Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/06/24
Area Forecast Discussion
National Weather Service La Crosse WI
1010 PM CDT Thu Sep 5 2024
.KEY MESSAGES...
- Below normal temperatures Friday into Saturday, Rebounding
Temperatures Sunday into Next Week. Frost possible in typical
cool spots of central and northern Wisconsin Friday Night.
- Scattered showers tomorrow, otherwise remaining dry over the
next 7 days.
&&
.DISCUSSION...
Issued at 255 PM CDT Thu Sep 5 2024
Tonight into Friday: Cold Front this Afternoon, Showers Friday
Cold front is sweeping through the area this afternoon, bringing
northerly winds and clearing skies after this morning`s
thunderstorms. 850mb temps fall to around 7C tonight as an embedded
wave from an upper-level low north of the Great Lakes drops south.
This wave, combined with the steepening lapse rates will bring
scattered showers across the region Friday morning through Friday
afternoon, with a pretty robust cumulus field with it. Temperatures
will struggle to get above the mid 60s for most, and those in
central Wisconsin may not even break the 60 degree mark along and
north of Hwy 29.
Despite the northerly winds, models are hinting at the potential for
for fog development tonight in the river valleys. Fog is harder to
develop in the Mississippi River Valley with a northerly wind;
however, there is a better chance for fog development in the west to
east oriented river valleys. I think with the winds remaining
elevated enough, the more likely solution is to see a stratocumulus
deck develop with patchy fog possible in sheltered locations.
Friday Night into This Weekend: Seasonably Cool, Frost Possible
Friday Night
The upper-level low drops south through the Great Lakes Friday night
as 850mb temps fall to around 0C over Lake Michigan and 6C along the
I35 corridor. With surface high pressure overhead and light winds,
expecting good radiational cooling conditions as temperatures fall
to around 40 for most. East of the Mississippi, in the typical cool
spots, temperatures are expected to fall closer to the mid 30s with
frost possible on elevated surfaces. Thinking that there is enough
moisture around and soil temperatures are high enough to stave off
widespread frost issues. Fog will be possible across much of the
area, especially near sources of water, as temperatures fall into
the 30s to 40s.
Warm air advection returns along the I35 corridor on Saturday
evening, but it will be too late as temperatures will likely remain
in the mid 60s to near 70. As a western CONUS ridge builds Saturday
into Sunday, temperatures locally will begin to rebound Sunday into
the mid 70s and Monday into the low 80s.
Next Week: Trending Warmer
The western CONUS ridge deamplifies early next week as it`s axis
shifts east to the Upper Midwest. Anomalously warm conditions are
expected west of the area across the Dakotas, with temperatures
locally climbing back into the mid 80s Tuesday through the rest of
the week. Global ensembles suggest higher probabilities that a
surface high pressure remains locked in over the Great Lakes through
the rest of the week, that will keep the warmest temperatures west
of the local area; however, there is some spread as time goes on
with some members suggesting it shifts east with a 20 to 30% chance
of 90 degree temperatures Thursday into next weekend.
No mentionable chance for precipitation in the extended as a wave
rides along the ridge north of us into Canada Monday night.
&&
.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1010 PM CDT Thu Sep 5 2024
Some nuances to the forecast with potential for low (IFR/MVFR) cigs,
fog along with scattered -shra. All lower end chances (20-40%) but
something to monitor through the night and Friday.
CIGS: most of the diurnal clouds have dissipated but a raggedy,
broken deck of mostly VFR clouds is sagging southward across WI.
Some of the meso models continue to bring this across KLSE, but also
increase the near sfc saturation such that IFR/MVFR could manifest.
As mentioned, this is more of a "low end" outcome and will stick
with VFR for now. SCT-BKN clouds are then expected for the better
part of Friday as an upper level shortwave works on the available
saturation. VFR also favored in this stead. Expect clearing for late
afternoon/early evening.
WX/vsby: after the rains of this morning and clearing skies, fog
generally becomes more likely for the night time hours. However, a
few things going against - first drier air is sinking southward with
sfc Tds expected to drop 5 to 10 degrees by 12z Fri. So a change of
airmass. Second - northerly winds stay stirred in the near sfc
layer, working against pooling of a deeper sfc saturated layer.
Third - uncertainty in clouds. If more clouds are realized, that
cuts the fog chances, although could increase low stratus. Will hold
with P6SM and monitor trends.
Next, incoming shortwave trough Fri with weak instability and an
uptick in low level lapse rates will provide an environment for a
few showers (storms?). How soon/widespread is questionable. The HRRR
is the most rambunctious - likely due to producing more instability
and have a somewhat deeper moisture pool to work on. Low end chances
still look reasonable, perhaps as soon as late morning, but mostly
for the afternoon hours. With confidence not high that either TAF
site will be impacted, will keep the VCSH at KLSE. Some meso model
runs spread these low chances across KRST and may need to add VCSH
there in later updates.
WINDS: north/northwest through the period. Lighter tonight, some
uptick to around 10+ kts for Fri.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...JAW
AVIATION.....Rieck
Area Forecast Discussion
National Weather Service Boise ID
841 PM MDT Thu Sep 5 2024
.DISCUSSION...An upper-level ridge will persist over the region
through Friday, maintaining smoky conditions, particularly in
the central Idaho mountains. The latest HRRR model indicates
some improvement in air quality for the Treasure and Magic
Valleys as southeasterly winds bring relatively cleaner air into
the Snake Basin from tonight through Friday. However, expect
smoke to drain from the mountain valleys back into the Treasure
Valley late tonight. Little improvement is anticipated for smoke
aloft due to light steering winds.
