Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/06/23
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
622 PM CDT Tue Sep 5 2023
.UPDATE...
Issued at 619 PM CDT Tue Sep 5 2023
Cancelled the wind advisory a little early as strongest wind gusts
are now topping out around 35 mph. Winds will continue to diminish
through the evening. No other major changes are planned to the
current forecast.
&&
.SHORT TERM...(This Evening through Wednesday Night)
Issued at 320 PM CDT Tue Sep 5 2023
Forecast challenges include timing the decrease in coverage and
speed of strong northerly winds early this evening, along with areal
coverage and timing of showers (w/ embedded thunder) through late
this evening. There is also smoke aloft, and near the surface to
contend with once more.
At 2 PM CDT, skies are cloudy or on their way to becoming cloudy,
due to a low pressure system churning over the Dakotas. Scattered to
numerous showers w/ some embedded occasional thunder have been
hanging out over portions of central and north central South Dakota
for several hours within the deformation zone/TROWAl-forcing region
of this low pressure system. And, northerly surface winds across
that same area have been running up into wind advisory category for
a few hours now (sustained 25 to 35 mph with gusts to 45 or higher).
Temperatures where it`s been sunny more than it`s been cloudy have
warmed into the mid to upper 70s (even 80F or higher in a few
locations south/east of Watertown). Where it`s been cloudy, rainy,
cold air advecting and windy, temperatures have not been able to
exceed the 60F degree threshold. Finally, smoke is quite evident on
satellite imagery, as well as at the surface with much of the
northern high plains surface observing network reporting visibility
between 1 mile and 4 miles. This smoke is working into the forecast
area (worst over forecast zones west of the James River valley at
this time).
Short range guidance has the showers dwindling/dissipating by 06Z
tonight. At the start of the tonight period, the strong northerly
winds across the Missouri River valley region should be ending. The
strong northerly winds that continue to slowly trudge eastward into
Minnesota will be diminishing some overnight with the loss of
daytime mixing. It will still be breezy over the Coteau into
Minnesota overnight, but the strongest of the strong winds should be
drawing down across the eastern half of the cwa by 06Z tonight. The
latest HRRR smoke model output shows the smoke layer aloft will
basically be over the entire CWA by 12Z Wednesday, with a similar
result for near surface smoke. Smoky/hazy conditions are expected
Wednesday into Wednesday night while winds are light and variable
with surface high pressure over the region.
Thee strong northerly winds happening now are bringing much cooler
air into the area. Low temperatures tonight and Wednesday night, and
high temperatures on Wednesday are forecast to be near to below
normal.
.LONG TERM...(Thursday through Tuesday)
Issued at 320 PM CDT Tue Sep 5 2023
The recent highly amplified flow pattern aloft has relaxed and
turned into a progressive, flattish setup over the CONUS, at least
for the time being. This should mean a return to more chances for
pcpn. West/northwesterly flow aloft will likely be the dominant
pattern through much of the period, and northwesterly flow aloft can
be tricky with timing/location of s/w energy. That said, there seems
to be good agreement between models for pcpn this weekend. Thus, NBM
pops look decent and are accepted. As for severe chances, they don`t
look particularly great with relatively low CAPE values during the
period. Shear values are also fairly low unless you head toward the
front range/high plains out west. By early next week, the main
baroclinic zone/LL front should have slid off south into the Central
Plains, with the highest probs for measurable rain shifting into the
IA/NE/KS/MO regions and even further south as sfc high pressure
nudges in from the north. Temperatures will start the period around
or perhaps a bit above normal, but then will trend below average for
the weekend and early next week due to more clouds/pcpn and sfc high
pressure building into the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 619 PM CDT Tue Sep 5 2023
Terminals KABR,KATY,KPIR,KMBG
Smoke from Canadian wildfires will continue to reduce vsby into
Wednesday. IFR vsby this evening is expected to improve to MVFR
late tonight. Cigs have all improved to VFR behind the showers.
Expect cigs at KABR and KATY to lift by 6z.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Wise
SHORT TERM...Dorn
LONG TERM...TDK
AVIATION...Wise
Area Forecast Discussion
National Weather Service La Crosse WI
659 PM CDT Tue Sep 5 2023
.DISCUSSION...(Tonight through Tuesday)
Issued at 215 PM CDT Tue Sep 5 2023
Key Messages:
- Cold front brings with it risk for strong to severe storms this
evening. Rain threat could linger through Wednesday, especially in
Wisconsin.
- Cooler weather returns behind front with next shot at rain or
storms early next week.
STORM RISK THIS AFTERNOON AND EVENING:
A short wave trough and associated cold front will cross the Upper
Midwest this evening/tonight bringing the chance for thunderstorms
(50 to 70%), with a few stronger storms possible - wind and hail are
the primary threats. Early morning clouds continue to dissipate and
shift east today allowing for boundary layer destabilization. Latest
RAP analysis soundings show around 1000-1500 surface-based CAPE;
however, an elevated mixed layer has left a capping inversion around
750mb. The associated convective inhibition is too large for a
surface-based parcel to lift through heating on its own, so
convection is expected to hold off for the next few hours. Surface
dewpoints are about as high now as they are expected to get, with no
moisture advection taking place.
Later this evening, the upper-level wave will continue to shift east
into western Minnesota. As it does, temperatures aloft begin to cool
as mid-level lapse rates increase. Due to the capping inversion,
storms will likely need the frontal boundary to initiate. The best
forcing and shear are displaced to the north of our forecast area,
which limits severe potential and storm longevity, even if/when
storms initiate along the cold front. Storms that fire along the
front are expected to initially move to the NE, which will move into
the frontal boundary - this will lead a small time window for any
isolated storm to become severe. The only other option for severe
storm potential will be tied to potential cold pool developments
where severe threat will transition more to wind than hail.
PRECIPITATION CHANCES INTO WEDNESDAY BUT COOLER:
As the short wave continues eastward progress tomorrow, could still
see some wrap around or post-frontal /and much needed/ showers but
most will notice the cooler temperatures and lower dew points most
significantly. After four days of heat, readings will be dropping to
below normal for at least a couple days.
With upper ridge axis centered more on desert southwest, Midwest
looks to remain on upper tier of broad ridge with almost a quiet
zonal flow setting up to close out the week. Even some hints,
especially in ECMWF ensembles, that could see a bit more ridging
into region and hence perhaps a little warmer than forecast. Some
solutions run a weak short wave into area Thursday night but most
maintain a dry forecast.
RAIN / STORM CHANCES BY EARLY NEXT WEEK:
Next bonafide rain chances start to ramp back up late in the weekend
when short wave trough could drop another front into region as
northerly branch in flow becomes a bit more dominant. With some
timing differences in medium range guidance, ensemble clusters in
fairly good agreement showing this evolution either late Sunday or
more likely early next week. Unclear that far out how much moisture
return we might see so even though adequate shear may be available,
unsure on the extent of storm threats that far out. Besides these
next precipitation chances, another plunge of cooler air could bring
that fall feeling back into the air.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 655 PM CDT Tue Sep 5 2023
Scattered showers and thunderstorms have developed ahead of a cold
front moving through parts of southeast Minnesota early this
evening. Will continue to mention TSRA/VCTS/VCSH at both sites
during the evening. VFR ceilings with patch MVFR ceilings and
visibilities under the stronger storms. South winds veer to the
southwest and northwest behind the cold front with deteriorating
ceilings to MVFR/IFR after 06Z at KRST and after 10Z at KLSE. MVFR
ceilings continue Wednesday with northwest winds 10 to 20kts
gusting 20 to 30kts.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...JAW/Shea
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Caribou ME
923 PM EDT Tue Sep 5 2023
.SYNOPSIS...
High pressure will build across the region through Wednesday
then move east Thursday. Low pressure will approach from the
west late Thursday and Friday, then begin to slowly cross the
region over the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
9:20 PM Update...The sky is mostly clear except for the haze of
forest fire smoke. Temperatures have cooled into the 60s over
the north where a lighter gradient has allowed cooling. Temps
remain in the 70s over the south. Modified mid evening
temperatures across the region to reflect this. Otherwise, no
major changes needed this hour.
