Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/13/23
Area Forecast Discussion
National Weather Service Grand Rapids MI
1039 PM EDT Sun Mar 12 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 1039 PM EDT Sun Mar 12 2023
No change at this time to the Winter Weather Advisory.
Latest guidance continues to put down a swath of around one third
of an inch of QPF from MKG to JXN overnight into Monday morning.
This zone/corridor represents the area of best mid level FGEN
forcing and deformation on the northeast side of the upper low
drifting southeast from WI. Even some trowal characteristics are
noted within this band, with pronounced thermal/theta-e ridge at
850 mb curling around the east and nrn side of the upper low.
Respectable omega in the DGZ is shown in this zone as well and
supports snow ratios on the order of roughly 15:1. The main
challenge with the fcst continues to be the exact placement of
the relatively narrow heavier band of snow which sets up within
the current advisory area. This is a typical conundrum when
dealing with an upper low-related band such as this.
Some amounts of 4-6" are certainly possible in spots, with latest
guidance still suggesting that the MKG to GRR area has the best
shot at that. Time of day and the cooler boundary layer conditions
under the upper low also supports the notion of locally higher
amounts near 6 inches.
Otherwise a broad 1-4" fcst is still the way to go within the
advisory and there`s even a possibility for a sharp nrn
gradient/cutoff leading to the nrn portions of Montcalm and
Newaygo counties not really seeing much at all from this.
Another thing to keep a close eye on is the possibility of a
separate burst of heavier snow around South Haven Monday morning.
This is an area of enhanced low level convergence in the vicinity
of the sfc trough which also has some help from lake effect via a
core of -12C air at H8 and westerly flow on the south side of the
upper low. RAP Fcst sounding at LWA during this time shows deeply
moist/unstable conditions cutting through the DGZ and extending
way up beyond 10K ft. If confidence grows in this scenario coming
to fruition, we may need to add the southwest corner counties
into the advisory.
&&
.DISCUSSION...(This evening through next Sunday)
Issued at 344 PM EDT Sun Mar 12 2023
-- Synoptic Snow Tonight into Monday --
First order of business is the light to moderate snow that will
pivot through Southwest Lower Michigan tonight and Monday. Bottom
line up front is we will be issuing a Winter Weather Advisory for
a swath of counties extending from the lakeshore southeast towards
Lansing and Jackson. The following counties are in the
Advisory...Oceana...Newaygo...Muskegon...Montcalm...Ottawa...
Kent...Ionia...Clinton...Allegan...Barry...Eaton...Ingham...
Calhoun and Jackson.
A period of light to moderate snow will begin this evening and
continue through tonight and into the afternoon on Monday. The
snow is associated with a compact vorticity maximum near the Twin
Cities in MN at the present time. Snow arcs out to the east of the
vort and its associated surface low into Eastern Wisconsin. The
vort in the mid levels and the surface low are forecast to pivot
through our area laying down a swath of heavier snow. Many areas
will at least see an inch of snow, but there is a zone in the
aforementioned counties that will likely see 2-4 inches. Would not
be surprised to see this system overperform a bit at least on a
local scale. Lift in BUFKIT overviews, like at MKG, is significant
and deep stretching through the DGZ especially in the NAMnest.
The models have been consistent in showing an axis of heavier snow
from MKG to LAN/JXN. Snowfall rates and time of day of heavier
snow (around daybreak) and air temperatures dipping into the 20s
tonight will likely bring about some impacts. Specifically we are
concerned that the morning commute to work and school on Monday
will be impacted. Extra time will need to be allowed to reach
destinations and roads will not be in ideal condition given snow
ongoing. Highest amounts may be in a zone across Muskegon...Ottawa
and Kent Counties given what we are seeing in BUFKIT overviews
and plan views of lift within the DGZ.
-- Period of Lake Effect Snow Monday Aft. into Monday Night --
A period of lake effect snow is expected on the backside of this
system Monday afternoon, potentially lasting into Tuesday morning.
