Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/04/17
Area Forecast Discussion
National Weather Service Taunton MA
1005 PM EST Fri Mar 3 2017
.SYNOPSIS...
An arctic cold front will cross the region this evening which will
be accompanied by scattered snow showers along with a few heavier
but localized snow squalls. Behind the arctic front near record cold
and bitterly cold wind chills tonight into Sunday morning.
A significant warming trend follows early next week with
temperatures likely back into the 50s Tuesday and Wednesday,
along with a chance of showers. Colder weather returns late in
the week with a few snow showers possible Thursday night into
early Friday.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
***Localized brief heavy snow squalls continue this evening***
10pm update...
Noting the gradual development of a modest narrow inverted trof.
This is especially noticeable in local meso-obs/winds suggest
some decent convergence colocated with a narrow min in MSAS
pres. This continues to provide enough of a focus for continued
SHSN which as the trof pulls both E and S will move across
portions of E MA and RI through about 1AM. SN accums should
remain light, generally under an inch but quick accums on area
roadways cannot be ruled out as these move through.
Otherwise, forecast on track. POPs/WX are close to both
operational HRRR and experimental HRRR which are now carrying
this inverted trof well.
Previous discussion...
After analyzing all of the 12z guidance including the 12z
GFS/NAM/NAM nest/NAM nest parallel/19z HRRR & HRRRX/12zARW/NMMB/BTV-
WRF and latest RAP, good model consensus on two bands of snow
showers/squalls impacting southern New England this evening and
overnight. Hi Res models simulating very well two lines of snow
squalls currently over eastern PA and NY state. In fact noting VCTS
with these squalls earlier at ELM NY. This activity enters western
MA/CT including the Greater Hartford/Springfield area between 5 pm
and 7 pm, then eastward into RI and eastern MA including Boston 7 pm
to 9 pm and shortly thereafter across Cape Cod. Some of the guid
weakens this initial band of snow showers/squalls as it traverses
eastward especially into RI and eastern MA.
As the lead arctic short wave approaches from the west it induces a
surface wave on the arctic front over southeast NH 22z-02z with an
inverted trough extending westward into southern VT. As this
boundary and associated low level convergence slips south a new line
of squalls will likely move into northern and eastern MA including
Boston between 10 pm to 1 am. Pretty impressive how well these Hi
Res models are simulating the squalls over eastern PA and NY then
model consensus over southern New England this evening. Thus we have
above average confidence on the timing and areal coverage
(scattered) of snow showers/squalls across the entire region this
evening.
As is the case with warm season convection some towns will be
impacted while neighboring communities will be spared. While a
lot of snow is not expected, some of the more intense squalls
will result in the potential for a quick 0.5 to 1.0 inch in 15-20
mins, covering roads quickly with a light accumulation and vsby
briefly but rapidly lowering to a 1/4 mile or less. Seeing many
social media posts upstream across PA/NY of many accidents as roads
quickly become slick along with poor vsby. In addition gusty WNW
winds will accompany the squalls. Will continue to communicate these
details via our Special Weather Statement.
Then behind this arctic front very strong CAA overspreads the area
with 850 temps lowering to about -22C by 12z Sat. This will result
in temps plummeting into the teens with single digits well inland.
These frigid temps combined with gusty NW winds up to 35 mph will
result in bitterly cold wind chills from minus 5 to 5 above zero.
Across the higher terrain of the Worcester Hills to the east slopes
of the Berkshires -5 to -15 wind chills will be common.
Given the magnitude of the cold air tonight`s temps were derived
from the coldest guid sources.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Saturday...
Second surge of arctic air comes tomorrow from trailing arctic short
wave in the afternoon. Good forcing for ascent with this feature
however models are indicating a lack of low and mid level moisture
for short wave to work with. Thus models are not generating much qpf
given the lack of moisture despite steep lapse rates and strong
forcing. Will have to watch how this evolves as sometimes these
potential short waves finds a way to pool enough moisture for
scattered snow showers/squalls to materialize. For now will keep the
forecast dry but later shifts will need to reevaluate.
Behind this short wave a second surge of arctic air advects across
the region with 850 temps lowering to -22C along the south coast to -
24C along the NH/MA border. Will be interesting to see how cold the
850 temp is on the 00z observed CHH sounding Sat evening, as the
coldest 850 temp observed in the month of March is -23C (per SPC
sounding climo)! Puts into context how cold of an airmass we are
dealing with.
