Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/08/20
Area Forecast Discussion
National Weather Service Denver/Boulder CO
853 PM MDT Wed Oct 7 2020
.UPDATE...
Issued at 756 PM MDT Wed Oct 7 2020
Other than smoke and fires, our weather continues to be very
benign. There was a new fire start along the Grand/Summit County
line this afternoon, which is only adding to the smoke. All told 5
significant fires, 2 of which are huge, are contributing to the
smoke in our area and that is expected to continue. HRRR smoke
shows a lot of smoke around tomorrow, but not as much as this
afternoon. The areas most impacted will be Jackson and Grand
Counties on the west slope, and Larimer and Weld Counties east of
the Divide. However, everyone will notice the smoke tomorrow to
some degree. Only adjustments were made to the smoke grids to
better represent coverage and impacts. The rest of the forecast
looks A-OK.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 413 PM MDT Wed Oct 7 2020
Smoke from the area fires is moving northeast and north-
northeasterly at this time. Something I haven`t seen with these
fires. There is still a decent coverage of "old" smoke over the
plains right now too. The Channel 7 Goes East Satellite pictures
do show the fires heating up right now. The current wind fields
across the plains is, mainly, easterly right now. Models keep
upper ridging over the CWA tonight and Thursday, along with weak
southwesterly flow aloft and neutral vertical velocity on the QG
Omega fields. There is very little moisture expected for the CWA
tonight and Thursday with precipitable water values progged in
the 0.20 to 0.40 inch range. Some of the model`s cross sections
hint at a few high clouds here and there. There is nothing noted
on the QPF fields. Will keep things dry; no pops. For
temperatures, Thursday`s highs look 0-1 C higher than today`s
highs.
.LONG TERM...(Thursday night through Wednesday)
Issued at 413 PM MDT Wed Oct 7 2020
Warm and dry conditions will continue through Friday night with
lighter winds in the mountains. There`s a weak shortwave Thursday
night that should produce a few clouds and a puff of north wind
over the plains Friday morning. Winds will increase ahead of the
trough on Saturday.
There`s still a lot of spread in solutions for the trough about
Sunday. Yesterday`s operational EC was toward the amplified end of
the envelope and it`s backed off some but is still more amplified
than the ensemble mean. GFS is quite progressive with a sharp
trough racing through Saturday evening and a quick burst of wind
behind it, but then going back to decent ridging by Tuesday. Our
model blend still seems reasonable with the usual bias
adjustments. The bottom line is a progressive system with the main
feature a shower band with the trough late Sunday, and the wind 24
hours before and after the trough. Most model solutions have
a little measurable precipitation with the trough, but then are
pretty dry behind it.
Discrepancies continue with how strongly the ridge builds behind
the trough. GFS would go back to warm and dry with diminishing
winds by midweek, though some ensemble members have a bit more
sharpness to a trough dropping through the plains Tuesday. EC
solutions have a bigger range and tend to keep us cooler and
windier for a couple of days but with the ridge starting to take
over by Wednesday. Again, the blended solution looks alright. A
few model runs have very light showers over the mountains at some
point in this period, but the vast majority are dry. The more
ridgy solutions would probably have pretty low humidities again
over the mountains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 756 PM MDT Wed Oct 7 2020
VFR conditions are expected other than perhaps during the morning
push at DEN when there could/should be enough smoke aloft to
result in ILS operations due to slant range visibility. Don`t
expect surface VIS to drop below 7-10 miles at any of the
terminals, much of the smoke will be aloft. In terms of winds,
drainage winds 10 kt or less (S to SSW at APA and DEN, W at BJC)
will go to light and variable during the mid to late morning hours
before noon Thursday. Diurnal east winds 6-10 kt are expected
through the afternoon into early evening, then a return to light
drainage winds after 10 PM.
&&
.FIRE WEATHER...
Issued at 413 PM MDT Wed Oct 7 2020
Nearly all the CWA can expected relative humidities values
falling into the 5-15% range during the afternoon Thursday.
Fortunately, light winds are expected in most areas. Obviously,
the fire danger will remain elevated.
