Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/22/24
Area Forecast Discussion
National Weather Service La Crosse WI
1059 PM CDT Sun Jul 21 2024
.KEY MESSAGES...
- Fog may recur late tonight into early Monday morning, with
better chances of occurrence in southeastern Minnesota and
northeastern Iowa.
- Seasonable temperatures and largely diurnal showers and storms
are possible through Wednesday afternoon.
&&
.DISCUSSION...
Issued at 249 PM CDT Sun Jul 21 2024
Tonight: Potential Fog
While fog was not as extensive spatially as forecast last night,
OLZ/CCY/AUM/TOB in SE MN/NE IA all experienced fog for several
hours, with OLZ/CCY seeing quarter mile or less visibility for 4-6
hours. Temperatures and dewpoints are similar to what was seen
yesterday except the mid 60s dewpoints are more extensive,
suggesting more of the area will see fog tonight. Have therefore
placed fog in the forecast for most of the CWA once again.
This Afternoon through Wednesday: Seasonable Temperatures, Diurnal
Convection
19z WV satellite shows a slow moving MCS, which traversed the NW CWA
slowly over the past 12 hours, in south central MN. Residual anvil
clouds are present over the NW CWA with this largely suppressing the
development of cumulus. Farther south, agitated cumulus has
developed with a few showers/storms present in Clayton/Grant
Counties. This afternoon, expect a few showers and thunderstorms,
primarily in the southeastern CWA, but a rogue bit of convection
could occur farther northwest nearer to sunset. Either way, with
little in the way of low level convergence, expect coverage to be
limited. With little flow through column, do not expect severe
storms but a localized area or two of heavy rain could occur given
slow storm motions.
Monday, convection should once again occur as a weak upper
disturbance arrives from the NW late in the afternoon. However, low
level convergence remains lacking. Therefore, think the end result
will be similar to Saturday and Sunday - some convection will occur
but not to the coverage suggested by coarser scale models and NBM
PoP output. Indeed, extended CAM runs suggest only spotty coverage.
Have therefore ensured all areas get a mention of precip but strove
to limit to a slight chance (under 25%) where possible. Given
continued weak winds through the troposphere, the main potential
hazard aside from lightning remains the same as Sunday - highly
localized heavy rain.
Monday night into Tuesday, upper support ticks upward as an upper
trough slides southeastward. While this should lead to an increase
in coverage, best convergence along the associated surface front
appears likely to occur after peak afternoon heating, once again
leaving us with issues getting parcels freely buoyant. Indeed, what
extended CAMs exist out through Tuesday afternoon suggest spotty
coverage once again. Have thus attempted to tamp down the 80% NBM
PoPs during the afternoon but have kept things solidly in the likely
(55-70%) category. The slight increase in deep shear to around 20
knots suggests a strong storm could develop but the probability for
a severe thunderstorm remains low.
Wednesday, with the main body of the trough overhead bringing cool
conditions aloft, can`t rule out a stray shower or storm as peak
surface heating occurs.
Wednesday through Saturday, heights aloft build as the
northwest flow finally abates. Expect temperatures to trend back
to the mid to upper 80s with scant chance for precip.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1059 PM CDT Sun Jul 21 2024
Fog will be the main aviation concern for the region overnight and
into the morning hours. The forecast remains somewhat challenging
with mid-level clouds once again being the primary concern. Model
soundings have suggested some saturation at 850mb which with ambient
lift from the departing upper-level wave may be enough to develop
some mid-level clouds. Otherwise, would expect areas that remain
clear to fog up with falling dewpoint depressions. At KRST, have
decided to introduce an IFR group with the recent 22.02z RAP
soundings suggesting a drier 850mb layer throughout the night. Will
have to monitor the area for possible LIFR reductions if fog can
reside at any particular location for the entire early morning
period.
As we head past sunrise, any fog will quickly disperse leading to
VFR conditions with sct to bkn mid-level clouds possible throughout
the day. Winds will remain light and variable through much of the
morning before shifting to southwesterly by mid-morning. As an
incoming trough approaches our region on Monday evening, a few
showers and storms may be possible. However, confidence remains low
in exact timing for when these will move in.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Ferguson
AVIATION...Naylor
Area Forecast Discussion
National Weather Service Bismarck ND
957 PM CDT Sun Jul 21 2024
.KEY MESSAGES...
- Isolated to scattered thunderstorms are possible this
afternoon through Monday. The threat for severe weather
remains low.
- Smoke aloft from distant wildfires will be found at least
through Monday and possibly longer. Patchy near-surface smoke
is possible, especially in north central North Dakota through
tonight.
- High temperatures will mainly be in the 80s through Monday,
while temperatures in the 90s to around 100 degrees are
expected mid to late week.
&&
.UPDATE...
Issued at 943 PM CDT Sun Jul 21 2024
Showers and storms have all but diminished, with the exception
of one little thunderstorm hanging on over southern Kidder
county. This storm will continue to drift/build west on outflow
until it runs out of fuel (which should be fairly soon).
For this update, we also decided to add mention of patchy fog to
the forecast for much of western and central North Dakota
overnight per many of the CAMs (and a similar pattern to
previous nights). Additionally, we are starting to see some
lower visibility readings due to an increase in near surface
smoke across portions of the north and west. Thus we may have to
increase the spatial area of smoke coverage in the gridded
forecast in future updates if these trends continue.
UPDATE
Issued at 626 PM CDT Sun Jul 21 2024
No major changes were needed for this update. Most of the
showers and thunderstorms are currently located over southern
portions of the James River Valley. There are a couple of
showers over the southwest as well, but this activity has been
on a weakening trend. All of this activity should diminish with
the loss of diurnal heating. Smoke aloft from distant wildfires
will continue to lead to a hazy sky.
&&
.DISCUSSION...
Issued at 249 PM CDT Sun Jul 21 2024
This afternoon, very broad surface high pressure was centered
over Ontario, with a weak low pressure analyzed in west central
North Dakota. Northerly flow aloft continued from the influence
of a potent upper ridge extending into Alberta, while a deep low
was off the coast of British Columbia. A few embedded
shortwaves were moving through the meridional flow, with
isolated thunderstorms ongoing in the southern James River
Valley area, as well as in southwest North Dakota. It`s another
day of plentiful instability but very low deep-layer shear, so
expecting another round of pulse-type thunderstorms that could
occasionally produce small hail and gusty winds. This looks to
be limited to the southern part of the forecast area through
early evening. The non-supercell tornado parameter is elevated
in the southern James River Valley, so we cannot rule out a
brief, weak funnel.
