Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/07/21
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1043 PM EST Mon Dec 6 2021
Gusty winds tonight will gradually diminish tonight with
lake effect snow impacting the western Adirondacks and Mohawk Valley
tonight into tomorrow. Otherwise it will turn cooler with a partly
cloudy sky. Although a coastal storm will miss the area on
Wednesday, an upper level disturbance will bring light
snow accumulations to most of the region.
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 1030 PM EST....The main area of rain has finally exited
into New England with just some lingering showers brushing parts
of the Berkshires, CT River Valley and Litchfield County. Winds
have diminished as well although NYS mesonet and ASOS
observations show some gusts still reaching up to 35 - 40mph.
These gusts will continue to diminish through the rest of the
overnight and our wind advisory will likely expire at 1 AM as
anticipated. Sustained winds will still be elevated near 8 -
The next hazard we are monitoring is lake effect snow which has
already spilled into northern Herkimer County (mainly north of
Route 28) and northern Hamilton County. In fact, lightning
strikes have occurred upstream in Lewis County from the incoming
disorganized single band. Total snow accumulations in the
western Adirondacks should range 1 to 3 inches. In addition,
there should be a decent inland extent, as strong flow aloft and
a moist multi-lake connection helps snow showers extend towards
the eastern Adirondacks.
This band may eventually start to drift southward towards the
Mohawk Valley by 09 - 12 UTC as the 925hPa winds veer to the
west-southwest. Favorable ingredient for inland extent will
still be in place and our local lake effect snow inland extent
tool suggests that the band could extent nearly 200 miles
downstream of Lake Ontario. This implies the lake effect band
not only could reach into the Capital District (esp Schenectady,
northern Albany and southern Saratoga County) but also into the
Berkshires. The high res NAM, RGEM, and RAP support this idea
and show a narrow lake effect band extending into these areas
so we expanded slight chance POPs into the northern/central Taconics
and Berkshires and even expanded chance POPs into Schenectady
County. In total, a coating to less than 1 inch for the Mohawk
Valley is possible with coatings to less than 0.5" for the
Capital District. Luckily, temperatures will only drop towards
freezing by sunrise so marginal temperatures could impede
accumulations on warmer surfaces such as roads, especially in
the Capital District.
Speaking of temperatures, overnight lows may not turn as chilly
as they could given the strong cold air advection due to
continued breezy winds tonight. Therefore, only thinking lows
fall into the mid to upper 20s for most spots with some teens in
the Adirondacks. The immediate Hudson Valley should be milder
with lows only near or slightly below freezing. Although the
winds should be drying everything out, any remaining wet
surfaces could be slick by late tonight.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Broken band of lake effect snow showers will be close to the
Mohawk Valley on Tuesday morning before lifting back northward
towards the western Adirondacks for Tuesday afternoon. Any
lake-effect should finally end by Tuesday evening, but an
additional dusting to half inch is possible in the western
Adirondacks. Otherwise, Tuesday will be fairly quiet, with a
partly to mostly cloudy sky in place over the area and much
colder temps compared to Monday. Highs will only be in the mid
20s to upper 30s. Although it will be a little breezy early in
the day, the wind will be decreasing through the day, as surface
high pressure extends into the area.
This high pressure area will quickly be departing by Tuesday
night. Although skies may initially be fairly clear in the
evening, clouds will be increasing for Tuesday night as the next
shortwave trough starts to approach. Temps will fall into the
teens and 20s early at night and then remain steady for the late
Fast, open-shortwave trough will be moving towards the area for
late Tuesday night into Wednesday. While a surface low will be
developing offshore, it will remain well too far south/east to
have a big impact on our weather. Still, enough moisture will be
in place along with the lift from the upper level disturbance to
allow for some light snow from late Tuesday night into
Wednesday. Most spots will only see a coating to an inch,
although locally up to two inches is possible across the higher
terrain. If the surface low were to track closer, parts of
Litchfield County could also see an extra inch or so. Daytime
temps will be held in the mid 20s to low 30s with the
clouds/light snow. Behind the system, clearing skies are
expected for Wed night with lows in the teens to low 20s.
.LONG TERM /THURSDAY THROUGH MONDAY/...
The weather patterns begins seasonably with even a chance for some
light showers or brief wintry mix Thursday night before a deep
longitudinal trough in the Southern Great Plains directs a plume of
mild and moisture rich air into the Northeast. This not only should
allow temperatures this weekend to rise above normal but also could
result in a period of steady/moderate rain ahead of an approaching
cold front. Drier weather then returns as high pressure builds back
into the region Sunday. Read on for details.
We start the period off Thursday as high pressure strengthens to
1030hPa overhead. Temperatures should be seasonable with highs
reaching into the 30s. As the high moves into New England, return
flow sets-up and warm air advection ahead of an approaching warm
front should allow morning sun to fade behind increasing clouds. The
best warm air advection coincides with mid-level moisture overnight
which should produce a period of showers. With surface temperatures
below freezing overnight, p-type looks like snow but the intruding
warm nose could support some sleet, especially for areas in the
Mohawk Valley and southern Adirondacks. For now, we show mainly snow
but will keep an eye on the potential for wintry mix. Even if the
column is cold enough to support mainly snow, total accumulation
amounts should be light due to limited moisture. The GFS is more
robust with QPF amounts but both the ECWMF and CMC are significantly
lighter so we sided with that side of the spectrum.