Friday will remain very dry, but with less wind. An upper level
trough and cold front will move through Sunday. It will be windier
ahead of this trough late Saturday and early Sunday, with Red Flag
conditions possible. There`s a good chance of light precipitation
with the trough late Sunday, and mountain areas may get a few
inches of snow. At this time, the chance of heavy precipitation
looks low for the Front Range and near zero elsewhere. Behind the
trough in the early part of next week, it will be cooler with
higher humidities, but windy over the higher mountains and
foothills and breezy elsewhere. There will be a trend back towards
dry, warm, and breezy by midweek.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Schlatter
SHORT TERM......RJK
LONG TERM.......Gimmestad
AVIATION...Schlatter
FIRE WEATHER....RJK/Gimmestad
Area Forecast Discussion
National Weather Service Cheyenne WY
903 PM MDT Wed Oct 7 2020
.UPDATE...
Issued at 856 PM MDT Wed Oct 7 2020
Only a couple of forecast changes to mention this evening as the
rest of the forecast package looks to be on track. Smoke will be
intermittent overnight from the Mullen Fire near Laramie and other
areas of southeast Wyoming into the western NE Panhandle. Fire
Temperature hot spot satellite spectrum still shows regions in
southeast Carbon County and southwest Albany County burning as of
3Z. Dropped the overnight minimums by a degree or two with the
clear skies and westerly component of winds not creating as much
of a downslope immediately east of the Laramie Range for part of
tonight.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 230 PM MDT Wed Oct 7 2020
Clear skies persist once again across the CWA and much of the
Front Range as a 500-mb trough sits overhead. Currently a stalled
cold front has backed up along the Laramie Range resulting in
east to northeast winds that have helped clear out some of the
smoke earlier in the day. However, smoke plumes from the Mullen,
Cameron Peak, and Middle Fork wildfires have started to get active
again over the past hour which will transport smoke over the
region once again. An Air Quality Alert is in effect for areas
in close proximity to the Mullen Fire including Laramie and
Saratoga through noon Thursday while additional areas in southeast
Wyoming including Cheyenne will be under an Air Quality Alert
starting at midnight tonight as flow turns more southwesterly
spreading smoke over a larger area overnight.
With weak relative humidity recoveries expected overnight along
with stronger winds by late morning Thursday as more zonal flow
aloft takes over, Red Flag Warnings are in effect for critical
fire weather conditions Thursday morning through the evening. For
further details, see Fire Weather discussion below and Red Flag
Warning product text. Expecting additional air quality issues
heading into Thursday afternoon and evening as smoke plume growth
with the critical fire weather conditions around the Mullen Fire
is expected.
.LONG TERM...(Friday night through Tuesday)
Issued at 300 AM MDT Wed Oct 7 2020
Warm and dry conditions remain in place over the CWA Saturday with
the area under a swly flow aloft ahead of a digging upper trough
that will impinge on the west coast by late Saturday. This system
will progress eastward over the western CONUS Sat night and
Sunday and move across the Rocky mtn region Sunday night and into
the plains Monday. As it does so a pretty decent cold front will
sweep across the CWA later Sunday with at least sctd showers
behind the front Sunday night and Monday. Looks cold enough for
some snow over mainly the mtns Sunday night into Monday. Pcpn
should move out of the area Monday night as the upper trough axis
moves into the plains. Otherwise cool and rather breezy conditions
expected Monday and Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 527 PM MDT Wed Oct 7 2020
As a frontal boundary passed through winds have begun to turn in
its wake as winds as slowly shifted on the WY side to south and
southwest. Diminishment of winds with loss of daylight in next
couple hours. Kept similar forecast for KLAR from previous in
regards to smoke and poor flight conditions around 9z as the HRRR
and RAP show near surface smoke concentrations increasing under
southwest flow. Otherwise VFR conditions at remaining terminals
expected with diurnal increase in winds with gusts into the 20 kt
range.
&&
.FIRE WEATHER...
Issued at 220 PM MDT Wed Oct 7 2020
Despite weaker winds Wednesday afternoon, elevated fire weather
conditions continue across the region with relative humidity
dropping into the low teens and single digits this afternoon. Poor
recoveries are expected once again tonight only into the 20s
along and west of the Laramie Range. Low humidities along with
strong winds by late morning Thursday will make for critical fire
weather conditions once again and therefore a Red Flag Warning is
in effect beginning Thursday morning. Elevated to critical fire
weather conditions will continue into the weekend before a strong
cold front provides possible relief to the area along with the
chance for precipitation Sunday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from 9 AM to 8 PM MDT Thursday for WYZ301>303-
306>309.
