Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/13/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
903 PM MDT Mon Jul 12 2021
.UPDATE...
Issued at 850 PM MDT Mon Jul 12 2021
There are still a few on-going showers in the mountains at this
time. Rainfall from these showers is/was very light. There are
several boundaries moving around the plains right now. Winds
across the CWA are light and variable. Not to many changes are
needed to the GFE grids this update. Satellite pictures are
showing extensive deep layer smoke across, about the western one
half of the Unites States right now, and certainly covering the
CWA. Will leave the smoke in tonight.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 137 PM MDT Mon Jul 12 2021
Warming has been slowed today by the smoke. The slightly cooler
temperatures has helped to stabilize the airmass, which wasn`t
going to be all that unstable to begin with. Lowered PoPs for the
rest of the day to reflect this. Expect isolated showers and
storms to track south- southeast across the higher terrain. Don`t
expect them to survive or form over the lower elevations and
removed the mention of showers and storms from the forecast for
the rest of today.
An upper level trough moving across Montana will help push the
ridge southwest on Tuesday. Surface low pressure will deepen over
Wyoming in advance of the trough. This will cause south/southeast
winds to increase across eastern Colorado and advect moisture into
the area. Precipitable water values increase to around an inch
across the plains. Over the higher terrain, precipitable water
values climb to around three-quarters of an inch. CAPE won`t be
all that impressive with 400-800 J/kg over the eastern plains and
200-600 J/kg farther west. Gusty winds to 50 mph and brief heavy
rain will be the main threats with the showers and thunderstorms.
Will have to see how much the smoke impacts temperatures, and thus
stability Tuesday afternoon. With some smoke, still expect highs
to reach the lower 90s, but if it is as thick as today.
Temperatures may only reach the upper 80s and may decrease the
amount of convection Tuesday afternoon/evening.
.LONG TERM...(Tuesday night through Monday)
Issued at 137 PM MDT Mon Jul 12 2021
Tuesday evening, isolated and high based showers and storms may
come off the high terrain and bring gusty winds and light rainfall
to the eastern plains. A shortwave trough will push a weak cold
front over the plains early Wednesday as it moves from the
northern Rockies towards the Dakotas. Wednesday should be a bit
cooler behind that front, with highs back down in the mid to upper
80s across the plains. The front will also bring an increase in
low level moisture and some northeasterly upslope flow into the
foothills, probably around 10 knots. Wednesday should have the
best moisture of the period, models are showing precipitable water
values up to around 1.0 to 1.25 inches over the lower elevations
and 0.5 to 0.8 inches over the higher terrain. Expect scattered to
widespread showers and storms Wednesday afternoon and evening,
with the best coverage and intensity over the high terrain. A few
severe storms are possible given some moderate instability and
shear, but the main concern should be for heavy rainfall. The
greatest precipitation should occur on the east slopes of the
Front Range, especially over the foothills, as those areas are
favored by the upslope flow.
The most recent HRRR Smoke model output suggests significant
concentrations of smoke still in the air come Wednesday, which
continues to make sense given the large smoke output of many
active fires upstream and the transport flow aloft. However, the
early cold front should help to clear some smoke from the near
surface and greater moisture and precipitation should wash some of
the particulate from the air as well, resulting in lesser
concentrations felt in the lower levels for a little while.
Thursday should see similar conditions to Wednesday, but with
less moisture and therefore precipitation. Expect similar
temperatures, and some models are now even suggesting that it
might be just slightly cooler. A gradual warming and drying trend
should set back in Thursday and Friday and persist through the
weekend as a large ridge builds over the Rockies again.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 850 PM MDT Mon Jul 12 2021
Easterlies are still blowing at DIA right now. Models do show
normal drainage patterns by 06Z tonight. Will leave the "FU"
mention in the TAFs; no way around that. There will be no ceiling
issues overnight.
&&
.HYDROLOGY...