Any snow or wintry should diminish Friday morning as the best warm
air advection escapes into Northern New England with high pressure
briefly building back into place. Southwest flow and weak WAA
continues through the day on Friday with temperatures rising
slightly above normal into the upper 30s to low 40s.
Upstream in the western CONUS a positively tilted trough will be
digging into the Deep South with broad riding building across the
Eastern CONUS. This should support mild temperatures into the
weekend. A surface low developing in the Great Lakes should track
into southern Canada Friday night into Saturday with its associated
warm front pushing through the Northeast. Without a blocking high
over southern Canada, the continued warm air advection should
support rain/snow mix changing to mainly rain by Saturday. Its
associated cold front will be pushing southeastward into our area
during the day Saturday and the full longitude upstream trough
combined with a potent low-level jet ahead of the boundary should
pump moisture from the Gulf of Mexico into area. In fact, guidance
shows PWATs on Saturday ahead of the front exceed 1" and even
nearing 1.50" which is 3-4 standard deviations above normal.
Guidance also points to strong low-level convergence along the cold
front which when combined with the deep moisture should support a
period of steady/moderate rain. Still some discrepancies on the
exact time for the period of moderate rain but the general consensus
looks to be Saturday afternoon into Saturday night which is when we
placed likely and even categorical POPs. However, the CMC and ECMWF
suggest the base of the aforementioned southern stream trough closes
over the Gulf States and could act to slow down the cold front and
keep the plume of moisture over the Northeast for a longer time,
lasting into part of the day Sunday. The GFS is much more
progressive which is a known model bias. Will keep an eye on model
trends to see when, where and if the southern stream energy closes
By Sunday, high pressure behind the front builds back quickly back
into the Northeast, leaving us with drier weather. Temperatures turn
relatively cooler compared to Saturday but still look a few degrees
above normal due to westerly flow aloft.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
A cold front continues to track across eastern NY this evening
bringing with it a period of rain, MVFR ceilings, gusty winds
with gusts up to 35 - 40kts and a sharp wind shift to the west.
The steadiest rain will be short-lived, only lasting between 00
and 03 UTC before exiting east of all the TAF sites.
Visibilities during the steadiest rain could briefly drop to 2 -
3 miles but during most of the rain, visibility should remain
After 03 UTC, the steadiest rain will exit to the east and
ceilings should improve to VFR. A lake effect snow band may
briefly reach GFL or ALB between 07 and 12 UTC resulting in MVFR
ceilings/visibility but due to low confidence, we only included
a PROB30 group at ALB and introduced VCSH at GFL. After 12 UTC,
expecting VFR conditions to return.
Winds at ALB and GFL have already observed the sharp wind shift
to the west while POU and PSF will shift to the west by 01 - 02
UTC. At the time of the sharp wind shift, wind gusts could
briefly rise to 35kts and stay 25 - 30 kts through 06 UTC before
winds at all TAF sites should diminish. Sustained winds after 06
UTC should still be a bit elevated between 8 - 12kts but gusts
should diminish. Northwest winds increase again by 15 UTC with
sustained winds near 5 - 10kts and gusts to 15-20 kts.
Tuesday Night: Low Operational Impact. Slight Chance of SHSN.
Wednesday: Moderate Operational Impact. Likely SN.
Wednesday Night: Low Operational Impact. Slight Chance of SHSN.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: Moderate Operational Impact. Chance of SHSN.
Friday: Low Operational Impact. Slight Chance of SHRA...SHSN.
Friday Night: Moderate Operational Impact. Chance of RA.
Saturday: High Operational Impact. Likely RA.
Rain showers will accompany a frontal passage this evening.
Although most locations will see under a third of an inch or
rainfall, some spots within the higher terrain may see between a
half to three-quarters of an inch of rainfall. While this may
allow for some minor rises on rivers and streams, no flooding is
expected. Some ponding of water on roadways can`t be ruled out
Behind the front, cooler weather will return for tonight into
the next several days. Any precipitation over the next few days
will be light and in the form of snow. Rivers and streams will
likely be receding or holding steady. Some ice may begin to re-
form on bodies of water across the higher terrain.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
The KENX radar will be down until mid December to refurbish and
replace the pedestal.
NY...Wind Advisory until 1 AM EST Tuesday for NYZ032-033-038>043-
MA...Wind Advisory until 1 AM EST Tuesday for MAZ001-025.
VT...Wind Advisory until 1 AM EST Tuesday for VTZ013-014.
Area Forecast Discussion
National Weather Service Grand Rapids MI
1006 PM EST Mon Dec 6 2021
Issued at 1006 PM EST Mon Dec 6 2021
I have canceled our Winter Weather Advisory since the winds have
decreased significantly and while we are still getting snow bands
I do not expect snowfall to exceed more than another inch or so.