Sat night...
Coldest temps will be observed tomorrow night as the core of the
cold air settles over the region. Mins will range from near zero
northwest MA to the teens along the south coast with single digits
across most of the area. Mins were derived from the coldest data
sets. Given robust CAA continues especially during the evening gusty
NNW winds will yield wind chills from zero to about minus 10 with
minus 15 to minus 20 across the high terrain. Will highlight these
bitterly cold wind chills via our Special Weather Statement but may
eventually need a wind chill advisory.
Dry weather prevails but could see some ocean effect snow showers
esp in the evening across the outer Cape as winds back to about 330
degs.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights...
* Significantly milder Tue/Wed with some showers.
* Turning colder Thu night with a few snow showers possible
Details...
Sunday...
Wind chills may still be near Advisory criteria of -15 degrees in
far northwest MA early Sunday morning with 0 to -10 degrees
across all of the rest of MA, except the southeast. However, the
core of the cold air mass will be shifting offshore, which will
allow some relief from the bitter cold. High pressure overhead
coupled with the increasing March sun angle should allow highs
to recover into the 30 to 35 degree range. Those temps are still
nearly 10 degrees below normal for early March. Northwest winds
will be gusty in the east, but will be diminishing during the
day.
Sunday night and Monday...
High pressure crests over the region Sunday night...so despite
rising height fields expect a good night of radiational
cooling. Low temps should bottom out well down into the teens
across many locations. with even a few single digits expected in
northwest MA and some of the normally colder areas in southeast
MA.
A return southerly flow of air should occur Monday as high pressure
moves off the coast. This should allow high temps to recover to
the mid and upper 40s Monday afternoon in many locations. The
exception might be along the immediate coast, where sea breezes
may result in high temps struggling to break 40. Skies will
start out sunny but there will be an increase in high cloudiness
from west to east during the afternoon.
Monday night through Tuesday night...
Strong low pressure in western Ontario will be slowly heading toward
Hudson Bay as high pressure shifts farther east off the coast.
The result will be a southerly flow of much milder air into
southern New England. Best forcing will be located well to our
northwest, but warm advection should create a chance of light
showers Monday night, which could possibly start as some snow or
freezing rain near the VT/NH border.
Skies will be mostly cloudy and there is a chance of showers Tuesday,
but temperatures will climb to the lower and middle 50s. Expecting
a weak cold front to move across the region Tuesday night,
enhancing the chances of showers.
Wednesday...
There is a slight chance of an early morning shower. Then, with
increasing sunshine and westerly downsloping winds, temperatures
are forecast to climb to 55 to 60.
Thursday...
A secondary cold front is forecast to move through on Thursday.
Timing is slightly different amongst models. Highs mainly in
the 40s. By Thursday night, a brisk and somewhat unstable flow
of air will usher much colder air into the region. There is a
chance of a few snow showers. Preferred the cooler guidance, in
deference to the much colder ECMWF solution. Lows Thursday night
mainly in the 20s, except teens northwest MA and near 30 outer
Cape Cod and Islands.
Friday...
Weak high pressure will lead to a partly sunny day with highs
in the lower to mid 40s. Attention will then turn to an
approaching warm front. There is a big discrepancy in the models
for next weekend`s weather, which is highly dependent on the
timing and location of this warm front. But that is currently
beyond our forecast period.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Saturday Night/...
VFR but MVFR/IFR at times in scattered snow squalls. These
could include quick light SN accumulations on runways and brief
increases in wind gusts 30-35 kt out of the NW. Squalls exiting
RI and eastern MA by 02-03Z. Could see some lingering scattered
snow showers in northern MA till 05Z.
Sat...moderate confidence.
Mainly VFR conditions but low probability of additional snow
showers/squalls in MVFR-IFR during the morning hours. Winds
increase early Sat, 25-35 kt again.
Sat night...high confidence.
VFR but MVFR-IFR possible across the outer Cape as ocean effect
clouds and snow showers may move into that region. Gusty NNW
winds 20-30 kt.
KBOS TAF...Moderate to High confidence in TAF. Brief MVFR-IFR in snow
shower/snow squalls likely between 00z and 02z then a second
round 03z-06z.
KBDL TAF...Moderate to High confidence in TAF. Brief MVFR-IFR in snow
showers/snow squalls between 22z and 00z.
Outlook /Sunday through Wednesday/...
