Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/10/17

Area Forecast Discussion

National Weather Service Bismarck ND

 943 PM CDT Sat Sep 9 2017

.UPDATE...
Issued at 937 PM CDT Sat Sep 9 2017

Latest radar loop shows a lone shower lifting northward and
possibly clipping far southeast Dickey county. Remaining shower
activity should remain east of the CWA. Will remove mention of
thunder southeast and keep a mention of a shower for the next hour
over southeast Dickey county.

Mesoscale models are still not picking up on a strong signal for
fog over central ND tonight. HRRR/RAP are indicating some patchy
fog in the southern Missouri River Valley and east toward
Jamestown. Already a mention of patchy fog and may spread it just
a bit farther east, but no additional changes at this time.

UPDATE Issued at 633 PM CDT Sat Sep 9 2017

Moderate southerly flow continues over western and central ND
early this evening ahead of surface low pressure over eastern
Montana. Warm advection clouds/showers over eastern South Dakota
with a stray shower pushing northward through Dickey county. Could
still be a few showers or possibly an isolated thundershower over
the next few hours. This was covered in the previous forecast but
made some minor adjustments here for clouds and pops. Otherwise no
changes other than populating latest sensible weather elements and
interpolating to mid evening values.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 309 PM CDT Sat Sep 9 2017

Sunny conditions this afternoon per latest visible imagery. An upper
low circulating over central/eastern South Dakota continues to
push scattered mid level clouds into Dickey County at this time.
Regional radar shows a band of showers south of Aberdeen, South
Dakota trying to push north. The HRRR/RAP simulated composite
reflectivity`s still lift some higher reflectivity`s into Dickey
and LaMoure counties late this afternoon and evening. A slight
chance for showers/thunderstorm remains in the forecast until 06z
Sunday. Have also mentioned patchy fog/low clouds mainly southern
ND once again developing between 09z through 15z Sunday, as the
HRRR/RAP13 hint at this with a continuation of southeasterly winds.

Farther upstream, current surface observations and satellite
imagery indicate a large area of surface smoke and reduced
visibilities from Lewistown to Havre Montana, and into Medicine
Hat in Alberta Canada. With a cold front pushing through eastern
Montana late tonight, and into northwestern ND by mid morning
Sunday, winds will shift to the west/northwest. As a result, a
concentration of smoke, albeit lighter, will filter into the
western ND, per NDFD Air Quality Forecast and HRRR near surface
smoke and vertically integrated smoke (aloft). The smoke aloft
will likely spread into central ND Sunday afternoon and evening.
Have incorporated this mention into the gridded forecast through
Sunday evening.

For Sunday, the aforementioned cold front will move west to east,
reaching the James River Valley Sunday evening. Frontal passage
both in advance and behind the front during the day Sunday looks
dry, thus will maintain a dry forecast. Highs Sunday will be in
the mid to upper 80s.

.LONG TERM...(Sunday night through Saturday)
Issued at 309 PM CDT Sat Sep 9 2017

A warmup through midweek, then a sharp cool down Friday and
Saturday per the latest PNA/Pacific North American Teleconnection
Pattern. The PNA ensemble mean forecasts coincide rather strongly
together with each other as the mean value of the PNA index drops
below zero briefly around Sep 16th. This indicates a potential
cool down, and is further verified with both the GFS and ECMWF
850mb temperatures falling to +2C to +6C Saturday. Thus after a
dry and warm forecast Monday through Wednesday with high temperatures
in the 80s to lower 90s, a gradual cool down occurs Thursday
through Saturday, with highs in the 60s Saturday. In addition,
chances for showers/and some thunderstorms increase daily Wednesday
through Saturday, along and ahead of the cooler temperatures. The
main baroclinic zone/upper trough shifts into western and across
central ND Friday/Friday night. This represents the time period
for the highest chances of showers.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 937 PM CDT Sat Sep 9 2017