Issued at 137 PM MDT Mon Jul 12 2021
Isolated thunderstorms are expected over the mountains and
foothills through early evening. Most of the rain today is
expected to be light. The flash flood threat for the burn areas
will be very low through tonight. Moisture will increase on
Tuesday with scattered thunderstorms expected to form Tuesday
afternoon. A brief period of heavy rain will accompany the
stronger storms and could cause localized flash flooding if one
passes over a burn area.
Scattered to isolated showers and storms will persist into the
evening Tuesday, but most will still be high based and produce
light rain which keeps the flash flood threat low. Brief, locally
heavy rainfall may still be possible with stronger storms.
Better moisture Wednesday and Thursday will mean increasing
shower and storm coverage with more significant precipitation. The
greatest moisture and precipitation of the period is expected
Wednesday. Upslope flow into the Front Range could result in
stronger storms and an elevated flash flood threat for burn areas
east of the Continental Divide, namely, Cameron Peak and Calwood.
A similar situation with similar threat levels is possible on
Thursday, though overall less moisture and precipitation are
expected. A gradual warming and drying trend will likely set back
in Thursday and persist through the weekend, with decreasing
precipitation and impacts.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......RJK
SHORT TERM...Meier
LONG TERM....EJD
AVIATION.....RJK
HYDROLOGY....EJD/Meier
Area Forecast Discussion
National Weather Service Caribou ME
1054 PM EDT Mon Jul 12 2021
.SYNOPSIS...
High pressure will build in from the north through tomorrow. A
warm front lifts north Tuesday night into early Wednesday. A
cold front is expected to cross the region on Thursday.
Unsettled into the weekend with a series of disturbances
affecting the region.
&&
.NEAR TERM /THROUGH TUESDAY/...
Update...
High pressure will cross the region overnight with mostly
clear/partly cloudy skies. Could also have patchy fog Downeast
late tonight. Low temperatures will range from around 50 to the
mid 50s north, to the mid to upper 50s Downeast. Have slightly
decreased low temperatures across portions of the region with
this update. Have also updated to adjust for current conditions
along with overnight clouds.
Previous Discussion...
Tonight...One thing to note, is that at the sfc, the high is
expected to start moving east later tonight w/an ESE light flow
to set up. This could begin to bring in some llvl moisture
below 925 mbs(around 1500`), which could allow for some fog and
low clouds to set up. Attm, the best potential looks to be right
along the coast and possibly portions of interior Downeast by
daybreak. The latest SREF and HRRR point to this potential. The
NAM hints at the potential for some as well w/the low clouds.
Therefore, decided to go w/some fog and showed some clouds
moving on to the coast by around the daybreak hrs. Further n.
clear to partly cloudy skies overnight. Temps are expected drop
back into the mid/upper 50s.
For Tuesday, looks like a rain-free day w/humidity gradually on
the increase. The 12Z NAM and GFS show moisture increasing
during the as that stalled frontal boundary begins to lift back
to the n as a warm front. Both show the potential for some
light rain showers or drizzle setting up around the western
periphery of the high w/some weak forcing aloft. The GFS is more
robust w/brining the rain further n, while the NAM holds it
back across far southern Maine and se New Hampshire. Went w/a
blend and brought 20-30% pops to the western areas late in the
day and this might be overdoing it, given the lack of
significant forcing aloft.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
A warm front wl be lifting thru the region Tue night. Sfc high
builds east into the Canadian Maritimes during the evening. Ridging
aloft fm sern high wl slide south and east and allow s/wvs to begin
to flatten ridge, especially acrs the west by Wed morning. For those
areas that don`t see rainfall late Tue night an inversion wl develop
and trap moisture near the sfc in the form of stratus, fog and
possibly drizzle. Some question as to how far north marine layer
will be able to make it Wed morning. With srly flow, extensive cloud
cvr and warm advection temps wl only be able to fall to near 60
overnight.
Little diurnal range is expected on Wednesday with maxes below
normal. Ridge wl be flattening as lead shortwave ejects twd the
northwest. Elevated instability wl be present with a chance for
thunder acrs most of the region in the afternoon and into the
nighttime hrs. This type of pattern wl allow fog to persist in a
warm and soupy airmass.
