Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/28/19
Area Forecast Discussion
National Weather Service Marquette MI
752 PM EDT Wed Mar 27 2019
.SHORT TERM...(This evening through Thursday)
Issued at 418 PM EDT WED MAR 27 2019
WV imagery and RAP analysis indicated a trough over north central
Canada and a ridge over the srn/cntrl plains resulting in zonal
mid/upper level flow from the northern plains through the western
Great Lakes. A shortwave trough and associated 1000 mb low was
located over northwest Ontario with a cold front through the nw
corner of MN and eastern North Dakota. Strong WAA 295k-300k (around
700 mb) isentropic lift supported a band of showers from eastern
Lake Superior to around KERY. Some tsra lingered over eastern Lake
Superior where MUCAPE values were near 500 J/Kg. Otherwise, a tight
pres gradient has pushed ssw wind gusts to 35 mph as temps climbed
to around 50.
Tonight, radar/satellite suggests that the showers over the east
will quickly exit Upper Michigan late this afternoon leaving a
period of partly cloudy skies. As the cold front moves through after
03z, there may be some light pcpn. However, nothing more than
sprinkles with weak to moderate 900-700 mb fgen behind the front.
Southwest winds veering nw will remain strong enough to keep temps
in the mid 30s.
Thursday, CAA with nw winds will bring in moderately cooler air as
850 mb temps drop to around -8C. There should be enough sun to boost
max readings into the mid 40s.
.LONG TERM...(Thursday night through Wednesday)
Issued at 351 PM EDT WED MAR 27 2019
Continued quiet with no impactful conditions expected.
Starts out with partly cloudy skies Thu night and Fri with lows in
the mid teens to mid 20s and highs in the mid 30s to mid 40s.
An upper trough moves in Fri night into Sun night, which will only
result in some light snow at times from lake effect and a shortwave.
Not surprisingly, models changed significantly with the track of the
surface low and now keeps any synoptic precip from that way S of the
CWA. 850mb temps drop to around -15C Sat afternoon and evening, but
daytime heating will limit coverage/intensity and snowfall amounts.
A shortwave drops through Sun afternoon and evening according to the
GFS and CMC, but the ECMWF is weaker and farther SW. Could see some
light rain/snow mix with this if the better precip from the GFS and
CMC verify, but nothing significantly impactful.
No significant precip expected early next work week. Could see a
more active period in the middle to end of next week, but there is a
lot of uncertainty with details given very poor model agreement and
run to run discontinuity.
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 747 PM EDT WED MAR 27 2019
VFR conditions are expected at KIWD/KCMX/KSAW through this
evening. Although moisture is advecting into the area under sw
winds, this moisture will only lead to cloud bases in the
4000-6000 ft range this afternoon. As the cold front arrives, cigs
should fall to MVFR at KIWD and KCMX overnight. A tightening sw pres
gradient ahead of the front will result in LLWS this evening while
west winds behind the front later tonight into Thu morning could
gust up to 25 knots, mainly at KCMX. &&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 418 PM EDT WED MAR 27 2019
South winds of 20 to 30 knots will become west behind a cold front
tonight and nw on Thursday and then diminish at or below 20 knots
Thursday night. Winds increase again to 30 knots Sat from the
north. These would be the strongest winds for the forecast period.
Area Forecast Discussion
National Weather Service Reno NV
314 PM PDT Wed Mar 27 2019
The ongoing storm with rain, wind, and mountain snow impacts will
move east tonight. Scattered snow and pellet showers are expected
Thursday afternoon with more isolated coverage Friday. Temperatures
will warm to above normal this weekend with dry and pleasant weather.
Additional storms are possible next week but low certainty on
severity and impacts.
Rain & Snow Through Thursday...
* Slightly increased QPF for later this afternoon/evening mainly
south of the Tahoe Basin and into Mono County due to position of
upper level jet enhancing spillover.
* Lowered snow levels for this afternoon/early evening due to the
heavy precipitation band associated with the system`s cold
Overall, not many changes were made to the short term forecast in
regards to precipitation amounts and snow levels through
Thursday. Taking a look at radar, a heavy and convective
precipitation band is currently moving through the Sacramento
Valley area and is expected to make its way into the Sierra by
late this afternoon/early evening. Snow has already begun to fall
in higher elevations in the Sierra, but is having a hard time
sticking to the roadways. This should change as precipitation
increases in intensity and snow levels drop quickly down to ~6000
ft as this band (cold front) moves through. During this time,
conditions will deteriorate rapidly leading to hazardous travel,
especially for areas in the Sierra. Due to the convective nature
and time of year, do not be surprised to hear a rumble of thunder
or see a flash of lightning due to these unstable conditions.
As the core of the low pressure system shifts closer to the west
coast early this evening, its associated upper level jet noses
into the Tahoe Basin and Mono County region. This set up should
lead to higher precipitation amounts and better spillover into the
western Nevada valleys. The steadier precipitation rates should
calm down and be reduced to on and off snow/pellet showers by
later tonight as the bulk of the atmospheric moisture tap cuts
off. These showers persist into Thursday with even the chance for
afternoon thunderstorms as the unstable conditions stay in place.
When it`s all said and done expect 1-2 feet of snow accumulation
above 7000 ft in the Sierra, 6-12 inches between 6000-6500 ft,
with minimal amounts below 6000 ft. As for the western Nevada
valleys, precipitation will be mainly rain with the potential to
see 0.10-0.30" of accumulation.
Wind Through Thursday...
* Minor changes to increase wind gusts Mono/Mineral for Thursday
* Strong gusty S/SW winds will persist through this evening as
respectable upper jet combines with low level thermal gradient.
Latest HRRR has reasonable trends pushing the strongest winds
east-southeastward with time as spillover works into W Nevada.
Could see some pockets of high impact winds along Hwy 95/Walker
Lake and Hwy 395/Washoe Valley. Sierra ridges gusting earlier
over 100 MPH but those winds should start to subside some this
evening as upper jet heads eastward.
* Winds relax quite a bit Thursday as surface high noses in from
California. Only area of some concern is S Mono and Mineral
Counties where low level pressure gradient appears stronger in
GFS, which could lead to some channeling of NW flow. Overall
travel impacts would be on the low-end.
Notes on Friday through Next Week...
* Changes: Raised daytime highs for this weekend. Increased rain
shower, t-storm chances and amounts for Monday.
* This coming weekend looks quite pleasant with upper ridging
moving overhead. Temperature guidance has trended upward and
daytime humidity trends down, and have followed this. 70 at RNO
and 60 at TVL/MMH is attainable Sunday if skies remain sunny
enough. Would be the first 70 at RNO this year - a bit tardy
since March 10 is the average first 70 (since 1990). Above
normal temps will likely persist into next week which could
start melting some of the lower elevation snows. This would lead
to minor rises on creeks/rivers but not a flooding scenario.
* Pattern next week favors weak-moderate and mild Pacific storms.
Wave moving through Monday is the most obvious example with
widespread rain showers even into mountain communities with high
rain-snow lines. Some spots especially N Sierra, NE Cal into far
NW Nev could pick up 1/4 to 1/2" rainfall. A few t-storms even
possible for the 1st day of April within a weakly unstable
airmass. Can`t rule out additional similar waves next week but
predictability this far out is limited.
* Of perhaps more interest are the increasing signs for a strong
atmospheric river landfall on the west coast late next week.
GEFS and EPS guidance support a feature like this, with highest
probabilities for landfall in far N California up into Oregon.
Our region is close enough where it wouldn`t take a radical
pattern shift for us to get a dose of heavy precip in the N
Sierra into NW Nevada. Not at all time to freakout, but
definitely worth keeping an eye on given the ripening snowpack.
We`ve had strong AR landfalls and heavy rains in early April
both in 2018 and 2017. Typically the frequency of AR impacts
decline rapidly during the month of April.
* Passing upper level jet of 120+ kts and low level thermal
gradient will lead to continued rough air across the Sierra and
W Nevada through this evening. Many reports of LLWS which will
persist due to substantial directional and speed changes below
mountain ridgetops. Winds Thursday will be quieter with high
pressure moving in. Exception would be toward MMH BIH and HTH
where low level gradient will promote gusty NW winds.
* Band of heavy precip working into the Sierra from Central CA
this afternoon. Feature is sliding south and as it does we`ll
see a period of heavy IFR/LIFR snows and even thundersnow at
Sierra airfields including TVL TRK and MMH. Good chance of
seeing runway accumulations even with antecedent warm pavement.
80% chance of at least an inch, with 30% chance of 4 inches or
more depending on how cold temps get during heavier snow bursts.
* Spillover into W Nevada will be confined into this same heavy
precip band. Should see 1-3 hour period of MVFR rain showers at
RNO CXP late this afternoon into early evening per latest HRRR,
but probably have a hard time making it east to NFL and HTH.
Wind will be the greater issue there.
NV...Lake Wind Advisory until 11 PM PDT this evening for Lake Tahoe
Winter Storm Warning until 11 PM PDT this evening above 6500
feet in NVZ002.
Wind Advisory until 11 PM PDT this evening NVZ001.
Lake Wind Advisory until 11 PM PDT this evening for Pyramid Lake
CA...Winter Storm Warning until 11 PM PDT this evening above 5500
feet in CAZ071.
Winter Storm Warning until 11 PM PDT this evening above 7000
feet in CAZ073.
Lake Wind Advisory until 11 PM PDT this evening for Lake Tahoe
Winter Storm Warning until 11 PM PDT this evening above 6500
feet in CAZ072.
For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Sacramento CA
331 PM PDT Wed Mar 27 2019
Pacific storm moves through today into Thursday with rain,
mountain snow, and possible thunderstorms. Drier weather Friday
into the weekend with unsettled weather early next week.
The Pacific cold front attendant to the offshore upper low has
just moved across the Greater Sacramento area. This has been
accompanied by a broad band of slow moving southwest-northeast
oriented showers. Somewhat unusual for this region, pulse-like
thunderstorms are firing ahead of this line within a pool of
instability. Normally this would be expected in the wake within
the dome of cool, unstable air aloft. Vertical shear profiles are
favorable for weak rotation so would not be surprised to see a
random funnel cloud report. Otherwise, heavy downpours and the
potential for gusty winds and small hail would be more likely in
the stronger cells. The entire swath of locally heavy rainfall
will continue advancing eastward toward the foothills/mountains
this afternoon. To the north, recent HRRR model runs have shown
indications of the Shasta County Convergence Zone setting up.
This would support an enhanced period of rainfall generally in the
vicinity of Redding. Overall, some lingering showers are possible
across Valley locations into the evening with additional chances
on Thursday given trailing cyclonic flow overhead.
Across mountain locations, the late-season winter storm is well
underway with heavy snow picking up this afternoon as the
baroclinic zone shifts focus to inland locations. This could lead
to a significant reduction in visibilities as well as hazardous
travel. Thus, as mentioned in previous messages, mountain travel
is not advised until the system clears on Thursday morning. The
S-band radar is showing initial snow levels around 5,500 to 6,000
feet. Given the arrival of colder air aloft overnight, expecting
the snow levels to drop to the 3,500 to 4,000 foot range early
Thursday. Like the Valley, numerous showers will continue into
Thursday with brief travel impacts where such precipitation falls.
When it is all said and done, elevations 7,000 feet and above can
expect 1 to 3 feet with locally higher amounts possible.
While some showers could linger into Friday morning over northern
counties (Shasta, Lassen, Tehama, and Plumas), much of the region
will begin to dry out as an upstream ridge approaches. The mean
ridge axis should settle over the state for the weekend ensuring a
dry, mild period. High temperatures are forecast to reach the low
to mid 70s over the Valley with upper 40s to lower 50s in the
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)
The extended period will start out dry with the transient ridge
maintaining its presence over the southwestern U.S. There is
decent agreement operational and ensemble model agreement that a
shortwave will reach the northwestern California coast by Monday
afternoon. An increase in cloud cover accompanied by some warm
advection precipitation is expected for Monday with snow levels
likely to be quite high, generally 7,500 to 8,000 feet. Once this
storm clears the region, model uncertainty grows as the main
operational models (GFS/ECMWF) are at odds with one another. At
the very least the models show run-to-run consistency, albeit with
different forecasts. The GFS favors a building of the eastern
Pacific ridge while the ECMWF depicts influences from a northern
stream trough. Thus, too much uncertainty exists to declare a dry
forecast into the middle of next week.
Looking ahead, the Atmospheric River Detection Tool and other
corresponding ensemble solutions are advertising a wet, active
pattern toward the end of next week and into the weekend. This has
also been highlighted in the Climate Prediction Center Day 8-14
experimental Heavy Precipitation graphics. The blocking upper high
over Alaska bounding an active Pacific jet are the key players in
the pattern change. While there is confidence in this set up,
the southward extent of its influences are a big question mark.
Ensemble probabilities remain highest between 40-45 degree north
latitudes. Will definitely be something to keep an eye on heading
to the period of April 4-8. ~BRO
Segments/lines and clusters of thunderstorms over much of
interior Norcal persisting into the evening with MVFR/IFR/LIFR
conditions obscuring higher terrain. Scattered showers and mainly
VFR/MVFR conditions for the remainder of the night after 06z.
Mainly south winds 10-20 gusts to 30 knots through 00z mainly
northern Sac Vly, then lighter south winds the remainder of the
night. Unstable air mass continues into Thu with scattered
thunderstorms redeveloping late morning/afternoon and into early
Winter Storm Warning until 5 AM PDT Thursday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.