Sunday...High confidence. VFR other than the risk for brief
MVFR conditions across Outer Cape Cod for an hour or two Sunday
morning. Northwest wind gusts of 20 to 25 knots will diminish
during the day.
Sunday night and Monday...High confidence. VFR.
Monday night into early Wednesday...Moderate confidence.
VFR but areas of MVFR-IFR conditions in lower clouds and
scattered showers from time to time. Greatest risk for IFR and
heavier showers is Tuesday night.
Mid-morning through Wednesday afternoon... High confidence.
Becoming VFR through the region. Gusty west winds to 15-25 kts.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
*** NNW Gales, Moderate Freezing Spray & possible Arctic Sea
Smoke ***
4 pm update...
Short Term /through Saturday Night/...
Tonight...High confidence.
First surge of gales overspread the waters roughly 8 pm to 2 am from
northwest to southeast behind first arctic front. The front will
likely be accompanied by brief but intense snow squalls lowering
vsby to 1/4 mile or less at times. Improvement 2nd half of the
night. However arctic air will result in areas of moderate freezing
spray across the eastern MA waters.
Saturday...high confidence.
Second arctic front crosses the region during the afternoon with
another surge of NNW gales. Moderate freezing spray eastern MA
waters along with possible snow squalls esp offshore.
Sat night...high confidence.
NNW gales continue with core of arctic air over the MA/RI waters.
Widespread moderate freezing including the RI waters. Thus freezing
spray advisories have been expanded. Low risk for a few hours of
heavy freezing spray eastern MA waters. Given how cold and dry this
airmass will be could see shallow arctic sea smoke develop.
Outlook /Sunday through Wednesday/...
Sunday...High confidence. Freezing spray concerns should come to an
end by Sunday afternoon as the air mass modifies. Wind gusts
will also gradually diminish as high pressure slowly builds in
from the west...but still expecting small craft advisory
criteria wind gusts until mid-afternoon.
Monday and Monday night...High confidence. Winds and seas
should below small craft thresholds.
Tuesday...Marginal southerly small craft wind gusts...to near
25 kts...may develop by Tue afternoon as high pressure
continues to move east allowing for southerly gradient to
increase. 5 to 6 foot seas may develop across our southern
waters. Scattered showers.
Tuesday night and Wednesday...5 to 7 ft seas over the southern
and far eastern outer waters. West to west-southwest winds will
gust to 20-25 kt at times. Scattered showers Tuesday night and
early Wednesday morning could reduce visibilities to 3 miles or
less.
&&
.CLIMATE...
Record Low Max Temperatures for Sat March 4...
BOS...21/1896
PVD...23/1943
BDL...23/1943
ORH...19/1943
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Freezing Spray Advisory from 4 PM Saturday to 7 AM EST Sunday
for ANZ232>234-255.
Gale Warning from 7 AM Saturday to 1 AM EST Sunday for
ANZ232>234.
Small Craft Advisory until 7 PM EST Saturday for ANZ230-236.
Freezing Spray Advisory from 4 AM Saturday to 7 AM EST Sunday
for ANZ231-250-251-254.
Gale Warning from 4 AM Saturday to 1 AM EST Sunday for ANZ231-
251.
Freezing Spray Advisory from 9 PM Saturday to 7 AM EST Sunday
for ANZ235-237-256.
Gale Warning from 7 AM to 4 PM EST Saturday for ANZ235-237.
Gale Warning from 1 AM Saturday to 7 AM EST Sunday for ANZ250-
254.
Gale Warning from 4 AM to 4 PM EST Saturday for ANZ255-256.
&&
$$
SYNOPSIS...Nocera/GAF
NEAR TERM...Nocera/Doody
SHORT TERM...Nocera
LONG TERM...GAF
AVIATION...Nocera/GAF
MARINE...Nocera/GAF
CLIMATE...
Area Forecast Discussion
National Weather Service Gray ME
940 PM EST Fri Mar 3 2017
.SYNOPSIS...