Weak boundary wl mv thru Wed night but wl bring thru very little
change in airmass. Skies wl become partly cldy and rain wl gradually
come to an end Thu afternoon. This wl allow high temps to rebound
twd the 80s areawide with dewpts rmn in the 60s as frontal bndry
rmns north acrs srn Canada.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Early in the long term, models diverge with location of front to our
north, along with wave riding up along it. 12z EC and GEM indicate
boundary will be located to the north of the Gulf of St. Lawrence
while GFS is a little murkier with it`s location. Operational EC has
the support of it`s ensemble mean. Minimal precip is expected Thu
night into Friday morning before front begins to approach. Due to
uncertainty in movement of sfc low riding along front and initial
location of bndry hv followed NBM with chc pops for the area on
Friday, though they may be able to be lowered by later shifts as
models come into better agreement. Either way it appears an active
pattern wl be setting up for the weekend and possibly into early
next week.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Generally VFR overnight through Tuesday. However,
variable conditions possible with any fog late tonight through
early Tuesday Downeast. Light and variable winds overnight.
South/southeast winds around 10 knots Tuesday.
SHORT TERM:
Tuesday night-Thursday...Low stratus and fog likely to affect
Downeast terminals Tue night and Wed night bringing LIFR
restrictions each morning. Brief improvement to MVFR/VFR each
afternoon and BGR and BHB. Uncertainty as to how far north IFR
will make it with KHUL possibly seeing IFR but confidence is
low, with northern terminals likely seeing patchy IFR fog each
morning in valley fog. Cannot rule out restrictions in thunder
each afternoon and evening across the north at all terminals.S
5-15kts and gusty each afternoon.
Thu night-Sat...IFR possible each morning in fog before improving
to VFR in the afternoon on Friday. MVFR/IFR possible in showers
and storms Friday night and Saturday. Light SW Thu night
increasing to S 5-10kts Fri morning.
&&
.MARINE...
NEAR TERM: Winds/seas below small craft advisory levels overnight
through Tuesday. Visibilities lowering in developing fog
overnight, then fog persisting Tuesday.
SHORT TERM: Seas and winds to remain below SCA thresholds into
Saturday. Areas of fog, perhaps locally dense at times, is
expected through the end of the week.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...Norcross/Hewitt
Short Term...Farrar
Long Term...Farrar
Aviation...Norcross/Farrar
Marine...Norcross/Farrar
Area Forecast Discussion
National Weather Service Grand Rapids MI
1056 PM EDT Mon Jul 12 2021
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 307 PM EDT Mon Jul 12 2021
- Marginal svr and flw risk late this afternoon into tonight
- Strong storms possible Tue
- Organized convection Wed night to Thu night
&&
.UPDATE...
Issued at 1056 PM EDT Mon Jul 12 2021
What appears to be an MCV is moving northeast from Northeast
Indiana into South Central Lower Michigan. In the wake of this
feature precipitation has been on the decrease across much of
Northern Indiana. This does not bode well for precipitation
chances across Southwest Lower Michigan tonight.
We do expect some shower and thunderstorm development tonight
however as a weakening warm front lifts north into Lower Michigan
along with a glancing blow from a weak 20kt or so low level jet.
Feel the upper trough moving in from the west will aid in some
precipitation production as well. The highest pops late tonight
will remain in the northwest and west which will be in closest
proximity to the upper trough.
