Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/21/24
Area Forecast Discussion
National Weather Service Bismarck ND
1009 PM CDT Sat Jul 20 2024
.KEY MESSAGES...
- Isolated to scattered thunderstorms are expected on and off through
Monday. The threat for severe weather remains low.
- Smoke aloft from distant wildfires will be found through the
weekend (at least).
- High temperatures will mainly be in the 80s through Monday,
while some 90s will likely return mid to late week.
&&
.UPDATE...
Issued at 958 PM CDT Sat Jul 20 2024
Storms continue to push south along a line from eastern Sheridan
county, down to northeast of Pingree in Stutsman county. A few
of these cells have perked up to near severe limits with the
potential for hail up to the size of nickels and winds to
around 40 mph or so. It seems that these storms have moved into
a pocket of marginally better effective shear at around 25
knots. With capping starting to settle back in, minimal forcing,
and shear dropping off quickly, we expect there should be a
weakening trend here over the next hour or two. We did go ahead
and update precipitation chances through the night based on the
latest radar observations and guidance trends.
The other main change for this update was to add some patchy
fog to the forecast late tonight into early Sunday morning,
mainly along and north of the Missouri River. The HRRR and RAP
are more bullish than most of the other CAMs regarding fog
development but the environment will be similar to the last two
nights when we had some fairly widespread ground fog at times.
UPDATE
Issued at 625 PM CDT Sat Jul 20 2024
No major changes were needed for this update. Just blended in
the latest observations to the going forecast. Isolated
thunderstorms have developed as expected and should continue
until we lose daytime heating later this evening.
&&
.DISCUSSION...
Issued at 143 PM CDT Sat Jul 20 2024
Broad high pressure was in place over the Northern Plains this
afternoon, with a sharp upper ridge extending through the
Canadian Prairies to our northwest, leading to northerly flow
across the forecast area. A few showers and thunderstorms were
ongoing as of 19 UTC across the south central and southeast,
with plenty of instability available but very low shear, so the
expectation is for pulse type, airmass thunderstorms. CAMs have
been relatively inconsistent in timing and location of any
convection, but have been most consistent in the north central
this evening. Overall, we have broad-brushed low POPs across
most of the forecast area through tonight to account for this
potential, especially with limited forcing aloft to increase
chances in any one place. Flow aloft is very weak, so any storms
that develop will be very slow moving.
This northerly flow is also bringing in large amounts of smoke
aloft from wildfires in Alberta and British Columbia. We opted
to not include any near-surface smoke with this update, as
confidence is not quite high enough at the moment, but we cannot
rule out that some locations could experience minor visibility
reductions at some point. Otherwise, the latest HRRR smoke
forecast shows no reprieve from thick smoke aloft, so
continuing the message of hazy skies through the rest of the
weekend.
A similar day is expected on both Sunday and Monday, with highs
in the 80s, light winds, and chances (20-40%) for showers and
thunderstorms. Sunday`s precipitation might be a bit more
spatially limited, while on Monday, a back door cold front and
attendant upper wave (although relatively weak) will bring
higher chances for showers and thunderstorms during the day.
With continued weak shear, the potential for severe
thunderstorms is very low.
As the upper ridge begins to build and shift to east through the
week, temperatures will start climbing, especially across
western North Dakota. The ridge axis is progged to be overhead
of the Northern Plains Wednesday into Friday, with blended
guidance suggesting these will be the hottest days of the
extended period. Highs around 100 degrees F are within reason
mainly on Thursday, with low to medium probabilities of
exceeding this threshold across western North Dakota, especially
in areas along the Montana state border. Lower dew points are
co-located with these hotter temperatures which is keeping
current forecast apparent temperatures just below criteria, but
this will be something to watch in the coming days. Chances for
precipitation are low Tuesday through Thursday.
Upstream of the ridge, a deep upper low is forecast to move
onshore and into the Canadian Prairies late in the week, pushing
the ridge out of the area. More consistent POPs, although low,
begin showing up during this time, while machine learning
probabilities indicate low but increasing chances for severe
thunderstorms late in the week. NBM temperature percentiles
show that after Friday, temperatures will slowly decrease
through the weekend, although expect highs to stay in the mid
80s to mid 90s.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 625 PM CDT Sat Jul 20 2024
VFR conditions are generally expected through the period.
Isolated hit or miss thunderstorms will continue across western
and central North Dakota through the evening and then again on
Sunday afternoon. If a storm moves overhead, brief MVFR to IFR
visibility reductions will be possible. The isolated nature of
convection precludes mention for any specific site forecast but
any storm that moves overhead could produce brief heavy
downpours and small hail. Winds may also become gusty and
erratic in the vicinity of any thunderstorms.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...ZH
DISCUSSION...Jones
AVIATION...ZH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
639 PM MDT Sat Jul 20 2024
.KEY MESSAGES...
- Isolated to scattered afternoon showers and storms this
afternoon. An additional round of storms possible overnight
tonight.
- Cooler on Sunday, with continued rain chances.
- Gradual warming trend next week with drier conditions.
&&
.UPDATE...
Issued at 618 PM MDT Sat Jul 20 2024
An outflow boundary has developed in northeast Colorado this
evening and it is moving southwestward. As of this writing
(6:20pm), the outflow boundary is moving through Fort Collins and
Hudson and will move through the center of Denver shortly after
7pm. This outflow boundary has continued to create strong to near-
severe storms immediately behind it. This should continue as there
is ample moisture behind this front along with good forcing from
the boundary. There is also a shortwave trough aloft that will
help with upper level forcing. All of these factors are combining
to make the chance of storms across the urban corridor around
60-70 percent this evening. Therefore, PoPs were increased and the
forecast mentions likely storms now.
The latest runs of the HRRR have been showing severe storms
forming in the Denver metro. The threat for severe storms will
have to be monitored closely as there seems to be a couple times
every summer where the severe threat is appears limited only to
have significant hail occur in the evening hours. Mixed-layer
CAPE behind the outflow boundary is above 1,000 j/kg which would
support a severe threat. Deep layer shear is not particularly
strong but with northeast winds gusting to 40 mph behind the
boundary, the deep layer shear will increase and could support a
few severe storms. Overall, the parameter space seems that it
will support a few severe storms but not widespread severe storms.
Another threat that will need to be watched is the threat for
flash flooding. The Cameron Peak burn area could have a threat of
flooding and a couple locations in the urban corridor may see
enough rainfall to have minor flooding.
&&
.SHORT TERM /Through Sunday/...
Issued at 220 PM MDT Sat Jul 20 2024
Satellite and radar this afternoon show a few weak storms across
the forecast area, mainly over the northeastern plains. No
significant updates to the forecast through this evening with
additional storms likely developing across the Front Range
mountains/foothills over the next few hours.
As we get into tonight and tomorrow`s forecast, confidence
decreases pretty quickly. Guidance has slowly warmed up to the
idea of a cluster of showers and embedded thunderstorms late this
evening/early tonight. This appears to be linked to the convection
currently developing across central Wyoming. We maintained at
least chance PoPs through the overnight. If you`re a fan of rain
across the I-25 corridor, it will be worth watching short term
model trends to see if models come into better agreement.
From there, there`s a few more "ifs" to discuss. If we do get
overnight rain... that may lead to some Sunday morning stratus. If
we get morning stratus... that likely limits our daytime heating
and subsequent afternoon destabilization... leading to less
coverage of showers/storms during the day Sunday. On the other
hand, a sunny start to Sunday would favor better instability and
widespread showers and storms by late morning or early afternoon.
As a whole, confidence of rain at any given hour is pretty low...
but the pattern favors a good chance (>70% from the GEFS/ECME) of
a wetting rainfall (>0.10") across the Front Range and adjacent
plains by Sunday evening. Stay tuned!
&&
.LONG TERM /Sunday night through Saturday/...
Issued at 240 PM MDT Sat Jul 20 2024
The CWA looks to stay in relatively weak northerly flow aloft
with high amplitude upper ridging to our west and northwest and
upper troughing east of Colorado Sunday night through Tuesday
night. The synoptic scale energy is expected to be weak
downward motion to neutral through the five periods. The boundary
level wind and surface pressure fields keep fairly normal diurnal
surface wind patterns for the CWA.