Another cold front moves through early this evening, accompanied
by a few snow showers and snow squalls mainly over southern New
Hampshire into extreme southwest Maine. In the wake of this
front, the cold air will deepen across the area, with a return
to gusty winds and bitterly cold wind chills. Wind chills, if
not actual air temperatures, will fall below zero tonight across
the entire region, and stay near or below zero through the day
Saturday into Saturday night. Winds diminish somewhat on Sunday
with a warming trend into early next week. The next chance of
precipitation will be later Monday night into Wednesday, which
could start as a mixture of precipitation, but will turn to
rain as temperatures warm above normal again.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
930 pm update: The line of snow showers and squalls are
currently moving off the coast and to the south of the NH
border. Some snow showers continue in the mountains and are low
level so the radar generally can`t see them but are noted on
the obs. So will keep scattered snow showers in the mountains
for a few more hours. Input latest mesonet temp data and looks
like current forecast temp trends are very close. No other
changes attm.
7 pm update: Increased pops further over most of NH and also
into southern Maine for early this evening. Issued an SPS for
all of central and southern NH for snow showers and scattered
snow squalls over the next hour. Being these snow showers are
low level and still distant from radar, the beam overshooting
the tops of the snow showers making it difficult to discern any
heavier snow squalls embedded in the the line of snow showers
moving east. This line of snow showers is moving rapidly and
should exit off the coast by later this evening.
540 pm update: Increased pops across NH for snow showers with
highest pops across southern areas where a band of some heavier
snow squalls moving across srn VT moving east across srn NH over
the next few hours. HRRR has these snow showers moving further
east into extreme southern ME in a few hours so made some
adjustments for chance pops in these areas as well. No other
changes at this time.
At 19z...a weak surface low was over the southern Adirondacks
along the arctic boundary. NWS Doppler radar mosaic showed an
area of snow showers and embedded snow squalls with this
feature. Current isallobaric analysis and HRRR output support
this feature tracking across the southern third of New Hampshire
and extreme southwest Maine during the late afternoon and early
evening timeframe. Any accumulations will range from a coating
to an inch. Visibilities will be briefly but sharply reduced in
the snow and gusty winds. Elsewhere...I expect just a few
flurries or light upslope snow showers across the mountains. The
cold air will deepen overnight with gusty winds and falling
temperatures producing bitterly cold wind chills. Areas near
the international border will see wind chills in the advisory
range and no changes are planned for the current advisory area.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
On Saturday, gusty northwest winds will produce upslope clouds
and a few snow showers over the higher terrain with partly to
mostly sunny skies elsewhere. The core of the cold air will be
over us and even with the relatively strong early March sunshine
we`ll struggle to reach the single numbers of above zero across
the mountains with readings only in the teens elsewhere. The
northwest wind gusting over 30 mph at times will make it feel a
good fifteen or twenty degrees colder. Wind chill values may
briefly moderate above advisory threshold during the day
Saturday, before returning to advisory threshold in the northern
mountains Saturday evening.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Large, stacked low pressure continues to move away from the
region on Sunday, and this will allow for gradually warming
conditions. In fact Sunday will in all likelihood be the coldest
day in the extended period. Fair weather and even warmer
conditions are expected on Monday. A cold front will approach
from the west Monday night with very light WAA precipitation
possibly developing late at night. The airmass may be initially
cold enough for a light wintry mix or freezing rain in spots,
but rain will be the dominant precipitation type Tuesday and
Tuesday night as moist southerly flow strengthens. Fair and
cooler weather returns later Wed and lothemoks to last into
Friday.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Short Term /through Saturday night/...Mainly VFR. A brief
period of MVFR and lcl IFR is psb btw 23z and 02z Sat in snow
showers and snow squalls at KLEB, KMHT, KCON and KPSM coinciding
with the cold frontal passage. Gusty NW winds to around 25 kt
will return behind the arctic cold front overnight and persist
into Saturday.
Long Term...VFR conditions expected Sunday through much of
Monday night. MVFR to IFR conditions develop late Monday night
or Tuesday morning as mixed precipitation, or more likely rain,
moves in and continues through Tuesday night. A return to VFR is
expected on Wednesday.
&&
.MARINE...
Short Term /through Saturday night/...winds and seas steadily
increase to night behind the arctic cold front tonight. We
should see several periods of gale force gusts in the strong
cold air advection overnight into Saturday night. Along with
that will be light to moderate freezing spray.
Long Term...SCA conditions linger Sunday and Sunday night. SCA
conditions will once again be possible Tuesday through Wednesday
with a cold front.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Wind Chill Advisory until 9 AM EST Sunday for MEZ007>009.
NH...Wind Chill Advisory until 9 AM EST Sunday for NHZ001-002.
MARINE...Freezing Spray Advisory until 6 AM EST Sunday for ANZ150>154.
Gale Warning until 6 AM EST Sunday for ANZ150>154.