&&
.DISCUSSION...(This evening through next Monday)
Issued at 307 PM EDT Mon Jul 12 2021
- Marginal svr and flw risk late this afternoon into tonight
Mid to upper level low over IL opens up and lifts through Lower
MI into Tuesday. Steady 500 mb height falls occur as PWAT values
climb up to around 1.75 inches. So far the low clouds have limited
the destabilization today. However the clouds will be breaking up
from south to north allowing for a few hours of warming
temperatures. Thus we could start to see a few storms
developing...mainly after 22z. Bulk effective shear is shown to
climb to 25 to 30 knots during the evening. Thus a few storms may
become organized. However the progged ML CAPE only rises to around
500 j/kg for places like Kalamazoo to Jackson. Mid level lapse
rates are weak as well. With continued height falls through the
night...we will likely maintain the convection. Where the cells
persist...some hydro impacts could occur. The past couple of runs
of the HRRR have shown the Battle Creek to Jackson area as a
location to potentially see several inches of rain through
tonight.
- Strong storms possible Tue
Morning convection may be loosely organized given lower
bulk effective shear values progged...around 20 knots and low ML
CAPE values. As we go into the afternoon ML CAPE increases and
could support a few pulse stronger cells...especially for eastern
parts of the CWA where the bulk effective shear is forecast to be
higher.
A cap arrives Wednesday so for now...we are leaning toward
a dry forecast.
- Organized convection Wed night to Thu night
A low level jet forms upstream in the Southern Plains Wednesday
morning and migrates through the Northern Lower MI later Wednesday
night. This could allow for elevated strong storms that may clip our
NW CWA then.
Models have been advertising the arrival of a mid to upper level
wave Wednesday night into Thursday from the west. The latest high
res euro shows the 300 mb winds increasing overhead to 70 knots
around 00z Fri. Bulk 0 to 6 km shear values are shown to be around
35 to 40 knots from the high res euro but 40 to 50 knots from the
GFS...thus an increased risk for organized convection could
develop. At the same time a surface front is shown to be tracking
through the CWA during the afternoon and evening. How much of an
impact these storms result in will likely be influenced by how
unstable the airmass becomes Thursday and whether the morning
convection alters the setup. For now...we will feature high POPs
and continue to highlight the risk in social media and the
hazardous weather outlook.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 815 PM EDT Mon Jul 12 2021
Weak low pressure is centered over portions of Central Illinois at
00z. A warm front extends northeast and then east from the low
into portions of Northern Indiana. The low will move northeast
to out over Lake Michigan tonight with the warm front lifting
northward into Lower Michigan. In a weak wind / moist airmass
setup, we should see low clouds expand in coverage and lower
further through the night. In fact, by 12z most of the area should
be below the 1,000ft level socked in with IFR clouds. The IFR
conditions should lift to MVFR in the early afternoon (16z-18z).
VFR weather should develop in the late afternoon (21z-00z) on
Tuesday.
As for the weather, we should see occasional showers and scattered
thunderstorms lift north from Indiana through the TAF sites
tonight. Between 06z and 12z visibilities should dip into the MVFR
category at all TAF sites due to scattered showers and especially
some light fog. Another round of showers and storms is likely
from midday on Tuesday into the afternoon hours (17z-23z).
&&
.MARINE...
Issued at 307 PM EDT Mon Jul 12 2021
Overall through Wednesday the pressure gradient remains relatively
weak which will act to keep the wind under 20 knots. The arrival of
front Thursday into Thursday night could strengthen the winds out of
the south to southwest. Storms at around that time could result in
gusty and variable winds.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...Duke
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...Duke
MARINE...MJS
Area Forecast Discussion
National Weather Service Lake Charles LA
942 PM CDT Mon Jul 12 2021
.UPDATE...
After a fairly active late afternoon to early evening
period, convection seems to finally be moving out of the area,
though a few showers are still noted near Alexandria. Best chance
for any future development through the night likely also remains
in the north portion of the CWA, closer to the influence of the E
CONUS trough... Though thinking overall PoPs will remain limited.
Biggest threat for any weather would come in the form of
fog/mist development after midnight, especially where some of the
higher rainfall totals from earlier were. While thinking any fog
that does form should largely remain patchy and shallow in nature,
SREF does give ~20-40% probs of visibility less than 1 SM north
of the I-10 corridor. For now, kept fog out of the WX grids, but
it`ll be something to monitor overnight. Otherwise, only made
minor adjustments to the gridded forecast to align with trends and
short term guidance, and the remainder of the forecast looks to
be in good shape.