The precipitable water and boundary layer dew point fields show
drying on Monday from Sunday; then more drying on Tuesday. CAPE
is limited through the periods. As far as convective chances go,
forecast soundings and QPF fields show the the best chances of
measurable rainfall over the high country for late day Monday and
only "isolated" coverage for the plains. Chances decrease further
on Tuesday with less moisture availability and less instability.
Heavy rain chances are marginal at best on Monday, decreasing
further on Tuesday.
For temperatures, Monday`s highs warm up a bit from Sunday`s
readings but they still look to be below seasonal normals across
the forecast area. On Tuesday, readings climb a bit higher but
temperatures still look a tad below seasonal normals.
For the later days, Wednesday through Saturday, the upper ridge to
our west pushes eastward into and across Colorado through Friday
night. By Saturday, some weak troughing gets into Colorado. Drying,
subsidence and warming will be the rule into Friday. Rainfall
chances get better again on Saturday along with some minor cooling.
&&
.AVIATION /00Z TAFS through 00Z Monday/...
Issued at 536 PM MDT Sat Jul 20 2024
A line of strong to severe storms is progressing through Morgan
County as of this writing. These storms have formed along an
outflow boundary that will move southwestward toward the terminals
this evening. Confidence is growing greatly that this outflow
boundary will produce storms with gusty winds. Winds up to 40
knots are possible. The best chance for these storms to occur is
between 02-05Z. Therefore, a TEMPO group was added to all
terminals.
The storms will end this evening and light winds are expected
throughout the night. There is a chance that stratus clouds
develop in the morning around 3,000 feet. However, this chance is
low enough that it wasn`t included in the TAFs at this time.
Tomorrow afternoon, isolated showers and storms will form. These
storms could produce gusty winds and reduce visibility. The chance
for these storms to impact the terminals is around 30 percent so a
PROB 30 was included.
We also want to note that there is plenty of smoke in the visible
satellite imagery that is headed to Colorado. It may impact
visibility especially in the higher levels of the troposphere.
&&
.HYDROLOGY...
Issued at 220 PM MDT Sat Jul 20 2024
Despite relatively high chances for precipitation, the burn area
flash flooding threat remains limited. Thunderstorms this
afternoon will be widely scattered and may pose a brief heavy
rain threat, but storm motions near 15-20kt will push storms off
the burn areas quickly. Additional showers and storms are
possible tonight but most guidance keeps these over the plains.
Cooler temperatures tomorrow will likely limit instability and
keep storms weak enough to avoid widespread issues. Storm motions
should generally be slower tomorrow and if a strong storm or two
manages to develop it could produce enough rainfall for isolated
issues.
A warming and drying trend is expected next week, with no
significant hydrological concerns.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Danielson
SHORT TERM...Hiris
LONG TERM....RJK
AVIATION...Danielson
HYDROLOGY....Hiris
Area Forecast Discussion
National Weather Service Billings MT
819 PM MDT Sat Jul 20 2024
.UPDATE...
Afternoon convection has dissipated quickly this evening, and as
of 8pm is really confined to areas near the Pryor and Bighorn
Mountains. This is consistent w/ the latest mesoanalysis showing
PV max moving from south central MT to northern WY. There are a
few showers north of our cwa, but they are also tapering off and
feel that as we transition to subsidence and darkness we should be
dry from ~10pm thru the remainder of the night. Regarding smoke,
there is plenty of it lofted and that will remain the case for the
foreseeable future. Surface visibilities remain 10SM or greater
regionwide. The northerly flow will continue advect Canadian smoke
southward (there are several active fires in northern AB and BC),
and we could begin to see surface smoke become more of an issue
tomorrow. This is what the HRRR is suggesting and will need to
monitor. JKL
&&
.DISCUSSION...
Rest of Today through Sunday Night...
Isolated to scattered showers and thunderstorms will progress
south/southeast through the afternoon and evening today. With
minimal shear and only modest instability in place, any storm
that initiates looks to remain garden variety, short lived, and
relatively slow in motion. With that said, the main threats are
heavy rain and wind gusts up to 40 mph. Small hail is also
possible under the strongest storms. Activity will decrease late
this evening through Sunday morning before isolated showers and
thunderstorms are expected to form again Sunday afternoon and
evening, mainly over the mountains and east of Billings. Again,
minimal shear and instability will keep things weaker, with gusty
winds up to 40 mph and heavy rain being the main threats.
Outside of this activity, smoke concentrations look to increase
aloft over the next 24 hours. Eastern Montana will see the push
by this evening, with the rest of the area getting into it by
Sunday afternoon. While the majority of the smoke looks to remain
aloft, some is expected to mix down to the surface. If you have
special sensitivities to smoke, make sure to check your local air
quality before headings outside tomorrow.
High temperatures Sunday are in the upper 80s to lower 90s across
the area. Expect overnight lows to be in the 50s and 60s tonight
and Sunday night. Arends
Monday through Friday...
Ensembles remain in good agreement with the overall pattern
through the middle of the week, with a bit more uncertainty from
Friday and beyond.
Upper ridge axis centered over western Montana will slowly shift
east through Wednesday, settling over eastern Montana. Gradually
warming temperatures can be expected, with highs in the upper 80s
to lower 90s Monday, increasing into the 90s for Tuesday, and
middle 90s to lower 100s for Wednesday. NBM probabilities for
temperatures of 100 degrees or higher are 50% or greater for the
river valleys mainly from Billings east. Isolated to scattered
showers and thunderstorms (15-30% chance) are possible over the
mountains during the afternoons and evenings, with less coverage
out onto the lower elevations.
Thursday will be another hot day ahead of a ridge breakdown with
high temperatures mainly in the upper 90s to lower 100s. A
limiting factor on the temperatures could be smoke aloft. A cold
front is currently progged to enter the west during the late
afternoon, moving east through Thursday evening. Isolated to
scattered showers and thunderstorms (20-50% chance, greatest over
the southwest mountains) are possible with the cold front. Will
need to keep an eye on Thursday, as this is a pattern that brings
fire weather concerns. Cooler conditions and additional chances
for showers and thunderstorms (20-50%, greatest over the west) are
progged for Friday as a weak shortwave lifts through the region.
Highs in the upper 80s to 90s are currently forecast. STP
&&
.AVIATION...
Isolated showers and thunderstorms, mainly south of KBIL at 02Z,
will dissipate entirely by 04Z this evening. Isolated
thunderstorms are expected Sunday afternoon as well, mainly east
and south of KBIL. VFR will prevail over the next 24 hours.
Lofted smoke will continue reduce slant range visibility across
the region. Surface impacts from smoke are less certain, but
surface visibilities may decrease some by Sunday.
JKL
&&
.PRELIMINARY POINT TEMP/POPS...
Sun Mon Tue Wed Thu Fri Sat
-----------------------------------------------------------
BIL 062/092 063/093 063/097 066/103 068/103 067/094 062/089
11/H 00/U 00/U 00/G 02/T 22/T 22/W
LVM 054/090 053/092 055/097 058/100 061/098 057/091 054/087
01/H 00/U 01/U 11/U 13/T 34/T 33/T
HDN 058/093 060/094 060/098 062/105 065/104 064/096 059/090
22/T 00/U 00/U 00/G 01/G 22/T 32/W
MLS 063/091 063/091 065/095 066/102 069/103 070/094 065/089
22/T 01/U 00/U 00/G 00/G 21/B 31/B
4BQ 061/090 061/090 062/094 065/101 067/104 070/096 065/090
12/T 01/U 00/U 00/G 00/G 10/B 21/B
BHK 059/089 059/089 060/093 063/098 064/101 066/096 063/092
12/T 01/U 00/U 00/U 00/G 11/B 22/T
SHR 055/090 055/090 056/094 058/100 061/102 062/094 058/089
22/T 01/U 00/U 00/U 01/G 22/T 23/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Des Moines IA
621 PM CDT Sat Jul 20 2024
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
- Periodic rounds of scattered showers and storms into early
next week. Severe weather not expected.
