Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/03/22
Area Forecast Discussion
National Weather Service Cheyenne WY
600 PM MDT Wed Nov 2 2022
.UPDATE...Winds have decreased across much of the region, and where
the High Wind Warnings were in place. With the wind dropping and
remaining below warning levels, the High Wind Warning was allowed to
expire. With the lighter winds also being observed in eastern
Wyoming and the Nebraska Panhandle, coupled with slowing increasing
humidity values, the Red Flag Warning was also allowed to expire.
Current Winter Weather Advisories remain in effect.
.SHORT TERM...(This evening through Friday)
Issued at 245 PM MDT Wed Nov 2 2022
All models continue to show a significant pattern change beginning
tonight and Thursday as a strong cold front and associated Pacific
upper level trough pushing across the region beginning late this
evening. The cloud shield ahead of the system is just starting to
push into central Wyoming with snowfall being reported across
northern Utah and far western Wyoming at this hour. Mild
temperatures will continue for the next few hours with
temperatures currently in the 60s across most of southeast
Wyoming, with low to mid 70s further east into western Nebraska.
Skies will gradually become mostly cloudy from northwest to southeast
this evening as the upper level trough gradually moves east across
the four corners region.
Current model trends show rain/snow mix beginning across Carbon
County sometime late this evening. This is a few hours later than
previous models suggested, but remains pretty much on track for
areas west of I-25. Any rainfall should quickly change to snow
overnight and into early Thursday morning with accumulating snow
expected after midnight for Carbon, northern Albany, and Converse
counties. Slick roadways look like a good bet mainly due to black
ice as the colder air moves into the area, but some snow covered
roadways are expected as well, especially above 6500 feet. Winter
Weather Advisories look good in these areas, but the Laramie
Valley may struggle with an unfavorable wind direction, both at
the surface and aloft through most of the event.
Models then show the system stalling a little as the first jet
streak lifts northeast and the upper level trough attempts to
close off near the four corners region. However, do not expect
this evolution to significantly affect the current forecast since
the upstream kicker will be quick to move into the Pacific NW late
on Thursday. As the storm stalls early Thursday, snow will likely
be delayed by several hours east of the I-25 corridor and further
south near Laramie and Cheyenne. Once the more significant 140
knot jet and associated vort max rapidly lift north ahead of the
main system Thursday afternoon and evening, precipitation is
expected to increase in coverage and intensity. With the NAMNEST
and HRRR starting to show this scenario with the potential for
some moderate snowfall, continued to increase POP along and east
of the I-25 corridor. With the colder air already in place,
precipitation may begin as all snow for areas around 5000 to 6000
feet of elevation. Therefore, the timing of the onset of snow
will be key in determining if the Winter Weather Advisories need
to be extended eastward. Models continue to show decent low level
frontogenesis lingering across the mountains and southern high
plains along with potent upper level diffluence associated with
the upper level jet Thursday afternoon and evening. Since the
timing of the bulk of the snow is questionable further south and
east, will hold off on extending Winter Weather Advisories towards
Cheyenne, Kimball, and Scottsbluff area. Generally, expect 1 to 3
inches of snow along and east of the I-25 corridor with locally
higher amounts of 4 to 5 inches possible along the Cheyenne Ridge
or near the Laramie Range.
Upper level trough will accelerate southeast across New Mexico and
northern Texas on Friday with snow ending early Friday morning. In
fact, expect clearing skies by sunrise Friday with cold
temperatures in the 20s and 30s. Upstream kicker across the Pac NW
will quickly move into Wyoming Friday with models showing a strong
130 knot anticyclonic jet pushing into the state. This is a
classic high wind pattern for the state and we will talk about it
in more detail below (long term discussion). Strong westerly
winds will start increasing as early as Friday afternoon across
the Wind Prone areas, so bumped wind gusts up towards 50 knots in
some areas. Will have to monitor the state of the snowpack by this
time since blowing snow is a possibility between Laramie and
Rawlins.