It does seem even so that the snow bands will continue over our
western 2 rows of counties into mid morning on Tuesday. The
inversion height falls from over 6000 ft now to around 5000 ft by
midnight. Winds in the cloud layer were over 30 knots at 7 pm but
should decrease to under 20 knots by 4-5 am. The wind direction in
the cloud layer will remain nearly due west too. This will mean
the snow bands will weaken over the next few hours and not get as
far inland. Even so I would think up to an inch is still possible
in the favored area south of Muskegon to I-94 and west of US-131
With temperatures falling into the upper teens by morning, I
could see some icy and snow covered roads where the roads are not
treated. This could mean a slow commute of many of us in the
UPDATE Issued at 642 PM EST Mon Dec 6 2021
I am thinking to allow the Winter Weather Advisory to expire as
scheduled at 10 pm. The snow showers have once again increased in
intensity and coverage after the lull during the mid afternoon.
Based on the latest model runs of the RAP and HRRR, seems this
increase in snow shower activity will last into the mid evening,
then inversion heights fall as the upper level flow becomes more
anticyclonic, causing inversion heights to fall. This would fit
the 10 pm timing very nicely actually.
Till then, through, the NAM shows decent lift from Grand Haven to
Hasting to Jackson in a northwest flow snow band that is already
there. I expect the snow showers to accumulate another 1/2 inch
to an inch under that snow band. Some of the snow showers have
been rather strong with visibilities under a 1/2 mile. Web cams
suggest the snow is causing icy roads when a band moves through.
The winds will continue to slowly decrease over the next few
hours but even so the cold air will continue to come in and
temperatures will fall into the teens. So, expect some icy roads
where the snow showers have been even into the morning drive time
.DISCUSSION...(This evening through next Monday)
Issued at 200 PM EST Mon Dec 6 2021
- Snow showers will continue tonight with diminishing winds
The deepening low pressure system tracking into Quebec will keep
the pressure gradient tight through the evening with a broad
cyclonic flow throughout the CWA. Cold air advection continues at
700 mb through 00z Tue which is also shown to moist through that
level. Temps are progged to be around -23 deg C at 700 mb which is
well through the DGZ. So it looks like bands of snow will continue
some of which could be briefly heavy. Where the snow
persists...several inches of may accumulate. Right now...that
looks to most likely happen over the US 131 corridor. As the
moisture depth decreases overnight...so should the snow showers.
The timing of that decrease in snow will need to be monitored as
the current expiration time is 03z for the Winter Weather
Advisory. The mixing level does decrease early tonight as the main
core of low level winds shifts east. This will allow for
gradually diminishing winds.
- South to southwest flow Tuesday night may lead to impacts
mainly north of Muskegon.
Any remaining snow showers/flurries Tuesday may start to fill
back in Tuesday night north of Muskegon as a south to southwest
flow develops and the low level convergence increases. Temps will
still be cold at 850 and 700 mb with values of -13 and -18 deg C
respectively and it is also shown to be moist. A 700 mb wave
passes through overnight Tuesday which will likely enhance the
lift. One or more bands of snow will likely develop and lead to
accumulating snow. The morning commute Wednesday could be impacted
as a result of the snow. This system could rise to the headline
level...again mainly north of Muskegon...into the Manistee
National Forest area. The moisture depth drops off considerably
Wednesday morning...thus any remain show showers should diminish
- A round of light precipitation possible Thursday
There could be some mixed precipitation on Thursday as warm air
advection strengthens during the day. Right now it could be a
rain/snow mix...however a warm layer aloft may warrant a few
hours of freezing rain which will need to be monitored. Surface
temperatures will be below freezing to start the day but are shown
to rise above freezing during the day. Thus the main window for
possible impacts would be during the morning commute if the
precipitation starts up then. With only weak omega...any
precipitation should remain light.
- A stronger system possible for Saturday
Models are tracking a fairly deep mid level wave eastward through
the Great Lakes Region Saturday. The surface wave is progged to
stay west then north of the CWA. This type of track keeps the CWA
in a warm sector. Thus we will feature mainly a rain event.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 642 PM EST Mon Dec 6 2021
Currently there is a mix of MVFR/LIFR in snow showers and
otherwise VFR cigs/vis. The snow showers will remain active from
near Holland to AZO, BTL and even JXN for the next 3 hours (03z)
and then they should seriously diminish. Once that happens, I
could see solid VFR cigs into Wednesday. Still, it is night time
and cig height typically lower at night so I did allow MVFR cigs
during the overnight at most of our TAF sites (expect LAN).
On Tuesday surface high pressure moves in so clouds will start to
break up during the afternoon. All sites should be solid VFR from
12z Tue into at least early Wednesday.
Issued at 717 PM EST Mon Dec 6 2021
As forecast the winds have decreased significantly over the past
few hours. All of our near Lake MESONET sites show significant
decreases in wind speeds. Some are marginally still getting gale
gusts but based on the trend I feel safe in taking down the gale
and replacing it with Small Craft Advisory which I continued
through Tuesday afternoon. Surface high pressure should allow
winds to be below advisory criteria by late afternoon.
LM...Small Craft Advisory until 6 PM EST Tuesday for LMZ844>849.
Area Forecast Discussion
National Weather Service Indianapolis IN
955 PM EST Mon Dec 6 2021
...Updated Aviation Discussion...
