Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/09/21
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
515 PM MDT Sun Aug 8 2021
.AVIATION...
00Z TAF CYCLE
Areas of smoke continue to be the main concern through the TAF
period. Models indicate that visibility due to smoke should
generally, albeit slowly, improve overnight. However, some areas of
MVFR vsby will likely persist through 18Z Mon, especially near the
CO border. Vsby will improve in the aftn, but haze will likely
persist. Additionally, isolated showers and thunderstorms may return
to the southwest and south central mountains during the afternoon.
Coverage will be limited due to continued dry air.
34
&&
.PREV DISCUSSION...315 PM MDT Sun Aug 8 2021...
.SYNOPSIS...
An unseasonably dry and warm air mass will persist over northern and
central New Mexico through Monday and into Tuesday before moisture
increases and high temperatures retreat to near normal values by the
end of this week. Any storms that do develop will favor the
southwest and south central high terrain through Monday, while near
record highs will be possible over portions of the northern half of
New Mexico. Smoke and haze will also continue to be noticeable early
this week then slowly improve as westerly winds aloft diminish.
Showers and storms will gradually expand over the region mid to late
week. At the same time, high temperatures will cool a bit to near
normal readings.
&&
.DISCUSSION...
SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)...
The upper high to the south will build back north over our area
through Monday, bringing 500mb heights back up to 593dam and
continuing the warming trend with above normal temperatures forecast
areawide. Daily record highs will be challenged Monday at several
central and northern NM locales. Reduced visibility due to smoke
from western wildfires will continue across the area, but gradual
improvement is expected and this trend is modeled in the latest HRRR
smoke output. Isolated showers and storms are possible this
afternoon/evening across the southwest and south central mountains,
but should increase in coverage and expand slightly further north
Monday afternoon/evening as moisture creeps north under the upper
high circulation. The main threat associated with these slow moving
storms will be strong/erratic wind gusts.
11
LONG TERM...(TUESDAY THROUGH SUNDAY)...
The westerly winds aloft which have sent the monsoon on a short
lived vacation and brought wildfire smoke and haze to the region
will be weakening and trending more southerly by Tuesday. Slowly but
surely the upper high will regain it`s dominance as it transitions
from southeast of NM back to the Great Basin and possibly over the
central Rockies this weekend. A disturbance associated with the more
substantial plume of moisture will pass over AZ Tuesday but some
moisture will start to leak into western NM. Moisture will continue
to seep into NM mid to late this week as the upper high shifts
northward. In addition, storm motions will become slower and trend
from east to west. Kept the mention of the potential for a few dry
storms over the northwest and north central Tuesday, thereafter
storms should become wetter as the week progresses. High
temperatures will cool down a bit from Monday`s near record highs
over portions of northern NM to near normal values by Friday and may
even be a few degrees cooler than average this Saturday and Sunday.
&&
.FIRE WEATHER...
Hot, dry and unstable conditions will persist across northern New
Mexico into Tuesday, with decreasing wind as the upper high moves
north over the area. Moisture will increase across the forecast area
from mid to late week as the upper high relocates to over the Great
Basin, causing chances for wetting storms to trend up and
temperatures to trend back down closer to normal. Good chances for
wetting storms will then persist into the weekend as the upper high
remains north and west of the area.
11
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service La Crosse WI
1056 PM CDT Sun Aug 8 2021
.SHORT TERM...(This evening through Monday night)
Issued at 230 PM CDT Sun Aug 8 2021
Currently watching a couple of short wave troughs working across
the region this afternoon. The first was swinging northeast out of
eastern Iowa with the second coming in from southwest Minnesota. A
band of showers and a few storms have developed out ahead of the
first short wave trough and this should continue to gradually
increase through the afternoon into the early evening. MLCAPE pool
was building out over eastern Wisconsin and extending back through
the Interstate 94 corridor where the RAP suggests this could get
to around 1500 J/kg. Shear remains pretty weak, only around 20
knots effective as of now with the RAP suggesting this could get
up to around 25 knots in the 0-3 km layer. This will likely be
enough to support a few strong storms over portions of Wisconsin.
If the shear upticks slightly, a couple severe storms could be
possible with some wind and hail possible. Some increase in the
0-1 km shear noted by early evening but this may not be phased
with the convective activity and could occur behind the main area
of convection.
The second wave looks to move across the area this evening and
overnight as the main upper level works its way slowly
east/northeast across the region. This wave looks like it should
have about 500 J/kg of MLCAPE to work with, mainly across
northeast Iowa, along with maybe 30 or so knots of 0-3 km shear.
Again, this should be sufficient to produce some additional
showers and storms this evening and overnight for spots along and
south of Interstate 90. Again, maybe enough there to support a
stronger storm or two.
Some of this overnight activity could still be lingering over
portions of southwest into central Wisconsin Monday morning but it
will be on its way out with a short lived drying trend expected to
spread over the area Monday afternoon and night.
.LONG TERM...(Tuesday through Sunday)
Issued at 230 PM CDT Sun Aug 8 2021
Our next source of energy originates in a closed upper- level low
barreling east across the Northern Plains on Tuesday. As it
returns to it`s parent shortwave trough over Manitoba in the
afternoon, the equatorward entrance region of it`s downstream jet
maxima passes over our forecast area providing a favorable region
for ascent. With this current track of the upper-level forcing, an
accompanying warm front is expected to track through WI during
the day on Tuesday bringing mid 70 dewpoints with it. Besides heat
indices into the upper 90s, this warm/humid air mass will provide
ample instability with SBCAPE/MLCAPE values >3500 J/kg. While
maximum 0-6km shear values of >50kts continue to remain post
cold frontal, 0-3km shear values >45kts persevere in the warm
sector. Therefore, severe storms are possible with damaging winds
and large hail as the primary hazards. The SPC day 3 categorical
outlook has a slight risk for most of our WI counties with
marginal for our counties in IA and MN.
After Tuesday the pattern becomes less active with the longwave
upper level trough axis eventually scooting across the Great Lakes
Thursday into Friday. Behind the longwave trough, northwest flow
aloft returns from a building Rocky Mountain ridge. Mid 60
dewpoints scoot with it, introducing milder temperatures later in
the week into the weekend. The next shortwave upper-level
disturbance appears later in the weekend, however currently
lacking on temporal and spatial resolution surrounding this
possibility.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1056 PM CDT Sun Aug 8 2021
Main taf concern is thunder potential at both taf sites early in the
taf period...then potential IFR visibility conditions at RST taf
site. Upper level disturbance moving across northeast Iowa will
continue to spread showers and a few storms into southern Minnesota
and southwest Wisconsin early in the taf period. Have introduced
showers at LSE taf site. Coverage of storms will be scattered...have
kept mention of vicinity of thunder at both taf sites through the
nighttime hours. Upper level disturbance tracks east of RST taf
site by 10z Monday. With skies clearing behind the upper level
disturbance...fog will form and reduce visibilities into IFR
potentially by 10z. VFR conditions are expected at both taf sites
by 18z Monday.
&&
.HYDROLOGY...
Issued at 230 PM CDT Sun Aug 8 2021
Warm cloud depths remain in the 3.5-4 km range over Wisconsin this
afternoon with precipitable water amounts of 1.75 to 2 inches. The
ongoing convection looks to have very efficient rates approaching
2 inches an hour, but fortunately, it is very progressive limiting
the amount of rain over any one given location. Given that some
locations in western and central Wisconsin already have saturated
ground, will not make any changes to the ongoing flash flood watch
at this time.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch until 1 AM CDT Monday for WIZ029-032>034-
041>044-053>055.
MN...None.
IA...None.
&&
$$
SHORT TERM...04
LONG TERM...JAR
AVIATION...DTJ
HYDROLOGY...04
Area Forecast Discussion
National Weather Service Bismarck ND
951 PM CDT Sun Aug 8 2021
.UPDATE...
Issued at 951 PM CDT Sun Aug 8 2021
No significant changes were made with this update. Convection is
increasing in coverage over eastern MT this evening, especially
along and behind the surface cold front which at 02 UTC extends
from about Minot to Miles City. That trend should continue over-
night as the frontal zone gradually sags southeast, with limited
bouyancy (MUCAPE from 250-500 J/kg in the frontal zone) likely
minimizing the strength of elevated updrafts. However, the low-
level thermodynamic setting will be characterized by steep lapse
rates in the residual boundary layer along with dry profiles, so
the related large DCAPE suggests gusty winds are possible despite
the likely elevated character of the convection.
UPDATE Issued at 619 PM CDT Sun Aug 8 2021
The deeply mixed, hot boundary layer has generated considerable
high-based cumulus over western ND late this afternoon, and recent
radar trends suggest some of the towers have deepened sufficiently
for precipitation production, at least aloft. Forecast soundings
suggest cloud bases are over 10,000 ft AGL, with shallow bouyancy
atop the deep boundary layer, so this activity should be rather
insignificant. GOES day cloud phase RGB imagery suggests the more
prominent updraft glaciation is taking place in the post-frontal
environment, so we have focused PoPs along/behind the front into
tonight. That generally resulted in a bit of a delay in eastward
and southward advance of precipitation chances through about 06
UTC. Otherwise, we also increased post-frontal north-northwest
wind speeds tonight and Monday with this update, especially over
southwestern ND, owing to the magnitude of cold air advection and
related low-level mass field adjustments behind the cold front.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 130 PM CDT Sun Aug 8 2021
Temperatures continue to climb this afternoon with many locations
nearing or possibly even hitting 100 degrees. Otherwise, the main
question for the short term period is in regards to thunderstorm
chances tonight and severe weather chances Monday into Monday
night.