850mb temperatures dip to around -15C, so when combined with lake
T`s around +2C, upper teens C delta T`s are in play. Plenty of
instability in place. Wind direction during this time frame will
be from the north-northwest (around 340 degrees). This places
Mason...Oceana and Van Buren Counties most in line for
accumulating snow. The most significant lake effect should
occur Monday evening between 00z and 06z when upper troughing is
still hanging on. We could see several more inches of new snow out
of the lake effect at places like Ludington, Pentwater and South
Haven/Covert. No headline at this point for the lake effect, but
later shifts will be monitoring.
-- Stronger system for end of the week with rain then snow --
A stronger system is still forecast by the medium range models to
affect the Great Lakes region. Initially a warm system with rain
Thursday into Thursday night. Precipitation begins to mix with
snow on Friday changing to all snow as we head into Saturday. The
GFS has +8C at 850mb Thursday night, plunging to -14C by Saturday.
Looks like the heavier snow with this system will occur north and
west of the low track which would place it in Wisconsin.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 756 PM EDT Sun Mar 12 2023
Snow will impact the terminals tonight and Monday. Generally MVFR
conditions this evening will trend to mostly IFR toward/after
midnight as the snow increases in intensity. Most of Monday
morning should feature IFR vsbys in snow as well before a
diminishing trend moves in after 18Z from northwest to southeast.
Gradual improvement in vsbys into at least MVFR category
anticipated as that occurs, with northerly winds increasing to 10
to 20 knots.
&&
.MARINE...
Issued at 344 PM EDT Sun Mar 12 2023
Small Craft Advisory looks good from this evening into the
Tuesday evening. An increasing north to north-northwest flow will
set up behind a departing low. The winds really ramp up Monday
morning after daybreak when winds increase to around 30 knots.
Solid 20-30 knot winds will continue into Tuesday morning. Waves
will likely approach or exceed 10 feet in much of the nearshore
zones, especially south of Holland.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 1 PM EDT Monday for MIZ043-044-050-
051-056>059-064>067-073-074.
LM...Small Craft Advisory from 11 AM Monday to 10 PM EDT Tuesday for
LMZ844>849.
&&
$$
UPDATE...Meade
DISCUSSION...Duke
AVIATION...Meade
MARINE...Duke
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1045 PM CDT Sun Mar 12 2023
.SHORT TERM... (Through Late Monday Night)
Issued at 158 PM CDT Sun Mar 12 2023
A rather deep upper low across the upper MS Valley will continue
to deepen and dig southeastward tonight leading to both weak
large scale height falls and the subtle passage of a secondary
cold surge late this afternoon and evening. Attendant with this
cold surge is a narrow band of decent low-level frontogenetic
forcing. This forcing along with a shallow zone of steeper low
level lapse rates could result in a band of light showers later
this afternoon and this evening, progressing from NW-SE and
impacting parts of eastern MO and southwest IL. A few of the CAMS
and especially the HRRR have been consistent depicting these
showers. I have added isolated showers into the forecast with this
in mind with the precipitation at any point short-lived and light.
Otherwise in addition to the current cloud cover another big surge
of stratus will spread into the area from the north tonight as
colder air spreads into the region.
The upper low/trof will continue to deepen as it moves into the
eastern Great Lakes/Ohio Valley on Monday and resulting in deep
cyclonic flow and CAA across the area. Monday looks will be the
coldest day of the period with well below normal highs owing to
cloud cover and the colder air mass. We could see a few flurries
or sprinkles across parts of the area, namely east of the MS
River in IL where the moisture is a bit deeper and magnitude of
the cold air is greater. High pressure will then build into the
region on Monday night as the aforementioned upper low/trof
continues to move east into the mid-Atlantic/northeast U.S.. How
cold we get will be dependent on the clearing of cloud cover, but
it certainly will be the coldest night in this stretch of the
week.
Glass
.LONG TERM... (Tuesday through Next Sunday)
Issued at 158 PM CDT Sun Mar 12 2023
There will be a lot of changeable weather during this period with
several significant pattern changes.
We pretty much remain locked under the influence of surface high
pressure on Tuesday with northwest flow aloft and confluence in
the the base of the upper trof progressing eastward. Clouds
should have departed and the low-level thermal trof will have
shifted eastward. As a result, temperatures overall will remain
below normal but won`t be as chilly as Monday.
By Wednesday the first pattern shift will be well underway as
upper ridging builds into the area and the surface high retreats.