.LONG TERM...(Friday night through Wednesday)
Issued at 244 PM MDT Wed Nov 2 2022
Main story in the long term forecast focuses on the high wind event
progged for this weekend, with the 500mb flow pattern transitioning
towards a northwesterly to westerly winds and tightening height
contours. Models have been consistent over the last few runs with
strong subsidence developing along the 250mb jet pushing to the
southeast from the Pacific Northwest, and positioning the right exit
region of the across Wyoming and much of the High Plains. Omega
fields are in agreement with this feature, with deep negative values
and MSLP gradients tightening just along the spin of the Laramie
Range and persisting through 06z Sunday. In addition, both in-house
model guidance and the NBM v4.1 Probability of Exceeding 56kts
indicating a high likelihood of headline worthy winds beginning late
Friday night and easing by the evening hours on Saturday. Lastly,
CAG-CPR height gradients have been trending upwards, with 82 to 101
meters from Friday night through Saturday night. All in all,
downsloping wind storms are becoming much more evident with all the
atmospheric conditions coming into alignment. Therefore, confidence
is fairly high that high wind headlines will be needed with the
upcoming forecast packages. In spite of the strong winds, weekend
temperatures are expected to be fairly pleasant as they begin to
rebound from the freezing temperatures experiences the days prior to
the low to mid-50s for areas east of the Laramie Range attributed to
the downsloping component from the strong westerly flow and cooler
temperatures off to the west. Unfortunately, due to the strong
winds, the wind chill will feel much different and the temperature
felt will be in the high 30s to low 40s.
Next chance for widespread precipitation is progged for midweek, with
an upper level low developing off the Pacific Northwest and pushing
eastward, resulting in a trough axis digging southeasterly through
the CWA. Main concern with this system is if the moisture maybe too
far eastward into central Nebraska, keeping precipitation totals on
the lower end. Otherwise, most precipitation chances remain confined
to the western fringes of the of the CWA from late weekend through
Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 545 PM MDT Wed Nov 2 2022
Wintry weather will begin to move into the area tonight and
continue through the TAF period. KRWL could see a rain/snow mix by
04Z or 05Z tonight with it quickly changing to all snow by 06Z.
Expect IFR conditions due to low CIGs and poor visibility in snow.
CIGs will begin to lower through the morning hours for KLAR and KCYS
with VCSH likely. KLAR will likely see a more steady snow by the
afternoon hours, and KCYS by the evening hours. During these times,
flight conditions will likely drop to IFR. Western Nebraska
terminals will likely be spared of any winter weather for this TAF
period, but lowering CIGs and some scattered showers are likely.
Snow will be possible for western Nebraska terminals Thursday night.
&&
.FIRE WEATHER...
Issued at 137 PM MDT Wed Nov 2 2022
Red Flag/critical fire weather conditions have been spotty so far
this afternoon with solid criteria across zones 417, 434, and 433
(Niobrara Co, Goshen Co, and the far northern NE panhandle).
Elsewhere, winds have been lacking so far along with RHs between
15 to 18 percent. Will keep the Red Flag Warning going until 6 PM
since conditions are close enough. Otherwise, much colder
temperatures, higher humidities, and widespread snow moves into
the region starting late this evening. Cold temperatures will
continue through Friday before strong winds develop during the
weekend. Minimal fire weather concerns anticipated tonight through
early next week with a light surface snow pack expected.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from 4 AM Thursday to 6 AM MDT Friday
for WYZ104-105-109>111-113-115-116.
Winter Weather Advisory from midnight tonight to 6 AM MDT Friday
for WYZ112-114.
NE...None.
&&
$$
UPDATE...AW
SHORT TERM...TJT
LONG TERM...MRD
AVIATION...SF
FIRE WEATHER...TJT
Area Forecast Discussion
National Weather Service Dodge City KS
1029 PM CDT Wed Nov 2 2022
...Updated Aviation...
.SHORT TERM...(This evening through Thursday night)
Issued at 210 PM CDT Wed Nov 2 2022
Water vapor satellite imagery and RAP upper air analysis depict a
fairly amplified pattern is in place over the CONUS, with a strong
longwave trough west of the Rockies, and a ridge out east. At the
surface, low pressure extends from south-central Canada through
the central plains, with strong south to south-southwest winds
ongoing in southwest KS. These winds will persist through the
short term period, and combine with clear skies to result in a
warm fall day across our area, with afternoon highs in the upper
70s to low 80s. Later tonight, cloud cover will begin to spread
north as forcing for ascent increases ahead of the approaching
upper level trough, and skies will likely be mostly cloudy for all
areas by sunrise Thursday. Given these poor radiational cooling
conditions, lows are only expected to drop into the low to mid
50s.