High pressure will continue to influence the region tonight and
into Wednesday. For tonight, upper air model soundings show the
inversion setting up before sunset across the region. However,
post tropical cyclone Idalia will continue to influence
northerly flow above this inversion. If last night was any clue
to how the marine layer will behave with this type of set up,
then expect the marine layer to remain offshore. SREF and HREF
are in agreement with this assessment, so decided to remove
patchy fog from the waters for the night due to the flow. For
the rest of the region, warm, humid conditions with light winds
will help develop patchy fog across the region, especially in
lower terrain due to radiational cooling. The flow with the jet
across Canada will bring smoke from the fires in British
Columbia into northern Maine tonight. Due to the shallow
inversion and HRRR smoke forecast, decided to include patchy
smoke into the forecast.
For Wednesday, patchy fog will burn off fairly quickly after
sunrise, but may remain in the North Woods a little longer.
Temps are expected to quickly increase into the mid 80s with the
ample sunshine and calm N winds. Coupled with the high
dewpoints, apparent temps are expected to reach into the upper
80s to low 90s. The approaching system from the W and high temps
could help produce some afternoon showers, but model confidence
is low on the development, so decided to not include it in the
forecast.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Upper level high pressure will be over the area Wednesday night
with more patchy fog. The upper high then shifts east a touch
on Thursday. With a weak approaching shortwave trough on
Thursday and slight cooling aloft, we should see the afternoon
shower/storm activity that we haven’t been seeing in recent
days. Instability and shear isn’t anything special, but should
be enough for isolated to scattered showers and storms pretty
much anywhere except the immediate coast. Remaining very warm
and muggy on Thursday with highs generally in the mid 80s and
dewpoints around 70. Fairly light winds Thursday, mainly out of
the south.
Thursday night into Friday, look for the marine layer to get a
bit stronger, with somewhat unstable mid level SW flow over the
area and a bit of an increased low level southerly flow. This
will result in a strengthening marine layer with increased
fog/low clouds especially overnight into Friday morning. A cold
front will be approaching NW Maine Friday, and look for a
better chance of showers and storms (60-70 percent) especially
in the afternoon. Lesser chances of showers/storms Downeast due
to the stronger marine layer. Still muggy Friday with dewpoints
around 70. Perhaps just a few degrees not as warm, but still
much warmer than average.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Saturday and Saturday night, look for not much change from
Friday, with unstable SW flow and a very slow-moving cold front
approaching from the NW, perhaps moving into Northern Maine.
Could be showers at any time through the weekend, but the better
chance appears to be Sunday (50-70%...highest in the north) as
the front begins to move through the area from NW to SE. Some
uncertainty on timing of the cold front however. Airmass
remaining fairly muggy through the weekend. Still warm with low
80s, but cooling a bit to the 70s Sunday thanks to more clouds
and better rain chances, and probable movement of cold front
through the area. Thunderstorms are possible this weekend as
well, but don’t anticipate any of them to be on the stronger
side.
Considerably lower confidence in the forecast beginning Monday.
Some models/ensembles clear the cold front SE of the area and
bring us drier weather Monday through Wednesday, while other
models keep the front close enough to continue the wet weather
through Wednesday. Went with a compromise approach of precip
chances dropping from around 40% Monday to 20% Wednesday, with
temperatures fairly close to average.
Another wildcard from late Wednesday is what may happen with
Lee. Most models tend to curve Lee to our east toward
Nova Scotia or Newfoundland, but some models/ensembles do move
Lee our way, and/or draw moisture north well ahead of Lee toward
our area. Tons of scenarios could play out, with most scenarios
being no big deal for us, but it is something we should be
watching.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: VFR for all terminals this evening. Then conditions
in the north expected to lower to MVFR/IFR in patchy fog after
midnight. Patchy smoke in the north could also lower vsby
tonight. For Wednesday, VFR conditions for all terminals once
the fog burns off. Light N winds tonight will increase slightly
on Wednesday to around 5 kts.
SHORT TERM:
Wednesday Night and Thursday...Light wind and generally VFR,
except patchy fog possible in valleys which could impact any TAF
site late Wed night/Thu morning. Isolated storms Thursday
afternoon could also impact any terminal.
Thursday Night through Sunday...
Generally S wind 5-15 kts. Conditions during this period will be
greatly variable, with generally MVFR/IFR during the night and
early morning hours, and generally VFR during the afternoon and
early evening hours. The greatest chance for persistent MVFR/IFR
conditions will be near the Downeast coast. Afternoon/early
evening thunderstorms are possible any day, mainly north of BGR.
&&
.MARINE...
NEAR TERM: Winds and seas will remain below SCA conditions for
tonight and Wednesday.
SHORT TERM: Conditions remaining below small craft through the
weekend. However, areas of fog are expected over the waters
especially from Thursday night on.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...Bloomer/LaFlash
Short Term...Foisy
Long Term...Foisy
Aviation...Bloomer/LaFlash/Foisy
Marine...Bloomer/LaFlash/Foisy
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Tue Sep 5 2023
.AVIATION...
Benign conditions overnight as greater stability briefly takes hold
in the wake of earlier convection. Substantial level of high cloud
debris will continue to mark conditions during this time. Winds
remain modest from the south tonight, precluding a concern for fog
despite the elevated dewpoint. Weakening mid level wave will track
through midday Wednesday, offering an initial window for possible
convective development. Greater convective potential will exist
late afternoon into the evening hours as a low pressure system
advances across the area. Confidence in timing and duration remains
quite low at this stage, with refinement of shower/thunderstorm
detail likely going forward.
For DTW...Conditions become more unsettled on Wednesday as a low
pressure system enters the region. This will bring the potential for
showers and thunderstorms both during the daylight hours and into
the early portion of Wednesday night. Forecast will continue to
highlight a window early in the day /15z-18z/, with a secondary
period toward evening. Additional revisions likely with confidence
very low.
.DTW THRESHOLD PROBABILITIES...
* Low for ceilings at or below 5000 feet tonight and Wednesday
morning. Medium Wednesday afternoon and evening.
* Low for thunderstorms Wednesday afternoon into early Wednesday
night.
&&
.PREV DISCUSSION...
Issued at 259 PM EDT Tue Sep 5 2023
DISCUSSION...
Key Messages
- A chance for isolated showers and thunderstorms exists this
afternoon for areas generally along and west of the US 23 and I 75
corridors. Many to most areas will remain dry. No severe weather is
expected.
- Showers and thunderstorm are likely Wednesday and Wednesday night
as a slow moving low pressure system pushes into Lower Michigan. Low
confidence in timing and duration of activity. Localized heavy
rainfall is possible. An isolated strong to severe thunderstorm with
gusty winds will be possible during the late afternoon and early
evening.
- Potentially grungy Thursday and/or Friday. High uncertainty and
low confidence in how fast the upper level low pressure system gets
swept out of the region.
- Much cooler next weekend Saturday and Sunday. Current data
suggests daytime temperatures will struggle to climb much above 70
degrees.
Agitated cumulus streets in place over Southeast Michigan this
afternoon. Anticyclonic curvature to the streets speaks to the
influence locally of the eastern NOAM omega block. Forecast and
observational data including the HREF and RAP based Mesoanalysis
suggests that instability this afternoon will top out with MLCAPES
around 1500-2000 J/kg. Vertical extent of the cumulus here early is
up against a capping inversion at 8.0 kft agl. That will change
during the late afternoon as all soundings suggest temperatures of
13C at 700mb will cool less than 10C. NWP signal is not great for
much convective development today with synoptic scale support for
ascent non-existent. In fact, could be looking at a period of
notable anticyclonic vorticity advection during peak heating. EPS
members are notably lacking in QPF with a good percentage of members
limited to trace amounts. Best potential to witness any activity
could be along and to the west of the US 23 and I 75 corridors.
Brief heavy downpours will be possible but no severe weather
expected.
First signs of changeover to cyclonic influence occurs after 12Z
Wednesday as a secondary thetae/moisture surge lifts into Southeast
Michigan. Good linkage of a meridional moisture transport axis to
absolute vorticity maximum. NWP model signal looks like just some
convective remnants arriving possibly earlier in the 12-15Z window
due to the diurnal minimum in surface based instability. Arrival of
potential vorticity support with increasing convergence and moisture
then brings precipitation chances into the likely category. Some
signal that things could wait until after 00Z Thursday due lagged
upper level jet forcing and organizing cold front, however, do thing
the models are underdone wrt to coverage of precipitation Wednesday
afternoon. Somewhat surprising but 800-600mb lapse rates are
forecasted to be steeper which should be good for MLCAPES of 2000
J/kg during the late afternoon and early evening. Best potential for
a strong to severe thunderstorm will likely wait for activity along
the cold front as higher shear (0-6km bulk shear increasing to 30
knots) between 00-03Z.