Issued at 944 PM EST Mon Dec 6 2021
Going forecast is in fairly good shape. Based on latest LAMP and
HRRR guidance, did bump min temps down a bit, primarily in the north
and northwestern portions of the forecast area. If winds drop off
more than expected near daybreak, there`s a shot that a few
locations could plunge quickly to near the high single digits in the
northwest, but increasing high cloud may counteract that a bit.
Suffice to say, a cold night is on tap across the area.
.Short Term...(This Evening through Tuesday Night)
Issued at 234 PM EST Mon Dec 6 2021
Stratocu continues to shift east with more substantial clearing
expanding in from the west this afternoon as deeper subsidence
arrives. Even with the sun...temps have not recovered much with
strong cold advection ongoing. 18Z temps were in the 30s.
In what has and will be a continued stretch of warmer than normal
weather for early December...winter makes an appearance for the next
48 hours or so across the Ohio Valley. This comes first with the
cold temperatures expected through midweek...and second and perhaps
more importantly with a small wave aloft set to track across central
Indiana Tuesday night with light accumulating snow.
High pressure over the central Plains will be the dominant feature
into Tuesday as it tracks east through the region. As mentioned
above...deep subsidence and progressively drier air are advecting
into the region this afternoon as an upper trough axis swings
through. This has led to a steady thinning of the stratocu deck
since this morning with increasing sunshine across the forecast
area. This will continue for the rest of the afternoon and into the
evening as skies become mostly clear. The main impact into this
evening will be the continued gusty westerly winds which will not
diminish until after sunset once the pressure gradient relaxes as
the high approaches. For the rest of the afternoon however...peak
gusts of 30-40mph are possible which will just make it feel all that
After mainly clear skies to start...increasing moisture aloft late
tonight and Tuesday morning will prompt a steady increase in mid and
high level clouds which will limit any filtered sunshine primarily
to the morning hours. The arrival of weak isentropic lift by late
day Tuesday immediately ahead of the upper level wave will bring the
onset of a few flurries or light snow showers. But the focus for
more widespread light snow will come Tuesday night as the wave
tracks through the area. Broad isentropic lift in tandem with a
roughly 6 hour period of deeper saturation through the column will
support a steady...periodic light snow for most of the forecast area
from the evening into the predawn hours Wednesday. Moisture and
forcing aloft are not particularly impressive and it does not appear
that the dendritic growth zone will be much if any of a factor. But
the presence of the isentropic lift along with an area of q-vector
divergence should be more than sufficient to generate an extended
period of light snow rates ending prior to daybreak Wednesday.
Ensemble support is present for the first widespread light snow
accumulation of the season for the region...with many areas
experiencing 0.5 to 1 inch by Wednesday morning. Certainly possible
that a few spots may end up slightly higher than this as well.
Considering this is the first accumulating snow for many this season
and the timing of the snow which frankly is less than ideal and will
likely create some impacts for the Wednesday morning commute...will
introduce an SPS.
Temps...cold air will entrench through Tuesday night. Low level
thermals support largely undercutting guidance Tuesday which seems
warranted with increasing clouds as well. Have highs ranging from
the mid 20s north to lower 30s south. Lows in the upper teens and
lower 20s are expected tonight with reading just a few degrees
warmer Tuesday night.
.Long Term...(Wednesday through Monday)
Issued at 234 PM EST Mon Dec 6 2021
...Moderating temperatures and rainy late week and weekend...
As Canadian high pressure shifts to the Appalachians, southerly flow
will allow for moderating temperatures starting Wednesday. By
Thursday afternoon, temperatures will return to the 40s, as a warm
front moves through. Even warmer temperatures are in store Friday
with 60 plus degree readings possible over south central sections.
Could see a rain shower or two Thursday associated with the warm
front but better chances will arrive this weekend as a cold front
approaches from the northwest and a long wave trough induces a wave
that will move along it and therefor slow it down. The front will
interact with a moist Gulf inflow and result in prolonged widespread
showers early this weekend. Will have to watch out for the potential
flooding, especially areas south of Interstate 70 where some locales
received over 3 inches of rain last night and this morning.
Confidence in when the rain will diminish and end is low but lower
PoPs next Sunday look ok. Snow could briefly mix in at the onset
Thursday and late in the weekend as the colder air returns in the
wake of the cold front.
.Aviation...(00Z TAF Issuance)
Issued at 955 PM EST Mon Dec 6 2021
* Westerly/northwesterly breezes continuing to diminish.
* Potential light snow very late in the period.
Winds have continued to gradually diminish this evening with gusts
becoming far more sporadic. This trend will continue through the
night. Winds will become far more variable late tonight into Tuesday
Mid and high level cloud will continue to increase tonight into
Tuesday ahead of the next upper level wave which may bring some
light accumulating snowfall beginning very late in this TAF period.
Will leave this to later packages as details come more into focus
Area Forecast Discussion
National Weather Service Melbourne FL
858 PM EST Mon Dec 6 2021
...Areas of Dense Fog Likely Tonight, Especially Inland...