Daytime Thursday, continued cloudy skies will help limit solar
insolation, resulting in temperatures peaking in the mid to upper
70s despite strong warm southerly flow. Forecast attention then
shifts to the potential for severe thunderstorms Thursday evening
through the overnight period. Unfortunately, significant
uncertainty remains regarding this event, with a large spread in
spatiotemporal details amongst guidance. As the aforementioned
strong upper level, positively-tilted trough begins to emerge from
the Intermountain West, thunderstorm initiation is possible along
a sharpening dryling extending from southwest KS southward into
portions of western OK and the eastern TX panhandle during the
00-06Z Friday time frame. However, how far north thunderstorms
can initiate is just one source of uncertainty. Given upper level
flow will be nearly parallel to the isovorts over southwest KS,
PVA will be limited, which will act against thunderstorms in our
area. This scenario is supported by multiple 12Z CAMs as well as
the 12Z NAM, however the 12Z deterministic ECMWF/GFS as well as
the 12Z HRRR/HiRes FV3 depict thunderstorms will develop along the
dryline in our area. Current thinking is any thunderstorm
development will not occur until the cold front that will be
diving south overtakes the dryline, although thunderstorms along
the dryline remain possible.
The next source of uncertainty with this event surrounds the
location of the dryline. Given mostly cloudy skies, boundary layer
mixing, which drives dryline propagation, will be shunted. This
throws into question how far east the dryline will mix before
retreating westward after sunset. Of the guidance members that
depict dryline initiation, they are nearly evenly split between
initiation along a Hays-Dodge City-Liberal line and a Larned-
Greensburg-Ashland line. While the tendency with synoptic features
would be to favor the ECMWF, which initiates thunderstorms along
the former line, historical trends suggest the dryline will set up
closer to the latter, and this is indeed the current forecast.
All of this said, the official forecast calls for dryline
initiation to fail until it is overrun by the cold front. Once
this happens, thunderstorms will favor roughly the eastern third
of our area. Accordingly, pops were limited to the chance
category (25-54%) for the whole event, while slight chance pops
(15-24%) were maintained west of Dodge City to account for the
substantial uncertainty. If dryline thunderstorms can form over
our area, they will pose a severe threat. At least 500-1000 J/Kg
of CAPE will coincide with 50-70 kts of 0-6km bulk shear, which
would be sufficient for storm organization. In addition, strong
low level flow will contribute to 200-300 m2/s2 of 0-1 SRH,
supporting some tornado threat. However, linear/messy storm mode
will likely limit hazards to hail and wind.
.LONG TERM...(Friday through Wednesday)
Issued at 310 PM CDT Wed Nov 2 2022
Elevated showers and thunderstorms may be ongoing at the beginning
of the long term period across southwest KS as the strong upper
trough ejects into the High Plains, however this is only strongly
supported by the 12Z HRRR/3kmNAM, and to a lesser extent the 12Z
deterministic ECMWF/GFS. If this scenario unfolds, thunderstorms
will be favored across the far east zones, while light rain/snow
mix will be possible near Syracuse and surrounding areas.
Otherwise, strong north winds Friday morning will usher in much
cooler temperatures while gradually relaxing during the day as
surface high pressure builds into the central plains. As a result,
afternoon highs will only be in the mid 40s to low 50s.
By the weekend, the strong upper level low will have departed the
High Plains for the Midwest, allowing winds to regain a southerly
component, skies to clear from west to east, and temperatures to
rebound rather quickly. Both Saturday and Sunday are therefore
expected to be beautiful fall days with afternoon highs in the
upper 60s to mid 70s amidst light winds. Early next week, 12Z
deterministic and ensemble runs of the ECMWF/GFS agree another
strong upper level longwave trough will begin to impinge on the
west coast, fostering lee cyclogenesis to occur over the northern
plains initially before spreading to the central plains on Tuesday
and Wednesday. This synoptic feature will bring the next chance
for precipitation for our area, however at the moment, any
precipitation appears likely to be displaced to the east. Higher
confidence exists in this wave bringing another strong wind/fire
weather event, which currently looks most probable Tuesday
afternoon. Either way, predictability at this range is not high,
and trends will need to be monitored.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1029 PM CDT Wed Nov 2 2022
VFR flight category will continue through this TAF cycle. South
winds will remain elevated through the night, continuing to gust
25-30 kts through 12z Thu. A strong low level jet will remain in
place, and kept LLWS mentioned at all airports through 12z Thu.