- Drier with gradually warming temperatures toward the latter
half of next week.
&&
.DISCUSSION...
Issued at 200 PM CDT Sat Jul 20 2024
It`s been a soggy and cloudy day for much of the forecast area as we
feel the impacts from a low amplitude shortwave circulation embedded
within mean northerly synoptic flow aloft. The shower activity has
been highly disorganized, owing to only marginal background
kinematic forcing and very nondescript surface
flow/convergence. A few rumbles of thunder have been noted in
northwest Iowa. The RAP has consistently highlighted this area
and into north central Iowa for potential funnel clouds later
this afternoon and evening as the NST parameter peaks where
ambient vorticity from the parent upper low overlaps with near
surface instability/stretching, coincident with clearing and
spotty cellular convection on satellite imagery. The cloud cover
and shower activity has held temps back today with some locals
struggling to get out of the 60s.
Models develop fog late tonight into early Sunday with the moist
and light flow surface conditions. Dense fog is currently not
forecast, but less cloud cover may favor lower visibilities. The
fog dissipates by mid to late morning, then the rest of the day
will be a similar scenario to today with below normal temps
mainly in the 70s and rain chances as the shortwave is sluggish
to progress southward into the base of the mean upper trough.
Hires model suite is a little less bullish on spatial coverage
and tied more to diurnal trends with most showers developing
during the afternoon, and potentially with more embedded thunder
activity as breaks in cloud cover promote deeper instability.
Weak shear profiles will limit any severe threat, but conditions
will again be favorable for a few funnel clouds.
Periodic rain chances hang around through Tuesday as additional
waves pass through the weak northerly flow aloft. Timing and spatial
coverage is difficult to pin down due to the diffuse forcing
mechanisms and no obvious focus for convergence. A more robust
wave will push a frontal boundary through Tuesday night into
Wednesday, sweeping out most appreciable moisture as a dry
Canadian airmass surges south into the region. This should lead
to dry conditions as we move into the latter half of the week
along with steadily warming temperatures as the western conus
ridge migrates east.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 617 PM CDT Sat Jul 20 2024
Mostly VFR this evening though a few showers are lingering over
the region. Areas of fog are expected to develop later tonight.
There still remains uncertainty to what extent the fog
development will be. Have maintained mention at all sites. The
fog will diminish in the morning. Cumulus should develop again
by mid to late morning and there could be some local BKN MVFR
early before cigs rise with diurnal heating. A few showers are
possible again by the afternoon by with less coverage than
today.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Martin
AVIATION...Donavon
Area Forecast Discussion
National Weather Service Goodland KS
1004 PM MDT Sat Jul 20 2024
.KEY MESSAGES...
- Scattered showers and thunderstorms through the weekend and
into early next week. Another low strong to severe threat is
possible across western portions of the Colorado counties
Sunday afternoon and into the early evening.
- Smoke aloft from Canadian wildfires looks to move across the
area Sunday.
- Warmer and drier conditions forecast for the mid to latter
part of next week.
&&
.UPDATE...
Issued at 824 PM MDT Sat Jul 20 2024
Patchy fog may develop across the area tonight with light winds
and low dew point depressions in place. The area that is more
favorable for fog development will be across Red Willow, Norton,
Decatur, and Graham counties around sunrise as winds more NNE
and light which is the climatologically favored for fog
development.
Did increase pops across western portions of the area some for
the early morning hours as the RAP and NAM both show 850 FGEN
in place along with some weak isentropic ascent occurring that
may result in some showers/storms wandering across the CO/KS
line. Those west of Highway 385 should see the relative higher
potential for additional rainfall.
Also did add in haze from Canadian wildfires to most of the
area during the day and early evening Sunday. Very good
consensus between the 12Z, 18Z and now 00Z runs of the HRRR
Vertically Integrated Smoke product all support the northerly
flow transporting the haze into the area.
Will again be watching for the potential for strong to
marginally severe storms. ML and MUCAPE looks to be similar to
today but shear looks to be very low around 10-15 knots. However
lapse rates are forecast to be better than today with around 7C
vs the 6-6.5C for today. So with that thinking that perhaps
accumulating hail may be of concern especially with a moist
almost complete saturated level from around 700-500mb.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 230 PM MDT Sat Jul 20 2024
Across the region this afternoon, skies are mixed from partly to
mostly sunny. Most of the cloud cover west of Highway 27 is from
persistent scattered rw/trw through the day. Temperatures as of 200
PM MDT are ranging from the upper 70s into the mid 80s, along with a
persistent north-northeasterly flow w/ gusts up to 20 mph at times.
Main wx concerns for the short term period will focus on strong to
severe thunderstorm chances for portions of the CWA. Sunday and
Monday will also have scattered storm chances.
Looking at the latest 500mb RAP40 analysis, the amplified ridge over
the western portion of the country remains in place and is expected
to persist into the beginning of next week. As with the last several
days, there is a shortwave working south along the eastern side of
this ridge, helping to trigger the scattered convection w/ the aid
of a weak surface trough over southwest Nebraska.
The current CAMs(HRRR/NamNest) are in fair agreement as to the start
time of current radar coverage and pushing southward through about
02z Sunday. With northerly flow aloft, most of the expected precip
will occur in the west with some scattered precip east of Highway 27
through this evening. SPC has continued a Marginal risk for
wind/hail threats. Limited instability should keep storms below
criteria from yesterday, as well as areal coverage. Overall a 15-30%
chance for rw/trw tonight.
For Sunday onward, some change in the upper level pattern as the
ridge will begin to shift east. This will allow for another chance
15-40% for storms. The focus Sunday will be in the west as a lee-
side trough pushes west slightly w/ high pressure building in from
the E/NE. Sunday night into Monday, that surface ridge breaks down
and in tandem with another shortwave, will allow for a 15-20% chance
for rw/trw. Dry conditions expected for Tuesday as high pressure
builds over the area.
For temps, decreasing chances for precipitation as the short term
period progresses will afford the Tri State area a warming trend
into Tuesday of next week. On Sunday, highs will range from the
upper 70s into the mid 80s. Coolest areas along/west of Highway 27
where most of the precipitation is expected. Going into Monday,
upper 70s to lower 80s in Colorado w/ mid 80s east of there. For
Tuesday, mid 80s to around 90F are expected. Lows each night will
range from the mid 50s west to around 60F east, especially east of
Highway 25.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Issued at 153 PM MDT Sat Jul 20 2024
From the latest runs of the GFS/ECMWF, the amplified upper ridge
over the western portion of the country will continue a slow trend
eastward into the Plains region as next week progresses. Guidance
does begin to differ as to the strength of the ridge by the end of
next week as a 500mb trough digs into the Pacific NW. If this occurs
late Friday, there could be a shortwave ahead of this does
develop/push through the Rockies and into the CWA by next weekend.
For now, mainly dry and above normal conditions will ensue.
At the surface, persistent southerly flow from lee-side troughing to
the west will aid in warming the region up as the upper ridge crests
overhead next week. Gradient does tighten ahead of the potential
shortwave late Friday, which will allow some decent gust potential
up to 30-35 mph possible.
For temps, highs for the midweek period will range from the upper
80s into the lower 90s. Next Thursday onward, lower to mid 90s are
expected. Overnight lows will see an increasing trend with Tuesday
and Wednesday nights having a range from the upper 50s into the
lower 60s. Thursday night onward, 60s area wide w/ warmest locales
east of Highway 25 each night.
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1000 PM MDT Sat Jul 20 2024
Confidence is increasing in fog potential across the area
tonight. A similar setup along with similar guidance signals
resulted in KMCK falling to 2.5 SM in fog so am going with
similar expectations for this event. Low dew point depressions
across the west and a saturated boundary layer makes me think
that some fog potential does reside at KGLD as well; even KMCK
may have the better potential. Any fog should burn off by 15Z at
the latest. Haze from wildfire smoke looks to be across the area
during the day Sunday as well so will include broken upper level
clouds. There is a potential some smoke smell and visibility
reductions to around 6sm at each terminal may occur throughout
the day.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...None.
