

Sedlock/Weitlich



Area Forecast Discussion...UPDATED

National Weather Service Twin Cities/Chanhassen MN

 712 PM CDT Fri Aug 27 2021

.SHORT TERM...(This evening through Saturday night)
Issued at 319 PM CDT Fri Aug 27 2021

Surface analysis this afternoon depicts a surface low over the triple
point of the ND/SD/MN border with a warm front snaking SE into far
southern MN and WI with a cold front back to the W. A more potent
surface low lurks over far southern Saskatchewan province. Aloft, a
weak ridge axis is aligned from Hudson Bay down the ridge of the
Appalachians while a trough digs south from the western Canada into
the northern Rockies.

The surface warm front is expected to lift north through this
afternoon as a shortwave trough axis rounds the southern periphery
of the longwave trough into the Upper Midwest. Destabilization of the
atmosphere is occurring with the diminishing of any cap across
southern and eastern portions of the WFO MPX coverage area despite
fairly expansive and low cloud cover. Some convection is ongoing in
SE MN with CAMs (including the HRRR and NAMNest) suggesting
additional convection developing closer to the TC Metro. It will be
close as to whether the TC Metro sees thunderstorms through this
evening while southern MN into western WI have better chances, due to
more duration during peak heating of being warm-sectored south of the
warm front. Have shown higher PoPs in southern and eastern portions
this evening. There`s still the chance of isolated severe storms as
SPC analysis shows MUCAPEs of 2000-3000 j/kg around the I-90 corridor
but that gradient drops off quickly going north. In addition, while
low level lapse rates are not impressive, mid-level rates are so it
may be a challenge to get surface-based convection going. Closer to
the warm front could see more rotation in individual cells before
more organization takes place into clusters, leading to a damaging
wind and large hail threat. However, as noted, most of this activity
may well occur to the south and east of the metro and potentially
south and east of the coverage areas as a whole.

Any and all activity will diminish and push off to the east overnight
through the first half of tomorrow, leading to a tranquil but warm
overnight period. Lows tonight will only range from the lower 60s in
central MN to the lower 70s near the IA border, including around 70
in the TC metro.

Saturday continues to be a bigger concern with respect to severe
weather and heavy rain. The longwave trough aloft will shift into the
Northern Plains, placing the Upper Midwest into a strong mode of
advection both in terms of moisture and PVA. Mid-level jetting of
near 60kt is expected across the Dakotas which will effectively shift
east across MN/WI mid-to-late day. Cap erosion by mid-afternoon with
strong low-to-mid level moisture advection is expected, to the tune
of lower 70s dewpoints for much of the coverage area. In advance of
the cold/occluded front attendant from the aforementioned southwest
Canadian low, rapid storm development is expected in western MN which
will translate east into a well-organized line of strong to severe
thunderstorms with plenty of moisture and lift to produce heavy rain
along with a growing potential of large hail, damaging winds and
isolated tornadoes. The tornado threat looks to be the initial threat
upon discrete cell development, followed by large hail and damaging
wind gusts as the storms organize into a linear mode. Best timing
would be mid-afternoon into the evening. Rainfall amounts of 1-2" are
again fairly common, which may again lead to localized flooding
concerns. As SPC has already upgraded most of the area to an Enhanced
Risk (along with WPC placing eastern and southern portions in a
SLight Risk for Excessive Rain), residents and visitors are urged to
remain weather-aware through Saturday night.

The primary cold front will sweep across the region Saturday evening
through early Sunday morning, pushing any and all precipitation off
to the east and leading to clearing skies by daybreak Sunday morning.