Strong south winds will again impact aviation operations daylight
Thursday, with gusts near 35 kts after 15z Thu. Increasing cirrus
is expected Thursday, but airports will be dry through 00z Fri. A
strong cold front is expected to reach the terminals around the
end of this TAF period, around the 06z Fri time frame. A northerly
wind shift is expected, and scattered thunderstorms are expected
along the cold frontal boundary, most likely near HYS/DDC in the
06-12z Fri time range.
&&
.FIRE WEATHER...
Issued at 210 PM CDT Wed Nov 2 2022
Near critical to critical fire weather conditions are expected to
arise Wednesday afternoon mainly across the far western portions
of our CWA. Strong south to south-southwest winds have already
developed over southwest KS, sustained in the 20-30 mph range with
gusts of 40-45 mph, as a lee cyclone deepens in eastern CO.
Additionally, clear skies and downsloping winds will aid
temperatures in warming into the upper 70s to low 80s this
afternoon, combining with dewpoints in the 20s and 30s to foster
minimum relative humidity in the 15-20% range. As a result, a Red
Flag Warning is in effect from 1 PM CST through 7 PM CST for
Hamilton, Kearny, Stanton, Grant, Morton, Stevens, and Scott
counties.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 55 74 37 52 / 0 10 50 20
GCK 53 74 33 48 / 0 10 30 20
EHA 52 75 33 48 / 0 0 10 20
LBL 51 77 35 52 / 0 10 30 20
HYS 56 74 36 48 / 0 10 50 30
P28 57 74 49 62 / 0 10 50 50
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Springer
LONG TERM...Springer
AVIATION...Turner
FIRE WEATHER...Springer
Area Forecast Discussion
National Weather Service Goodland KS
602 PM MDT Wed Nov 2 2022
.UPDATE...
Issued at 601 PM MDT Wed Nov 2 2022
Winds have diminished across the area and the Red Flag Warning
allowed to expire.
&&
.SHORT TERM...(This evening through Saturday Morning)
Issued at 308 PM MDT Wed Nov 2 2022
RAP analysis shows southwesterly flow over the area aiding in the
advection of warm and dry conditions. At the surface a trough was
present with a tighter pressure gradient over the eastern counties
where the gustier winds are present as a few gusts around 30 knots
have occurred. The Red Flag Warning continues for the majority of
the area. High temperatures have been panning out well forecast
wise as eastern areas have made it into the low 80s; a few record
highs are in jeopardy throughout the remainder of the afternoon.
Tonight should be similar to last night as winds will be breezier
through the overnight hours which will allow temperatures to
remain above normal for early November in the upper 30s to mid
50s.
The main story continues to be the deep trough that will advect the
area tomorrow. All 4 seasons may be realized in a 24-36 hour period.
The cold front looks to move into NW portions of the area during the
morning hours and then stall/slow down along/near a line from McCook
to Goodland to Cheyenne Wells. Quite a gradient of temperatures
across the CWA will be observed with portions of Yuma County
struggling to get out of the 40s to approaching 80 degrees in
eastern parts of the CWA. The recent guidance trends have been
slowly trending the front further south.
Jumping to the potential hazards: winds will be gusty to windy
ahead of the front with gusts from the SW at 30-50 mph; the
strongest gusts will look to reside south of Highway 40. The
timing of the winds looks to begin at diurnal mixing (~10am MDT)
and persists through sunset.
The severe weather potential remains on the low end as the
overall trough remains positively tilted. The also quicker
movement of the cold front may push any severe potential south and
east of the forecast area. If a storm were to form it currently
looks like Graham and Gove counties would have the relative best
potential. if a storm were to develop as well it would not be
until after sunset and would be relatively fast moving. The main
threats would be damaging winds as storms would grow quickly
upscale along the front, but a small tornado potential may exist
with any discrete cells or cells on the end of the line where the
strong wind shear can be most realized.