&&
$$
NEAR TERM...Marine
SHORT TERM...Marine
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
805 PM CST Fri Mar 3 2017
.UPDATE...
805 PM CST
Primary concern this evening is with snow potential tonight.
Shortwave riding the NW flow will move across the area with
guidance in good agreement on progressive, but rather intense
f-gen band developing in advance of this shortwave and leading to
a narrow, but potentially stout band of snow late this evening
into the overnight across the area. T/H x-sections from RAP
depict the f-gen band quite nicely with fairly strong omega within
the forecast dendritic growth zone. In addition, the forecast
strongly negative saturated EPV (less than -0.5 PVU) within the
strongest ascent indicates the potential for convective banding
and some slantwise convection. Really, other than the dry air that
must be overcome and expected short duration, conditions appear
favorable for the development of a narrow band of heavy snow.
The DVN 00z sounding was quite dry below about 825mb and quite a
bit of the lift will be spent trying to saturate and break through
this dry layer. The DVN WSR-88d since the 23z launch of the
sounding has shown saturation working down from 7kft to 4kft MSL,
so the process of top-down saturation is under way. The 00z RAP
and HRRR both have trended substantially lower with QPF over the
area tonight, perhaps responding to the 00z upper air data and the
drier air.
Despite the trend in the short range guidance toward lower QPF,
not planning to lower snow amounts of QPF any in the forecast for
tonight. Often times models, even the higher res ones,
underestimate QPF/snow in f-gen bands co-located with potential
instability. Certainly the recent trend in the models lower
confidence in max snow amounts in the band, but given the
potential for convective banding and strong ascent in the DGZ,
think its plausible that max snow amounts will exceed an inch,
with isolated 2"+ totals not totally out of the question if the
banding takes off.
Will freshen up grids and send out updates shortly, but no big
changes planned to going forecast.
Izzi
&&
.SHORT TERM...
123 PM CST
Through Saturday...
It is certainly hard to tell looking out the window at a largely
clear sky that the short term will feature a quick shot of winter
before we can trend back toward spring. A seemingly well modeled
shortwave will propagate southeast through area late tonight into
early Saturday and bring a quick shot of snow to a good portion of
the area. Some areas may not see a lot of sun, but this wave will
ride right over a significantly strengthening lower level frontal
zone such that a decent band of snowfall will setup during the
overnight hours for a least a few hours where accumulation is
expected.
The devil is in the details with regards to where this more
moderate/briefly heavy will setup and for how long, and given the
progressive nature of the wave it should not be for very long and
should shift with time. While some lighter snows are possible later
this evening after low level saturation commences, the latest short
term guidance sets this up along a Freeport-Dekalb-Joliet line after
midnight and intensifying it. A while the forcing is a bit more
progressive closer to Chicago and points east, the forcing appears
strong enough for a period of more moderate snowfall as well.
Most areas will remain under an inch, but this strongest axis could
lay down a quick inch and half in a few hour period and given the
rates and colder ground this will likely stick on the pavement.
The good news is that it will not last long. There will likely be
some lingering lighter snow after daybreak, especially for areas
farther east. Clearing skies behind the wave will bring a modest
warmup Saturday, though it may not feel a ton warmer as there will
be a stiff southeasterly wind most of the day, the best warming
being across the western and southern tier of counties of
Illinois.
KMD
&&
.LONG TERM...
315 PM CST
Saturday night through Friday...
The period will begin with a warm frontal passage by Sunday
morning, and the onset of breezy and mild southerly winds during
the day. This will all be in response to the storm system,
currently off the British Columbia Coast, digging over the western
CONUS and setting up a stout area of low pressure over the
Northern High Plains. Overall, this looks to result in highs
climbing well into the 50s across the area, albeit with breezy
southerly winds.
The Northern Plains low will shift east-northeastward into
southwestern Ontario by Tuesday evening, while deepening
substantially to a sub 980 MB central pressure, as the parent
upper trough becoming negatively tilted over the Upper Midwest.
This rapid deepening (12+ MB) of the surface low on Monday will
likely drive very strong pressure falls across much of the upper
Great Lakes region during the afternoon and evening on Monday.
This in turn would strengthen the pressure gradient over the
region and drive some strong gusty southerly winds (possibly in
excess of 40 mph) over the area Monday afternoon and evening ahead
of an approaching cold front. Temperatures in this pattern are
expected to warm into the low 60s.