VFR conditions to begin the 00Z TAF period. Expect VFR conditions
throughout except for a period of possible fog around 10-16 UTC as
has been the case the past few days. The for this morning was
mainly along and west of the Missouri. Sunday morning indications
are the most likely areas would be central ND into the James River
Valley. Short term models are not indicating much in the way of
low stratus/fog at this time but given the persistent pattern and
low T/TD spreads expected around 12 UTC by BUFKIT forecast
soundings, we added a VCFG at KBIS and KJMS to start, and will
continue to monitor. Southerly flow will shift west to northwest
from west to east behind a cold front during the day on Sunday.
There were some restrictions to visibility over Montana today due
to smoke. Will need to monitor for possible restrictions in
west/central ND due to smoke behind the cold front.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...TWH
SHORT TERM...KS
LONG TERM...KS
AVIATION...TWH




AREA FORECAST DISCUSSION

National Weather Service Eureka CA

 329 PM PDT Sat Sep 9 2017

.SYNOPSIS...High pressure will bring warming and drying through
Monday. An offshore trough will bring a chance of showers and
thunderstorms around Tuesday. Seasonable weather conditions will
prevail through the remainder of the week.

&&

.DISCUSSION...Ridging aloft and associated subsidence will
continue to build over the area through Sunday as a cut-off low
meanders about offshore the central/southern California coast.
High temperatures were warmer today. Additional warming is
expected for Sunday as an offshore flow pattern emerges. Highs
in the interior valleys will climb into the 90s and peak around
100F. Coastal areas should warm as well on Sunday as the stratus
burns off. Current indications are for coastal highs to peak in
the upper 60s to mid 70s. The offshore flow will strengthen Sunday
night thru Monday and temperatures will warm a few more degrees
most everywhere. The GFS and NAM indicate broad southeast flow
aloft with an increase in high and mid level RH on Mon, mainly
across the southern and eastern portions of the forecast area.
The high layered clouds may knock temps down and reduce the
potential for additional warming on Mon.

A new upstream trough in the westerly flow will interact with the
central/southern California cut-off low on Tuesday. The best
opportunity for showers and storms appears to be on Tue or Tue
night as deeper moisture and instability combine forces with the
trough. The models continue to trend faster with ejecting the cut
off low eastward and out of the area on Wed. The upstream kicker
may generate some mountain showers Wed or Thu, however the threat
for additional t-storms is too low to worry about at this time.
Overall, we are looking at seasonable weather conditions with near
normal temperatures through much of next week.

&&

.AVIATION...A deep stratus layer impacted the north coast and
interior valleys this morning. Interior valley clouds eroded
quickly with daytime mixing while improvement has been slow along
the north coast this afternoon. Mendocino County, on the other
hand, had minimal cloud coverage with mostly VFR conditions
throughout the day. KCEC should remain VFR with scattered skies
the next few hours into the evening. The Humboldt Bay area should
slowly scatter the next few hours with KACV and KFOT possibly
seeing a short period of blue skies around 4 to 5 PM this evening.
Expect stratus to return to Humboldt Bay tonight bringing IFR to
LIFR conditions. A combination of increasing north winds over the
waters and dry easterly flow inland will help keep clouds out KCEC
through most of the night. However, a wind shift could allow low
ceilings to impact the airport late tonight thus I just hinted at
the possibly with a scattered deck in the TAF. Otherwise, the
Humboldt Bay area should observe a return of low ceilings and
visibility tonight with improving conditions for Sunday afternoon.
/KML

&&

.MARINE...The 11 AM ASCAT pass this morning confirmed fresh winds
across the southern waters ranging from 22 to 27 kt while winds
to the north were around 10 to 15 kt. North winds will continue to
increase tonight through Sunday with more widespread 20 to 25 kt
winds offshore and gusts around 30 kt. The HRRR seems to be
capturing current conditions fairly well so it was used for the
near- term wind forecast. Gusts to 30 kt will produce some steep
wind driven waves nearshore primarily around Cape Mendocino. Then
an approaching surface low will cause winds to weaken from south
to north bringing widespread gentle winds and southerly flow off
the Mendocino County coast Monday and Tuesday. The confidence in
the winds for later next week becomes low as models have been
having the tendency to over forecast the winds. That said, high
pressure across the northeast Pacific Ocean will bring a return of
increasing northerly flow. As far as the wave environment, it`s
looking more and more like summer is coming to an end with
persistent northwesterly swells expected to impact the waters
through next week. Otherwise steep wind driven waves will build
through Sunday and settle early next week. An advisory was issued
for marine zone 455 to account for gusty winds and steep waves
that propagate nearshore. /KML