The northerly flow is also bringing a thick swath of wildfire
smoke into the region, with some near- surface smoke primarily
across northern North Dakota. We are keeping the mention of
near- surface smoke through tonight only in the north, but could
occasionally see reduced visibilities elsewhere, especially if
fog begins mixing in. The latest HRRR smoke forecast has higher
smoke concentrations moving in later tomorrow so this mention
will likely need to be extended.
Precipitation chances (20-40%) return early Monday morning in
the north central and east, persisting through the day as a back
door cold front drifts down from the Canadian Prairies.
Deterministic guidance is advertising slightly more shear (25
knots) overlapping with modest instability levels, so wouldn`t
be surprised if a few stronger storms can develop, especially in
the north central part of the state. Highs on Monday will again
be in the 80s.
The main forecast concern this week is hot temperatures returning as
the previously mentioned upper ridge shifts east. Ensemble clusters
show the ridge will be moving across the Dakotas in the middle
to end of the work week, with areas in western North Dakota
having their hottest days on Wednesday-Thursday, while the
eastern portion of the forecast area will likely be hottest on
Friday. The expectation is for highs from the lower 80s east to
mid 90s west on Wednesday, before highs in the upper 90s to
around 100 in western North Dakota on Thursday. The ridge axis
will shift further east on Friday, dropping highs back into the
mid 90s southwest, while the James River Valley will see its
hottest temperatures of the week in the lower 90s.
As the upper trough pushes east and flattens the ridge, blended
precipitation chances emerge to end the week as a deep trough
and closed low move through the Canadian Prairies. The latest
ECMWF EFI paints a more notable overlap of instability and
shear well north of the International Border as the upper low
swings through Saskatchewan and Manitoba. CSU machine learning
continues to paint widespread but low potential for severe
weather across the forecast area starting on Friday and
continuing through the weekend. With the flow pattern aloft
shifting to become more broadly zonal and less amplified, there
is increasing confidence in cooler temperatures late in the
weekend and into next week, with highs generally back to the
80s.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 626 PM CDT Sun Jul 21 2024
VFR conditions are generally expected through the period.
However, some near surface smoke may impact our northern sites
at times tonight with KMOT being the most likely. An isolated
shower or thunderstorm at any one particular site is not
likely the evening or Monday afternoon, but not impossible.
Winds may become gusty and erratic in the vicinity of any
storms.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...ZH
DISCUSSION...Jones
AVIATION...ZH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
807 PM MDT Sun Jul 21 2024
.KEY MESSAGES...
- Scattered showers and thunderstorms across the Front Range and
I-25 corridor through this evening, with the heavy rainfall
threat decreasing.
- Temperatures look to be above seasonal normals Wednesday into
next weekend.
- Increased rainfall chances for Friday through Sunday.
&&
.UPDATE...
Issued at 803 PM MDT Sun Jul 21 2024
Scattered showers and storms were moving across the plains with
most activity south of a Foprt Collins to Fort Morgan to Akron
line. This activity will continue moving southward thru the
evening with most of it ending over srn areas by midnight.
Otherwise, a lot of smoke has moved into the area with very
hazy skies. This will continue thru Monday.
&&
.SHORT TERM /Through Monday/...
Issued at 211 PM MDT Sun Jul 21 2024
As expected, poorly organized convection has continued to develop
over the past couple of hours. A few stronger embedded storms
across the higher elevations have produced briefly heavy rain, but
have largely missed the more sensitive burn areas.
Scattered showers and storms should continue through the evening
hours. Most of the DEN-FNL-GXY area is still unstable, with recent
ACARS soundings from DEN showing roughly 1000 J/kg of CAPE with
PWAT near an inch. It appears likely that some of the convection
across southeastern Wyoming will eventually drift into our
forecast area by the evening. Still, it doesn`t look like this
will be nearly as intense as yesterday evening`s I-25 corridor
event... but if you`ve got outdoor plans, keep an eye out!
The overall synoptic pattern won`t change significantly tomorrow,
but the airmass is expected to gradually dry out. Temperatures
should return to the 80s across the lower elevations, but the
drier air should limit overall instability. At least isolated to
scattered showers and a few thunderstorms are forecast across the
higher elevations, with generally <20% chances across the plains.
The other story for tonight/Monday will be a return of wildfire
smoke. GeoColor satellite imagery shows a broad plume of smoke
across the northern Great Plains, and HRRR smoke forecasts show
this reaching the Denver metro late tonight or early tomorrow
morning... continuing through most of the day. Most of this smoke
is concentrated well above the surface, but a modest increase in
near-surface smoke is possible during the day.
&&
.LONG TERM /Monday night through Sunday/...
Issued at 240 PM MDT Sun Jul 21 2024
The high amplitude upper ridge to the west of the CWA begins to
push slowly eastward on Tuesday. Models show the ridge axis to get
into the CWA by late Thursday and Thursday night. The flow aloft
will be northerly for the CWA through the period with weak
synoptic scale subsidence.
Moisture is lacking over the plains through the period, with limited
amounts for the mountains. CAPE is limited as well. Models continue
to show some alpine convection during the late day periods, with
very little to nothing on the plains. Will leave the 10-40% late
day high mountain pops going Monday evening, late day Tuesday and
late day Wednesday. Decent rainfall amounts are not expected.
For temperatures, Tuesday`s highs look to be right around seasonal
normals, then Wednesday`s warm up 1-4 C from Tuesday`s.
For the later days, Thursday through Sunday, models now show the
upper ridge right over the CWA Thursday through Friday night. They
also show the upper trough moving eastward well north of the CWA on
Saturday and Sunday to be a bit weaker than yesterday`s models
indicated. It doesn`t flatten the upper ridge down like it did on
yesterday`s runs either. The models are still indicating better
moisture and increased convection for Friday through Sunday, with
even "scattered" coverage over a good portion of the plains. We
will see. Temperatures are progged to stay above seasonal normals
all four days.