NE...None.
&&
$$
UPDATE...BW
SHORT TERM...MB
LONG TERM...RE
AVIATION...WM
FIRE WEATHER...MB
Area Forecast Discussion
National Weather Service Grand Rapids MI
942 PM EDT Wed Oct 7 2020
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 222 PM EDT Wed Oct 7 2020
- Cool tonight
- Warm, breezy, hazy sky Friday
- More unsettled with rain chances next week
&&
.UPDATE...
Issued at 941 PM EDT Wed Oct 7 2020
I am concerned there may be a little more patchy fog than we were
at first thinking. Since the winds decouple and there is little if
any clouds, plus it is now fall and it takes longer for the sun to
come up and mix the boundary layer, I can see patchy fog
developing. The NAMNEST and RAP model show soundings that suggest
shallow fog. So, I updated our weather grids to have patchy fog. I
also lowered the low temperature around 2 to 4 degrees.
&&
.DISCUSSION...(This evening through next Wednesday)
Issued at 222 PM EDT Wed Oct 7 2020
-- Cool tonight --
Not too much of significance to talk about over the next few
days. Temperatures tonight will be fairly crisp as the surface
layer decouples under radiational cooling conditions. Dew points
upstream in Wisconsin are in the lower 40s or upper 30s, so with
low temperatures expected to be in that ballpark, patchy fog could
develop by daybreak. But there may be just enough pressure
gradient wind to help temper this. Also can`t rule out some
sprinkles north of M-20 before daybreak as some moisture around
850 mb advects through within a shallow layer of steep lapse
rates.
-- Warm, breezy, hazy sky Friday --
Friday will likely be the warmest day of the next several as low-
level southwesterly flow increases between a mid-Atlantic high
and western Ontario low. Afternoon gusts around 30 mph are likely.
The HRRR Smoke advects a plume of western US wildfire smoke 2 km
to 7 km overhead on Friday (heaviest smoke concentration between 4
and 6 km), so a hazy/smoky sky is once again expected.
-- More unsettled with rain chances next week --
Other than a slight chance of a light rain shower over the
weekend, the next appreciable chance of rain won`t arrive until at
least Monday. For now, the moisture plume from Hurricane Delta
will likely stay southeast of us on Monday, but it`s close enough
that we`re not counting it out. The spread in temperature and
precipitation outcomes in the ensembles increases markedly from
Sunday onward, as much is left to question in the evolution of the
northern Pacific jet streak as it moves into North America.
Global models are favoring an amplified trough or large upper
level low developing over central US/Canada next week, and its
progression or lack thereof will make the difference between a
week that`s mostly mild/wet or cool/dry.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 631 PM EDT Wed Oct 7 2020
Expect VFR conditions through Friday and likely beyond that.
The polar jet is core is over NE Lower Michigan as I write this.
The evidence for that is seen by looking at the visible satellite
loops, which shows considerable open cell cumulus clouds north of
a line from Big Sable Point to Detroit at 22z. As the polar jet
continues to lift out of our area through Thursday, surface high
pressure will replace it. That means light winds and few clouds.
Fog toward morning? Given the light winds and clear skies, it
would not be out of the question we could see some patchy fog
toward sunrise. The NAM12, NAMNEST and RAP model do show fog with
visibilities below 1 mile near and west of US-131 toward sunrise.
I am thinking the air is to dry for much fog but it is possible.
&&
.MARINE...
Issued at 222 PM EDT Wed Oct 7 2020
Small craft advisory will end late this afternoon and waves will
gradually subside this evening. Winds and waves will again become
hazardous to small craft by mid-day Friday into Saturday morning,
especially north of Holland.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...WDM
SYNOPSIS...CAS
DISCUSSION...CAS
AVIATION...WDM
MARINE...CAS
Area Forecast Discussion
National Weather Service Spokane WA
404 PM PDT Wed Oct 7 2020
.SYNOPSIS...
