Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/15/21
Area Forecast Discussion
National Weather Service Boise ID
836 PM MDT Sat Aug 14 2021
.DISCUSSION...Lots of smoke and a few clouds (mostly cirrus) cover
the forecast area this evening. Visibilities around the region
were in the 3 to 5 mile range at most observations sites. Little
change is expected over the next 24 hours. Winds were out of the
west to northwest at 5 to 15 mph. We will continue the excessive
heat warning, even though the smoke has kept temps down a couple
of degrees below our previous expectations. It still looks like
the smoke will be largely pushed out of the area by a system
moving in Monday and Monday night. No changes at this time.
&&
.AVIATION...Mostly MVFR with visibility restrictions due to wildfire
smoke at the surface and aloft through Sunday. Surface winds: west
to northwest 5-10 kts except 10-15 kts south and east of KBOI before
03z. Winds aloft at 10k feet MSL: northwest 10-20 kts. Hot afternoon
temperatures will increase density altitude.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Monday night...Latest indications
are that heat and smoke will continue into Monday, especially on
the Idaho side, but a cold front should end it in eastern Oregon
Monday. HRRR smoke model shows significant improvement in the
smoke immediately after the frontal passage, and although the
HRRR model goes out only through Sunday night the trend strongly
suggests that near-surface smoke will decrease greatly on the
Idaho side late Monday or Monday evening, and smoke aloft will
decrease a few hours later. Tuesday looks breezy and cooler as the
upper trough comes in. West-southwesterly flow aloft should also
continue to improve air quality. A slight chance of showers and
thunderstorms is forecast in the Idaho mountains Monday afternoon
and evening with the cold front.
LONG TERM...Tuesday through Saturday...An upper trough will
continue to dig across the Intermountain West through mid-week,
ushering in cooler temperatures and breezy winds. This system will
also generate a chance of thunderstorms over higher terrain of
southwestern Idaho on Tuesday and Wednesday. Conditions will be the
coolest on Wednesday at roughly 10-15 degrees below normal. As flow
aloft slowly turns northwesterly and then westerly, temperatures
will gradually rebound to near normal by Saturday under mostly dry
conditions.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Excessive Heat Warning until midnight MDT Sunday night
IDZ012-033.
OR...Excessive Heat Warning until midnight MDT /11 PM PDT/ Sunday
night ORZ061>064.
&&
$$
www.weather.gov/Boise
www.facebook.com/NWSBoise
www.twitter.com/NWSBoise
DISCUSSION...SP
AVIATION.....JT
PREV SHORT TERM...LC
PREV LONG TERM....AL
Area Forecast Discussion
National Weather Service Denver/Boulder CO
741 PM MDT Sat Aug 14 2021
.UPDATE...
Issued at 740 PM MDT Sat Aug 14 2021
Storm activity is increase versus the normal decrease around this
time of day. We have one wave of storms moving through the
mountains with a flash flood threat for the burn areas, while a
more significant wave of storms dropping south across southeast
Wyoming and the Nebraska panhandle. Some of these storms are
severe with very large hail of golf ball to a couple reports near
baseball sized and then one 3" diameter hail report east of
Scottsbluff, NE. The highest MLCAPE is over the northeast corner
of the state with close to 2000-2500 J/kg, and then amounts
decrease rather quickly to the south and west to just a few
hundred J/kg closer to Akron and Fort Morgan. The severe
thunderstorm watch looks good over the northeast corner with very
large hail possible from storms through about midnight, but also a
threat of severe farther west into Morgan and northern Weld
County. Even where MLCAPE was limited to <1000 j/kg, the bulk
shear was sufficient for severe storms near Cheyenne, WY.
Overall forecast has this on track, with only minor adjustments
for timing/PoPs.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 233 PM MDT Sat Aug 14 2021
Showers and storms have developed in the mountains and near the
Palmer Divide. By the late afternoon and evening, there will be
more instability which will allow for better coverage of storms
and for some to move off the mountains and foothills to the
adjacent plains. Model data hasn`t provided much help today. In
fact, the 18Z HRRR and 18Z NAM Nest have the exact opposite
solutions with how the storms will play out. The HRRR thinks
showers and storms will be confined to the mountains, foothills,
and near the Denver metro while the NAM Nest has strong storms
over the northeastern plains. A solution somewhere in-between
will likely end up verifying. Some weak convection will come off
the higher terrain with gusty winds and there will be a threat for
stronger storms over the northeast corner although the coverage
may not be as high as the NAM Nest has. The environment across the
northeast corner is ripe for severe storms if storms were to
develop there. Right now, the SPC mesoanalysis page shows a mixed
layer CAPE of up to 3,000 j/kg and bulk shear of around 50 knots
near Ogallala yielding a supercell composite of 16. So if storms
that are currently moving south of the Black Hills make it to the
northeast corner of Colorado, they could produce severe hail and
damaging wind gusts.
Storms will eventually dissipate around midnight as instability
decreases. Low temperatures will be a few degrees above normal.
Models are picking up on a shortwave trough moving into northern
Colorado tomorrow morning providing enough lift to generate isolated
showers and storms. PoPs were added to the forecast to get a mention
of precipitation in the forecast during the morning hours Sunday.
The morning cloudiness/showers will keep high temperatures down
tomorrow so the high temperatures were lowered around 3 degrees
meaning Denver should see the upper 80s instead of the low 90s. The
left over moisture will mean precipitable water values will
reach the highest values they have in a while. With some weak
instability developing by the afternoon, scattered showers and
storms will redevelop. There`s not much of a severe threat due to
the limited instability and shear. The slow moving nature of the
storms and good moisture in place will mean there will be at least
a limited threat for flash flooding in the burn areas.
.LONG TERM...(Sunday night through Saturday)
Issued at 233 PM MDT Sat Aug 14 2021
Scattered showers and thunderstorms will linger into Sunday
evening and then dissipate by midnight as the airmass stabilizes.
For Monday and Tuesday, the strong upper level high over the
Great Basin will weaken and slide southeast across the Central and
Southern Rockies. This will usher in warmer and drier air. Should
be enough moisture and instability for isolated thunderstorms
Monday. Drying continues into Tuesday with precipitable water
values falling to a half inch or less over the higher terrain.
Very little convection is expected for Tuesday. The showers and
storms that form should be limited to the higher terrain.
Southwest flow aloft will increase Wednesday ahead of an upper
level trough moving across the Pacific Northwest and Northern
Rockies. Moisture is expected to increase ahead of this trough
with scattered thunderstorms. The timing and how deep this trough
digs is still uncertain, but there should be an increase in
thunderstorms Wednesday, especially over the mountains. A cold
front should have moved through the area by Thursday, so expect
cooler temperatures. There could be another round of scattered
thunderstorms as well. It will depend where the best lift ends up.
Will keep a chance for showers and thunderstorms in the forecast for
Friday and Saturday as northwest flow aloft prevails behind the
upper level trough off to the northeast. Expect cooler temperatures
during this period with highs in the lower to mid 80s over northeast
Colorado.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 740 PM MDT Sat Aug 14 2021
We will have a few showers/weaker thunderstorms in the area
through about 05-06Z, and still looks like VCTS is an adequate
way to represent this chance. The most likely impact from these
showers and storms would be gusty winds that could reach 35 knots
if a storm were to get close enough. A shortwave trough that moves
across the area tomorrow morning could produce light rain
showers and a mid level cloud deck, but VFR conditions will
prevail. During the afternoon Sunday, there will be a chance
(Prob30) of storms again mostly after 21Z.