CO...None.
NE...None.
&&
$$
UPDATE...Trigg
SHORT TERM...JN
LONG TERM...JN
AVIATION...Trigg
Area Forecast Discussion
National Weather Service Louisville KY
844 PM EDT Sat Jul 20 2024
.KEY MESSAGES...
* Shower and storm chances will continue to increase across
southern KY for Sunday, then everywhere else by next week.
* Locally heavy rainfall possible with any of these showers and
storms.
&&
.UPDATE...
Issued at 844 PM EDT Sat Jul 20 2024
Brief, isolated showers continue over southern Kentucky this
evening. As the sun begins to set, these showers will start to
dissipate. In the overnight hours, cloud coverage will increase over
the region and winds will be calm to light out of the northeast.
Some patchy fog development over southern Kentucky is possible,
mostly due to recent rainfall. The current forecast remains on
track with low temperatures Sunday morning in the mid-upper 60s.
&&
.SHORT TERM /THROUGH SUNDAY/...
Issued at 319 PM EDT Sat Jul 20 2024
Sfc boundary has lifted northward as a warm front across southern KY
and northern TN. This is evident on the Kentucky Mesonet where you
can see a spread of dew points in the upper 60s to around 70 along
the KY/TN border with low/mid 60s further north along the Ohio River
into the Blue Grass. There is even a steep PWAT gradient from north
to south with 1.5"-1.7" along and just north of the KY/TN border and
south of the parkways with 1.1-1.4" from southern IN to just north
of the parkways. Current radar images from area WSR-88d show a few
isolated showers/storms forming along the KY/TN border, just south
of the warm front. This remains the best chance for precipitation
this afternoon before activity diminishes with the loss of daytime
heating. While the current HRRR wants to develop some isolated
activity northward later this evening into the overnight, I just
don`t feel there will be enough instability or lift to develop this
activity, so continued to trend of diminishing precipitation chances
this evening and overnight. Sfc low currently located over the Deep
South will work along the quasi-stationary boundary turned warm
front that stretches from Louisiana through the TN Valley and
eastward towards the Eastern Shores of VA. This will help to
increase mid/upper cloud cover over the region overnight. Even with
the cloud cover, the increased low-level moisture may increase the
possibility of patchy fog across our south in areas near and south
of the sfc boundary.
As the aforementioned sfc low slowly works into Kentucky during the
day tomorrow, it will continue to lift the sfc boundary further
north towards the Ohio River and into the Blue Grass by tomorrow
afternoon. An upper low coming dropping southward out of the Upper
Midwest will open up into a trough and start to swing through the
region as well during the day. This will help to increase the low
level moisture northward as dew points climb into the mid/upper 60s
across north central KY and southern IN while we will have low 70
dew points across southern KY. More scattered showers and
thunderstorms will be likely tomorrow afternoon. HREF ensemble mean
continues to show 1000-2000 J/kg of SBCAPE across a large portion of
central KY tomorrow afternoon but with meager shear and lacking any
strong lifting mechanism, while there remains a chance for
showers/storms tomorrow afternoon the main impacts will be heavy
rain and occasional gusty winds from any activity that forms.
Temperatures could be quite warm tomorrow working into the mid/upper
80s. Temperatures could end up being a challenge depending on shower
activity as well as cloud cover from the aforementioned systems
working across the region tomorrow.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 319 PM EDT Sat Jul 20 2024
Relatively stationary frontal boundary draped over Kentucky during
the next week will bring showers and thunderstorm chances every day
with the highest confidence being Monday and Tuesday. Confidence is
increasing (as the forecast pattern has been consistent for several
days) that several rounds of storms will bring locally heavy
rainfall. Model forecast soundings continue to show a low severe
threat with the main concern focusing on the heavy rain potential
with plenty of column moisture and elevated PW amounts. Gusty winds
and small hail would be secondary threats with the strongest storms.
Locally excessive rain could result in flooding, especially in the
areas with best coverage across the southern and eastern portions of
the forecast area. Concerning max temperatures, the work week will
be slightly below normal with highs ranging in the low and mid 80s.
Temperatures will be highly dependent on storm/cloud activity each
day. Heading to the end of the week and into the weekend, max temps
will climb to around normal in the mid to upper 80s.
&&
.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 737 PM EDT Sat Jul 20 2024
VFR conditions will remain for this TAF cycle. In the overnight
hours, light northeasterly winds will prevail with SCT-BKN mid and
high level clouds. These clouds, along with limit precipitation will
keep fog development to a minimum in the early morning hours. There
is a small chance for fog at BWG and RGA, however, confidence is
quite low. On Sunday, low and mid level clouds will begin to build
into the region from the northwest. Winds will remain light out of
the northeast. In the late afternoon, showers and storms will be
possible.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...SRM
SHORT TERM...BTN
LONG TERM...MCK
AVIATION...SRM
Area Forecast Discussion
National Weather Service Lubbock TX
933 PM CDT Sat Jul 20 2024
...New AVIATION...
.SHORT TERM...
(This evening through Sunday)
Issued at 153 PM CDT Sat Jul 20 2024
Regional surface obs at 1 PM captured a surface trough drifting
south from CVS to PVW to CDS underneath generally weak N-NW flow.
Westerly winds of this trough were proving quite dry with dewpoints
mixing out into the low/mid 50s over much of the Caprock which has
dealt a hefty blow to CAPEs. This was not the case off the Caprock
where winds were more backed south of a mesolow poised near Caprock
Canyons. Aloft, satellite imagery shows what appears to be a weak
MCV over the northern Rolling Plains that has already triggered a
small cluster of storms. PoPs were updated earlier this afternoon to
reduce mention to isolated on the Caprock while focusing a scattered
coverage of storms farther east within richer moisture and an
instability axis. Immediately north of the surface trough on the
Caprock, CAPEs do improve owing to Td`s in the lower 60s which
should fuel some storms through the evening. A few pulse storms
remain in the cards until sunset given healthy DCAPE and weak deep
layer shear.
For this evening and overnight, the NBM looks too generous with PoPs
in most areas given an overall downturn in activity as shown by
multiple runs of the HRRR and recent HREF mean, so we`ll advertise
low PoPs with increasing chances later in the night near the TX/NM
border for what should be a cluster of storms spreading south across
eastern NM, and also in the far sern TX PH along the fringes of
increasingly cyclonic NW flow far from an upper low over the
Upper Midwest.
Sunday features weak height falls as an upper high currently over AZ
retreats to NV. More importantly, moist E-NE upslope winds along
with breaks in cloud cover should fuel a better round of afternoon
storms expanding from eastern NM and through the South Plains. High
temps continue to creep up a bit from earlier forecasts, although
still not to the extent of the GFS which is considerably lower with
PoPs.
&&
.LONG TERM...
(Sunday night through next Friday)
Issued at 153 PM CDT Sat Jul 20 2024
Upper level troughing to our northeast will continue tracking
through the Upper Midwest into portions of the Great Lakes region
through the period. Meanwhile to our west, upper level ridging will
continue to dominate across the southwestern CONUS. This upper level
pattern will favor relatively northwest flow aloft to prevail
through a majority of the long-term period, thus increasing
precipitation potential through the upcoming week.
Best chances for thunderstorms arrive overnight Sunday into early
Monday morning as a shortwave trough tracks along the eastern side
of the upper level ridge. Northwest steering flow will help this
complex of thunderstorms track southeastward into the far
southwestern Texas Panhandle by late Sunday night. Storms are
expected to linger through the overnight hours as they continue to
track southeast through the FA, likely diminishing just before or
around sunrise Monday. Convective potential becomes slightly
tricky by the afternoon, especially with an overworked environment
in place. If low-level stratus decides to linger through the
afternoon, like some models have projected, we may not see enough
boundary layer mixing, limiting diurnal destabilization. In
addition, any remaining outflow boundaries from the overnight
storms could possibly throw a wrench in convective development.