Main weather concern and biggest forecast challenge for tonight
will once again be concerning dense fog development across the
area. An area of marine fog along the west central FL coast, from
around the Tampa area northward through the big bend region is
already starting to move onshore. Model guidance is still in
pretty good agreement showing this area of dense fog expanding as
it spreads gradually eastward with time into tonight, eventually
moving into Lake County and through the I-4 corridor from around
There is some question on how far east this fog can progress from
there through daybreak with some guidance taking it well east
toward the coast of Volusia and Brevard County through early
Tuesday morning. However, the trends in the latest HRRR runs limit
dense fog expansion to just around the I-4 corridor. However, at
this time this solution is more of an outlier and will therefore
keep areas of dense fog mentioned for much of the area late
tonight into Tuesday morning. Dense Fog Advisories will likely
need to be issued overnight, especially for inland areas where
greater coverage of fog producing visibilities of a quarter of a
mile or less will likely exist.
Those out driving on area roadways overnight should be alert for
rapidly changing visibilities and should slow down if encountering
dense fog. Those heading out for the Tuesday morning commute
should also allow for extra time to get to their destinations
where dense fog forms.
Some passing high clouds expected through tonight, with skies
mostly clear to partly cloudy before stratus and fog slowly builds
in. Any lingering showers will be limited to the offshore waters
of the Treasure Coast through late evening, with dry conditions
over land areas. Lows tonight will range from the upper 50s to low
60s over much of the area.
.AVIATION...Models in pretty good agreement with dense fog
expanding eastward from west central FL reaching KLEE near to just
after midnight. Fog will then continue to spread eastward and
should at least make it through the I-4 corridor, and potentially
as far east as the coastal TAF sites, especially from KMLB
northward by daybreak. Visibilities 1/4 mile or less and cigs
around 200 feet are generally expected with any dense fog that
forms. Fog will then lift and dissipate into Tuesday morning,
diminishing by late morning. After fog diminishes, VFR conditions
are generally expected through Tuesday afternoon.
.MARINE...Showers and isolated storms are pushing well offshore
this evening, with only a lingering chance for showers through
midnight offshore of the Treasure Coast. S/SW winds around 5-10
knots will become W/NW late tonight toward daybreak Tuesday, as a
weak prefrontal trough crosses the waters. Seas will range from
around 2-3 feet.
.PRELIMINARY POINT TEMPS/POPS...
DAB 58 77 59 81 / 0 10 10 20
MCO 61 82 61 84 / 0 10 10 20
MLB 59 79 60 82 / 0 10 10 10
VRB 62 82 63 85 / 0 10 10 10
LEE 59 80 61 83 / 0 0 0 30
SFB 60 80 60 83 / 0 0 10 20
ORL 61 80 62 83 / 0 0 10 20
FPR 60 80 62 83 / 10 10 10 10
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
852 PM CST Mon Dec 6 2021
Issued at 852 PM CST Mon Dec 6 2021
Still on track for light snow to develop late overnight into Tuesday,
with latest short-term guidance indicating the best chance for
accumulation being generally south of I-94 where 0.5 to 1.5 inches
are possible. Total liquid-equivalent precipitation amounts will be
fairly light, just a few hundredths of an inch, due in part to the
limited depth of the moist layer with this system. However this
moisture will also reside in an area of the atmosphere where the
temperatures are most favorable for max dendritic growth over a
fairly large depth, which should result in large flakes that
accumulate quickly. High-res model guidance suggests liquid-to-snow
ratios over 20:1 which seems reasonable given the thermal profile.
Latest HRRR forecast of 2" just south of and west of MSP doesn`t
sound unreasonable given these snow ratios, although still think 1"
or less should be the general rule for most areas.
.DISCUSSION...(This evening through Sunday)
Issued at 317 PM CST Mon Dec 6 2021
The two main stories for the rest of this week are warming
temperatures and multiple chances for snow. We will warm to above
normal temperatures for the mid to late part of this week. On the
precipition side there is a chance for snow on Tuesday and again
late in the week.
Monday evening into Wednesday... As our weekend system moves farther
away and high pressure moves in winds will decrease by later this
evening into tonight. Increasing cloud cover overnight should help to
prevent us from getting extremely cold tonight, but with where we
are this afternoon it will be cold. The coldest temperatures will be
where there is fresh snowpack, generally to the north of I-94. These
locations are likely to fall below zero tonight. Looking ahead to
Tuesday a quick moving system should be able to provide some
accumulating snow. Model soundings looks moist enough for snow and we
could see a few bursts of snow showers. As this system will not
linger like the weekend`s system did snow totals should remain under
an inch. Wednesday should see a break between our two chances for
Thursday and Friday... The likely more significant round of
precipitation will come on Thursday and Friday. There could be two
rounds of here with one more on Thursday and another more on Friday.
There still remains a fair amount on uncertainty with this event,
but models have been moving into better agreement on accumulating
snow. What is less certain is how much snow and where. An example of
this would be the GEFS and EPS for the Twin Cities where there are
numerous members with high snow totals and other very little
accumulation. Model trends suggest that the lower totals are less
likely, but we will have to wait and see if these trends continue
into tomorrow. Warm air advection Thursday and Friday will help bring
temperatures above normal into the upper 30s and 40s. This warm air
advection will also be a source of forcing for the snow potential.