&&

.FIRE WEATHER...Primary concern through Monday will be light to
moderate offshore flow along with drier humidities each night/day.
The NAM12 has 925mb winds reaching 15-20kt tonight into Sunday
morning over zones 201/203, however RH`s are forecast to remain
above critical fire weather thresholds throughout the forecast
area. More robust easterly flow with stronger drying is forecast
to develop Sunday night into Monday morning throughout the
forecast area. Once again the strongest easterlies (15-25kt at
925mb per the NAM12) will be over zones 201-203-204. Thus expect
gusty easterly ridge level winds around 30-35mph Sunday night for
the usually breezy mountain peaks. RH`s are forecast to remain
moderate til 6z-15z Monday when boundary layer RH`s plummet to
20%-30% throughout the forecast area, but with generally light
easterly ridge level winds from 5 to 10kt. We will continue to
highlight the potential for critical fire weather conditions for
all zones above 3000 feet. A red flag warning will not be necessary.

As for t-storms, the models continue to show the best potential
for storms and showers spreading northward into our neck of the
woods Monday night and/or Tue/Tue Night. The trend has been for an
upstream kicker to eject the central California cut-off eastward
out of the area on Wed.  We may still see some showers over the
mountains even with the drier westerly flow aloft Wed or Thu as
a s/w trough drops down from the NW. The threat for storms with
this s/w trough is too low to be a source of worry at this time.
The upshot, temperatures will be seasonable (about normal) and
subjectively pleasant through much of next week.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 11 PM PDT Sunday for PZZ470-475.
Small Craft Advisory until 9 PM PDT this evening for PZZ455.

&&

$$

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Area Forecast Discussion

National Weather Service Green Bay WI

 1029 PM CDT Sat Sep 9 2017

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 858 PM CDT Sat Sep 9 2017

Lowered temperatures across far northeast Wisconsin tonight and
increased the areal coverage of patchy frost over that region.
Only went with middle 30s for lows, so will hold off on a frost
advisory and just cover the situation with HWO/SPS.
&&

.SHORT TERM...Tonight and Sunday
Issued at 236 PM CDT Sat Sep 9 2017

The latest RAP analysis and satellite/radar imagery show high
pressure centered over the central Great Lakes. Southeast flow off
Lake Michigan has support a widespread cu field, which turned broken
for a short period late this morning. A weak shortwave is moving
over the northern Plains, but is running into a blocking ridge over
the Great Lakes. With the surface high remaining over the region,
clouds and temps are the main forecast concerns.

Tonight...High pressure will remain over the region. Will see clouds
dissipate with sunset, but a few clouds may arrive late tonight over
north-central as recycled moisture pushes in from the southwest. May
also see a few strands of strato-cu push in off Lake Michigan into
east-central WI towards morning. Temps continue to look warmer than
last night, though will probably see a few upper 30s over northern
Forest, Vilas, and Florence counties. Otherwise, lows mainly in the
40s.

Sunday...A shortwave will be moving into the northern Mississippi
Valley, but will likely remain too far west of the area for much
impact on our weather. Low level flow will turn more southerly,
which should continue to support more cu formation over eastern WI,
while scattered cu should also pop over the western edge of the
area. With the southerly breeze, temps will continue to warm into
the upper 60s to middle 70s.

.LONG TERM...Sunday Night Through Saturday
Issued at 236 PM CDT Sat Sep 9 2017

A long period of dry weather looks likely for Wisconsin, with
summer like conditions possible by the middle of the week, as an
upper ridge builds across the Great Lakes between the westerlies
to the north and the upper low that is formed after the hurricane
comes ashore and weakens. High and low temperatures may be ten or
more degrees above normal, with humidity rising as well. With the
waters of the lake and bay still in the mid 60s, it might be warm
enough to swim.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1025 PM CDT Sat Sep 9 2017

Mostly clear skies are anticipated overnight. The exception may
be some lake-enhanced clouds along the Lake Michigan shoreline
late tonight. These may linger into the morning at the MTW TAF
site, where brief MVFR ceilings may occur. Patchy MVFR/IFR fog may
also form late tonight, especially in north central and northeast
WI. Few to scattered cumulus should reform across the region by
late Sunday morning. South winds will also pick up a bit on
Sunday, with gusts to 15 kts in north central and central WI, and
along the Lake Michigan shoreline.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE.........Kieckbusch
SHORT TERM.....MPC
LONG TERM......RDM
AVIATION.......Kieckbusch




Area Forecast Discussion

National Weather Service Pocatello ID

 252 PM MDT Sat Sep 9 2017

.DISCUSSION...
Main forecast concern today is the potential for showers/t-storms.
Sufficient moisture is in place per surface obs. Our primary
source of lift will once again be terrain, but a weak wave/trough
brushing the region may also contribute. T-storm outflow
boundaries will also provide lift and help to make up the
difference in areas such as the Snake Plain. Instability is
sufficient for thunder but otherwise looks fairly marginal,
although the NAM generates CAPE values of 500- 800 J/kg over the
central Mntns and W portions of the Southern Highlands, and some
downdraft CAPE is available. Thus, our severe weather threat today
is once again very low. Similar to yesterday, the strongest cells
may produce wind gusts over 40 MPH, and to a lesser degree, perhaps
some small hail. High temps today should approach yesterday`s
values, but may be just a few degrees cooler due to cloud
cover/storms. Most of the short-term models also show an area of
precip moving NNE across eastern portions of the forecast area
overnight tonight. Confidence is low on exactly how this may
evolve, but have added a chance of precip.

A lingering shower/storm will be possible Sun afternoon near the WY
border, but otherwise high pressure is still on track to build
across the region Sun-Tues AM with dry weather.

Long range guidance continues to signal a significant change in our
weather pattern. A closed low pressure system is forecast to move
into CA Wed and then collapse into a trough/front that will push
into our region/wash out by Thurs AM. This trough/former low will
actually be rotating around an even stronger storm system moving ESE
into OR/WA late Thurs, moving E across ID with an associated
stronger cold front Thurs night/Fri AM. There are still notable
differences between the models on exact timing of precip/placement
of heaviest totals, but confidence is increasing that this will be a
strong system with the potential for widespread showers, storms, and
areas of rain. Have continued the trend of increasing PoPs from Tues
eve right through Fri night/Sat morning region-wide, highest Wed eve-
Thurs eve. High temps may not make it out of the 50s (mountains) and
60s (Snake Plain) by Fri. Stay tuned! - KSmith/Valle.

&&

.AVIATION...
Showers and thunderstorms remain in the forecast. We have VCSH or
VCTS through this evening at all TAF sites. VFR weather is
expected although with heavier rainfall, we could drop to
MVFR/IFR briefly. Gusty winds over 25kts are possible with
stronger storms as well. We kept VCSH overnight at KIDA and KPIH
as a wave lifts north across far eastern Idaho. There is actually
some potential of dropping to MVFR/IFR due to ceilings if we can
get some good rain going to moisten things up some more. For KDIJ,
that potential for showers and lower ceilings extends into
Sunday. - Keyes

&&

.FIRE WEATHER...
Showers and isolated/widely scattered thunderstorms will continue
into this evening. A weaker wave moves north near the Wyoming
border overnight, keeping showers going across portions of the
Snake Plain and eastern highlands. Thunder is NOT expected
overnight but we wouldn`t be surprised if a strike or two
occurred. For Sunday, drier air starts moving in BUT we are
expecting enough moisture for isolated storms over the highlands
especially east of I- 15. High pressure builds for Monday and most
of Tuesday shutting off showers/storms. By Tuesday evening and
beyond, expect a pretty decent storm to drop south out of Canada.
This will bring much cooler weather our way and a better chance of
precipitation for the middle and end of next week. - Keyes

&&

.AIR STAGNATION...
S to SW winds and increased moisture have reduced smoke levels
significantly in SE Idaho over the past 24-36 hrs. Visibilities have
increased to greater than 10 miles at all of our visibility-
reporting surface ob stations, and the latest monitoring from Idaho
DEQ shows air quality readings have improved to the "Good" category
across almost the entire forecast area. A review of regional webcams
does show some lingering smoke across portions of the Central Mntns,
where air quality values may still be "Moderate".

A chance of t-storms today (both their associated moisture and local
outflow winds) along with continued S to SW winds will continue to
help slowly reduce the smoke. Forecast confidence remains high in
this scenario. We do expect some smoke will linger in the Central
Mntns due to their proximity to several active wildfires, and
isolated lingering patches of smoke are possible in other parts of
our region, so we are maintaining mention of "patchy" smoke across
the entire forecast area ("areas" for Central Mntns). Beyond today,
the NAM/GFS both continue to advertise winds in the mid-levels of
the atmosphere will turn into the W Sun AM and WNW Sun night, which
MAY push some more smoke into portions of our region (especially the
Central Mntns) as dozens of large, active wildfires continue across
the NW. Guidance from the HRRR Smoke Model and AIRPACT-5 from
Washington State University hint at this trend, but it should be
noted that guidance at this time looks nothing like what we
experienced over the past week. All in all, forecast confidence is
fairly low in smoke evolution beyond Sunday, and for now we will
maintain the ongoing mention of smoke in the forecast region-wide
for the first part of the upcoming week. - KSmith/Valle

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$




Area Forecast Discussion

National Weather Service Pueblo CO

 313 PM MDT Sat Sep 9 2017

.SHORT TERM...(This evening through Sunday)
Issued at 313 PM MDT Sat Sep 9 2017

Most showers/tstms this evening are expected to be over and near the
higher terrain.  However, the NAM and HRRR continue to show some
storms moving east over the I-25 corridor and maybe even a little
farther east, especially in Las Animas county.  By late night, most
if not all of the pcpn should end.

A weak disturbance in the flow is expected to move over western CO
late tonight and then make its way slowly over central Colorado on
Sun.  This disturbance could help kick off some showers/tstms in the
mid to late morning hours over the central and portions of the
southwest mtns.  Then more showers/tstms will develop in the
afternoon hours over and near the higher terrain.  The models also
suggest that some storms could again move out along the I-25
corridor.  Temps will still be above average acrs the southeast
plains, with highs on Sun mostly in the mid 80s to lower 90s.  In
the San Luis and Upper Arkansas Valleys, highs will be around
average with readings in the 70s.

.LONG TERM...(Sunday night through Saturday)
Issued at 313 PM MDT Sat Sep 9 2017

Sunday night through Tuesday...Upper level ridge is forecast by
all models to remain anchored over the area, providing weak flow
aloft. Mid and upper level moisture remains trapped in the ridge,
so there will be daily chances for afternoon and evening showers
and storms, mainly across the high country and adjacent terrain.
A weak front will move across the eastern plains early Monday,
bringing weak upslope flow and increased low level moisture to
the plains. Temperatures on Monday and Tuesday will be above
seasonal levels in the 80s to lower 90s across the lower
elevations and mainly in 60s and 70s across the higher terrain.
and Tuesday.

Wednesday through Friday...A deep upper trough moving into the
western US early Wednesday will push the upper ridge south and
east through the period. Southwest flow aloft increasing across
the region into the end of the week, as the broad trough moves
out across the Great Basin and Northern Rockies. There are some
differences in location of the trough, but models in concurrence
with keeping daily chances of showers and storms across the
higher terrain. We may have decreasing chances of precipitation
across the eastern plains, as low level moisture decreases with
southwest flow aloft. Temperatures look to be at or slightly above
seasonal levels through the extended period.


&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued
at 313 PM MDT Sat Sep 9 2017

VFR conditions are expected the next 24 hrs at KCOS, KPUB and KALS.
All three forecast sites will also have the potential for
showers/tstms in the vicinity this evening and again late Sun
afternoon.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...28
LONG TERM...TM
AVIATION...28




Area Forecast Discussion

National Weather Service Sacramento CA

 300 PM PDT Sat Sep 9 2017


.SYNOPSIS...
Warming trend with showers and thunderstorms possible over
portions of the mountains through early next week. Cooler with
more widespread showers and thunderstorms possible toward the
middle of next week.

&&

.DISCUSSION...
Water vapor imagery showing upper low digging south along 123 W
this afternoon. Some cu/tcu has developed over the mountains with
a few isolated weak storms over the Sierra Nevada. Expect this to
be the main area of development into early evening per latest HRRR
runs. Afternoon temps running about 2 to 7 degrees warmer than
yesterday at this time and expected to max out slightly above
normal.

Upper low forecast to remain offshore and drift slowly south to
about latitude 32N Sunday then gradually meander back northward
early next week. Interior NorCal will warm over the weekend as the
low drifts farther away. Highs Sunday/Monday will be in the upper
90s in the Central Valley with triple digit heat in the Northern
Sacramento Valley. Main threat of afternoon showers or
thunderstorms will be over the Sierra Nevada, mainly south of I-80
Sun. Threat spreads farther north Monday to include Coastal Range
and mountains of W Plumas and Shasta as the low approaches again.

Upper low progged to be near the Central Coast again by Tuesday
and slightly deeper. This will result in some synoptic cooling
over Interior NorCal along with the possibility of more widespread
showers and thunderstorms.

PCH

&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)
Forecast remains on track as models indicate the persistent upper
low finally tracking inland across central California on
Wednesday. As a result, showers and thunderstorms are expected
given enough instability and moisture. Best chance of this
convection will be over the mountains, but the dynamics of this
system would suggest potential for showers and thunderstorms over
portions of the Central Valley as well. We`ll continue to monitor
trends. Drier weather is projected toward the end of next week.
Daytime highs will remain near or a few degrees below averages.

&&

.AVIATION...
VFR conds ovr Intr NorCal nxt 24 hrs exc isold tstms poss ovr
Siernev til arnd 03z. Gusty wind poss near tstms with lcl gusts
to 25 kts poss thru Delta.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$




Area Forecast Discussion

National Weather Service Tucson AZ

 320 PM MST Sat Sep 9 2017

.SYNOPSIS...Scattered showers and thunderstorms ending around
midnight tonight. Expect only isolated mainly afternoon and evening
showers and thunderstorms during the upcoming week. Warmer daytime
temperatures Sunday with above normal high temperatures continuing
Monday into Wednesday.

&&

.DISCUSSION...Scattered showers with isolated thunderstorms were
moving north-northeastward across southeast Arizona at this time.
The strongest thunderstorms were across far western Pima County,
with even stronger thunderstorms just south of the international
border south of Organ Pipe National Monument. The 09/12Z Univ of AZ
WRF-NAM and WRF-GFS as well as several HRRR solutions depict
generally scattered coverage of showers/tstms into this evening.

These solutions suggest that much of the Tucson metro area will
remain dry into this evening. At any rate, the official forecast
continues with isolated to scattered showers/tstms this evening,
then a slight chance of showers/tstms mainly east of Tucson late
tonight. Would not be surprised if precip-free conditions occur area-
wide late tonight, particularly if the high resolution models are
reality.

High pressure aloft will be centered over southern Colorado Sunday
morning with low pressure aloft centered west of the southern
California coast near 31N/122W. The mid-level steering flow is
progged to become more southeasterly Sunday versus the nearly sly
mid-level flow this afternoon. This flow regime may actually favor
showers/tstms to perhaps move into portions of the Tucson metro area
Sunday afternoon and evening. At any rate, have continued with
scattered showers/tstms across the White Mountains Sunday afternoon/
evening with isolated coverage elsewhere.

A fairly low-grade pattern for showers/tstms then exists Monday into
next Saturday. High pressure aloft is progged via the deterministic
GFS/ECMWF/CMC to build over this forecast area Tuesday as the upper
low moves northward toward the central California coast. The mid-
level flow Wednesday is progged to become southwesterly as the upper
moves eastward into central California, and high pressure aloft
migrates south of the area.

The bulk of deeper moisture Thursday should be shunted east of this
forecast area as southwesterly mid-level strengthens in response to
a tightening pressure gradient. However, enough moisture should
exist to support isolated afternoon/evening showers/tstms Wednesday
into Thursday east of Tucson with dry conditions elsewhere. Have
opted for dry conditions across much of the area Friday into next
Saturday as a low amplitude upper trough continues over the
southwestern CONUS.

Warmer daytime temperatures will occur Sunday into Monday followed
by no significant change in daytime temperatures Tuesday into
Wednesday. A modest cooling trend with high temperatures trending
closer to seasonal normals will then prevail Thursday into Friday.