.LONG TERM...(Sunday through Friday)
Issued at 319 PM CDT Fri Aug 27 2021

Sunday morning could still see some showers and thunderstorms in
west central Wisconsin, but the bulk of the activity should occur
Saturday into Saturday night. Behind this frontal passage on
Saturday high pressure will move in on Sunday bringing an end to our
days of wet weather. This break will be brief though as the pattern
looks to remain active next week. Monday looks more like Sunday than
it does any of the wet days this week with generally dry weather for
most. Southwest Minnesota could see some precipitation though
associated the advection of some warm moist air from the air mass
associated with Hurricane Ida. Tuesday looks fairy quiet though as a
ridge aloft builds into the Upper Midwest. Then Wednesday into the
end of the week sets up similar to what we`ve seen late this week
with a warm front setting up along the north of a ridge aloft. On
the temperature front expect near normal temperatures with highs in
the upper 70s through most of this period. Depending on how the rain
chances set up though we could see some cooler weather later in the
week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 712 PM CDT Fri Aug 27 2021

TSRA across southeastern MN will lift northeast and likely impact EAU
for the next few hours. Otherwise, cigs and visibilities
deteriorating later this evening at STC and AXN where dense fog is
possible. Line of thunderstorms will fire over western MN during the
early afternoon and push east through the mid evening, impacting all
TAF locations.

KMSP...No concerns tonight or Saturday morning. TSRA becomes
increasingly likely late afternoon, with a decent chance of severe
gusts (50+ kts) as it moves through between 00-02Z.

/OUTLOOK FOR KMSP/
Sun...VFR. Wind W 10 kts.
Sun night through Mon Night...VFR. Wind variable less than 5 kts.
Tue...VFR. Wind SE 10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&

$$

SHORT TERM...JPC
LONG TERM...NDC
AVIATION...Borghoff



Area Forecast Discussion

National Weather Service Marquette MI

 633 PM EDT Fri Aug 27 2021

.SHORT TERM...(This evening through Saturday)
Issued at 402 PM EDT FRI AUG 27 2021

Low confidence remains heading in tonight`s forecast as model
consistency/continuity continues to be poor. Water vapor imagery and
RAP analysis indicates a shortwave lifting ne into the area today
ahead of a broad western CONUS mid-upper level trough. PVA,
isentropic ascent and increased moisture transport and theta-e
convergence associated along and ahead of this shortwave has
increased shower coverage late this morning/afternoon across
especially central and eastern portions of the cwa. And with the
showers and clouds hanging over the area, temperatures have stayed
pretty steady this afternoon in the upper 50s to lower 60s north to
the mid to upper 60s south.

Big question tonight will be the evolution of convection as another
shortwave is fcst to ride along the warm frontal boundary situated
from southern MN into southern WI. This boundary is expected to move
north into central MN and central WI as a shortwave trough
approaches from the west. Based on current radar trends, it would
appear that the HiRes-ARW and maybe the NSSL-WRFARW have the best
handle with ongoing convection at the moment. Also like the HiRES-
ARW evolution of convection initiating along the frontal boundary
over southern MN early this evening and then tracking it ene into
central WI and then south central Upper Mi later this evening. This
ene track of more organized convection would makes sense since the
better instability is fcst by models to stay generally south of the
U.P. or along and just north of the frontal boundary. Will generally
follow this solution for fcst details into tonight as I expect there
should be a bit of a break in steady showers toward early evening,
but then showers should ramp up again, especially over south central
and eastern sections of the cwa later this evening into the early
overnight, as the second wave of convection works its way across the
area. Menominee County is in a marginal risk later tonight for
stronger to marginally svr storms, but with elevated instability and
effective shear looking marginal would expect stronger to severe
storms to stay mostly south of the area. Model trends are for storms
to dissipate and move east of the area late tonight. Min temps
should be mostly in the lower to mid 60s tonight.

Expect a mostly quieter weather across the area on Saturday as
shortwave ridging builds in from the west, although it will be quite
muggy with dew points ranging generally from the mid 60s north to
perhaps the lower 70s south and max temps expected in the upper 70s
to lower 80s. Max temps will be tricky as I`m not sure how much
sunshine we will see before clouds fill back in ahead of the
approaching cold front from the west late in the day. Building
instability ahead of the front will bring a chance of showers and
storms back into the western cwa late Sat afternoon.