50
&&
.PREV DISCUSSION... /issued 612 PM CDT Mon Jul 12 2021/
AVIATION...A intermittent line of showers and storms will
continue east across the region through the next few hours. Gusty
winds, reduced vis, and frequent lightning will be possible along
with MVFR ceilings. Conditions will improve after sunset, however
patchy fog may develop late tonight. More thunderstorms will be
possible again Tuesday with lower vis and ceilings likely in
storms.
PREV DISCUSSION... /issued 330 PM CDT Mon Jul 12 2021/
DISCUSSION...
SHORT TERM [Tonight through Wednesday Night]
A series of disturbances wrapping around an upper level low
centered over Illinois this afternoon continues to send lines of
convection through the area. The next of these is presently
moving through Polk and Liberty counties in southeast Texas as of
this writing. Latest runs of the HRRR show this line gradually
weakening as it moves across the region with the loss of daytime
heating.
A weak surface pressure gradient will allow winds to calm
overnight and with soils remaining saturated, patchy light fog
appears likely once again during the early morning hours tomorrow.
Don`t expect fog to become dense enough to be anything more than a
minor nuisance. Any fog that develops will quickly dissipate after
sunrise.
The aforementioned upper low will begin to lift off to the
northeast tomorrow and while there will still be some marginal
upper level support, convection tomorrow will be more diurnally
driven and less well organized than has been seen the last couple
of days. Wednesday`s convection will be exclusively diurnally
driven with weak gradients both at the surface and aloft. With
such a weak atmospheric profile, it wouldn`t be a surprise to see
tropical funnel clouds develop Wednesday afternoon.
Jones
LONG TERM [Thursday through Monday]...
Not many changes in the extended period this afternoon, as global
models continue to show the region on the western flank of a low/mid
level ridge that will maintain a steady and moist SE flow underneath
a general weakness aloft. This will yield daily and mainly diurnally
driven showers and thunderstorms with daytime highs in the lower 90s
and morning lows in the lower to mid 70s.
13
MARINE...
A light to moderate onshore flow will persist through the
forecast period. Scattered showers and thunderstorms will be
possible each day through next weekend. Locally higher winds and
seas will be possible around storms.
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 72 89 73 91 / 40 50 10 30
LCH 75 89 75 89 / 30 50 10 50
LFT 74 89 75 90 / 10 60 10 50
BPT 75 90 75 89 / 30 40 10 40
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
751 PM EDT Mon Jul 12 2021
.SHORT TERM...(This evening through Tuesday)
Issued at 323 PM EDT MON JUL 12 2021
An overall quiet day was observed across Upper Michigan today. Temps
have climbed into the 70s and low 80s across the region and with
mostly clear skies, this has turned out to be a nice summer day so
far. There was still some lingering haze associated with the fires
to our northwest in Ontario, particularly over the lake and in the
Keweenaw. As low-mid level winds shifted to be predominately
southerly, GOES 16 products have observed the smoke patch lifting
northward. This has matched fairly well to what the HRRR anticipated
through the day.
The overall synoptic picture is painting a scenario where a blocking
ridge across the western Atlantic and East Coast continues to
mitigate much movement of a pinched off upper level low over the
middle-Mississippi River Valley. This has allowed dry air to remain
over the region. Tonight though, as the low finally devolves into an
open wave and begins riding the ridge top, expect cloud cover to
increase in the south and east. At the same time, expecting chances
of rain showers to increase. Lows look to be in the 50s across the
region, with some low 60s by the lakeshores being possible.
Rain showers will continue lifting from the south on Tuesday, mainly
in the east. The central and west are expected to stay dry. Given
the slightly warmer airmass and partly cloudy to clear skies over
the west and central, expecting highs to climb into the low to mid
80s. In the east, more moisture will make it feel muggy as highs
climb into the 70s.