Due to the uncertainties and models hinting at a drier solution
unfolding, decided to limit NBM likely PoPs down to slight chance
and chance PoPs for Monday afternoon. A few subtle disturbances
within the flow aloft, upslope flow, and increased moisture in
place will likely allow for additional daily chances for
thunderstorms through the rest of the long-term period.
As previously stated, forecast highs on Monday will likely remain
below seasonal normals in the upper 70s to mid 80s. Temperatures
will sadly begin to warm as we head through the week, but thankfully
remain near seasonal normals in the upper 80s to mid 90s as
thickness values and heights begin to slowly increase.
&&
.AVIATION...
(00Z TAFS)
Issued at 932 PM CDT Sat Jul 20 2024
Thunderstorms are briefly possible at KLBB this evening. Otherwise
VFR and generally light winds will persist through the TAF period.
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...93
LONG TERM....12
AVIATION...19
Area Forecast Discussion
National Weather Service Medford OR
246 PM PDT Sat Jul 20 2024
.DISCUSSION...Most of the coastal stratus has dissipated, and we
remain under mostly stable southwest flow under a ridge of high
pressure and a thermal trough over central California. There are,
however, some cumulus clouds are starting to build east of the
Cascades. These clouds are indicative of a shortwave disturbance
which will is approaching our area from the southwest this
afternoon and evening. Lastly, smoke from area wildfires is
blanketing much of the area. In fact, the Medford airport is
reporting reductions in visibility to around 4 miles.
While temperatures will be hot today, the smoke may prevent the
absolute peak of heating this afternoon. That being said, that`s
not much of a consolation. Temperatures are forecast to be in the
upper 90s to 105 degrees for many inland areas today. Tonight will
be somewhat cooler, as will tomorrow, but highs east of the
Cascades will be in the upper 90s to near 100 degrees. A heat
advisory continues for areas of the Shasta Valley and eastward in
California and east of the Cascades in Oregon. This heat advisory
was extended until 11 pm Sunday due to smoke concerns keeping the
HeatRisk at moderate with some majors sprinkled within once again.
The bigger concern, is going to be this shortwave disturbance
passing through southern Oregon this evening. This will provide
some instability (smoke permitting), additional moisture, and a
lifting mechanism to provide isolated to scattered showers and
storms this evening, through the overnight hours, and again
on Sunday.
This event looks very similar to the one from earlier this week,
both in overall pattern and in the dry lower layers of the
atmosphere. There are differences, however, in that this shortwave
trough is coming through overnight and will pass by farther
offshore compared to earlier in the week. We remain concerned
about lighting and gusty outflow winds once again, especially
given that any storms that develop will produce very little, if
any, precipitation. However, given the farther offshore
trajectory, this should limit how strong winds get this afternoon
in advance of the shortwave. Also, we don`t expect sufficient
moisture for thunderstorm development to arrive until late this
afternoon and evening. So for today, thunderstorm chances are
focused over western Siskiyou County and over the East Side, then
transitioning to areas west of the Cascades this evening and then
to areas north of the Rogue-Umpqua Divide, including the coast
north of Cape Blanco, late tonight into Sunday morning. There will
be a relative break in thunderstorm activity during the late
morning hours, then the focus of convection concerns will shift to
the East Side on Sunday as the wave exits the region.
For the remainder of the week, the pattern will very slowly progress
to the east, with the Gulf of Alaska trough gradually moving inland
into Canada and Washington. This will push the ridge axis farther
east and, as a result, we are expecting temperatures to "cool"
slightly, returning to near normal values for this time of year.
We`ll need to monitor the potential for gusty winds as this trough
pushes inland, otherwise, relatively dry west to southwest stable
flow should continue through the week. Though conditions should
remain dry, there are some indications that some unstable monsoonal
air could skate by our far southeastern areas (eastern Modoc/Lake
counties) so we`ll need to monitor these trends as well.
-Schaaf/BR-Y
&&
.AVIATION...20/18Z TAFS...Marine stratus (ranging from LIFR near
Brookings to MVFR at North Bend) will impact portions of the coast
and even some coastal valleys into this afternoon. VFR will prevail
from Port Orford south to Gold Beach. Model guidance is showing a
deeper marine layer at North Bend that could limit clearing (or
breaks in the stratus) to just a few hours this afternoon. Stratus
will quickly return at North Bend this evening. Then, during the
evening, low pressure offshore will approach. There is some
potential for the coastal stratus to lift a bit, but IFR/LIFR could
remain in place as isolated thunderstorms develop over the top.
Inland, VFR conditions will prevail through Sunday morning, with an
exception. The exception will be in the vicinity of the cluster of
fires in eastern Douglas County, and across northern portions of
Klamath and Lake counties, where visibility could occasionally lower
to 3-5 miles in smoke/haze. Hazy skies are likely across more of the
area than recent days as well, including here in portions of Jackson
County and near Klamath Falls. Visibility could be briefly MVFR.
Isolated to scattered thunderstorms will develop across Modoc and
southern Klamath/southern Lake counties late this afternoon/early
this evening, but this activity should wane by midnight as the
action shifts to the west side/coast. Activity over the west
side/coast Sunday morning should lift to the north. However, we
expect another outbreak of scattered thunderstorms east of the
Cascades Sunday afternoon/evening. -Spilde
&&
.MARINE...Updated 215 PM Saturday, July 20, 2024...A thermal
trough will strengthen tonight through Tuesday. Moderate north winds
and steep seas will be present south of Port Orford tonight into
Sunday. Expect conditions hazardous to small craft to expand to all
areas during Sunday with the strongest winds and highest seas south
of Pistol River. Stronger, gale force winds and very steep,
hazardous seas are expected to develop Sunday night into Monday, and
then continue into Tuesday. -Spilde
&&
.FIRE WEATHER...Issued 200 PM Saturday July 20, 2024...
Thunderstorms will be the main concern from late this afternoon
through early Sunday evening. The latest water vapor image is
showing the upper trough working it`s way north along the California
coast. This is already in the beginning stages of tapping into some
monsoonal moisture as evidenced by increasing cumulus development in
Fire zone 285, portions of the east side and areas south of there.
The upper trough will move up from the south just off the California
coast and will tap into some monsoonal moisture with a southeast
flow aloft. At the same time, there`s good agreement, the upper
trough will become negatively tilted this afternoon into tonight.
Based in part on pattern recognition, and various other data, all of
the ingredients are there for storms to break out late this
afternoon in portions of northern California, east of the Cascades,
with a few storms possibly slipping into into the southern portions
of Fire zones 619, 620, 621, and 622 early this evening due to a
stronger flow aloft which could allow storms to come off the
mountains and move north into the lower elevations.
The axis of the upper trough will still be south of our area tonight
which heightens the concern for nocturnal storms west of the
Cascades, and portions of the eastside in Oregon This is a classic
pattern where the instability is elevated, and thus the convection
will be elevated as well. All signs are pointing towards a heighten
concern for nocturnal storms along and west of the Cascades Saturday
night into Sunday morning. Thus, the Fire Weather Watch has been
upgraded to a Red Flag warning for the Cascades west, for abundant
lightning on dry fuels. Keep in mind given how dry and hot it has
been for the interior and near the coast, that lightning efficiency
is high to very high for fire starts. Also gusty and erratic winds
are a concern which could further increase fire activity on existing
fires. Some of the high res guidance are showing some reflectivity,
and higher PWATS, therefore there we could see some rain out of
these storms that could reach the ground, but it will not provide
much, if any help in preventing new starts given how dry and hot
it`s been. Additionally model soundings suggest the base of the
storms could be high with a drier sub layer which is another factor
that could limit the amount of precipitation.
Even through the center of the action could end up along and west of
the Cascades, Fire zone 625 could also experience nocturnal storms
this evening and tonight, followed by additional storms Sunday
afternoon and evening. A red Flag is out for this zone and it will
be a situation where most of the action in terms of storms will be
tonight, then again Sunday afternoon into Sunday evening. Hence the
long duration time of the Red Flag.