Presently, an upper level low is positioned over the northern
Rockies. This upper low will progress eastward through the
remainder of today and tonight. The low will then lift up into
southern Saskatchewan/Manitoba and associated potent shortwave
energy will slide through the region Monday. Meanwhile, at the
surface, associated surface low pressure presently situation over
eastern Montana will slide along the ND/SD border tonight through
Monday afternoon.
RAP model analysis suggests 1500 to 2500 J/kg of MLCAPE, 0 to 6 km
bulk shear of 30 to 50 kts, and steep mid-level lapse rates of 8
to 8.5 degrees C/km. All in all, indications are that a few
supercells are not out of the question and confidence in seeing
large hail has increased a bit. In regards to winds, DCAPE values
continue to appear high in that 1000 to 1300 J/kg range. The one
concern is that RAP soundings suggest a failure of the mixed layer
to tap into the strongest winds aloft. This may inhibit some of
the worst gusts at the surface. Still, the main point remains that
large hail and very strong wind gusts are possible. Locations most
likely to see severe weather are east of Highway 83.
.LONG TERM...(Tuesday through Sunday) Issued at 130 PM CDT Sun
Aug 8 2021
There could be a few lingering showers and thunderstorms through
the day Tuesday from the prior shortwave Monday/Monday night.
Otherwise, the large majority of the extended period looks mostly
quiet with the region coming under northwest flow aloft Tuesday
through at least Friday as a west CONUS ridge builds back in. The
occasional shortwave dipping through while in northwest flow isn`t
uncommon, so wouldn`t be surprised if a few showers and
thunderstorms occur at some point, some time. Presently though, as
mentioned, models keep things dry through the workweek. Beyond
that, models diverge a bit in regards to when/if the ridge will
break down come the weekend. Forecast highs keep the region
seasonable (broadly, the upper 70s to around 90) for this time of
the year through the workweek.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 951 PM CDT Sun Aug 8 2021
Isolated to scattered showers and thunderstorms will increase in
coverage over western ND tonight and expand east into central ND
late tonight and Monday. The highest probabilities of impacts are
at KXWA tonight, and KMOT and KJMS on Monday. Otherwise, MVFR
ceilings are possible behind a cold front in northwest and north
central ND late tonight and Monday, and low-level wind shear is
likely in the south tonight ahead of that front, including at
KDIK and KBIS.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CJS
SHORT TERM...Telken
LONG TERM...Telken
AVIATION...CJS
Area Forecast Discussion
National Weather Service Denver/Boulder CO
942 PM MDT Sun Aug 8 2021
.UPDATE...
Issued at 942 PM MDT Sun Aug 8 2021
It has been a quiet afternoon and evening with mostly clear skies
over Colorado, and should be a quiet night as ridging has
continued to build ahead of the next trough, which is now moving
over the northern Rocky mountains. Persistent smoke continues to
decrease the air quality and visibility tonight and will do so
tomorrow as well. The forecast is on track with only minor updates
this evening.
&&
.SHORT TERM...(This evening through Monday)
Issued at 309 PM MDT Sun Aug 8 2021
Smoke continues to be the main impact for the region. Upper level
ridging is slowly building in with a closed low pushing into the
northern mountains creating westerly flow over the region. There
will be a slight reprieve from smoke by sunset and into the
overnight hours. However, with the upper level pattern smoke will
return Monday morning and be around into Tuesday morning at least
per the latest HRRR smoke guidance. The upper trough will continue
to progress across the Northern Mountains through the day Monday
with continued minimal moisture over the region. This will leave
the airmass quite dry with just a few high-based CU development
across the higher elevations by mid-day. High temperatures will be
only slightly warmer then today with highs in the mid to upper
90s.
.LONG TERM...(Monday night through Sunday)
Issued at 309 PM MDT Sun Aug 8 2021
A shortwave trough and cold front will move through Monday
evening, bringing with it a puff of less hot and probably somewhat
less smoky air. There`s a small chance of some weak
showers/storms with the front, but too little to mention.
The cloud band associated with the Monday evening system will
clear our area Tuesday morning. Temperatures should rebound nicely
as there will be little affect in the mid levels. There may be
enough moisture over the central mountains for some clouds, but
the chance of rain is still quite low.
For the rest of the week, we will have a pattern much like we had
about 10 days ago, with a ridge building just northwest of us
that`s elongated NW-SE. This will hold the mid level moisture
mainly south of us though there could be some northward creep with
each day`s convection. Weak shortwaves passing in the flow on the
north side of the ridge will eventually bring a weak front or two
down the east slopes, which will also help turn the low to mid
level flow a bit more north or even northeasterly by the weekend.
This will maintain a pocket of drier mid level air from the Front
Range eastward. We`ll have the usual trade off of slight cooling
but also moistening over the plains, but the warm air aloft will
likely keep the plains capped and weak or possibly north to
northeast steering winds will tend to keep the limited mountain
convection from drifting east. Even with all that, there will
likely be a gradual increase in convection starting Thursday and
continuing through the weekend. Slow storm motions could
eventually lead to a low flood risk for the new burn areas, but
there`s nothing bigger in sight at this point. With the minimal
change aloft, temperatures will still probably remain near or a
little above 90 on the plains.
As far as smoke goes, our low/mid level flow will be bringing us
air from the Pacific Northwest, northern Rockies, and southern
British Columbia once the Monday night trough passes. It remains
to be seen whether this air is cleaner or not, as fire activity
has been increasing in Washington and Oregon as it gets warmer and
drier there. It`s a pretty good bet we`ll have noticeable smoke
but how much will depend on the smoke production upstream. It will
be dry, unusually warm, and breezy in those areas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 536 PM MDT Sun Aug 8 2021
Expect ILS conditions to persist through the TAF period due to
visibility reduction by persistent smoke. We expect surface
visibility to generally stay around 5SM to 6SM, with possibly
slightly lesser slantwise visibility. Normal diurnal wind patterns
should prevail overnight with speeds up to around 10 knots. A
weak front is expected Monday evening, currently around 03Z, and
winds should shift northerly with slightly greater speeds of 10 to
15 knots. The front may help to clear out some of the surface
smoke for a little while, but for now continue to expect reduced
visibility to around 6SM and therefore ILS conditions. The
probability of convection in the vicinity of the terminals still
seems very low Monday evening and certainly too low to include in
the current TAFs, even considering the front, but some occasional
variable gusts are possible.
&&
.FIRE WEATHER...
Issued at 309 PM MDT Sun Aug 8 2021
Elevated to near-critical fire danger is expected Monday with hot
and very dry conditions. Daytime humidities Monday will bottom
out around 10% across almost all of our forecast area below 9000
feet. The windiest conditions will be north of our area, but a few
gusts from 25-30 mph will be possible over North Park. No
highlights are expected at this time but conditions will be
monitored.
Breezy conditions will continue to create increased fire danger on
Tuesday and Wednesday afternoons. The only area likely to be near
Red Flag conditions will be Grand and Jackson counties where fuels
are fairly green from recent rains. Lighter winds are expected
later this week with hot temperatures continuing. A gradual
increase in humidities is also expected.
&&
.HYDROLOGY...
Issued at 309 PM MDT Sun Aug 8 2021
There are no hydro concerns through the middle of the week.
Increasing moisture will lead to a gradual increase in
thunderstorm activity mainly over the mountains starting Thursday.
Storms that develop will be slow moving, but initially will have
limited strength and moisture availability. A low risk of flash
flooding in the new burn areas will eventually develop by next
weekend. At this point it appears this threat will remain limited
as a ridge of high pressure in the middle atmosphere will remain
over Colorado.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...EJD
SHORT TERM...Bowen
LONG TERM...Gimmestad
AVIATION...EJD
FIRE WEATHER...Bowen/Gimmestad
HYDROLOGY...Gimmestad
Area Forecast Discussion
National Weather Service Cheyenne WY
526 PM MDT Sun Aug 8 2021
.SHORT TERM...(This afternoon and evening)
Issued at 215 PM MDT Sun Aug 8 2021
Ongoing high pressure influence over the region continue this
afternoon and expected through the evening as low level of smoke
and haze continue across the region. Temperatures this afternoon
reaching into the 90s across the Panhandle and portions of the WY
high plains as other places across southeastern WY reaching from
the middle 70s into the upper 80s. With influence of high
pressure, not expecting any precipitation today. Similar to
previous forecast HRRR Near-Surface Smoke continues the smoke and
haze albeit not as dense seen earlier in the weekend.
Dry conditions for many this afternoon with min RHs dropping into
the low double digits and teens though winds at majority of
sensors remain below criteria for fire weather concerns today
though Red Flag Warnings were upgraded for Monday. Expect lows
tonight from the middle 40s to upper 50s for many.