Saturday and Sunday... While some snow from the late week system
could linger into Saturday the upcoming weekend is looking much
quieter. Temperatures will be cooler than the late week as well,
especially if we have new snow. How much new snow we get will be
important in determining if we will see normal or above normal
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 537 PM CST Mon Dec 6 2021
Main concern this period is potential for light accumulating snow
Tuesday morning. -SN could impact all area terminals, with the best
chance for any accumulation being from around MSP eastward into
western WI where a half inch to inch is possible. Snow could last up
to 6 hours but will remain light, with rates generally less than 1/2
inch per hour, and sometimes just flurries. Snow should clear out
west to east through late morning and afternoon with lingering MVFR
clouds. Winds will be relatively light so blowing snow not much of a
Light snow is expected to start right around sunrise/13Z and taper
off by 19Z or so. Rates will be light but could see accumulation of
0.5 to 1 inch. Current WNW winds will switch around from the SE
shortly after midnight, generally staying under 10kt.
/OUTLOOK FOR KMSP/
WED...MVFR/IFR cigs. Wind SE 5-10 kts.
THU...MVFR. Chc IFR/-SN. Wind SW 10-15 kts.
FRI...MVFR. Chc IFR/SN. Wind NE 5-10 kts.
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
925 PM EST Mon Dec 6 2021
A strong but moisture-starved cold front will move across central VA
and NC early tonight, then stall off the South Atlantic coast on
Tuesday. Chilly high pressure will follow and build across the
middle Atlantic later tonight and Tuesday. A wave of low pressure
will then develop along the stalled front and track northeastward
along and offshore the coast of the Carolinas and middle Atlantic
Tuesday night and Wednesday.
.NEAR TERM /TONIGHT/...
As of 925 PM Monday...
Main changes for this update was the timing of PoPs across the
forecast area, and tweaking temperatures a tad. The cold front is
currently approaching the Northern Piedmont and can be seen by
looking at surface observations and lowest level radar scans. Winds
overnight will continue to be 10 to 15 mph veering to a northerly
wind late tonight early Tuesday morning. Otherwise, the front will
make its way across the region overnight and expected to exit the
region late tonight early Tuesday morning.
Previous discussion as of 215 PM Monday...
As of early afternoon, a cold front was along the eastern slope of
the Appalachians. Radar echoes have been very weak across western
North Carolina, although this could be due to beam blockage in the
mountains. Closer to the Virginia and South Carolina radars, echoes
are more continuous. Gusty winds will continue this afternoon with
some scattered cumulus present as well as higher clouds moving in.
The HREF and latest runs of the HRRR show less rain coverage across
the Triad with coverage picking up as the front moves farther to the
east, primarily during the evening hours. This has been reflected in
the pop grids, with isolated pops for most of the Triad and
scattered pops across the rest of the forecast area, with the window
for showers only being a few hours at any location. Think all rain
should be east of the area by 2-3am, and wind gusts should continue
to a lesser extent behind the front as well. Temperatures will be
noticeably colder behind the front, with lows ranging from the
freezing mark in the northwest to the mid-40s in the southeast where
the frontal passage will occur last.
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 215 PM Monday...
While clouds will linger across the I-95 corridor around sunrise
Tuesday, the rest of the area should be mostly sunny. Cloud cover
will continue to diminish through the morning except in Sampson
county before clouds will begin to increase again from the south.
The cloud cover will develop along a wave of low pressure that will
form across today`s cold front and return back to the north Tuesday
night. Highs will be about 20 degrees colder tomorrow compared to
today, with readings in the upper 40s and lower 50s.
There should be just a slight chance of rain across southeastern
counties late Tuesday afternoon before the chance of rain spreads
across the entire forecast area Tuesday night. Have not made much
change to this part of the forecast, keeping high chance pops across
eastern counties and just a slight chance of rain across the Triad.
Lows will drop to just above freezing along the Virginia border to
the lower 40s in southern counties. Despite surface temperatures
nearing the freezing mark, temperatures will increase with height,
assuring that any precipitation that occurs will fall as rain and
not a different precipitation type.
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 355 PM Monday...
The wide weather swings continue, with cool weather mid-week
trending to well above normal by the end of the week.
Wed: The primary surface low along the front to our SW, over Upstate
SC, will continue to fill as the surface low deepens just off the NC
coast. The northern stream mid level shortwave trough should be over
the Ohio Valley/Mid South Wed morning before progressing eastward
through the Mid Atlantic region. Deepening moisture and the arrival
of DPVA and upper divergence will continue to support high rain
coverage, mainly across the S and E and less so over the NW, where
the latest model runs (including latter hours of the high res
models) continue to trend drier, with the lift focused further S and
E and less moisture penetrating into the cooler air. Will keep
chance pops in the NW, trending to likely across much of the S and E
CWA Wed. Temps should be quite frigid, with highs ranging from the
lower 40s N to near 50s S.