Warm and dry weather will persist through most of the week with
above seasonal high temperatures through Friday. A change is
expected over the upcoming weekend bringing wetter, cooler, and
breezy conditions. Many areas will see a quarter of an inch or
more of precipitation with high elevation snow possible by
Saturday night and again Sunday night. Next week will start out
unsettled with temperatures below normal.
&&
.DISCUSSION...
Tonight through Thursday...The strong upper level ridge which
has sat over the Inland NW for most of this week is going to be
weakened considerably by an elongated upper level trough and weak
cold front. This trough is forecast to shear apart with the
northern end passing through southern BC on Thursday. Before it
arrives, we expect to see another clear night with relatively mild
temperatures for early October. Lows will generally range from
the upper 30s to around 50. More fog is expected for some of the
valleys of NE WA into the Idaho Panhandle. So as for
Thursday...the trough will bring a subtle change to our stagnant
weather pattern. First off it could bring some increased high
cloudiness to the region, and it could even kick off some
sprinkles or light showers late in the day near the Canadian
border. The odds arent good, but they arent zero either. The
biggest weather change will be an increase in the winds for most
locations. West to southwest winds with gusts of 20 to 25 mph will
be possible by afternoon. This will lead to greater mixing
potential in the atmosphere and it could alleviate the potential
of California smoke moving into SE WA into NC ID late tonight into
tomorrow morning. The trough will also introduce a slight cooling
of the high temperatures with readings in the 70s which is still
around 10 degrees warmer than what it should be this time of year.
Thursday night and Friday...The weakening trough will quickly
exit the region with shortwave ridging moving back in. The main
impact of this will be lighter winds but temperatures will remain
quite mild for this time of year. Forecast highs will cool a
couple degrees vs Thursday which still equates to readings in the
upper 60s to mid 70s. fx
Friday night through early Sunday morning: Cloud cover will
increase throughout early Saturday morning as a trough of low
pressure moves into the region. The cloud cover will likely
disrupt the overnight radiative cooling process, resulting in
Saturday morning lows a couple of degrees warmer than the previous
morning. Saturday`s high temperatures are only expected to reach
around 60 degrees in most areas, and highs may be as low as 40
degrees in the northern valleys. These temperatures may be reached
as early as the late morning hours, depending on the timing of
the cold front passage. Saturday afternoon and evening bring the
best chances for gusty winds and wetting precipitation. In the
Columbia Basin, sustained winds of 25 mph and gusts up to 35 mph
are possible with a lower confidence of locally higher wind gusts
up to 40 mph. Storm total precipitation amounts range from 1-2
inches near the Cascade crest and higher elevations in northeast
WA and the ID panhandle, with lower accumulations from two-
hundredths to two-tenths of an inch expected on the lee side of
the Cascades. This rain shadow is supported by forecast west winds
at 700mb. Precipitation amounts will generally range from one-
tenth to three-quarters of an inch elsewhere. Isolated lightning
strikes along the front cannot be ruled out for the Okanogan
highlands into northeast WA. The bulk of the precip will move out
of the area by Sunday morning, but a sprinkle or two will remain
possible. Sunday morning, temperatures are expected to be more
fall-like, dipping down to the upper 30s and lower 40s for much of
the region with below-freezing values likely for protected
valleys and elevations above 4500 ft. Very light snow cannot be
ruled out Sunday morning for said high elevations, but impactful
accumulations are not expected. Any clearing of clouds will likely
be temporary due to a secondary shortwave trough moving through
the region Sunday night. RC
Sunday through Wednesday: There is little agreement amongst the
medium range model guidance making for a low confidence forecast.
Previous operational runs indicated a shortwave trough moving
through in the northwest flow on Sunday night. There is still some
semblance of a shortwave in the 12Z model runs, but the consensus
now points to a weaker disturbance with mainly just a chance for
some additional preciptiation. The Central Panhandle Mountains
will be most favored for precipitation in the strong northwesterly
flow. Snow levels look to hover right around 5,000 feet with
light snow possible on the higher peaks. The 12Z runs also show
the potential for a stronger and more moist shortwave disturbance
for around mid week, but there isn`t much support with the
ensembles and even less confidence with additional precipitation
for the rest of the week. The model ensembles continue to show
support for ridging toward the latter half of next week that would
dry things out and result in temperatures trending warmer.