.LONG TERM...(Saturday night through Friday)
Issued at 338 PM EDT FRI AUG 27 2021

Active with some potential severe weather is possible Saturday night
across the region before we progress into a dry pattern that will
last through a good portion of next week.

An eastward propagating line of showers and thunderstorms is
expected to develop upstream ahead of a cold front that`s tied to an
upper level trough moving through the Northern Plains. There is good
model agreement that the line could be over the far western portions
of the forecast area with a southward extension into Wisconsin by 0Z
Sunday. Models suggest plenty of instability developing during the
day Saturday ahead of the convection, and with some support provided
by a decent 850mb LLJ, thunderstorms with a damaging wind and hail
potential should move into the west and central before midnight.
With PWATs expected to be well over the 90th percentile moving
average, expect any thunderstorm to be capable of producing heavy
downpours. As instability wanes, expecting cold pool dominated
strata-precip to fill in behind the initial line and spread east to
northeastward for the remainder of the night. As the front moves
into the west by Sunday morning, another round of precip may
accompany it, but would be waning if so. Expect the front to shift
eastward through Upper Michigan on Sunday, with some redeveloping
shower and thunderstorm activity being possible out ahead of it
Sunday afternoon in the east half. As surface cyclogenesis tied to
the upper level trough takes place over Ontario, increasing pressure
gradient and CAA behind the front will support some breezy winds
near 30 mph across the Keweenaw by Sunday afternoon.

By Sunday night, ridging extending across the Plains northward into
north-central Canada will shift eastward and set off a prolonged
calm and dry spell across the region. Guidance suggests we could be
dry through at least Thursday.

High temperatures after the cold front will settle into the 70s for
much of the coming week. Overnight lows will be near 60F by the
lakeshores and 50s or mid 40s in the interior are also expected.
&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 633 PM EDT FRI AUG 27 2021

A somewhat moist east-southeast flow will persist over the area
through the fcst period. This will result in IFR/LIFR conditions
persisting at KCMX and KSAW in a moist upslope flow through much of
the period with maybe some improvement during the early afternoon on
Saturday. MVFR conditions at KIWD will also lower to IFR/LIFR late
tonight before improving to VFR later in the period. There is plenty
of fcst uncertainty with timing and coverage of showers, but expect
at least isolated to scattered coverage over the terminals into
tonight as a warm front slowly approaches from the south. Best
chance of showers looks to be at KSAW.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 402 PM EDT FRI AUG 27 2021

A tight pressure gradient between high pressure over Ontario and low
pressure in the Plains will continue to result in gusty easterly
winds perhaps as high as 30 knots into this evening. A warm front
will then lift northward towards the lake tonight, bringing winds
around to the southeast. As the high pressure north of the lake
lifts east on Saturday, the gradient will relax and the winds will
follow, falling blo 20 knots by Saturday morning. As a front crosses
Lake Superior on Sunday westerly winds could gust as high as 30
knots. High pressure building over the area early next week will
lead to calmer conditions through the middle of next week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 9 PM EDT this evening for MIZ005-
     014.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Voss
LONG TERM...JP
AVIATION...07
MARINE...Voss



Area Forecast Discussion

National Weather Service Pocatello ID

 125 PM MDT Fri Aug 27 2021

.SHORT TERM...Tonight through Sunday night. One shortwave will
depart the region this afternoon while a second one drops in from
the northwest tonight. Models offer only some showers around the
Island Park area tonight. Some lingering wind gusts are expected
until around sunset tonight, so will keep the Lake Wind Advisory
active through then. There is notable improvement in the smoke
forecast as observational trends show improving visibility and
better air quality. Some As the second shortwave departs to the
east, the region will come under the influence of weak ridging. This
will lead to dry weather that should last through Sunday night.
Hinsberger