&&
.HYDROLOGY...
Issued at 740 PM MDT Sat Aug 14 2021
There will be slow moving storms with decent precipitable water
values so there will be at least a limited threat for flash
flooding over the burn areas. That threat should mostly end by 10
pm or so this evening. On Sunday, the morning convection will
make the forecast difficult because it may limit afternoon
instability.
Isolated showers and thunderstorms are expected over the higher
terrain Monday and Tuesday. Moisture and thunderstorm activity
will be limited so the flash flood threat for the burn areas will
be low. Moisture and thunderstorms are expected to increase
Wednesday and Thursday. If this occurs, there will be an increase
in the flash flood threat.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Barjenbruch
SHORT TERM...Danielson
LONG TERM...Meier
AVIATION...Barjenbruch
HYDROLOGY...Barjenbruch/Danielson/Meier
Area Forecast Discussion
National Weather Service Burlington VT
1017 PM EDT Sat Aug 14 2021
.SYNOPSIS...
High pressure drifting over the North Country will bring us
drier and slightly cooler weather that will last through
Tuesday morning. The weather will then turn more unsettled from
Tuesday afternoon onward once the high pressure moves to our
east and return southwesterly flow develops. Temperatures and
mugginess will increase each day through the end of the week,
along with the return of afternoon showers and thunderstorms.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 1017 PM EDT Saturday...No changes needed with this
update. Some isolated stratus over the high terrain is visible
on satellite otherwise skies are clear across the North Country.
Latest RAP MSLP analysis shows gradient beginning to slacken
therefore expect winds to continue to diminish over the next
couple hours. Still thinking some pockets of patchy valley fog
are possible. Overall, a pleasant mid August night is on tap.
Previous Discussion...A very quiet period of weather is
starting this afternoon behind this morning`s frontal passage.
In the wake of the front, expansive surface high pressure will
build in, allowing for subsidence to develop. Main forecast
challenge is potential for fog development overnight. Plenty of
moisture at the surface from this morning`s rainfall despite the
drier air mass moving overhead, and with clear skies tonight,
thinking we will see some patchy fog develop. Limiting factor
will be light sustained northwesterly flow just off the surface,
which will keep enough mixing in place to limit coverage of fog
to sheltered valleys. Overnight lows tonight will be in the
upper 40s to mid 50s...substantially cooler than the lows the
previous few nights. Conditions will also be noticeably less
muggy than our recent weather.
For Sunday, looking continued quiet and dry with persisting subsidence
under high pressure. Will just see some shallow fair- weather cumulus
clouds develop in the afternoon and highs in the low to mid 70s.
Lows Sunday night will again be in the upper 40s to mid 50s.
&&
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 344 PM EDT Saturday...Expect sunny weather with no
precipitation for another day due to dry air at all levels of the
troposphere as sprawling high pressure remains over the area.
Towards daybreak, the leading edge of a warm front will approach the
southern portions of North Country, so they should see a layer of
low clouds roll overhead. Elsewhere, only thin, high clouds may make
an appearance late. Temperatures will be near normal for mid August
with highs ranging from 75 to 80 and lows in the 50s in most
locations.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 344 PM EDT Saturday...Isolated to scattered showers and a
rumble of thunder will be mainly over the Adirondacks westward
into the St. Lawrence Valley on Tuesday. Farther east, upper-
level support for precipitation will be weaker and in the
absence of deep moisture, expect mainly dry conditions over
Vermont through the day with partly to mostly cloudy skies.
Decreasing heights will likely push eastward to work in concert
with high precipitable water (above the 90th percentile for the
date) to cause more numerous showers with moderate to heavy
rainfall to move through the whole North Country at times from
Tuesday night through Wednesday. Again cannot rule out thunder
during the daytime hours, but looks like limited instability
will be available given little cooling aloft and relatively poor
surface heating. Highs will be a few degrees above normal where
there is ample sunshine on Tuesday, with otherwise near normal
temperatures continuing through Thursday with some continued
unsettled and humid weather. As of now, it looks like the
hottest period of this upcoming warm and humid stretch will be
Friday to Saturday. On these days, heat index values could again
surpass 90 in most areas and surface based instability will
likely support thunderstorms. With rising upper level heights
expected, the threat for severe weather is low.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Through 00Z Monday...Mainly VFR through the TAF period with
clear skies and generally light winds expected. Expected
generally clear skies with only some low stratus remaining over
the high terrain. Areas of patchy fog/low stratus are possible
at KSLK, KMPV & KEFK after 08z. Anticipate periods of MVFR
visibilities with VLIFR ceilings possible. Any reductions to
visibilities/ceilings should lift by 12z with VFR through the
remainder of the period. Winds will between 5-10 kt from the
W/NW becoming light and variable overnight. Tomorrow, winds will
remain generally 10 kt or less.
Outlook...
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. Slight chance SHRA.
Tuesday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.
Wednesday: Mainly MVFR, with local VFR possible. Chance SHRA.
Wednesday Night: Mainly VFR, with areas MVFR possible. Chance
SHRA.
Thursday: Mainly MVFR, with areas VFR possible. Chance SHRA,
Slight chance TSRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Duell
NEAR TERM...Duell/LaRocca
SHORT TERM...Kutikoff
LONG TERM...Kutikoff
AVIATION...LaRocca
Area Forecast Discussion...CORRECTED
National Weather Service Billings MT
241 PM MDT Sat Aug 14 2021
.DISCUSSION...
Tonight through Sunday night...
Satellite imagery shows a broad ridge over the western CONUS and
WNW flow over our region. There is a weak shortwave in southeast
ID that is developing a cumulus field over the Beartooth/Absarokas
and there are a couple weak radar echoes popping up over the
mountains near Gardiner. Any chance of light showers or weak
t-storms will be confined to our southern mountains late this
afternoon and evening. It will otherwise be a clear and dry night.
There is also a good deal of smoke spreading eastward over our
cwa, to near Rosebud county as of mid afternoon. 18Z HRRR
certainly supports what we have been expecting: a shift to much
smokier skies for the next couple days from the numerous western
North American wildfires.
Sunday will be a bit hotter than today with the only fly in the
ointment being smoke impacts on solar radiation. In addition to
temps near 100 degrees, we will see somewhat breezy and well-
mixed W-NW winds tomorrow afternoon as surface trof shifts to
eastern MT. If the smoke cover is thick enough it could shave a
few degrees off of temps and a few mph off of wind gusts...but
based on temps we are achieving today it may not matter much. Have
upgraded our Fire Weather Watch to a Red Flag Warning, which will
cover the entire Sunday-Monday period. We will see a poor
humidity recovery Sunday night, then another hot day but with a
chance of late day t-storms (and erratic convective outflow winds)
across the region Monday. See extended discussion for details.
Otherwise, potential for diurnal t-storms on Sunday will again be
confined to our southern mountains.
JKL
Monday through Saturday...
We will start off the week with temperatures nearing the triple
digits... but finally, on the horizon, is the possibility for
widespread rain and below normal temperatures!