The return to low-level south-southwest flow along with rising
heights aloft will bring warmer temperatures with most of the area
near to slightly above normal.
From late Wednesday night through Thursday into Thursday night
into early Friday morning we will see a return of active weather
as separate northern and southern stream upper trofs evolve into a
progressive more deeply meridional trof. There are some model
differences in how all this will come to fruition, as well as the
upper trof structure and timing. However at least into Thursday
evening those differences are negligible to the sensible weather.
Moisture transport will commence late Wednesday night/early
Thursday morning via a robust southwesterly LLJ and this could
produce showers across mainly parts of central and northeast MO.
Rain chances will ramp-up Thursday afternoon and night with the
progression of the upper trof and associated cold front and
attendant lift. Continue moisture transport and low level WAA will
bring even warmer temperatures, above normal, but how far above
will ultimately be dictated by the amount of cloud cover and
precipitation coverage. The lower and middle quartile of the NBM
temperature spread is entirely above normal. The resultant
advections will also bring a slight chance of thunderstorms into
the region associated with weak elevated instability. Whether we
see any post-frontal precipitation within the CAA is still in
question. This will be dependent on the upper trof structure and
the ensemble cluster analysis shows enough variance that there
remains uncertainly. A more progressive structure of the upper
trof aka the latest deterministic ECMWF would not support any
post-frontal precipitation. Alternatively a bit deeper and lagging
short wave aka the latest deterministic GFS would result in weak
large scale ascent, moisture, and frontogenetic forcing such that
there could be a short-period of post-frontal/anafront
precipitation distribution where rain changes to snow and results
in minor accumulations.
As we move Friday into Saturday the development of an expansive
upper low and trof over the upper Midwest and slow movement to the
east signals a cold period. The ensemble height cluster analysis
has good agreement on this pattern and the cluster analysis of 850
mb temperatures has over 90% of the population well below normal.
At this time the above pattern would favor below normal
temperatures Friday-Sunday and as much as 20 degrees below normal
on Saturday.
Glass
&&
.AVIATION... (For the 06z TAFs through 06z Monday Night)
Issued at 1035 PM CDT Sun Mar 12 2023
A deck of largely-MVFR stratus continues to drop slowly south
through the Mid-Mississippi Valley at this hour, now impinging on
the St. Louis metropolitan area. Gusty northwest flow is
reinforcing colder air moving into the region, which will keep
stratus in place overnight. Guidance continues to drop CIGs too
much, so this TAF issuance stays on the higher side. Some
terminals may remain out of fuel-alternate conditions for most (if
not all) of the night due to their elevation (particularly KJEF
and KSUS, which are a few hundred feet AGL below their surrounding
terminals).
The MVFR CIGs remain in place through the morning, though high
pressure will slowly move in from the west and erode the lower
stratus during the afternoon from west to east. I`m not confident
we`ll lose the clouds completely, but improvements to VFR
conditions are expected by the early afternoon at most sites. The
one exception is at and around KUIN, where low-level moisture
will be stubborn to exit. As such, the forecast is for MVFR to
continue through the TAF period in far northeast Missouri and
west-central Illinois.
MRB
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Mobile AL
658 PM CDT Sun Mar 12 2023
...New AVIATION...
.AVIATION...
(00Z TAFS)
Issued at 640 PM CDT Sun Mar 12 2023
Showers and storms will continue to move east across the area
through the evening hours. MVFR ceilings persist this evening
before IFR ceilings develop at the TAF sites overnight as light
to moderate rain persists near the coast. Ceilings eventually
erode after sunrise on Monday with VFR conditions expected by 12z.
Northerly winds will redevelop tonight as the cold front drops
into the area. Gusts up to 20kts are possible during the day on
Monday in the wake of the front. 07/mb
&&
.PREV DISCUSSION... /issued 502 PM CDT Sun Mar 12 2023/
..New MESOSCALE UPDATE...
MESOSCALE UPDATE...