The upper trough axis shifts north during the day Sunday. Any threat
for storms could be confined to the early morning hours over the
northwest part of our area, then shifting north late Sunday morning
through Sunday afternoon with a drier and stable southwest flow
moving into the area. However, there will be enough instability,
moisture and trigger for isolated to scattered storms to develop in
Fire Zones 624 and 625 Sunday afternoon and lasting into Sunday
evening. There`s pretty good agreement most of the action Sunday
afternoon into Sunday evening will be in these areas and the Fire
Weather Watch has been upgraded to a Red Flag Warning to account for
this.
Storms are expected to be isolated portions of Fire zone 623, and
along the Warners in Fire Zone 285 Sunday afternoon and evening, so
these were left out of the warning, but lightning efficiency remains
high, so any lightning is likely to result in new starts.
Monday, a dry and stable southwest flow will set up with any chance
for storms shifting east and northeast of our area. It will be
cooler with gusty afternoon and early evening breezes for the
interior westside valleys and east of the Cascades.
The rest of next week is pointing towards dry weather, with ridging
nudging back into the area. This will result in afternoon
temperatures trending upwards from Tuesday and beyond. The concern
will shift towards moderate to locally poor overnight recoveries for
the mid slopes and ridges in southwest Oregon and western Fire zone
280, and the typical gusty afternoon and early evening breezes for
the interior westside valleys and east of the Cascades with low
afternoon RH`s. However, some of the models hint at some mid level
moisture and instability creeping into northern Cal and southeast
portions of Fire Zones 624 and 625 Tuesday afternoon and evening.
For now we have a low end probability of thunderstorms (10% or
less), and we`ll continue to watch this closely.
A side note for those involved in air attack on the various fires in
our area will be visibilities lowering to 3-4sm in the vicinity of
the Homestead Complex. However, due in part to an east drainage from
last night and this morning, and some vertical mixing has allowed
smoke from that complex is moving down into the Rogue Valley
resulting in MVFR visibility between 4-5 sm at Medford Airport. The
latest run of the HRRR smoke fields show the smoke being transported
east to southeast late this afternoon and evening. However there are
fires up in Lane County that will get transported into eastern
Douglas County, so we may not see any improvement through tonight.
Meanwhile, smoke from the Homestead Complex will push southeast into
Klamath County late this afternoon, then into Klamath Falls proper
tonight, and visibility could be reduced to 4-6sm. Tonight, as the
mixing height decreases, the smoke will settle and be confined to
around the perimeter of the fires resulting in MVFR visibility
between 3-5sm. However, a northeast drainage winds could bring smoke
towards Medford resulting in visibility lowering to 5sm northeast of
the Medford Airport late this evening and tonight. -Petrucelli
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 11 PM PDT Sunday for ORZ029>031.
Red Flag Warning until 8 AM PDT Sunday for ORZ615>620-622-623.
Red Flag Warning until 11 PM PDT Sunday for ORZ624.
Red Flag Warning from 2 PM to 11 PM PDT Sunday for ORZ625.
CA...Heat Advisory until 11 PM PDT Sunday for CAZ081>085.
PACIFIC COASTAL WATERS...Small Craft Advisory from 11 AM Sunday to 8 PM PDT Tuesday for
PZZ350-356-370-376.
Gale Warning from 5 PM Sunday to 8 PM PDT Tuesday for PZZ356-
376.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
715 PM EDT Sat Jul 20 2024
.KEY MESSAGES...
-30-60% chance of showers and thunderstorms over the southern
half of the UP into early evening. Severe weather not expected.
-Dry through early Monday afternoon with near-seasonal temperatures.
-Showers and thunderstorms from as early as Monday afternoon to as
late as Wednesday night across the area.
-High pressure and dry weather return to the forecast Thursday
through Saturday.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 256 PM EDT Sat Jul 20 2024
Upper low over northern Quebec continues to push a weak cold front
southward across Upper Michigan. Showers and isolated thunderstorms
have been spotty along the front as it has moved southward across
Lake Superior. Visible satellite imagery showing mainly scattered
clouds ahead of the front along the WI/MI line and south central U.P.
leading to modest destabilization. This zone will be the area where
shra/tsra activity will be the greatest in coverage prior to 00Z. As
high pressure and drier air builds into the area behind the front
this evening skies will clear. With light winds and clear skies
inland temperatures will fall into the 40s with 50s along the
lakeshores.
&&
.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 332 PM EDT Sat Jul 20 2024
High pressure sits over the western U.S. early this week as low
pressure troughing over northern Quebec slowly moves east with time
from early to mid this week. While ridging over Lake Superior will
keep us mostly dry until Monday, with a shortwave and cold front
moving into our region Monday night/Tuesday into the middle of this
week, we could see showers and thunderstorms return across the Upper
Peninsula as we head into the mid-week. As the high pressure ridging
from the western U.S. slowly trudges eastwards with time, expect it
to finally be felt over our area by around Thursday, keeping our
area dry through the rest of the week into early next weekend.
Additional details follow below.
Expect a very pleasant day Sunday as a weak surface high pressure
moves over Lake Superior. With the weak high strengthening the Lake
Superior lake breeze, expect light north to northeasterly winds up
to 10 mph across most of the U.P. Sunday, save for right along the
Lake Michigan shoreline where the CAMs show the lake breezes
colliding. While we could see a stray shower or two over the far
west early Sunday, decided to keep chances at 10% or less over there
as only the HRRR shows this solution; other CAMs are too dry to
allow for any convection, and the better forcing is south in
Wisconsin. Outside of the sunny skies, we could see min RHs get down
to around 30% in some spots across the interior west and east given
the radiational heating; should rainfall be lower than what`s
expected today, than we could see min RHs dip into the 20 percents
Sunday.
Expect another pleasant night come Sunday night, with clear skies
and lows getting down into the mid 40s across the interior west and
east. Monday looks to be another pleasant day too, with high
temperatures being a few degrees warmer as a cold front begins to
descend from northern Ontario towards us. In addition, conditions at
the surface may be very dry again come Monday, particularly during
the morning as the high pressure over Lake Superior leaves the area;
we could see min RHs get down to 30 percent over the interior east.
Thankfully, expect the winds to still be fairly light and lake-
breeze driven for the most part. That being said, we do have a very
weak shortwave ahead of the cold front moving through Wisconsin that
could bring some showers and t-storms over the interior west by the
afternoon hours Monday. However, given the low shear profile over
our area Monday afternoon, nothing more than garden-variety storms
are expected.
Rain chances across the area begin increasing Monday night through
Tuesday as the weak shortwave interacts with the descending cold
front from Canada. As this occurs, expect rain showers and t-storms
to crawl across the U.P. from west to east Monday night into
Tuesday. As the shortwave low begins to organize and deepen over the
Lower Peninsula Wednesday, some of the rainfall looks to begin
ending over the western U.P. as early as Tuesday night, with the
rain chances ending from west to east Wednesday into Wednesday night
as the low begins lifting into southern Ontario.
Dry weather looks to return to the U.P. by Thursday as the low
continues eastward and high pressure ridging moves overhead. The
high pressure ridging looks to keep us dry for the rest of this week
into early this weekend as medium range guidance shows slowly
warming temperatures to end the extended period (thanks to warm air
advection from the Desert Southwest). Overall, expect temperatures
near normal across the area for this week, with below normal
temperatures seen Tuesday and Wednesday and above normal
temperatures returning by the end of this week/early next weekend.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 714 PM EDT Sat Jul 20 2024
No forecast concerns through the 00z TAF period. Expect VFR
conditions at all sites with clearing skies and generally light
north to northeast winds.
&&
.MARINE...
Issued at 332 PM EDT Sat Jul 20 2024
Lighter winds of generally 20 knots or less continue through the
period as a few weak disturbances move through the area before high
pressure ridging moves in late this week. Other than that, a few
thunderstorms could be seen in the far west near Duluth late this
afternoon/early this evening (30 to 40% chance) and across the
entire lake from west to east with time Monday afternoon through
Wednesday (25% east to 50% west).