.LONG TERM...(Monday through Saturday)
Issued at 200 AM MDT Sun Aug 8 2021
Winds increase Monday as an upper low tracks across Montana and
associated surface front begins to move into northern Wyoming. GFS
700mb winds increase to 30-35kts across Carbon and Albany Counties
as they usually do in this weather pattern. Looks like we are
going to see critical fire weather conditions for the lower
elevations of southwest Carbon County and most of Albany County
with late morning through afternoon wind gusts to 35 mph. Decided
to issue a Fire Weather Watch for Monday for the Laramie valley
and southwest Carbon County to account for these winds and low
humidity.
Could be another critical fire weather day Tuesday as 700mb winds
remain elevated. Upper low slowly tracks into western North
Dakota Tuesday morning and we begin to see 700mb winds begin to
ease during the afternoon and evening hours.
Looks like a dry week ahead as we stay in upper northwest flow.
Upper ridge remains across Idaho with lower level southeast flow
east of the Laramie Range.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 521 PM MDT Sun Aug 8 2021
Wyoming TAFS...VFR at Rawlins until 02Z, then MVFR until 06Z, then
IFR until 16Z, then MVFR. Wind gusts to 25 knots until 02Z, then
to 28 knots after 16Z Monday.
VFR at Laramie and Cheyenne until 05Z to 08Z, then MVFR until 15Z,
then VFR. Wind gusts to 22 knots until 02Z, then to 25 knots after
15Z Monday.
Nebraska TAFS...VFR at Chadron until 04Z, then MVFR.
VFR at Alliance and Sidney. Wind gusts to 22 knots after 15Z
Monday.
VFR at Scottsbluff until 02Z, then MVFR until 15Z, then VFR.
&&
.FIRE WEATHER...
Issued at 159 PM MDT Sun Aug 8 2021
Near to critical min RHs across the region today as overall winds
will remain near but just shy of criteria. Upgraded FWZ 304 and
308 to Red Flag Warning for Monday for gusty winds and low RHs.
Elevated to near-critical fire weather conditions will also be
present for the southern portion of FWZ 310 and 313 as min RHs
will drop into the low to middle teens with an hour or so of near
criteria gusty winds. Otherwise dry conditions to persist through
the week though winds are forecast to remain below criteria.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from 11 AM to 8 PM MDT Monday for WYZ304-308.
NE...None.
&&
$$
SHORT TERM...WM
LONG TERM...GCC
AVIATION...RUBIN
FIRE WEATHER...WM
Area Forecast Discussion
National Weather Service Grand Junction CO
533 PM MDT Sun Aug 8 2021
.SHORT TERM...(Tonight through Monday night)
Issued at 208 PM MDT Sun Aug 8 2021
Wish there was some good news in the forecast with regards to the
dense smoke but that doesn`t look to happen. The smoke from the
wildfires out west lingers and latest HRRR guidance is showing an
increase in denseness from this afternoon through tomorrow morning
and possibly beyond. The only good news is that high temperatures
have remained several degrees cooler than forecast due to the
smoke. A few gusty winds are expected this afternoon with mostly
clear skies (if you can see it).
A trough can be seen to our northwest and will move across areas
to our north tomorrow. As it moves through, the pressure gradient
will tighten and bring some gusty west winds to the northern
valleys in the afternoon. Some localized critical fire weather
conditions are possible but forecast gusty winds over the last few
days have been diminished due to the smoke. The smoke will
continue tomorrow and so anticipate the winds are a bit
overforecast. Previous thinking still holds that persistence and
coverage will not be enough to warrant any fire weather
highlights so will not issue anything with this afternoon`s
package. The trough may bring a quick shower/storm to the eastern
Uintahs in the afternoon but outside of that area, partly cloudy
and smoky conditions remain.
.LONG TERM...(Tuesday through Sunday)
Issued at 208 PM MDT Sun Aug 8 2021
Our CWA will be on the fringe of a deep trough that will be
centered over the central Plains. High pressure will start setting
up though it will be very disjointed to start with. Monsoonal
moisture will continue to stream up from the south but the higher
pressure over us will keep the heavier precip over AZ and NM. NBM
does highlight a few showers/storms over the San Juans and this
seems reasonable. The area of high pressure becomes more well-
defined Wednesday onwards. The northerly push of monsoonal
moisture continues but guidance continues to show most precip
confined to our southerly neighbors. By Thursday, various
disturbances will impinge on the area of high pressure and start
to deform it while shifting it eastward. As this occurs, precip
chances will look more likely for the San Juans and areas south
Thursday onwards. As of now, the really big push of monsoonal
moisture doesn`t look to occur until Sunday into the next work
week. Heading into the weekend, shower and storm coverage will
increase from south to north. Since we are talking 6 to 7 days
out, still plenty of time for this forecast to change as subtle
movements of the high could increase or decrease precip amounts
for our area. We`ll certainly be watching future trends.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 530 PM MDT Sun Aug 8 2021
Smoke from western wildfires will continue to be the main focus
regarding visibilities during the next 24 hours based on the
latest HRRR smoke transport forecasts. Expect MVFR visibility at
most TAF sites through Monday. In addition, a shortwave will move
east across the northern Rockies on Monday which will result in
gusty afternoon winds over most TAF sites.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...JDC
LONG TERM...TGR
AVIATION...MPM
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
918 PM EDT Sun Aug 8 2021
.SYNOPSIS...
Slow moving showers and storms with locally heavy rainfall will
wane this evening as a front lingers over the region. Onshore
flow gives us a cool and mostly cloudy Monday, then the trend
will be toward heat and humidity through the balance of the work
week. Although shower chances exist each day this week,
likelihood of widespread showers and storms increases through
the second half of the week, culminating in a frontal passage
late in the week. This should bring an end to this latest bout
of heat with a Canadian airmass invading the region next
weekend.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
918 PM Update: Boosted near term/overnight temperatures and
dewpoints in line with late evening observational and GFS LAMP
trends. Otherwise...only minor adjustments to PoPs/cloud cover
given the evolution of slow moving convection which continues to
weaken as of this hour. Blended recent NARRE-TL and HRRR
guidance to earlier fog forecast which looks initially to
develop PSM-PWM and then later along the midcoast. This is in
line with what looks to be the initial stratus/fog development
on nighttime microphysics imagery from GOES 16 just east of PWM.
Some fog already evident at EEN/AFN where earlier rains have
fallen. No other significant changes to the forecast at this
time.
620 PM Update: Going forecast in very good shape as convective
activity has translated north and east into the NH Lakes region
and the Whites with storm not very deep...but slow moving and
thus capable of dropping a quick 1-2" of rain. Other than some
minor tweaks to align with current conditions no significant
changes at this time looking ahead to the overnight. Watching
for stratus/fog development as mentioned in the afternoon
discussion...but still expect that we have a few more hours
until this becomes an issue.
Previous discussion below...
Warm and muggy today with weak flow through the column... which
is leading to autoconvective rain showers over the mountains,
where elevated heating is providing some UVV over the peaks and
ridges amid a dearth of dynamic forcing. At this hour, activity
is mostly centered across the Monadnock region... along a weak
remnant boundary draped across New England. This activity will
gradually propagate northward through the remainder of the
afternoon and evening before dissipating with the setting sun.
Very slow storm movement due to almost no flow is leading to
locally heavy rainfall totals, so a very localized flood threat
persists through the evening.
High pressure builds over the Canadian maritimes with an
inverted ridge axis building down the Maine coast tonight. This
will set up mostly along-shore flow at the surface, but
slightly onshore with Ekman flow and a more easterly component
just off the surface. Thus the forecast conundrum for tonight
will be how the marine layer behaves with respect to fog and
stratus development. There has been consistent fog and stratus
development around Nova Scotia over the last couple days, but
there is some question with how much of that airmass we can
advect in given a greater northerly component of flow. Hires
guidance is mixed, and satellite/webcams don`t show anything
right now over the waters. Do think with the humid airmass in
place we`ll at least have patchy fog over most of the area
however. Lows will again be down into the 60s tonight.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday will likely be the coolest day of the week with
temperatures hinging on cloud cover. Surface charts will show
high pressure anchored over the Gulf of Saint Lawrence
extending down through coastal Maine, however cut off low
pressure will continue to meander off the southern coast of New
England. While any morning marine stratus and fog will likely
lift during the morning hours, mid- and upper-level clouds
provide cover in the mean time. High temperatures will be most
subdued along the coast due to onshore flow (near 70), but
inland will be a bit tougher. More clouds in convergence are
expected over Maine, for a larger chunk of the day, so highs
remain in the mid-70s for the most part there. Further west into
New Hampshire, more cloud breaks and better mixing of low level
moisture lends confidence to readings closer to 80... and over
in the Connecticut River Valley, highs are progged in the mid-
80s as it stays sheltered from the marine layer. A few showers
will be possible across the far south associated with the cut-
off low and over the northern mountains associated with a weak
upper level wave.
Another surge of onshore flow late in the day provides greater
confidence in more fog impacts along the coast, coming at the
nose of a weak jet along the northern periphery of the cut-off
low as it drifts ENEward. Caveats remain however and hires
guidance including the HREF still suggest a fairly transient
period of locally dense fog, which may also be accompanied by
light rain showers and perhaps drizzle. Overall I think tomorrow
will have the better chance of activating the marine layer than
tonight. The soupy airmass remains so I still think we`ll have
fairly widespread patchy fog over the region, but with more
coverage along the coast.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Hot and Humid Conditions Expected Wednesday Through Friday...