Issued at 453 PM CDT Sun Mar 12 2023
Strong to severe thunderstorms remain possible across southeastern
MS into southwestern AL and the FL panhandle this evening. Several
supercell thunderstorms have developed over the past hour across
south-central MS with large hail being the primary hazard. KMOB
and KDGX VWP`s continue to exhibit long, straight hodographs above
1km AGL with muted low level curvature. As mentioned earlier, this
hodograph shape with strong mid-level shear supports hail growth
and hail production in splitting supercells. This is particularly
the case considering these thunderstorms remain elevated with
around 1,000 to 1,500j/kg of MUCAPE. There does appear to be a
MUCAPE gradient oriented northwest to southeast over southwestern
AL, which is evident from radar imagery of a recent storm
weakening after moving into Clarke and Monroe Counties. Unless
some airmass modification occurs over the next couple hours, this
would suggest the better severe threat will remain to the west
across southern Choctaw County southward into Mobile/Baldwin
Counties, and points west into our southeastern MS Counties. As
the shortwave and associated surface cold front continues to push
east into the early to mid evening hours, expect coverage of
discrete to semi-discrete supercells and multi-cell clusters to
continue to increase and for storm intensity to increase as well
until MUCAPE values diminish in the hours following sunset.
In summary, strong to severe thunderstorms with the threat for
large hail upwards of golf ball size remains possible across
portions of southeastern MS into southwestern AL, and perhaps the
FL panhandle through early to mid evening. MM/25
PREV DISCUSSION... /issued 357 PM CDT Sun Mar 12 2023/
.New NEAR TERM, SHORT TERM, LONG TERM, MARINE...
NEAR TERM...
(Now through Monday)
Issued at 244 PM CDT Sun Mar 12 2023
Showers and storms will continue to slide east across the area
through the mid evening hours for inland communities. Further to the
south (closer to the coast), showers and storms will continue to
develop and progress east through much of the evening. The HRRR has
the best handle on this afternoon`s convection and continues to show
redevelopment across the coastal counties and Gulf waters well into
the pre-dawn hours on Monday. As we head into the overnight and
early morning hours, the main concern will switch from hail to
nuisance flooding as showers and storms repeatedly moves over the
same locations along the coastline. Only expecting another inch or
so of rain overnight along the coast, but this may be problematic
given the heavy rainfall that has already fallen today and the
saturated soils (especially for locations south of I-10).
A surface high begins to build into the region in the wake of the
cold front tonight and Monday. Subsequently, northerly winds will
usher in much drier air to inland communities overnight with PWATs
falling below a half inch. Cold air advection sets up after midnight
and temperatures steadily fall into the 40s across inland
communities while remaining in the 50s along the coast/beaches.
Temperatures will struggle on Monday in this pattern with highs only
rebounding into the low 60s inland with upper 60s at the beaches.
Spring Break Note: The HIGH RISK OF RIP CURRENTS remains in effect
through tonight for coastal Alabama and northwest Florida beaches
with surf remaining around 3-4 feet. The risk subsides to MODERATE
on Monday as northerly winds persist at the beaches. 07/mb
SHORT TERM...
(Monday night through Wednesday night)
Issued at 244 PM CDT Sun Mar 12 2023
An upper level northwest flow will dominate through the period
with surface high pressure building into the area. This will
maintain dry and cool conditions with precipitable water values of
0.5 inches or less as northerly winds advect cooler and drier air
into the region. This pattern will keep temperatures below
seasonal norms for this time of year. Lows Monday night will range
from the mid and upper 30s inland to mid 40s near the coast.
Tuesday night will feature the coldest temps with lows in the low
to mid 30s inland to mid 40s near the coast. Temps will be very
close to freezing over far northern areas which we will continue
to monitor for a possible freeze watch due to the warm conditions
we have experienced recently. Highs on Tuesday will only be in the
upper 50s and low 60s inland to low 60s near the coast. Wednesday
will be slightly warmer, in the low to mid 60s across the area.
/13
LONG TERM...
(Thursday through Sunday)
Issued at 244 PM CDT Sun Mar 12 2023
Surface high pressure will move east of the area on Thursday with
a southerly flow developing. Meanwhile upper ridging will build
over the area as an upper trough digs across the southwestern
states. This will allow moisture to increase ahead of an
approaching cold front. This front is expected to bring the next
chance of showers and storms to the area on Friday into Saturday.
Highs on Thursday and Friday will warm into the low to mid 70s
with another shot of cooler and drier air moving into the region
behind the front. /13
MARINE...