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...MZ
LONG TERM...TAP
AVIATION...BW
MARINE...TAP
Area Forecast Discussion
National Weather Service Pocatello ID
240 AM MDT Sat Jul 20 2024
.SHORT TERM...Today through Sunday Night.
Early morning satellite imagery shows a H5 ridge of high pressure
over the WRN CONUS with the center slowly shifting from the Four
Corners region to being over the Great Basin. As this ridge axis
progresses west, very dry air over the PacNW will filter in this
weekend which will work to limit convection chances to
increasingly isolated coverage for Saturday and even furthermore
on Sunday. Have lined up this afternoons 15-25% POPs more towards
the HREF probability of thunder (given a very dry NBM bias as of
late) with the HREF showing a 20-60% chance along and east of
I-15 to the Wyoming border with less than a 20% chance elsewhere.
The convective environment today will remain very similar to
previous days with around 300-800 J/kg of SBCAPE, 15-20 kts of 0-6
km shear, and 8-9 degree/km 700-500 mb lapse rates. As a result,
stronger storms will be capable of producing wind gusts to 30-50
mph (locally 50-60 mph), brief heavy rain, and frequent lightning.
PWATs in that 0.50-0.80" range will also support a mix of wet and
dry thunderstorms. For Sunday, that very dry airmass that was
over the PacNW will now be overhead which will further limit
convection chances to less than a 15% chance regionwide and have
gone ahead with a dry forecast with POPs peaking around 5-10%.
With high pressure overhead through the weekend, temperatures
will remain seasonably warm and generally about 4-10 degrees above
normal for late July which means high in the upper 80s to low
100s. Overnight lows will range from the 40s/50s/60s to low 70s
around the Magic Valley. Given our location in the NE sector of
the H5 ridge this weekend, predominant surface flow will now be
out of the N/NE which will actually help to bring temperatures
down a few degrees this weekend across the Upper Snake Plain
region but other areas will see little to no impact from this.
Synoptic winds will also see a slight uptick over the next couple
of days with gusts peaking around 20-40 mph each afternoon outside
of winds remain elevated tonight into Sunday across the Snake
Plain corridor out of the N/NE. MacKay
.LONG TERM...Monday through next Saturday.
Upper level ridge centered over the western Great Basin will
produce above normal temperatures through mid week. Heat risk
values show marginal indices for heat headlines as most nights we
are seeing good recovery. Best chance for heat advisories is
Wednesday which looks to be the warmest day in terms of afternoon
temperatures and overnight recovery. Models continue to show an
upper level trough pressing into the Pacific Northwest late next
week. This will cool temperatures to seasonable levels. Isolated
to scattered thunderstorms will remain possible most days as
monsoon moisture rotates around the center of the ridge. Best
chances for organized thunderstorms is Thursday and Friday when
the trough begins to work into the region. 13
&&
.AVIATION...For the 12Z TAFS through 12Z Sunday.
Main concern is possibility of afternoon storms. About 20 percent
of high res models are showing storms drifting near IDA, PIH and
DIJ this afternoon. Most storms look to be southeast of the TAF
sites. Unsure at this time if will introduce a mention of VC at
any TAF sites. Will take another look at latest high res model
runs before 12z TAFs are due. HRRR smoke model shows some smoke
drifting through today, but visibilities are not expected to be
affected. 13
&&
.FIRE WEATHER...
Seasonably warm and predominantly dry conditions will continue
through the weekend courtesy of a broad H5 ridge of high pressure
overhead as weak monsoon moisture over this ridge feature works to
support isolated thunderstorm activity. Best chances this weekend
will be today where a 15-25% chance of afternoon showers and
thunderstorms will exist along and east of I-15 with stronger
storms being capable of producing wind gusts to 30-50 mph (locally
50-60 mph), brief heavy rain, and frequent lightning. A very dry
airmass over the PacNW today will shift to being more overhead for
Sunday which will further limit thunderstorm chances to less than
15% regionwide.
Heading into early next week, look for much of the same with
around a 10-20% chance of showers and thunderstorms (mostly in the
mountains) each afternoon. High temperatures will also see a
gradual warming trend as a H5 ridge axis shifts east with highs
likely peaking Wednesday in the 80s to low 100s. Around that
Wednesday/Thursday timeframe, a H5 low in the NE Pacific will move
onshore to WRN Canada and help to bring a H5 trough over the
PacNW and NRN Rockies for late next week. This will support a mix
of isolated to scattered showers and thunderstorms for Thursday
and Friday when the trough begins to pass overhead which will lead
to cooler, more seasonable temperatures. In addition to cooler
temperatures and an uptick in POPs, winds will have to be
monitored as 700 mb winds aloft increase to around 20-30 kts with
lighter synoptic winds expected until then. MacKay
&&
.AIR QUALITY...
Patchy wildfire smoke from regional wildfires across the WRN CONUS
will continue through the weekend as evident by the latest HRRR-
Smoke model which keeps light concentrations of smoke in place. As
a result, have added the mention of patchy smoke to the forecast
regionwide which will lead to hazy/smoky skies at times. Air
quality as of 230 AM MDT remains in the "Good" to "Moderate"
categories. MacKay
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until midnight MDT tonight for IDZ051.
&&
$$
Area Forecast Discussion
National Weather Service Riverton WY
944 PM MDT Sat Jul 20 2024
.KEY MESSAGES...
- Today is similar to the past few days. Highs are around normal
for this time of year. Showers and thunderstorms are possible
through this afternoon and evening. Brief heavy rain and
gusty winds are the main hazards, but small hail is also
possible.
- A very stagnant weather pattern for this coming workweek. High
pressure building in keeps warm temperatures around. Afternoon
isolated (15%-20%) shower/thunderstorm chances, but most
remain dry.
&&
.DISCUSSION...
Issued at 1236 PM MDT Sat Jul 20 2024
The western US high pressure has shifted slightly westward for
today. This allows for some shortwave energy to move through. As a
result, showers and thunderstorms will be a bit more widespread
today. The 12Z Riverton sounding had a precipitable water (PWAT)
value of 0.70 inches. The area will generally have values 100% to
150% of normal today. Some brief heavy rain and gusty outflow winds
would be the main threats today with any convection. Gusts up to
around 45 mph are possible, though would not be surprised to see
some 50 to 60 mph outflow gusts today. Small hail is also possible
with stronger storms. Everywhere will have a chance for a shower or
storm today, with chances ranging from 15% to 70% across the area.
The mountains will have most numerous storms. Chances decrease with
the setting sun, and almost all convection should be done by
midnight. Otherwise, today`s temperatures are very seasonal, peaking
in the mid-to-upper 80s for most.
Sunday trends a bit drier, with more isolated afternoon convection,
the best chances over the mountains and across Johnson and Natrona
Counties. Temperatures are also similar, if not a few degrees
cooler. For the coming workweek, the high pressure builds back east.
This brings some warmer temperatures and less rain chances, though
it still looks like some isolated (15%-20%) afternoon convection
occurs. A little better shower/storm chances for western Wyoming
mountains. Overall, little change occurs this next week when it
comes to the broader weather pattern.
When it comes to smoke, the HRRR shows the highest smoke
concentrations over western Wyoming today, which thins this evening
and overnight. Smoke from Canada begins to make its way into
northeast Wyoming for Sunday and moves over Johnson and Big Horn
Counties Sunday afternoon, as it travels southward.
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 943 PM MDT Sat Jul 20 2024
There are a few lingering showers in central Wyoming, that will
continue to diminish through midnight tonight. VFR conditions
with mostly clear skies and light winds will prevail through
around 18Z Sunday. Afternoon convection will develop again on
Sunday, mainly impacting TAF sites east of the Divide. Storms
will be more isolated than Saturday, with chances (15-20%) at
KCPR and KLND, with even lower chances at KRIW, KCOD and KWRL.
Gusty winds and frequent lightning will be the primary threats
from thunderstorms across the CWA. There is also a chance
(10%)for some small hail with any of these storms.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence forecasts.
&&
.FIRE WEATHER...