High pressure and downslope winds will start of the work week,
cranking temperatures back near the 100s and keeping conditions
very dry. Some decent mix-down will occur with westerly winds for
the foothills west of Billings, bringing about gusts 25-30 mph.
The red flag warning from Sunday will roll over through Monday as
well to account for these elevated fire weather conditions.
The more pleasing story revolves around a prominent upper low
swinging southeast from the Pacific Northwest and through our
area. Widespread rain is expected, though amounts vary greatly,
depending on the placement of the low. Some lightning activity is
possible, but this will be more of a strictly rain event. The cold
front will swing through Tuesday night (so Tuesday, being a pre-
frontal day, will still see temperatures in the upper 90s),
bringing in extremely cooler temperatures that will only allow for
highs to reach the 60s for much of south-central Montana, and 70s
for southeastern Montana. Northwest flow with weak, embedded
shortwaves behind it will keep below-normal temperatures in place
for the rest of the weak, albeit just not as cold as Wednesday`s
temperatures.
Oh, and don`t be surprised if those in the higher mountains see a
couple snowflakes from Wednesday`s system ;)
Vertz
&&
.AVIATION...
VFR conditions prevailing through this evening for most of the
area. Wildfire smoke will begin to impact locations west of BIL
this evening. MVFR conditions are likely after midnight for these
locations, and after sunrise Sunday for BIL. Expect reduced slant
range visibility throughout the period.
Behringer
&&
.PRELIMINARY POINT TEMP/POPS...
Sun Mon Tue Wed Thu Fri Sat
-----------------------------------------------------------
BIL 065/098 067/098 065/092 054/065 051/073 054/076 053/077
00/K 01/U 23/T 68/T 53/T 34/T 43/W
LVM 057/097 059/094 057/089 049/066 046/073 047/076 046/078
00/K 02/T 25/T 88/T 53/T 34/T 43/T
HDN 060/100 060/100 062/094 053/070 049/074 051/076 050/078
00/K 01/U 22/T 57/T 63/T 34/T 33/W
MLS 062/100 064/100 067/095 058/074 051/073 053/075 053/077
00/H 00/U 21/B 45/T 53/T 33/T 33/W
4BQ 062/099 063/098 066/096 058/076 053/071 053/075 053/077
00/K 00/U 11/B 35/T 64/T 33/T 33/W
BHK 060/099 062/099 065/097 058/079 051/072 050/075 050/077
00/H 00/U 11/B 34/T 54/T 23/T 33/W
SHR 058/097 059/096 060/092 053/070 047/071 047/074 047/076
01/K 01/U 22/T 47/T 75/T 44/T 43/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Red Flag Warning in effect from 9 AM Sunday to 9 PM MDT
Monday FOR ZONE 117.
Red Flag Warning in effect from noon Sunday to midnight MDT
Monday night FOR ZONES 123>132.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Cheyenne WY
333 PM MDT Sat Aug 14 2021
.UPDATE...
Issued at 332 PM MDT Sat Aug 14 2021
Severe Thunderstorm Watch 440 issued for the Nebraska Panhandle
today through 11 PM this evening.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 150 PM MDT Sat Aug 14 2021
Latest surface obs and satellite scanning convergence boundary
stretching across portions of southeastern WY and the NE Panhandle
with early convection across the the SD Black Hills and light echo
now over the Laramie Range. CAM guidance remains split in thinking
with the HRRR once again being the quiet outlier this afternoon
with limited convection across the Panhandle while the NAMNEST has
stayed consistent with more widespread thunderstorms from now
through late tonight. SPC continues a sliver of slight risk for
far eastern NE Panhandle with marginal including only eastern tier
of counties from Dawes south to Cheyenne.
Latest PRECIP sounding from CSU shows robust CAPE profile of over
1000 J/kg but lackluster 0-1 km shear of about 7 kts. CIN is the
kicker again today as inversions in the sounding and values into
the 150 to 200 J/kg range. So similar to yesterday, topography
will be key to help spur initiation. LLJ again could play a bit of
a spoiler tonight across the Panhandle with any remaining
convection and energy remaining. Highs today on the warmer side
from Friday into the upper 80s and low 90s for many.
Sunday will see an uptick in low and midlevel moisture coupled
with passing upper level shortwave that again will spur convection
perhaps more widespread including into SE WY. Highs near-similar
to today`s forecast.
.LONG TERM...(Monday through Friday)
Issued at 220 AM MDT Sat Aug 14 2021
Monday...With some decrease in low and mid level moisture, we should
see a decrease in late day shower and thunderstorm coverage.
Slightly cooler temperatures for most locations, notably across the
Nebraska Panhandle.
Tuesday...Even warmer temperatures as the flow aloft becomes
southwest with 700 mb temperatures near 18 Celsius. Looks like
enough low and mid level moisture for isolated to scattered late day
thunderstorms.
Wednesday...Shower and thunderstorm coverage becomes scattered to
numerous in the afternoon and evening with a monsoonal moisture
increase, and with a cold front progressing into our counties.
Somewhat cooler temperatures on tap with considerably more cloud
cover and increased precipitation chances.
Thursday...Cooler temperatures expected in the wake of a passing
shortwave trough aloft and its associated cold front. Chances for
showers and thunderstorms will likely decrease by the evening as
more stable air moves into the region.
Friday...Northwest flow aloft continues. Still looks like
isolated to scattered showers and thunderstorms possible in the
afternoon and evening with adequate low and mid level moisture.
&&
.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1117 AM MDT Sat Aug 14 2021
VFR conditions across southeast Wyoming and the Nebraska panhandle
with some clouds beginning to pop up. There are thunderstorms in
the forecast, but the location, spread, and intensity are all very
uncertain as of right now. A low level jet will impact KCDR once
again tonight into early tomorrow with gusts of 25 to 30 knots
possible.
&&
.FIRE WEATHER...
Issued at 135 PM MDT Sat Aug 14 2021
Limited fire weather conditions next few days with isolated to
scattered chances of precipitation coupled with lackluster winds
although min RHs will teeter if not go into critical conditions.
With thunderstorm chances, lightning sparked fires remain a
possibility.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...GCC
SHORT TERM...WM
LONG TERM...RUBIN
AVIATION...LK
FIRE WEATHER...WM
Area Forecast Discussion
National Weather Service Goodland KS
609 PM MDT Sat Aug 14 2021
.UPDATE...
Issued at 609 PM MDT Sat Aug 14 2021
Severe Thunderstorm Watch 440 remains in effect for most areas
along and north of Highway 36. Boundary remains over the CWA from
northwest to southeast, with a few storms trying to get going
along it, but pulse very quickly within a few radar scans and not
amounting to much. Will continue to monitor any initation along
this, but the main focus will be the cluster of storms working
south-southeast from west central Nebraska.
&&
.SHORT TERM...(This evening through Monday Night)
Issued at 141 PM MDT Sat Aug 14 2021
For the short term, an unsettled period of weather with chances for
storms in the afternoon and evening hours through the period.
Temperatures are expected to be near to slightly above average with
winds remaining roughly out of the south.
Synoptically, not too much is expected to change through the period.