&&
.AVIATION /00Z TAFS through 00Z Tuesday/...
Issued at 510 PM MDT Sun Jul 21 2024
Outflow boundary moved across which switched winds to SSW. There
is still a chc of a few storms moving across from 01z to 03z but
confidence level is low. For now have left a tempo group thru 03z.
After 03z should see tstm chances diminish with basically
drainage winds overnight.
On Mon, it should be dry with VFR conditions. Winds will become
NNE by midday and then more ENE by late aftn.
&&
.HYDROLOGY...
Issued at 211 PM MDT Sun Jul 21 2024
Heavy rain/flash flooding concerns will slowly diminish through
this evening, as instability wanes. Ongoing storms are producing
heavy rain for brief periods at a time, with one gauge in Glen
Haven recording 0.24" in 5 minutes. However, storms have had just
enough storm motion and generally haven`t persisted for long. A
continued diminishing trend is anticipated as the ongoing
convection washes out the modest instability.
Moisture decreases further on Monday, but there should be at least
widely scattered storms across the higher elevations with a
limited threat of burn area flash flooding. There is little
concern for Tuesday through Thursday under a hot/dry airmass.
Eventually better moisture should return as we approach next
weekend, but this is too far out to discuss in detail.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...RPK
SHORT TERM...Hiris
LONG TERM....RJK
AVIATION...RPK
HYDROLOGY....Hiris/RJK
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
642 PM CDT Sun Jul 21 2024
...New AVIATION...
.SHORT TERM...
(Tonight through Monday night)
Issued at 143 PM CDT Sun Jul 21 2024
The upper-level ridge will remain over the western US through the
short term, as a positively tilted upper-level trough continues
to move across the central to northeastern US. At the surface a
weak stationary front running across Central Texas will remain in
place through the period. Ample moisture, diurnal instability, and
weak forcing along the seabreeze could support isolated to
scattered showers and thunderstorms late Monday morning through
Monday afternoon. PWAT values remain near to above 2 inches for
much of the region through the period, which could support locally
heavy showers.
Low temperatures tonight are expected to fall into the upper 70s
to low 80s across the region. High temperatures Monday afternoon
are forecast to reach the mid to upper 90s. Heat indices are
expected to peak around 108, remaining below Heat Advisory
thresholds. Low temperatures Monday night are again expected to be
in the upper 70s to low 80s.
&&
.LONG TERM...
(Tuesday through next Sunday)
Issued at 143 PM CDT Sun Jul 21 2024
-Key Message: Multiple rounds of heavy rainfall possible this
week. Low severe weather threat. Low tropical weather threat.
Confidence for beneficial rains this week remains consistent and
above average. A favorable setup for rain will persist, fueled by
ample Gulf moisture. PWAT values will push above two inches
Tuesday through Friday. Severe weather is generally not in the
cards, and the region is in a general thunderstorm outlook area
for Tuesday, with the potential too low after Tuesday right now
for any outlook category. WPC places deep South Texas and the RGV
in a marginal risk for excessive rainfall for days 3 through 5, or
Tuesday through Thursday. Operation Border Health Preparedness
will be underway this week, and rainy weather may impact access to
resource sites across the area.
On the large scale, the center of mid-level ridging will retreat
to over the Golden State (California). Meanwhile, large scale mid-
level troughing from East Canada southwest to the Southern High
Plains will supply upper instability and provide a pathway for
moisture to funnel from the Gulf northeast across East Texas and
over the Gulf States and toward the mid-Atlantic region. Ridging
and high pressure will remain stolid over the Gulf. The lack of
surface boundary forcing through much of the long term will mute
boundary layer rooted deep convection.
Total deterministic (50%) rainfall amounts summed up through
Friday reflect some areas along the RG getting 1 to 1.5 inches of
rain, while most other areas are looking at 2 to 3 inches. With
ample tropical moisture stoking the atmosphere, heavy tstorms may
occur, producing a quick one to two inches and nuisance flooding
such as ponding on roadways and flooding of low lying and poor
drainage areas. Additional rounds over the same area in a short
period could result in two to three inch totals and potentially
more serious flooding. Given the persistent nature of the models
regarding this event, later forecasted rainfall totals may
increase.
High temperatures will trend lower during the week. Lower to mid
90s may occur on Tuesday but that may be a bit generous for the
rest of the week, which could more commonly see upper 80s to lower
90s. We do not see heat advisory conditions. Low temperatures are
generally expected to be in the 70s with a few places getting
close to 80 degrees.
&&
.AVIATION...
(00Z TAFS)
Issued at 637 PM CDT Sun Jul 21 2024
Tranquil conditions will prevail through the overnight hours, with
convection ending and skies clearing. For Monday, a TEMPO has been
added for BRO and HRL for convection based on the HRRR model. Breezy
winds and partly cloudy skies will also occur with VFR in effect.
&&
.MARINE...
Issued at 143 PM CDT Sun Jul 21 2024
Tonight through Monday night...Broad high pressure will remain
situated across the Northern Gulf, supporting light to moderate
southeasterly to southerly winds along the Lower Texas Coast.
Slight seas are expected to persist through the period. Isolated
to scattered showers and thunderstorms are expected to continue
through the period, with locally higher winds and seas possible in
and around some of these storms.
Tuesday through Friday night...High pressure across the Gulf will
support light to moderate southeast winds and low to moderate seas.
We do not expect small craft advisory conditions. Isolated to
scattered showers and thunderstorms will develop from time to
time.
&&
.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE 80 94 79 91 / 10 40 30 70
HARLINGEN 77 94 75 91 / 10 30 20 70
MCALLEN 80 97 79 94 / 30 30 10 60
RIO GRANDE CITY 78 97 76 94 / 20 30 10 60
SOUTH PADRE ISLAND 82 89 80 88 / 20 30 40 60
BAYVIEW/PORT ISABEL 79 91 77 90 / 10 30 30 70
&&
.BRO WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Junction CO
510 PM MDT Sun Jul 21 2024
.KEY MESSAGES...
- Shower and storms will diminish early this evening. Storm
coverage decreases tomorrow as drier air moves in.
- Near normal temperatures today and tomorrow heat up mid week
as drier air moves in.