Local dust research continues to indicate the potential for a
plume of dust to originate in SE Colorado/SW Kansas and move
northeastward into portions of Greeley, Wichita, Wallace, Logan,
Gove and Graham counties through the afternoon. Currently not
anticipating any walls of dust, the event should be similar to a
few weeks back with 2-5SM of visibilities being observed. The
majority of the dust should remain south of I-70. Any dust
potential should end after the passage of the cold front.
Confidence is fairly high in dust occurrence due to the warm and
breezy preceding days to this event.
Near critical fire weather conditions are expected due to the warm
temperatures, gusty winds and ongoing drought conditions. If a
fire were to begin it would have the potential for rapid spread
as most if not all vegetation should be entering its winter
dormancy period. Any fire may also be hidden by any dust making it
difficult to see or respond to. The sudden switch to northerly
winds with the front would also to lead to dangerous conditions if
a fire were to be ongoing.
Into Thursday night/Friday morning, the quicker frontal passage has
increased the potential and confidence for wintry weather. Recent Hi-
Res guidance has snow moving into western portions of the area as
early as 02Z. A few areas of additional frontogenesis looks to form
across northeast Colorado with localized convective snow banding
potential possible. NAM and GFS suggests theta-e lapse rates and Fn
Divergence vectors being coincident with the frontogenesis band
which would suggest the potential for localized areas of heavier
snowfall. It is worth noting that the snow bands from the past
winter season had a margin of error of ~30 miles to the SE, so if
this band does form it may form closer to the Dundy, Yuma,
Cheyenne (KS) borders. Any snow accumulation will be difficult to
realize due to the warm ground conditions but elevated surfaces
may become slushy and slick. The wintry mix will continue into
Friday morning before become all rain as temperatures warm above
freezing.
Friday, I opted for a somewhat colder solution with highs in the low
40s as cloud cover and precipitation will linger for the majority
of the day. If the precipitation does last a bit longer the
actual temperatures may be lower and struggle to get out of the
30s which is closer to the wet bulb temperature. Light rain may
look to continue through the remaining of the day over the eastern
portion of the area and may mix with snow after sunsets and
temperatures cool.
.LONG TERM...(Saturday through Wednesday)
Issued at 126 PM MDT Wed Nov 2 2022
Per the latest GFS/ECMWF, the upper low at 500mb that will affect
the cwa in the short term period exits well east of the cwa going
into the upcoming weekend. There is a transition in both model runs
of a shift from northwest flow aloft to zonal/westerly flow this
weekend and eventually late in the weekend into next week, a shift
to southwest flow aloft ahead a low digging south into the west
coast region. By midweek next week, upper ridge amplifies over the
east, allowing for the west coast low to dig further and eventually
push east into the Rockies.
At the surface, high pressure over the northern Plains will move
slow east into next week, working in tandem the aforementioned upper
ridge to block the approaching low from the west. The GFS/ECMWF do
begin to differ slightly as to the potential for precipitation by
Wednesday. The surface low/front associated its upper component does
lift north along the eastern slopes of the Rockies Tue-Wed. Current
guidance has much of the cwa staying dry, with the potential for
slight chance pops in the far east for light rain. This falls with
the GFS as the front slides through the cwa. The bulk of any
potential moisture does stay east of the cwa in central KS where
better dewpts/rh reside.
The persistent drying could bring about fire wx concerns again,
especially for next Tuesday. Currently Colorado seeing as low as
upper teens for rh ahead of fropa, with wind gust potential
approaching the 30-40 mph range area-wide.
For temps, highs over the upcoming weekend will range in the 60s
area-wide. Going into next Monday, upper 50s to mid 60s which will
give way to mid 60s to lower 70s on Tuesday. By the middle of next
week, cooler air returns with a range from the upper 50s to the mid
60s.
For overnight lows, lower and mid 30s Saturday night give way to
slightly colder numbers with upper 20s to mid 30s expected for
Sunday night. Mid 30s west to mid 40s east for Monday night give way
to a colder trend with much of the cwa in the 20s Wednesday night,
with a few spots east around 32F.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 513 PM MDT Wed Nov 2 2022
VFR expected to prevail at both KGLD and KMCK through the TAF
period. A cold front will move through both terminals late
Thursday morning and early afternoon, with a resultant wind shift
to the north. Breezy surface winds possible at KGLD both ahead of
and behind the front, with gusts up to 25 kts.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...024
SHORT TERM...Trigg
LONG TERM...JN
AVIATION...024
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
926 PM CDT Wed Nov 2 2022
...New UPDATE...