.LONG TERM...Monday through next Friday. A broad upper trough over
WRN Canada will shift east through the NW states Monday and Tuesday
resulting in a dry SW flow aloft across the region and increasing
surface winds into Tuesday afternoon. The trough lingers over
Alberta Wednesday while a surge of sub-tropical moisture makes its
way north through Utah into the SE mountains. As we have discussed
over the last couple of days, the operational GFS and ECMWF (as well
as the ensembles) begin to show quite a bit of variability in the
model solution space Thursday and Friday. Hence, we will remain in
lockstep with the National Blend Solution until we see more
consolidation toward a reasonable solution. Huston
&&

.AVIATION...A dry upper trough was working east through the region
early this afternoon resulting in breezy west winds across the
region. Winds are expected to decouple and diminish after sunset
with VFR conditions prevailing through Saturday. Huston
&&

.FIRE WEATHER...Breezy and dry conditions will persist until around
sunset tonight, particularly across the Arco Desert. The shortwave
that is triggering the winds is also bringing some showers to the
Island Park area and extreme northern Lemhi county. Showers may
persist through the night until the shortwave pushes to the east
around sunrise tomorrow morning. Humidity will trend lower starting
tomorrow, though winds over the weekend should remain fairly light.
With the approach of another upper trough on Monday, we`ll see winds
increase across the region. This could lead to critical fire weather
conditions, mainly across the Snake Plain. Will continue to evaluate
the need for Red Flag Warnings Monday as models update. Afternoon
thunderstorms are back in the forecast starting Tuesday over zones
410, 411, and 413. Hinsberger
&&

.AIR STAGNATION...Significant improvement in smoke is expected
today as shortwave feature drives through and changes flow aloft
to a more westerly direction. HRRR smoke, both near-surface and
vertically integrated, show drastic clearing through today and
continuing through most of the weekend. Flow does turn back to the
southwest late Sunday, so we could see smoke return to East Idaho
by early next week. DMH
&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory from noon today to 8 PM MDT this evening for
IDZ054.
&&

$$



Area Forecast Discussion

National Weather Service Sacramento CA

 229 PM PDT Fri Aug 27 2021

.SYNOPSIS...
Hot and very dry through the weekend. Locally breezy north winds
will lead to areas of critical fire weather conditions over the
northern Sacramento Valley into Saturday morning, with a Red Flag
Warning in effect. Cooler weather returns next week. Breezy
southwest winds early next week over Sierra ridges.

&&

.DISCUSSION...
Satellite shows smoky skies across much of the area. Northerly
flow has brought wildfire smoke down through the Valley. Easterly
flow in the morning brought dense smoke into the Motherlode and
eastern Sacramento suburbs. The diurnal flow has reversed, with
westerly winds shifting some of the denser smoke in those areas
further to the east. The HRRR smoke model shows this pattern
reversing overnight, with dense smoke bake into the Motherlode
and eastern Sacramento suburbs by early Saturday. Smoke continues
to be an issue across the area through the weekend. For air
quality forecasts check with your local air quality district or
AirNow.gov.

Northerly winds and low humidity have brought Red Flag conditions
to the northern and central Sacramento Valley and surrounding
areas today. Redding currently has a humidity down to 9% with
winds gusting to 25 mph. Gusts of 25-30 mph are likely over the
northern half of the valley, and locally further south along the
western edge. Winds should gradually decrease overnight, but
overnight recoveries should be poor to moderate (25-40%) and winds
should pick up again early Saturday. The Red Flag Warning
continues until 11 am Saturday.

High pressure rebounds a bit over the weekend in the wake of the
short-wave. 850 mb temps climb to the upper 20s to around 30C over
the weekend. Given the amount of wildfire smoke, surface
temperatures will probably not realize their full potential.
Nevertheless, it will be hot with most Valley high temperatures
forecast to range from 100 to 105 (about 10 degrees above
average). Widespread moderate heat risk is expected.

The next upstream trough moves in early next week bringing cooler
temperatures and a return of onshore flow.

&&
.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...