Issued at 244 PM CDT Sun Mar 12 2022
A moderate to strong onshore flow persists over the nearshore
and offshore coastal waters this afternoon as an outflow boundary
sits along the coast. Offshore flow will set-up later this
afternoon into this evening as a cold front dives south into the
marine area. Moderate to strong offshore flow will continue
through the early part of the week before subsiding by midweek. A
light to moderate onshore flow is expected to redevelop late in
the week with a gradual increase in winds by Friday. SCA
conditions persist over most of the marine area through Monday
morning. 07/mb
&&
.PRELIMINARY POINT TEMPS/POPS...
Mobile 49 66 42 62 42 66 45 73 / 70 0 0 0 0 0 0 0
Pensacola 53 66 45 62 44 65 49 70 / 80 0 0 0 0 0 0 0
Destin 56 68 46 61 45 63 50 69 / 80 0 0 0 0 0 0 0
Evergreen 46 64 37 59 36 64 37 73 / 70 0 0 0 0 0 0 0
Waynesboro 44 63 37 58 36 64 38 73 / 40 0 0 0 0 0 0 0
Camden 44 61 35 57 34 62 36 72 / 50 0 0 0 0 0 0 0
Crestview 52 68 40 62 38 66 39 72 / 80 0 0 0 0 0 0 0
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through Monday morning for ALZ265-266.
FL...High Rip Current Risk through Monday morning for FLZ202-204-206.
MS...None.
GM...Small Craft Advisory until 10 AM CDT Monday for GMZ630>632-650-
655-670-675.
&&
$$
This product is also available on the web at:
www.weather.gov/mob
Area Forecast Discussion
National Weather Service Reno NV
252 PM PDT Sun Mar 12 2023
.SYNOPSIS...
Bands of rain and snow showers continue through Monday, mainly for
the Sierra and northeast California, with isolated thunder also
possible through this evening. Heavier precipitation with
increased winter and hydrologic impacts arrives with a stronger
storm late Monday night through Tuesday. Unsettled and showery
conditions remain possible later this week through next weekend.
&&
.SHORT TERM...through Tuesday Night...
The Pacific moisture continues to stream into northern and central
CA, with higher elevation (7500+ feet) snow totals adding up to
between 2 and 3.5 feet since Thursday night. The next shortwave
within the moist flow will bring increased convective activity
across central CA this afternoon-evening with bands of heavier
rain and snow showers spreading over the Sierra and western NV.
While snow levels will generally range from 6000-7000 feet during
this activity, they could dip to near 5500 feet at times from
Tahoe northward during heavier shower bands. A few lightning
strikes may occur near the Sierra crest and also in west central
NV near and east of US-95.
For late tonight through Monday, the overall shower coverage is
expected to decrease with orographic effects limiting most
activity to areas near the Sierra northward to western Lassen
County. Western NV will remain dry on Monday with milder
temperatures ranging from the 50s to near 60 degrees.
Monday night will feature the early stages of the more
significant storm with another atmospheric river connection.
Precipitation will increase across northern CA and push into the
Sierra with increasing intensity, but the consensus of the
guidance holds off on spreading precip across lower elevations of
eastern CA-western NV until near daybreak on Tuesday. This period
of shadowing could allow for a period of stronger winds during the
overnight/early morning hours.
The main effects and impacts of this storm continue to target the
region during the day Tuesday, producing the following highlights:
* WINDS: We will issue a High Wind Watch for all of western NV and
the Surprise Valley as a period of 60+ mph gusts is possible in
these areas, but confidence levels aren`t high enough for a
definite major wind event. The eventual position of the upper
level jet will affect the location and magnitude of the peak
winds. When the main precip pushes through western NV (most
likely Tuesday morning-midday) the wind speeds could be dampened
a bit, but the afternoon-evening still holds a window of
opportunity for stronger gusts to mix down into lower elevations
when precip rates show a decrease but stronger winds aloft
remain overhead. Sierra ridges can expect gusts surpassing 100
mph all day Tuesday. Plan on wind-related travel impacts,
especially for aviation interests and high-profile vehicles.