Issued at 149 AM MDT Sat Jul 20 2024
Convection will be the driving factor behind fire weather concerns
in the short-term. Fire starts from lightning have been cropping up
over the last couple of weeks as fuels have been drying thanks to
mostly dry conditions and hot temperatures. Wind is not a primary
concern in the sense that synoptic flow will remain weak, but
plentiful outflow boundaries from convection will continue to pose a
risk to ongoing and new fires. This will be the main threats through
this weekend into early next week, but temperatures will rise, which
will result in falling RH by the middle of next week. Wind will be
the saving grace, again, since high pressure that is bringing the
hotter/drier air will keep wind light in general. Convection will
decrease in coverage, but is not likely to cease altogether, so new
fire starts from lightning will remain a threat through next
week.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Wittmann
AVIATION...Swanson
FIRE WEATHER...Rowe
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
502 PM MDT Sat Jul 20 2024
.KEY MESSAGES...
- Isolated/scattered thunderstorms possible through Monday
- Hazy skies due to Canadian fires
- Increasingly hot/dry middle/end of next week with
elevated/critical fire danger
&&
.DISCUSSION...(This Evening Through Saturday)
Issued at 127 PM MDT Sat Jul 20 2024
19z surface analysis had weak through from central ND through the
Black Hills into southern WY. Water vapour matinee had upper
ridge from the southwest CONUS into southwest Canada. Northerly
flow aloft noted over the northern Plains with a parade of weak
shortwaves rotating southward into the CWA. SPC mesoanalysis had
1-1.5KJ/kg MLCAPE along/east of surface trough with minimal cap.
Shear profiles are weak, except for a small area of 25kts
effective shear over southwest SD on the lee side convergence zone
area given northeast boundary layer flow. Geocolor satellite loop
clearly shows smoke pouring into the region courtesy of (mostly)
Canada. Forecast concern revolves around upper ridge.
Late this afternoon through Monday afternoon, thunderstorm
chances continue as shortwaves rotate through. Enough
buoyancy/shear through this evening for isolated strong/severe
thunderstorms, mainly over far southwestern SD. Weaker
buoyancy/shear expected Sunday with perhaps a small uptick for
Monday. Organized severe thunderstorm chances low. HRRR integrated
smoke guidance depicts hazy skies through Sunday night.
Temperatures will be near guidance at night, but possibly a bit
below for highs depending on smoke aloft thickness.
Monday night through Friday, upper/thermal ridge builds into the
northern Plains. Increasingly hot/dry weather expected with
chances for 100F+ readings 50%+ Thursday most areas and Friday for
western SD. Upper ridge should flatten late Friday, allowing a
cold front to move through the area. Deep boundary layer mixing
will promote gusty winds during peak insolation, especially
Thursday/Friday. While precipitation chances will be very low, an
unmentionable stray thunderstorm cannot be ruled out. Mentionable
PoPs return late Friday with potential cold front.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening)
Issued At 500 PM MDT Sat Jul 20 2024
VFR conditions are generally expected through the period.
Isolated to scattered showers and thunderstorms will continue
through this evening, especially across the southern Black Hills
area. Brief MVFR conditions can be expected near any stronger
storms. Otherwise, hazy skies from Canadian forest fires will
continue. Isolated to scattered showers and thunderstorms again
expected Sunday afternoon.
&&
.FIRE WEATHER...
Issued At 127 PM MDT Sat Jul 20 2024
Warm conditions continue through Monday with chances for
thunderstorms, but coverage will be limited. An upper level ridge
will bring increasingly hot/dry temperatures for Tuesday into
Friday. An upper ridge breaks down Friday with cold front with
some uncertainty as to the timing of the cold front. Pre-frontal
environment will be hot/dry with locally gusty winds possible.
Temperatures ahead of the front will be in the 90s to around 100.
LREF is giving 50-90% probability of relative humidity less than
15% across northeastern Wyoming and far western South Dakota. The
result will be elevated to critical fire weather conditions,
especially across northeastern Wyoming and far western South
Dakota.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Johnson
FIRE WEATHER...Helgeson
Area Forecast Discussion
National Weather Service Las Vegas NV
154 PM PDT Sat Jul 20 2024
.SYNOPSIS...Isolated showers and thunderstorms return today and
Sunday afternoons and will favor the higher terrain. Meanwhile, an
upper-level high pressure system will center itself overhead,
resulting in persistent above-average temperatures. Monsoonal
moisture will increase through the work week, resulting in muggy
conditions and a return of widespread shower and thunderstorm
chances each afternoon.
&&
.SHORT TERM...Today and Sunday.
The upper-level area of high pressure typically responsible for its
monsoonal moisture flux into the Desert Southwest will shift
overhead today. This position change will result in persistent above-
average temperatures for the Mojave Desert. As such, the Excessive
Heat Warning for southern Inyo, southern Nye, Clark, San Bernardino,
and southern Mohave counties will continue through Sunday. With the
high overhead, the moisture flux up the Colorado River Valley from
northern Mexico is cut off. However, remnant moisture trapped
beneath the high coupled with heat-driven instability and orographic
lift will result in isolated thunderstorms in the higher terrain of
the Mojave Desert and southern Great Basin each afternoon through
the weekend. This reduction in Precipitable Water (PWAT) will help
mitigate widespread flash flooding concerns, though there remains
some risk of localized flash flooding beneath stronger cells,
especially in cases of training or stationary storms.
A slight increase in moisture Sunday afternoon will allow for
increased coverage of thunderstorms across the southern Great Basin
and eastern Mojave Desert. Of particular interest, Convection
Allowing Models (CAMs) continue to highlight the occurrence of a
thunderstorm outflow impacting the Las Vegas Valley and nearby lakes
Sunday evening as a result of thunderstorms in southeastern Nevada
and southwestern Utah. This is supported by a slight shift in the
upper-level high, resulting in a northerly flow over southeastern
Nevada and by HRRR forecast soundings calling for 2200 J/kg of DCAPE
over southern Nevada. Associated with this outflow would be gusty
winds between 25 and 35 mph and additional convection along the
boundary.
.LONG TERM...Monday through Friday.
Southerly flow will return to the region through the week, resulting
in an increase of monsoonal moisture and daily afternoon scattered
showers and thunderstorms through Friday. Meanwhile, the center of
the high pressure aloft continues to wobble around the western
Mojave Desert, which will result in above-average temperatures
persisting through the week. Though forecast temperatures are not
expected to break records or approach readings experienced a few
weeks ago, the added humidity will feel oppressive. HeatRisk
indirectly incorporates humidity by analyzing diurnal spreads in
temperature and unusually warm overnight low temperatures. With that
in mind, HeatRisk doesn`t have widespread Major-to-Extreme HeatRisk,
but rather focuses in the desert valleys. Will continue to wait to
see how much of an impact this moisture has on temperatures before
pulling the trigger on an extended heat-related headline at this
time.
&&
.AVIATION...For Harry Reid...Light north to east winds through mid
afternoon. Still looking at the development of an isolated shower or
thunderstorm west of the valley over the Spring Mountains/Red Rock
Canyon between 19Z and 22Z. Outflow winds from the collapsing storm
near Red Rock Canyon could shift the wind to a westerly direction
after 22Z. Winds look to remain from a west-southwest direction this
evening and overnight. Similar conditions expected Sunday with
shower and thunderstorm formation staying along the higher terrain
west and south of the valley. Outflow winds may impact the valley
terminals with the potential for stronger outflow winds Sunday
evening from the northeast.
For the rest of southern Nevada, northwest Arizona and southeast
California...Outside of the Las Vegas Valley, isolated thunderstorms
expected over northwest Arizona, central Nevada and the vicinity of
KBIH in the Owens Valley. Erratic, gusty winds up to 30 mph at KBIH
possible between 21Z and 02Z. Ceilings will drop to 10-12 kft with
thunderstorm activity. Winds will return to diurnal trends overnight
before isolated thunderstorm chances return to the region Sunday
afternoon with similar timing. Stronger east or northeast outflow
winds are possible Sunday evening at KIFP and KEED as well as at the
Las Vegas Valley TAF sites.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...Soulat
AVIATION...Czyzyk
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