- Monsoonal moisture looks to return Friday and heading into the
weekend.
&&
.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 151 PM MDT Sun Jul 21 2024
Here we go again. Yet another day with scattered showers and
storms. The deepest moisture remains down south which is where
the convection has fired again today. Hi-res models were also
showing an uptick over the northern mountains and along the
Divide and this is also being borne out according to radar.
Forecast PWATs of .75 inches for SE Utah and SW Colorado remains
the same while lesser amounts up north also remain in the
forecast. Plenty of instability can also be found in those same
areas with anywhere from 400 to 800 J/kg with lesser amounts
elsewhere. We`re certainly tapping into this instability as
ground ob reports are showing around 0.5 inches of rain falling
in around 30 minutes. Pea to dime sized hail has also been
reported under the stronger cells. The HRRR has been performing
well recently and the latest run is showing this convection
continuing through around 7PM before shifting south and east.
The NAMNEST is onboard with this solution as well so we should
see this convection slowly wind down in the early evening hours.
Overnight, might see a stray shower over the San Juans but not
expecting much.
Tomorrow, following the HRRR and NAMNEST leads, should be a down
day. PWATs across almost the entire CWA will be around 0.4
inches except for the southern valleys where 0.6 to 0.8 inches
remains. If there will be any convection, that should be the
spot. Having said that, wouldn`t be surprised to see a bit more
convection than advertised as daytime heating allows a few cells
to form. We shall see. The NBM has put a larger swath of ~ 20%
PoPs for SE Utah and SW Co with 40 to 60% chance PoPs for the
San Juans. This seems very reasonable so will make no changes
there. Temperatures will remain near normal through the short
term, give or take.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 151 PM MDT Sun Jul 21 2024
The area of high pressure will be centered to our west Tuesday and
Wednesday while troughing continues to dominate the central and
eastern CONUS. Additional dry air will filter into the region,
allowing PWATs to gradually diminish back to slightly below normal
area-wide by Wednesday. As a result, look for fewer showers and
storms each day and warmer temperatures. Even so, enough residual
moisture paired with daytime heating and orographics will lead to at
least isolated convection over the mountains both days. Gusty winds
will be the primary concern but brief heavy rain can`t be ruled out.
Late Wednesday and Thursday will see a trough of low pressure drop
south from the Gulf of Alaska and push into the Pacific Northwest.
This will weaken the ridge and deflect its axis to the northeast as
the trough nudges further inland. The trough`s base will dig into
the far Northern Rockies Thursday night and into Friday, brushing
our northern zones in response. Guidance is pretty adamant that this
will bring nocturnal showers and perhaps some storms Thursday night
with widespread activity expected on Friday as the trough passes.
The breaking down of the ridge and arrival of the trough will lead
to an uptick in moisture across the region as we get back to that
tap of the monsoon with PWATs projected to return to 140 to 160
percent of normal by Friday evening. As the atmosphere begins to
saturate once more we can expect gusty outflows to become less
likely compared to those heavier rains. We`ll have to see how this
event plays out but, regardless, a return to cooler and more
unsettled weather looks increasingly likely for late in the week.
The wetter pattern continues going into the weekend as yet another
trough begins to elongate off the West Coast.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 508 PM MDT Sun Jul 21 2024
Most of the showers have come to an end. A few outflows may keep
the winds gusty for the next few hours. Showers and storms are
expected again tomorrow afternoon. Although given the coverage
KDRO and KGUC might be the only taf sites that have a chance to
get a shower. Those chances were low enough not to include in
the taf. Gusty winds may be possible around any showers
tomorrow.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...TGR
LONG TERM...MMS
AVIATION...TGJT
Area Forecast Discussion
National Weather Service Goodland KS
754 PM MDT Sun Jul 21 2024
.KEY MESSAGES...
- Scattered showers and thunderstorms through Monday evening, with
low chances of severe.
- Warmer and drier conditions forecast for the mid to latter
part of next week, with low chances for precipitation at the
end of the week.
&&
.UPDATE...
Issued at 746 PM MDT Sun Jul 21 2024
Haze from wildfire smoke will continue through at least mid day
Monday before exiting north to south.
As for rain chances tonight; guidance has been hinting at
showers and storms continuing through at least 09Z mainly for
locales along and west of the Highway 27 corridor. Persistent
new updrafts across Nebraska have thus far been able to survive
and are nearing the northern portion of Dundy county. Am
watching an outflow boundary currently in central Nebraska that
may be able to initiate new cells or briefly intensify ongoing
cells assuming it is able to make it into the CWA. Severe
weather is not anticipated but gusty winds, torrential rainfall
and perhaps some small hail would be common the strongest of
updrafts.
Interesting and subtle setup for showers and storms Monday.
RAP/NAM both show an 850mb FGEN boundary draped from Kit Carson
through Sherman and arcing up through Red Willow county. RAP
also shows a 700mb disturbance (perhaps an MCV) from South
Dakota working its way into the NC KANSAS/ SC Nebraska vicinity
through the day which should act as another source of lift for
storms. Any severe weather threat looks low as shear is forecast
to be around 10-15 knots and mid level lapse rates of 6-6.5C.
Thinking that very heavy rain and lighting will be the primary
threats with PWATS of 1.3-1.5. The strongest storms should be
able to produce some gusty winds and perhaps some hail around
penny size.
&&
.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 235 PM MDT Sun Jul 21 2024
Across the region this afternoon skies are a partly to mostly sunny
mix. Temperatures as of 200 PM MDT are ranging in the upper 70s to
the mid 80s. Winds are meandering around east-northeasterly up to 10-
15 mph at times.
Main wx concerns will focus on rw/trw chances this afternoon and
evening and again Monday/Monday evening. The latest RAP40 500mb
analysis is showing amplified ridging over the western portion of
the country, with a broad open trough the Plains and points east.
The result is a northerly flow aloft with a shortwave moving south
through east-central Colorado.
There is a weak inverted surface trough pushing into east-southeast
Colorado, and combined with the shortwave pushing into the area, are
creating scattered rw/trw mainly west of the CWA. There have been a
few isolated showers that developed in western Kit Carson/Cheyenne
counties but collapse as they move away from the surface trough.