.UPDATE...
Issued at 925 PM CDT Wed Nov 2 2022
Clear skies and calm winds prevailed across the Midsouth at this
evening. Surface dewpoint depressions had narrowed to 1 to 3
degrees F at 9 PM. 00Z NAM Bufr sounding for KMKL/Jackson and
HRRR surface visibility progs suggest patchy fog potential will
increase over rural valleys of west TN and north MS from about 5
AM to 8 AM. Current forecast handles this well, with a perhaps a
bit an earlier start than guidance suggests.
&&
.DISCUSSION...
(This evening through next Tuesday)
Issued at 246 PM CDT Wed Nov 2 2022
Great weather is on store for the Mid South over the next 36
hours. Expect clear and pleasant conditions through Friday
afternoon. The next system is expected to impact the forecast area
Friday night into Saturday. SPC made a special day 3 adjustment to
the SWODY this afternoon for areas off to the west. We will have
to see what the new day 3 outlook tonight has in store for the Mid
South as we could be outlooked for some strong to severe storms.
The system itself looks to be pretty stout. The kinematics look
to be fairly dynamic with a 125+kt upper level jet and a 25 to
35kt LLJ. However, thermodynamic support looks to be a big
limiting factor for strong to severe thunderstorms. Again, we will
have to see how things evolve, but the signal now points to maybe
some elevated thunderstorms. Beyond Saturday, look for typical
fall weather for the Mid South. Temperatures in the 60s and 70s
and perhaps a few lingering showers through early next week.
Otherwise, the only real impact is this weekend`s front for the
Mid South.
&&
.AVIATION...
(00Z TAFS)
Issued at 615 PM CDT Wed Nov 2 2022
VFR conditions will continue for the entire forecast period. Some
patchy areas of fog may develop overnight but it is not expected
at TAF sites. Winds will be light and variable tonight before
becoming southerly at 5 to 10 knots on Thursday.
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
PUBLIC FORECAST...PWB
AVIATION...ARS
Area Forecast Discussion
National Weather Service Reno NV
622 PM PDT Wed Nov 2 2022
.UPDATE...
Gone ahead and extended the Winter Weather Advisory for the Tahoe
Basin (including I-80) southward through Mono County until 12am
tonight. Radar trends, high resolution model guidance, and current
DOT webcams all suggest that periods of winter driving conditions
will continue through the evening hours before our focus turns to
the possibility of isolated lake effect bands during the
overnight and early morning hours on Thursday (see discussion
below for details on that). Even after snow showers diminish
tonight, use extra caution on the roadways as surface temperatures
below freezing are likely to refreeze, causing slick conditions.
-Dustin
&&
.PREVIOUS DISCUSSION... /issued 159 PM PDT Wed Nov 2 2022/
SYNOPSIS...
Periods of snow showers will bring slick conditions to some areas,
especially outside of daylight hours. Snow showers diminish Thursday
with milder conditions moving into the region Friday and Saturday.
The unsettled pattern continues as another round of cool, wet
weather starts late Saturday and continues through the middle of
next week.
DISCUSSION...
Today, the cold front that brought the initial taste of the coming
winter to the region continues to march east over the Rockies and
across desert Southwest. A broad area of northwesterly flow follows
with cold polar air streaming into the western US for the next 36-48
hrs. Earlier satellite imagery showed open cellular low and mid-
level cloudiness covering most areas from the Pacific Northwest into
California and the Great Basin region with a slight enhancement to
convection along the CA-OR-NV border.
* Snow showers: The ensuing increased instability from even
marginal daytime surface heating daytime will continue fuel
scattered snow showers over the Sierra and western Nevada
through this evening. Higher resolution CAM guidance foresees
these showers dancing across much of northeast CA, eastern
Sierra, and Basin and Range landscape for a few hours after
maximum heating. Showers should abate somewhat during the
overnight hours as radiative cooling and increased stability
continues through the early morning hours Thursday. Winter
weather advisories will continue across Lassen-Eastern Plumas-
Eastern Sierra Counties and the Tahoe Basin through 8PM
tonight.