A lot of uncertainty then exists for how long shower activity will
hang around Southeast Michigan for Thursday and Friday. ECMWF output
has been very consistent in keeping absolute vorticity center and
closed H3 heights stalled out over the state. The current forecast
reads chance PoPs. The difficulty with the Friday period is the
split in EPS members with dry vs. relatively wet solutions.
Reasonable confidence in the main cold front pushing through
Southeast Michigan around midday Friday. Highs Saturday are expected
to top out around 70 degrees with perhaps low 70s Downriver Sunday.
MARINE...
Southerly wind of 10 to 15 kt continues through today into tomorrow
as a low pressure system slowly approaches the Great Lakes from the
west. Isolated to widely scattered showers/storms will be possible
through this evening with more numerous showers/storms expected on
Wednesday as the system moves in. An isolated strong to severe storm
will be possible Wednesday. The center of the low tracks overhead
Wednesday night into Thursday morning with cooler north to northeast
flow settling in on Thursday as the low departs. Wind looks to hold
predominantly northerly and at 15 kt or below through the end of the
week, keeping marine conditions overall quiet.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....MR
DISCUSSION...CB
MARINE.......TF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Forks ND
616 PM CDT Tue Sep 5 2023
.UPDATE...
Issued at 616 PM CDT Tue Sep 5 2023
The Mayville radar shows a few echoes over eastern North Dakota
and portions of west central Minnesota. There is still some
lightning activity in this area, but what remains is shifting
into Clay County Minnesota now. This lingering shower activity
will be a little slow to end this evening, but not much
precipitation is expected from it. Otherwise, anticipate the gusty
north winds to decrease this evening, along with some of the low
cloud cover. Models show most of the Red River Valley clearing by
midnight, but pretty much stall the clearing from Lake of the
Woods to Bemidji to Wadena. These areas may not clear out until
late Wednesday morning. The smoke is a challenging one, but it
also looks like that is here to stay tonight. The Minnesota
Pollution Control Agency updated its latest statement to show red
or unhealthy air quality in effect tonight through 6 pm Wednesday.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 249 PM CDT Tue Sep 5 2023
-If we get any strong to severe storms in our area, it will be in
the next few hours along the far eastern tier of counties.
-Lingering showers and thunderstorms should taper off before
midnight
-Smoke lingers a bit longer before decreasing tomorrow.
Showers and thunderstorms continue across central MN ahead of the
cold front, with weaker showers further west over the Devils Lake
Basin with the main trough. Clouds and showers have kept
instability even ahead of the cold front in Wadena and Hubbard
counties on the lower side. However, there is some breaks in the
clouds starting across our far southeastern counties, and Staples
has risen to 75 temp over 70 dew point. Shear is pretty strong in
the 45 to 50 kt range, and if anything does develop we cannot rule
out cells becoming quickly severe before moving east. HREF has
some 10 to 30 percent probabilities of updraft helicity tracks in
our southeast, although some of the newer CAMs runs break out
stronger convection just across the CWA border by early evening.
Some isolated severe storms are possible before 01Z, mainly
producing hail up to quarters and 60 mph gusts before moving out
of the area.
As stronger convection moves into central and northeastern MN,
showers will linger across far eastern ND and western MN as the
main trough moves through. Showers should taper off from west to
east this evening, with fairly light amounts and low impacts.
Winds will also come down and there could be some clearing at
least in our western counties. Could see some temps dip into the
low to mid 40s, quite a change from the 90s a few days ago. HRRR
and RAP both have some decent smoke concentrations moving through
tonight, before starting to decrease from north to south during
the day tomorrow. Wednesday should be dry and cool with surface
high pressure, as afternoon temps stay in the 60s to low 70s.
.LONG TERM...(Thursday through Tuesday)
Issued at 249 PM CDT Tue Sep 5 2023
Thursday through Sunday...Upper ridging builds into the central
CONUS for the end of the work week, although heights over the
Northern Plains will not be nearly as high as they were last week
and temps will be closer to seasonal averages instead of way above.
Temperatures will be knocked back a bit behind a weak frontal
boundary moving through late Friday, with weekend readings in the
upper 60s to low 70s for highs. The next chance for precipitation
will be Saturday into Sunday as a shortwave moves into the Northern
Plains and then the Upper Midwest. Deep moisture return seems
unlikely, and NBM average CAPE values stay mostly in the double
digits, maybe a few hundred J/kg on the higher outliers. M climate
percentiles are not showing a huge signal for a wet pattern, but
there is enough ensemble members bringing some precip to include 20-
40 percent POPs.
Monday and Tuesday...The shortwave that passes through will phase
with a more northerly wave and amplify over the Great Lakes. These
will leave our area in northwesterly flow aloft, with fairly dry
conditions and slightly below average temperatures.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 616 PM CDT Tue Sep 5 2023
Lots of aviation challenges. First is the gusty north wind.
Luckily, that appears like it will end by early to mid evening.
Next is the low cloud cover. Ceilings have risen to VFR now at
KDVL and KGFK and they should continue to at KFAR and KTVF this
evening. KBJI is the question mark. Guidance shows the low clouds
may hold tough around KBJI until possibly around the noon hour
Wednesday. Finally, smoke and low visibilities. Guidance for
smoke really doesn`t show much change across the FA until maybe
sometime on Wednesday, from east to west. For that reason, have
basically kept visibilities where they are currently at until
sometime Wednesday morning. Really hard to see them improving
overnight, but would not be surprised if they lower even more.
They could also combine with some late night fog and result in
even lower visibilities by sunrise. Will take another look at that
possibility with the 06z set of TAFs.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Godon
SHORT TERM...JR
LONG TERM...JR
AVIATION...Godon
Area Forecast Discussion
National Weather Service Gray ME
1109 PM EDT Tue Sep 5 2023
.SYNOPSIS...
Deep layer ridging and surface high pressure will continue to
build across the Northeast through the middle of the week with
well above average temperatures and dry conditions. Fog is
likely to develop at night. Shower and perhaps thunderstorm
chances will then increase late Thursday through the upcoming
weekend along with a return to cooler temperatures.
&&
.NEAR TERM /OVERNIGHT/...
1108 PM Update...Another round of minor tweaks to the forecast,
this time to incorporate latest 00Z runs of hires data. The
humid night continues with visibility jumping around at are more
sheltered interior valley sites. A weak inverted trough pivoting
around a cut-off low south of Nova Scotia is tracking through
out area right now... with a little bit of mid-level cloud cover
and light flow accompanying it. This will mitigate or at least
delay widespread fog outside of those aforementioned sheltered
interior valleys.
715 PM Update...Little to report at this hour, other than it
remains quite humid. This is starting to become evident in some
surface observations, with some early instances of BR in some
northern locations (which may have some smoke contribution)...
but also with BCFG at Mount Washington. Update at this time
focused on overnight fog to utilize MOS, to hit valleys
especially hard.
Previously...Warm and humid conditions remain in the region
this afternoon and tonight. Once the sun goes down, temps
retreat, but anticipate a very warm night with lows only getting
into the upper 60s or lower 70s. This can compound over the
next warm day/night cycles resulting in additional heat stress.
Fog is expected to again develop tonight, mainly in the valleys.
Marine stratus/fog underperformed today, and am not too bullish
on additional development there.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
Another hot day expected Wednesday. If today`s mixing is any
story to tell for tomorrow, it was pretty weak. With a very
similar environment expected, have extended the Heat Advisory
into Wednesday for the same area in southern NH. There may be a
little more robust cloud development tomorrow, and can`t rule
out a light sprinkle. Capping and dry levels just off the
surface could mitigate anything actually reaching the surface.
HRRR and NAMnest guidance depicts a sea breeze overtaking a good
portion of the coast mid afternoon, but this may also create a
pooling of dewpoints on the front edge causing some pools of
very uncomfortable conditions with brief heat index spikes.
Behind the sea breeze, especially right along the coast, it
should be pleasant, taking the edge off the hot temps inland.
Much like tonight`s forecast, Wed night also looks warm with
temps falling into the mid 60s to around 70.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Overview
Hot weather continues through the end of the week. Scattered
showers and thunderstorms are possible towards the end of the
week and then through the weekend. A cold front crosses the
region Monday night with temperature becoming much more
seasonable at the start of the week.