.LONG TERM...(Tuesday night through Monday)
Issued at 334 PM EDT MON JUL 12 2021
Although Upper Michigan will be under an unsettled pattern coming
up in the long-term period, the model trends have been drier
and/or more southerly, making precip chances much more hit and
miss this week. Some low-end PoPs appear tomorrow night, but the
better chances hold off until late Wednesday into Thursday as an
amplifying trough approaches the Upper Great Lakes. Models had
been trying to develop a well-defined low that followed a path
reminiscent of a fall system, but the 12z GFS run has backed off
on that, with the ECMWF maintaining a more robust system, and the
CMC and NAM falling somewhere in the middle of these two opposing
solutions. Regardless of the low`s strength, where models do have
better agreement is it tracking somewhere in the vicinity of
northern Lake Michigan, which would generally limit precip chances
further to the west in the U.P. As the low marches off toward the
NE and the parent trough keeps a progressive motion, so too go
the precip chances, allowing for high pressure to build back into
the region and dry conditions to prevail next weekend.
Temperatures continue a slow yet steady increase from how they`ve
been as of late into Wednesday before briefly dropping off in
conjunction with the aforementioned system. As ridging returns
later this week into the weekend, so too do the summer temps with
widespread 80s. Lows will of course respond accordingly, with the
warmest nights in the period looking to occur tomorrow night and
then next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 750 PM EDT MON JUL 12 2021
VFR conditions and light winds will continue at KIWD/KCMX/KSAW thru
this fcst period. A disturbance over the Mid-Mississippi Valley will
lift ne across the Great Lakes region on Tue. However, associated
pcpn will most likely pass e of KSAW. If not, a few -shra may be in
the KSAW vcnty late tonight/Tue morning.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 323 PM EDT MON JUL 12 2021
Winds will remain below 20 knots through at least Wednesday. From
there, some northeasterly to easterly winds gusts to 25 knots will
be possible into Thursday night as a low moves through the Upper
Great Lakes. Beyond this and through the weekend, winds are expected
to remain below 20 knots. With increasing chances for rain starting
Tue, fog could be a possibility, especially associated with the
system Wednesday night into Thursday. Given that confidence isn`t
high enough, will wait to add it to the forecast.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JP
LONG TERM...lg
AVIATION...Rolfson
MARINE...JP
...Updated for 00Z Aviation Forecast Discussion...
.DISCUSSION...
Issued at 410 CDT Mon Jul 12 2021
Pleasant conditions around the area this afternoon with current
temps close to 80F and northeasterly winds generally under 5 knots.
Canadian wildfire smoke is evident on GOES 16 loop and, to a lesser
extent, just by looking out the windows here in Valley. It is notably
more dense on the western periphery of the area. The 12Z run of the
HRRR shows it becoming more dense tonight.. though the Canadian smoke
in place now will be replaced by smoke working in from the western
U.S.
Temps continue to climb for Tuesday on the strength of continued
sunshine and WAA on southerly flow that should drive temps up by
5-10F and equal seasonal norms.
A compact and relatively weak shortwave will eject from the
northern Rockies on Tuesday night and produce a chance at severe
weather along the Nebraska/SD state line before diving southeast.
Wouldn`t be surprised to see these storms linger a bit longer
than advertised with the LLJ ramping up as it approaches Nebraska.
Have boosted POPs in northern portions of the CWA. Storms are
expected to be propagating along the cold pool and should have a
linear mode by the time they enter this neck of the woods. They`ll
primarily pose a wind threat. Sure enough, the new Day 2
convective outlook has expanded southeast to include Norfolk,
Omaha, and Lincoln.
Some areas will achieve their warmest temps of the week on
Wednesday while areas just north will be cooler. Expect a range of
near 80 north to near 90 south... with the gradient dependent on
the front`s location. Determinstic forecast highs for Wednesday in
Lincoln and Omaha have been inching up for the past 36 hours.