* SNOWFALL/SNOW LEVELS: A short period of higher snow levels is on
tap from Tuesday morning through early afternoon as the main
surge of subtropical moisture arrives. However, the heavier
precip intensity along with a slight intrusion of cooler air
with the advancing low pressure center should prevent an
excessive rise, with projections relatively consistent to near
6500 feet for northeast CA/northwest NV, 7000-7500 feet for the
Lake Tahoe Basin eastward across western Nevada along I-80 and
US-50, and near 8000 feet for Mono County and western Nevada
south of US-50. These snow levels will then start dropping by
late Tuesday, eventually bottoming out below 4000 feet well
north of I-80, between 4000-4500 feet from I-80 to US-50, and
near 5000 feet south of US-50 by early Wednesday morning.
However, most of the precipitation is expected to diminish
before the coldest air arrives. If any low elevation snow
occurs, the best chances are north of Susanville-Gerlach closer
to the upper low`s inland track, with potential for 1-3" prior
to daybreak. Around the main urban areas, spotty amounts up to
1" are possible if a stray snow band manages to hold together in
the pre-dawn hours. Higher elevation snow potential is detailed
in the Winter Storm Warning message, with heavy wet snowfall
adding at least a couple more feet of snowpack depth mainly
above 7000 feet. but amounts drop off quite a bit below 7000
feet.
Prepare for significant travel impacts and delays over Sierra
passes starting Monday evening, which could last through early
Wednesday morning. As always, check road conditions with Caltrans
and Nevada DOT before traveling.
We have seen several structural issues from snow loading in the
Sierra communities from recent storms. Snow loading concerns on
structures will likely increase with the added heavy rain and
snow especially on Tuesday. There will also be a higher risk of
roofalanches in these areas. Follow guidance from local officials
and building inspectors for ways to monitor and mitigate the risk
of increased snow loads on roofs.
* LOWER ELEVATION RAINFALL: A new Flood Watch has been issued for
lower elevations due to the expected period of heavier rainfall
on Tuesday combined with more saturated ground conditions. This
could aggravate flooding concerns in areas already impacted
during the recent rain, even though the faster movement and
shorter duration of Tuesday`s heavier rain spreading into
western NV has trended the rainfall potential a bit lower
compared to previous projections. The latest precipitation
forecast for Tuesday shows 0.30-0.70" for far western Nevada
communities of Reno, Carson City, and Minden, with around 1"
possible for foothill areas including Virginia City. Amounts
taper off to 0.10-0.30" into the Basin and Range of western
Nevada. While areas south of US-50 in west central NV currently
are less likely to have the spillover moisture compared to last
Friday, their rain totals could increase if a deeper
subtropical moisture feed sets up longer over Mono County. MJD
.LONG TERM...Wednesday onward...
Wednesday will start with weather related impacts winding down
as the strong AR driven storm begins to exit the region. Flooding
concerns could still remain even though precipitation will start
to wind down. Temperatures will be the first sign that things are
changing as lows Wednesday night slide down 5 to 10 degrees below
seasonal averages. These lower temps will also decrease snowmelt
across lower elevation areas across the Sierra. Temperatures
through the remainder of the week, however, will make a gradual
comeback to more seasonal averages.
We’ll finally get a much needed rest from the relentless days
of heavy mountain snows and lower elevation rain on Thursday into
much of Friday. This period will be brief as this current
progressive pattern will continue through the weekend. The next
weather system is looking to bring another round of precipitation
later next weekend with guidance trending slightly higher with
amounts, although well below the magnitude of Tuesday`s storm.
That being said, anticipate another quick shot of higher
elevation snow and valley rain later Saturday into Sunday.
Ensemble guidance is presenting the notion that less snow will
fall around the Lake Tahoe Basin with this upcoming weekend storm,
but there is a good chance that travel impacts will continue for
higher Sierra passes. However, these periods of higher elevation
snow and lower valley showers are looking to bring fewer impacts
going into next week as the systems moving onto the west coast
are projected by the ensemble guidance to be on the weaker side.
-Amanda
&&
.AVIATION...
Unstable airmass over CA continues to generate scattered
thunderstorms upstream over the Central Valley. Latest HRRR
projects these cells to spill over into the TVL/TRK and
eventually RNO/CXP/MEV areas this afternoon and evening. A 50/50
chance for LIFR snow squalls at TVL/TRK with brief runway
accumulations, and even some lightning in the vicinity. For MMH
there is a chance for IFR snow showers if convective cells can
spill into the higher terrain. For Western NV including RNO mainly
looking at on/off MVFR rain showers between 22z this afternoon
and 06z this evening.