The latest HRRR/NamNest are showing the best chances for any
convection through about 03z-04z Monday w/ the focus in Colorado and
maybe into the immediate adjacent areas near the CO/KS border. Have
put in a 15-20% chance for this tapering westward through 04z
Monday. Our CWA is currently not outlooked from SPC, so any storms
that should occur will have brief sub-severe gusts and brief
downpours, and even some small hail.
Going into Monday, the wx focus shifts to the aforementioned surface
trough that now pushes into western Kansas. Similar conditions aloft
with another weak shortwave traversing the area Monday afternoon.
Looking for a 20-30% chance for rw/trw to occur before tapering to a
20% chance Monday evening. The surface flow becoming more E/SE as
the day progresses will allow for an increase in low level moisture,
and with soundings showing inverted-v profiles around 18z-21z, low
SBCape 400-500j/kg, thinking any storms will be slight wind makers
with some locally heavy rainfall before they taper Monday evening.
High pressure and dry conditions sets up going into Tuesday as the
upper ridge begins a trek eastward.
For temps, highs in the short term period will see an upward trend
with Monday seeing a range in the lower to mid 80s, but giving way
to a range on Tuesday from the upper 80s west into the lower 90s
east. Lows each night will range from the upper 50s west into the
lower 60s east.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 209 PM MDT Sun Jul 21 2024
The main wx focus in the extended period from the latest GFS/ECMWF
focuses on the movement of a strong amplified 500mb ridge. This
feature pushes slowly eastward during this time. Models do differ
some on the placement late week as a strong upper trough swings into
the Pacific Northwest and into the north central Rockies. Current
guidance has this making a more easterly trek than digging into the
Rockies. The result of this will be limited precip potential, giving
way to a warm up with near and above normal temperatures.
There is a shortwave that works into the central Rockies late
Friday, but has a hard time pushing east due to the ridge blocking
its advancement. The system will have a 20-30% chance for rw/trw in
Colorado Friday night before pushing into the western CWA with a 20-
40% chance of precip on Saturday. limited qpf from the latest NBM
guidance and with hot temperatures expected area-wide, conditions
will be similar to the past few weeks with any storms posing a wind
threat as soundings showing DCape from the GFS around 18z-00z near
the 1500-1700j/kg mark.
For temps, highs across the region for the extended period will
range in the 90s each day, with hottest numbers seen in areas east
of Highway 25. Overnight lows will mainly range in the 60s area-
wide, but late in the week, slightly warmer east of Highway 25 as
some locales from Friday night onward could see lower 70s.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 501 PM MDT Sun Jul 21 2024
VFR conditions remain forecasted for each of the terminals for
this period; however smoke aloft from Canadian fires will remain
in the mid to upper levels throughout the night. Not expecting
any reductions in visibility due to smoke at this time. North
to south moving showers and storms will be the main focus for
the next few hours with overall lower confidence on how far
south they will survive and the magnitude of them. CAMS are a
bit more optimistic that KMCK will have the better potential for
rainfall around 08Z or so; will need to watch for any potential
AMD for that. Showers and storms will again develop tomorrow as
early as 17Z. Storms for tomorrow look to be more hit and miss
so will go with VCTS until guidance agrees on the coverage.
&&
.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 North Platte NE
742 PM CDT Sun Jul 21 2024
.KEY MESSAGES...
- Scattered showers and thunderstorms will move through western
and north central Nebraska late this afternoon and tonight.
Although the risk of severe weather is low, some storms may
produce small hail, gusty winds and locally heavy rainfall.
- Hot weather will begin building into wrn Nebraska Wednesday
and high temperatures in the 90s are expected across all of
wrn and ncntl Nebraska Friday through Sunday.
&&
.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 340 PM CDT Sun Jul 21 2024
A weak UA disturbance across wrn SD this morning dropped into wrn
Nebraska this afternoon setting off isolated ordinary thunderstorms.
A second stronger disturbance across srn ND this morning is moving
south through cntl SD this aftn and satellite shows a distinct
circulation has formed. Satellite timing tools backed by the RAP
model show this disturbance moving through ncntl Nebraska this
evening and overnight. The disturbance will continue moving south
tonight and then mostly east Monday.
The POP forecast leans on the slower more generous SREF model for
scattered showers and thunderstorms tonight and Monday. The
disturbance should be east of the area Monday evening.
The risk of severe storms is low. Winds aloft at h500-300mb are weak
at 20kts or less as is the moisture transport and theta-e advection
below 700mb. Still, the MRMS indicates small hail is ongoing across
SD and the Nebraska Panhandle from both disturbances.
There is also the potential for locally heavy rainfall. PWAT in the
RAP model is around 1.50 inches beneath the SD disturbance as it
moves into and through cntl Nebraska tonight and Monday. The
disturbance will be moving slowly south at about 15 kts but the weak
moisture advections and low ambient PWAT, near 1.25 inches, would
seem to suggest low, but not zero, potential for a heavy rainfall
center of a few inches tonight. It will be interesting to see if the
system can tighten up and become better organized across ncntl
Nebraska tonight.
Attention turns to the elevated smoke circulating south from
the fires across Canada. The smoke forecast from the RAP model
shows this smoke throughout the cntl and nrn Plains for the next
48 hours. Thereafter, the GFS shows north winds aloft Tuesday
continuing to steer smoke through Nebraska. A shift in wind
direction from the northwest is expected Wednesday which might
push the smoke east of Nebraska. For simplicity, sky coverage
has been adjusted up to 30-40 percent tonight through Monday
night.
The 00z KLBF sounding Saturday evening showed a mixing height to
just 750mb. H850mb temperatures will be used as a proxy for max
temperatures Monday and the models suggest a very modest 1C degree
rise in temperatures at that level. The temperature forecast Monday
uses the short term model blend plus bias correction for highs in
the low to mid 80s. This forecast is close to the NBM 50th
percentile.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 340 PM CDT Sun Jul 21 2024
Heat will build into wrn/ncntl Nebraska Wednesday through Sunday
with high temperatures rising into the 90s across all of the
region by Friday and lasting through the weekend. The models are
in good agreement dropping a fairly deep upper level low
through the Canadian provinces. This will cause the upper level
ridge across the wrn U.S. to flatten and build east through the
central Plains. By next weekend temperatures at h700mb across
wrn Nebraska should rise to 12C-15C with sfc low pressure across
Manitoba and the Dakotas. This well supports highs in the 90s
across wrn/ncntl Nebraska.