General pattern in the extended will consist of a
sprawling Bermuda High along the Eastern Seaboard midweek through
Friday. This will lead to well above average temperatures with
elevated heat index values. Relief is expected by the weekend as a
500mb trough approaches from Quebec on Saturday leading to cooler
and less humid conditions for next weekend. Forecast confidence is
above average in regards to the general synoptic flow.
Tuesday a weak coastal low moves through the Gulf of Maine. This
will keep the coastal plain in the marine layer for post of the day
as temperatures begin to trend up across interior areas as southerly
return flow brings to impact the area. A few scattered showers
and isolated thunderstorms can`t be ruled out. Southwest flow
becomes established by Wednesday across the entire CWA bringing
with it a very sticky airmass as dewpoint temps surge to near 70
degrees. The only relief will some afternoon cloud cover as
diurnal instability storms develop. Rinse and repeat will be
the forecast for Thursday and Friday with a slight trend up in
temperatures on Thursday as the possible peak in the heat, but
it could be just as hot on Friday. Broad cyclonic flow just to
our west will allow just enough instability aloft to help aid
in afternoon convection each day, with higher props the further
north and west you go. Surface cold front looks to cross the
area on Saturday with more storms, potential for severe weather
will be a good bet based on pattern recognition. A relief is
expected towards Day 7 for the end of the weekend.
&&
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
Short Term...
Summary: Onshore flow will develop tonight and continue through
Monday and Monday night as low pressure south of New England moves
north and east into the Gulf of Maine with high pressure
remaining over Atlantic Canada.
Restrictions: VFR attm all sites...but guidance /NARRE-
TL...LAMP...HRRR/ continues to insist on the development of IFR
fog/stratus as onshore flow continues to moisten the boundary
layer tonight. Will continue to include this expectation...but
delay it some based on evening observations and latest CIG/VSBY
forecasts from the HRRR. Do expect improvement back to VFR
during the day on Monday but another round of potentially lower
CIGS/VSBYS is possible Monday night as the onshore flow
continues.
Winds: Calm/light-variable winds overnight will become
southeasterly 5-10kts for the day on Monday before diminishing again
to calm/light-variable Monday night.
Lightning: Low probability of lightning CON/LEB/HIE over the next 1-
2 hours and then no additional lightning threat through Monday
night.
LLWS: No LLWS is expected through Monday Night.
Long Term...Tuesday morning IFR conditions could linger along
the coastal plain in the marine layer and the CT River Valley
Tuesday morning before burning off. Conditions should improve to
VFR by the afternoon hours. By midweek, morning fog and
afternoon thunderstorms will be the general pattern with tempo
aviation impacts, but coastal plain TAF terminals will generally
be VFR.
&&
.MARINE...
Short Term...High pressure builds over the Canadian maritimes and
extends down into the Gulf of Maine tonight through tomorrow
providing quiet conditions over the waters with seas and winds
staying well below small craft thresholds. Fog and showers will
be possible tonight into tomorrow, with more widespread activity
of both possible late tomorrow into tomorrow night.
Long Term...Seas and waves will stay below SCA conditions in the
extended as broad ridging is expected over the coastal waters
from Wednesday through Friday after a very weak coastal wave
crosses the waters on Tuesday. A moist airmass advecting over
the Gulf could lead to periods of fog that will lower
visibilities.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM UPDATE...Arnott
Area Forecast Discussion
National Weather Service Wichita KS
1103 PM CDT Sun Aug 8 2021
.UPDATE...
Issued at 623 PM CDT Sun Aug 8 2021
Per visible satellite imagery and regional radar mosaic, isolated
to widely scattered thunderstorms are attempting to develop
across south-central and southeast Kansas. These updrafts are
developing within a zone of enhanced moisture advection and
convergence along a subtle southwest to northeast oriented
boundary. Updrafts currently appear to be struggling, probably
given the lack of large scale forcing and actually some subsidence
in wake of the upper wave moving just east of the region.
However, with an increasing low-level jet and associated
strengthening convergence/lift this evening, suspect at least a
few storms will be able to get going. Combination of strong
instability and seasonably strong deep layer shear will support
large hail and damaging winds with any storm that can form.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 316 PM CDT Sun Aug 8 2021
Forecast highlights the next 7 days:
* Thunderstorm chances this evening across southeast Kansas, and
again areawide Tuesday afternoon and beyond.
* Heat/humidity and above normal temperatures through Wednesday or
Thursday.
Tough thunderstorm forecast late this afternoon-evening across
southeast Kansas. Upper shortwave passing overhead is providing
upper support/forcing as well as cooler air aloft. When combined
with ample surface heating and rich boundary layer moisture, the
atmosphere is strongly unstable and weakly capped.
However, there is little if any apparent surface focus/trigger for
convective initiation. Modest low to mid-level warm advection and
moisture transport should persist into the evening, lending to the
potential for convective development. Trends from the last several
hours of the HRRR and RAP support a mostly dry forecast. Will
continue to monitor observational trends, and may eventually need to
remove PoPs this evening across southeast KS. All-in-all...if a
storm or two can manage to develop, the combination of instability
and deep layer shear would support severe weather.
Will still be dealing with smoke/hazy skies through Monday,
especially generally northwest of the KS Turnpike. Thinking the
only chance for near-surface smoke will be across generally the
western half of the state, where smoke concentration could be
high enough to adversely affect those with sensitivities.
Additionally, based on observations trends, thinking this smoke is
thick enough to temper afternoon temperatures a few degrees.
Otherwise, the main story is the continued heat/humidity. Building
thickness will support forecast high temperatures in the 90s to low
100s through at least Wednesday. Combination of seasonably high
dewpoints will support heat indices mostly in the 103-108 degree
range. Consequently, in collaboration with surrounding WFOs, hoisted
a heat advisory across the entire eastern half of Kansas for Monday.
Suspect this advisory will need to be extended through Tuesday, and
maybe even Wednesday, but will punt decision to later forecast
shifts given some uncertainty.
.LONG TERM...(Tuesday night through Sunday)
Issued at 316 PM CDT Sun Aug 8 2021
The next chance of thunderstorms arrives Tuesday evening-night,
especially across generally the northern half of Kansas, as an
unseasonably strong shortwave progresses along the US/Canadian
border, dragging a cold front south into the Central Plains. There
is actually some upper support and decent flow aloft associated with
this frontal zone across the region, so thunderstorm activity may
actually have some organization to it. Deterministic consensus
wobbles this weak frontal zone across the forecast area through at
least late week, which could lead to isolated to widely scattered
hit-or-miss thunderstorm chances through late week or early next
weekend.
Above normal temperatures should continue through late week,
although likely tempered some due to the frontal zone presence and
potential for some clouds/precipitation. Could be looking at a more
bonifide cool down by next weekend, as a deep upper trough digs
across the central and eastern CONUS. However, there remains some
significant model differences which increases uncertainty.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1103 PM CDT Sun Aug 8 2021
Isolated convection will remain possible until about 3 am across
the Flint Hills and southeast Kansas. Otherwise, patchy MVFR
vsbys in haze possible due to smoke, though for the most part 6sm
or greater. Marginal low level wind shear early Monday morning for
southeast Kansas. VFR conditions are expected on Monday with
diurnal cumulus across southeast Kansas.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 73 99 78 100 / 20 0 0 10
Hutchinson 72 100 76 102 / 10 0 0 20
Newton 73 98 77 100 / 20 0 0 20
ElDorado 74 97 77 98 / 20 10 0 10
Winfield-KWLD 75 98 78 99 / 20 0 0 10
Russell 68 103 74 103 / 0 0 10 20
Great Bend 68 101 74 100 / 0 0 10 20
Salina 72 102 76 102 / 0 0 10 20
McPherson 70 99 76 100 / 10 0 0 20
Coffeyville 75 95 78 96 / 30 10 0 0
Chanute 75 94 78 95 / 30 10 0 10
Iola 74 94 78 95 / 30 10 0 10
Parsons-KPPF 74 94 77 96 / 30 10 0 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon to 8 PM CDT Monday for KSZ032-033-
047>053-067>072-082-083-091>096-098>100.
&&
$$
UPDATE...ADK
SHORT TERM...ADK
LONG TERM...ADK
AVIATION...KED
Area Forecast Discussion
National Weather Service Lincoln IL
916 PM CDT Sun Aug 8 2021
.SYNOPSIS...
Issued at 212 PM CDT Sun Aug 8 2021
Showers and thunderstorms will push across central Illinois
through Monday as an upper- level disturbance pivots across
the region. Drier conditions return Tuesday and Wednesday along
with uncomfortable heat index values (98F - 108F). This will
likely summon a Heat Advisory by mid-week. The stretch of hot and
humid conditions will be relatively short-lived, however, as a
surface cold front drops through the region later in the week,
brining additional showers and thunderstorms. Very pleasant
weather arrives by next weekend.
&&
.UPDATE...
Issued at 916 PM CDT Sun Aug 8 2021
Line of showers and storms has moved east of I-57 and should be
out of the CWA soon. However, HiRes models continue to indicate
additional showers and storms developing overnight as the low
level jet fires up into central IL. Will keep pops in the area for
this and into tomorrow as the upper level system slowly moves
across the state. Current forecast does not loo bad, but will be
making some tweaks and will be sending an update shortly.