Wed night through Fri night: The forcing and precip will push
quickly offshore late Wed. Surface high pressure will build over the
Mid Atlantic region from the W Wed night through Thu morning, then
this ridge will move offshore Thu afternoon and night, but is likely
to leave behind a lingering cool stable pool over central NC through
Thu, with a lack of a mechanism to dislodge it. Expect dry weather
through Thu, with lows in the mid 20s to around 30 Wed night and
highs in the upper 40s to mid 50s Thu, roughly a category below
normal. The increasingly vulnerable stable pool with no parent high
for support should eventually succumb to the increasing SW flow,
with good odds for above normal temps Fri, peaking 55-68 (coolest in
the far NW where the stable air should hang on the longest),
culminating in strong mid level ridging over and off the Eastern
Seaboard by Fri night. A few light showers or sprinkles are possible
late Thu night through Fri night within strengthening WAA as the
positively-tilted but deep western CONUS longwave trough starts to
ease through the central US, with an elevated warm frontal zone
tracking northeastward through the region. Models have been
inconsistent with the degree of moisture and lift during this
period, but most recent runs generate just spotty light precip,
which is reasonable given the lingering lower surface dewpoints in
the wake of the surface ridge plus the overall weak forcing for
ascent, so will maintain just a few sprinkles or small chance of
Sat through Sun: Model solutions continue to vary for next weekend,
but they all tend to favor a deepening of the southern portion of
the trough over the lower Miss Valley, with a deepening and
strengthening WAA pattern over NC, ahead of its corresponding slow-
moving surface cold front. Will trend pops up to good chance for now
by Sat night/Sun, given the timing uncertainty of the arrival of
prefrontal showers (and perhaps a few storms), in addition to the
potential for downstream (E Gulf Coast) convection to interrupt
moisture transport into NC, possibly trimming coverage and amounts.
But if this pattern trend holds in later model runs, we`ll need
higher pops at some point. Expect highs near 70 to the upper 70s
Sat, followed by lows in the 40 to around 50 Sat night and highs in
the 60s Sun. Forecast confidence really takes a dive late Sun into
Mon, with the GFS trending dry and mild with a continental high
pressure area building in from the west, while the latest ECMWF
keeps a potent closed low drifting over the Southeast through early
next week, keeping our weather very unsettled. Will go the dry/mild
route for now, following the more consistent solutions, although the
ECMWF trend certainly bears watching. -GIH
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 730 PM Monday...
A cold front was analyzed between SIF and MTV, very near the nw part
of Forsyth Co. in the nw NC Piedmont, at 00Z. That front and
surrounding narrow band of 2500-3500 ft AGL ceilings will sweep sewd
across cntl NC early tonight: through INT/GSO through 02Z, RDU
between 02-04Z, and RWI and FAY between 03-05Z. A short period of
MVFR ceilings may consequently result at each site during those
times. The frontal passage will also be marked by an abrupt and
gusty wind shift to nwly, and also a band of showers as the front
approaches RDU/RWI/FAY. While VFR conditions are otherwise expected,
VFR stratocumulus ceilings (3500-6000 ft AGL) may linger for much of
the TAF period particularly at RWI and FAY, with some redevelopment
of MVFR ceilings probable at the latter site (FAY) by the end of the
00Z TAF period. Surface winds will also diminish overnight, as they
gradually veer from nwly immediately behind the front to nely Tue
morning, to light and variable through the day Tue.
Outlook: VFR conditions will continue into Tuesday evening before
restrictions and rain overspread the area Tuesday night into
Wednesday, with the greatest rain potential at FAY/RWI. VFR
conditions and dry weather should return for Wednesday night before
another chance of rain and restrictions returns to the forecast for
Friday and Saturday.
Area Forecast Discussion
National Weather Service Reno NV
303 PM PST Mon Dec 6 2021
A fast moving weather system will bring light rain and high
elevation snow later today through tomorrow morning. A more potent storm
will bring an increased chance for snow Wednesday night into
Thursday, with some impacts likely down to lower elevations. Sharply
colder conditions continuing into next weekend. Next week could be
quite active with potentially significant winter weather conditions.
.SHORT TERM (Through Wednesday)...
`tis the season that say farewell to our extended period of warmth and
clear skies as a noticeably more active weather pattern returns
to our neck of the woods. We will first touch on the weaker storm
which will move through this evening through the overnight hours.
A brief lull in the weather will transition to a potentially more
impactful weather system on Thursday, which will be covered more
in the long term discussion.
* Current afternoon radar and surface observation trends indicated a
large swath of light rain/snow stretching from CA across central
NV. Much of this is still virga except over higher elevations like
Mt Rose highway. Nevertheless, as the lower levels continue to
moisten through the afternoon hours, we expect this to finally
make it to the ground. Confidence is high for measurable rainfall
amounts south of US-50 where 12Z HREF guidance is on the order of
80-100% for at least 0.01 inch of accumulation around the midnight
hours. For the Reno-Carson areas, we have about a 40-60% of being
able to finally measure something in the rain gauge. Higher-end
HREF numbers suggest the highest amounts across Mono county, where
12hr totals have a 40-60% of exceeding 0.50 inches of liquid. Part
of this will fall as snow as we`ll cover next...