The cold frontal timing from the 12z GFS is several hours faster
with the frontal passage by early Monday evening. I think this is
too fast given the rapid deepening of the low. As a result, I like
the slower timing advertised by the 12z ECMWF and GEM, which don`t
bring the frontal passage through the area until overnight Monday
night. This slower timing then would result in the better chances
for showers and thunderstorms over the area during the late
evening and overnight hours on Monday. The instability axis ahead
of this approaching front appears fairly narrow, which would only
support a short window for thunderstorms just along and ahead of
the front itself.
Cooler weather, though still above average for early March, will
shift over the area for the middle part of the week in the wake of
this system. Gusty westerly winds are likely over the area Tuesday
as deep mixing taps into stronger winds aloft. Also cant rule out
a period of light isolated showers and/or graupel Tuesday
afternoon as the cold upper trough moves overhead. However, in
spite of this possibility, we have left this mention out of the
forecast at this time.
Later in the week, around next Friday, another storm system could
take aim on the area. There is considerable uncertainty with the
pattern over the area this far out, so at this time I will just
mention a chance for rain or snow.
KJB
&&
.AVIATION...
For the 00Z TAFs...
Primary aviation concern this TAF cycle is snow tonight. Narrow,
but potentially rather stout, band of snow is expected to spread
southeast across northern IL and western IN tonight. The heaviest
band of snow is expected to be just west/south of ORD/MDW/GYY,
with the most intense snow expected at DPA/RFD tonight. Most
likely timing of the snow looks to be in the 06-12z window. Snow
should end very early Saturday morning with some lingering MVFR
CIGS probable through at least Sat morning. Light winds tonight
should become southeast and gradually increase Saturday with
at least occasional gustiness upwards of 20kt probably developing
Saturday afternoon.
Izzi
&&
.MARINE...
352 PM CST
Following the eastward passage of a surface ridge of high pressure
over the lake this evening, winds over the lake will become
southeasterly. A developing area of low pressure over the Northern
High Plains on Saturday will result in increasing wind speeds
and building waves over the western shores of the lake during the
day. This will likely lead to winds and waves reaching small craft
advisory criteria by late Saturday morning and persisting into
Sunday, especially north of Cook county Illinois near shores.
There will also be the potential for a period of low end gale
force gusts over central and northern portions of the lake
Saturday night into Sunday. It appears this window will be about a
6 hour period, with some gusts reaching 30-35 KT. Given the
marginal event, we have opted to hold off on any type of
headline, though the potential for a small gale warning cannot be
ruled out during this period.
Expect the winds to turn southerly on Sunday as the Northern High
Plains low begins to shift eastward. Southerly winds are likely to
increase to 30 to 40 KT Monday and Monday night as the low deepens
rapidly over the Upper Midwest. An associated cold front will
then shift eastward over the lake by Tuesday morning. Winds in its
wake will then become west-northwesterly, with gale force winds
remaining possible through midweek.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...Small Craft Advisory...LMZ740...9 AM Saturday TO 3 PM Sunday.
&&
$$
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Area Forecast Discussion
National Weather Service Reno NV
136 PM PST Fri Mar 3 2017
.SYNOPSIS...
Enjoy this last day of mild conditions before a moderate winter
storm moves into the region late Saturday into Sunday with gusty
winds, rain, and snow. Heavy snow is likely for the Sierra, and snow
accumulation for western Nevada is still possible by Sunday morning.
High pressure returns by mid to late next week with warmer and drier
conditions forecast.
.SHORT TERM...
Main changes to the forecast were to upgrade to Winter Storm
Warnings for the Sierra zones and to issue Wind Advisories for most
of the Nevada zones. Storm for Saturday into Sunday is still on
track to impact the Sierra and western Nevada.
High clouds are moving across northern California and Nevada today
ahead of the winter storm for this weekend. Strong gusty winds,
rain, and heavy snow are expected to disrupt travel Saturday
through Sunday so plan for delays and the potential for chain
controls and road restrictions. Those with travel plans may want
to consider completing travel by midday or sundown Saturday, or
just want until Sunday evening.
WINDS - No big changes. Wind advisories have been issued. Gusty
winds will develop ahead of and along a strong cold front that will
move through the region late Saturday night and early Sunday
morning. Winds across valley and foothill areas look on track to
reach into the 45-55 mph range while ridgetop gusts peak around 100-
120+ MPH late Saturday night into Sunday. Expect travel impacts for
high profile vehicles in addition to turbulence and wind shear for
aviation. Hazardous boating conditions are likely on area lakes so
venturing out onto the water is not advised.