A shortwave is still expected to move inland from the northern
California coast on Saturday afternoon, increasing the chance of
showers and thunderstorms (20-30%) into Sunday. The primary
concerns with these storms will be gusty winds up to 50 mph and
potential new fire starts. Temperatures will remain around 10
degrees above normal.
&&
.AVIATION...Low VFR to IFR in smoke with areas of mountain
obscuration. Surface winds generally SE 5-15kt. Winds aloft at
10kft MSL: S-SE 5-10kt.
KBOI...Low VFR to MVFR from smoke through Friday morning. Some
improvement is possible Friday afternoon. Surface winds SE
5-10kt.
Weekend Outlook...Continued smoke with reduced visibility, and
areas of mountain obscuration. A slight chance of showers and
thunderstorms late Saturday into Sunday.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Saturday night...Upper level
ridge remains over the area through the short term. Smoky
conditions will continue, especially over the central ID
mountains. HRRR smoke model shows some improvement this
afternoon with the heating of the day, but has smoke draining
out of the mountain valleys at night over the next several days
in the populated areas. The HRRR continues to show some
improvement in the Treasure and Magic Valley as southeasterly
flow brings relatively cleaner air down the Snake Basin into the
Treasure and Magic Valleys. Little improvement with the smoky
conditions aloft, due to light steering winds. A shortwave moves
inland off the northern CA coast on Saturday afternoon,
increasing the chance of showers and thunderstorms to 20-30
percent late Saturday into Sunday. Gusty winds up to 50 mph and
new fire starts will be the primary threat with the
thunderstorms. Temperatures remain around 10 degrees above
normal.
LONG TERM...Sunday through Thursday...The departing upper wave will
keep a chance of thunderstorms across southwest Idaho on Sunday.
Activity could be on-going from Saturday night near the ID/OR
border, transitioning into the mountains by afternoon. Dry southwest
flow will follow for early next week as a trough begins to deepen
off the coast. All the operational models continue to show a sharp
trough along the Pac NW coast by Tuesday night. From here there are
still differences on how quickly the trough pushes inland, but all
solutions are showing some eastward movement late Wed/Thur. This
supports at least low chances of precipitation Wednesday afternoon,
possibly becoming more widespread on Thursday. The 12Z ECMWF has
trended toward the GFS in that it closes off an upper low as it
tracks inland. Temperatures will be well above normal through
Tuesday dropping to near normal Wed/Thur.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
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DISCUSSION...JDS
AVIATION.....JDS
SHORT TERM...KA
LONG TERM....DG
Area Forecast Discussion
National Weather Service Dodge City KS
648 PM CDT Thu Sep 5 2024
.KEY MESSAGES...
- Very scattered and weak thunderstorms are possible (around 40%
via ensembles) for the far SE portions of the forecast area.
- A dry pattern with highs primarily in the 80s will take hold
across SW Kansas for nearly the entire forecast period.
&&
.DISCUSSION...
Issued at 231 PM CDT Thu Sep 5 2024
An upper-level trough continues to slowly trek eastward near the
US/Canada border. The system holds a westward tilt with height and
vertical continuity with a weak surface low positioned over the
western Great Lakes. The associated cold front has passed through
the forecast area and continues to be weaker than previously
forecasted, greatly hampering the chance (<15% via ensembles) for
most of SW Kansas to see any precipitation with the majority of the
thunderstorms likely contained in the SE part of the forecast area
stretching into south-central Kansas. The far SE area still has
ensembles offering around a 30-40% chance for accumulation,
coinciding with the only region where NAM forecast soundings show
any meaningful CAPE and shear values. Even in this region, modest
CAPE values (<1500 J/KG) and even lower effective shear values (<15
KTs) will virtually eliminate all severe potential. Models still
hold disagreement on exactly where the line of initiation will
occur. The HRRR and HRW FV3 are bullish on the forecast area seeing
convection beginning around the Pratt/Coldwater axis while other
models such as the NAMNST and the HRW WRF-NSSL have the area nearly
missing out entirely. The places that do see thunderstorms will
struggle to see accumulations due to the weak and very isolated
nature of the storms, especially at the onset. If the more
optimistic models are followed, the storms will have moved to the
east out of the forecast area by around midnight.
Moving into Friday, highs will hover in the 80s after marginally
being affected by the weak cold front. Days with highs in the 80s
will become the norm through the middle next week as a benign
pattern resumes. The pattern is headlined by a trough that long
range ensembles have moving into, and settling over the northern
CONUS late friday into the weekend. The ensembles show a large, dry
airmass settling over much of the west-central US including the
forecast area. As a result, the dry weather and temperate highs of
the upper 80s/low 90s will last nearly the entire forecast period.
At the end of next week, ensembles hint at troughing developing
along the west coast and a fairly robust moisture transport from the
Gulf of Mexico. The clarity of the more precise timing and impact of
this pattern change will increase with time in future
discussions.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 645 PM CDT Thu Sep 5 2024
Scattered showers and a few thunderstorms were moving south at
the beginning of this TAF period early this evening, however
none of this activity is expected to impact any of the four
terminals HYS, DDC, GCK, or LBL. A north wind will prevail this
evening with a gradual decrease in speed down to the 10 to 13
knot range later this evening before becoming 8 knots or less
later tonight. Light winds and good flying conditions in
widespread VFR are forecast for Friday.
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...KBJ
AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1203 AM EDT Fri Sep 6 2024
.KEY MESSAGES...
* A cold front will pass through the area during the late night and
early morning bringing showers and thunderstorms.
* Seasonally cool for the weekend.
&&
.AVIATION...
Clusters of thunderstorms flared up on the leading edge of the
larger band of showers now a combination of prefrontal trough and
cold front focus that collectively result in faster timing across
Lower Mi. A rumble of thunder also remains possible within the
larger band of showers as the SW to NE band moves NW to SE from MBS
to DTW around sunrise. Both MVFR ceiling and visibility become a
prevailing condition along with a few hours of IFR during peak
rainfall and close to the surface wind shift. MVFR ceiling lingers
through the morning in cooler NW flow which then builds into low end
broken VFR with the help of daytime boundary layer growth and wind
gusts near 20 knots. Disorganized VFR coverage lingers into Friday
evening as the wind gusts drop off around sunset.
For DTW/D21 Convection... A thunderstorm is possible ahead of the
primary band of showers supported by the inbound cold front which
remains the primary focus for activity. Late night timing suggests
storms will have low coverage and low intensity until the larger
scale shower pattern exits into Ontario and Ohio by mid morning.
DTW THRESHOLD PROBABILITIES...
* High for ceiling 5000 feet or less late tonight and in the
morning. Moderate in the afternoon.
* Low for thunderstorms late tonight.
&&
.PREV DISCUSSION...
Issued at 947 PM EDT Thu Sep 5 2024
UPDATE...
Showers are gradually increasing coverage across central/northern
Lower Mi during mid evening followed farther west by bands showers
and thunderstorms along the cold front. The leading activity
continues to expand within the moisture axis in response to height
falls and DCVA inbound with the mid level trough digging into the
Great Lakes. A rumble of thunder is possible in this sector of the
system but with greater potential along and immediately post cold
front. Hourly mesoanalysis and RAP projections suggest MUCAPE holds
near 1000 J/kg under 700-500 mb lapse rate generally sub 7 C/km.
This is just a check on storm intensity that is in line with a sub-
severe/general thunderstorm outlook projected within an otherwise
strongly sheared wind profile in a strongly forced larger scale
environment. The shower pattern then continues forward during the
late night while expanding into a larger band with widespread
coverage while crossing SE Mi. Timing in the going forecast looks
good for a southward/eastward exit of the band into Ontario and Ohio
by mid morning followed by cloudy and cooler conditions into the
afternoon.
PREV DISCUSSION...
Issued at 317 PM EDT Thu Sep 5 2024
DISCUSSION...
A tongue of mid Mississippi River Valley moisture centered at
approximately 850 mb will advect northeastward into most/all of
Southeast Michigan this afternoon. Surface observations upstream
across Indiana depict middle to upper 60s dewpoints associated with
the northward moisture transport. Latest indications suggest that a
capped or elevated <1000 J/kg MUCAPE will be present this afternoon
and evening with the introduction of the saturation between 3.0 -
6.0 kft agl. Model data suggests and radar data supports rogue
shower and isolated thunderstorm activity will remain possible
moving forward as altocumulus activity passes on by. Introduced a
slight chance for showers and a thunderstorm through 00Z. Dry air
subcloud with the inverted V sounding will support a gusty wind
potential. Weather interest for tonight is then centered on the 07-
11Z time window as hires consensus remains consistent with shower
and potential thunderstorm activity along a rapidly organizing cold
front. While the frontal structure is rather disjointed late
tonight, the low-midlevel convergence is very good which supports a
60-70% chance of precipitation from north to south. The trend noted
out of the 12Z model soundings is a higher likelihood for moist
adiabatic lapse rates after 08Z which limits the instability in the
midlevels to less than 250 J/kg. Given the lack of instability
convective vigor is anticipated to be weak. The one interesting
aspect for tonight is there is some uncertainty regarding the depth
of the static stability layer at the surface (some portion of
Southeast Michigan could see a stable layer at less than 2.0 kft
deep). Therefore, it is plausible that evaporative cooling at the
lead edge or some transient cold pool development could be enough to
result in more neutral stability conditions to allow some gusty wind
gusts. The latest SWODY1 has Southeast Michigan designated as
General Thunderstorm Outlook.
Friday...Shower activity will remain possible through approximately
16Z for the Detroit Metro area southward as elevated frontal
activity clears southward. Model data is then very insistent on
strong dynamic subsidence occuring in the 2.5 - 6.0 kft agl layer
that should very efficiently shut down precipitation potential.
Abundant stratocumulus is expected with some late afternoon breaks.
The exception will be those locations downwind of Lake Huron and
perhaps Saginaw Bay Friday evening and Friday night. A very deep
upper level trough and potential vorticity reservoir is expected to
activate the lakes in a big way. Lake effect parameters are
impressive lake induced CAPE of 1200 J/kg and equilibrium heights of
25.0 kft. The uncertain aspect of the Friday night and early
Saturday forecast is what surface wind trajectories will be in the
Thumb. There is a hires signal suggesting that thermal troughing
will be strong enough to direct greater north/northeast surface
winds in Huron County. Did increase PoPs significantly into the
likely/numerous category.
Weekend...Closed upper level low pressure will lead to 850mb
temperatures of 1-4C, which is roughly a degree colder than
advertised in recent days. Daytime highs are expected to be in the
lower 60s Saturday and near 70 Sunday. Models continue to support a
very dry atmosphere this weekend with saturation razor thin at the
top of the boundary layer. Continue to favor a optimistically dry
forecast for the weekend.
Next week...Sprawling surface high pressure is forecasted to build
across the Ohio River Valley next week. Latest indications are a
surface ridge extension will remain in place over Southeast Michigan
ensuring relatively lower humidity across the region. An extended
stretch of outstanding early Autumn weather with daytime
temperatures in the middle to upper 80s and lows in the 50s.
MARINE...
Southerly flow over the Central Great Lakes through this evening
ahead of a cold front, mainly just topping out around 20 knots. Low
pressure and associated cold front over Lake Superior will track
through tonight and Friday, with numerous showers and possible
embedded thunderstorms. The amount of cold air following the passage
of the front and filtering in through the weekend looks impressive,
with 850 mb temps settling around the freezing mark. The steep low
level lapse rates and instability will be supportive of lake
enhanced scattered showers continuing over Lake Huron right through
the Weekend, with waterspouts also possible. With the deep mixing
depths, wind gusts Friday night and Saturday will likely peak out in
the 25 to 30 knot range. However, this is a decided trend with the
winds backing quicker, leading to northwest/offshore flow Saturday
morning and the rest of the weekend. This will tend to limit the
higher waves (6+ feet) developing over the nearshore waters, but the
wind gusts and wave heights will still should be sufficient to issue
small craft advisories for Friday evening through at least the first
half of the weekend. Planning on issuing the small craft advisories
with the evening package. Winds then expected to become due westerly
on Sunday, making the call to extend small craft advisories
uncertain as winds just marginally reach around 25 knots.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 9 AM EDT this morning through this
evening for MIZ049.
Lake Huron...Small Craft Advisory from 3 PM this afternoon to 5 AM EDT Sunday
for LHZ421-422-441>443.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....BT
UPDATE.......BT
DISCUSSION...CB
MARINE.......SF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Sioux Falls SD
1025 PM CDT Thu Sep 5 2024
.KEY MESSAGES...
- Temperatures will trend cooler for Friday through Saturday.
- A return to above normal temperatures for next week, with
little chance of precipitation through the period.
&&
.DISCUSSION...
Issued at 225 PM CDT Thu Sep 5 2024
A pleasant afternoon, albeit a little breezy, is in progress across
the region with current temperatures in the 70s to around 80. With
cooling temperatures aloft, have seen a broad cumulus field develop
across the region, and as evidenced by a few of the hi-res models,
cannot completely rule out a few sprinkles during the afternoon with
weak upper level lift across the region. While wildfire smoke aloft
was making it down to the surface earlier in the day (with patchy
visibilities as low as 4 to 5 miles), current observations are all
above 7 miles. Although there may be a lingering haziness to the
sky, latest HRRR smoke fields would suggest continuing improvement
through the remainder of the afternoon. Otherwise, surface high
pressure over southern Canada begins to build southward into the
Northern Plains tonight. This will result in light winds overnight,
and with continuing cold air advection behind the previous cold
front, it will be a much cooler night with lows in the mid 40s to
lower 50s.
For Friday and Saturday, the surface ridge shifts through the
Northern Plains and into the Mississippi Valley through the period,
while an upper level trough deepens over the MS Valley/Great Lakes
region. This keeps a northwesterly upper level flow over our area,
and with 850 mb temperatures in the upper single digits to mid teens
C, temperatures will be below normal for both days. Highs on Friday
will be in the upper 60s to mid 70s, with lows on Friday night
in the 40s. Slightly warmer on Saturday as a southerly flow
returns to the area behind the exiting high pressure - though
still just below normal for this time of year with highs mainly
in the 70s over the entire area. A few of the hi-res models
would indicate a few sprinkles again possible over our far
eastern MN/IA zones on Friday afternoon with weak instability in
place between 800-700 mb, this collocated with an upper level
shortwave which will drop southward on the back side of the
aforementioned trough. In any event, measurable precipitation
will be hard to come by if anything occurs.
The nod to Fall will be short lived however, with both deterministic
models and ensembles pointing toward much above normal temperatures
for most of next week - this as the upper level ridging dominates
across the region during the week. Both NAEFS and ECMWF ensembles
indicate 700/850 mb temperatures in the 90th percentile or greater
with respect to climatology for Monday through Thursday of next
week, and currently forecasted highs are in the mid 80s to lower 90s
through the period. At the same time, precipitation chances look low
through the week with no real model consensus on precipitation
chances. Ensembles would support this with a less than 10 percent
chance of receiving a tenth of an inch of precipitation in any one
24 hour period.
&&
.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1024 PM CDT Thu Sep 5 2024
VFR conditions will continue into and through Friday. Some mid-
lvl clouds will drift into south central SD after daybreak, with
an additional area of mid-lvl clouds moving southward across
Minnesota on Friday morning. Between these areas, light winds
will prevail most of the day. Afternoon diurnal CU field is
likely.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...JM
AVIATION...Dux
Area Forecast Discussion
National Weather Service Grand Junction CO
935 PM MDT Thu Sep 5 2024
.KEY MESSAGES...
- Showers and storms along the Divide will persist through 6PM
before coming to an end this evening.
- High pressure builds in for the start of the weekend though an
odd shower or storm could fire over the San Juans Friday.
- Moisture starts creeping back into the area Monday onwards.
&&
.SHORT TERM /THROUGH FRIDAY/...
Issued at 122 PM MDT Thu Sep 5 2024
As expected, satellite and radar are showing some convection
right along the Continental Divide bringing a few showers and
storms there. The convection is in response to a shortwave
trough that is moving from north to south while the axis of the
shortwave is almost in a straight line from west to east from
Canyonlands NP through Gateway, Delta, and Crested Butte.
Enough moisture and instability is allowing this convection to
fire though most activity is in Pueblo`s CWA. If the HRRR and
NAMNEST are to be believed, as the wave keeps dropping southward
we can expect an uptick over the San Juans and possibly the
southern valleys through the late afternoon. Satellite not
looking all that impressive at the moment so we`ll see if this
comes to pass. The NBM certainly isn`t too excited and thus the
20 to 40% chances there. Either way, storms and showers will
produce gusty outflow winds and some brief, heavy rain. Models
all agree that convection will end shortly after 6PM giving way
to a tranquil evening. Elsewhere, plenty of sunshine is
expected as temps run a few degrees cooler than yesterday thanks
to north through northeasterly wind flow ushering in cooler
air.
A broad area of high pressure to our west will approach the Four
Corners region tomorrow bringing plenty of sunshine with some
clouds forming over the higher terrain tomorrow afternoon.
Despite the subsidence from the high, models do indicate a very
slim chance for a quick shower or storm over the San Juans
tomorrow afternoon. It`s possible so kept the PoPs and
convection in the forecast. Outside of that, dry conditions
persist as temperatures remain similar to today...maybe a
degree or three higher.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 122 PM MDT Thu Sep 5 2024
A center of high pressure will remain in place over the West.
Relatively benign meteorological conditions will continue here on
the West Slope as a result. Split jet flow around the high will
discourage meaningful dynamic forcing through the weekend and into
early next week. A couple of shortwave perturbations skirting around
the ridge will add some hints of moisture to the atmosphere, along
with some vague subtropical moisture sneaking under the ridge from
the south. This will likely be enough to see some very isolated
afternoon convection on the terrain features in the CWA on Saturday
and beyond. Wetting rain will be hard to come by with these storms
with the dry boundary layer conditions. Tuesday night, models begin
to dig a jet streak southward out of the Gulf of Alaska, deepening a
trough coming ashore in the Pacific Northwest. Model solutions are
still inconsistent on the timing and phasing of this storm, but
there is some general agreement in a pattern shakeup late week with
this storm pushing the high out of the way and arrival of dynamic
forcing under a stout jet max. Unfortunately, as currently
advertised, this storm pushes the subtropical moisture fetch
southeast and brings very little of its own moisture to work with.
Closing out this extended period, gusty southwest winds arrive
Thursday ahead of the front. High pressure and few clouds will keep
temperatures trending nearly 10 degrees over climatology in the
afternoon. Overnight lows will stick around the 5 degree warmer mark
through the period.
&&
.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 933 PM MDT Thu Sep 5 2024
VFR conditions and light terrain-driven winds are expected
through the taf period.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...TGR
LONG TERM...LTB
AVIATION...TGJT
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EDT Thu Sep 5 2024
.KEY MESSAGES...
- Much cooler tonight with showers, becoming lake enhanced off
of Lake Superior as the night progresses.
- High swim risk through Saturday for the Lake Superior beaches
of Marquette and Alger counties.
- Drier and warmer weather returns Sunday through much of next
week with increasing ridging from the west.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 347 PM EDT Thu Sep 5 2024
Water vapor imagery and RAP analysis show mid-level trof from Hudson
Bay into the Northern Plains/Upper Mississippi Valley. Lead
shortwave in the trof extends from James Bay to MN. Associated sfc
cold front runs from roughly ne Lake Superior to Marquette to Iron
River. A prefrontal trof noted from eastern Lake Superior across
eastern Upper MI has been associated with the main band of shra that
has progressed across Upper MI today. Additional isold to sct -shra
are occurring from ne MN into western Upper MI. Farther upstream,
another shortwave is over Manitoba. Daytime heating and resulting
instability has led to sct tsra with that wave.
As increasing cooler air flows into the Upper Lakes tonight under
northerly winds, 850mb temps currently at ~8-11C across Lake
Superior per latest RAP analysis will fall to -2 to 1C by sunrise on
Fri. With Lake Superior sfc water temps averaging 16-19C, the cool
air overhead will set the stage for an increasing lake component to
shra with time. Height falls resulting from Manitoba shortwave
diving se will further aid shra development overnight. Models show
low-level flow across the west half of Lake Superior having more of
an anticyclonic curvature tonight while flow is more cyclonic across
the e half of the lake. This will result in northerly flow lake
enhanced shra coverage being more numerous off of eastern Lake
Superior than off of western Lake Superior. Baraga/Marquette/Alger
counties will be favored for the most nmrs shra late tonight. So,
after a period of more nmrs shra across the area over the next
several hrs per radar trends, expect coverage to tail off some while
we await further cooling. As overlake instability continues to
increase, northerly flow lake enhanced shra will then develop
overnight and steadily increase in coverage thru sunrise. Temps
tonight will fall back into the 40s, except near Lake Superior where
readings should bottom out at around 50F.
&&
.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 352 PM EDT Thu Sep 5 2024
The extended forecast starts out with lake effect showers under
northerly flow. These gradually diminish Friday night into Saturday
as drier air moves in. While slight chances for showers continue
over the far east into Sunday, dry weather returns for the start of
next week. With mid level ridging returning next week, a dry pattern
is likely into the following weekend. Cooler than normal temps are
expected this weekend followed by warmer than normal temps for next
week into mid September.
Starting Friday, the mid level trough descends into the Great Lakes
while at the sfc: high pressure holds over northern Ontario and
troughing shifts east. This northerly flow with 850 mb temps
dropping to around -1C to -2C yields scattered to numerous lake
effect rain showers. North winds will be breezy near Lake superior,
gusting up to 25-30 mph with strongest winds expected over the east.
Highs are expected generally in the low to mid 50s, though upper 50s
to maybe 60 are possible in the south central UP where there is
better clearing from the lake effect clouds. Showers continue across
much of the UP Friday night as the sfc high pressure descends into
the midwest and the eastern trough deepens into a low, keeping the
UP underneath cold northerly flow. PWATs highlight drier air moving
in, which in turn works against lake effect over the far west. Lows
are expected in the mid 30s to low 40s, coldest interior west. Even
colder temps are very possible if a drier solution is favored
allowing for more clearing and radiational cooling to lower temps
further near or below freezing. Some patchy frost is forecast in the
interior west late Friday night.
Showers over the east mainly diminish Saturday morning as 850 temps
warm and high pressure becomes centered over the Upper Mississippi
Valley. The deepening sfc low looks to remain in Quebec, keeping
most, if not all isentropic ascent and Q-vector convergence outside
the CWA. So mostly dry weather returns to the UP. Highs Saturday
peak in the upper 50s to mid 60s, warmer in the south central UP.
Saturday night won`t be quite as cold because the colder airmass
aloft departs northeast from the Upper Great Lakes with the mid
level closed low; min temps are expected in the upper 30s to upper
40s. Sunday warms up in to the upper 60s to low 70s as skies clear
out in the late morning to early afternoon.
Next week, remains mainly dry as mid level ridging shifts east from
south central Canada/Northern Plains to the Great Lakes. While there
is a very low chance ~15% for showers accompanying a shortwave
Tuesday night/Wednesday, forcing is weak and there is uncertainty in
placement. Thus, kept forecast dry for now; will see partly to
mostly cloudy skies Tuesday night through Wednesday. The mid level
ridging along with the advance of a 850 mb thermal ridge with temps
approaching 18-20C by midweek means above normal temps, perhaps even
much above normal at times, will return to Upper MI. With model
guidance diverging into mid September, confidence in our next
significant measurable precip is very low.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 735 PM EDT Thu Sep 5 2024
Continued MVFR conditions are expected in this TAF period with a
cooler airmass building into the region supporting lake induced
clouds and scattered rain showers. Initially, some IFR ceilings and
MVFR visibilities will be possible at KSAW, but prevailing MVFR
ceilings and VFR visibilities is expected soon after issuance.
Expect slow ceiling rises through the period at all sites with KIWD
breaking out into VFR late while KSAW and KCMX remain MVFR. The bulk
of the colder air aloft arrives early Friday; this in combination
with the northerly upslope flow and long across lake fetch, will
result in more numerous rain showers for KSAW.
&&
.MARINE...
Issued at 352 PM EDT Thu Sep 5 2024
North winds 20-30 kts are expected into tonight behind the cold
front. The strongest winds are forecasted for over the east half of
the lake; some gale force gusts to 35 kts are possible between
Stannard Rock and the Eastern Lake Superior Buoy late this
afternoon through ~2AM EDT. Northerly winds of 20-30 kts
continue tonight into Friday night, highest over the east half
of the lake. Continuing into Saturday, northerly winds die down
to 15-25 kts and begin to back west to northwest in the
afternoon, again with the highest winds over the east half of
the lake. West winds look to diminish to mainly 20 kts or below
Saturday night. West winds to 20-25 kts are expected on Sunday,
strongest over the west half of the lake, before finally
falling below 20 kts across the lake Sunday night. Winds back
southwest to south into next week as high pressure ridging
returns quiet conditions to Lake Superior.
Significant wave heights are expected up to 5-9 ft late this
afternoon/early tonight along the southern half of Lake Superior,
highest waves between Marquette, Stannard Rock, and Grand Marais.
Waves of 4-7 ft continue over a similar region into Saturday morning
before falling below 4 ft Saturday evening/night.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Beach Hazards Statement until 10 PM EDT this evening for
MIZ005-006.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...Jablonski
AVIATION...JTP
MARINE...Jablonski
Area Forecast Discussion
National Weather Service San Francisco CA
745 PM PDT Thu Sep 5 2024
...New UPDATE...
.SYNOPSIS...
Issued at 1230 PM PDT Thu Sep 5 2024
Hot and dry conditions continue through Friday, resulting in a
moderate to major risk of heat-related illness and near critical
fire weather conditions. A pronounced cooling trend starts on
Saturday and continues into the next week.
&&
.UPDATE...
Issued at 740 PM PDT Thu Sep 5 2024
It was a hot and dry day today across much of the region.
Although no sites broke records today, it was still quite warm with
interior regions seeing temps in the high 90s, and a few low 100s.
Livermore Airport reached 102, Concord Airport 99, Pinnacles NP 105,
and closer to the coast, the Big Sur RAWS station reached 105.
Alongside the warm temperatures were some very dry conditions,
leading to many sites flirting with fire weather conditions this
afternoon. However, as the evening progresses, temperatures drop and
humidities begin to rise again, many stations that were flirting are
now back to normal.
Forecast otherwise appears to be on track. Heat Advisory is still in
effect through 8PM Friday for interior regions. Stay cool, and stay
hydrated!
&&
.SHORT TERM...
(This evening through Friday)
Issued at 1230 PM PDT Thu Sep 5 2024
Satellite imagery shows the stratus decks pared back to the
immediate coast to the north of Santa Cruz County, and staying a
fair bit offshore from the Monterey Bay region southward. Model
output suggests that stratus could once again develop into the SF
Bay region and the Sonoma County and Salinas Valleys tonight, with a
good chance that some patchy fog will develop across the region. A
quick primer on why fog develops overnight on hot days like this:
With the high pressure system over the western US, the marine layer
compresses, so while on cooler days the marine layer moisture can
flow farther inland, say, into the interior East Bay, on a hotter
day like this, the marine layer moisture is "trapped" by the coastal
ranges and condenses into fog closer to the coast.
Speaking of the high pressure system over the western US, that ridge
is still the dominant force over our region, giving us hot and dry
temperatures over the next two days. The Heat Advisory over the
interior portions of our region continues through Friday night as
temperatures rise into the mid 90s into the triple digits.
Elsewhere, high temperatures near the bays are expected to hover in
the 80s, while the coastal regions see temperatures in the 60s to
the low 70s. Low temperatures on Friday morning range from the mid
50s to mid 60s in the lower elevations, up to the mid 70s in the
thermal belts.
Daytime relative humidities are expected to be very dry inland, with
pretty much any location away from the coast seeing minimum relative
humidities in the 10-30% range. Overnight humidity recoveries will
be very limited in the higher elevations, as temperature remain warm
and the marine layer remains compressed. The operations team
considered issuing fire weather products for the Santa Lucias and
Santa Cruz Mountains, but after coordination with neighboring
offices, we`ve decided to hold off as the diurnally driven winds
will not last long enough to reach critical fire weather criteria.
Nevertheless, we are still anticipating near critical fire weather
conditions across the interior through Friday.
Moderate HeatRisk is widespread across the interior regions over the
next couple of days, which corresponds to an increased risk of heat-
related illness for sensitive populations, such as children, the
elderly, pregnant women, and people with chronic illnesses. In
addition, portions of the interior East Bay, the Santa Lucias, and
San Benito County are experiencing major HeatRisk, which impacts
anyone without access to effective cooling or adequate hydration.
Once again, a reminder of our heat safety tips:
* Stay hydrated and drink plenty of fluids.
* Wear lightweight, light-colored clothing.
* Reduce time spent outdoors or stay in the shade.
* Never leave people or pets unattended in vehicles.
* Use sunscreen if going to the coast or the pool.
As a final note, an upper-level shortwave will come through northern
California on Friday. Although the chances for thunderstorms are non-
zero, we`re not seeing the alignment between instability and
moisture needed to support widespread convection in the region. The
highest chances for thunderstorms are displaced towards the North
Coast, and the Sierra Nevadas. Even then, chances remain low with
probabilities around 10-20%. Any convection that does form is
expected to be high-based, with the primary threats being dry
lightning and gusty outflows.
&&
.LONG TERM...
(Friday night through next Wednesday)
Issued at 1230 PM PDT Thu Sep 5 2024
A pattern change brings us relief on Saturday as the ridge flattens
and moves eastward while a trough forms in the Gulf of Alaska and
drops into the eastern Pacific. By Sunday, temperatures should cool
to around the seasonal average, where they should remain into the
early part of next week, and more robust onshore flow should
develop, with gusty winds in the gaps and passes. Heading into the
later part of next week, model clusters are starting to hint at a
low pressure system that could bring some chances for rain to the
North Bay. That said, the model clusters continue to diverge on
location and timing, so uncertainty towards this part of the period
remains high.
&&
.AVIATION...
(00Z TAFS)
Issued at 517 PM PDT Thu Sep 5 2024
It`s VFR inland with patchy stratus and fog /IFR/ along the
coastline late this afternoon. The marine layer is compressed to
near sea level, however onshore winds will result in a mid-late
evening and overnight stratus and fog /VLIFR-IFR/ intrusion across
the San Francisco Bay and the northern Salinas Valley. Stratus
and fog will mix out back near the coastline late Friday morning
and afternoon.
Vicinity of SFO...VFR. Stratus and fog /IFR/ may be nearing SFO
Airport overnight and Friday morning based on recent RAP model
output, however for now will continue to advertise VFR and amend
the TAF as needed. Onshore wind 15 knots diminishing to around 10
knots tonight and Friday morning, increasing to 15 knots Friday
afternoon and evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR, then increasing VLIFR-IFR in stratus
and fog tonight and Friday morning. Stratus and fog mixing out back
to near the coastline late Friday morning and early afternoon.
Onshore winds 5 to 15 knots, becoming light and variable tonight
and Friday morning, then onshore winds 5 to 15 knots Friday
afternoon and evening.
&&
.MARINE...
(Tonight through next Tuesday)
Issued at 449 PM PDT Thu Sep 5 2024
Fair weather continues as high pressure persists over the region.
Winds will generally be moderate to fresh and west to northwest,
with moderate seas. It is not until the middle part of next week
that winds and seas begin to increase to become strong and out of
the northwest.
&&
.FIRE WEATHER...
Issued at 930 PM PDT Wed Sep 4 2024
The marine layer is approx 1000 feet deep this evening with some
compression forecast in the marine layer depth Thursday. It`ll
remain warm/hot and dry within the lower level temperature
inversion with little change in the strength of the mid to upper
level high pressure system tonight and Thursday. A mainly weak
500 mb trough moves in Friday along with thermal ridging embedded
within the trough at 700 mb and somewhat also at 500 mb which should
sustain air mass stability and preclude convection.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT Friday for CAZ502>504-506-510-
512>518.
PZ...None.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Canepa
MARINE...Flynn
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Area Forecast Discussion
National Weather Service Pendleton OR
546 PM PDT Thu Sep 5 2024
.SHORT TERM...Tonight through Sunday...A ridge of high pressure
remains over the region providing hot dry conditions across the
forecast area this afternoon. Smoke from regional fires has spread
across the entire forecast area leading to hazy conditions and in
some areas helping to suppress heating of the day on the order of a
couple of degrees. This ridge of high pressure will remain in place
on Friday for continued hot conditions with ongoing heat advisories
in effect. There is a small weak weather disturbance off the coast
of northern California that will begin moving towards southwest
Oregon late Friday. This will generate enough instability to trigger
some isolated thunderstorms across southern Oregon that move into
Deschutes County in the late afternoon and evening that could push
as far north as Jefferson County before dissipating. This
disturbance will trigger thunderstorms over central Oregon again
Saturday afternoon but then push them northeast into NE Oregon
overnight then linger into Sunday before the system exits the
forecast area late Sunday. This system will also begin the weakening
of the ridge so temperatures will be slightly cooler on Sunday but
still well above normal.
.LONG TERM...Monday through Thursday...A weak, transient ridge will
pass through the PacNW through Tuesday before a shortwave trough
makes its way from the British Columbia area to the region Wednesday
onwards. High temperatures will be mainly in the 80s and 90s on
Monday until decreasing Tuesday by 3-8 degrees below normal. Breezy
winds will be around 20 mph or less at the Cascade Gaps due to
tightened pressure gradients. Showers will develop for Tuesday night
at the WA/OR Cascades with a slight chance (15-30%).
Wednesday through Thursday night, the major concern will be the
showers and isolated thunderstorms. Models are in good agreement on
the trough off Oregon coast traveling through the PacNW with
southwest flow, including its amplitude. This could increase chances
(50-70%) of showers at the low elevations and t-storms in the
eastern Blue Mtns. The deterministic GFS shows MUCAPEs below 500
J/kg and low 0-1km bulk shear, indicating little to no instability.
The ECMWF and Canadian models even show the trough moving across and
out of the PacNW sooner than the GFS. If the trough moves closely
sooner, cooler temps and potential t-storms will occur. If not, then
warm temps can last longer. This makes forecasting this weather
pattern challenging, given the timing differences and uncertainty of
this trough`s behavior.
Gradients will tighten along the Cascades, inducing elevated wind
gusts around 25-35 mph with breezy winds through the Kittitas and
Yakima valley and the eastern CR Gorge (30-50% probability). As
trough begins moving east out of the area Thursday night, showers
and t-storms will then be over the edge of the eastern Blue Mtns and
Wallowas. Chances will lower as convection weakens while the
remainder of the forecast area have lingering showers as the trough
continues moving east. Feaster/97
&&
.AVIATION...00Z TAFs...Limited concerns through 00Z Saturday.
Currently a few swaths of cirrus/cirrocu lifting into central OR in
tandem with translucent to opaque smoke aloft across much of central
OR that is spreading north and east. Limited visibility impacts from
smoke seen today, except KRDM terminal that was sub-VFR this
afternoon.
Light winds, largely terrain driven, prevailing through early
tomorrow with a sharpening gradient prompting light north/northeast
breezes Friday afternoon. Otherwise, HRRR runs hint at possibility
of addition visibility restrictions from smoke in central OR,
however, confidence sub-50% thus precludes a mention in any TAF at
this time. Looking ahead, a 10-20% chance of thunderstorms in place
over the central OR terminals starting around 00Z Saturday. CAMs are
showing modest agreement in time and location for a threat of
isolated storms. Main hazards would be lightning and outflow winds.
&&
.FIRE WEATHER...The hot dry and unstable conditions will continue
across the forecast area over the next couple of days before
temperatures begin to cool starting on Sunday. Under these
conditions, existing large fires could see increased fire behavior
possibly leading to plume dominated fires. As such, a Fire Weather
Watch has been issued for zones 640 and 642 for the hot and unstable
conditions covering Friday through Saturday.
An approaching weak weather system from the southwest will trigger
some isolated thunderstorms over southwest and south central Oregon
Friday afternoon with some of this moving into central Oregon by
late afternoon and evening before dissipating overnight. This system
will again trigger thunderstorms over central Oregon on Saturday
that will then spread northeast into NE Oregon overnight and Sunday.
At this point the weak nature of this system leads this event to be
isolated thunderstorms but will be monitored for any need to upgrade
for some watch or warning highlights.
Overall, conditions are expected to turn cooler next week with some
possible rain showers midweek.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 56 96 57 94 / 0 0 0 0
ALW 57 98 61 98 / 0 0 0 0
PSC 59 98 63 99 / 0 0 0 0
YKM 57 96 63 96 / 0 0 0 0
HRI 57 99 61 98 / 0 0 0 0
ELN 52 96 57 94 / 0 0 0 0
RDM 49 95 57 91 / 0 0 20 10
LGD 51 94 57 94 / 0 0 0 0
GCD 54 97 59 93 / 0 0 0 0
DLS 58 100 63 98 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 9 PM PDT Saturday for ORZ041-044-049-502-503-
505>511.
Fire Weather Watch from Friday afternoon through Saturday
evening for ORZ640-642.
WA...Heat Advisory until 9 PM PDT Saturday for WAZ024-026>030-521-523.
&&
$$
SHORT TERM...91
LONG TERM....97
AVIATION...80