&&
.SHORT TERM...(This evening through Monday)
ISSUED AT 212 PM CDT Sun Aug 8 2021
Latest satellite trends continue to show an eroding capping
inversion across central and west central Illinois ahead of a
decaying MCV. A very moist and unstable boundary layer has evolved
this afternoon over the region, characterized by mid 70s surface
dewpoints and MLCAPE values around 2500 J/kg.
The expectations for today`s severe weather potential remain little
changed after reviewing the latest suite of hi-res models. Stronger
thunderstorms are still anticipated to arrive just prior to 21z
with the arrival of our forcing mechanism; a mid- level shortwave
trough pivoting across the Mid- Mississippi Valley. The main
limiting factor for today`s convective setup is the lack of
sufficient deep-layer shear, with the latest RAP analysis
revealing below 20 kts. This value should increase later this
afternoon as the decaying MCV and mid- level shortwave trough
approach the Illinois River Valley, but we are still looking at
less than 30 kts of deep layer shear through this convective
event. Updrafts should struggle to stay organized in such an
environment.
Nevertheless, we continue to monitor a few strong-to-severe
multicell clusters that have already developed west of the
Illinois River. Given the orientation of the shear vectors, this
activity is expected to grow upscale into a MCS/squall line as it
moves into our outlook area over the next few hours. The line
should quickly become outflow dominant as the UDCZ struggles to
stay balanced, which is once again a result of insufficient shear.
Locations west of I-55 will stand the best chance for severe
weather through this evening, with damaging downdraft winds up to
60 mph being the prime hazard. Localized heavy rainfall will also be
possible with these storms. While the global ensembles (GEFS and
ENS) do not suggest upper echelon PWATs or QPF with this
convective system, some of the hi- res models do offer localized
pockets of 1-3 inches mainly west of I-55. Shower and
thunderstorm activity should begin to wane after sunset. Despite a
healthy LLJ veering into the region around that time, we think
ongoing convection across the Ozarks will rob us of some of the
rich theta-e air needed to sustain convection. CAMs have been
supporting this over the past few runs.
The forecast for Monday is a messy one and may offer another
opportunity for severe convection. The threat at this point is
conditional, and depends on how much convective debris is leftover
from tonight. If the cap can erode quickly enough on Monday,
there will likely be a pre- existing boundary lurking. With the
mid- level shortwave still centered over northern Illinois, there
may be enough instability and forcing to ignite thunderstorms
across central Illinois.
.LONG TERM...(Tuesday through Sunday)
ISSUED AT 212 PM CDT Sun Aug 8 2021
The bigger concern heading into this week is the heat. Mid- level
heights will begin to increase behind the departing shortwave
trough late Monday evening in response to low- level warm air
advection. By Tuesday afternoon, surface temperatures will surge
near 90 degrees with dewpoints in the mid 70s. This combination of
heat and humidity will yield triple digit heat index values and
will likely summon a Heat Advisory.
By the middle-to-late stages of next week, ensemble guidance is in
excellent agreement of strong shortwave energy digging into the
Upper Great Lakes region. This will help drive a surface cold
front through the Midwest. Shower and thunderstorm activity is
anticipated ahead of this front, especially on Wednesday and
Thursday, but it`s not clear yet on whether this activity may be
severe.
Cooler and drier weather will return in the wake of frontal
passage, with the NBM offering afternoon temperatures in the lower
80s with lows near 60 throughout next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 635 PM CDT Sun Aug 8 2021
A line of showers and thunderstorms have brought LIFR ceilings to
some of the regional terminals this evening. In wake of this line,
ceilings will gradually raise into the VFR category. Latest hi-
resolution models suggest this thin line of convection will clear
the IL/IN state line by 04z/11pm, with VFR ceilings likely at all
regional terminals by that time.
Additional shower and thunderstorm activity may spread into the
region from the south overnight. Such activity would primarily
affect the SPI/DEC terminals, but could lift as far north as
PIA/BMI. If such activity develops, and confidence remains low,
then ceilings may once again lower into the MVFR/IFR category by
08z/3am. Vicinity thunder then may linger through 15z/10am at the
regional terminals.
Surface winds will blow from south to north through the TAF
period. Sustained speeds tonight of 05-10 kts with occasional
gusts to 20 kts, increasing to 10-15 kts after sunrise.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Auten
SYNOPSIS...MJA
SHORT TERM...MJA
LONG TERM...MJA
AVIATION...MJA
Area Forecast Discussion
National Weather Service Indianapolis IN
1142 PM EDT Sun Aug 8 2021
...Updated Aviation Discussion...
.Forecast Update...
Issued at 934 PM EDT Sun Aug 8 2021
Radar returns this evening show a diminishing line of showers and
Thunderstorms over eastern IL...making progress toward the Wabash
Valley. Skies were generally mostly clear across Central
Indiana...although some higher CI from the convection to the west
was beginning to arrive across the western parts of Central Indiana.
GOES16 shows the strongest part of the convection upstream over SE
MO where cooling tops were found. Surface analysis shows high
pressure still in place across the Carolinas...providing a warm and
moist southerly flow to Central Indiana. Dew point temps across the
area remained near 70.
SPC meso pages suggest a less than favorable atmosphere in place
across for convection across Central Indiana. CAPE continues to
diminish hour by hour as heating is lost. HRRR shows the line to the
west effectively falling apart upon arrival near the Wabash between
04Z-06Z. GOES16 shows warming tops associated with the line. Thus
have kept some pops near the Wabash through the first half of the
night...but trended pops lower overnight as precip is expected to
end. Kept overnight lows at or slightly warmer than the current dew
points.
With an upper trough in the area on Monday...chances for showers and
Storms will return as daytime heating begins.
&&
.Short Term...(This evening through Monday night)
Issued at 259 PM EDT Sun Aug 8 2021
A shortwave embedded in an upper trough will approach Indiana from
the west tonight. It should bring enough lift to prompt some showers
and storms given the amount of available moisture and a SSWly low
level jet of around 30 kts. Coverage and how far eastward the precip
will be able to get is somewhat uncertain during the night as
instability will drop off quickly, especially in the eastern and
central counties where models depict a quickly developing inversion.
By Monday morning, the upper trough should be entering Indiana from
the west and moving through the area, and this looks to have enough
forcing for high PoPs across the entire area at least through the
morning. With the upper trough moving slowly through the area but
plenty of warm and moist advection at the surface, could see off and
on showers and storms throughout the day. Precipitable water values
around 2 inches or above will arrive in the early morning hours on
Monday, and will make heavy rain/localized flooding a threat Monday
and into Monday night.
NAM/GFS are both showing a bit more shear than previous runs for
Monday late afternoon/evening, with bulk shear of 25 to 30 kts.
While not overly impressive, this could be enough to help storms
organize considering the abundance of forecast CAPE (well over 2000
J/kg). The best combination of shear and instability are over the
northwestern counties arriving between 18 and 21z. Low confidence on
this being surface based, though, with the potential for cloud cover
throughout the day with the trough axis overhead. Marginal risk for
the area based on the above factors seems reasonable.
Temperatures overnight should remain in the upper 60s to lower 70s
given the warm advection pattern. Monday`s highs will likely be
lower than today given the potential for cloud cover for much of the
day.
&&
.Long Term...(Tuesday through Sunday)
Issued at 259 PM EDT Sun Aug 8 2021
Central Indiana will continue to be in a sultry summer weather
pattern through at least Thursday...with an upper-level zonal flow
promoting steady heat, humidity and isolated/scattered convection...
while weak west-to-east waves passing to our north may bring
occasional higher chances of showers/storms. While highest POPs will
be in the typical afternoon/evening time frame, low chances of
showers/storms cannot be ruled out also through most AM hours...with
PWATs consistently near 2.00" offering the potential for heavy
rains. The overall lack of shear will discourage severe weather,
although a wave crossing northern Indiana Wednesday will bring the
potential for marginally severe thunderstorms across far northern
counties.
A surface trough/front will set-up across the central Plains and
upper Mid-West for the first several days of the period, providing a
decent gradient. Moist southwesterly breezes, gusting as high as 15-
20 mph most afternoons, will boost humidity to oppressive levels.
Dewpoints in at least the low to mid 70s will promote afternoon heat
indices over 100 for much of the CWA through Thursday, especially
along the Wabash Valley, and wherever scattered showers/storms do
not occur.
At least moderate confidence continues for a deepening long wave
H500 trough over southern Canada to drag a corresponding cold front
south across the region late in the work week...transitioning the
pattern back to seasonal or cooler conditions. Light northeasterly
breezes would then bring more refreshing Canadian air across the
CWA...and finally turn off the convective showers, as PWATs are now
progged to drop below 0.75" for nearly all of central Indiana by
dawn Saturday.
Temperatures will be above normal through Thursday, although the
anomalously high humidity may keep afternoon highs from reaching
95F. Readings will transition downward on Friday, before the
slightly below normal temperatures that are expected for the weekend.
&&
.Aviation...(06Z TAF Issuance)
Issued at 1141 PM EDT Sun Aug 8 2021
IMPACTS:
- Mainly VFR Conditions this TAF period
- Brief MVFR Cigs will be possible on Monday with any storm that
strikes a Taf Site
- Winds will generally be from the south at 6-12 knts.