SNOW - Moisture begins to push across NE California Saturday
afternoon with snowfall reaching the Tahoe Basin Saturday afternoon
and into Mono County Saturday night. The main push of snowfall will
move through quickly between about 10pm Saturday and 4am Sunday and
that is when we expect the snow levels to drop to all valley floors.
Unstable conditions will allow snow showers to persist through
Sunday night. Forecaster confidence is high for heavy snow in the
Sierra with 1 to 2 feet likely along the crest, while snow in
western Nevada is less than a guarantee at the moment. While snow
levels will be down to all valley floors on Sunday morning, the
snow may struggle to accumulate on the roads. We don`t see any
definitive mesoscale band setting up right now, but higher
resolution models such as the HRRR may be able to pick up on this
as we get closer to the event. For now, the Reno-Sparks-Carson
City may see a quick inch with the front but likely the best
chance will occur post-frontal early Sunday morning into early
afternoon where an additional inch or so is possible. North
valleys, including Stead and Cold Springs could see up to 4 inches
by Sunday morning.
Lingering light snow showers are likely Sunday afternoon into
early Monday. Additional snowfall amounts on Sunday are more
difficult to pindown as the atmospheric environment will be more
convective in nature. Impacts should be less with daytime heating
perhaps making roads warm enough to limit accumulations. Monday
will be brisk with colder temperatures and breezy westerly winds
in place. - Edan
&&
.LONG TERM...Next week and beyond...
No major changes for next week with a couple more short waves
expected to move through the zonal flow Monday and Tuesday. The
brunt of these waves will be into Oregon, but there remains the
chance for a few showers. The one Monday will be a little further
south with snow showers possible as far south as Highway 50, but
any accumulation would be light and confined to the mountains
above 6000-6500 feet. Tuesday`s is further north into Oregon with
only a few showers remaining near the Oregon border.
Ridging is expected for Wednesday and Thursday with the storm
track shifting to the Canadian border. Winds are expected to be
light with only moderate winds on the ridges. Temperatures are
expected to rise a few degrees above average by Thursday.
Friday models diverge a bit with the GFS trying to show a
weakening trough moving through while the EC holds onto a ridge
for another day or so. Ensembles support their parent solutions,
but the one feature of note they agree on is the block
redeveloping in the Aleutians. As a result, leaned a bit more
toward the GFS ideas with a slight chance of showers and a little
cooling since that position supports more troughing.
Looking ahead into mid-March, the ensembles show the block
continuing in the Bering Sea/Aleutians well into the week 2
period. This pattern is favorable for more active weather to
develop in the Sierra and Western NV. There is also a threat for
ARs (Atmospheric Rivers), with progs now indicating better
chances further south. The latitude and strength remain very much
up in the air. Bottom line, chances are increasing for another
period of active weather for the middle of the month. Wallmann
&&
.AVIATION...
VFR with high clouds through 12Z Saturday. Winds will begin
increasing on the ridges tonight with mtn wave turbulence also
increasing. Gusty winds are expected Saturday with the peak winds
at terminals during the afternoon and gusts to 40-45 kts possible.
Mtn wave turbulence will peak during this time, but LLWS is
expected to be less of an issue due to good mixing. The exception
will be KTVL where terrain channeling will result in crosswinds.
Winds will decrease some Saturday night with LLWS potential
increasing as the surface winds may decouple from the strong winds
aloft. Also, a strong cold front will bring widespread MVFR/IFR
conditions for a 3-6 hour period. These conditions may continue
in the Sierra for Sunday while the lower elevations are much more
isolated. Wallmann
&&
.REV Watches/Warnings/Advisories...
NV...Winter Storm Warning from 4 PM Saturday to 4 PM PST Sunday
NVZ002.
Wind Advisory from 4 AM to 10 PM PST Saturday NVZ003-005.
Wind Advisory from 10 AM Saturday to 4 AM PST Sunday NVZ001-004.
CA...Winter Storm Warning from 4 PM Saturday to 4 PM PST Sunday
CAZ071-072.
Wind Advisory from 4 AM to 10 PM PST Saturday CAZ070.
Winter Storm Warning from 10 PM Saturday to 10 PM PST Sunday
CAZ073.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno