Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/16/24
Area Forecast Discussion
National Weather Service La Crosse WI
1052 PM CDT Thu Aug 15 2024
.KEY MESSAGES...
- Showers and storms persist into the evening hours today with
gusty winds being possible in any stronger storms that
develop. Additional showers and storms are likely (50-80%
chance) for Friday.
- Fog potential tonight into tomorrow morning east of the
Mississippi River.
- Slightly below normal temperatures through next week with
sporadic shower and storm chances.
&&
.DISCUSSION...
Issued at 309 PM CDT Thu Aug 15 2024
Rest of Today - Tonight: Showers and Storms This Evening, Fog
Potential Overnight East of the Mississippi River
The general synoptic setup this afternoon can be seen on GOES-16
water vapor imagery and 15.16z RAP 500mb heights with a surface low
and corresponding upper-low situated on the ND/MN state line. As
this low slowly works its way southeast, pieces of shortwave energy
can be noted in the cyclonic flow, aiding convective initiation
across the Great Plains and Midwest. Attention this afternoon turns
to how much instability we have managed to build in order to aid
convection as we approach peak heating. As of 1830z, noting some
developing cumulus across portions of southeast MN leading to shower
activity. Still some questions with how these showers will deepen
over the coming hours though. While the 15.17z RAP continues to
increase MLCAPE values to around 1000-2000 J/kg locally into the
evening, currently satellite trends have kept a fairly persistent
low-level cloud deck over much of the local area into the
afternoon. As a result, ongoing convection could struggle to
deepen with limited instability where cloud cover persisted. If
storms are able to tap into more instability where clearing is
present, DCAPE values of 600-900 J/kg in the 15.17z RAP would
support an isolated threat for some stronger wind gusts as
storms move east.
With the aforementioned cloud cover lingering over portions of the
area through peak heating this afternoon, particularly along and
east of the Mississippi River, diurnal mixing processes likely will
be minimized in these locations allowing low-level moisture to
remain in place going into the overnight. Consequently, noting
deterministic soundings developing a near surface inversion with
this low-level moisture, particularly across southwestern
Wisconsin. The main question will be if any cloud cover lingers
into the overnight hours which could hinder any fog development.
A key point of interest in the 15.12z HREF visibility
probabilities overnight is there is minimal deviation between
the 4 mile probabilities (40-70%) and the 1/4 mile probabilities
(20-50%) in southwestern Wisconsin. As a result, areas that
manage to develop fog would favor low visibilities that could
lead to fog becoming locally dense before fog dissipates Friday
morning.
Friday: Seasonable With Additional Showers/Storms Likely
Looking towards Friday, the previously stated low pressure system
pushes southeast into north-central Wisconsin on Friday afternoon.
Consequently, this will further instigate shower and storm
development throughout much of the day on Friday. The overall
setup generally shows a piece of vorticity associated with a
subtle shortwave that progresses through the area during the
late morning and early afternoon. As instability increases by
afternoon, convection will develop along an associated surface
boundary that will progressively push eastbound. With minimal
0-6km bulk shear in the 15.15z RAP to maintain any organized
convection, storm mode will be very pulse-like in nature. The
one caveat to the afternoon showers and storms tomorrow will be
the possibility for any non-supercell funnels that can develop.
With the vertically stacked low and a surface boundary pushing
through the area, the non-supercell tornado parameter in the
15.15z RAP is highlighting portions of central and north-central
Wisconsin with values greater than 1 during the afternoon.
After this round of convection moves through during the early
afternoon hours, limited instability in the 15.15z RAP would
suggest limited able for deep convection to occur. However,
given some of the CAMs holding onto showers later into the
evening with marginal instability and weak pieces of energy
pivoting around the low, held onto some precipitation chances
through the evening (20-40% chance).
Saturday - Wednesday: Continued Seasonable Temperatures With Spotty
Shower and Storm Potential
As we head into the weekend and next week, the aforementioned
vertically stacked low will slowly continue to migrate eastward. As
the associated trough axis becomes more neutrally tilted, a
deepening ridge to our west will help posture our region in
northwesterly flow pattern. Consequently, this will aid in
keeping our temperatures near to slightly below average into
next week. This is reflected in the 15.12z grand ensemble
(GEFS/EC ensemble/Canadian ensemble) with median high
temperatures trending in the middle 70s to lower 80s with inter-
quartile spread of generally around 5 degrees through the first
half of next week. Shower and storm chances will be possible
with any shortwaves embedded in the flow but guidance currently
having low confidence in how these may resolve at this time.
&&
.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1053 PM CDT Thu Aug 15 2024
Partly to mostly cloudy skies for the overnight period. Some
areas of patchy fog will be possible, especially for areas
along and east of the Mississippi. If enough clearing does take
place, IFR and LIFR fog could develop, especially in the river
valleys. There is currently between a 20 and 30% chance of these
lower flight categories occurring overnight. Scattered showers
and storms will be possible across the area from Friday late
morning through the rest of the day. MVFR conditions are likely
to occur during the afternoon with lower flight categories
expected for Friday night due to low stratus clouds. Southwest
winds will transition to northwest winds Friday afternoon with
some gusts between 15 and 25kts, especially in southeast
Minnesota and northeast Iowa.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Naylor
AVIATION...Cecava
Area Forecast Discussion
National Weather Service Bismarck ND
946 PM CDT Thu Aug 15 2024
.KEY MESSAGES...
- Isolated thunderstorms possible, with mainly rain showers
east of Highway 3, through this evening. The threat for severe
weather is low.
- Areas of wildfire smoke to return across the west today, then
across the west and central tonight through Friday.
- Warmer weather, with limited chances (20 to 40%) for
precipitation, is anticipated Friday into early next week.
&&
.UPDATE...
Issued at 945 PM CDT Thu Aug 15 2024
Showers over the eastern portions of the forecast area are now
generally found over the southern James River Valley, and have
begun to scatter out while continuing its southeastward
trajectory. The earlier isolated showers and storms across
central North Dakota have also generally dissipated, with no
lightning detected across the area over the past few hours.
The visibility reductions due to surface wildfire smoke
previously found across much of western North Dakota are now
found mainly in the southwest. Another push of smoke is
beginning to move out of the southern Canadian Prairies, with
visibility reductions as far south as Yorkton and smoke evident
on satellite imagery, and is expected to begin to move into the
northwest over the next few hours before lingering overnight.
Winds remain northerly and have generally begun to diminish,
except in the far southeast where showers linger and sustained
speeds from 15 to 25 knots, and gusts up to 30 knots can be
found. The forecast remains on track at this time.
UPDATE Issued at 650 PM CDT Thu Aug 15 2024
A broad area showers that are wrapped around a low pressure
center to the east of the forecast area linger over the southern
James River Valley at the time of this early evening update.
Rainfall rates remain fairly low, less than one-tenth of an inch
a hour. A few short-lived thunderstorms continue to form off of
the pseudo dryline moving in from the northeast, mainly over
north central North Dakota. The previously mentioned elevated
Non-Supercell Tornado parameter continues to diminish this
evening which, along with the very short-lived nature of these
thunderstorms, continues to limit the chances to funnel or
landspout development over our area. Some visibility reductions
due to surface smoke continue over the west, though the bulk of
the smoke has already progressed much further south than
suggested by either the HRRR or RAP smoke models for this time.
Will continue to monitor the trends of these visibility
reductions.
At this time of this update, we have cancelled the Flood
Advisory present over portions of Dickey and LaMoure counties as
floodwater continue to recede. Otherwise, have made a few
tweaks to the sky grids to account for the latest satellite
trend. The forecast remains on track.
&&
.DISCUSSION...
Issued at 302 PM CDT Thu Aug 15 2024
Wrapped up upper level low will continue to bring showers and
perhaps an isolated thunderstorm across eastern portions through
this evening. This will mainly be for areas along and east of
Highway 3. Meanwhile, abundant instability across central and
northern portions could lead to some pulse like thunderstorms
through this evening. WPC has analyzed a cold front in
northwestern ND currently, although this appears to be more of a
pseudo dry line moving through. This front could be the focus
for a few stronger storms through this evening. Shear is
lacking, with up to 20 knots currently found in the CWA. Lapse
rates are also lacking. Thus severe hail is not anticipated at
this time, although small hail is possible. The wind threat is
also minimal, although inverted v soundings could indicate some
elevated wind gusts are possible as the pulse thunderstorms
collapse. Of concern with the upper low, steep low level lapse
rates, some low level shear, and some low level CAPE there could
perhaps be some brief funnel clouds near any more robust
updrafts from todays convection. Non Super Cell Tornado
parameter is also elevated currently on SPC`s meso analysis
page. The pulse nature of these storms may not give enough
residence time for a funnel cloud or brief landspout to setup,
although it is possible. Behind this mentioned boundary is
starting to see some wildfire smoke filter into the state. This
could impact the northwest through the evening. Tonight,
thunderstorms should diminish shortly after sunset, while
showers may linger in the southeast. Smoke will continue to
filter into the west and north, perhaps reducing visibility
through the night. RH values will approach 100 percent, although
winds may be elevated enough to hinder fog development tonight.
Thus have left fog out for now. Lows tonight will be in the mid
50s to mid 60s. Upper low will continue to push eastward
Friday. This could perhaps bring some showers to the southeast,
with slight PoPs now in the forecast. Smoke will also continue
to filter into the state a high pressure builds into the area
through the day. Smoke may linger into Friday night as well.
Highs will be still remain slightly be low normal and generally
in the mid 70s to lower 80s.
A weak warm front may then lift across the state on Saturday
which could bring some showers and thunderstorms, mainly across
the west. Shear is elevated, although instability is limited.
There could be an isolated stronger storm as a result, and will
have to monitor for anything stronger. Temperatures should warm
with this front, into the 80s west and upper 70s east. Upper
level ridge builds more overhead on Sunday bringing mainly clear
skies and more warming temperatures. Perhaps some mid to upper
80s will be found as a result in the central and west, with
lower 80s east. Clusters then have this ridge set up in the
central US and flatten at some point. How far north this
flattens will determine thunderstorm chances. If this flattens
more over ND, then daily thunderstorm chances are possible, and
could possibly be strong. This ridge also bring higher
confidence in warmer temperatures in the 80s to perhaps lower
90s at least through mid week. This could also keep overnight
lows near normal.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 650 PM CDT Thu Aug 15 2024
For the 00Z TAF period, mainly VFR conditions are anticipated
at KXWA and KBIS. At the terminals of KMOT and KJMS, MVFR to VFR
ceilings are expected through Friday morning as a broad area of
precipitation continues to where a broad area of precipitation
wraps around a lower pressure to the east of the forecast area.
A few showers and thunderstorms are also developing across
central North Dakota along a pseudo dryline pushing in from the
northwest, and may occasionally impact the terminals of KBIS and
KMOT through this evening. At KDIK, wildfire smoke is
occasionally promoting MVFR visibilities at the time of this
update. Near surface smoke models have not been capturing these
visibility reductions particularly well, so while near surface
wildfire smoke is expected to filter across the west and central
overnight, confidence is too low to add visibility reductions
due to the smoke any other site at this time. Moderate winds
out of the north-northwest will generally diminish through this
evening and overnight, except in the southwest, including at
the terminal of KJMS, where moderate winds from 15 to 20 knots,
and gusts up to 25 knots are anticipated to continue through
the early Friday afternoon.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Adam
DISCUSSION...Anglin
AVIATION...Adam
Area Forecast Discussion
National Weather Service Boise ID
856 PM MDT Thu Aug 15 2024
.DISCUSSION...Showers and thunderstorms ended rapidly this
evening as a short wave trough in Oregon moved into eastern
WA. Warmer weather will occur the next two days as upper flow
changes from west to southwest Friday, and to nearly southerly
Saturday. High temps Saturday will be 95-100 degrees in the
lower southern valleys. Monsoon moisture will be kept east of
our CWA so skies will be mostly clear. Today`s rain cleared some
of the smoke, but HRRR model shows it clearing even more during
the next two days, especially in southern areas Saturday. Smoke
will continue, however, near the fires to the north and northeast
of Boise. Current forecast is in good shape. No updates.
&&
.AVIATION...VFR, except localized MVFR/IFR and mountain
obscuration near wildfires. Surface winds: variable 10 kt or
less overnight, then SW to NW 5-10 kt Friday afternoon. Winds
aloft at 10kft MSL: SW 10-20 kt.
KBOI...VFR. Haze from distant wildfires. Surface winds: light
and variable overnight, then NW 5-10 kt Friday afternoon.
Weekend Outlook...VFR, except localized MVFR/IFR and mountain
obscuration near wildfires. High density altitude due to hot
temperatures, mainly Saturday. South-southwest winds aloft of
20-40 kt will produce gusty afternoon winds Sat/Sun across SE
Oregon and mountains of SW Idaho.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Saturday night...A shortwave is
moving across eastern Oregon this afternoon, and is the focus of
showers and thunderstorms. The showers and thunderstorms will
slowly move NE tonight as the shortwave exits the area. Main
threats of storms will be gusty outflow winds to 50 mph, areas
of blowing dust, and new fire starts. Some of the high
resolution guidance still shows remnant thunderstorm outflows
moving across the Treasure Valley late this afternoon and
evening as the showers and storms weaken. Conditions dry out
tonight after sunset. Another weak disturbance brings a slight
chance of thunderstorms on Friday afternoon mainly north of a
line from southern Baker County OR to Banner Summit. Higher
terrain of SE Oregon could see cumulus buildups but otherwise
the area remains dry with high temperatures holding a few
degrees below normal. Strong southwest flow develops on
Saturday as a trough digs south along the Pacific Northwest
coast. Temperatures warm to around 5-10 degrees above normal
with 95-100 in the Snake Basin on Saturday. Southwest flow will
bring breezy and unstable conditions especially during the
afternoons, where a fire weather watch has been issued.
LONG TERM...Sunday through Thursday...A trough will remain off
the Pacific Northwest coast and a strong ridge over CO/NM will
keep strong southwest flow going over the region through the
long term. Southwest Idaho and southeast Oregon will remain in
a dry slot, with hot, very dry, and windy conditions expected
through the long term. Temperatures will be around normal to 5
degrees above normal through the period. Monsoon moisture should
stay east of Twin Falls through the period.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning until 10 PM MDT this evening IDZ402-403.
Fire Weather Watch from Saturday afternoon through Saturday
evening IDZ401>403-421.
Fire Weather Watch from Saturday afternoon through Saturday
evening IDZ423-426.
OR...Red Flag Warning until 10 PM MDT /9 PM PDT/ this evening
ORZ636-637-646.
Fire Weather Watch from Saturday afternoon through Saturday
evening ORZ636-637.
&&
$$
www.weather.gov/Boise
Interact with us via social media:
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DISCUSSION...LC
AVIATION.....SH
SHORT TERM...KA
LONG TERM....KA
Area Forecast Discussion
National Weather Service Boston/Norton MA
1039 PM EDT Thu Aug 15 2024
.SYNOPSIS...
Scattered showers thunderstorms will end this evening. Dry
weather returns Friday and will continue Saturday for all but
far western portions of southern New England. A slow moving
front will lead to unsettled weather Sunday through Tuesday. A
drying trend with seasonable temperatures are expected for the
middle of next week. Meanwhile, Hurricane Ernesto will track
well southeast of New England, but it will bring rough surf and
strong rip currents to south facing ocean beaches this weekend.
&&
.NEAR TERM /THROUGH FRIDAY/...
Latest SPC mesoanalysis showed the convective environment
weakening rapidly late this evening. The last few runs of the
RAP were handling the lingering convection the best, but did
make some tweaks from there to account for observed trends.
Expecting rainfall to end between 11 PM and 2 AM. Minor tweaks
to temperatures as well.
8 PM Update...
Widespread convection across eastern southern New England has
mostly diminished, with some isolated convective cells moving
into western MA from the CT River Valley in VT/NH. These storms
have already begun to weaken with sunset around 745pm, and
should continue to do so as instability wanes.
With a lot of residual moisture, with radar QPF estimates
topping 5" in parts of SE MA and the Cape!, and light ENE to
calm winds, do expect fog to form, especially east of Worcester.
In fact, we have already seen a bit of fog develop around the
office. The remains uncertainty in how low vsbys will go
overnight, with some guidance, like the GLAMP, hinting at
widespread 1/4sm fog, and other guidance taking a much more
moderate approach of vsby reductions to 2-3SM.
245 pm update...
Convection developing, so far along the sea breeze boundary
along the south coast and higher terrain in western MA and CT.
Also watching the cluster of t-storms just to the north that is
in association with the shortwave dropping south. Temperatures
aloft are fairly chilly (-14 to -16C at 500mb), so some small
hail is to be expected with the storms. Sub cloud layer is also
rather dry, so that will enhance the potential of seeing
localized downbursts/gusty winds with the strongest storms.
DCAPE values are running 800-1000 J/kg, which is fairly notable.
Otherwise, winds in the atmosphere aren`t all that strong, so
shear is minimal, meaning we shouldn`t see organization with the
thunderstorms. They`ll tend to be more pulse variety.
Hi-res CAMs still not doing all that great with the convective
forecasts, so took a more broadbrush approach with the PoP
forecast through the evening. Expect the activity to quickly
weaken as we get closer to sunset, so the strongest activity
should be between now (as I type this, not necessarily as you
read it) and 6pm.
For the rest of the night, it should be quiet. We will likely
have some patchy fog develop given the light winds, especially
in any areas that receive rain through this evening.
&&
.SHORT TERM /FRIDAY NIGHT/...
245 pm update...
Looks like a quiet day. Ridging will be building in aloft. Some
of the hi-res models suggest a shower or two could develop
across the higher terrain of the Berkshires. At this point, kept
the chances less than 10%. Surface winds will be light, so sea
breezes will develop by late morning along the coast. Thus
immediate coastal locations will remain cooler than inland.
850mb temperatures will be running around 15C, which would
support high temperatures in the mid 80s in most areas (except
cooler along the coast). Quiet weather into Friday night as
well. Could be some patchy fog in a few spots.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
300 pm update...
Key Points
* Generally dry first half of the weekend with a chance for some pop
up showers across interior SNE
* Unsettled late Sunday into early next workweek with slow moving
front swinging through the northeast
* Drying trend appears to develop mid next week with seasonable
temperatures
Saturday and Sunday...
Guidance continues to trend drier for Saturday with mid level
ridging parked over southern New England through late Saturday
evening; before the ridge moves seaward overnight and into Sunday.
Southerly flow will yield increasing moisture with PWATs climbing
back towards 1.5". Can`t rule out a few diurnal showers across the
terrain of interior southern New England but it should be a dry day
for most. Temperatures will be seasonable, in the upper 70s to mid
80s, but climbing dewpoints, into the mid/upper 60s, will result in
some mugginess.
Ridge slowly moves east of the region on Sunday, though likely
influences a mainly dry day, ahead of approaching cold front/trough
moving east from the Great Lakes region. With the slowing departure
of the ridge and delayed arrival of the front, thinking the best
forcing arrives over SNE overnight, after instability wanes. Thus,
the Sunday afternoon thunderstorm threat looks to be best to our
southwest of our region. This is corroborated by the CSU Severe
Probabilities which also keeps the wind threat to our southwest.
This aforementioned trough comes in time to help steer Hurricane
Ernesto away from our region, though we expect coastal impacts, such
as high rip risks and high surf, to begin to impact the region the
second half of the weekend.
Monday into Tuesday...
With a later shift in guidance, the best chance for widespread rain
and thunderstorms will come on Monday. Prefrontal PWATs will climb
to as high as 1.8-2", which will result in numerous showers and
embedded downpours through the day; though, again the threat for
the most precipitation looks to be west of Worcester. Ensemble
probabilities don`t hint at a tremendous amount of precipitation to
be associated with the front, with both the GEFS and ECMWF probs of
1" of QPF maxing out around 30% across the high terrain. CAPE looks
to rise to between 1500-2000J/kg on Monday which should provide
enough "juice" to initiated scattered thunderstorms. We will need to
keep an eye on the severe threat, with the CSU day 5 probs
highlighting a low wind threat for the region on Monday.
Front should pass by early Tuesday which will yield generally
improving conditions. Much drier air is expected to filter in behind
the front, falling to as low as 0.5" by late Tuesday evening.
Mid week and beyond...
Substantial ridging develops over the central CONUS mid week, though
we generally remain on the lee side of the ridge, which should help
us avoid the worst of the potential heat. It will also yield a
mainly dry mid week and beyond.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Moderate confidence through tonight. High confidence Friday.
Isolated showers will persist through ~04-06Z. Forecast guidance
is indicating fog developing in areas later tonight, and suspect
the areas that see fog is where it rained earlier today. Some of
that fog could result in IFR visibility and ceilings if it gets
thick enough. Winds will be light overnight.
For Friday, VFR. More light surface winds, so sea breezes will
develop by late morning. VFR continues Friday night, with
potential for local MVFR/IFR in any patchy fog.
KBOS TAF...Moderate Confidence. There is potential for MVFR or
IFR conditions to develop after 06z with fog and stratus. If it
does develop, it will be out by 12z. Seabreeze should develop
about 14z Friday.
KBDL TAF...Moderate Confidence. VFR conditions prevail. Could
be some MVFR in fog very late tonight.
Outlook /Saturday through Tuesday/...
Saturday: VFR.
Saturday Night: VFR. Slight chance SHRA.
Sunday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.
Sunday Night: Mainly VFR, with local IFR possible. Chance SHRA,
isolated TSRA.
Monday: Mainly MVFR, with local IFR possible. Chance SHRA,
slight chance TSRA.
Monday Night: Mainly VFR, with local IFR possible. Chance SHRA,
slight chance TSRA.
Tuesday: Mainly VFR, with local IFR possible. Slight chance
SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
300 pm update...
Through Friday Night...High Confidence.
Light winds through Friday night. Only aspect of the forecast
that mariners need to be aware of is the expected increase in
swells starting Friday night and lasting into Monday. These
swells and associated increased wave heights will be from
Hurricane Ernesto. The swells will also be of very long period
(13 to 16 seconds), so this will also result in strong rip
currents and high surf developing along south facing coast
lines. This may also result in rough conditions at the entrances
to inlets and harbors.
Outlook /Saturday through Tuesday/...
Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft.
Sunday: Winds less than 25 kt. Areas of rough seas.
Sunday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.
Monday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers, isolated thunderstorms.
Monday Night through Tuesday: Winds less than 25 kt. Seas up to
5 ft. Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Air Quality Alert until midnight EDT Friday night for
MAZ002>004-008>012.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...KS/Nash
NEAR TERM...Belk/KS/Nash
SHORT TERM...Nash
LONG TERM...KS
AVIATION...Belk/KS/Nash
MARINE...KS/Nash
Area Forecast Discussion
National Weather Service Billings MT
244 PM MDT Thu Aug 15 2024
.DISCUSSION...
This afternoon through Friday night...
A ridge at 500 mb will slide eastward tonight, with the ridge axis
reaching the MT/Dakota border by 6 AM MDT Friday. To the west of
the ridge axis, southwesterly cyclonic flow will move over our
area and facilitate the development of isolated-scattered showers
and thunderstorms, first over the mountains this afternoon, then
across most of south central MT tonight (20-70% chance, greatest
in the mountains). Instability and wind shear are low, so not
expecting severe weather at this time.
On Friday, our area will continue to be under southwesterly,
cyclonic flow aloft with additional disturbances moving through
the flow. This pattern will facilitate additional isolated to
scattered shower and thunderstorm activity over much of the area
(20-50% chance, greatest north of Billings).
A ridge should return at 500 mb Friday night, causing shower and
thunderstorm activity to diminish from west to east.
Low temperatures will generally be in the 50s to lower 60s tonight
and Friday night. High temperatures will mainly be in the 80s to
lower 90s Friday.
Smoke: there will be smoke in the atmosphere into Friday. HRRR
shows greater smoke concentrations near the surface probably over
eastern MT. Smoke could decrease over the Beartooth/Absaroka
Mountains tonight-Friday as southwesterly winds aloft push the
smoke out of that area. RMS
Saturday through Thursday...
The extended forecast features above normal temperatures with
continued chances of precipitation as monsoonal moisture returns
to the region under a developing ridge aloft.
On Saturday, the upper ridge will begin to build back in over the
region as a low pressure system digs south off the west coast of
the United States. The return flow of monsoonal moisture will
remain south of our area Saturday, so warm and dry conditions are
in the forecast. On Sunday, the monsoonal moisture looks to return
along with the chance of precipitation in the afternoon and
evening across portions of the area (15-50% chance mainly west of
Billings, highest in the mountains). Sunday also looks to be the
warmest day of the weekend with high temperatures reaching into
the low to mid 90s.
The hot conditions with periodic chances of precipitation will
then continue Monday through Thursday as the upper level weather
pattern looks to stay relatively consistent. With that said,
uncertainty does exist in how the pattern will evolve into the end
of the week. This uncertainty impacts temperatures and placement
of precipitation across the region, so this is something to watch
as we progress into next week. Arends
&&
.AVIATION...
While VFR conditions will prevail today, lofted wildfire smoke
will continue to reduce slant range visibility at times. With
this, surface impacts from the smoke remain uncertain. Weather
stations in northern Montana have seen reductions in surface
visibility from the smoke today, and some of these impacts could
move south into southeastern Montana. At this time, airports
around KMLS and KBHK have the best chance of seeing surface
visibility reductions below 10 miles. Too much uncertainty remains
at KBIL for any mention to be added into their TAF.
Outside of smoke, isolated showers and thunderstorms will move
over the mountains around KLVM this evening. This activity could
produce local MVFR with brief gusty winds at KLVM. Arends
&&
.PRELIMINARY POINT TEMP/POPS...
Fri Sat Sun Mon Tue Wed Thu
-----------------------------------------------------------
BIL 059/087 059/090 062/094 064/093 062/094 061/091 060/086
12/T 10/U 01/U 12/W 21/U 11/U 11/B
LVM 049/083 049/088 054/091 056/090 054/090 053/088 052/083
63/T 30/U 02/T 14/T 22/T 12/T 22/W
HDN 057/089 056/092 060/096 063/094 060/094 058/093 058/088
12/T 10/U 00/U 12/W 21/U 11/U 11/U
MLS 057/087 062/090 063/093 067/094 063/091 061/090 061/086
01/H 20/U 00/U 12/T 21/U 11/U 21/U
4BQ 058/088 060/092 063/095 066/093 064/093 061/093 061/089
02/T 20/U 00/U 02/T 21/U 10/U 11/B
BHK 054/084 057/089 060/090 061/089 060/089 059/089 058/085
00/H 21/U 00/U 11/B 31/U 10/U 21/U
SHR 053/088 053/092 059/094 061/091 059/092 057/093 058/088
12/T 00/U 01/U 13/T 21/U 11/U 11/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Cleveland OH
948 PM EDT Thu Aug 15 2024
.SYNOPSIS...
A warm front will lift northeast across the area on Friday as
low pressure slowly approaches from the northwest. This low
pressure will drift east through the weekend, dragging a cold
front across the area Saturday.
&&
.NEAR TERM /THROUGH FRIDAY NIGHT/...
930 PM...Radar returns continue to be apparent across portions
of North and Northwest Ohio this evening, though much of this
activity remains light with the dry low- level air mass in
place. Slightly heavier rain exists just south of the area
across central OH. Otherwise, we`ll be watching how convection
evolves across eastern IA/IL this evening and overnight ahead of
an upper-level trough evident on water vapor imagery. Still
some uncertainty on the eastward extent of this convective
activity, though there exists the potential for a few
thunderstorms Friday morning across Northwest Ohio.
Previous Discussion...
Low pressure currently over Minnesota will drift towards
northern lower Michigan by late Friday night. Ahead of this low
a warm front will lift northeast across the area on Friday. An
initial cold front (with little airmass change) will cross from
west to east Friday night with a shortwave aloft crossing
through the southern Great Lakes Friday afternoon/evening.
Moist isentropic lift ahead of the warm front is supporting
clouds and light rain showers into parts of western Ohio. While
dry low-levels are in place ahead of this light rain, at least
some of it is reaching the ground. Expect thicker clouds and
potential for a few light rain showers to slowly spread east
through tonight, though progress will likely slow for several
hours later this evening into the overnight as the rain will
struggle to push east into the departing high pressure. There
will be another (greater) push of showers as the warm front
lifts in very late tonight into Friday morning from west to
east. We should see a period of relatively drier weather spread
in from the west/southwest behind the warm front into the
afternoon on Friday. By mid to late-afternoon, any heating will
result in some destabilization which should allow showers and
thunderstorms to increase in coverage as the shortwave moves
through the region and adds some large-scale lift. Storms will
be favored across parts of Northeast OH/Northwest PA in
proximity to the warm front, with additional activity trying to
spread in from the west during the late afternoon or evening
ahead of the approaching cold front. Shower and storm chances
will continue to work east across the area Friday night as the
cold front moves through, though the overall coverage and
intensity should gradually diminish after sunset.
The environment will Friday afternoon and evening will feature
relatively skinny CAPE due to weak mid-level lapse rates with
modest wind shear. Overall, about 25 knots of deep-layer shear
and 750-1500 J/KG of MLCAPE can be expected. While a couple of
stronger storms may produce gusty to locally damaging winds
thanks to 700-1000 J/KG of DCAPE and somewhat steep low-level
lapse rates of 7-8C/km, feel like the severe threat is on the
lower end. The SPC has maintained a Day 2 "Marginal Risk" (level
1/5) for severe weather for Friday afternoon-evening. Skinny
instability profiles and precipitable water values climbing to
1.75-2.00" will support efficient rain rates with convection
Friday afternoon and evening, so if some training or back-
building occurs (as the HRRR and ARW hint at) there could be a
localized heavy rain/flooding concern too. Any localized severe
weather or flooding threats will diminish with time after
sunset Friday night.
Lows tonight will be milder than the last several, generally
ranging from the mid 60s to near 70. Highs on Friday will reach
the lower to upper 80s with increasing humidity. The coverage of
clouds and rain with the warm frontal passage will influence
those highs. With muggy dew points, lows will struggle to fall
much below the upper 60s to near 70 Friday night.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
A wet and active pattern will dominate this weekend as a surface low
meanders east across the Great Lakes region. On Saturday, an upper
level trough will continue to dig south across the region as an
occluding low approaches the central Great Lakes. A cold front
associated with this low will depart to the east early Saturday with
some showers and thunderstorms lingering across eastern portions of
the CWA. The aforementioned low will persist over the region,
resulting in winds behind the departing front remaining from the
southwest and continuing to advect moisture and warmer temperatures
into the area.An 850mb LLJ of 20-30 knots and upper level support
from a shortwave moving on the periphery of the trough will enhance
the chance for shower and thunderstorm potential through Saturday
afternoon ahead of a secondary cold front. Daytime heating should
aid in enhancing instability across the area with models generally
suggesting an average of 1500 J/kg by 18Z Saturday with 0-6km bulk
shear of 20-30 knots. These conditions should lead to an increase
risk of severe weather Saturday afternoon into the evening hours
which SPC has highlighted in a Day 3 Marginal with the primary
threat remaining strong winds. There are some potential limiting
factors however that make this forecast less confident, including
how the overnight/morning convection and lingering clouds will
impact the area by increasing stability which will likely be
enhanced if the initial cold front slows at all. The other aspect is
the exact location of the low pressure center over the region. There
remains a bit of a spread in model agreement with some placing the
low closer to Lake Erie while others place it closer to over Lake
Huron which will impact the location of the features described
above. In addition to the severe threat, PWAT values of 1.5-1.8
inches and warm cloud depths greater than 10kft will present another
chance for locally heavy rainfall and potential flooding. As a
result, WPC has placed portions of the area in a Day 3 Marginal ERO.
By Saturday night, showers and thunderstorms will linger across the
area, but the severe threat will diminish once the sun goes down.
The aforementioned low will continue to very slowly move east through
Sunday, finally reaching the New England area Sunday night. With the
placement and continued upper level support from a deepening trough,
chances of showers and isolated thunderstorms will persist through
the entire period, gradually tapering from west to east Sunday
night. Less confidence exists for any chance of severe weather or
heavy rainfall on Sunday as the generally flow become northwesterly
and colder air begins to push south. Will need to continue to
monitor the pattern given the uncertainty of the low placement.
High temperatures on Saturday will climb into the upper 70s to low
80s, possibly warming a tad more in areas where there is any cloud
breaks. Once winds shift to northwesterly for Sunday, CAA will
return highs to the mid to upper 70s. Overnight lows through the
period will be in the low 60s.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Lingering showers and storms may persist across the eastern CWA as
the aforementioned low continues to slowly drift northeast towards
Nova Scotia. By Monday evening, high pressure should become dominant
across the entire area and end the potential for precipitation from
Monday night through Thursday. With the presence of a Canadian high
pressure over the area, temperatures will remain a bit cooler Monday
through Wednesday with highs climbing into the low to mid 70s and
then will slightly warm near the end of the period into the upper
70s. Overnight lows will drop into the 50s.
&&
.AVIATION /00Z Friday THROUGH Tuesday/...
VFR across the TAF sites this evening with primarily VFR to
persist through much of the TAF period. Will be primarily dealing
with a lot of light rain showers with minimal impact expected
in the first half of the TAF period. Non- VFR appears more
likely towards the end of the TAF period Friday afternoon and
evening, though confidence remains low on thunderstorm timing
and location. Have added vcts at the central and eastern TAF
sites in this update, excluding TOL/FDY since confidence in
afternoon/evening thunderstorms is lower along the I-75
corridor. Thunderstorms could be strong at times Friday
afternoon and evening, with the primary threat being wind.
Otherwise, ceilings should remain above 3kft for the most part,
though can`t rule out brief drops between 2 to 3kft in any
heavier showers or thunderstorms.
Winds will generally favor a east to southeast direction this
evening and overnight, around 5 knots. Winds will gradually
shift more towards the southeast and eventually south by Friday
afternoon, 10 to 12 knots.
Outlook...Non-VFR possible in periods of showers and
thunderstorms Friday night through Monday, especially in the
afternoon and evening hours. Widespread non-VFR appears most
likely in low ceilings on Sunday into Monday.
&&
.MARINE...
Easterly winds of 5-10 knots this afternoon will gradually become
southeasterly at 10-15 knots by Friday morning. A warm front
associated with a low pressure system over the western Great Lakes
will move north across the lake on Friday resulting in winds
gradually becoming more southerly at 10-15 knots. The aforementioned
low pressure system will slowly drift east across the region,
becoming centered near Lake Erie on Saturday. This will increase the
gradient across Lake Erie and result in winds increasing from the
southwest to 15-20 knots. This flow will keep the largest waves
isolated to the northern lakeshore. As the low shifts towards New
England late Sunday into Monday, a northerly flow will become
established at 15-20 knots with waves building to 4-6 feet along the
near shore. The entire period from Saturday through Monday will
potentially need a Small Craft Advisory. By Tuesday of next week,
high pressure will return to the region, weakening variable winds to
5-10 knots.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
NY...None.
MARINE...None.
&&
$$
SYNOPSIS...Sullivan
NEAR TERM...Kahn/Sullivan
SHORT TERM...Campbell
LONG TERM...Campbell
AVIATION...Kahn
MARINE...Campbell
Area Forecast Discussion...UPDATED
National Weather Service Quad Cities IA IL
814 PM CDT Thu Aug 15 2024
.KEY MESSAGES...
- A severe risk remains through 11 pm timeframe with isolated to
widely scattered thunderstorms. Hail and damaging winds are
the main threats.
- A pattern change will bring mainly quiet weather to the area
Saturday night through next Thursday. Temperatures look to
be near normal.
&&
.UPDATE...
Issued at 813 PM CDT Thu Aug 15 2024
Severe Thunderstorm Watch 623 remains in effect for southeast
Iowa and northeast Missouri until 11 PM CDT tonight. Storms
continue to develop across the area ahead of a eastward moving
cold front but have struggled to strengthen to severe limits in
eastern Iowa and northeast Missouri. An inversion exists on the
00 UTC DVN sounding around 840 mb. There are steeper lapse
rates above the inversion resulting in most unstable CAPE to
around 2800 J/KG. Model soundings do show a cooling or weakening
of the inversion. Low level flow is weak but mid to upper level
flow is faster resulting in 0 to 6 km shear of 40 to 45 knots
mostly in the mid to upper levels. CAMs have been supportive of
some increase in coverage of these storms through 10 PM. Think
that hail and damaging winds are the main threat from any storms
that intensify this evening.
Winds are forecast to remain light across the area tonight and
given recent rains and abundant low level moisture patchy to
areas of fog are possible tonight after 3 AM.
&&
.SHORT TERM /THROUGH FRIDAY/...
Issued at 258 PM CDT Thu Aug 15 2024
Tonight, uncertainty remains with possible storm development
after 6 pm in western parts of the CWA. Trends of the HRRR have
been to delay the time of development, which is now showing
closer to 6 or 7 in our western CWA. The NAMNEST has only shown
some activity in the far SW after 8 pm. MUCAPE values of 2 to 3K
J/kg build into the area late this afternoon and evening. This,
along with mid level lapse rates over 7 C/km and moderate shear,
will all some supercells to be possible with strong winds,
hail, and tornadoes all a threat. The caveat is whether the
clouds that have been over the area most of the day will clear
in time for needed heating for development. Some temps in the
low 80s are seen in south central IA as of 2 pm. Moisture is
plentiful, with dew points in the lower and middle 70s area
wide. Due to these uncertainties, kept POPs in the chance
category. As for timing, it looks like areas west of the MS
River will see activity from 6 pm to 10 PM, with the eastern CWA
seeing it 9 pm to about midnight or 1 am. Overnight, any
showers or storms will exit to the east. Some patchy fog is
possible overnight, but left mention out of grids for now. Lows
will be in the 60s.
Friday, a secondary cold front will sweep across the area as
the surface low moves across northern WI. Sunshine will prevail
south of Highway 30, while clouds and even some shower and
thunderstorm chances will be possible to the north. SPC has NW
IL in a marginal risk area for wind gusts and hail. Highs will
top out in the lower 80s north to upper 80s south.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 258 PM CDT Thu Aug 15 2024
Largely quiet weather dominates the Quad Cities CWA in the long
term as the upper low currently situated over the ND/MN border
slowly migrates east over the next several days putting the area
into northwest flow. Temperatures are expected to sit generally
right around average through Tuesday with highs in the upper
70s/lower 80s and lows in the upper 50s/lower 60s. Temperatures,
combined with manageable humidity levels (especially early next
week), should make for overall pleasant weather. The focus over
this weekend will be on the upper low Saturday as it pushes
into Lower Michigan, which could provide enough forcing for a
few wrap-around showers over the far eastern portions of our
area. The most favored time for shower activity comes during the
daytime hours on Saturday. Still, generally low chances (<35%)
of precipitation exist, so not expecting anything in the way of
widespread rainfall.
Shower chances diminish Sunday and beyond as the upper low exits
and high pressure builds in. Mid-level ridging builds in by midweek
which will nudge temperatures back up into the upper 80s late
week.
Siemianowski
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 632 PM CDT Thu Aug 15 2024
TAFs are currently VFR ahead of a cold front that is moving
across central Iowa. Isolated showers and thunderstorms are
possible through 06 UTC with the best chance currently at KCID
from 1 to 3 UTC. Periods of MVFR to IFR conditions are possible
in any showers and storms. Stronger thunderstorms could produce
winds up to 40 knots but confidence is low on what TAF sites
this would occur at. Conditions will improve to VFR after 06
UTC and continue through the remainder of the period. Winds will
turn to the west behind the front with gusts up to 20 knots
possible after 15 UTC on Thursday.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
UPDATE...Cousins
SHORT TERM...14
LONG TERM...12/14
AVIATION...Cousins
Area Forecast Discussion
National Weather Service Glasgow MT
246 PM MDT Thu Aug 15 2024
.DISCUSSION...
KEY MESSAGES:
- Surface smoke moving in from Canadian wildfires has prompted a
Dense Smoke Advisory and Air Quality Alert through Friday afternoon.
- A wetter Friday is in store for much of northern Montana, with
the greatest chances for a wetting rain highest across Phillips
County (40% to 60% chance of exceedance).
- Hint of a line of storms developing across the island ranges
Friday afternoon with severe wind gusts being the biggest
concern.
- A slight warming trend through the weekend brings the return of
widespread highs in the 90s.
WEATHER PATTERN OVERVIEW:
A 500 hPa trough in the Gulf of Alaska will move south in the next
24 hrs, parking itself off the Washington coastline, cutting off
from the jet stream, while a shortwave trough traverses the Great
Plains and parking itself in the ECONUS, setting up an Omega
Block pattern.
Being downstream of the western-most cutoff low pressure will
lead to enhanced upper-level divergence and increased PoP chances
across northern Montana on Friday. The probability of a wetting
rain (at least a tenth of an inch of rainfall) on Friday ranges
from 40% to 60% across the western half of the CWA, and 20% to
40% south and east of Glasgow. For Friday afternoon and evening,
some CAMs are hinting of a line of showers and thunderstorms
(possibly with some bowing hinted in the 16th 00Z HRRR run).
Latest RAP13 forecast soundings in our western zones show
relatively dry low and mid- levels, indicative of severe wind gust
concerns. Will have to monitor this trend carefully.
By Saturday, 500 hPa heights increase, leading to drier conditions
and temperatures increasing as high as the mid-90s, as per the NBM
mean.
FORECAST CONFIDENCE & DEVIATIONS:
Main change from the NBM in the short term forecast is adding in
the latest HRRR/RAP13 surface smoke guidance into the Weather and
Visibility grids. The source of the smoke for this next batch of
smoke and haze today and into Friday comes from the wildfires
across the far northern Canadian Prairie. The concentration of the
particulate matter will be much higher than recent days and is not
being captured well without a concentration formula adjustment
based on current observations.
With respect to high temperatures from Sunday onward, the
probability of reaching 100F for max temperatures is highest for
locations in lower elevations of adjacent river valleys, though
these probabilities of exceedance do not go above a 20% chance. We
will have to carefully monitor the trends for the 500 hPa high
pressure and how much heights increase in subsequent model runs
and to see if we creep back up to the 100s.
-Enriquez/Zanker
&&
.AVIATION...
UPDATED: 2000Z
FLIGHT CAT: Mainly MVFR - IFR
DISCUSSION: Mostly clear skies are expected through Friday morning
above wildfire smoke filtering in from Canada. This will lead to
periods of IFR visibility, particularly after sunrise on Friday
after some improvement this evening. By 00Z Saturday, the next
round of scattered thunderstorms will approach the TAF sites from
the west.
WINDS: North at 10-15 knots becoming east at 5-10 knots around 06Z.
&&
.GGW WATCHES/WARNINGS/ADVISORIES...
Dense Smoke Advisory until 6 PM MDT Friday for Central and
Southeast Phillips-Central and Southern Valley-Daniels-Dawson-
Eastern Roosevelt-Garfield-McCone-Northern Phillips-Northern
Valley-Petroleum-Prairie-Richland-Sheridan-Southwest Phillips-
Western Roosevelt-Wibaux.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Hastings NE
707 PM CDT Thu Aug 15 2024
...Aviation Update...
.KEY MESSAGES...
- A round of isolated to scattered thunderstorms possible very
late tonight, but moreso during the day on Friday,
particularly for areas SW of the Tri-Cities. Another Marginal
Risk of severe with this activity.
- Mainly quiet and seasonable Friday night through Sunday.
- Amplified NW upper flow could lead to a series of upper
disturbances early to middle of next week and off and on rain
chances. Confidence on coverage/timing details very low.
&&
.DISCUSSION...
Issued at 425 PM CDT Thu Aug 15 2024
A potent, but compact, upper vort lobe is moving E through the
Siouxland area and has been responsible for some isolated
thunderstorms this afternoon. There remains some agitated CU
along a subtle wind shift/outflow from earlier activity -
roughly along the Platte River. Continued heating ahead of this
wind shift could still spark another thunderstorm or two through
6-7PM, but this appears very slight chance (only ~20%) and
conditional as the primary upper forcing and associated mid
level cooling is steadily shifting E away from the area. CAMs
have struggled to get a handle on activity today, but where they
have been at least consistent on a run to run basis is that
development along the boundary this eve will be sparse, at best.
After a quiet late eve and most of the overnight, the next
chance for iso-scat convection will move into far SW portions of
the CWA around dawn. This will be associated with a weak upper
disturbance interacting with the deep layer moisture gradient,
or elevated warm front. The LLJ remains pretty weak in our area,
but the veering nature could help to push/develop activity a bit
further E during the AM. Guidance is in pretty good agreement
that the brunt of convection will remain SW of the Tri-Cities,
but is somewhat mixed on the overall coverage and organization.
There does appear to be a non-zero risk for some strong or
severe storms to develop on Friday along the instability
gradient, but this looks to be conditional on overall weak
forcing. Should a storm tap into the instability (1000-2000 J/kg
of MUCAPE), there would be strong effective shear to work with
(esp. by August standards) at around 50-60kt. This could easily
allow for storm organization into supercells and pose a risk for
large hail. The greatest chances from the ensembles is closer to
or S of I-70, but the 18Z HRRR is close enough to esp. Rooks Co
to warrant some concern. This would be somewhat unusual timing
of late AM into early aftn.
Otherwise, looks to be fairly quiet Fri PM through the weekend
with seasonably comfortable temperatures (highs in the 80s) and
humidity. The upper pattern will really amplify over the
weekend, with deep troughing over the E 1/3rd of the CONUS, and
strong upper ridging along the Rockies. This should keep the
really active and cool conditions well to the E, and the real
hot temperatures to the SW over the central/southern High
Plains...leaving the local area in between in mainly near normal
temps. The deep layer moisture axis will remain close enough to
the area, esp. considering what should be a stream of weak upper
disturbances as there typically are in NW flow, to cause some
shower and thunderstorm chcs off and on next week. In theory,
just about any disturbance could induce enough WAA/isentropic
lift to produce elevated convection, particularly during the
overnight/AM hrs and over the W half of the CWA. So overall, the
pattern will favor seasonably comfortable temperatures and off
and on rain chances next week, but the details of which are
just too difficult to pin down this far out.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 706 PM CDT Thu Aug 15 2024
For KGRI/KEAR Airports:
- General overview:
This is a high-confidence VFR ceiling/visibility forecast, and
at least the vast majority of the period will surely be
dry/thunderstorm-free. However, there are some uncertainties
with this during the daytime hours Friday, as there is a
possibility that especially KEAR could be brushed by some
passing shower/weak thunderstorm activity. Barring any
unforeseen convective influences, winds should not be much of an
issue throughout, with sustained speeds commonly at-or-below
7KT and direction largely from some variation of westerly.
- Ceiling/visibility/precipitation details:
With the low-levels/boundary layer not as moist/humid as 24
hours ago fog should not be an issue heading into Friday
morning, thus have rather high confidence in VFR visibility
throughout. As for ceiling, while confidence is also high in
VFR, much of the latter half of the period (Friday daytime) will
likely feature quiet a bit of mid-high level cloud cover (mainly
at-or-above 10K ft.). As for shower/thunderstorm potential,
especially KEAR could reside near the east-northeast fringes of
potential activity, particularly between 15-21Z. As a result,
later TAFs may need to consider at least basic "vicinity"
(VCSH/VCTS) inclusion, but given this potential is currently
beyond the first 12 hours and confidence in occurrence is less
than 50% have held off for now. IF thunderstorms do occur, they
should be of the weaker/non-severe variety.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
DISCUSSION...Thies
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Grand Rapids MI
921 PM EDT Thu Aug 15 2024
.KEY MESSAGES...
- Chances of showers and thunderstorms through the weekend
- Cooler than normal much of next week
&&
.UPDATE...
Issued at 921 PM EDT Thu Aug 15 2024
Widespread coverage of showers associated with lead shortwave,
elevated warm front, and incoming axis of higher PWATs continues
to slowly march across the area. There has been no thunder at all
with this activity as the leading edge of any respectable MUCape
values is still well to our west. The risk for a tstm does
increase late tonight as RAP MUCapes of 500-1000 J/KG arrive and
the next shortwave currently over Iowa/srn MN approaches. Only
change to the fcst was to drop the mention of thunder in the
grids until after 06Z and that was done earlier this evening.
&&
.DISCUSSION...
Issued at 245 PM EDT Thu Aug 15 2024
- Chances of showers and thunderstorms through the weekend
As the low pressure system tracks into the region from the west
through Friday, it will bring with it moisture, lift and
instability. SPC HREF 4 hr thunder probabilities don`t really
increase significantly until after 08z tonight. They remain high
until mid morning when they then decrease steadily. So it looks
like a break in the storm activity is expected late morning into
part of the afternoon. We do destabilize in the afternoon with
surface based CAPE values likely to reach 1000 J/kg away from Lake
MI. Forcing is shown to be weak then. So if storms do develop
then, then should remain isolated/scattered during the mid to late
afternoon hours. The main mid level wave/vort max arrives from
west in the 00z-04z Sat period. There`s a signal in the models for
a cluster of storms to accompany this feature. The SPC HREF 4h
thunder probabilities increase once again. LPMM 24 hr qpf values
show small swaths of values over 2 inches 00z Fri to 00z Sat so
locally excessive rain may occur. We will feature relatively high
POPs trough the period as a result.
Vertically stacked and slow-moving area of low pressure will be
centered over Lower Michigan on Saturday and southwest Ontario on
Sunday. Scattered showers or thunderstorm cells will tend to be
reinvigorated with daytime heating, with greater precip chances
inland and away from Lake Michigan. CAPE will be more modest than
Friday, and shear will still be limited, but 20-25 knot winds in
the lower atmosphere not far off the surface may allow for
localized gusts over 30 mph to mix down with some showers. Though
high temperatures will be cooler than normal, dew points will
still be on the muggier side.
- Cooler than normal much of next week
A tendency for synoptic-scale ridging over the Rocky Mtn front
range and troughing over the eastern Great Lakes early-mid next
week will provide a flow of drier and cooler-than-normal air as
high pressure builds in the Midwest. Good confidence among the
ECMWF and GFS ensembles for highs mostly in the mid 70s. A small
minority of members give rain chances Tuesday night or Wednesday
depending on strength and location of shortwave troughs moving
over the ridge.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 723 PM EDT Thu Aug 15 2024
No significant changes to the going forecast. A band of showers
crosses through West Michigan through the evening with more
scattered showers behind it. Instability builds in early Friday
morning bringing thunder chances with a cluster of showers moving
through in the 08z-12z range. Have VCTS in the TAFs given the more
scattered nature of thunderstorms. Isolated thunder is possible
earlier but confidence is too low for TAF inclusion. MVFR and
lower visibilities are possible in any thunderstorms. A few hours
of MVFR cigs are likely Friday morning, longest at MKG.
Uncertainty exists in how long MVFR cigs continue into the morning
as it will depend in part on how much rainfall occurs. Even worst
case scenario, any MVFR cigs lift to VFR by the afternoon. An
isolated shower or storm is possible in the afternoon but coverage
is to low to warrant TAF inclusion at this time. The next
organized complex of storms holds off until after 00z Friday.
&&
.MARINE...
Issued at 245 PM EDT Thu Aug 15 2024
The winds and waves will remain elevated through much of tonight
as the pressure gradient tightens up as a result of the
approaching low pressure system We did slightly expand the
hazardous beach/boat risk this afternoon based on the latest model
and observational trends. On and off hazardous conditions are
predicted into the weekend so we will adjust headlines as we get
closer to those periods.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 2 AM EDT Friday for MIZ037-043-050-
056.
MARINE...Small Craft Advisory until 2 AM EDT Friday for LMZ846>849.
&&
$$
UPDATE...Meade
DISCUSSION...MJS/CAS
AVIATION...Thomas
MARINE...MJS
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
824 PM CDT Thu Aug 15 2024
.KEY MESSAGES...
- Main window for severe weather tonight is expected between 9 pm
and 2 am, with scattered wind damage the primary concern.
- Some shower and storm activity will linger Friday and Saturday,
as a slow moving upper low drifts across the Great Lakes.
- An extended period of cooler conditions is expected Saturday
into the middle of next week, with temperatures about 5-8
degrees below seasonal normals.
&&
.UPDATE...
Issued at 822 PM CDT Thu Aug 15 2024
This evening, water vapor imagery reveals a broad upper low
spinning across portions of the northern Great Plains and Upper
Midwest with a shortwave trough ejecting from the base of this
feature across IA/MO. Further southeast, a modest 20-25kt low
level jet will focus moisture transport across portions of SE MO
into Srn IL. These two features should support scattered
convection across portions of the region overnight, though the
activity on the LLJ seems favored to stay south of the forecast
area. Latest RAP holds on to moderate instability through the
night with dew points in the mid 70s contributing to MLCAPE values
around 1500-2000 J/kg while deep layer shear values of 30-35 kt
will support some stronger or severe storms. A number of CAMs
continue to try to congeal upstream convection into a line as it
moves across central Illinois, though the latest HRRR keeps
convection more scattered in nature. While coverage still remains
uncertain, shear and instability parameters do continue to
support the potential for severe storms tonight.
Deubelbeiss
&&
.SHORT TERM... (Through Late Friday Afternoon)
Issued at 300 PM CDT Thu Aug 15 2024
Lingering showers early this afternoon have finally been showing
more of a diminishing trend, with most of the activity now around
Champaign and Danville. Some clearing has occurred over western
Illinois into adjacent areas of Missouri, allowing surface based
CAPE`s to reach around 3000 J/kg per recent SPC mesoanalysis.
Convective initiation is expected over central Iowa and north
central Missouri over the next few hours, which should arrive in
western Illinois toward 9-10 pm. A few of the CAM`s have also been
showing development over south central Illinois late in the
afternoon, and surface analysis does show a weak north/south
boundary roughly near Vandalia, which could be a source of
initiation. Will keep the lower (30%) PoP`s going in that area
for that reason, with most of the PoP adjustments focused on the
timing of the main convection later in the evening. Latest Day1
convective outlook maintains a level 2 risk of severe weather,
with the main window focused between 9 pm and 2 am.
Upper currently over northeast North Dakota is progged to move
to central Wisconsin by Friday afternoon. Much of the convective
activity should be out of our area early Friday morning, but a few
storms can`t be ruled out late afternoon or early evening as the
attendant surface boundary swings through the region. Think the
best chance of this occurring will be near and north of I-74 near
a small lower level jet max dropping into northern Illinois.
With the slower arrival of the main cold front, temperatures
Friday should still reach the mid 80s. However, some drier air
will begin to work in during the afternoon, easing the heat index
back a bit.
Geelhart
.LONG TERM... (Saturday through Next Thursday)
Issued at 300 PM CDT Thu Aug 15 2024
Upper level progression of systems will be slow through the
weekend, as Hurricane Ernesto lifts northward across the western
Atlantic. This will result in the upper ridge amplifying across
the Rockies. Broad troughing will continue over the eastern U.S.
into early next week. Between these two, northwest flow into the
Midwest will provide a cooler weather pattern that persists
through this period. Highs in the upper 70s to around 80 degrees
are expected, with dew points dropping into the 50s by early
Monday. Rain-wise, the slow progression of the upper low over the
Great Lakes will provide a risk of scattered showers on Saturday
and perhaps into early Sunday, with surface high pressure
providing dry conditions after that.
Geelhart
&&
.AVIATION... (For the 00z TAFs through 00z Friday Evening)
Issued at 630 PM CDT Thu Aug 15 2024
VFR conditions and southerly winds will be in place this evening
as thunderstorms develop over Iowa and Missouri. These storms
will move across central Illinois overnight. MVFR ceilings are
expected to linger behind the storms for several hours Friday
morning. Winds will set up out of the west mid to late Friday
morning and conditions should return to VFR the remainder of the
period.
Deubelbeiss
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1033 PM EDT Thu Aug 15 2024
.KEY MESSAGES...
- Humidity, along with the possibility of showers and
thunderstorms, will increase Friday and last into Saturday night.
- Below normal temperatures are expected Sunday through Wednesday
behind a cold front passage late Saturday night.
- Showers and thunderstorms will remain possible Sunday and
Monday, especially in the afternoon and early evening, with a
drying trend for Tuesday into Wednesday.
&&
.UPDATE...
Issued at 1033 PM EDT THU AUG 15 2024
Update this evening extends into tomorrow. Based on current
trends in temps and sky cover made some adjustments to the
overnight lows, including a non-diurnal trend with additional
cloud cover that will be overspreading the area over the next few
hours. Overnight lows will like be reached a little after
midnight, begin to level off, and then to increase a bit in the
hours leading up to dawn. Also, after getting a quick peak at the
0Z NAM, RAP, and hrrr run, model solutions are suggesting the
potential of some convection firing late tonight...in the hours
leading up to sunrise, generally between 4 and 8 am across much of
the forecast area. After this early morning convection, a second
round appears to take aim at the area through the late morning and
early afternoon. With the expected timing of the additional cloud
cover and convection, trended afternoon highs across our east and
southeast down a bit. However, there could be some late afternoon
partial clearing and the chance for some recovery of temperatures.
Thus only tweaked highs down just a few degrees over areas of
interest. Adjustments to the forecast and updated zones have been
issued.
UPDATE Issued at 700 PM EDT THU AUG 15 2024
Hourly temperatures have been falling a bit quicker than
previously forecast, so this trend will need to be watched closely
over the next few hours to determine whether or not tonights low
temperatures need to be adjusted. Used the most recent obs to
freshen up the hourly grids and establish new trends.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 350 PM EDT THU AUG 15 2024
The short term portion of the forecast looks to be quite active, as
a vigorous area of low pressure moves through the Great Lakes region
to finish out the week. The weather should remain quiet for most of
tonight, as the aforementioned system moves slowly our way. The
models differed a bit in their handling of this system and its
evolution and associated precipitation. The NAM12, NAMNEST, GFS, and
WPC guidance were all quite wet across our region, especially Friday
and Friday night, during frontal passage. The SREF and RAP models
were not as wet, and had larger time gaps between precipitation
episodes than the other four model mentioned above. With a general
consensus amongst a higher number of models, decided to go with the
wetter solutions at this time. The latest model QPF also differed a
bit across the area, with multiple bullseyes of higher amounts
showing up across our area Friday and Friday night, likely due to
the models difficulty in handling convection during that time.
However, with model soundings precipitable water values between 1.50
and just over 2 inches common across our area Friday and Friday
night, chose to go with the higher model QPF from both the NAM12 and
GFS solutions, with a swath of higher amounts across our southern
tiers of counties from the Hal Rogers Parkway southward to the
Tennessee border.
There is still a marginal risk of excessive rainfall across portions
or all of our forecast area Friday and Friday night, along with a
marginal risk of severe weather. The probability of severe storms on
Friday is quite low at this time, or roughly a 5% chance. As for the
chances of excessive rainfall that could lead to flooding, there is
currently a 5 to 14% chance of that occurring to end the week, which
is also quite low. As always, everyone should remain aware of the
danger posed by cloud to ground lightning that could occur with any
thunderstorm.
Warm and humid conditions will continue through the end of the week.
Highs on Friday will likely be several degrees cooler than what we
experienced today, but with dewpoints expected to increase into the
upper 60s and lower 70s on Friday, it will be quite steamy outside.
The high moisture levels will aid in thunderstorm formation and
maintenance as well.
.LONG TERM...(Saturday through Thursday)
Issued at 347 PM EDT THU AUG 15 2024
There is good agreement among the ensemble and deterministic
solutions for an upper low to push across the Great Lakes, with the
trough axis swinging through the Ohio Valley. This coupled with a
nearby frontal boundary will keep the weather active to begin the
period. Even so, the overall evolution in convection remains in
question, as you could begin the day at times with early morning
convection. This will certainly play a roll into how much
instability can be recovered in the afternoon hours. The EFI does
show decent signal for the climatologically significant
combination of CAPE and shear on Saturday, but when looking at
CAPE alone it was a much lesser signal. This means the shear
seems to be driving the values up more and the jet energy noted in
the various solutions is one that would support deeper layer
shear. Given the uncertainties mentioned, SPC did keep a marginal
risk going for Saturday. In terms of flooding, the concern here
would be places that can see multiple iterations of storms, so
overall threat right now is lower. Outside this expect near normal
temperatures (mid to upper 80s) Saturday depending on cloud
cover.
This trough axis will continue to swig through the area and lower
heights some as it does. This will keep the weather active through
Monday. The highest chances of rain will be Sunday when chances
of rain peak at around 50-90 percent particularly in the far
eastern parts of eastern Kentucky. By Monday, afternoon highs will
be running around 10 degrees below normal, with highs in the mid
to upper 70s in most locations.
A cold front or post frontal trough will user in much dryer air by
Tuesday. The PWATs will be running in the 25th percentile range for
this time of year at around 0.75 inches. There is good agreement on
an area of high pressure pushing into the Great Lakes providing
northerly flow at the surface and will lead a much cooler night
Tuesday into Wednesday morning. The dewpoints are expected to mix
out well under deep mixing on Tuesday and did adjust this down
given the usually too hot NBM deterministic toward the 10th
percentile. Given this lowered valleys into the upper 40s to lower
50s for overnight lows by Wednesday morning. This cooler valley
trend was also noted in the COOP MOS. We will begin to rebound
through the week to near normal for afternoon highs, with
overnight lows remaining in the low to mid 50s in most cases. The
other good news is it should be nice and dry Tuesday into Thursday
under the northerly flow and lower PWAT values.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 756 PM EDT THU AUG 15 2024
VFR conditions are expected as a predominant flight condition
through the bulk of the period. However, guidance suggests there
could be some short periods of high end MVFR conditions, mainly
associated with showers and especially thunderstorms that develop
across the area through the 10Z-18Z time frame as a slow moving
surface cold front approaches form the west. FROPA is not expected
through the area until Saturday night, or around 24 hours beyond
the end of the current forecast window. Winds will be light and
variable, around 5 kts or less until after sunrise, when a
southwest gradient wind between 5-10 kts develops ahead of the
approaching cold front. Winds could be gusty in the vicinity of
any thunderstorms.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...RAY
SHORT TERM...AR
LONG TERM...DJ
AVIATION...RAY
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
840 PM CDT Thu Aug 15 2024
.KEY MESSAGES...
- Several rounds of thunderstorms are possible from tonight into
Friday. A few storms may be severe, and not all areas will see
thunderstorms.
- Isolated showers and thunderstorms possible over the weekend,
especially on Saturday.
- Temperatures early next week will be below average with highs
in the 70s to around 80.
&&
.UPDATE...
Issued at 839 PM CDT Thu Aug 15 2024
There are spotty weak returns that remain on radar passing over
the area. However, as soon as they develop, the quickly fall
apart. Isolated to scattered sprinkles to light rain is possible
(15 to 20 percent chance) for the next couple hours. There is a
sharp instability gradient from northwest to southeast draped
just along our western forecast area. Given the lack of
instability presently, thunder is not expected until after 9PM,
first arriving around I-39 before moving east.
Most attention on radar is focused on the thunderstorm activity
over eastern Iowa and northeastern Missouri. These storms are
expected to move eastward through the overnight. As better
instability moves into the area, there is the potential for some
development out ahead of the current activity, but the overall
coverage of storms is expected to be scattered at best. Given
how cloudy it was during the day which inhibited heating and
provided weaker low level lapse rates as well as slightly weaker
forcing, confidence is lower on the risk for severe weather.
However, given stronger effective shear and enough moisture
and instability present, stronger storms could develop where
some small hail or localized wind gusts could necessitate
the issuance of a severe thunderstorm warning. That being said,
thunderstorm activity is expected through the overnight before
it slowly moves east of the forecast area after daybreak
allowing for improving conditions for the morning commute.
DK
&&
.DISCUSSION...
Issued at 230 PM CDT Thu Aug 15 2024
Through Friday Night:
Regional water vapor and radar imagery depicts an elongated area of
low pressure centered over the Midwest with several embedded
shortwaves pinwheeling around the perimeter of the circulation. The
first shortwave is currently moving through the Lower Great Lakes,
and continues to support scattered showers across northern Illinois
and northwestern Indiana. Mostly cloudy skies have prevented
highs from climbing much above the low to mid 70s, altogether
making for a cool, and somewhat wet, day. With the increasingly
tight pressure gradient being forced by the approaching surface
component of the broad upper-level low in the northern Plains,
south to southeast winds remain breezy and continue to build up
waves on Lake Michigan. A Beach Hazards Statement remains in
effect from Chicago to Waukegan (and points northward) though
this evening.
The next upper-level shortwave and associated upper-level jet speed
max is easily identifiable in radar and satellite imagery near
eastern Nebraska, and will approach our area after dark. Although
forecast confidence in exactly how and were thunderstorms develop
remains on the lower side of the spectrum, an ensemble of convective
allowing models favors at least scattered thunderstorms moving
through the general area from about midnight to daybreak along the
nose of the aforementioned jet speed max. While thunderstorms will
likely be rooted above the near-surface layer, cloud-layer shear >50
kt should support semi-organized clusters capable of producing
frequent lightning, heavy downpours, locally gusty winds, and small
non-damaging hail. One or two storms may briefly acquire severe
caliber hail or winds, though such a threat should be localized. The
SPC Level 2/5 threat level is probably a category too high, but
should cover the threat well.
All remaining showers and storm should scoot east and away from our
area after daybreak allowing for clouds to scatter by mid-afternoon.
Boundary layer warming with surface temperatures climbing into the
mid 80s and lingering low-level moisture should allow for a pool of
1000+ J/kg of MLCAPE to develop by mid-afternoon ahead of the third,
and final, shortwave (currently meandering across North Dakota).
With a stout pop of southwesterly (and veering) low-level winds
ahead of the shortwave, forecast kinematic profiles within the
instability axis tomorrow afternoon do raise eyebrows and appear
supportive of low-topped supercell structures, given some 25-30kt of
shear and 150-200 J/kg of SRH in the lowest 3 km (assuming a
southeasterly storm motion). As a result, thunderstorms tomorrow
afternoon and evening may carry a threat for localized severe
weather in the form of brief tornadoes, damaging hail, and damaging
winds.
Now, a clear failure mode for thunderstorms (both coverage and
intensity) tomorrow afternoon and evening will be the quality of low-
level moisture, as the normally trustworthy HRRR and RAP depict
aggressive downward mixing of mixed-layer dew points in response to
breezy west winds. Forecast soundings taken from more moist CAMs
also depict a notable dry pocket within the mixed layer, which would
lead to similar, correspondingly low, values of MLCAPE. With that
said, even just 500 J/kg of MLCAPE may be enough for sustained
convective attempts given the deep-layer shear won`t be overly
strong (to enhance the entrainment of dry air and "shear apart"
initial updrafts). However, the signal for less-than-stellar
quality moisture in the mixed layer does suggest coverage of
thunderstorms may be isolated to scattered at best, and
primarily confined to areas along and north of I-88 in closer
proximity to the core of forcing. For now, the SPC Level 1/5
threat level for tomorrow afternoon and evening appears
appropriate, as adjustments (both upward or downward) may be
needed as the integrity of mixed-layer moisture becomes more
clear.
Borchardt
Saturday through Thursday:
The upper trough responsible for today`s rain can be found
spinning over the North Dakota/Manitoba border this afternoon.
It will gradually work its way eastward over the next several
days traversing the Great Lakes over the weekend. After dragging
a cold front across the area Friday night providing a chance
for some stronger storms (see short term discussion above), the
low level circulation will remain over Lake Michigan during the
day on Saturday. The broad forcing for ascent will help pull
precip chances into this weekend. Forecast soundings also remain
relatively moist on the backside of the system which may make
it easier for any subtle forcing mechanisms to stir up some
showers. A couple of thunderstorms will be possible during the
afternoon as well after heating can destabilize the low levels
some. Thermo profiles though remain poor aloft and overall
unfavorable for robust convection, so none is anticipated at
this time. Coverage looks isolated to widely scattered but may
be maximized around the lakeshore nearer to the circulation.
Conditions will be seasonably cool over the weekend following
Friday`s cold front. Similar highs in the middle and upper 70s
are expected both days. Onshore flow will keep temperatures a
bit cooler near the lake on Sunday. A rather tight MSLP gradient
between the departing low and an impending high to the
northwest will bring about breezy conditions over the weekend as
well. As a result, building waves may make for dangerous
swimming conditions (mainly Sunday into Monday). A few
additional showers may go up during the day on Sunday, but with
high pressure and drier air encroaching from the west, chances
are primarily focused across the eastern half of the CWA.
After the trough finally makes it out of the region early next
week, a sizable upper ridge will dominate the western CONUS
spreading high surface pressure across the Great Lakes region.
This is expected to keep precip chances minimal and provide lots
of sunshine during the earlier half of the week. Highs will be
pretty steady in the middle to upper 70s each day before
conditions look to heat up after mid- week as the ridge meanders
eastward.
Doom
&&
.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 616 PM CDT Thu Aug 15 2024
Aviation Forecast Concerns:
- MVFR ceilings may improve for a time this evening, though
patchy MVFR conditions likely will later tonight especially
for KRFD.
- Scattered thunderstorm potential roughly 04-08Z window at
KRFD and 05-09Z for KORD/KMDW. Somewhat low confidence in
coverage over terminals.
- Chance of additional scattered thunderstorms Friday evening.
Surface low pressure was centered over northwest MN early this
evening, with a warm front extending into northern IL. A cold
front trailed farther west across IA and eastern KS. Warm/moist
advection in the vicinity of the warm frontal zone has
maintained extensive cloud cover across the region, though most
of the earlier showers have moved east of the area since this
afternoon. A few spotty showers may linger this evening, though
MVFR cloud cover will likely erode for a time from the
southwest across most of the terminals (KRFD may have the
toughest time losing the MVFR deck). Surface winds from the SSE
should eventually turn more SSW late this evening.
We continue to monitor scattered thunderstorm development
upstream across eastern IA early this evening, which is
expected to eventually increase in coverage and spread east
tonight in association with a mid-level disturbance and ahead of
the cold front. High-res CAM guidance generally suggests the
main window for a few hours of thunder in the terminals to be
after 03-04Z for KRFD and after 05Z-06Z for the Chicago metro
sites. There is some spread in the degree of coverage between
models however, so while confidence in thunder and the general
timing is fairly high, confidence in coverage across the
terminals is lower.
Winds will become more SW to WSW Friday (with gusts 20-25 kt in
the afternoon) as the weak cold front moves through the area.
Any lingering MVFR ceilings early in the day should mix out and
scatter to VFR. Another mid-level disturbance wrapping southeast
across the area later in the day may produce some additional
scattered thunderstorms for the terminals by early Friday
evening.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement until 10 PM CDT this evening for
ILZ006-ILZ103-ILZ104.
IN...None.
LM...Small Craft Advisory until 10 PM CDT this evening for Winthrop
Harbor to Wilmette Harbor IL.
&&
$$
Visit us at weather.gov/chicago
Area Forecast Discussion
National Weather Service Memphis TN
914 PM CDT Thu Aug 15 2024
...New UPDATE...
.UPDATE...
Issued at 908 PM CDT Thu Aug 15 2024
GOES-16 Water Vapor satellite trends show convective development
generally along the I-44 corridor in eastern Oklahoma and
Missouri, and additional convection also occurring over southern
Illinois. This activity is out ahead of a cold front which
extends from northeast Missouri back through southeast Kansas and
central Oklahoma. 00Z upper air analysis shows an upper-level
ridge still in place across the Mid-South. Temperatures are still
quite warm in the 80s across most locations as of 8 PM CDT.
The 00Z NAM is suggesting minimal convective potential if any
overnight due to the very warm mid-level temperatures and ridging
present across the area. The 00Z HRRR and the Hi-Res WRF-FV3
support this limited convective potential to an extent until after
sunrise when mid-level height falls begin to spread into the
Tennessee Valley. Consequently, some adjustments will be made to
lower rain chances to reflect current trends. Ample instability
present and 25 to 30 kts of shear are sufficient for a strong to
isolated severe thunderstorm if any sustained convective
development does occur.
Updated grids will be available shortly.
CJC
&&
.SYNOPSIS...
Issued at 331 PM CDT Thu Aug 15 2024
Hot and humid conditions will continue across the region
tomorrow, as heat headlines will remain in effect through 9 pm
Friday. A wet and unsettled pattern will begin later tonight and
may last through Saturday as a slow moving cold front advances
through the Mid-South. Cooler temperatures and dry conditions are
expected behind the front and should last through mid next week.
&&
.DISCUSSION...
(This evening through next Wednesday)
Issued at 331 PM CDT Thu Aug 15 2024
Mid-level water vapor analysis depicts that shortwave ridging is
continuing to build across the region, resulting in hot and humid
conditions across the Mid-South today. Heat index values as of the
discussion range from near 100 to near 110 degrees. Given the
fact that temperatures will remain fairly warm overnight and
dangerous heat index values are expected tomorrow, the Heat
Advisory and Excessive Heat Warning have been extended until
Friday night at 9 pm. There is some uncertainty with these heat
headlines as some areas of the Mid-South may experience convective
activity that could result in areas not reaching criteria.
Additional heat headlines are possible Saturday, where moisture
pools ahead of a southward moving cold front.
Later this evening, a mid-level trough will continue advancing
from the northern Plains with a surface cold front that will move
across central Missouri. Ahead of this front, scattered
thunderstorm development is expected later tonight. There
continues to be uncertainty with respect storm coverage, timing,
intensity. However, given the fact that forecast soundings depict
a moderately unstable environment coupled with favorable effective
bulk shear values, it appears at least plausible that an isolated
strong to severe thunderstorm capable of large hail and damaging
wind gusts could occur across the northern portions of the Mid-
South. The unsettled weather pattern continues on Friday and
Saturday across the rest of the region as the front continues
moving south. Similar challenges appear present with respect to
severe potential on these days as it pertains to the location,
timing, and intensity of convection, though damaging winds and
large hail are anticipated to be the main threats with any strong
to severe storm that does occur.
Things will begin to cool off as the front pushes through the
Mid-South on Sunday, eventually bringing temperatures into the mid
80s to low 90s and dry conditions area wide by Monday. These
conditions look to persist through mid next week with mid-level
northwest flow prevailing across the Mid-South in association with
troughing persisting over the eastern US.
&&
.AVIATION...
(00Z TAFS)
Issued at 609 PM CDT Thu Aug 15 2024
Upstream convection is just firing up in southern
Illinois. This convection should not impact the terminals, and
more towards middle TN. The NAMNest seems very aggressive in MCS
impacting the northern terminals this evening, but other CAMs not
in favor. The latest HRRR did bring in a few isolated
thunderstorms just after midnight tonight near MEM, but thinking
that is influenced by the aggressiveness of the NAM. Will monitor
closely, but MKL and JBR are most likely for convection late
tonight into tomorrow morning.
DNM
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Excessive Heat Warning until 9 PM CDT Friday for ARZ009-018-
026>028-035-036-048-049-058.
MO...Excessive Heat Warning until 9 PM CDT Friday for MOZ113-115.
MS...Excessive Heat Warning until 9 PM CDT Friday for MSZ001-007-008-
010>012-020-021.
Heat Advisory until 9 PM CDT Friday for MSZ002>006-009-013>017-
022>024.
TN...Excessive Heat Warning until 9 PM CDT Friday for TNZ001-002-019-
048-049-088.
Heat Advisory until 9 PM CDT Friday for TNZ003-004-020>022-
050>055-089>092.
&&
$$
PUBLIC FORECAST...JPR
AVIATION...DNM
Area Forecast Discussion
National Weather Service Morristown TN
1032 PM EDT Thu Aug 15 2024
...New UPDATE...
.UPDATE...
Issued at 1023 PM EDT Thu Aug 15 2024
Forecast is on track tonight with mostly clear sky conditions. The
main impacts will be on Friday when a line of showers and
thunderstorms is expected to move across the area. Exact timing is
uncertain, but recent CAMs are showing additional convective
initiation associated with the convective cluster currently
across Missouri. This cluster would develop into an MCS and move
towards our area mid-day to early afternoon on Friday.
While this will need to be monitored, the overall severe risk
continues to be marginal. The upper shortwave and PVA will be
focused north of our area across the Ohio Valley with limited to
no height falls for the East Tennessee area. This will result in
poor mid- level lapse rates and limited instability with HRRR
forecast soundings showing MLCAPE around 1000 to 1500 J/Kg with
highest values across our western counties near the Cumberland
Plateau. Effective bulk shear is also weak at around 15 to 20 kt.
While the severe potential is limited, there is still a low risk.
Even with sub- severe winds, some downed trees will be expected.
In addition, RAP forecast PW values around 2.0 to 2.2 inches will
result in heavy rain rates and localized flash flooding potential
on Friday.
&&
.SHORT TERM...
(This evening through Friday)
Issued at 300 PM EDT Thu Aug 15 2024
Key Messages:
1. Isolated showers through this evening over parts of higher
terrain.
2. Scattered to numerous showers and storms Friday, with some
strong to severe storms and localized flooding possible. Damaging
winds would be the primary threat with any severe storms.
Discussion:
The rest of this evening and tonight should be mostly quiet, with
some isolated shower development over the plateau and mountains.
At least a couple hundredths has been recorded as of this time in
some areas. Activity should wane with the loss of day time
heating. Patches of fog may also be possible due to the influx of
moisture funneling our way under calm conditions overnight.
Friday: our mostly dry spell will come to an end this weekend with
an approaching system and attendant cold front. A mid to upper
level trough is forecast to slide east across the northern tier of
the country. The low center will pretty much be stacked underneath
it. Pre-frontal showers and thunderstorms will impact the area as
early as just before or around sunrise from the west and
northwest. SPC currently has us in a MRGL risk for severe weather
and they mention the possibility of the morning convection
diurnally strengthening as we approach Friday afternoon. 20 to
30KT effective shear along with CAPE in the 1000 J/Kg range is
enough to support multicellular storms. Exact timing, evolution,
movement, and the possibility or not of multiple rounds is still
pretty unclear even with CAMs less than 24 hours out. All in all
we can expect the possibility of strong to severe storms with
damaging winds the primary threat. Heavy rainfall could also lead
to localized flash flooding. Hopefully the latter will hold off
with how dry we have lately been.
&&
.LONG TERM...
(Friday night through next Thursday)
Issued at 300 PM EDT Thu Aug 15 2024
Key Messages:
1. Scattered to numerous showers and storms Friday evening and
Saturday, with some strong to severe storms possible.
2. More scattered showers and storms possible Sunday and Monday,
with better coverage across the northern areas.
3. Higher pressure building south with a more northwest flow and
drier Tuesday and Wednesday with cooler high temperatures and low
temperatures dropping into the 50s.
Discussion:
Models in general agreement with upper low over Wisconsin and
Michigan to start the extended forecast period Friday night. The
upper low will drift, move southeast through Saturday and Sunday
opening up by Sunday night into the northeast states and digging an
upper trough across the eastern states into the TN Valley and
southeast through Sunday night. Multiple shortwaves will progress
through the NW flow and across the Tennessee Valley Friday night and
continuing through Saturday and Sunday. A cold front will be
approaching the area as well on Saturday. The trough looks to shift
eastward Monday into Monday night with improving conditions Monday
night and continuing through Wednesday.
Models are still different in the details with the timing of the
shortwaves coming through but are showing Friday evening and late
Saturday afternoon and evening as the best times for significant
rainfall and thunderstorms. Sunday the trough and cold front will
have shifted farther south with more convection south of the
Tennessee state line in MS, AL, GA and the Carolinas with the GFS
and NAM12 showing that will be where more significant convection
develops. Model runs have been showing differences so stay tuned.
With the threat for heavy rainfall some isolated flooding is
possible Friday night but a better chance will be Saturday night if
Friday night is wet too. Sunday and Sunday night into Monday expect
storms to more directly effect the northern half of the area with
another significant shortwave moving through the Ohio Valley Sunday.
Overall the atmosphere looks supportive of more organized convection
with some strong to severe storms possible Friday evening. The slow-
moving upper trough/low continues east across the Great Lakes/OH
Valley Saturday. The weak surface low over southern MI is forecast
to gradually develop into southern Canada/Ontario. The weak front
extending southward from the low should slowly move east-southeast
across the OH Valley and Mid-Atlantic into the Southeast through
Saturday night. The boundary, although not well defined and having
only modest low-level convergence, should serve as a focus for
strong to severe convection. Diurnal heating of a moist airmass
along/ahead of the front should bring weak to moderate
destabilization Saturday afternoon, even though mid-level lapse
rates should remain modest. Enhanced mid-level flow associated with
the upper trough/low should focus storms over parts of the lower OH
Valley into the TN Valley and Mid-South. But, sufficient deep-layer
shear to support some updraft organization should be present over
much of the broad warm sector. Multiple clusters may develop along
the length of the front Saturday afternoon and pose primarily an
isolated strong to damaging wind threat as they spread east-
southeast through Saturday evening. So Marginal risk is across the
forecast area. Damaging winds will be the primary severe threat with
these storms. In addition, any areas that see repeated and/or
prolonged rounds of heavy rainfall may experience localized
flooding.
Cooler temperatures will be moving in behind the front Sunday and
Monday, with temperatures at or a little below normal Sunday and
below normal on Monday. Highs Monday only in the 60s to lower 70s
higher elevations and 70s to the lower 80s. On Tuesday and
continuing into Wednesday a cooler surface high pressure will build
into the eastern Tennessee Valley and southern Appalachians.
Dewpoints will lower into the more comfortable 50s at most sites
with actual lows in the 50s Tuesday into Thursday mornings. A weak
surface trough is expected to move through the upper flow Thursday
and may trigger a few showers or storms. Temperatures will be
warming back into the mid to upper 80s Thursday.
&&
.AVIATION...
(00Z TAFS)
Issued at 724 PM EDT Thu Aug 15 2024
VFR conditions continue tonight with a low probability of fog near
the TRI terminal. Rain chances increase on Friday with VCSH from
mid-morning throughout the afternoon. Have included prob30 TSRA at
all terminals as a thunderstorm complex is forecast to move across
the region, but timing is still uncertain. SW winds remain mostly
5-10 kt with higher gusts near any thunderstorms.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 72 94 73 93 / 0 50 50 70
Knoxville McGhee Tyson Airport, TN 72 91 71 90 / 0 50 70 70
Oak Ridge, TN 71 89 70 89 / 10 60 70 70
Tri Cities Airport, TN 67 86 69 85 / 10 50 60 50
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...KS
LONG TERM....TD
AVIATION...JB
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
527 PM PDT Thu Aug 15 2024
Updated short term forecast for Thursday evening.
.SYNOPSIS...An upper level low will most likely bring a widespread
soaking rain to northwest OR and southwest WA late Saturday through
Saturday night as showers and thunderstorms move into the area. Rain
rates look to be heaviest over the Cascades, posing a threat of
debris flows over/near recently burned areas associated with ongoing
wildfires as hourly rain rates may approach 0.75 inches/hr. There is
also a marginal risk of severe thunderstorms over the Cascades and
foothills Saturday into Saturday night, as isolated damaging wind
gusts up to 60 mph will be possible with any discrete cells that are
able to form. Cool and cloudy weather then continues into the middle
of next week an onshore flow maintains the pattern in place.
&&
.UPDATE...Thursday evening...Radar and surface weather observations
from 520 PM Thursday depicted isolated light rain showers developing
in the Salem, McMinnville, Forest Grove, Hillsboro and Beaverton
area. NBM PoPs are too low at <10%, so the forecast was adjusted to
manually increase PoPs to 15-30% in the aforementioned areas. Also
included this chance for the rest of the Portland metro and the south
WA/north OR Cascade foothills as these light showers slowly shift
east-southeastward. The latest iteration of the HRRR backs this up
well, as simulated reflectivity guidance is showing these showers
moving over parts of the Portland metro between 6-8pm Thursday
evening, approaching the Columbia River Gorge and Cascade foothills
after 8pm. It appears showery activity will diminish completely by
4-5am Friday before chances for showers and thunderstorms increase
significantly late Saturday. This is discussed below in the short
term discussion. -TK
&&
.SHORT TERM...Now through Saturday Night...The short term forecast is
highlighted by increasing chances for a widespread soaking rain
across all of western WA/OR (50-80% chance) as widespread showers and
scattered thunderstorms bring a threat of heavy rain and isolated
wind damage. These showers and storms are associated with an upper
level low that models and their ensembles show lingering over the
coastal waters off the south Oregon coast. This will result in
southeasterly flow aloft across southwest WA and northwest OR,
helping to advect moisture into the area and increase instability.
Ample QG forcing for ascent is evident as well as CVA and WAA
increases ahead of an incoming trough axis and associated vort max,
resulting in notable Q-vector convergence.
The threat for thunderstorms is currently highest in the Cascades
where instability will be maximized according to the latest model
guidance (CAPE values rising to 500-1500 J/kg according to the
GFS/EURO/NAM). Strong wind shear is also evident with impressive
0-6km bulk shear values between 40-55 knots. Admittedly, there is
some uncertain regarding the exact timing of this system and which
areas will undergo enough daytime heating for these higher CAPE
values to materialize. Nevertheless, the environment is favorable
enough to support at least a 20-30% chance of thunderstorms from the
Coast Range to the Cascades, with the best chance being over the
Cascades. In fact, the Storm Prediction Center (SPC) has introduced a
marginal risk for severe thunderstorms over the Cascades/foothills,
mainly for potential isolated convective wind gusts up to 60 mph with
any discrete cells that are able to form before cells congeal into an
MCS. Regardless of the storm mode, heavy rain will be a threat given
high PWAT values over 1", fairly deep warm cloud layer depths over
7kft, and somewhat slow storm motion with cloud layer winds <20
knots. The UWWRF 1km and the NAM Nest are both showing rain rates up
to 0.75 in/hr, which is not quite high enough for debris flow
concerns over old burn areas, but is high enough to warrant concern
for our new 2024 burn areas associated with ongoing active wildfires.
As such, a Flash Flood Watch has been issued for the south WA
Cascades and Oregon Cascades from Lane County northward to cover
this threat as this will pose a safety concern for crews working on
these fires. While confidence is high somewhere in the Cascades will
be hit hard from thunderstorms, confidence is low in regards to the
exact location and exact timing. Nevertheless, confidence has
reached the 50% threshold needed to issue a Watch, and zones may be
added or removed from the Watch as confidence increases. For now,
anyone near or within the watch area should ensure they have a
timely way to receive NWS warnings in case a Flash Flood Warning is
issued.
While the bulk of convective activity should shift northward into
northwestern WA Saturday night, forecast soundings show lingering low
and mid level moisture / weak instability over northwest OR and
especially over southwest WA. This will likely result in at least
some continued showery activity, however convection will become more
shallow and chances for thunder will decrease to 15-20% or less.
Despite convection becoming more shallow Saturday night, brief heavy
downpours will still be possible. Showers and storms should finally
begin tapering off Sunday morning, which is discussed below in the
long term discussion. -TK
&&
.LONG TERM...Sunday through Wednesday...Rain will be starting to
taper off by Sunday morning as most of the energy associated
with the upper trough shifts north of the region, but certainly
could see a few stray showers linger into the day on Sunday and bring
minimal additional rainfall amounts to the area, especially over
southwest WA. Otherwise suspect the Pacific Northwest will remain
under the influence of broad upper level troughing centered offshore
through the middle of next week, which is well agreed upon by
ensemble guidance. As such, expect a continuation of seasonably cool
and cloudy weather through the end of the period with daily highs
remaining in the mid to upper 70s. The proximity to the upper level
trough will yield continued chances for sporadic shower
activity, but no significant rainfall or thunderstorm potential
is signaled beyond Sunday morning. /CB
&&
.AVIATION...Marine stratus has mostly cleared out of all areas,
with KONP being the last holdout. 40-50% chance of southern
coastal terminals remaining MVFR or lower throughout the day,
dropping back to IFR by 3z Fri. For other coastal terminals, MVFR
conditions redevelop around 3z Fri. Inland terminals should
generally remain VFR until 12-18z Fri, when the northern
Willamette Valley sees marine stratus pushing up the Columbia and
causing high-end MVFR cigs during that time period. 60% confidence
in MVFR cigs between 12-18z Fri. Winds at all terminals are
generally W/NW and under 8 kts throughout the entire period.
PDX AND APPROACHES...VFR expected until 12z Fri, with a 60% chance
of MVFR cigs between 12z-18z Fri due to marine stratus pushing up
the Columbia. Northwest winds under 8 kt throughout the period.
/JLiu
&&
.MARINE...Expect benign conditions over the waters through early
next week. Winds remain N/NW through Saturday before turning SW
as surface low pressure develops. Winds are expected to remain at
10 kts or less with gusts up to 15 kts; wind-driven seas of 2 of
4 feet. -Batz
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
$$
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Area Forecast Discussion
National Weather Service Pueblo CO
523 PM MDT Thu Aug 15 2024
.KEY MESSAGES...
- Low chance (less than 20 percent) for a storm this evening
I-25 corridor and southeast plains.
- Dry and hot both Friday and Saturday.
- Moisture returns Sunday, with above normal temperatures and
daily chances for showers and thunderstorms persisting
through next week.
&&
.SHORT TERM /THROUGH FRIDAY/...
Issued at 228 PM MDT Thu Aug 15 2024
Generally dry and warm across the area today, with little/no
convection even over the mountains, as wly flow has cut off
low/mid level moisture across much of srn CO. A few hints of
some deeper surface moisture/instability returning into nern NM
this afternoon, and some of this may leak northward over the
Raton Mesa into into the srn I-25 corridor and the plains this
evening and overnight. As a result, HRRR has some isolated
convection developing around Pueblo/Colorado Springs 02z-04z,
then sliding eastward onto the plains late evening and
overnight. Will keep some low pops in place to account for this
possibility, though storm strength/coverage may be limited by
relatively low (CAPE 300-600 J/KG) instability.
On Friday, upper ridge begins to build over Colorado, and with
rising heights and continued dry air mass, expect another day of
limited/no convection across much of the region. Some deeper
low level moisture may sneak back into the far eastern plains
late in the day as surface winds turn more n-ne, but any forcing
for precip looks weak and farther east, so will keep the dry
forecast in place at this point. Max temps will climb upward a
few degf given warming mid-levels, and a few spots over the
lower Arkansas Valley may get close to 100f by late afternoon.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 228 PM MDT Thu Aug 15 2024
Our Friday night through Saturday weather will be dominated by high
pressure sitting over New Mexico on Friday and meandering northwards
towards the Colorado and New Mexico border by Saturday. This system
will bring above normal temperatures and mostly dry conditions to
our plains, with only very isolated showers and thunderstorms over
the high country for Saturday. Overnight lows on Friday night look
to be near to just slightly above normal thanks to dry conditions
and efficient cooling, while daytime highs on Saturday look to rise
to around 5 to 10 degrees above normal. This means highs in the mid
90s to low 100s across the plains, mid 80s to low 90s for mountain
valleys, and 70s for higher terrain locations. Though relative
humidity values look to fall into the low teens through Saturday
afternoon, winds are expected to remain below critical fire weather
thresholds.
Sunday..
Sunday is a bit of a transition day, as models begin to bring a low
onshore over the Pacific Northwest, which will shunt the high off to
our southeast a bit as we get into the beginning of next week. This
will eventually open up the monsoonal moisture tap over our region.
For Sunday, models indicate that the beginning of this monsoonal
moisture should start to work its way into the high country, as we
remain situated along the northwestern periphery of the high. This
setup could lead to the possibility of a few showers and storms
pushing into the mountain adjacent plains through Sunday afternoon
and Sunday evening as well, though the best chances for moisture
will remain over the mountains for Sunday. Daytime highs look to
remain around 4 to 8 degrees above normal for Sunday, though we will
see a slight decrease from expected temperatures on Saturday,
especially over and near the mountains where convective cloud cover
will help to keep us cooler through the hottest part of the day. Our
far eastern plains could still see triple digits under mostly sunny
skies, but the majority of the I-25 corridor should top out in the
90s, with mountain valleys in the 80s and higher terrain locations
in the 70s.
Monday Onwards..
By Monday, models indicate that we transition to a pattern of
slightly above normal temperatures and daily chances for afternoon
showers and thunderstorms, especially over and near the higher
terrain, thanks to the return of monsoonal moisture over the region.
Ensembles, especially GEFS members, show a strong signal for PWAT
anomalies exceeding the 100-140% range beginning Sunday and
persisting all the way through next week.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 522 PM MDT Thu Aug 15 2024
VFR conditions are expected to prevail for all TAF sites (KALS,
KCOS, and KPUB) throughout the forecast period. Winds will be light
(mostly less than 10 kts) and diurnally influenced at all terminals.
There will be some gusty winds during the afternoon hours tomorrow
at KCOS and KPUB. -Stewey
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...PETERSEN
LONG TERM...EHR
AVIATION...STEWARD