Winds have remained elevated on the ridges with gusts above 40 MPH,
so we could see some brief gusts of stronger wind this afternoon
and early evening. Flow aloft remains breezy so that could set
up some wind shear overnight into early Mon AM. For Monday,
airmass remains unstable so continued risk of rain/snow showers
remains, though latest HRRR shows more isolated precip coverage
-Chris
&&
.AVALANCHE WEATHER...
Waves of Pacific moisture will continue to produce additional
rounds of snowfall through Tuesday. Several inches of new
snowfall will continue to accumulate on top of the deep existing
snow pack creating varying snow densities.
Another atmospheric river (AR) will bring increased winds, heavy
snowfall rates along with high snow levels. These conditions will
result in low snow-to-liquid ratios Monday night through Tuesday.
* 24-hr Snow Water Equivalent (SWE): 1-3" through tonight for the
Lake Tahoe Basin/Alpine County, with heaviest totals north of
US- 50, then decreasing to about 0.75-1.50" from tonight through
Monday. Lesser SWE rates of 0.50-1.00" for Mono County through
Monday. SWE rates increase again late Monday night through
Tuesday with the next incoming AR.
* Snow-to-Liquid Ratios (SLR): Medium to high snow-to-liquid
ratios about 11-15:1 through tonight, then trending lower late
Monday through Tuesday with SLR’s dropping 4-8:1 between
6500-8000 feet and 8-12:1 above 8000 ft.
* Winds: Southwest winds continue with gusts generally 55 to 65
mph across the ridges through tonight, with an increasing trend
late Monday through Tuesday where ridge top gusts could exceed
100 mph.
-Johnston/Amanda
&&
.HYDROLOGY...
Heavy rain and snowmelt associated with the atmospheric river
Monday night through Wednesday will renew flooding potential
mostly in areas below approximately 7000 feet. Areas of primary
concern are small creeks and streams, and areas with poor or
obstructed drainage, especially if impacted by flooding recently.
Renewed river flooding is also a concern especially in the Carson
Valley, along the Carson Mainstem, and along the East Fork and
mainstem of the Walker River. Areas of concern for potential new
river flooding include the Pit River into Big Valley, the Susan
River near Susanville, and the Middle Fork of the Feather near
Portola. Flooding is not currently forecast at these points, but
they should be closely monitored as minor flooding can not be
ruled out.
The combination of wet soils, primed low-mid elevation snowpack
and currently high streamflows will lead to a more rapid response
to rainfall, even if we have less rain and lower rain-snow
elevations then our previous atmospheric river event. Expect new
and renewed flooding problems Tuesday morning through Wednesday.
Ongoing high flows on the Walker River and along the Carson River
(both above and below Lahontan Reservoir) could lead to new
impacts with any additional inflows or debris issues. -Bardsley
&&
.REV Watches/Warnings/Advisories...
NV...High Wind Watch from late Monday night through Tuesday evening
NVZ001-003>005.
Flood Watch from late Monday night through Wednesday evening
NVZ001>004.
Winter Storm Warning until 5 PM PDT Wednesday NVZ002.
CA...High Wind Watch from late Monday night through Tuesday evening
CAZ070.
Winter Storm Warning until 5 PM PDT Wednesday CAZ071.
Flood Watch from late Monday night through Wednesday evening
CAZ071>073.
Winter Storm Warning until 5 PM PDT Wednesday CAZ072.
Winter Storm Warning until 5 PM PDT Wednesday CAZ073.
&&
$$
Area Forecast Discussion
National Weather Service Sacramento CA
228 PM PDT Sun Mar 12 2023
.SYNOPSIS...
Periods of rain with high elevation snow today, along with
scattered thunderstorms in the Valley. Another wet, warmer system
early week bringing moderate to heavy rain, high elevation snow,
and renewed flooding concerns.
&&
.Discussion...
Upper level trough is pushing east over the far part of the state.