Worth noting, though, is the wide spread in ensemble temps. Get
this: Wednesday has a greater percentage of members hitting 88F
at Omaha than on Tuesday. At the same time, Tuesday has more
members than Wednesday hitting 87F at the same location. It`s all
riding on that front`s placement.
Those temps certainly matter for Wednesday as low-level lapse
rates will climb due to some mid-level cooling. Expect some
convection along both the warm and cold front with Wednesday`s
shortwave working west to east. The bulk of mid-level
frontogenesis will be in South Dakota and Minnesota. But if the
front were to have trouble pushing north, the threat for severe
weather would be displaced into the heart of OAX.
A marginal threat of heavy rain and flash flooding has been
progged for the northern portions of eastern Nebraska / northern
Iowa on Tuesday night and Wednesday with PWATs running in the
90th percentile with values nearing 2.0". I`m sure some of the
farmers in this area would take their chances with the heavy
rains as the drought`s greatest impacts overlap this region.
Thursday will be cooler in the system`s wake as heights fall and
850 temps lose about 10C. As we head into the weekend, the western
ridge remains strong and may expand north and east. Regularly
ejecting shortwaves riding the ridge will work to try to keep it
at bay, but ensembles suggest it may be futile as the threat of
warmer weather increases with time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 610 PM CDT Mon Jul 12 2021
There is some smoke around, mostly aloft, and that probably will
not have a huge impact on aviation. Should see VFR conditions
through the period.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Nicolaisen
AVIATION...Miller
For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php
Area Forecast Discussion
National Weather Service Las Vegas NV
745 PM PDT Mon Jul 12 2021
.SYNOPSIS...As the major heat wave wanes, monsoon storms will
increase across parts of southeast Nevada, northwest Arizona and far
eastern San Bernardino County tonight and again Tuesday night. Gusty
winds and heavy rain leading to flash flooding are the primary
concerns. Conditions are forecast to dry out by late in the week but
monsoon moisture looks to return to northwest Arizona and parts of
the Mojave Desert Sunday and Monday.
&&
.UPDATE...Best thunderstorm activity this evening has been mainly
over Lincoln and Nye counties, which have been slowly drifting
southeast. The question through the rest of the evening will be if
the current storms persist into the over night or if they dissipate
quickly. The area south of the current activity in Clark and Mohave
counties did currently show decent MUCAPEs and high moisture, which
would be a decent environment for convection to continue, but now
CIN was beginning to increase through that region as well. Some of
the HI-Res models show at least isolated activity continuing through
the night in Clark County and western Mohave County, with HRRR and
FV3 models being the most bullish through the first part of the
night and showing a similar situation to last night with storms
congealing in northeast Clark County. While that may be a bit
overdone given the general trend of things now, leaning towards less
convection than last night but still some thunderstorms around
through at least the first part of the night. HREF continues to show
MUCAPE at 500-1000 J/Kg through the overnight hours and PWATs are
very high, so with any possible outflow from storms dying to the
north we could still see some additional storms. With PWATs over 1
inch over much of the region, heavy rain is possible with isolated
flooding concerns where storms congeal and stall.
Today should be the last day for extreme heat for southeast Nevada,
eastern San Bernardino County, and Mohave County as moisture
continues to push into the region. Temperatures will be lower
tomorrow and heat risk decreases for these areas, so will let the
excessive heat warning expire. One more day of high heat risk is
likely further to the west as moisture will be lacking and the high
will still be centered overhead, so will let that continue through
Tuesday.
&&
.PREVIOUS DISCUSSION...300 PM PDT Mon Jul 12 2021
.DISCUSSION...Anticipating an active evening and again tomorrow
evening with gusty winds and heavy rainfall being the primary
concern. Recent burn areas in Mohave County will be very susceptible
to flash flooding and debris flows Tuesday night.