Details:
Mostly clear skies and calm winds Thursday morning should allow
for destabilization across the region. Temperatures will heat
up rapidly as warm air continues to sit in place and continue to
get warmed by intense sunlight. Temperatures are anticipated to
approach 90F Thursday, with dewpoints near 70F. Humidity will
feel oppressive and heat indices may exceed 100F locally in
Southern New Hampshire. Heat Advisory criteria may be reached
along the I93 corridor up to Concord and in interior Rockingham
county.
A non-zero chance for thunderstorms is likely Thursday as well.
Expected intense heat will provide ample potential energy for
thunderstorms to develop. However, it does not appear likely
that storms will be impactful due to a lack of forcing, and
minimal wind shear. At this time, showers and thunderstorms are
possible along the CT river and in the White Mountains, with a
diminishing front likely not making it to the coast until
Friday.
A warm, but dry onshore flow initiates on Friday. The dry flow
from the Bermuda High should keep temperatures warm and prevent
destabilization across most of New Hampshire and Maine. An
isolated threat for a brief shower or thunderstorm does exist in
western New Hampshire and along the Canadian border.
Troughing returns for Saturday and should bring temperatures
closer to average. An upper level low over the Canadian
Maritimes could allow for the development of some scattered
showers across the region. Showers become more widespread as the
weekend closes. Widespread showers continue through most of the
day Monday with the upper-level low finally exiting the region
overnight Monday into Tuesday.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Short Term...VFR with light winds. Will see fog develop in
valley locations tonight once again. This will result in after
midnight vis/ceiling restrictions down to IFR/LIFR. Fog should
become patchy by 9am local. VFR Wed with light winds continuing
Wednesday, with a similar fog threat Wed night.
Long Term...Thursday morning starts out foggy along the coast
and north of the mountains. Patchy fog and LIFR flight
restrictions are possible at LEB, HIE, PWM, and RKD. Fog will
persist through the day along the coast, with fog lifting and
thunderstorms moving down into northern NH and ME from Canada in
the afternoon. IFR flight restrictions are possible at sites
impacted by thunderstorms and coastal sites. Scattered showers
and thunderstorms continue through the day on Friday and should
keep ceilings lower (MVFR) across the interior. Drier air moves
into the coast and should keep the coastal areas dry and bring
VFR flight restrictions to PWM, PSM, RKD on Friday afternoon.
Scattered showers and thunderstorms continue through the weekend
and into early next week, with MVFR flight restrictions
possible across the region. Consistent light winds from the
south will persist through the entire forecast period, with
winds slightly stronger along the coast.
&&
.MARINE...
Short Term...SCA continues this evening for waves on the outer
waters. Continue to see long period swell at nearby buoys, and
would expect moderate rip current risk in the shallows. With
strong ridge overhead, expect light winds to continue.
Long Term...Winds will be out of the SSW from 5-15kts from
Thursday through early next week. AM patchy fog could skew
visibility over the coast and open waters. An isolated shower or
thunderstorm is possible overnight Thursday and into Friday.
1-3 foot waves are expected across all marine zones. Isolated
showers return for the weekend with 2-3 foot waves expected.
Wave heights increase to 3-5 feet over the open waters on Monday
with 1-2 feet waves in Casco and Penobscot Bays.
&&
.CLIMATE...
RECORD HIGH TEMPERATURES POSSIBLE...
Tuesday (9/5) Wednesday (9/6) Thursday (9/7)
90F (1971)92F (2018) 95F (1945) --> Portland, ME
88F (1971) 88F (1998) 90F (2007) --> Augusta, ME
91F (2018) 92F (2018) 96F (1881) --> Concord, NH
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...Heat Advisory until 6 PM EDT Wednesday for NHZ007-008-011>013-
015.
MARINE...None.
&&
$$
UPDATE...Casey
NEAR/SHORT TERM...Cornwell
LONG TERM...Legro/Palmer
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1059 PM CDT Tue Sep 5 2023
.SHORT TERM... (Through Late Wednesday Night)
Issued at 236 PM CDT Tue Sep 5 2023
The main concern in the short term is the potential for a few severe
thunderstorms capable of producing damaging winds and perhaps large
hail through the early hours into the the overnight over parts of
the area.
Visible satellite and radar imagery is showing a well defined
circulation over south central Illinois with an upper low that the
RAP shows lifting northeast by early this evening. Latest SPC
mesoanalysis is showing MLCAPES of 2000-2500+ J/kg over western
Missouri ahead of a cold front that HREF shows moving southeast
across the CWA tonight. Latest runs of the CAMS including the HRRR
have been consistent in developing thunderstorms ahead of this front
over central and northeast Missouri by early this evening and then
shifting southeastward late this evening and overnight with the
front. There will be some potential for a few of these storms to be
severe, particularly over parts of southeast and central Missouri
where capping will be the weakest and the instability will be the
greatest. Damaging winds will be the primary threat, though large
hail will also be possible. The showers and thunderstorms will move
south of the CWA by late tonight as the front moves out. A upper
ridge will move into the area for Wednesday and Wednesday night
supplying dry weather.
Temperatures will be at or below normal on Wednesday as cooler air
moves in behind the front.
Britt
.LONG TERM... (Thursday through Next Tuesday)
Issued at 236 PM CDT Tue Sep 5 2023
The latest ensemble guidance continues to show very few members with
precipitation from Thursday night into Sunday as a surface high
moves across the area underneath northwesterly flow aloft. The
number of members showing rain increases as an upper trough moves
southeast through the Midwest. Temperatures Friday through Monday
will be close to seasonal normals with 850mb temperatures around
15C. Temperatures will fall off below normal by Tuesday as winds
turn out of the north and with the increase in clouds with the
upper trough.
Britt
&&
.AVIATION... (For the 06z TAFs through 06z Wednesday Night)
Issued at 1054 PM CDT Tue Sep 5 2023
The probability of impactful thunderstorms is decreasing at all
terminals for the remainder of the evening. While a few lightning
strikes will be possible in the vicinity of the St. Louis metro
area near the start of the 06Z TAF cycle, thunderstorms are not
expected produce much more than light rain and an occasional
strike of lightning, while stronger storms remain south of local
terminals.
Overnight, a cold front will push through the area, causing winds
to shift to westerly, and eventually northwesterly by morning.
Wind speeds will increase and remain gusty through the afternoon,
and diminish quickly in the evening.
BRC
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
749 PM EDT Tue Sep 5 2023
.UPDATE...
Issued at 749 PM EDT TUE SEP 5 2023
Line of strong/severe storms is crossing western Lake Superior with
a ship observation of 56kt gust. These storms are tracking
northeastward and should not impact land on their current trajectory
except for Isle Royale by around 9 pm EDT. Elsewhere, storms are
developing along a well-defined, E-W oriented outflow boundary over
northern WI. Will need to watch the eastern part of this boundary as
it approaches Ironwood over the next couple of hours, but midlevel
winds support storm motion to the northeast, so development may be
more delayed than it would first appear. Ample instability is in
place over the western UP with SPC mesoanalysis showing 1500-2000
J/kg MLCAPE. However, effective bulk shear is weak at only around 20
kt, so longevity of storms is in question should they develop.
Deep-layer forcing will increase through the night as a shortwave
trough rotates in from the southwest. Due to the geometry of this
system, it will take quite a while for the better forcing to work
eastward across the UP. The trend in the CAMs has been a bit slower
for the more widespread rain and thunderstorms to move into the
western and central UP; PoPs have been adjusted accordingly to delay
likely PoPs to 02-04Z over the western UP and Keweenaw, and 06-08Z
for Marquette-Dickinson. Strong/borderline severe storms with large
hail and strong wind still can`t be ruled out, with chances
decreasing with eastward extent as low-level forcing washes out and
instability wanes through the night. As the system slows down, heavy
rainfall remains a possibility, with HREF Probability-Matched Mean
showing 1-2" from 00-06Z over Gogebic/Ontonagon Counties. This could
cause some ponding/minor flooding in low-lying areas, but this area
has also been very dry recently, so that should mitigate a more
extensive flooding threat.