DISCUSSION:
Mainly VFR conditions are expected. Deteriorating line of convection
west of the TAF sites is expected to continue to weaken upon
approach. Have used VCSH/VCTS for the first few hours to account
for this. The end result should me VFR CIGS and southerly winds
through the night. Any storm that does strike a TAF site may produce
brief MVFR Cigs.
An upper trough axis is expected to push across Indiana on Monday.
HRRR suggests TSRA/SHRA development through the day as this feature
passes with triggering aided by daytimes heating. Forecast soundings
show attainable convective temperatures along with pwats near 2.00
inches. Thus will expect TSRA/SHRA devlopment through the day.
Again confidence too low to include specific timing at this
point...thus time windows of VCTS have been used for now.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...Puma
Short Term...CP
Long Term...AM
Aviation...JP
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
627 PM CDT Sun Aug 8 2021
.SYNOPSIS...
Issued at 341 PM CDT Sun Aug 8 2021
H5 analysis from this morning had high pressure anchored
off the east coast of the CONUS. A trough of low pressure extended
from the Mid-Atlantic states, southeast into the Carolinas. Low
amplitude ridging extended north of the Tennessee valley into
western Ohio. Closer to the central plains, a trough of low pressure
extended from central Minnesota into central Kansas. Across the
Pacific Northwest and southwestern Canada, a tandem of closed lows
were present. The first was located over northwestern Saskatchewan,
and a second over northern Washington state. At the surface, a weak
surface low was present over west central Minnesota with a weak
frontal boundary extending south of this feature into sern Nebraska
and central Kansas. Basically, this front was a wind shift line with
southerly winds east of the front and southwesterly to westerly
winds west of the boundary. Skies were clear across western and
north central Nebraska this afternoon, however conditions were hazy
as smoke continues to roll into the area aloft from the fires in the
western CONUS. Temperatures as of 2 PM CDT ranged from 88 at Broken
Bow to 96 at Valentine.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 341 PM CDT Sun Aug 8 2021
Temperatures and the small threat for thunderstorms are the main
forecast challenges in the near term. For tonight, the shortwave
trough across northern Washington state will track into north
central Montana. South of this feature, elevated smoke and haze
from the fires in northern California will be funneled across
Idaho into Wyoming, and eventually into western Nebraska Monday
morning. Near surface smoke continues to be prevalent across
western Nebraska this afternoon per the minor visibility
restrictions at some surface reporting stations in western
Nebraska currently. That being said, will continue to mention haze
in the forecast for tonight/near surface smoke, and
tomorrow/elevated smoke as indicated in the latest HRRR 6000 AGL
smoke product. On Monday, the H5 trough will traverse northern
Montana. This feature will force a cool front into northern
portions of the panhandle Monday. South of the front, the latest
GFS and NAM solns continue to push a tongue of very warm air into
southwestern and central Nebraska Monday afternoon. The latest
MET and MAV guidance for North Platte are 101 and 104 degrees
respectively for highs Monday. Forecast soundings for North Platte
are indicative of around 102 degrees. That being said, went ahead
and trended the forecast toward the slightly warmer MAV guidance
as we tend to be warmer than guidance south of an approaching
front. As for heat headlines, the airmass immediately south of the
front is dry tomorrow with forecast dew points in the 40s to
lower 50s. With the dry airmass, this will lead to heat indexes
just under 100 degrees at peak heating. With this in mind, will
forgo any heat headlines with this forecast package. Another
concern is fire weather concerns tomorrow afternoon given the
forecast minimum RH of 15 to 20 percent in SW Nebraska. However,
winds south of the front will be light, peaking at around 15 MPH
in the afternoon, so critical fire weather conditions are not
expected ATTM. One final weather concern with the forecast Monday
is the threat for convection as the front progresses into
southwestern and central Nebraska. The inherited forecast from
overnight had a mention of isolated storms roughly east of a line
from Ogallala to Valentine late Monday afternoon/evening. Based on
the latest NAM12, GFS and 12z HRRR solns from this morning, will
continue this in the forecast with some areal modifications based
on expected frontal position Monday afternoon. As for the severe
threat, give the lack of moisture, any storms which do develop,
will be highly elevated and could produce some gusty winds.
Forecast DCAPE of around 1000 J/KG supports gusty winds INVOF
thunderstorms as well.
.LONG TERM...(Tuesday through Sunday)
Issued at 341 PM CDT Sun Aug 8 2021
Some limited relief in the heat will arrive on Tuesday behind the
front. The relief will be temporary however as another frontal
boundary will approach the area on Wednesday with highs in the mid
90s to the lower 100s expected. Later in the week there is
indications in the ECMWF and GFS solns of a developing ridge
across the western CONUS. This will spread more heat east into the
area late in the week. That being said, temperatures were trended
upward given the trends with the mid range models.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 627 PM CDT Sun Aug 8 2021
VFR is generally expected across wrn and ncntl Nebraska tonight
and Monday.
There is a slight chance, less than 20 percent, valley fog and
local IFR will develop for a few hours Monday morning. Southeast
winds have developed across ncntl Nebraska and in the Platte
Valley this evening. A change in direction to the south is
expected between midnight and 3 am tonight and this should
prevent fog from forming in these areas.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion...UPDATED
National Weather Service Louisville KY
906 PM EDT Sun Aug 8 2021
.Forecast Update...
Corrected at 906 PM EDT Sun Aug 8 2021
Upper and mid-level shortwave trough is moving ENE over the Upper
and Mid-Mississippi Valley this evening. Diurnal cu has all but
dissipated, but we do have a thin film of cirrus spreading in ahead
of convection off to the west. A north-south oriented squall line
has been pushed east across Illinois and southeastern Missouri.
Recent IR satellite trends show considerable cloud top warming in
central Illinois, but deep convection continues at the south end of
the line in Missouri. This area continues to be fed from the
southwest with higher theta-e air.
The environment downstream in Indiana and central Kentucky does not
support maintenance of the line. The 00z Nashville sounding
continues to show a modest warm nose between 700-500 mb and a huge
amount of dry air. PWATS drop off to around 1.4 inches near and east
of the Wabash Valley. CAPE is relatively weak as well, and some
SBCIN is already developing with the development of a nocturnal
inversion. By 04z, the RAP shows much stronger CIN. 04z is when the
weakening line should arrive in the far western CWA. Based on latest
radar trends, the HRRR looks too slow bringing the line into the
CWA. But the HRRR does show considerable weakening, which is
expected, as the showers and perhaps some storms push across the
western half of the forecast area between 04-08z. The much stronger
southern part of the line has the best chance to bring storms into
the CWA in our western and southwestern-most counties in KY.
&&
.Short Term...(This evening through Monday)
Issued at 300 PM EDT Sun Aug 8 2021
A healthy cu field exists this afternoon over the region looking at
vis satellite imagery. A few small showers have tried to get going
but a robust mid level cap and dry layer (depicted in AMDAR
soundings) have kept convective development at bay for the most
part. Very isolated locations may see a brief sprinkle or shower
through this evening but most will stay dry.
Tonight a mid level shortwave will approach the region bringing sct-
numerous showers/storms to the area late (after 4am). Convection
will spread east through the morning hrs providing rainfall to most
especially along and west of I-65. As the shortwave continues to
move through the region Monday afternoon, convection may continue or
redevelop over southern Indiana/central KY with some strong to
marginally severe storms possible. Soundings indicate CAPE values in
the 2000-3000 j/kg range with steep low level lapse rates and modest
0-6 km bulk shear in the 25-30 kt range. Precipitable water
values will rise to near 2 inches which is well above normal.
Altogether these parameters would indicate the potential for strong
to damaging wind gusts, hail and heavy downpours in some of the
strongest storms Monday afternoon/evening.
Temperatures for tonight will hang in the upper 60s/lower 70s for
lows. Monday`s highs will be somewhat dependent on placement/timing
of showers/storms but should range through the mid to upper 80s.
.Long Term...(Monday night through Sunday)
Issued at 245 PM EDT Sun Aug 8 2021
Chance of showers and storms will continue into Monday evening and
through the overnight hours into Tuesday morning. An upper level
trough will likely spawn convection upstream across the Mid and
Upper MS Valley during the day Monday, which will have potential to
continue eastward into our CWA where CAPE/shear gradients exist. As
a result, our western counties are under a Day 2 Marginal Risk for
severe weather with locally damaging winds and hail as the main
concerns. It should be noted that there is a lot of model
disagreement during this period so will continue to monitor closely
as new data becomes available. But for now, will continue with
chance PoPs overnight.
Broad upper level ridging will build in across the southern half of
the CONUS, displacing most of the upper level energy north of our
area for the much of the work week. But, our position on the west
side of the Atlantic High will place us under deep SW flow resulting
in hot and muggy conditions. Afternoon max temps Tuesday through
Thursday will reach into the 90s, likely surpassing convective temps
and resulting in diurnal chances of showers and storms. Atmospheric
environment will be similar to this past week with high CAPE/low
shear with chances of pulse storms with locally heavy rainfall
possible. We`ll also have to monitor heat indices for areas west of
I-65 during this stretch as dew points surge into the 70s, resulting
in apparent temperatures in the low 100s.