* The only areas for snow shower concerns later this evening into
the early morning hours will remain around the southern
periphery of the larger area lakes. Lake Tahoe and Pyramid Lake
could see periods of bands of lake effect/enhanced snow showers
with an inch of two of accumulated snow several miles down wind
to their southeast through southwest shorelines. HRRR
simulations have also projected lesser extent bands of lake
effect snow showers early morning Thursday from Walker Lake as
well.
* Temperature drop: The increased post-frontal northerly flow
aloft will be reflected in the general drop of temperatures for
most areas 15-20 degrees below seasonal averages. Thursday
morning temperatures will put a definite chill to the bones as
lows across the region plummet into teens for most Sierra
locations with areas across the eastern Sierra and Mono County
dropping into the more frigid single digits. A proper taste of
the winter season to come! Area ski resorts will get the extra
benefit much from these colder temperatures with snow making
operations to supplement accumulations already on the ground.
Highs Thursday over most Sierra locations will struggle just
above the freezing mark with most lower valleys seeing January
like highs mostly in the low to mid 40s. Blended guidance does
project a brief warming trend through Saturday as temperatures
rebound into more seasonal territory before more unsettled
conditions and lower temperatures return early next week.
* Road impacts: Area interstates (I-80 from Fernley to USA
Parkway) and roadways (US 50/CA 89 from Meyers to Echo Summit)
in the downwind areas of Pyramid Lake and South Lake Tahoe could
see icy-slick conditions early morning Thursday that could
continue till roads warm sufficiently before midday.
* The way forward: A rather quiet period from overnight Thursday
through Saturday morning will be followed by an unsettled period
that looks to continue into next week. An amplifying upper
trough deepening over the western US will bring increases
chances for wetter and cooler conditions going into next week.
Although the lower end of probabilistic precipitation chances is
currently trending up, any increased confidence will remain
guarded till ensemble guidance aligns better going into the
weekend. Winds look to increase later this coming weekend across
northeast CA and northwest NV. These higher breezes with
increase chances for 30-40 mph gusts, look to spread south and
east into the eastern Sierra and far western NV respectively.
AVIATION...
Hi-Res radar simulations show widespread showers over northeast CA
into western Nevada this evening. Some terminals across the the
Basin and Range will see rain showers switching to mostly snow or
snow pellet showers going into the evening hours before tapering
off before midnight. Simulations also show most snow shower
activity shifting more south of US-50 and west of US-95 after
midnight with areas from KMMH-KHTH west into the eastern Sierra
(KMEV) with light snow accumulations lingering till at least 12Z
Thursday morning.
* SIERRA TERMINALS: Widespread terrain obscurations over higher
terrain areas with periods of IFR-MVFR conditions in light to
moderate snow showers through this evening. Snow showers will
gradually diminish overnight around the Tahoe Basin with the
exception of some light to moderate lake effect snow persisting
around KTVL until 13-15Z. For the eastern Sierra (KMEV-KMMH)
light snow will continue through early morning Thursday as an
increasing north-northeast flow enhances upslope over terrain
favored areas. Snow amounts will vary considerably but generally
between 0.5-2".
* WESTERN NV TERMINALS: Snow showers will begin to taper off north
of Hwy-50 going into the evening but a few light snow showers
should linger around KHTH into early morning hours Thursday.
Reductions in VIS/CIGS will bring rather brief periods of IFR-
MVFR conditions with lighter snow accumulations half inch or
less for area terminals if and when they occur.
* WINDS: A more northerly flow aloft at FL100 this evening will
remain around 15-20 kts. before turning more northeasterly
Thursday morning. Surface winds tonight will shift more from
the north to northeast 10-20 kts through Thursday.
* LONG RANGE: A longer stretch of stormy weather is looking more
likely this weekend into next week with multiple periods of valley
rain, mountain snow, increased breezes, and turbulence.
-Amanda
&&
.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until midnight PDT tonight NVZ002.
CA...Winter Weather Advisory until 8 PM PDT this evening CAZ071.
Winter Weather Advisory until midnight PDT tonight CAZ072.
Winter Weather Advisory until midnight PDT tonight CAZ073.
&&
$$