This short wave has been bringing widespread showers to the area
with some locally moderate to heavier rain in the northern San
Joaquin Valley. It has also kept skies mainly cloudy across the
region. This has had a major impact on instability and our
thunderstorm chances and was always the wild card for today. Meso-
Analysis is estimating 100-250 j/kg of ML-CAPE from about
Sacramento north to Chico. HRRR runs are still favoring the
northern San Joaquin Valley to about Sacramento for scattered
thunderstorms this afternoon which doesn`t seem reasonable at this
point and the HRRR has been under doing these showers all
morning. The better thunderstorm chances today will likely be
south of our area into Hanford`s area. We still could see some
isolated thunderstorms mainly over the central and southern
Sacramento Valley. Model soundings are still showing good
hodographs, sufficient 0-1 km shear, high PWATs, and CAPE in the
hail growth zone. This would indicate that we could see some
stronger storms but cloud cover has likely modified these sounds
some. Still will have to keep an eye on any thunderstorms that
develop but heavy rain at this point looks to be the biggest
threat.
Overall we will see showers diminish overnight with them lingering
over the mountains. A deeper trough and cold front will then
approach the area later Monday into Tuesday. This will bring the
return of periods of heavy rain and heavy mountain snow. Models
are in slightly better agreement but still seeing a wider range in
the 500 mb pattern than what you would like to see this close to
the event. The GEFS continues to be slower and a bit further south
with the southern part of the trough. Overall there is good
agreement with QPF though, it`s looking like 1.50-3" in the Valley
and 3-7" over the foothills and mountains.
Snow levels will be 5500-6500 feet into Monday rising to pass
level Tuesday as the burnt of the storm hits us. Snow levels fall
Wednesday falling back down to 3500-5000 feet. Several more feet
of snow is expected over the Sierra with this storm. This will
bring travel issues at times mainly as you get to the passes.
We will also see gusty southerly winds with this system. 850 mb
wind increase to 45-70 knots Tuesday morning into the afternoon.
This will result in winds gusting 45-60 mph across much of the
area and up to 70+ mph over the higher Sierra.
With another warmer and wetter storm in the forecast for Monday-
Tuesday flooding is a concern. Streams, creeks, and rivers will
continue to rise as we see additional rain and snow melt. Some
urban and street flooding will also be possible mainly Monday
night through Tuesday. Streams, creeks, and rivers of most concern
will be those coming out of the Sierra.
A few showers will linger on Wednesday mainly over the mountains.
Upper level ridge will build in later in the day bringing the
return of dry weather.
-CJM
&&
.EXTENDED DISCUSSION (Thursday THROUGH Sunday)...
Dry weather forecast for Thursday into early Friday as short wave
upper ridging moves through. Short wave trough progged to follow
Friday afternoon into night. This system looks weak and QPF
limited. First part of Saturday appears dry except for some
possible lingering mountains showers. Another storm is progged
later Saturday into Sunday. Model differences exist with timing
and associated precip amounts resulting in some forecast
uncertainties at this time.
&&
.AVIATION...
Widespread MVFR cigs with areas IFR and isolated LIFR conditions
over interior NorCal next 24 hrs. Snow lvls 5500-6500 ft. Isolated
tstms possible through 03z again Monday 21-02z. In Central Vly,
areas Sly sfc wind up to 20 kts possible aft 18z with lcl gusts to
30 kts over the northern Sacramento Valley through Monday
afternoon. Over mtns, areas S-W sfc wind gusts up 40 to 50 kts
possible.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Wednesday morning for Burney Basin / Eastern
Shasta County-Carquinez Strait and Delta-Central Sacramento
Valley-Motherlode-Mountains Southwestern Shasta County to
Western Colusa County-Northeast Foothills/Sacramento Valley-
Northern Sacramento Valley-Northern San Joaquin Valley-Shasta
Lake Area / Northern Shasta County-Southern Sacramento Valley-
West Slope Northern Sierra Nevada.
High Wind Watch from Monday evening through Tuesday evening for
Carquinez Strait and Delta-Central Sacramento Valley-Motherlode-
Mountains Southwestern Shasta County to Western Colusa County-
Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-
Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta
County-Southern Sacramento Valley-West Slope Northern Sierra
Nevada-Western Plumas County/Lassen Park.
Winter Storm Warning until 4 PM PST Wednesday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.
&&
$$