&&
.SHORT TERM...(This evening through Tonight)
Issued at 304 PM EDT TUE SEP 5 2023
Mid and upper level cloud cover continues to stream across the
western half of the UP with an initial weaker shortwave rippling
northward through WI. This is touching off some weak radar returns
that don`t appear to be reaching the ground with very dry lower to
midlevels in soundings. Still, will not totally rule out some stray
convection across the UP this afternoon with some cumulus also
apparent on satellite. Temperatures well into the 80s and dewpoints
in the lower 70s have contributed to plenty of destabilization, with
SBCAPE analyzed at up to 2000 to 3000 j/kg and lower level lapse
rates looking pretty healthy.
Better synoptic forcing arrives into the evening with a sharp cold
front over central Minnesota. Convection developing along it has
continued to drift northeastward amid robust SW pre-frontal flow. As
the boundary continues to track eastward, showers and storms reach
the arrowhead of MN and western Lake Superior closer to sunset,
reaching the western UP between 00-03Z and continuing to press
eastward the rest of the night. We`ll be running out of daylight as
storms roll in, with CAPE decreasing to around 1000-2000j/kg. Though
shear is quite high across the Dakotas, flow aloft is rather lighter
across the Great Lakes, with bulk shear only around 20 to 30 knots
as the boundary arrives. However, while severe parameters aren`t
extraordinary, robust synoptic forcing should be enough to keep the
potential for strong storms going at least across the western UP
into the first half of the night. The main concerns would be gusty
winds and hail, though there is also the potential for excessive
rainfall with PWATs over 1.5 inches and bulk shear vectors looking
boundary-parallel.
Otherwise, as the low currently over MN drifts eastward overnight,
southerly winds should continue to lighten up from west to east
before turning to the north and increasing behind the front. Expect
another mild night with lows ranging in the 60s.
.LONG TERM...(Wednesday through Tuesday)
Issued at 304 PM EDT TUE SEP 5 2023
Key Messages:
-Low pressure tracks just south of the UP, bringing rain and thunder
chances thru Friday AM
-Much cooler Thursday with lingering cloudiness and lake effect
sprinkles/rain showers
-Quieter weather Friday and on with more fall-like temperatures ahead
A slow-moving closed low is the primary weather-maker through
Thursday and perhaps lingering into Friday too. Showers and
thunderstorms should be ongoing Wednesday morning while the cold
front tracks southeast across the Copper Country. The front will
make slow and steady progress across the area on Wednesday as the
surface low remains around 1000mb and arrives in Northern Lower
Michigan in the evening hours. Among the HREF guidance, only the
HRRR shows ongoing continued vigorous convection during the day, so
the expectation is that while a few thunderstorms may have the
potential to be strong, the vast majority, if not all of the storms,
should remain sub-severe. However, due to the slow storm motion
combined with strong forcing with PWATs in excess of 1.75 inches, a
marginal excessive rainfall risk is present as highlighted by the
WPC. Despite the long duration of showers, HREF probability matched
mean 6-hour rain rates are only around an inch at most, especially
with much of the UP being well-under normal in terms of recent
precipitation, so the flash flooding threat is limited. Behind the
front, temperatures cool into the 50s with blustery north-northeast
winds reminding us what fall feels like. With the continued cloud
cover preventing radiational heating following the frontal passage,
the high on Thursday may approach record cool high temperature
territory, with the NBM 10th percentile showing highs in the low 50s
inland from Lake Superior and the 50th percentile only being in the
mid 50s for those same locations. Model soundings indicate a shallow
cool air mass with lake-induced inversion heights peaking in the 2-3
kft range and saturation extending through at least 5 kft. This
suggests fairly high confidence for lake effect rain showers and/or
drizzle near Lake Superior, possibly lasting all the way through
Thursday night in the most favored upslope locations.
Deterministic guidance has an unexpectedly high spread regarding the
progression of the midlevel trough at 60 hours from model initiation
this morning. Models seem to be trending less progressive and
keeping the trough around the southern Ontario vicinity longer. This
may keep cloud cover in the region longer and keep the diurnal
temperature curve moderated, though model consensus shows skies
clearing by Friday as a surface high is expected to move over the
area for the weekend. This does lead to some frost potential for the
typical cold spots in the interior west, though confidence remains
low as long as spread is high in the model solutions.
NBM spread is actually quite low in keeping highs in the 60s for
next week, much more in line with the more fall-like conditions that
are expected of this time of year. Precip chances return to the
forecast later Sunday into the next week as a weak shortwave of some
flavor is expected to ride the zonal flow aloft and arrive in the
region, though timing and magnitude of impacts varies greatly
ensemble member to ensemble member, so just keeping the slight
chance PoPs in there that the NBM presents.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 749 PM EDT TUE SEP 5 2023
Main aviation concerns are thunderstorm potential overnight and IFR
cigs late tonight into Wednesday. There is a low (20%) chance of
thunderstorms at IWD from 00-02Z, increasing to around 50% from 02-
05Z. Storms could result in gusty winds and hail as well as heavy
downpours reducing vsby to IFR. TEMPO was included to address this
possibility, but there is still uncertainty in timing. At CMX, the
most likely timeframe for TS is 04-07Z, with gusty winds, hail, and
heavy downpours a threat as well. Confidence in TS is lower at SAW,
so left VCTS mention 07-10Z.
Cold advection in the wake of the rain and storms will trap moisture
near the surface and result in low conditions for late tonight into
much of Wednesday. MVFR vsby and IFR/MVFR cigs can be expected.
Showers/drizzle will continue.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 304 PM EDT TUE SEP 5 2023
Southerly winds of 20-25 kt are ongoing across Lake Superior this
afternoon as a low advances towards the lake from the Northern
Plains. A strong cold front moves onto the northwestern lake by
Wednesday morning then tracks southeast across the rest of the
lake by late Wednesday night. North-northeast gales >33 kts are
likely (>80%) behind the front across north-central portions of
the lake late Wednesday afternoon through Wednesday night with low
chances (~20%) for moderate gales >40 kts. Chances for gales are
lower across the western (30-40%) and especially eastern (<20%)
portions of the lake. NNE winds diminish to 25 knots or less by
Thursday evening then to 20 knots or less late Thursday night as
surface ridging moves back over the lake.
Thunderstorm chances move over western Lake Superior late on Tuesday
then spread across the entire lake Tuesday night before ending
Thursday morning. Some strong to severe storms are possible,
especially Tuesday night into Wednesday morning over the western
portions of the lake. In addition, patches of dense fog may occur
within the increasingly humid air mass near and ahead of Wednesday`s
cold front.
&&
.CLIMATE...
Issued at 304 PM EDT TUE SEP 5 2023
Record High Temps at the NWS Office in Negaunee:
Sep. 5: 88 (1998, 2007, 2023)
Record warm Low Temps at the NWS Office in Negaunee:
Sep. 5: 65 (1971)
Record cold High Temps at the NWS Office in Negaunee:
Sep. 7: 52 (1979)
Period of record: 1961-present
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Warning from 5 PM Wednesday to 2 AM EDT Thursday for
LSZ242>244.
Gale Warning from noon Wednesday to 11 AM EDT Thursday for
LSZ263-264.
Lake Michigan...
None.
&&
$$
UPDATE...Thompson
SHORT TERM...LC
LONG TERM...GS
AVIATION...Thompson
MARINE...GS
CLIMATE...GS
Area Forecast Discussion
National Weather Service Nashville TN
806 PM CDT Tue Sep 5 2023
...New UPDATE...
.UPDATE...
Issued at 801 PM CDT Tue Sep 5 2023
Latest radar imagery shows an area of light rain and a few
thunderstorms continues across our western half, along and behind
a gust front from the earlier widespread storms. This activity
will continue eastward to the I-65 corridor but diminish with time
due to the loss of daytime heating. Therefore have current chance
pops decreasing to none by midnight. Overnight, additional showers
and storms look to spread southeastward into the midstate per the
HRRR with pops increasing through sunrise into Wednesday morning,
with additional activity likely popping up Wednesday afternoon as
well. Made adjustments to pops for tonight/tomorrow based on this
reasoning. Made other tweaks to temps/dewpoints but rest of
forecast remains mostly on track.
&&
.SHORT TERM...
(This afternoon through Thursday Night)
Issued at 114 PM CDT Tue Sep 5 2023
Shortwave moving across western TN this afternoon. Out ahead of it,
scattered convection is ongoing and is beginning to pick up across
western areas of the mid state. This trend will continue through the
afternoon. Models dont completely rid themselves of overnight
activity so will keep a low pop going.