At 500mb, the area will remain in roughly northwest flow though the
ridge over the Western CONUS is expected to retrograde further west
as a trough develops over the East-Central CONUS. Near the surface,
a boundary is currently located over the East-Central portion of the
Tri-State area. This boundary will push off to the east during the
day though the area will remain under an area of relatively low
pressure through Sunday. Monday, the low pressure is expected to
deepen across much of the High Plains.
For the rest of this afternoon, a bit of uncertainty remains. First,
a thunderstorm in Southwestern Nebraska has kept cloud cover over
the Eastern Portion of the area close to where the boundary is. On
top of keeping temperatures cooler in those areas, it may also
increase stability over the area and suppress storm growth. Even so,
RAP guidance suggests that there is over 2000 J/KG of both MLCAPE
and SBCAPE to go with PWATs near 1.25 to 1.5 inches. Satellite also
shows cumulus fields in the area. So while storms have not formed
yet and there is some stabilizing due to the prior convection, there
still remains plenty of ingredients for storms to form.
For this evening, more uncertainty as there are multiple solutions
depending on the boundary`s location, prior convection, and cloud
cover. The more likely solution appears to be storms fire up along
the boundary with a few isolated storms elsewhere. This would again
favor locales further east in the area as the boundary slowly moves
to the east. Storms would then continue for most of the night before
tapering off around 3am. Another solution includes storms firing up
over Eastern Colorado around sunset as a subtle shortwave moves
through. The storms would move east a bit and then decay before
midnight. The final solution I`ll mention and the more severe of the
solution is a cluster of storms developing in North Central
Nebraska that would move south during the evening. This cluster
would move into the area during the early night hours and provide
the area with the greatest chance of seeing severe weather with both
hail and wind possible. Severe weather will be possible though with
any of the solutions and favor the northern and eastern portions of
the area regardless of solution. Hail, wind, and heavy rain would be
possible with any severe storm.
Tomorrow, the morning hours may start out with some fog or showers
over the Eastern counties from the remnants of convection from the
prior day. Otherwise skies will clear to allow for mostly sunny
skies through the late morning and early afternoon hours. Highs are
forecasted to reach the upper 80`s and low 90`s. Another chance for
storms arrives during the late afternoon hours as a shortwave and
lee cyclone move into Eastern Colorado. Storms would form a few
hours before sunset and move east across the area, likely decaying
as they go. Severe storms appear unlikely at this time as effective
shear looks to be 20 kts or less though an isolated one can`t be
ruled out due to the forcing from the features and CAPE above 1000
J/KG.
Monday, a few showers may be possible, mainly south of I-70, but
otherwise partly cloudy skies across the area. Temperatures are
forecasted to remain around 90 across the area but will depend on
how much cloud cover persists from the rain the prior night. Should
storms develop later in the day, there does look to be a chance that
a few could be severe as effective shear reaches 30 kts and MLCAPE
gets above 1500 J/KG. Uncertainty remains though given the couple of
days of convection prior so will continue to monitor how the
environment evolves for Monday.
.LONG TERM...(Tuesday through Saturday)
Issued at 1241 PM MDT Sat Aug 14 2021
Upper ridging prevails at the start of the long term period, leading
to warm and dry conditions on Tuesday. The quiet weather is
short-lived however, with an upper trough exiting the Pacific
Northwest by Wednesday.
The trough closes off into a low, but guidance isn`t sure what to do
with it from that point on. One solution shows the system tracking
across the northern Plains while another gives it a more southerly
component. Either way, this disturbance will create a wetter pattern
for the region, generating chances for showers and thunderstorms
Wednesday through Saturday. A cold front can also be anticipated,
with the latest thinking being that it will begin to push through
the area on Thursday. It is too early to determine any severe
weather threat at this time.
A cooling trend is forecast through the period, with highs falling
from the upper 80s/low 90s on Tuesday and Wednesday to the low 80s
for Saturday. Low temperatures will range from the mid 50s to upper
60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 500 PM MDT Sat Aug 14 2021
VFR conditions for both terminals with SCT-BKN mid and high
clouds. KMCK will have VCTS from 03z-06z. Winds for KGLD, south-
southeast 10-15kts. Gusts to 20-25kts thru 06z Sunday and after
14z. Winds for KMCK, south-southeast 10-15kts. Gusts to 20-25kts
thru 03z Sunday and after 18z.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JN
SHORT TERM...KAK
LONG TERM...JBH
AVIATION...JN
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1110 PM EDT Sat Aug 14 2021
.UPDATE...
Issued at 1110 PM EDT SAT AUG 14 2021
Storms are still rolling across our southern and southeastern
counties tonight, though there has been a general weakening
trend. Overall, the going forecast was in good shape. Did nudge
the PoP grids some based on radar trends and recent guidance, but
this didn`t lead to any substantial changes. Updates have been
sent.
UPDATE Issued at 920 PM EDT SAT AUG 14 2021
Stubborn strong thunderstorms continue this evening across the
south. A few more are possible later this evening before the front
continues to slowly cross the area from north to south. Updated
Pops and sky cover to reflect the latest trends. Updates sent to
NDFD and web servers.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 422 PM EDT SAT AUG 14 2021
A cold front remains just to our north, running SW and into West-
Central Kentucky. Cloud cover did a good job early this afternoon
with hampering convection, but with afternoon heating and clearing,
scattered storms have developed along the SW bordering TN and in the
north from Bath and into Fleming Co. Guidance still doesn`t have the
best handle, with the HRRR much drier into the night versus a wetter
solution in the NAMNEST and similar Hi-Res guidance. Because of
this, have went chance PoPs through tonight before redevelopment
into Sunday. Theta-e surface analysis from the RAP suggests the
aforementioned front to nearly stall across the KY/OH border and
through Western Kentucky. Because of this, showers will again be
best along the front and in the south (where the better instability
lies) into the afternoon tomorrow. An upper level high continues to
sit off the Southeastern Coast, but will weaken and provide less of
an influence as heights lower through the period.
Shear continues to be very weak with CAPE peaking between 2000 and
3000 J/kg during the afternoon today and again Sunday. This is best
along our southern counties, into Central Kentucky, and down into
Tennessee. This, as well as along and ahead of the front (to our
north), is where we have seen the best convection so far today. Gulf
moisture continues to stream into the area with the aid of southerly
flow, allowing for PWATs between 1.75 and 2". Combining this with
slow storm motions, localized flooding can not be ruled out through
the period. This is also highlighted by WPCs day 1, 2, and 3
marginal outlook for Eastern Kentucky.
Sensible weather will feature river valley fog/stratus overnight
which could hamper morning visibilties periodically. Lows will be
near to slightly above average, in the mid and upper 60s. With the
front at a slow crawl southward, our far northern counties (Bath to
Rowan and north) will be the coolest for afternoon highs, in the
upper 70s. The remainder of the CWA will generally be in the lower
80s. Lows overnight Sunday will be very similar to tonight, ranging
in the mid to upper 60s.