Upper troughing remains along the West Coast through the extended
forecast period. This will result in below normal high
temperatures Tuesday into Friday. Locally breezy wind possible at
times through the Delta and over higher terrain, mainly afternoons
into evenings. This will likely clear some of the smoke out of
the Valley. Southwest ridge winds over the mountains could bring
fire weather concerns.

&&

.AVIATION...

VFR with MVFR to locally IFR at times next 24 hrs due to area
wildfire smoke. Generally elevated smoke layers 040 and 100 AGL.
Gusty northerly flow through the Sacramento Valley today. Gusts
20 to 30 kts possible through around 03 UTC.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 11 AM PDT Saturday for Central Sacramento
Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County
Below 1000 Ft-Eastern Mendocino NF-Eastern Portion of
Shasta/Trinity NF-Northern Sacramento Valley to Southern Tehama
County Line Below 1000 Ft-Northern Sierra Foothills from 1000 to
3000 Ft. Includes portions of Shasta-Trinity and Butte Units-
Southeast Edge Shasta-Trinity NF and Western Portions of Tehama-
Glenn Unit.

&&

$$



...Update to aviation forecast discussion...



 .DISCUSSION...
Issued at CDT Fri Aug 27 2021

Late this afternoon, an upper trough was located across the
central Rockies. A downstream upper level ridge axis extended from
the southeast US north-northwest into the southern Great Lakes.
At the surface a weak sfc trough axis extended from south central
NE southwest into southeast CO. There may be enough convergence
along this sfc trough axis to provide ascent for a few isolated
thunderstorms. The effective shear will be weak but MLCAPES will
be 100-1500 J/KG, so any pulse storm may produce gusty winds. I
placed a 20 POP across the northwest counties, in case isolated
storms managed to develop. The FV3 CAM does forecast a weak line
of storms developing across Republic CO after 20Z. The HRRR
develops isolated storms across northwest and west central KS. The
main synoptic front has lifted northward across central ND.

Tonight, any storm that manages to develop in the northwest counties
will dissipate after sunset.

Saturday through Sunday night, The upper level trough across the
central Rockies will lift east-northeast across the northern and
central Plains. Stronger low-level CAA across the northern Plains
will cause the surface front to shift southward across SD and
into north central NE during the afternoon hours. Several CAMs
show a line of storms developing along the front, then shifting
southeast across southern NE during the evening hours and into
north central KS after Midnight. If these storms can keep their
intensity, there might be a few damaging wind gusts within the
line of te storms. However, the effective shear will weaken below
20 KTS once this line moves into north central KS and the outflow
may outrun the line of storms causing the line to weaken. At this
time SPC has a marginal risk out for portions of north central KS
in case the line can hold together as it moves southeast across
north central KS after Midnight into early Sunday morning . It
looks as if the line of storms will continue to weaken and most
CAMs show the line of storms falling apart across the central
counties of the CWA during the morning hours of Sunday. Highs on
Saturday will range from the lower to mid 90s with heat indices
around 100 degrees.

Thunderstorm chances on Sunday will dependent on where the
outflow boundary/front ends up during the afternoon hours. The 3KM
NAM shows the front shifting south of the CWA during the
afternoon hours. If this were to occur the better chance for
thunderstorms will develop across south central and southeast KS.
If the front is slower and stalls out across the CWA as forecasted
by the ECMWF and GFS, then thunderstorm chances will increase
across the CWA. HOwever, the effective shear will be weak, around
10 KTS, so I`m not expecting any of the storms to be severe. The
H5 trough will lift northeast across the Great Lakes States.
Hurricane Ida will make landfall across the central LA coast late
Sunday night. Highs on Sunday will be a bit cooler with mid 80s
along the NE border to lower 90s south of I-70

Monday through Thursday, An upper level trough will move into the
northwestern US as the Hurricane becomes an extra tropical upper
low. An upper level ridge will amplify northward across the southern
and central Plains Tuesday into Thursday. Expect a slight warm  up
with highs back into the lower to mid 90s. The H5 trough across the
northwestern US will move east across the northern and central
Plains, as it passes north of the CWA, a weak surface