Isolated to low-end chance POPs are in place Friday through Sunday.
This rain chance is associated with an approaching cold front across
the nrn Plains but it`s worth noting both the morning runs of the
ECM and GFS show no storm development across wrn/ncntl Nebraska.
This makes the thunderstorm forecast next weekend speculative.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 735 PM CDT Sun Jul 21 2024
VFR conditions are expected to prevail across all of western and
north central Nebraska through Monday. Widely scattered
thunderstorms will continue through this evening but should tend
to dissipate after midnight. Winds will be light except
variable and gusty near any storm.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Taylor
Area Forecast Discussion
National Weather Service Marquette MI
722 PM EDT Sun Jul 21 2024
.KEY MESSAGES...
-Showers and thunderstorms from as early as Monday afternoon to as
late as late Wednesday across the area. No severe weather is
expected.
-High pressure and dry weather return to the forecast Thursday
through Saturday along with a warming trend.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 257 PM EDT Sun Jul 21 2024
High pressure is centered over Lake Superior this afternoon with
light northerly Lake breeze flow the primary wind direction across
the U.P. While the center of the surface ridge may nudge a little
bit eastward through the night tonight winds will remain light and
variable under mainly clear skies. Low temperatures last night fell
below the lowest available guidance across the interior west with
even a few upper 30s lows. Will undercut by a degree or two the
lowest guidance for tonight especially across the interior east as
that area will be right under the ridge axis. Otherwise...lows will
fall into the 50s closer to the lakeshores and in the far west
where light southerly return flow and some higher clouds will
arrive towards morning.
&&
.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 354 PM EDT Sun Jul 21 2024
Weak high pressure of 1018-1020 mb leaves Lake Superior Monday
morning as a weak trough of 1014-1015 mb drops down from around Lake
Winnipeg to Minnesota throughout the day. Because of this, expect a
battle between the lake breezes by the afternoon hours over the east
(with the Lake Michigan lake breeze probably/70-80% chance of moving
further inland than the Lake Superior one), while scattered rain
showers and thunderstorms look to move over the west half.
Initially, expect Monday to start out fairly similar to today, with
mostly sunny skies; high temperatures even look to be similar in
comparison to today`s, albeit a few degrees warmer. The main
difference comes in the afternoon when the aforementioned shortwave
begins firing off convection in the western U.P. around noon Central
Time with the assistance of diurnal heating. While there is plenty
of instability to work with over the interior areas, with little
forcing and lack-luster shearing overhead, no severe weather is
expected.
The showers and thunderstorms continue into the rest of
the U.P. Monday night into Tuesday morning as the shortwave low
becomes better organized and deepens to 1012-1015 mb. Uncertainty
still remains on rainfall totals and even rain chances Monday
afternoon through Tuesday as guidance as a whole has trended the
shortwave low deepening earlier and further to the northwest (near
us) in comparison to yesterday; so far, the European ensemble and
deterministic models are the most aggressive with rainfall amounts,
with the ECMWF EFI highlighting QPF amounts well above modeled
climatology, with a third of the models hinting at rainfall amounts
in the 10th percentile of modeled climatology (shift-to-tails of 0).
In addition, the LREF shows a 10-30% chance of 1 inch or greater of
rainfall Monday night through Tuesday across most of the area,
although much of this is due to the inclusion on the European model
suite. Meanwhile, other model guidance systems, including many of
the CAMs, have backed-off on rainfall totals and chances Monday
through Tuesday, with the WRF-ARW, NSSL, FV3, and HRRR keeping the
highest precipitation chances over Lake Superior and just to our
south in Wisconsin. Therefore, while there is signal for a soaking
rainfall, there is also the possibility that we will only see light
scattered showers and storms early to mid this week. Also, expect no
severe weather Monday night through Tuesday as well given the cloud
cover and the bulk shear being fairly marginal (around 30 knots).
If you were missing the lake-effect precipitation this summer, you
could be in `luck`, as inversion temperatures just may be cool
enough to get delta-Ts to around 13C right behind the main line of
precipitation Tuesday night and Wednesday. With some upslope
northerly flow to help out, we could see some lake-effect
drizzle/light rain showers over the north wind lake-effect belts
Tuesday night into Wednesday. Given the marginal delta-Ts, only a
few hundreths of an inch of rainfall are expected with these
showers. As high pressure pushes in from the west earlier than
previously expected, model guidance as a whole generally shows the
rainfall ending from west to east Wednesday, first the main line
precipitation followed by the lake-effect rainfall. Expect mostly
clear skies by Wednesday evening.
High pressure ridging dominates the latter half of the extended
period as the high pressure block over the Southwestern U.S. finally
brings ridging over the Upper Midwest the rest of this week into at
least the middle of this weekend. As the ridging moves through and
we get on its backside, expect warming temperatures from Thursday
onwards; temperatures could get up to 90F in the downslopes near
Lake Superior this weekend as surface flow picks up from the
south/southwest.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 721 PM EDT Sun Jul 21 2024
Clear and calm conditions are expected for a majority of the 00z TAF
period as high pressure will dominate the UP through the night and
most of the day Monday. A weak shortwave moving into western Lake
Superior Monday evening could kick up some showers and a possible
thunderstorm during the afternoon and evening hours in the west half
near IWD and CMX, but confidence in overall coverage is low.
&&
.MARINE...
Issued at 354 PM EDT Sun Jul 21 2024
High pressure over Lake Superior will keep lake winds 20 knots or
less the rest of today through Monday, until a cool front dropping
down from Canada increases winds from the northeast over the west
half Monday night into Tuesday; winds could gust between 20 and 25
knots throughout the day Tuesday. Behind the cool front, expect the
winds to slowly lighten, becoming 20 knots or less again by Tuesday
evening; the light winds look to remain through the rest of this
week as ridging begins building in from the west.
As for t-storm chances this week, we could see some storms as early
as Monday over the far western lake as a weak 1014-1015 mb shortwave
low drops down from Lake Winnipeg to Minnesota ahead of the cool
front. As the shortwave deepens and becomes better organized Monday
night into Tuesday near the U.P. (possibly due to interacting the
cool front), the thunderstorm chances move east with time and
generally become more confined to the southern Lake Superior
shoreline; the thunderstorm chances look to end over the far eastern
lake Tuesday night.
&&
.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 San Diego CA
143 PM PDT Sun Jul 21 2024
.SYNOPSIS...
High pressure will continue to bring hot weather for inland areas
through the middle of the week with a shallow marine layer closer
to the coast. Triple digit heat will be common for deserts and
portions of the Inland Empire, while low clouds and fog are
expected each night and morning near the coast and adjacent
valleys. Monsoonal moisture will increase over the coming days
with mountains and deserts seeing a chance of storms each
afternoon through Wednesday. Drier and slightly cooler air is
expected to come into the picture by later in the week as the
ridge of high pressure weakens.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Cumulus clouds are beginning grow across portions of the northern
mountain areas this afternoon as monsoonal moisture increases
across the region. This pattern will continue over the next few
days. For today, areas near Big Bear into northern adjacent
deserts have a slight chance of storm activity, per latest HRRR
and WRF guidance. Flow around the high becomes better organized to
let in greater amounts of moisture from the south by Monday and
Tuesday, where greater chances spreading to most mountain and
desert locations. The highest chance for storm formation will be
on Tuesday, slightly lower Wednesday. Storms may cause heavy
downpours, gusty winds, and small hail. Otherwise, the heat will
remain for inland areas through the middle of the week. As
monsoonal moisture increases, so will the humidity! Use caution if
outdoors for long periods this week and drink plenty of fluids.
The marine layer depth will remain quite unchanged through the
middle of the week, with clouds and fog impacting ares within
15-20 miles from the coast each night and morning. This will also
continue to help moderate temperatures with highs in the 70s and
80s.
The ridge of high pressure over the region will begin to break
down by Thursday and Friday, where global models indicate the
potential for a weak trough to develop. This would bring slight
cooling and drier weather to the region. Highs for inland areas
look to drop near average with western valleys seeing below
average readings by next weekend.
&&
.AVIATION...
211953...Coast/Valleys...BKN low clouds over the coastal waters and
locally onshore with bases 700-1100 ft MSL with VIS 5 SM expected at
the coast. After about 22/07Z this evening BKN low clouds re-
developing and moving inland with similar bases, tops and
visibilities to just west of KONT by 22/13Z. Local visibilities
inland 1-3 miles. Confidence in KSAN TAF low cloud forecast of low
cloud return around 22/06Z is MDT-HIGH.
Mountains/Deserts...15 percent chance of iso TSRA mainly in the San
Bernardino mtns, with less than 10 percent chance in the
Riverside/San Diego mtns 21Z Sun-00Z Mon. Lightning and erratic
winds possible near TSRA. SCT Cu expected over the mtn with bases
to 15000 ft MSL. Periods of FEW-SCT high clouds in the deserts, with
unrestricted VIS.
&&
.MARINE...
No hazardous marine conditions are expected through Thursday.
&&
.BEACHES...
High tides may produce minor tidal overflow at susceptible low lying
beach parking lots and boardwalks. High tide Sunday night is
expected to peak at 6.8 ft at 9:45 PM. High tides will gradually
lower through the middle of the week.
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 9 PM PDT Wednesday for Riverside County
Mountains-San Bernardino County Mountains-San Bernardino
and Riverside County Valleys-The Inland Empire-San Diego
County Mountains-San Diego County Valleys.
Excessive Heat Warning until 11 PM PDT Wednesday for Apple and
Lucerne Valleys-Coachella Valley-San Diego County Deserts-
San Gorgonio Pass Near Banning.
PZ...None.
&&
$$
PUBLIC...APR
AVIATION/MARINE...Small
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
939 PM MDT Sun Jul 21 2024
.KEY MESSAGES...
- Hazy skies through at least Monday night
- Isolated to scattered thunderstorms through Monday afternoon
- Increasingly hot/dry Tuesday through Friday with elevated to
critical fire weather developing
&&
.DISCUSSION...(This Evening Through Sunday)
Issued at 210 PM MDT Sun Jul 21 2024
20z surface analysis had weak trough snaking across central MT to
central SD to northern MN. Water vapour loop portrayed upper
ridge over the western CONUS and upper low over IL/IA. Northerly
flow aloft over the CWA. Zooming in, weak shortwave/MCV (from
eastern ND convection last night) drifting south/southwest
supporting a small gently pinwheeling cluster of TSRA over central
SD. Outflow from this feature interacting with surface trough
east of the Black Hills producing isolated TSRA. Last area of
focused convection is at the southern end of the Black Hills per
convergence courtesy of northeasterly boundary layer flow. SPC
mesoanalysis depicts 1-1.5KJ/kg MLCAPE over western SD this
afternoon, which will continue to fuel isolated/scattered
convection. Shear weak with outflow dominated storms evident per
KUDX radar loop. Persistent thunderstorms over the southern Black
Hills could pose a threat for flooding this afternoon, but
otherwise organized convection unlikely through this evening.
Concern then turns toward upper ridge for the rest of the week.
Tonight/Monday, isolated/scattered thunderstorms through this
evening wane overnight and then redevelop Monday afternoon.
Shear sufficient for organized convection low. Temperatures will
be near guidance, except perhaps for highs Monday when smoke aloft
per HRRR integrated smoke guidance continues.
Tuesday through Thursday, upper ridge expands into the northern
Plains promoting thermal ridge over the CWA. Smoke aloft may
linger into Tuesday, but ridge should shield the area for the
middle of the week. While a stray thunderstorm cannot be ruled out
through Thursday afternoon, chances are unmentionable. High-based
thunderstorms could develop Thursday evening over northeastern
Wyoming. Gusty winds may develop during peak insolation,
particularly Thursday, but chances for gusts greater than 25 MPH
relatively low at this time. Friday, upper ridge strength
decreases as it flops into the eastern CONUS allowing an upper
trough to scoot across southern Canada. Feature should push a
"cold" front through the CWA Friday with thunderstorm chances
lasting into next weekend under southwest flow aloft. LREF chances
for 100F+ temperatures 30-70% across northeastern WY/far western
SD Thursday and 30-50% east of the Black Hills Friday.
&&
.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 937 PM MDT Sun Jul 21 2024
Isolated thunderstorms in southwest SD will dissipate around
midnight. Brief MVFR conditions in stronger storms. Isolated
showers and thunderstorms will redevelop Monday afternoon. Hazy
skies will continue through the period, with local MVFR
visibilities possible.
&&
.FIRE WEATHER...
Issued At 210 PM MDT Sun Jul 21 2024
An upper level ridge will bring hot and dry conditions Tuesday
through Friday. As the upper ridge breaks down Friday, a cold
front will slip into the area. There is considerable uncertainty
with the cold front timing. The pre-frontal environment will see
temperatures in the 90s to around 100 and very low relative
humidities. LREF is giving 70-90% probability of relative
humidity lower than 15% across northeastern Wyoming and far
western South Dakota Thursday afternoon. The pattern also favors
some windy areas which would result in critical fire weather
conditions Thursday for parts of the area, and perhaps dry
lightning over northeastern Wyoming Thursday evening.
Elevated/near critical fire weather conditions are expected Friday
with the higher winds mainly east of the Black Hills. Relative
humidity recovery Wednesday and Thursday night will be poor over
the higher terrain of the Black Hills and northeastern Wyoming.
&&
.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
825 PM PDT Sun Jul 21 2024
.SYNOPSIS...High pressure continues to meander across the Desert
Southwest, resulting in diurnal rounds of showers and
thunderstorms, and a continuation of extreme heat. This pattern
looks to hold through the majority of the upcoming week.
&&
.UPDATE...
Ongoing showers and thunderstorms will gradually wane into the
late evening and overnight hours. Activity has generally
underperformed compared to what many of the convective-allowing
models would suggest. The latest hi-res ensembles are a bit closer
to what is currently transpiring, showing widely scattered
activity struggling to persist much beyond about 11pm to midnight.
Still, a low probability of a few showers and a stray storm will
persist through the next few hours, mainly across the Las Vegas
Valley and portions of Mohave County in Arizona. The main
consideration from any storms has been gusty outflow winds as
storms collapse within a deeply mixed and hot environment. At
times, wind gusts have exceeded 40 mph, though the potential for
strong downdrafts will generally diminish as daytime heating is
lost further into the evening. Once activity ends, expect another
very warm night with lows generally in the 80s and 90s most areas.
&&
.PREV DISCUSSION...
.DISCUSSION...Today through Saturday.
Convection expected again this afternoon across the region. PWATs
range from 0.75 to 1.25" across the southern Great Basin and
northern Mojave Desert this afternoon, though instability is limited
with a 500 mb area of high pressure directly overhead. Instability
will rely on daytime heating with a convective temperature in Las
Vegas at 113 and orographic lift with storms favoring the higher
terrain. Storms that form in southern Nevada and southwestern Utah
will likely kick out strong outflow winds between 30 and 40 mph with
over 2000 J/kg of DCAPE. HRRR runs have been consistent since 24
hours ago in showing an outflow from afternoon storms in southern
Nevada pushing southward and riding the northerly steering flow into
eastern San Bernardino County and southwestern Mohave County this
evening. Convection is expected to form along this outflow as the
air moves into a region of CAPE values exceeding 1000 J/kg and PWATs
approaching 1.50". SPC has a Marginal Risk of severe thunderstorms
in the southern Colorado River Valley surrounding Needles and Lake
Havasu City to reinforce this forecast.
PWATs will range from 100 to 200 percent of average across the
region through the week, which will return chances of precipitation
to the forecast area each afternoon through Friday.
Friday through the weekend, there is good agreement that the area
will dry out with the approach of an upper-level trough that will
effectively squash the monsoonal high overhead. ECMWF ensemble
members show a stark drop in PWATs between Thursday afternoon and
Saturday afternoon.
In addition to moisture, above-average temperatures will persist
through the work week. There is an Excessive Heat Warning out for
the Mojave Desert including Las Vegas, Mesquite, Pahrump, Laughlin,
Lake Havasu City, Kingman, Barstow, and Death Valley that originally
went through 9pm tonight. However, this Excessive Heat Warning has
just been extended through Wednesday at 11pm for all aforementioned
locations. Morning low temperatures will flirt with daily records
across all climate sites (for more details, see the CLIMATE section
below), which will result in minimal relief. Additionally, monsoonal
moisture in place will result in hot and muggy conditions - rather
than hot and dry. Despite temperatures being cooler than experienced
a few weeks ago when several climate sites across our forecast area
observed all-time hot temperatures, it is likely that conditions
this week will feel worse due to the increased humidity. Moisture
allows the air to retain heat for longer, which also means that
shaded locations will provide less relief than normal. HeatRisk
values are likely to underestimate this heat wave, as humidity is
not directly taken into account during the calculation. It is
important to take frequent breaks in air conditioning and drink
plenty of water and electrolytes.
There remains high confidence in an upper-level trough dropping from
the Pacific Northwest late-week into the weekend, which will work to
squash our monsoonal high. Temperatures will moderate and dry
conditions will return to the region.
&&
.AVIATION...For Harry Reid...Light easterly components should become
southwest around 23-00Z this afternoon. Showers and thunderstorms
building over the mountains to the north of the Las Vegas Valley
late this afternoon and evening may move to the south and impact the
terminal area with gusty northeast and erratic winds between 02Z and
05Z. Thunderstorm potential will diminish after 05z with loss of
daytime heating and once storm influences abate, winds will revert
to light overnight southwest components and easterly components
during late Monday morning into the afternoon. Thunderstorms will
likely develop again over the mountains west and north of the
terminal area Monday afternoon with the potential for erratic
outflow late in the afternoon and evening.
For the rest of southern Nevada, northwest Arizona and southeast
California...Isolated to scattered thunderstorms will develop this
afternoon/evening, bringing erratic winds, heavy rains and
lightning. The Las Vegas Valley airports and Lower Colorado River
Valley sites from IFP to EED and HII may see gusty and erratic winds
from thunderstorms between 02Z and 06Z this evening as storms move
toward the south. Showers and thunderstorms near KBIH and KDAG could
also impact those areas with gusty and erratic winds between 00Z and
03Z.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...Austin
AVIATION...Salmen
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