&&

.AVIATION...Valid thru 11/00Z.
Scattered -TSRA/-SHRA ending around midnight tonight. Isolated
-TSRA/-SHRA returning Sunday afternoon. Otherwise, VFR
conditions into Sunday afternoon. Surface wind variable in direction
mainly less than 10 kts through tonight. Surface wind ely/sely
5-15 kts with gusts to 20 kts Sunday. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Isolated to scattered thunderstorms into this
evening followed by dry conditions across much of the area late
tonight. Only isolated thunderstorms are forecast to occur during
the upcoming week, mainly during the afternoon and evening hours.
Expect elevated wind speeds from the southwest Thursday and Friday
as a trough moves north of the area. Otherwise, 20-foot winds will
generally be terrain driven less than 15 mph.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None

&&

$$

Francis

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson



Area Forecast Discussion

National Weather Service Las Vegas NV

 907 PM PDT Sat Sep 9 2017

.SYNOPSIS...Scattered thunderstorms with heavy rain will continue
into early evening, especially in areas to the south of Las Vegas.
Moisture will remain in place through early next week, with shower
and thunderstorm coverage gradually decreasing each day. Moisture is
likely to be pushed out of the region later this week as a
transition to a drier, fall-like pattern begins.
&&

.UPDATE...Low pressure well offshore of SoCal was taking the best
forcing for thunderstorm development farther southwest than expected
earlier. Storms over our area went to bed early this evening, and
new model runs suggest much less activity Sunday than previous runs
showed. Thus, cancelled the Flash Flood Watch early. Also reduced
PoPs overnight tonight.
&&

.PREV DISCUSSION...
225 PM PDT Sat Sep 9 2017

.SHORT TERM...Through Monday night.

Thunderstorm coverage has increased over the past few hours across
eastern San Bernardino and southern Mohave Counties. 1000-2000 J/kg
surface based CAPE along with vorticity lobe lifting northeast
driving the convection in that area. With impressive precipitable
water values in place its making for a heavy rain storm environment.
The question becomes just how far north storm will make it into
Clark County. Confident northeast Clark and northern Mohave County
will not see heavy rain so cancelled the Flash Flood Watch. Las
Vegas may just be on the northern edge of storms so opted to keep
the valley in the watch for now. The HRRR indicates convection
should shutdown between 8-10 pm this evening. Closed low off the
central California coast progged to drift south Sunday with best
forcing shifting west across the San Gabriel and San Bernardino
Mountains. On Monday, low begins to shift back north with broad area
of diffluence for better coverage in showers/thunderstorms across
southern Nevada.

.LONG TERM...Tuesday through Saturday.

Closed low will shift eastward onshore of the California coast on
Tuesday. This will continue southerly flow over the area while
shifting best moisture and forcing westward resulting in decreased
activity levels. Best chances for showers and storms for these days
will be across the higher elevations with more isolated activity in
the lower elevations. The low will continue on its eastward track on
Wednesday and Wednesday night passing across the local area late in
the day. It will weaken in the process as it dissolves into the
prevailing flow ahead of a more prominent trough entering the
Pacific northwest Thursday and Friday. As the trough passes overhead
on Wednesday rain chances will be limited to the southern Great
Basin and northern Mohave County with mostly dry weather expected
for Thursday and Friday as drier air filters in behind the exiting
shortwave.

As low approaches and passes across the area midweek breezy south to
southwest winds of 15-20 mph gusting around 25 mph will be possible
each day Tuesday through Thursday. Slightly higher winds will be
likely across the western Mojave Desert. Temperatures will rise a
couple degrees Monday to Tuesday before dropping back down below
normal midweek behind exiting trough.

.AVIATION...For McCarran...Winds will remain out of a
northeast-east direction with speeds mostly 10 knots or less before
trending from the west late evening. Winds will shift back to a
northeast-east direction Sunday afternoon. Isolated showers or
thunderstorms this evening with a slight chance of storms possible
around the valley Sunday afternoon.

For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered thunderstorms will continue across southern
Mohave and eastern San Bernardino counties drifting northward into
Clark, Inyo, Lincoln, and Nye counties through early evening. Winds
will be forced by nearby convection but should otherwise follow
diurnal trends. Gusty, erratic winds will be possible with any
storms that move over the terminal in addition to heavy downpours,
lowering CIGS, and lightning.

.SPOTTER INFORMATION STATEMENT...Another day of showers and
thunderstorms capable of producing gusty winds and flash flooding
is expected. Spotter activation is requested for San Bernardino
and Mohave Counties. Elsewhere, spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&

$$

Update...Morgan
Short Term/Aviation...Pierce
Long Term...Guillet

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