.LONG TERM...(Monday through Saturday)
Issued at 321 PM EDT SAT AUG 14 2021
An active weather pattern is on tap for the extended. We can
expect daily chances of showers and storms, especially during peak
heating each afternoon and evening. We will have a few weather
systems influencing the weather of eastern Kentucky through out
the upcoming work week. A weak upper level trough will be in place
across the mid west, and will slowly evolve into a slow moving
closed low by mid-week. This system will provide lift for shower
and storm development. There will also be a slow moving cold front
that will be move around the region. Tropical cyclone Fred will
also be a player, as it moves northward into the Tennessee Valley
next week. The latest forecast models have Fred tracking further
and further west. The northward movement of Fred`s remnants could
act to further slow down the earlier mentioned cold front, keeping
in place for an extended period of time over or near our area.
Fred will also bring a good amount of tropical moisture into the
region. All of these factor together should make for a week of
active and wet weather. Rainfall amounts will depend largely on
how Fred evolves, the amount of moisture we get into the region,
and how much instability is available for storm formation. The
latest model soundings suggest tall and skinny CAPE profiles,
favorable for locally heavy rainfall. The latest QPF forecast was
increased to higher numbers than the newest pure WPC QPF numbers
to account for this.
Temperatures should trend cooler than normal each day due to
persistent and extensive cloud cover and precip, and a slight
intrusion of cooler air from the north. Nightly lows continue to
show a trend toward warmer than normal numbers on average.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 920 PM EDT SAT AUG 14 2021
VFR to start the 00Z TAF period. Scattered showers and
thunderstorms may result in brief flight restrictions tonight.
Patchy fog and lower ceilings (MVFR or lower) are possible
overnight into early Sunday morning. Additional showers and storms
are expected on Sunday which may result in more flight
restrictions. Winds will be light and variable overnight an N/NE 5
kts or less on Sunday.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CMF/HAS
SHORT TERM...BB
LONG TERM...AR
AVIATION...CMF
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1054 PM CDT Sat Aug 14 2021
.UPDATE...
Issued at 818 PM CDT Sat Aug 14 2021
Have removed what little PoPs we had tonight up by the Alexandria
area and now have a dry forecast for tonight. The RAP shows the h85
theta-e ridge and associated moisture transport remaining northwest
of the MPX CWA through Sunday morning. The HopWRFs and HRRR have
shifted northwest with precip for late tonight as well, so removed
what PoPs we had with support in the form of forcing or CAM
reflectivity forecasts now gone.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 255 PM CDT Sat Aug 14 2021
Not one cloud in the sky today with high pressure firmly in place.
The center of the ridge has shifted south which has allowed surface
winds to turn southerly. Despite the flow, very low dew points in
the 40s are being observed area wide thanks to the source region from
the high itself. Elevated fire weather conditions are occurring
across central Minnesota, and have approached Red Flag criteria with
gusts in the 20-25 mph range and RH values in the mid 20s.
A LLJ will develop tonight across the Plains to northern MN. Better
moisture contained within this flow will contribute to increasing
elevated CAPE. The forcing with the LLJ and the elevated instability
could lead to a few showers or thunderstorms overnight into early
Sunday across west central MN. Introduced PoPs in this area as
several CAMs indicate development. The loss of the LLJ after sunrise
will allow storms to dissipate quickly.
Elevated fire weather conditions are likely again Sunday with
continued breezy south winds, slightly warmer temperatures, and min
RH values in the 25-30 percent range.
.LONG TERM...(Monday through Saturday)
Issued at 255 PM CDT Sat Aug 14 2021
Dry, sunny weather is certain Monday and Tuesday and becoming more
likely Wednesday. Highs of 80s (and perhaps a 90 in western MN) are
forecast through Wednesday. Meanwhile, lows will rise from upper 50s
to mid 60s Monday night to mid 60s Wednesday night. Humidity is
expected to increase through mid-week as sustained southerly flow
over the central Plains (to the west of a sprawling surface high
over the Northeast) advects more moist air northward. Southerly
winds could be breezy, especially in western MN where gusts may
reach 20 knots during the afternoon. Dewpoints of mid 50s to lower
60s Monday morning will gradually rise to the low to mid 60s
Wednesday morning (with some upper 60s possible in southern MN and
western WI). Fire weather concerns will thus be reduced.
The Pacific Northwest upper-level trough that has been mentioned in
previous discussions is still forecast to eventually translate east
into the Northern Plains. However, model consensus agrees that the
trough`s arrival won`t be until at least Thursday, decreasing PoPs
Wednesday into Wednesday night. More concerning, the trough`s
evolution has become more uncertain in recent model runs. The ECMWF,
GEM, and a number of EPS and GEFS ensemble members suggest that a
portion of the trough breaks off into a cutoff low (at least
temporarily) over the western CONUS. The rephasing of the cutoff low
with the northern jetstream eventually happens but timing differs
between models. Once rephasing occurs the trough moves east into the
Northern Plains, developing a surface frontal system. This system
should sweep a cold front through MN/WI late week, but large
uncertainty when this happens exists due to the rephasing discussed
earlier. (For example, a 48-hour difference in cold front arrival in
MN is observed between the latest ECMWF and GEM.) With the greatest
chance for widespread QPF along the cold front, the timing of
greatest PoPs is in question (with later solutions suggesting Friday
into Saturday). Meanwhile, the GFS is much faster, due to keeping
the trough intact, leading to a Thursday to Friday timeframe.
Unmentioned so far is QPF as this is also dependent on whether the
MPX CWA receives a direct hit from the trough or just glancing
blows. Guidance is suggesting that at least a half inch of QPF is
likely, with northern MN having a good chance of upwards of an inch.
Hopefully, models converge on a solution relatively soon to shed
light on how much rainfall we may get. After the cold frontal
passage, temperatures will also decrease with 70s for highs possible
next weekend.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1054 PM CDT Sat Aug 14 2021
Move along, nothing to see here. Lots of one line TAFs with south
winds and clear skies expected. Enjoy!
KMSP...Winds during the afternoon will be occasionally gusty, but
changes are not enough to warrant cluttering the TAF with another
line.
/OUTLOOK FOR KMSP/
MON-WED...VFR. Wind S 10-15 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
UPDATE...MPG
SHORT TERM...Borghoff
LONG TERM...CTG
AVIATION...MPG
Area Forecast Discussion
National Weather Service San Francisco Bay Area
849 PM PDT Sat Aug 14 2021
.SYNOPSIS...As high pressure strengthens this weekend, Sunday should
be the hottest day for inland locations and higher elevations.
The weather pattern changes early next week providing the next
cooling trend for the Bay Area and Central Coast as an upper
trough tracks across NorCal.
&&
.DISCUSSION...as of 09:00 PM PDT Saturday...A lopsided synoptic
scale tug of war is underway with a broad 596dm monsoonal ridge
centered 400 miles east of the Bay Area and a weaker 586dm low
pressure disturbance focused 850 miles offshore to west. The
center point between these two features is roughly 300 miles
offshore, meaning that the broad monsoonal high pressure system is
responsible for the majority of our weather, but not all. That is,
the marine layer has been surprisingly robust this evening despite
the relatively high pressure aloft of the region. In fact, the
latest readings from the Fort Ord profiler show the marine layer
has been gradually deepening and is now around 1800 feet in depth
after depressing to below 1000 feet last night. So, what this mean
is that despite what is a very hot and dry for most across the
state, the majority of our region has been fairly seasonable and
dictated by the marine layer and robust onshore flow while only
the more remote locations of our forecast area such as Cloverdale,
Berryessa, Pinnacles, etc are experiencing the triple digit heat
much of the rest of the interior of the state is seeing today.
Otherwise, evening satellite imagery is quite dynamic and features
a number of interesting features, including a textbook tropical
hurricane system off Baja (Linda), decaying monsoonal
thunderstorms over the Sierra sending their remnants westward
towards our area this evening, omnipresent wildfire smoke, marine
stratus and even a band of tropical moisture farther offshore.
Convective models have hinted that some of these showers and
thunderstorms rolling off the Sierra in the mid level easterlies
could bring a few sprinkles to our region into the morning though
chances are rather slim. Per the smoke, air quality sensors
across the region are running in the yellow to orange range,
indicating that the stagnate air mass trapped under the high
pressure system is preventing fresher air from entraining into the
region. Unfortunately, even with the afternoon sea breezes, air
quality struggles to improve given the amount of smoke lingering
offshore waiting to be pushed inland. That said, HRRR smoke model
suggests an arriving trough later early in the work week will help
clear out the smoke and advect in fresher air.
Looking ahead, the high pressure system over the area will peak in
intensity tomorrow and very hot and dry conditions should be
anticipated across the interior regions. Essentially, areas that
were at least in the mid 80s today should expect another few
degrees of warming into tomorrow, while nearer shore areas will
see little difference. Robust onshore flow returns with tomorrow
evenings seabreeze. Interior locations just beyond our forecast
area will be flirting with record temperatures tomorrow and some
unofficial record heat along our periphery is also possible.
Needless to say, wildfire fuels are extremely dry so vigilance and
caution is advised for those choosing to spend time outdoors
tomorrow.
Then, on Monday, the aforementioned offshore disturbance and an
approaching Gulf of Alaska low will work together to suppress the
high pressure system currently stagnating over us this evening
before completely evicting it from the local region by Tuesday.
Remnants of the ridge will then spin offshore and form an eastern
Pacific high through the upcoming week while the broad 545dm low
sweeps across Canada and the upper to mid intermountain west. As
such, expect a trend towards a deeper marine layer and cooler and
wetter conditions. Confidence is rather high on this occurring
given that 5 of 5 ensemble clusters show similar scenarios playing
out between days 3 and 6 with only minor to moderate perturbations
in the low pressure intensity being different.
&&
.AVIATION...as of 6:13 PM PDT Saturday...For the 00z TAFs. An
amazingly resilient stratus and fog coverage /marine layer depth
1,600 feet/ continues despite last evening`s influx of tropical
moisture aloft; on the heels of a strong spring to summer marine
layer so far. It`s LIFR-IFR along the coast, VFR inland. The SFO-
SAC pressure gradient is 3.9 mb, satellite shows onshore winds
already ushering in stratus and fog. The WRF-ARW forecasts patchy
light coastal drizzle overnight and Sunday morning. Wildfire smoke
is limiting surface /MVFR/ and slant range visibilities.
A very focused and spatially compressed 500 mb high pressure system
retrogresses to the NorCal/NV border during 00z TAF cycle,
expectation is this will compress the marine layer tonight and
Sunday; already late we`re still waiting for the compression to
show up in the profiler data.
Vicinity of KSFO...VFR, west wind near 20 knots until mid evening.
MVFR ceiling forecast 10z-17z Sunday, stratus intrusion hinges on
the depth of the marine layer. VFR Sunday with afternoon and evening
west wind 20 knots.
KSFO Bridge Approach...Similar to KSFO.
Monterey Bay...IFR due to stratus and fog around the Monterey Bay
already making inroads into the northern Salinas Valley. VLIFR-IFR
in stratus and fog, the marine layer likely compressing tonight
and Sunday. Patchy light coastal drizzle possible overnight and
Sunday morning. Conditions improving to MVFR-VFR late Sunday
morning and afternoon.
&&
.MARINE...as of 02:10 PM PDT Saturday...Breezy north/northwest
winds persist today through Sunday. Stronger gusts will be
observed along the coast where coastal jets commonly set up (e.g.
Big Sur Coast, Point Reyes, etc). In addition, gusty westerly
winds will funnel through the Golden Gate and into the Delta
during our afternoons and evenings this weekend. These winds may
be hazardous for smaller vessels. As for the sea state, it
continues to be driven by a weak southerly swells from the
remnants of a tropical system and a northwesterly swell stemming
from a low pressure off the coast of British Columbia. Are
observing steep northwest wind waves that are typical for this
time of the year as well. Stronger northwest winds develop early
next week as the low pressure begins to approach the Pacific
Northwest.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...SF Bay until 9 PM
SCA...Pt Reyes to Pigeon Pt 0-10 nm until 9 PM
SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
&&
$$
PUBLIC FORECAST: DRP
AVIATION: Canepa
MARINE: Diaz
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Area Forecast Discussion
National Weather Service Nashville TN
1012 PM CDT Sat Aug 14 2021
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Issued an evening update to further reduce pops. Latest Hrrr
indicates that the decreasing convection trend overnight will
continue. Otw, dewpoint spreads at or below 5F. That, combined
with the usage of the fog formatter both indicate the development
of patchy fog late tonight. Will therefore maintain the inclusion
of patchy fog. Min temp forecast appears to be on track so no
other changes.
&&
.AVIATION...
00Z TAF DISCUSSION.
Scattered showers and a few storms were in Middle TN this
evening. Most of the activity was near a southward moving outflow
boundary that stretched from Centerville to Murfreesboro at 00Z.
The convection should dissipate by 03Z. Expect areas of low clouds
and some vsby restrictions to develop later tonight into early
Sunday at all terminals. Best chance for greatest impact is at
KCSV due partly to the heavy rains that fell in that area from a
late afternoon storm. The areas of low clouds and fog will burn
off by mid morning Sunday...with another round of scattered
showers and storms expected to commence early Sunday afternoon.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......21
AVIATION........Vannozzi
Area Forecast Discussion
National Weather Service Phoenix AZ
404 PM MST Sat Aug 14 2021
.UPDATE...Updated aviation discussion.
&&
.SYNOPSIS...
High levels of moisture will remain entrenched across the Desert
Southwest through the middle of the week, leading to persistent
chances for showers and thunderstorms. The primary threats with any
storms remain localized heavy rainfall that may cause flash
flooding. A Flash Flood Watch is in effect for south-central Arizona
through Sunday afternoon. Strong winds and some blowing dust will
also be possible for desert locations. With increased cloud cover
and showers, temperatures will remain below normal.
&&
.DISCUSSION...
A very moist airmass remains in place across the region today.
Mesoscale analysis shows regional PW ranging from ~1.4-1.9"+ with
the 12Z PSR sounding showing PW of 1.77" and a late morning PHX
ACARS soundings indicating a comparable mean PW of 1.8". The 12Z
sounding also featured a worked-over, more stable column with a
near moist adiabatic profile,relatively weak CAPE and moderate
CIN. Though significantly higher MUCAPE was developing midday and
back in the 1000s as shown on the RAP and ACARS, although with CAPS
also present. The UL pattern depicted pronounced E flow aloft
along the S flank of the UL ridge with the latest inverted trough
and vort max over S-E AZ with additional disturbances lined up
over S NM/W TX to the east preparing to ride the easterly flow
conveyor belt into the region. METSAT showed mostly cloudy to
patchy clear conditions as radar painted scattered showers and
thundershowers across SE-E AZ and into Pinal County SE of Phoenix.
After last night`s widespread storms dewpoints remained very high
from the upper 60s to mid 70s in the early afternoon along with
enough breaks in the clouds to produce increasing afternoon
insolation and heating around Phoenix and the lower deserts. HREF
members have divided into two camps for this afternoon and
tonight. The ARW and the HRRR favor a smaller area of storms
descending from S Gila Cty into the SE-S-Central Valley while
weakening as they enter the Valley this evening around 8-9PM MST.
In the other camp are the significantly more bullish NSSL, FV3 and
NAM NEST which favor more numerous, robust storms over a larger
area descending off the E high terrain and not weakening as much
as they cross Phoenix. The UL triggering mechanism disturbances in
place support the latter/stronger storm scenario, while the
possible lingering effects of a recently worked-over column
support the former/weaker storm scenario. In either case there
remains a good 40% NBM chance of precipitation tonight and a 50%
chance of HREF thunderstorm wind gusts of >35 mph across Phoenix
and the deserts tonight. There`s also almost a 10% HREF chance of
thunderstorm wind gusts of 60 mph tonight across the lower deserts.
The current upper level pattern changes very little on Sunday and
into the early part of the week. As a result a flash flood watch
remains in effect for the region (not including SW AZ and SE CA)
through Sunday afternoon at 5 PM MST. Temperatures today and for
the week will also change very little and remain below normal, in
the upper 90s to near 100, owing to the persisting highly humid
airmass conditions.
The Clusters family favors similar flavors of a large, weak low
pressure trough anomaly dominating the Intermountain West and N.
Rockies by the middle of the week as well as disturbances and
associated storms lifting out ahead of it across Phoenix and the
AZ area. As a result expect elevated chances of storms and
precipitation through the middle of the week.
&&
.AVIATION...Updated at 2305Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Still some potential for shower/thunderstorm activity across parts
of the Phoenix metro area this evening, with higher chances for an
outflow moving through. Still some uncertainty as to how
widespread any activity will be given that the air mass is
slightly more stable compared to yesterday. Winds from east to
northeasterly outflow are expected to arrive near or after 02Z,
with gusts of 20-30 kt possible. Otherwise, easterly winds should
persist overnight into much of Sunday morning. Expect SCT-BKN
clouds to persist mostly aoa 6 kft, though cigs could drop down
with any convection that develops over the metro later.
Southeast California/Southwest Arizona including KIPL and KBLH:
At KIPL, light winds should persist out of the east to southeast for
the bulk of the TAF period, while winds are expected to remain
southerly for KBLH. FEW-SCT clouds aoa 12 kft are expected to
persist throughout the period.
&&
.FIRE WEATHER...
Monday through Friday:
Humid conditions will continue through much of the week. The
threat of showers and thunderstorms will also continue through
midweek, followed by a drying trend and only a slight chance of
wetting rains. The strongest storms early in the week will be
capable of producing localized flash flooding, particularly in the
higher terrain north and east of Phoenix. Below normal
temperatures are also anticipated.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flash Flood Watch through Sunday afternoon for AZZ534-537>563.
CA...None.
&&
$$
DISCUSSION...Sawtelle
AVIATION...Rogers/Smith
FIRE WEATHER...Hirsch
Area Forecast Discussion
National Weather Service Pueblo CO
332 PM MDT Sat Aug 14 2021
.SHORT TERM...(This evening through Sunday)
Issued at 330 PM MDT Sat Aug 14 2021
...Showers and storms possible all locations tomorrow afternoon...
...Smoke will be increasing again during this period...
Currently...
A couple of isolated showers were noted over the region at 2 PM. A
few showers were noted along the DCVZ ()well defined in radar data)
extending from Elbert county into El Paso county. Other very
isolated showers were noted over the high terrain. Otherwise skies
were predominantly clear across the area.
Rest of today and tonight...
Water Vapor sat pix imgy shows rather very dry conditions over the
region and this will lead to a decrease of thunderstorm activity
over the region during this period. Best chance of storms will
mainly be over the mtns, especially along the CONTDVD region. Some
rain could be heavy but given entrainment of the drier air any heavy
rain should be brief. Likewise any flash flood threat will be low.
Overall a large majority of the region will be dry the rest of today
through tonight.
A review of the HRRR smoke fcst indicate smoke will be on the
increase across the region tonight, especially smoke aloft. Expect
vis to gradually decrease with time.
Temps tonight will be seasonable with mins around 60F plains and 40s
and 50s higher elevations.
Tomorrow...
Pattern will be a bit more active, and all areas will see the
potential for showers and storms. Two potential features will help
bring a better chance of precip to the area. First, flow aloft will
transition to NW and a weak wave is noted in the mid to upper
levels moving over the fcst area. The 2nd feature (not shown by ALL
guidance) is an MCV feature developing at 700 mbs developing over
the plains. Mainly the CAMS show this feature developing. Overall
expect a better chance of storms affecting all areas tomorrow,
albeit the brunt of the precip on the plains will likely occur after
this period (after 00 UTC). CAPE values are not all that high and
storms should be moving at a decent clip to the southeast, so flash
flooding should not be that great of a concern, on the other hand
the rain will be heavier that we have seen in the previous 24 hours
so the flash flood threat will be with us, albeit low.
Storms are not expected to be severe, but locally strong gusty winds
and some small hail will be possible.
Smoke will continue to increase, especially at mid level, so
anticipate hazy conditions tomorrow. /Hodanish
.LONG TERM...(Sunday night through Saturday)
Issued at 330 PM MDT Sat Aug 14 2021
...Flash Flooding could be an issue for the burn scars areas on
Monday during the afternoon and throughout the early evening,
especially for the Spring burn scar...
For Sunday night through Monday...thunderstorms that had developed
during the evening will continue overnight over some areas,
especially over the eastern plains. During the morning hours on
Monday, there will be thunderstorms possible over the far eastern
and southeast plains. Scattered thunderstorms will develop during
the late morning, mainly over the San Juans and southern Sangre de
Cristo Mountains. These storms will move out over the I-25 corridor
areas during the afternoon and evening hours. Isolated thunderstorms
will be possible over the plains, with the best chance of occurrence
over the Raton Mesa area and the southeast plains later in the
evening.
For Tuesday...a few isolated thunderstorms could develop over the
central mountains.
For Wednesday...scattered thunderstorms will develop over the
central mountains during the afternoon and over the eastern
mountains and northern plains during the evening hours. A slight
chance of severe thunderstorms over the eastern plains late evening.
For Thursday through Friday...Scattered thunderstorms will develop
throughout the afternoon over the mountains and evening over the
plains. Showers and thunderstorms will continue into the late
evening hours over the plains and into Friday morning. Some of these
storms could be severe. Isolated to scattered thunderstorms will be
more likely over the far eastern plains on Friday and there could be
severe thunderstorms during the afternoon and evening hours,
especially over Prowers and Kiowa counties. A few thunderstorms will
also be possible over the Rampart Range, Palmer Divide, and the
Raton Mesa area and could potentially become severe in these areas
as well.