Temperatures for Sunday into early next week though will be below
normal, and we should also be a bit breezy -- more typical of
fall than what we have experienced so far in October. /SVH
&&
.AVIATION...
00Z TAFs: VFR conditions are expected at all sites through this
forecast period. Skies will be primarily sunny through the day and
clear into the night with light winds. The only fly in the ointment
is the possibility of some near surface smoke pushing into SE WA/NC
ID late tonight into early Thu morning as the winds shift to the
south to southwest. The HRRR smoke model shows this reaching PUW/LWS
after 11z and up to GEG/SFFand maybe COE by 14z. Increasing winds
with gusts of 20 to 25 mph associated with a cold front will sweep
over the area by late morning into the afternoon. The front will
likely push any smoke well east of the area, but will also
bring increasing high and mid level clouds. fx
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 49 73 45 70 48 57 / 0 0 0 0 20 70
Coeur d`Alene 45 72 46 70 48 55 / 0 0 0 0 20 70
Pullman 48 71 44 71 44 56 / 0 0 0 0 10 70
Lewiston 51 78 50 77 52 61 / 0 0 0 0 10 70
Colville 43 73 41 71 42 60 / 0 10 10 10 40 70
Sandpoint 43 69 44 66 43 53 / 0 0 10 10 20 70
Kellogg 51 69 50 69 51 54 / 0 0 10 10 20 70
Moses Lake 49 76 46 74 49 63 / 0 0 0 0 30 60
Wenatchee 57 74 52 72 54 60 / 0 0 0 10 50 70
Omak 50 75 46 71 52 63 / 0 0 10 10 50 60
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
Area Forecast Discussion
National Weather Service Norman OK
1047 PM CDT Wed Oct 7 2020
...New AVIATION...
.SHORT TERM...
(This evening through Thursday)
Issued at 218 PM CDT Wed Oct 7 2020
Some mid/high clouds will develop and move into SE portions of
the CWA tonight in association with Hurricane Delta, which is
currently located just north of the Yucatan Peninsula. The HRRR
and HREF suggest some patchy fog developing tomorrow morning over
areas of western OK. Given the uncertainty at this time, however,
did not include in the weather grids.
The surface ridge situated over the eastern CONUS will continue
to provide for S/SE-ly winds, and wind speeds are expected to gust
up to 25 mph tomorrow (NW OK). With temperatures rising to the
low 90s (western OK/TX), and RH values dropping to 15 to 20
percent over tomorrow afternoon (NW OK), elevated fire weather
conditions will be possible across portions of NW OK on Thursday.
Thompson
&&
.LONG TERM...
(Thursday night through next Tuesday)
Issued at 328 PM CDT Wed Oct 7 2020
Warm, above temperatures are expected to continue through the
upcoming weekend. The impacts from the remnants of Hurricane Delta
should remain to the east given the forecast track into central
Arkansas (the precipitation gradient tends to be sharper on the
left side). There is still a low chance of showers across far
southeast Oklahoma. Otherwise, relatively benign weather is
antipicated through Saturday.
Very warm to hot conditions are expected on Sunday as a low-level
thermal ridge develops ahead of an approaching trough. 850 mb
temperatures are progged to increase markedly and range from ~20
to 25+ deg C. High temperatures are expected to be range from the
mid 80s to mid 90s deg F (well above seasonal averages). A
diffuse dryline may also result in veered low-level flow,
especially across western Oklahoma/north Texas. Drier air and
deeper mixing (with an attendant increase in gusty winds) behind
the dryline will result in elevated fire weather conditions Sunday
afternoon.
Forecast uncertainty increases slightly toward Monday of next
week. The ECMWF is deeper/more amplified with the approaching
trough than the GFS. Both models move the attendant cold front
through early on Monday with breezy northwest winds in its wake,
but the ECMWF track would suggest some post-frontal showers. The
National Blend of Models (NBM) included low probabilities for rain
on Monday, which seems reasonable give the uncertainty. Either
way, a cooler, more seasonable air mass is forecast in the front`s
wake through the middle part of next week.
Mahale
&&
.AVIATION...