On Wednesday, we are in a marginal risk and it now covers the entire
mid state area. We are looking at a potential early morning impulse
that will play a key factor on how unstable we will get by
afternoon. Models are split on the late night and early morning
development. At any rate, it looks like the cold front will push
through Wednesday night. Thus, from midday and through the afternoon
hours, middle TN will be under the gun for the risk of damaging
winds and perhaps some hail. Precip amounts though Wednesday night
look like 0.75" far west to 0.2" east.
Following the fropa, moisture will still be somewhat slow to scour
out. Additionally, there will be an upstream impulse that could
trigger a few added showers Wednesday night, before the drier air
prevails and the precip ends. Thursday and Thursday night are
looking mostly clear and a little cooler.
For the near term temps, still quite warm but perhaps a degree or
two cooler on Thursday.
&&
.LONG TERM...
(Friday through next Tuesday)
Issued at 114 PM CDT Tue Sep 5 2023
In the extended forecast, we are looking at a dry northwesterly flow
regime as the northerly wind component is uniform vertically. There
still appears to be a second, but dry, fropa for Friday with the
northerly surface flow then picking up a touch. Sky cover looks
partial with perhaps some fair weather cu development each
afternoon. We do see a potentially potent mid week shortwave that
will approach. This could perhaps lead to our next precipitation
chance, long about Wednesday or so of next week.
For the extended temps, not seeing any solid cool push with the
expected late week fropas. Thermal troughing looks somewhat modest.
However, we should see more seasonal numbers with highs mid 80s and
lows 60 to 65. Thats very close to normal for early Sep. Otw,
tropics looking clean as we approach the climatological tropical
activity peak, the second week of Sep. We dont really see anything
effecting the Gulf or Atlantic coast area in the next 7 days.
Several Atlantic systems will likely veer to the north with
troughing setting up across the eastern U.S.. Not a good pattern
for the Bermuda area, but that`s long way off.
&&
.AVIATION...
(00Z TAFS)
Issued at 706 PM CDT Tue Sep 5 2023
VFR conditions continue for most sites, however, multiple rounds
of unsettled weather are expected this taf period. First round is
moving through now, primarily impacting CKV. Coverage is
uncertain overnight, so VCSH/VCTS is in at all sites. A front
will bring better storm coverage late morning/early afternoon
Wednesday with tempos in at all terminal sites for best timing of
impacts.
Outside of storms, winds are light and southerly. Some fog could
develop overnight tonight at SRB if clouds clear out enough.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 72 90 69 86 / 30 60 40 0
Clarksville 71 89 65 83 / 50 60 20 0
Crossville 64 82 64 79 / 0 30 40 10
Columbia 70 89 67 86 / 30 60 40 0
Cookeville 68 84 66 81 / 10 30 40 10
Jamestown 66 82 65 78 / 10 30 40 10
Lawrenceburg 69 87 67 85 / 30 60 40 0
Murfreesboro 70 90 67 87 / 20 60 30 0
Waverly 69 87 64 84 / 50 60 30 0
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Shamburger
SHORT TERM...21
LONG TERM....21
AVIATION.....Baggett
Area Forecast Discussion
National Weather Service Paducah KY
716 PM CDT Tue Sep 5 2023
.UPDATE...
Issued at 715 PM CDT Tue Sep 5 2023
Updated aviation discussion for 00Z TAFs.
&&
.SHORT TERM...(Tonight through Thursday night)
Issued at 239 PM CDT Tue Sep 5 2023
Primary focus in the short term resides with thunderstorm chances
through Wednesday afternoon. Beyond that, cooler and much less humid
air gives us an early taste of Fall!
A mid level disturbance is slowly spinning across the area, leading
to isolated to widely scattered showers and thunderstorms. Coverage
should increase this afternoon before dwindling early to mid
evening. Precipitable water values of 1.8 to 2" may lead to some
localized heavy rainfall amounts exceeding 1 inch. The lack of
appreciable wind shear through the column is negating much of a
severe threat with this activity.
Tonight into Wednesday, a secondary shortwave will slide east across
the Upper Midwest and Great Lakes with a trailing cold front
extending down into Missouri. Ahead of it, thunderstorms are
expected to develop late today into this evening across Missouri and
then congeal into an MCS and track east/southeastward towards our
region overnight. So after a bit of a lull, we anticipate a decaying
MCS of sorts to move into at least parts of the region after 05z.
Latest HRRR runs hold it together enough to give nearly the entire
region a decent soaking, with some localized heavy amounts possibly
exceeding 1 to 2". Can`t rule out a few flooding concerns overnight.
A marginal severe threat exists, primarily early in the night,
across southeast MO and southern IL. Main concern would likely be
some strong wind with any organized linear complex.
The remnants of the MCS may linger into mid morning on Wednesday.
Thereafter, much of the area may be dry the rest of the day. There
is some potential at isolated thunderstorm development across west
KY in the afternoon though before the frontal passage occurs. The
severe storm threat seems to have shifted south and east of our
area, with only our far southern Pennyrile still included in a Day 2
marginal.
Cooler and much less humid air filters into the region Wednesday
night into Thursday. Dewpoints currently in the low to mid 70s will
be replaced by upper 50s to lower 60s
.LONG TERM...(Friday through Tuesday)
Issued at 239 PM CDT Tue Sep 5 2023
The large scale pattern late this week into the weekend will feature
troughing across the TN Valley/Southeast U.S. and ridging across
NM/west TX. This places our region in northwest flow. Disturbances
migrating through the flow may touch off a few clouds, but that`s
about it given the lack of appreciable moisture.
The main story of the long term will be the cooler and much less
humid airmass that will be in place. High temperatures will top out
in the upper 70s to lower 80s with overnight lows in the upper 50s
to lower 60s through the period.
Towards the end of the period, a mid level wave is expected to dive
southward out of Canada into the Upper Midwest. Ensemble guidance
has been in good agreement with carving out a deepening trough later
Tuesday into Wednesday. A cold front may make passage across our
area late Tuesday into Tuesday night, accompanied by a few showers
or thunderstorms. This would then lead to a reinforcing shot of the
cooler, refreshing airmass, by Wednesday into Thursday of next
week.
&&
.AVIATION...
Issued at 715 PM CDT Tue Sep 5 2023
Predominantly VFR conditions are forecast over the next 24 hours.
Early evening shower and thunderstorm activity over southwest
Indiana and western Kentucky will exit the region. However, a cold
front will approach with another line of showers and thunderstorms
late tonight into early Wednesday morning. Most of Wednesday should
turn off dry, but lingering isolated showers cannot be ruled out
over mainly southwest Indiana and western Kentucky during the
afternoon. Southerly winds 5 to 10 knots will prevail, but a shift
to westerly will accompany frontal passage throughout Wednesday.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...RJP
SHORT TERM...SP
LONG TERM...SP
AVIATION...RJP
Area Forecast Discussion
National Weather Service Pendleton OR
703 PM PDT Tue Sep 5 2023
.UPDATE...Latest water vapor imagery shows a shortwave trough off
the BC coast and another off the CA coast, and these to features
will keep a dry SWLY flow aloft over the region the next couple of
days. The excessive heat associated with the pronounced upper
level high over the the SWRN states will stay suppressed to the
south of the region for the next several days with near normal
temperatures expected. The latest HRRR shows a couple of meager
showers over the northeast mountains Wednesday evening but
coverage and intensity will be limited. Latest NBM has TSTM
probabilities of 15-20% over Wallowa County from 21Z-03Z Wednesday.
Otherwise some high cirrus clouds will move across the region
especially central and north tonight and Wednesday and it will be
breezy in the Gorge and Kittitas Valley during the late afternoon
and evening on Wednesday. These two areas have about a 50% chance
of seeing sustained winds of 20 mph or greater after 21Z. 78
&&
.PREV DISCUSSION... /issued 403 PM PDT Tue Sep 5 2023/
SHORT TERM...Today through Thursday...Current radar and visible
satellite imagery showing dry conditions under mostly sunny skies as
transient ridging takes place over the area. This will keep skies
clear overnight tonight as temperatures drop into the low to mid 50s
across the Lower Columbia Basin, and low to mid 40s through Central
Oregon. Minimal weather concerns are anticipated through the
midweek, with a slight chance (0-15%) of showers and isolated
thunderstorms over Wallowa county and locally breezy afternoon winds
through the Eastern Gorge, Simcoe Highlands, and the Kittitas Valley
on Wednesday. Sustained wind speeds of 15 to 20 mph and gusts of up
to 30 mph out of the west will be possible across the aforementioned
areas. Confidence in these wind values is moderate to high (60-70%),
as the NBM highlights a 40-60% chance for the Eastern Gorge and a
48% chance for Ellensburg of experiencing wind gusts of 35 mph or
greater on Wednesday.