Detailed discussion:
Sunday night through Monday...
There is going to be some troughing to the east of the CWA and
moisture begin advected upstream over the area at the 700-500mb
level which will produce thunderstorms initially over the mountains
and then moving out over the plains during the evening hours going
into the late Sunday evening hours. Some flash flooding could be
possible for the burn scar areas throughout the early part of the
evening, especially for the southern Sangre de Cristo Mountains, to
include the Spring burn scar. Convective models do suggest a
possible development of an MCV late tomorrow evening and going into
early Monday morning, SREF/NAM12/GFS20 are all showing a lot of
moisture hanging out during the Monday morning hours over SE
Colorado and therefore showers and thunderstorms could still be
continuing into the morning hours over the far east and southeastern
plains. There could be a slight chance of a severe thunderstorm over
Kiowa county towards the center of the MCV where there is more omega
forcing. There will be thunderstorms developing over the mountains
again, during the afternoon, with the best chances for development
along the eastern mountain ranges in the late morning hours. A few
storms could move out into the plains later in the afternoon and
evening, especially along the I-25 corridor. It will begin to
slightly cool as the northwesterly flow is persistent over most
areas with troughing to the east, with temperatures closer to the
seasonal average.
Tuesday through Wednesday...
Ridging will temporarily build back in with most of the CWA
remaining dry as the monsoonal moisture plume remains further to the
west, and only some afternoon and evening thunderstorms will be
possible over the central mountains. Temperatures will also be back
on the rebound, with anywhere from 5 to 10 degrees above the
seasonal average over most areas, especially for Wednesday, where
triple digit heat can be possible over some areas of the lower
Arkansas River Valley. By later in the day on Wednesday, troughing
is going to allow for some of the monsoonal moisture plume to be
drawn up from the southwest and there could be some more storm
development towards the north and allow for a slight chance of
severe thunderstorms to move in over the north areas of the plains
by late evening, but all depends on the timing of the boundary
interacting with the southerly moisture surge ahead of the trough.
Thursday through Friday...
Most of the ensembles and deterministic models are in relatively
good agreement with a trough and associated closed low at the 500 mb
level moving over the region late Thursday evening and going into
Friday. This could potentially be a very impactful system, with a
strong boundary that could produce severe thunderstorms over the
eastern plains of the CWA by late Thursday evening and Friday as
well. This system will need to be continued to be monitored in the
days ahead to determine when and where exactly the frontal boundary
associated with this trough will be moving over the CWA and the
timing. Along with the threat of severe weather, will also be a
reinforcement of cooler temperatures over the area, which will allow
for maximum temperatures to be slightly below the seasonal average
by Friday. Stewey
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 330 PM MDT Sat Aug 14 2021
VFR conditions are anticipated during the next 24 hours at all 3 taf
sites, KPUB, KALS and KCOS. There will an increasing chance of
thunder at all TAF site starting late tomorrow afternoon and
especially tomorrow evening, so later fcst may need to introduce
thunder into the TAF fcst products. Winds overall will be diurnally
driven during this period, however gusty outflows associated with
TSRA will likely affect the TAF sites starting late tomorrow
afternoon.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HODANISH
LONG TERM...STEWARD
AVIATION...HODANISH
Area Forecast Discussion
National Weather Service Las Vegas NV
828 PM PDT Sat Aug 14 2021
.SYNOPSIS...A strong area of high pressure centered over northwest
Nevada will lead to above normal temperatures through Monday.
A lingering moist and unstable air mass will continue to produce
isolated afternoon thunderstorms over the mountains of southern
Nevada and southeast California and better storm coverage over
northwest Arizona through Tuesday. Drier southwest flow and cooler
temperatures are expected to spread over the region after Tuesday.
&&
.UPDATE...Earlier isolated severe thunderstorm over the
plateau of northern Mohave County has weakened. However, outflow
from that storm just reaching eastern Lake Mead with 20-35 mph wind
gusts likely from South Cove to Temple Bar and Overton Arm. Also, we
have been monitoring thunderstorms over southwest Lincoln and
northwest Clark counties. Those storms are capable of producing wind
gusts up to 50 mph and brief heavy rain. Did a quick refresh of Pops
for the rest of tonight using latest camPoPs. No other changes.
&&
.PREV DISCUSSION...230 PM PDT Sat Aug 14 2021
.SHORT TERM...through Monday.
Thunderstorms developing over northern Lincoln County and southwest
Utah will tend to propagate toward the south-southwest late this
afternoon. However, low MLCAPE values and MLCIN persisting into early
evening should lead to cells dissipating before they reach Clark
County. There is still better potential for more sustained
convection moving from northern Mohave and western Yavapai counties
toward central Mohave late this afternoon and evening. This is
indicated by the latest HRRR and HREF. A similar setup remains in
place for Sunday afternoon and evening where only isolated
thunderstorms over southern Nevada will primarily be confined to the
mountains and central/southern Mohave County should see storms
moving in from the rim country during the late afternoon and
evening.
This pattern is driven by the clockwise circulation around the high
pressure centered over northwest Nevada. This high will bring a
couple days of above normal temperatures, especially over southeast
California and southwest Nevada which prompted the Excessive Heat
Warning which will be in effect for Inyo, western San Bernardino and
southern Nye counties from 10 AM Sunday until 8 PM. The center of
the high will be nudged down over southeast California and southern
Nevada on Monday ahead of a broad trough dropping into the Pacific
Northwest and Great Basin. This provide will provide one last day of
above normal temperatures and may suppress convection somewhat with
increasing temps aloft and a dry northwest to northerly flow.
.LONG TERM...Tuesday through Saturday.
The setup is now looking less favorable for deeper moisture to be
drawn into our region ahead of the aforementioned approaching trough
though lingering moisture should remain over part of southern Nevada
and northwest Arizona and maybe eastern San Bernardino County. There
should still be sufficient instability over these areas for
afternoon thunderstorms Tuesday and possibly again Wednesday and
this is reflected by the latest NBM PoPs which indicate more than
just terrain-based storms. However, the ECMWF and GEFS ensemble
means have been digging the base of the trough a little deeper
resulting a drier southwest flow which could scour moisture out to
the east during the Tuesday-Wednesday period followed by a
persistent dry west to northwest flow Thursday into next weekend.
The ensemble-based NBM PoPs are a little slow at indicating this
drying trend so far, but temperatures decrease several degrees after
Tuesday under the influence of the trough and PoPs will likely trend
downward over the next few model runs if ensembles continue to dig
the trough slightly farther south.
&&
.AVIATION...For McCarran...Light easterly winds are favored through
early evening before a trend toward more south or southeasterly
winds arrives late in the day. A few gusts in the 12-18 knot range
are possible with the southerly wind shift. Otherwise, just
scattered mid and high level clouds expected, with isolated
thunderstorms possible mainly east of Lake Mead, impacting the Peach
Springs approach corridor.
For the rest of southern Nevada, northwest Arizona and southeast
California...Outside of thunderstorm influences, mainly light and
diurnal winds are expected at the regional TAF sites. Scattered to
broken mid level cloud cover is likely across much of the region,
with isolated evening thunderstorm activity mainly in northwestern
Arizona.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Pierce
SHORT TERM/LONG TERM...Adair
AVIATION...Outler
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