(06Z TAFS)
Issued at 1044 PM CDT Wed Oct 7 2020
VFR conditions will prevail through the period. A light southeast
wind will become gusty by late Thursday morning and then
diminish by early evening.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 61 85 60 82 / 0 0 0 0
Hobart OK 60 88 58 86 / 0 0 0 0
Wichita Falls TX 60 88 59 86 / 0 0 0 0
Gage OK 55 91 58 91 / 0 0 0 0
Ponca City OK 59 87 58 84 / 0 0 0 0
Durant OK 60 85 63 81 / 0 0 0 10
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
SHORT TERM...01
LONG TERM....10
AVIATION...06
Area Forecast Discussion
National Weather Service Seattle WA
745 PM PDT Wed Oct 7 2020
.SYNOPSIS...Light onshore flow, marine air, and a few showers or
drizzle will develop overnight and persist on Thursday. A vigorous
frontal system will arrive Friday afternoon and evening. Wet and
unsettled weather will continue through the weekend and into early
next week with the first significant snow for the high elevations of
the mountains this weekend.
&&
.SHORT TERM /TONIGHT THROUGH SATURDAY/...Onshore flow with marine
air and a few showers or drizzle will be the rule through Thursday.
A vigorous frontal system will arrive Friday with some wet and
blustery weather--mainly in the afternoon and evening. Another
system arrives Saturday--that one is more of a trough with strong
onshore flow and some cooler air aloft. The high elevations of the
mountains will be picking up the first real snow of the season with
the snow level falling to 5000 feet for the weekend. 19
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Wet and unsettled
conditions look to persist early in the long term as another
quick-moving system potentially traverses the region Sunday night
into Monday for another round of moderate to heavy rainfall, breezy
winds, and high elevation snow for the mountains. Otherwise,
deterministic models remain a bit of a mixed bag heading into
next week. Ensembles hint at an upper level ridge building into
the region, however to what extent remains uncertain at this time
and will be resolved in the coming days. Should it be enough to
deflect additional systems to the north, a drying trend could
commence midweek. 14
&&
.AVIATION...Tonight will see a hodge podge of conditions as onshore
flow develops and stratus redevelops. There were still some patches
of fog that persisted through the day and into the evening--those
were mostly near the water. Marine stratus will be persistent on
Thursday. 19
KSEA...With the switch to onshore flow stratus will develop tonight
and persist as it lifts on Friday. A southerly breeze will develop
tonight and continue Friday.
&&
.MARINE...Onshore flow will develop this evening and persist into
Thursday. The HRRR has been showing less wind than the UW wrfgfs and
with the mainly calm winds in the Strait this evening I think 10-
20kts ought to be enough later tonight--and the same for the
northern waters. Winds will increase Thursday night and Friday ahead
of a vigorous front that will arrive Friday afternoon and early
evening. 19
&&
.HYDROLOGY...Several rounds of widespread rainfall are expected
over W WA in the coming days. A strong frontal system will begin
to push into the area early Saturday morning, carrying with it
widespread moderate to potentially locally heavier pockets of
rain. In the wake of the front Saturday afternoon and evening,
widespread rain will taper to widespread convective showers, with
the threat for isolated thunderstorms. Estimated rainfall into
Sunday morning is roughly 1-1.5 inches across the lowlands and 2-4
inches over the higher terrain. Although rivers will rise, no
flooding is currently expected. Another system may traverse the
area Sunday night into Monday, possibly bringing another round of
moderate rain. Additional rainfall totals of 1-3 inches may be
possible in higher terrain. Amounts will continue to be refined
in the coming days.
Kovacik/14
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
www.weather.gov/seattle
Area Forecast Discussion
National Weather Service Las Vegas NV
841 PM PDT Wed Oct 7 2020
.SYNOPSIS...Dry conditions and above-average temperatures will
continue through Friday before a pattern change brings more fall-like
temperatures to the area this weekend. Breezy to locally windy
conditions are possible with a slight chance for light showers
late in the week over the Sierra and the northern regions of
Lincoln and Mohave counties.