By Friday, a cold front is progged to sweep through the region
followed by high pressure that could lead to a dry and cooler
weekend. But given model disagreement and late period uncertainties,
will stick with model blend of chance PoPs for periods throughout
the weekend.
&&
.Aviation...(00Z TAF Issuance)
Issued at 755 PM EDT Sun Aug 8 2021
Mostly clear skies and VFR to begin this TAF period with breezy
southerly winds. Watching a line of strong thunderstorms oriented
north-south push east across Illinois and southeastern Missouri.
Environment downstream does not support maintenance of the line, so
expecting the convection to gradually weaken after 01z. Showers, and
perhaps some lingering thunder, could arrive at HNB as early as 04-
06z. Areas west of I-65 in central KY have the best shot at seeing
showers between 06-10z before the line dissipates. Additional TSRA
are likely to develop after 15-16z and could potentially impact any
of the terminals Monday afternoon and evening. Brief torrential
rainfall and locally gusty winds, along with lightning, are the
primary aviation hazards.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...EBW
Short Term...AMS
Long Term...CG
Aviation...EBW
Area Forecast Discussion
National Weather Service San Francisco Bay Area
431 PM PDT Sun Aug 8 2021
.SYNOPSIS...Seasonal temperatures are forecast Sunday and Monday as
upper level winds push most of the elevated smoke eastward toward
the Sierra. Growing high pressure by mid week will drive a gradual
warming and drying trend into next weekend.
&&
.DISCUSSION...as of 02:09 PM PDT Sunday...As an upper level low
moves inland over the State of Washington this Sunday, the wind
pattern aloft over the Bay Area becomes much more westerly.
Recently, northerly winds were advecting smoke from the fires
burning in Northern California southward toward the Bay Area,
filling much of the sky earlier this weekend. However, with the
newer wind pattern, much more of the smoke will blow away from the
Bay Area and in towards California`s Central Valley. Social media
reports on Sunday morning have been showing bluer skies around
the area, or at least for areas away from the coastal stratus.
Cloud ceilings were fairly low Sunday morning, but all of the low
clouds and patchy fog has mixed out with just stratus clouds
residing out over the Pacific Ocean. Despite the low being all the
way up in Washington and the pressure gradient fairly weak between
it and San Francisco, minor increases to the marine layer depth
can likely happen later today. Observations at both Ford Ord and
Bodega Bay area already starting to increase from 1500 to 1800
feet.
Temperatures are expected to range in the 70s and 80s for most of
the region. Isolated low 90s may be possible in traditional inland
areas near Lake Berryessa, or the East Bay, or Southern Monterey
County, but for the most part pleasant conditions all around.
Coastal areas will remain in the 60s and low 70s due to the
influence on onshore westerly flow. This typical summer time
pattern will last through Tuesday.
Euro and GEFS ensemble models are showing higher pressure begin to
form over the northeast Pacific, down the Pacific Northwest, and
over the Desert Southwest. It almost gives the impression that it
is trying to avoid the Bay Area, but an inverted trough will keep
the higher pressure mostly developing east of here. That region
of higher pressure will grow and by the end of the week form more
of a prototypical circular high pressure system with clockwise
geostrophic flow aloft. But what are the impacts to the Bay Area
of this pattern chance and what is with the oblong high pressure
shape at the start?
The main impacts for the region will mostly be in both temperature
for inland area and monitoring elevated moisture. The high pressure
will usher in a drier airmass which under sunny afternoon skies will
increase afternoon temperatures. Ensemble models are keeping the
probability for temperatures at 850 mb increase greater that 25
degrees celsius around 60 to 70 percent. But with that oblong
shape down the Rocky Mountains, the warmest temperatures will
really be for the inland most areas. West-southwest winds off the
ocean will keep the coastal areas mild through the week. But a
warming and drying trend looks likely with inland areas and higher
elevations with the best chance for 90s and even the low 100s.
Being that it is August, it is quite apparent that it is quickly
coming up on the one year anniversary of the historic lightning
event that started so many wildfires around the Bay Area and the
Central Coast. So any mention of elevated moisture will be a
sensitive topic to bring up for anyone. Yet as this high pressure
starts to form over the southwest, winds aloft will once again
turn southerly, pushing moisture northwestward. The time frame in
question will be Wednesday and Thursday. The GFS hints at
something similar to what is about to be described, but at a lower
resolution. The higher resolution NAM is showing that around 00Z
Wednesday (Tuesday evening) a narrow band of elevated levels of
CAPE between 700 to 500 mb will move northwestward up the
California Coastline. However, relative humidity with these
pressure levels at this time frame stay between 30 to 50 percent.
It is not until Thursday at 00Z (Wednesday evening) where there is
a surge of RH values greater than 70 percent. By that time, CAPE
values drop off. Despite that drop off in CAPE, it should be noted
that it keeps pockets of 50 to 150 J/kg CAPE lingering around the
East Bay Hills and North Bay Mountains. Last but not least,
modified 500 mb Total Totals (another proxy index to gain
confidence in elevated convection) has pockets of areas that
increase over 30, but mostly stay out over the ocean. Any
lingering Totals Totals over land is in the mid-to-upper 20s and
isolated 30s. For reference, last years lightning event was in the
mid-30s.
So what does all that last paragraph mean? Simply put: it will be
monitored, but there is low confidence in elevated convection
happening at this time. This event is only now moving into model
time frames that are of higher resolution to fully capture it. As
long as that instability (CAPE) remains decoupled in time from the
moisture (RH) as it currently shows, then it will be more likely
high clouds will just pass on through harmlessly. Beyond this
event, the high pressure takes a better shape over the desert
southwest toward the weekend as previously mentioned and long
range models are hinting at a second opportunity on Saturday for
another southerly movement of moisture. But that is far too out
with models being to low resolution for any confidence
whatsoever.
&&
.AVIATION...as of 04:31 PM PDT Sunday...For the 00z TAFs. Less
extensive stratus coverage over the waters compared to yesterday
afternoon. Satellite imagery shows a thin strip of low clouds near
Bodega Bay and stretching southward and expanding in width through
Monterey County. The marine layer sits at about 1,800 ft AGL per
the Fort Ord Profiler. Expecting a little later of a return of
stratus this evening compared to yesterday, though most sites are
forecast to see IFR cigs tonight through mid to late tomorrow
morning as low clouds fill back in and the marine layer possibly
deepens. A push of onshore winds has lessened some of the smoke
across the region today. The latest HRRR smoke model shows
continued improving conditions into tomorrow afternoon. Smoke
aloft may reduce slant range visibility, particularly across the
North and East Bay, through late tomorrow morning. W/NW winds this
afternoon around 10-15 kt with locally higher gusts. Winds to
diminish overnight.
Vicinity of KSFO...VFR, satellite shows low clouds over the
Peninsula and beginning to push through the Golden Gate gap.
There is a slight chance of IFR/MVFR cigs moving into the terminal
late tonight through mid tomorrow morning. It is possible the
clouds just wrap around the East Bay and into the approach but do
not fully expand into the terminal. A weak dry cold front moving
through this afternoon may bring a shift of winds out of the SW as
indicated by the HRRR and RAP models. However, have not yet seen
that manifest and have put back W/NW winds in this afternoon`s
taf for now. Will monitor observations and update as needed.
Otherwise winds around 15-20 kt this afternoon are expected before
diminishing overnight.
KSFO Bridge Approach...Similar to KSFO.
Monterey Bay...Satellite already shows low clouds pushing back
inland towards Salinas and over the Monterey Peninsula. MVFR/IFR
cigs are expected to develop shortly with IFR/LIFR conditions then
prevailing overnight and through tomorrow morning. W/NW winds this
afternoon 10-15 kt before diminishing tonight.
&&
.MARINE...as of 02:26 PM PDT Sunday...Breezy to locally gusty
northwest winds continue through the evening, with gustiest
conditions in the northern outer waters and along the coast south
of Point Arena. Additionally, gusty westerly winds are expected in
the afternoons and evenings through the Golden Gate gap and into
the Delta. These winds will generate steep waves which may be
hazardous for smaller vessels. The sea state remains dominated by
steep short period northwest waves at 7 to 9 seconds along with a
moderate period southerly swell. Winds will weaken Monday.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...SF Bay until 9 PM
SCA...Pt Arena to Pt Reyes 0-10 nm until 9 PM
&&
$$
PUBLIC FORECAST: DK
AVIATION: AS
MARINE: Lorber
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Area Forecast Discussion
National Weather Service Phoenix AZ
439 PM MST Sun Aug 8 2021
.UPDATE...Updated Aviation Discussion...
&&
.SYNOPSIS...
An area of low pressure will move towards Arizona, bringing
cooler temperatures and an increased chance of precipitation
Monday night and Tuesday. Humid conditions will persist through
the week, along with a continued threat of showers and storms.
&&
.DISCUSSION...
Clear skies prevail across much of the Desert Southwest today.
This is largely due to abundant dry air aloft as evident in the
water vapor imagery. Latest RAP streamline analysis depicts the
mid-level ridge axis draped east to west across central Arizona.
In the lower levels, dewpoints in the lower 60s persist across
much of south-central Arizona. Further southwest, latest VWP
indicates a weak gulf surge near Yuma with southerly winds up to
3k feet and dewpoints in the lower 70s. However, total PWATs have
trended downward with the SPC mesoanalysis indicating values near
1.3 inches in the Phoenix area.
With the relatively dry westerly flow, conditions generally
remain unfavorable for convection across the lower deserts. CAMs
instead are more keen on activity across southeastern Arizona,
where temperatures are a bit cooler aloft. HREF along with some
other WRFs suggest isolated storms could develop across far
southern Maricopa and western Pinal Counties this evening. Any
storms that do materialize will be capable of producing strong
wind gusts along with an outflow boundary that could generate
blowing dust further to the north and west this evening.
Models remain in good agreement an inverted trough will emerge
overnight across Sonora. Considerable cloudiness and light rain
associated with this system will likely inhibit insolation and
initially delay the buildup of instability across the lower
deserts Monday as it drifts northward into southern Arizona.
However, consensus among the CAMs is scattered convection will
develop across the higher terrain north and east of Phoenix during
the late afternoon and evening before propagating westward.
Latest HREF suggests wind gusts in excess of 50 mph will be
possible during the evening, particularly across Pinal County.
Meanwhile, the aforementioned inverted trough and associated vort
max will drift into central or southern Arizona Monday night, but
its exact track remains uncertain. Vorticity-forced ascent will
then support elevated rain chances through Monday night and even
into early Tuesday morning as far west as the Colorado River. The
strongest storms will be capable of producing heavy rainfall and
localized flash flooding.
&&
.PREVIOUS DISCUSSION...
Tuesday the deterministics show the disturbance continuing N through
the S-Cent and N AZ as NBM POPs rise to 50%. In addition an area
of elevated WPC QPF is emphasized on Tue morning for S-Cent and
SW AZ and lighter QPF elsewhere. Tue morning QPF between Tacna AZ
and Phoenix ranges from 0.1-0.4" with 0.1-0.2" favored across
most of Phoenix. Also for for Mon and Tue the WPC Days 2 and 3
EROs are "Marginal" across the area (including SE CA on Tuesday).
This means there is a 5-10% chance of rainfall exceeding flash
flood guidance within 25 miles of a point. Models support this due
to good agreement on a decent recovery of area PWAT to 1.6-2.0"
associated with the regional disturbance moving NNW and
penetrating the S flank of the UL high.
The Clusters continue to hold a decent mix of signals for
recurring storms and showers, on and off, for the later half of
the week and into the weekend. They still favor anomalous high
pressure repositioning further to the N and NW of the region which
would give easterly waves and inverted troughs in N MX continued
better access to S-Cent AZ. However there is still plenty of
uncertainty on the timing and position of any storm intrusions
into the region during that time. For now NBM POPS favor 20-40%
for the second half of the week and into the weekend with
occasional moderate amounts of WPC QPF. NBM POPs are also
maintained, on and off, into the low-mid double digits for SW AZ
and SE CA for the second half of the week and into the weekend.
Expect a moderating effect that the increase in moisture and
occasionally thick cloud cover will have on temperatures
beginning Monday when highs have a good chance to fall to below
normal. After that below normal high temperatures remain favored
through late next week with highs mostly in the low 100s and even
the upper 90s around Phoenix, and 103-109 degrees out west.
&&
.AVIATION...Updated at 2345Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
There are no major aviation weather concerns for the rest of today.
Westerly winds will persist into early evening with occasional
gusts of 18-22 kts possible. Storms currently across Pima and
southern Maricopa Counties will be capable of producing southerly
outflow winds that may progress into the Phoenix area by mid
evening shifting winds more out of the south and possibly gusting
to 20-25 kts. An easterly switch for tonight/Monday morning should
still occur, but timing in somewhat uncertain.
For Monday afternoon/evening, scattered showers and storms will
be likely across the high terrain northeast of Phoenix with a
modest possibility of a northerly outflow boundary impacting the
Phoenix area terminals in the evening. Scattered showers and maybe
an isolated thunderstorm will then become possible later Monday
evening. Wind direction is quite uncertain for the latter half of
Monday evening due to the possibility of showers in the Phoenix
area and due to potential outflows from distant storms. Mid and
high level clouds will also gradually increase on Monday with
decks lowering to 8-12K feet late Monday evening.
Southeast California/Southwest Arizona including KIPL and KBLH:
There are no major aviation weather concerns. At KIPL, southerly
to southeasterly winds will continue at speeds of 7-13 kts with
daytime gusts of 20-25 kts. At KBLH, southerly winds will
continue through the period with speeds of 12-16 kts and some
gusts of 20-25 kts possible during the daytime hours.
&&
.FIRE WEATHER...
Tuesday through Saturday:
Highs over S-cent AZ will settle a few degrees below normal and
near normal in western areas. Storm chances increase Tue with an
increasing chances for possibly locally heavier rainfall over
S-Cent AZ by Tue. RH values also remain elevated with periodic
influxes of moisture and below normal temperatures in most places.
Min RH will remain above 20-30% in all areas except for the drier
parts of SE CA where they will fall into the upper teens possibly
on Thu. Apart from thunderstorms expect mostly light, normal
diurnal wind patterns through the period.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Sawtelle
AVIATION...Rogers/AD
FIRE WEATHER...Sawtelle
Area Forecast Discussion
National Weather Service Las Vegas NV
824 PM PDT Sun Aug 8 2021
.SYNOPSIS...Hazy skies will persist through Monday, especially over
the southern Great Basin. Thunderstorm chances will return to areas
southeast of Interstate 15 Tuesday and spread to much of the region
Wednesday. After a lull late in the week, thunderstorm chances are
expected to ramp up again over the weekend. The main impacts for the
upcoming active period will be flash flooding, especially in the
higher terrain, and gusty outflow winds.
&&
.UPDATE...Satellite images and surface observations revealed that
the thicker smoke from the northern California wildfires was
blanketing the northern third of Nevada while a more diffuse haze
existed over our forecast area. A northwest flow behind a trough
brushing northern Nevada will drive some of this smoke down into
Esmeralda, central Nye and northeast Inyo counties tonight and it
should linger over those areas Monday then begin lifting to the
north Tuesday as a light southerly flow develops around and below
700mb. The latest 00Z HRRR smoke grids were populated into the
weather grids to depict these trends.
&&
.PREV DISCUSSION...
132 PM PDT Sun Aug 8 2021
.SHORT TERM...through Monday night. Early afternoon satellite loop
and surface obs showed that most of the smoke had moved away to the
northeast, with just hazy skies and moderate air quality remaining
over much of our area. Surface obs also showed very dry air along
and northwest of I-15 (dewpoints in the teens and 20s), with more
surface moisture farther southeast (dewpoints in the 40s and 50s in
Kingman and along the Colorado River from Bullhead City southward).
As low level flow shifts from southwesterly to more southerly
Monday, humidity will creep northward, with precipitable water
forecast to increase from one inch to 1.5 inches at Lake Havasu City
and from 0.75 inch to one inch at Bullhead City. This will help
thunderstorm chances spread from central Arizona into southern
Mohave county as early as Monday night, but this will only be the
beginning. More details in the long term section.
.LONG TERM...Tuesday through Sunday.
Continuing to watch the potential for monsoonal moisture and
thunderstorm chances to return to the region through next week.
There could be a few periods of higher and/or more widespread
impacts, including flash flooding and impacts from thunderstorms
such as gusty winds and lightning.
The first wave of thunderstorms is expected on Tuesday through
Wednesday. Increased moisture is noted on many models by Tuesday,
with ensembles showing higher probabilities for 1 inch+ of PWATs
through at least southern Mohave into Clark and portions of San
Bernardino counties. What makes this time period potentially more
interesting is both the GEFS and EC are showing a decent wave
moving through parts of the region Tuesday into Wednesday morning.
With moisture already in place, this wave should help initiate
convection during this time, especially through Mohave into
southern Clark County and eastern San Bernardino County. As such,
precipitation chances have increased compared to the previous
forecast for Tuesday and Wednesday.
A lull in thunderstorm activity is possible Thursday and Friday.
Moisture will remain about the same compared to earlier in the week,
in fact some moisture increases are likely through the western
Mojave Desert and Inyo County through this time period. However,
with increasing heights and temperatures aloft, this could cap the
area and limit thunderstorm development. There will still be some
thunderstorms around each afternoon, however coverage will be less
compared to Tuesday and Wednesday and potentially limited to the
higher terrain.
The weekend forecast could get active again as monsoonal moisture
will remain in place and cooling mid level temperatures should allow
for more widespread thunderstorm development.
&&
.AVIATION...For McCarran...Wind will diminish somewhat after
sunset but will remain southwesterly at about 10 kt. There will be
periods of slightly diminished visibility due to smoke during the
morning hours Monday, but MVFR conditions are not expected. South to
southwest winds are expected to continue through the day Monday,
becoming gusty to around 20 kt in the afternoon.
For the rest of southern Nevada, northwest Arizona and southeast
California...Areas of smoke continue around the area through Monday.
The terminal most impacted will be KBIH, where MVFR conditions can
be expected. Elsewhere, periods of mountain obscuration are likely,
but local vis will remain above MVFR thresholds. Wind will primarily
be from the south/southwest at most terminals with gusty wind 20-25
kts at times during the afternoon hours Monday.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Adair
SHORT TERM...Morgan
LONG TERM...Nickerson
AVIATION...Berc
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