* After the possibility of some light showers later this afternoon
(and maybe a brief rain/snow shower or two at higher elevations
above the drier layer), hi-res RAP & HRRR guidance shows an area
of rapid cold air advection and moistening spreading southeast out
ahead of an upper level trough. While there is high confidence in
snow levels at least 7,500 feet and above, forecast soundings
(South Lake Tahoe, for example) suggest a rather substantial wet-
bulbing effect which may bring snow levels closer to 6,500 feet by
9pm-12am. With that said, don`t expect much accumulation even if
we happen to make it near lake level. Snow totals through tomorrow
look to be from a dusting to 1 inch around the Carson Range and
Sierra within the I-80 corridor (between 6500-7500ft).
Farther south, across Eastern El Dorado, Eastern Alpine, and Mono
counties, look for 1-4 inches above 7500 feet. For Mono county
above 8,500 feet, 3 to 6 inches of fresh snow will be possible.
Expect some minor impacts across higher passes and perhaps even
down to US395 in Mono county.
* Nothing too unusual with the winds for this system as the 700mb
jet is not too impressive. Ridge-top winds on the order of 30-
45mph with gusts up to 70 mph are possible. In the valleys, we`ll
remain 10-15 mph with occasional gusts up to 20 mph mainly this
afternoon prior to the precip.
Rain/snow showers ongoing across Mono and Mineral counties will
dissipate from north to south during the morning hours on Tuesday.
After this precipitation exists our area, we will see a brief lull
in the weather. Highs will be cooler on Tuesday - but still a touch
above average for most areas. At least we can say goodbye to 60s!
Tuesday night will be chilly, with widespread 20s but it won`t be
anything like the frigid temperatures we can look forward to by
late week... Brrr
.LONG TERM...Wednesday and Beyond...
Wednesday night into Thursday, a hybrid "inside slider" will move
through the region, which will drive a strong cold front across
eastern CA and NV and allow for snowfall down to all valley floors.
There is still high uncertainty in the timing and the strength of
this storm, but these sorts of systems are typically this way. Here
are the potential impacts:
* Breezy southwest to northwest winds are expected for most areas
Wednesday-Thursday with localized travel and recreation impacts.
There is a slight potential (~20%) for wind gusts up to 60 mph for
the Eastern Sierra into Central NV, especially Wednesday
afternoon. On Friday, cold north winds with low-end travel impacts
are possible along the Eastern Sierra.
* With the potential for widespread snowfall due to low snow levels
in both the mountains and valleys, and this being the first
potential for snowfall "down here" this cold season, we have
issued a Winter Storm Watch for western NV, northeastern CA, and
the Sierra Wednesday evening-Thursday night.
* At this time, the cold front and main snow band look to move
through the area Wednesday night into Thursday morning, with
residual snow showers continuing into the afternoon on Thursday.
Lake-effect snows are also possible east/south of larger area
lakes, especially Thursday afternoon/evening into Friday morning.
* The probability of seeing a least 1" of snowfall in the lower
valleys along the US-395 corridor is nearly 85%, and about 40%
for 2", which would result in travel impacts. Sierra communities
have a 30-40% chance for 6" of snowfall. Due to the mesoscale
nature of the snow band, the details of the amount of snowfall
and location will become better known in the next 12-18 hours.
Potential lake-effect snowfall Thursday evening is not included
in these probabilities.
* After the cold front passes Thursday, temperatures will plummet 15-
20 degrees, with Friday and Saturday looking quite cold,
especially in areas that receive snowfall. High temperatures
Friday in western NV and Sierra valleys look to be in the 30s.
Frigid temperatures are possible Friday night into Saturday
morning, with teens and single digits possible for western NV
valleys, and single digits to subzero temperatures in the Sierra.
* Below-average temperatures are expected this coming weekend with
another storm possible early next week. Quite a few simulations
show a slow-moving series of winter storms next week. There is
a lot of variability in model solutions, but there is potential
for significant amounts of snow in many areas and prolonged
travel disruptions. We will continue to keep our eye on it.
VFR conditions will prevail through the early evening hours with generally
light winds out of the west. However, virga and gusty ridge top
winds on the order of 50-60 kts will yield both mountain
obscurations and some mountain wave turbulence on the lee side of
ranges. Showers will begin to move into the region later this
afternoon or early evening, generally impacting terminals along
and south of a Portola/Lovelock line. While precip type will
mostly be RA, some brief mixture cannot be completely ruled out at
TRK and TVL around midnight. MMH will generally be a mixture or
all SN later tonight through the morning hours. Some uncertainty
remains about the impact precipitation will have on FG and low
stratus late overnight into tomorrow morning. At this time, will
keep MVFR cigs for RNO/CXP/MEV along with IFR vsby over the Sierra
terminals. Lower restrictions may be necessary with the 00Z or
06Z issuance, however. -Dustin
NV...Winter Storm Watch from Wednesday evening through Thursday
Winter Storm Watch from Wednesday afternoon through Thursday
Winter Storm Watch from Wednesday afternoon through Thursday
CA...Winter Storm Watch from Wednesday afternoon through Thursday
Winter Storm Watch from Wednesday evening through Thursday
Winter Storm Watch from Wednesday afternoon through Thursday
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