&&
.UPDATE...Quiet evening across the region with just a few high
clouds and generally light winds. Some additional high clouds are
expected to push into the forecast area overnight and early Thursday
in association with a weak disturbance. Not seeing much smoke in the
Owens Valley this evening, but the HRRR is trying to bring smoke
along with lower visibilities into the area by sunrise Thursday
morning. If this does occur, it looks like it should only remain in
place for a few hours before mixing out by late morning.
&&
PREV DISCUSSION
1240 PM PDT Wed Oct 7 2020
.DISCUSSION...Today through next Wednesday.
Today through Friday:
The weak disturbance over south-central CA has brought a band of
high clouds across the area this morning, leaving behind mostly
clear skies. Besides some passing high clouds, and subtle drop in
temperatures, not expecting any other impacts with this weak
disturbance as it continues to weaken and move ENE across the
southern Sierra. Southwest flow will remain through the rest of the
week, allowing for weak perturbations to move through the area
resulting in some afternoon breezes. Subtle pressure gradient across
far southeast NV/northwest AZ/southeast CA will bring increased
southwest winds Thursday with gusts to around 15-25 mph.
Increased winds and low RH`s will create elevated fire weather
conditions Thursday. By Friday, the gradient will relax a bit, but
southwest flow will remain as a weak shortwave begins to dig
across the eastern Pacific, keeping general breeziness across the
area. These weak disturbances will allow for temperatures to
decrease a few degrees each day, allowing high temperatures to be
a few degrees above seasonal normals.
Saturday-Monday:
Even 3-4 days away, guidance has not resolved the shortwave ahead of
the longwave trough and the evolution of the trough itself very
well. The latest GEFS ensemble guidance brings the shortwave down
the eastern Pacific and as far south as CA Baja spur, creating a
closed low. Additionally, the latest GEFS is not taking the long-
wave trough into the intermountain west like it previously had,
and instead only glancing it across northern NV. Whereas, the
ECMWF ensemble has been consistent in its evolution of these two
features - bringing the shortwave across the Mojave Desert before
weakening as it phases with the longwave trough that digs into
south-central NV/southwest UT. The Canadian Ensemble is similar to
the Euro. Given the differing scenarios, the overall impacts with
these systems expected this weekend remains to be gusty winds,
pre-frontal southwest winds and post-frontal northerly winds,
along with cooler temperatures behind the cold front expected to
move through Sunday. The magnitude of the winds with this system
is much less confident, but have been trending downward and
currently we`re only expecting gusts to 20-30 mph both Saturday
and Sunday. Even within the ensembles themselves, there`s still
considerable spread in the cold-fronts influence on temperatures,
but overall the trend continues to keep highs in the low 80s to
upper 70s for Las Vegas by Monday. Near freezing temperatures are
possible Monday and Tuesday mornings across some northern valley
areas in south- central NV and along the AZ Strip. With the
glancing nature of the trough and limited available moisture
associated with it, only slight chances of precipitation are
possible across the southern Sierra, south-central NV and northern
Mohave County. With snow levels around 10-8 Kft, some light
dusting of snow is possible across the higher elevations of the
southern Sierra and higher elevations of south-central NV.
Northwest flow is expected to remain through much of Monday,
keeping cool, northerly breezes in the forecast.
Beyond Monday:
By Tuesday, guidance begins to diverge, with a less confident
forecast. Northwesterly flow may continue, or a broad ridge may once
again build overhead.
&&
.AVIATION...For McCarran...Typically light drainage winds expected
overnight tonight with light and variable winds beginning to favor
an easterly direction Thursday morning. Late thursday afternoon, a
southerly push will sweep overhead aloft, but may not make it down
to the surface, leaving the possibility of light easterly winds, or
a southeast or southerly push making it to the airport. Expect low-
level clear-air turbulence and wind shear associated with the push
in the late afternoon.
For the rest of southern Nevada, northwest Arizona and southeast
California...Generally persistence forecast for southeast California
with typical drainage winds for most terminals. Thursday afternoon
will bring southerly flow up the Colorado River Valley into the
Great Basin, increasing clear-air turbulence and low level wind
shear, especially where surface winds do not turn southerly. Smoke
looks to spill down the Owens Valley once again briefly overnight,
then improve once again thursday morning.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Gorelow
DISCUSSION...Kryston
AVIATION...Steele
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