Center of mid-level ridge forecast to lies across southern
California the next two days. Area of broad divergence aloft is
forecast along the northeast/eastern quadrant of the high across
southern Nevada, northwest Arizona and the lower Colorado River
Valley. SPC HREF has been consistent showing thunderstorms and
associated outflow surging south across Clark County southward into
the Lake Mead Natl Rec Area and western Mohave County late this
evening. Main concern tonight looks to be gusty winds with localized
heavy rainfall. Similar setup for Tuesday evening into Wednesday
morning. However, this time both gusty winds and heavy rainfall are
the concern as storms surge south all the way through the lower
Colorado River Valley and southern Mohave County. Hourly rainfall
rates of 1 to 1.5 inches are possible Tuesday night. Collaborated a
Flash Flood Watch with surrounding offices with ours running from 2
pm Tuesday - 5 am Wednesday morning.
Our major heatwave will continue across the western zones through
Tuesday while most area will be allowed to end later this evening.
Temperatures will continue to drop on Wednesday with highs closer
to what we would expect this time of year. Moisture lingers
and showers and storms continue across mainly Lincoln and Mohave
counties.
Heat will moderate from mid week through the weekend with no
additional heat headlines anticipated.
On Thursday, high pressure ridging is suppressed with weak
troughing setting up near the west coast. Seasonal temperatures
will continue through the weekend with the deeper moisture
shifting eastward and focusing any remaining storm chances over
or near eastern Mohave County. The Four Corners high rebuilds
sometime over the weekend and storm chances expand west across
much of Mohave County on Sunday.
&&
.AVIATION...For McCarran...Southeast winds are expected this
afternoon with occasional gusts to around 15-20 knots. There is
still a potential of storms developing in and around the Las Vegas
Valley this evening bringing erratic and gusty outflow winds. Also,
there is still the potential of outflow winds moving in from
northeast and northwest with storms that develop to the north. Low
confidence on magnitude of these outflow winds at this time. If
outflow winds do develop there is still the potential they could
exceed 35 knots, again low confidence however. Cloud bases with
convection will range from 7-10kft AGL. Storm chances decrease by 10-
12Z overnight tonight. Another round of storms are possible again
tomorrow, initially developing along the higher terrain in the
afternoon with a similar wind threat in the evening.
For the rest of southern Nevada, northwest Arizona and southeast
California...Generally light winds are expected across most TAF
sites through this afternoon. Storms will be possible near KBIH
through this afternoon, with potentially erratic and gusty outflows
to around 30-40 knots. Slight chance for storms moving through Clark
and Mohave Counties to make it to KIFP and KEED overnight tonight.
If storms do develop down the Colorado River Valley TAF sites, gusts
to around 25-35 knots are possible. Cloud bases with convection will
range from 7-10kft AGL. Storm chances decrease from north to south
10-12Z overnight tonight. However, there`s a non-zero chance of
storms near KDAG early Tuesday between 11-14Z. Another round of
storms are possible again tomorrow, initially developing along the
higher terrain in the afternoon with a similar wind threat in the
evening.
&&
.CLIMATE...Listed below are a few climate locations showing both the
record high maximum and high minimum temperature for each location and
the year the record was last set for Monday and Tuesday.
LOCATION MON-JULY 12 TUE-JULY 13
(HIGH MAX) Record(year) Record(year)
Las Vegas NV 114(2003) 115(1939)
Bishop CA 108(2020) 107(2020)
Barstow CA 115(2020) 115(1972)
Needles CA 124(1925) 123(2005)
Kingman AZ 111(2020) 110(2005)
Desert Rock NV 111(2020) 111(2014)
Death Valley CA 130(1913) 131(1913)
LOCATION MON-JULY 12 TUE-JULY 13
(HIGH MIN) Record(year) Record(year)
Las Vegas NV 94(2020) 93(2020)
Bishop CA 69(1990) 68(2002)
Barstow CA 87(2012) 84(2020)
Needles CA 92(2019) 95(2020)
Kingman AZ 83(1925) 83(2007)
Desert Rock NV 81(2003) 89(2020)
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Nickerson
DISCUSSION...Pierce
AVIATION...Peters
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