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 618 PM CDT Fri Aug 27 2021

VFR conditions are expected through the TAF period. Similar to
last night, the strongest portion of the LLJ will remain west of
the terminals, mitigating any LLWS concerns. Otherwise, southerly
winds will remain near 10 kt through the overnight hours with
gusts near 20 kt returning by mid-morning.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...Gargan
AVIATION...Baerg



Area Forecast Discussion

National Weather Service Las Vegas NV

 202 PM PDT Fri Aug 27 2021

.SYNOPSIS...Excessive Heat Warnings are in effect through Sunday
for parts of the area with dry conditions continuing and very hot
temperatures expected. Monsoon moisture will creep into our
area from the southeast, which could eventually limit afternoon
heating in our southern areas. The increasing moisture could lead
to a few isolated showers and thunderstorms developing in Mohave
County on Sunday. Shower and thunderstorm coverage could expand
further into our area next week as remnant tropical moisture from
Nora is injected into the Desert Southwest.

&&

.DISCUSSION...Through next Friday

Little has changed in the overall impacts we expect in the coming
days.

Temperatures will be 5 to 7 degrees above normal this weekend with a
smattering of zones covered by excessive heat warnings. There is a
new active wildfire in central Nye County. Smoke plume is visible on
satellite this afternoon contributing to the regional smoke/haze.
HRRR Smoke output continues to keep widespread smoke/haze across Inyo
and Esmeralda Counties. But can not rule out hazy conditions
anywhere across the southern Great Basin and Mojave Desert this
weekend.

Guidance still showing a minor influx of monsoon moisture moving
back westward into Mohave County maybe as early as Saturday
afternoon. Its better looking for Mohave County, southeast
California and Clark County by Sunday and Monday.

For Tuesday-Thursday: Attention then turns to how moisture from the
remnants of Nora comes into play. Official NHC forecast track keeps
Nora at hurricane strength into the southern Gulf of California
before making landfall as a tropical storm along the southern Sonora
coast between Guaymas and Bahia Kino. The current forecast track
fits very similar to Hurricane Lorena in 2019. There is uncertainty
in the track and strength of the storm as any interaction with the
southern tip of Baja would weaken the system quicker. Confidence
that moisture from Nora reaches into the Desert Southwest is high
and models have been consistent showing PW values peaking Tuesday-
Thursday. However, just how far west this moisture reaches and
impacts our area remains a bit more uncertain. Latest guidance
suggests a sharp moisture gradient will develop across western
Arizona and eastern California and southern Nevada. 12Z ECMWF
ensemble QPF continues to indicate Mohave County will likely see
some of our higher precip. amounts with values decreasing steadily
moving west into eastern California and southern Nevada. Stay tuned
as any shift west in this moisture would change the outlook for
eastern California and southern Nevada.

&&

.AVIATION...For McCarran...Southwest winds are expected to develop
this afternoon and become gusty at times between 22z-02z this
evening. Wind speeds between 10-18 kts with occasional gusts to 20
kts are likely. These winds will gradually diminish by 03z with
southwest winds around 10 kts remaining overnight. Winds will again
become light and variable after 14z and then gradually become
northeast to east around 7 kts between 15z-20z. Southwest winds will
once again develop Saturday afternoon with gusts up to 18 kts.
Mostly clear skies expected through the period.

For the rest of southern Nevada, northwest Arizona and southeast
California...South or southwesterly winds each afternoon and early
evening with gusts of 15-20 knots possible through Saturday. Winds
will become mainly light and variable overnight with speeds
generally less than 7 kts in most areas. Lingering haze is likely in
the Sierra and Owens Valley which may affect visibility into
Saturday around KBIH, but not expecting the visibility to drop below
6 miles at this time.

&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&

$$

DISCUSSION...Pierce
AVIATION...Gorelow

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