The transient ridging that is occurring locally today is associated
with a weak upper level shortwave that is traveling across
northern Nevada today before pushing into southern Idaho later
this evening. The main weather maker that will be providing the
elevated winds and showers/storm potential over Wallowa county is
associated with an upper level trough that is heading south along
the British Columbia coast today before pushing onshore and
through southern British Columbia on Wednesday. This passing
trough will tighten isobars as a 4-5mb gradient will develop
between Portland (PDX) and Spokane (GEG), leading to breezy
conditions through the Basin and the Kittitas Valley. Afternoon
minimum humidities are in the 20-30% range on Wednesday across the
aforementioned areas, however, the peak winds are expected to
occur during the evening hours - so fire concerns are low (<10%).
Very little moisture is associated with this passing trough as
SBCAPE stays between 200-300 J/kg, which keeps confidence rather
low (<15%) in any showers or storms occurring over the area on
Wednesday. This passing upper level trough will also lead to flow
aloft shifting from the west today to the southwest on Wednesday,
bumping up afternoon high temperatures a couple degrees and into
the upper 70s to low 80s across the Basin. The trough will
continue east into Alberta Wednesday night as a weak upper level
shortwave eyes the Pacific Northwest on Thursday, moving onshore
along the Oregon coast Thursday afternoon. There is more moisture
associated with this shortwave than the earlier trough on
Wednesday, allowing for a slight chance (15%) of showers over the
Northern Blue Mountains/Foothills late Thursday afternoon through
the late evening. SBCAPE is less than 50 J/kg, but Precipitable
Water (PW) is around 1 inch, which is 150% above normal for this
time of year. Minimal rain accumulations are expected, but higher
elevations could see as much as 0.02 inch. Conditions are expected
to continue to warm into the extended period, peaking over the
weekend. 75
LONG TERM...Friday through Tuesday...A mostly quiet weather pattern
is expected to dominate the region through the weekend extending
into early next week. Models remain in fairly good agreement on a
weak SW flow pattern aloft shifting ever so slightly more zonal as
we progress through the period. The light SW flow may trigger some
upslope rain showers for our eastern mountains Friday, before shower
chances increase more for the WA Cascades towards the latter half of
the period with more westerly flow aloft. Should any showers
develop, however, they would be weak and short-lived, as the
atmosphere will be pretty moisture-starved under the pattern
guidance is depicting through the period. NBM probabilistic guidance
only shows at most a 20% chance PoPs for the WA Cascades Sunday
onward, during primarily the afternoon hours, and even less chances
of below 10% for the eastern mountains when SW flow is overhead.
Thus, sensible weather threats should be limited for the time being.
This synoptic pattern will continue to promote breezy conditions
through the Cascade Gaps, especially as the flow pattern becomes
more zonal by next week. Afternoon gusts over 20 mph are expected
(40-50% confidence) for the usual Gaps areas of the Kittitas Valley
and Columbia River Gorge, especially for Sunday onward. Temperatures
will continue to trend towards more seasonable averages through the
period, with widespread 80s for daytime highs expected across our
population centers (70-80% confidence). Evans/74
&&
AVIATION...00z TAFs...VFR conditions expected through the period.
Expect mostly clear skies and light, terrain-driven winds less than
10 kts, outside of some breezy conditions for DLS. Some few-sct high
clouds may build heading into the evening hours. Evans/74
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 53 78 50 78 / 0 0 0 0
ALW 56 80 55 81 / 0 0 0 0
PSC 56 82 56 81 / 0 0 0 0
YKM 52 81 50 79 / 0 0 0 0
HRI 55 82 54 82 / 0 0 0 0
ELN 52 76 49 79 / 0 0 0 0
RDM 44 77 44 78 / 0 0 0 0
LGD 52 79 51 80 / 0 10 0 0
GCD 51 83 49 83 / 0 0 0 0
DLS 56 80 55 81 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&
$$
SHORT TERM...78
LONG TERM....74
AVIATION...74
Area Forecast Discussion
National Weather Service Seattle WA
824 PM PDT Tue Sep 5 2023
.SYNOPSIS...On Wednesday, a weakening cold front will sweep
across the state. The chance of showers remain low, but the best
chance for them are for areas west of Interstate 5. Patchy fog
will be possible across the entire coverage area Wednesday
morning. The pattern Thursday through Saturday transitions to high
pressure, with skies gradually clearing out during the day
Thursday and Friday. Saturday is expected to be the sunniest and
warmest day in the forecast, with highs approaching 80 degrees.
The next chance of showers returns Sunday from a cold front moving
through the state.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY/...KLGX showing a few light
echoes over the outer Coastal Waters this evening as our next
front moves in. Light showers expected on the coast early
Wednesday morning. Not much moisture makes its way farther inland
per latest HRRR runs, thus keeping the interior mainly dry. 33
Previous discussion...Upper level pattern for Tuesday shows a
trough over the Dakotas, with a zonal flow across most of
Washington today ahead of a broad shortwave trough approaching
from BC Canada. Surface high pressure has helped break up some of
the clouds this afternoon. By Wednesday, the next weak shortwave
arrives, returning overcast skies for the the morning across the
CWA. The mid levels on the deterministic models show a weak amount
of vorticity advection wrapped in the trough. Moisture remains
relatively dry for the front except closer down to the surface.
The amount of showers as a result is expected to be minimal, with
the activity being concentrated west of Interstate 5 during the
day Wednesday. QPF amounts remain around a trace to a few
hundredths of an inch of precip. With calm winds and at least some
available moisture near the surface, cannot rule out the
potential of patchy fog in the morning in spots across the CWA.
Behind the front Wednesday, the precipitation chances go away with
an upper level ridge beginning to build Thursday and Friday over
the Pacific Northwest. Surface high pressure will build into the
region as a result. Thursday will still see some clouds and patchy
fog in the morning with partial clearing expected in the
afternoon. By Friday, the skies clear out even more with only a
few clouds hanging around by the afternoon. High temperatures in
the short term remain in the 60s and 70s across the region, with
lows hovering around 50. Winds remain light out of the west around
5 mph with a shift to the north expected by Friday.
HPR
.LONG TERM /SATURDAY THROUGH TUESDAY/...The upper level ridge and
surface high pressure combo continues for Saturday, with high
temperatures topping out in the low 80s in the lowlands. The
ensembles have good confidence in the intensity and placement of
the ridge. While temperatures will be above average this weekend,
heat impacts are minor/yellow. The approaching trough over the
Pacific will swing around a shortwave Sunday. The chance of
showers will return across the entire CWA with a surface cold
front. At this time, QPF approaches a tenth of an inch towards the
coast with only trace amounts to a couple hundredths further
inland. A couple more showers in the western half of the CWA are
possible Monday into Tuesday. Temperatures cool off Monday and
Tuesday as well, with 60s and 70s across the board.
HPR
&&
.AVIATION...Westerly flow will persist aloft today as an upper
level low passes to the north over the region. Meanwhile, light
onshore flow will persist in the low levels. Conditions at all
area terminals are VFR this evening. A weak front will then move
into the region tonight into Wednesday. Expect another round of
low clouds and patchy fog to develop by Wednesday morning ahead of
the front, primarily for areas west and south of the Sound. This
could briefly drop conditions down to MVFR at times, mainly for
terminals such as KHQM, KOLM, KPWT. While some cloud cover does
look to move into the interior Wednesday morning, latest guidance
suggests ceilings will remain VFR for interior terminals. Expect
low clouds to scatter by 18Z, followed by some mid level clouds
moving in from the west as the weak system approaches. A few light
showers will be possible for areas along the coast (mainly
impacting KHQM).
KSEA...Conditions VFR this afternoon. Will likely see a BKN layer
redevelop over the terminal by Wednesday morning, but expect
ceilings to generally remain VFR. Winds will remain light at
generally 6 kt or less, gradually shifting to the N/NE tonight.
Winds will then gradually shift back to the south by early
Wednesday, persisting at 4 to 8 kt.
14/Mazurkiewicz
&&
.MARINE...Light onshore flow will continue through midweek. A weak
front will move into the region tonight and move through the area
waters on Wednesday, which will bring additional pushes of westerly
winds down the Strait of Juan de Fuca. While wind gusts may reach
small craft criteria along the central and eastern Strait at times,
current guidance continues to suggest that overall speeds will
generally remain below thresholds. Thus, have held off on any
small craft issuance for now. High pressure will then build across
the coastal waters in the wake of the front for lighter winds
headed into weekend.
Combined seas will continue to hover between 3 to 5 ft today,
though look to build slightly to 4 to 6 ft on Wednesday. Seas
will then subside back to 3 to 5 ft by Thursday and look to hover
between this range heading into the weekend. 14
&&
.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
Area Forecast Discussion
National Weather Service Salt Lake City UT
345 PM MDT Tue Sep 5 2023
.SYNOPSIS...After today, mostly dry and benign weather is expected
with temperatures returning to near normal levels. By Sunday into
the following week, some lower end precipitation chances return.
&&
.SHORT TERM (Through 12Z/6AM Thursday)...A compact mid level
shortwave, evident via GOES-W water vapor imagery, will continue to
eject to the east northeast from northern Nevada into northern Utah
and southern Idaho. Given sufficient moisture (PWATs 0.6-0.8 inches)
and continued destabilization (Sfc CAPE ~250-750 J/kg) across
portions of northwest and north central Utah, will see this
feature yield some isolated to scattered afternoon/evening
convection accordingly. CAM guidance continues to focus this
activity primarily north of I-80 and through the vicinity of the
Raft River Mountains, though the 4km NAM Nest and some recent HRRR
runs do suggest some lighter showers may persist further eastward
into the northern Wasatch Front late in the evening. For the
initial convection across northwest Utah, marginally dry subcloud
layers will bring at least a low end threat of some gusty outflow
winds from any more robust cells. Any lingering activity will wane
by late evening, with dry conditions returning overnight.
Elsewhere across the forecast region, benign weather with clear to
mostly clear skies and below normal temperatures is expected.
On Wednesday, a weaker secondary shortwave will lift through,
following largely the same trajectory as the previous one. Overall
this appears to be a bit weaker though, and with guidance supporting
a gradual drying trend and lower PWATs, anticipate more minimal
afternoon/evening convective coverage across far northwest Utah.
Otherwise, given a strengthening ridge across the southern CONUS and
associated warming 700 mb temperatures, will see afternoon highs
nudge upward several degrees in most locations. Even with the
warmup, afternoon highs are expected to be fairly near to
climatological normal levels for early September.
.LONG TERM (After 12Z/6AM Thursday)...The extended forecast
period continues to look to be pleasant under a high pressure ridge
building into the region. This will bring a drying and warming trend
to end the work week and into the weekend. Some uncertainty sits
within the beginning of the following work week but some isolated
precip could be headed back to the Great Basin.
A warming trend over the end of the work week will bring back more
seasonal like temperatures with highs reaching the mid and upper 80s
across most low lying valleys while far SW Utah reaches the 90s.
Uncertainty grows by the end of the weekend as model guidance has
shown the possibility of trough building off the PNW coast and
moving eastward. Uncertainty sits within how far it will build
southward and if it brings any impacts at all to Utah and SW
Wyoming. The NBM for now wants to create some PoPs (<40%) for the
CWA to begin the week as any dynamical support from the trough
could drive orographic processes and some isolated showers. But
nothing substantial at this point. For now, the favored solution
keeps the trough to our north and the ridge overhead of the CWA,
keeping mild and calm weather as we move into fall!
&&
.AVIATION...KSLC...Very light winds are expected to persist
throughout the forecast period with a switch in direction of out the
southeast this evening. Look for winds to becoming northwesterly
early tomorrow afternoon. VFR conditions are forecast.
.REST OF UTAH AND SOUTHWEST WYOMING...Scattered thunderstorms are
forecast to track through portions of northern Utah that may bring
gusty outflow winds to terminals through this evening. Rain or
thunderstorms can`t be altogether ruled out either. VFR conditions
are forecast through tomorrow.
&&
.FIRE WEATHER...A weak low pressure system will yield some isolated to scattered
convection in northwest to north central Utah through the
evening, with activity waning overnight. A similar setup is noted
for Wednesday, though precipitation coverage is expected to be
lower. Otherwise, strengthening high pressure will bring a drying
and warming trend through the week. This in turn will bring
afternoon minimum relative humidity values down into the teens for
much of low elevation areas, and closer to the 20 to 30 percent
range for higher elevations. By Sunday into early next week, there
is some indication that moisture will begin to increase, and with
it bring back low end precipitation chances for portions of the
state.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&
$$
SHORT TERM...Warthen
LONG TERM...Selbig
AVIATION...NDeSmet
FIRE WEATHER...Warthen
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity
Area Forecast Discussion
National Weather Service Great Falls MT
900 PM MDT Tue Sep 5 2023
.SYNOPSIS...
Areas of smoke will continue to affect North Central MT through
Wednesday morning, while scattered showers or an isolated
thunderstorm is possible. The best chance for any storms will be
over the mountains. Later this week, the chance for storms will
become a bit more widespread over North Central MT. Overall,
afternoon temperatures will be seasonable, with afternoon highs
mostly in the 70s and lower 80s.
&&
.UPDATE...
6:30PM Quick Update: Scattered rain showers across Central Montana
continue this evening moving eastward producing brief periods of
moderate to heavy rainfall that can reduce visibility for a brief
period of time as the showers move through. Increased and added
PoPs to the current forecast where showers have developed and will
move eastward in the next few hours. Webb
9PM Evening Update: For this evening`s update, only minor
adjustment to the rest of tonights PoPs to reflect current surface
observations and radar. Added in patchy fog to the grids for the
potential of fog development for this morning across valley
locations in Central Montana that saw precipitation this evening
and can see clearing overnight. Minor adjustment to haze grids as
well to add in haze for locations currently observing haze in
surface observations. Latest HRRR and RAP near surface smoke
forecasts suggest smoke and haze to linger this evening in eastern
portions of our CWA such as Hill, Blaine, and Fergus counties.
Smoke and haze is forecasted to move eastward tomorrow morning and
afternoon from the region. Webb
&&
.AVIATION...
520 PM MDT Tue Sep 5 2023 (06/00Z TAF Period)
We start the TAF period with a variety of conditions at all
airfields. For KHVR and KLWT, smoke and haze continues to impact
visibility this evening to between 2 and 6 miles. Visibility should
improve to VFR conditions through the TAF period as the upper level
flow moves the smoke northeastward. Scattered rain showers across
Central and Southwest Montana continue to move northeastward across
our region this evening bringing periods of mountain obstruction for
Central Montana. Scattered rain showers are forecasted to have
little impact to airfields this evening (less than 15% probability
for reductions in visibility of less than 6 miles). A quiet night is
then in store for all airfields through tomorrow afternoon. Webb
Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.
&&
.PREV DISCUSSION...
/ISSUED 630 PM MDT Tue Sep 5 2023/
Tonight through Friday...The main concern tonight over North
Central MT will continue to be the areas of smoke/haze. With
visibility generally above 2 miles, no dense smoke advisory will
be issued at this time. Otherwise, there is a small chance for an
isolated thunderstorm over Central MT, with the best chances over
the mountains. Generally dry conditions are expected during the
day Wednesday, but another round of showers/thunderstorms are
possible Wednesday night through Friday. Overall this will be a
hit/miss thunderstorm activity, with most storms producing less
than 0.20 inches of rainfall. Afternoon temperatures will be
seasonable during this period. Brusda
Looking ahead, CPC`s Outlook suggests temperatures to persist 40
to 60% above seasonal averages through mid-September, while
precipitation retains a near normal outlook. 3 to 7 Day Cluster
Analysis favor a new upper-level ridge to build centralized over
Montana by Day 4 (Saturday) and lasting through early next week,
further indicating the likeliness of warmer and drier conditions
through mid- September. - Pierce
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 50 80 53 78 / 10 0 30 10
CTB 46 76 46 74 / 10 10 10 0
HLN 52 81 53 81 / 30 10 20 20
BZN 46 79 48 79 / 0 10 20 20
WYS 36 67 38 70 / 0 0 20 20
DLN 43 74 45 75 / 10 0 10 10
HVR 51 83 52 80 / 0 0 30 0
LWT 48 79 49 76 / 10 10 20 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls