Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/16/21

AREA FORECAST DISCUSSION

National Weather Service Albany NY

 953 PM EST Mon Nov 15 2021

.SYNOPSIS...
Chilly weather remains with us through Wednesday, before becoming
mild on Thursday ahead of a cold front. This cold front will
bring rain showers later Thursday which could end as snow
showers over the higher terrain Thursday night. Colder
temperatures and some snow showers are expected on Friday.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
.UPDATE...
A few mostly cellular bands of snow or rain showers continue
this evening, with one long band that extends from the western
Mohawk valley southeast across central Schoharie County and then
further southeastward across northern Columbia and southern
Berkshire Counties. Temperatures have only slowly dropped due to
cloud cover and gusty northwest winds. Most locations are in
the 30s with some 20s in the higher terrain. Snow/rain shower
activity should slowly diminish overnight and gradually sink
southward as flow becomes more northwest. Gusty winds should
diminish after midnight. Higher elevations that see snow shower
activity tonight will see a light accumulation as temps there
are at or below freezing.

.PREVIOUS...
As of 4PM...our upper level trough axis has shifted into New
England with west-northwest ushering in a chilly Canadian air
mass. The combination of moist cyclonic flow aloft and lake
effect has resulted in scattered rain and snow showers for most
of the day today under mostly cloudy skies. The west-northwest
wind direction continued to direct most of the showers into the
Mohawk Valley and eastern Catskills but the tight pressure
gradient in place has tightened low level winds and these
showers have tracked well downstream into the Hudson Valley and
even the Berkshires. Latest ENX radar scans show multiple bands
heading southeastward through our area with ground truth
observations picking up a few hundredths of an inch up to
around a tenth of precipitation. While p-type in the valley has
been mainly rain, the higher terrain areas above 1500ft have
seen mainly wet snow and these bands have resulted in a fresh
coating of wet snow.

Winds have also remained breezy with gusts to 20 to 25kts and
with temperatures only in the low to mid 40s (low to mid 30s in
the higher terrain), it felt like a typical chilly autumn day.

Our trough exits into New England tonight with low level backing
to the northwest. This should redirect snow showers into our
eastern Catskill zones through 06 UTC before winds back enough
to the northwest that showers stay to the south/west of our
area. However, upper level ridging starts to rebuild into the
Northeast towards 09 - 12 UTC which should low level flow to
veer to the west enough that some snow showers return to
far western Ulster/Greene/Schoharie and even southern Herkimer
County through sunrise. However, the westerly flow will bring
in warmer air thereby reducing the delta-T between the incoming
air mass and Lake Ontario and the winds in the 925-850hPa layer
weaken. As a result, additional lake effect bands may reach into
our far southwestern zones with total snowfall amounts likely
only around a coating to a few tenths at worst. Otherwise,
temperatures tonight will be seasonably chilly with lows in the
mid to upper 20s with near 30 degrees in valley locations. Sfc
winds remain a bit breezy tonight, albeit not as breezy as the
daytime. Still, sustained winds near 5 - 9kts will provide
sufficient mixing to prevent temperatures from becoming too
chilly in the face of partial clearing skies.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
West-northwest flow tomorrow morning gradually veers to the west
through the day as flat upper level ridging from the Ohio
Valley shifts eastward. Since guidance is in good agreement that
the ridge axis remains to our west through 00 UTC/Wed, west-
northwest flow should persist most of the day, maintaining a
fetch of moisture off Lake Ontario directed down the Mohawk
Valley. High res models paint a similar solution with the
initial lake effect rain/snow showers and clouds penetrating
into the eastern Catskills Tuesday morning shifting northward
towards the western Mohawk Valley through the afternoon in
response to the wind shift. While of the guidance keeps showers
confined to the terrain areas, the HRRR points to the possibly
that a skinny band of showers could actually reach into the
Capital District towards 21 UTC. WPC QPF guidance also is in
agreement. Daytime temperatures reaching into the low to mid 40
will keep p-type as rain for valley areas but still, we
increased POPs to slight chance to account for perhaps a late
day shower near Albany. Otherwise, p-type in the higher terrain
areas of western Greene/Ulster, Schoharie County, the
Helderbergs and southern Herkimer County with upslope showers in
the southern Greens/Taconics/northern Berkshires, should be
rain/snow mix. No accumulations expected.

Otherwise, tomorrow will be another seasonably cool day with
highs in the low to mid 40s with slightly breezy winds
continuing (gusts up to 20-25mph down west-east oriented
valleys). Skies should be a mix of sun and clouds, with more sun
expected downstream of the Adirondacks and Catskills due to
downsloping effects. On the other hand, more clouds expected
where west-northwest winds maintain lake effect moisture in the
eastern Catskills, Mohawk valley into the Capital District.

Upper level ridging then builds into the Northeast Tuesday night
resulting in initially mostly clear skies which should assist
radiational cooling and temperatures dropping into the 20s for
most of the area. Coldest temperatures expected in the Upper
Hudson Valley and southern Adirondacks where skies should clear
the longest resulting in lows in the upper teens to mid 20s. Mid
and upper level clouds increase for the second half of the
night but this should only reduce the the rate of cooling.

Clouds continue increase during the day Wednesday as the ridge
axis shifts into New England and west - southwest flow ushers in
a milder air mass. Expect high temperatures in the mid to upper
40s although cool air appears to be caught in the southern
Adirondacks which could prevent highs from climbing out of the
30s. Persistent and strengthening southwest flow Wednesday
night will actually allow a non-diurnal trend with temperatures
reaching their respective lows before Midnight and then warming
up the rest of the night into the 40s. Despite the continued
WAA, guidance is in good agreement that the region stays dry
thanks to strong upper level ridging ahead of the approaching
cold front.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
A pocket of anomalously warm 850 mb temps, averaging around 8C (+1
to +2 standard deviations), is modeled to be over the forecast area
on Thursday. However, a strong cold front is expected to push across
the area from NW to SE late Thursday into Thursday night. Areas from
the Mohawk Valley to the Glens Falls area and points southeast have
the best potential for being in the warm sector during the daylight
hours, so forecast highs are well above normal in the low to mid-60s
there. Showers may spread into the southern Adirondacks by late
morning/early afternoon (although there is still uncertainty with
the timing, so highs there are expected to remain mainly in the 50s
and possibly fall during the afternoon. Models are not forecasting
any instability with the frontal passage, so thunder will be omitted
from the forecast. A sharp temperature drop and a band of showers is
likely to accompany frontal passage late Thursday into Thursday
night, with rain turning to snow across the higher terrain, and lows
falling into the upper 20s to mid-30s. Lake effect snow showers
should start up Thursday night into Friday as surface to 850 mb
delta-T values increase to 15-20C, with low-level mean wind flow
veering from westerly (favoring the western Adirondacks) to
northwesterly (western Mohawk Valley, Schoharie Valley, and eastern
Catskills). Some upslope showers are also possible across the
southern Greens. PoPs were increased over NBM values during this
time frame in these locations. Otherwise, Friday appears to be a
seasonably cool, mostly cloudy, and breezy day.

High pressure is forecast to build in Friday night into Saturday
night, with a seasonably cool but otherwise tranquil period
expected. The midlevel flow is forecast to amplify once again Sunday
into Monday, with upstream troughing inducing strengthening
low-level southerly winds and isentropic lift. Chance PoPs
return to the forecast Sunday night into Monday.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Through 00z/Wednesday...Mostly VFR conditions can be expected
through the 00z TAF cycle as ceilings are by and large expected to
remain at or above 3,000 ft. There could be some clouds that range
between 2,000-3,000ft (MVFR territory) tonight, especially at
KPSF due to upsloping.

Winds through tonight will remain out of the west-northwest 5-10
kts. On Tuesday, west-northwest winds will remain 5-10 kts with
gusts between 15-20 kts developing mid to late morning and
persisting into the afternoon.

Outlook...

Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: No Operational Impact. NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: Moderate Operational Impact. Chance of SHRA.
Thursday Night: High Operational Impact. Likely SHRA.
Friday: Low Operational Impact. Breezy. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
After a chilly and breezy start to the work week with
some valley rain and higher terrain snow showers, temperatures turn
milder by Wednesday and especially Thursday. A potent cold front
should usher in our next chance for more widespread rainfall by
Thursday night.

RH values rise to 80 to 95 percent tonight before dropping to 45
to 60 percent tomorrow afternoon. In addition, sustained west-
northwest winds tomorrow afternoon will remain elevated between
6 and 12mph with gusts to 25mph.

&&

.HYDROLOGY...
No river flooding is expected at least through Wednesday. A few
lingering lake effect rain and snow showers tonight into
tomorrow will produce an additional tenth of an inch or less of
precipitation, mainly for the southern Greens, Taconics,
northern Berkshires, eastern Catskills and southern Greens due
to upslope and lake enhancements. While rivers remain elevated
from the weekend rainfall events, the light precipitation
amounts will not raise any flooding concerns for the rivers in
the NWS Albany Hydrologic Service Area.

Our next widespread rainfall event appears to arrive Thursday
night but guidance suggests this event will be fairly progressive
which should mitigate most flooding concerns.

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.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.

&&

$$
SYNOPSIS...SND
NEAR TERM...SND/Speciale
SHORT TERM...Speciale
LONG TERM...Thompson
AVIATION...Evbuoma
FIRE WEATHER...Speciale
HYDROLOGY...Speciale



Area Forecast Discussion

National Weather Service State College PA

 1036 PM EST Mon Nov 15 2021

.SYNOPSIS...
An upper level trough will exit the region to the east tonight.
Lake effect snow showers will continue through tonight with
minor accumulations. A nice moderating trend will set in for mid
week, pushing temperatures above normal by about 10 degrees on
Wed. Cooler weather will follow another cold front later
Thursday. No big rain events are expected with the cool down.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
730 pm/0030z update... A lake-effect band remains in place this
evening from the western southern tier of NY into northern
Warren, McKean, and western Potter counties. Although the
appearance of the band looks a bit more ragged recently, we
still expect it to remain generally in its current position for
another 6 hours or so. Thus, the Winter Weather Advisory will
remain in tact.

Elsewhere, a band of lighter lake enhanced/upslope snowfall
continues to stream into southwestern Clearfield, Cambria, and
northern Somerset counties. RWIS cameras over the more elevated
terrain within this region indicates snow of very light
intensity, and if anything conditions will become less favorable
later tonight with backing flow, so we don`t expect much in the
way of accumulations/impacts. One thing we may have to watch
for later tonight over the Laurels is patchy freezing drizzle,
as the moisture perhaps becomes too shallow for ice production
in the cloud bearing layer. At this juncture, it looks like
light snow will just taper off to precipitation free conditions,
with any freezing drizzle very limited. Just the same though,
we`ll keep a close eye on it.

Generally light snow showers/flurries over the northern
mountains (east of Coudersport) and also into Clinton county
(north of Lock Haven) should be tapering down with time.

Over the Middle and Lower Susquehanna Valleys where downsloping
has taken full effect, skies should remain clear-partly cloudy
overnight.

Lows by daybreak will range from the mid 20s over the higher
terrain, to the lower 30s in the Lower Susquehanna Valley.

5 pm/22z update... We`ve issued a near-term Winter Weather
Advisory for Warren and McKean counties (mostly northern
sections of these counties) through most of the overnight hours
(until 4 am).

A steady-state Lake Erie band continues early this evening from
the western southern tier of NY into northwestern PA (Warren,
McKean, and Potter counties). Given a moist and elevated
mixed/unstable layer, little expected variation in band
placement through this evening, and occasional in-cloud flashes
seen within this band, we feel it will be intense enough to drop
locally 3-6" of snow over the next 6-12 hours. Most of this snow
is likely to fall through about midnight and be emphasized over
the higher terrain. These amounts also jive well with the
latest high-resolution model output, including the HRRR and
HREF.

This lake-effect band should begin to weaken and drift northward
during the pre-dawn hours, as the flow backs and warm advection
commences just above the boundary layer.

Earlier discussion... Upper trough axis pushing off the
northern Mid Atlantic and through southern New England.
Scattered lake enhanced snow showers persisting especially north
of I80 after a relative lull early this afternoon, likely
thanks to a fast moving secondary shortwave traversing the
region. High resolution models sharpen and solidify activity
into a few narrower bands which target Warren and parts of
McKean County this evening with some additional light
accumulations. Large scale subsidence behind the departed upper
trough has brought partial clearing to many areas east of the
Alleghenies.

NW flow regime for the rest of central/western/northern PA
through tonight with lake enhanced, orographic snow showers
across the Allegheny Plateau with boundary layer flow tapping
moisture from Lakes Huron and Erie. The fast moving shortwave
may support some brief rain or snow showers into the Middle Susq
River Valley this evening. Favored snowbelt of Warren and
Mckean counties appears likely to see an additional 1-2 inches
through early Tuesday morning.

Lake effect snow showers over northern PA dwindle and winds
diminish late tonight, as surface ridge builds in from the Ohio
Valley. Expect mainly flurries from the predawn hours until
sunrise. Mins to range from the mid 20s north to the lower 30s
southeast.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
The arrival of surface ridge should bring fair and somewhat
milder conditions Tuesday with light winds. As the high pushes
off the east coast, expect a warmer southerly return flow on
Wednesday. Large scale subsidence under upper ridge should
ensure dry weather for most of the area Wednesday. However,
models indicate a surge of low level moisture, combined with
an upsloping southerly flow, could yield some low clouds and
patchy drizzle over the northwest mountains on Wednesday.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Evening update to the long range is pretty uneventful. The rain
moving in along/behind a cold front on Thursday will not be
heavy, and the air should not get cold enough in the NW to snow
until sunset or after Thurs night. Lake effect pattern resides
for a day, but then a couple of dry days. As noted below,
another chance for precip exists early next week. It will be
interesting to watch the long range the next few days to see
just how deep the trough progged to dive down from the Canadian
Rockies will be. EC is sharper and deeper and even tilts it
negative as it swings over the eastern US. It deepens a sfc low
over the DelMarVA Mon/night (Day 7+). The GFS is slightly more
progressive with this significant long wave trough. It does not
develop anything near as powerful as the EC does, keeps it
moving, and takes any potential development out to sea. That`s 7
days away...still a long way out. Many model/ensemble runs will
be forthcoming over that time to help make the best forecast.

Prev...
High pressure and dry weather to start Wednesday will soon be
overtaken by an approaching cold front from the west, which will
lead to rain showers beginning late Wednesday/Thursday morning
and stick around all day Thursday. Cold air behind the front may
turn some of that rain into snow flurries for late Thursday
evening/Thursday night. Eventually, all precip will transition
to snow or a rain/snow mix as the system exits early Friday
morning. Lake-effect snow showers will linger in the far
northwestern counties for Friday.

Dry weather is expected for Saturday. The next system moves in
sometime during the day on Sunday bringing another round of
precipitation. The rain/snow mix will linger into the beginning
of the week.

Temperatures will vary greatly this week, with high temperatures
on Wednesday and Thursday getting into the 50s and 60s. The next
day on Friday, however, high temperatures plummet to the 30s and
40s and will likely stay there for the remainder of the period.

&&

.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Lake effect snow bands were able to get well inland from the
Great Lakes at mid evening. Bands now weakening a bit. Minor
adjustments made to the TAFS as of late evening.

Earlier discussion below.

For the 00Z TAF package, looking at some snow bands into BFD
overnight. Some light snow showers into AOO, UNV, and JST at
times. Used a TEMPO group at BFD to handle the heavier snow
showers.

VFR conditions across other sites like IPT, MDT, and LNS.

After about mid morning, CIGS will become VFR across the
whole area.

Good conditions expected for the rest of Tuesday into Wed.

Outlook...

Wed...MVFR cigs possible.

Thu...Restrictions in SHRA. Gusty.

Fri...Becoming VFR.

Sat...Dry with VFR conditions.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 4 AM EST Tuesday for PAZ004-005.

&&

$$
SYNOPSIS...DeVoir
NEAR TERM...Jurewicz/DeVoir
SHORT TERM...DeVoir
LONG TERM...Dangelo/Gutierrez
AVIATION...Martin



Area Forecast Discussion

National Weather Service Quad Cities IA IL

 542 PM CST Mon Nov 15 2021

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 221 PM CST Mon Nov 15 2021

Early afternoon temperatures ranged from the mid and upper 30s over
the northeast to the 40s and low 50s across far southeast Iowa and
northeast Missouri, where skies were mostly clear. Clouds
streaming across eastern Iowa and northwest Illinois in the
northwest flow aloft were slowly thinning. The primary NW-SE band
of F-GEN precipitation had shifted from northwest IL to an axis
from southern WI through Chicago into NW Indiana. A separate area
of warm advection/FGen that moved across southeast Iowa into west
central IL with only very light rain or snow observed today was
about to exit Bureau and Putnam counties. Further south, a warm
front was analyzed at the surface from roughly Omaha to St Louis,
marking the leading edge of breezy southwest winds and
temperatures in the 60s over MO and eastern KS. These conditions
will prevail over much of our forecast area tomorrow as the warm
front shifts northward.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 221 PM CST Mon Nov 15 2021

Temperatures are the primary challenge, with seasonably cool values
tonight, then much above normal highs Tuesday.

Tonight, the current trend on satellite showing a very gradual
eastward retreating of the NW-SE axis of low to mid level clouds
into northern IL should continue into this evening, to be then
replaced by thin high clouds in the northwest flow out of the
plains for an overall partly cloudy night. This should lead to
lows in the upper 20s to around 30 across the central and north.
The south should be bit warmer due to slightly stronger southeast
winds, holding lows in the lower to mid 30s. There is some
indication in the models suggesting enough low level saturation
north of the warm front for at least light fog and possibly low
clouds, but this fog is not expected to be significant enough of
an issue to include in the public forecast.

Tuesday, a developing frontal system advances into the plains,
leading to a broad south to southeast low level flow over the area
which essentially washes out the warm frontal boundary. Even with
shallow mixing, temperatures should climb into the low to mid 60s
south and mid to upper 50s north. This is close to the NBM highs and
for now have discounted the much cooler NAM, which appears to be
holding onto low level moisture and cloud cover limiting its highs
to the 40s north and 50s south.

.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 221 PM CST Mon Nov 15 2021

Key messages:

1) Rain chances decreasing for most on Wednesday.

2) Roller coaster temperatures for middle of the week towards the
weekend, with dry conditions.

Tuesday night-Wednesday...a cold front will be making its way across
Iowa at the start of the period and will be through most if not all
of the CWA by 12z Wed. While there will be some convergence along
the front, moisture will be the limiting factor. Model 1000-700mb RH
progs and cross sections show quite a bit of dry air in the low
levels and thus expect a dry fropa for most hometowns. PoPs have
been lowered some more and shifted slight southeast. The higher
chances (30-40%) is now south and east of a line from Keokuk,IA to
Geneseo,IL. The latest 15z RAP/12z HRRR model runs also support this
and later shifts can monitor trends to make any adjustments.
Temperatures will be warm enough for all rain and if any rain does
fall, it will be light and less than a tenth of an inch. After a
nice warm day Tuesday, 850mb temps will drop from 15C at 00z Wed to
minus 1C at 00z Thu. The CAA aloft and at the surface will keep
temperatures from rising much during the day Wednesday despite the
sunshine, with readings remaining in the 40s. Highs for the calendar
day will likely occur early in the day prior to cold front passage.

Wednesday night-Thursday...even colder air will filter into the
region with 850mb temps dropping down to -10C on Thursday. Forecast
soundings indicate deep mixing near 850mb will occur Thursday and
combined with a steepening pressure gradient will bring strong
northwest winds. The NBM has a 90% probability of wind gusts greater
than 25mph Thursday afternoon. These winds will make for a rather
chilly day and keep temperatures in the 30s.

Thursday night-Monday...winds will subside after sunset Thursday as
surface ridge axis begins to slide east towards eastern IA. With
mostly clear skies, this will set the stage for temperatures to drop
off rather quickly Friday morning into the lower 20s. Some lower
teens are not out of the question if winds remain calm and high
clouds streaming in from the west stay thin.

A nice weekend is forecast, with dry conditions and temperatures
near to slightly above normal. Another cold front is progged to move
through late Saturday night and have kept the forecast dry for now
given model timing and strength differences.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 539 PM CST Mon Nov 15 2021

VFR conditions expected next 6 to 10 hours before a MVFR deck
overspreads MLI. There are low chances for this occurring at CID
and DBQ, so added a few015 to hedge that way. Otherwise expect VFR
conditions from 16z on tomorrow at all sites. Winds could gust
into the 20kt range tomorrow afternoon as well.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...Gross
AVIATION...Gibbs



Area Forecast Discussion

National Weather Service Marquette MI

 638 PM EST Mon Nov 15 2021

.SHORT TERM...(This evening through Tuesday)
Issued at 354 PM EST MON NOV 15 2021

Water vapor imagery and RAP analysis show eastern N America troffing
shifting eastward. Upstream, trof approaching the Pacific NW will be
the next feature of interest, and it will already be an influence on
the weather here by late Tue aftn. Btwn these 2 features, mid-level
ridging is over the Rockies. LES continues off Lake Superior under
850mb temps around -9C. Locally hvy shsn continued thru the morning
hrs, mainly across Alger County where snow accumulations up to 10-12
inches occurred locally over the interior w half of the county since
late yesterday. The LES has become increasingly disorganized this
aftn under weakening low-level wind fields, resulting from
approaching sfc high pres ridge which has reached far western Lake
Superior. Lowering inversions and the negative effect of daytime
heating are also contributing to the diminishing LES.

Sfc high pres ridge will drift across the fcst area during the
night, bringing an end to lingering LES. However, it may not be
until late tonight that the last of the LES shifts offshore e of
Marquette. Additional snow accumulations should mostly be under 1
inch. Opportunity will be there tonight to get quite cold under very
light or calm wind with passing sfc high pres ridge. There is
uncertainty in how long the lake stratocu will linger under the
light wind fields. In addition, high clouds are already streaking
toward the Upper Mississippi Valley under waa regime developing well
in advance of the shortwave trof approaching the Pacific NW. Looks
like there may be a short window with limited cloud cover, and it
shouldn`t take much to get temps to fall quickly. Thus, opted to
hedge fcst toward some of the lwr guidance interior w and central
where at least some snow cover exits. Temps may tumble to the lwr
teens F at traditional cold spots.

Shortwave trof currently approaching the Pacific NW will rapidly
deepen, closing off a mid-level low over southern Saskatchewan by
Tue aftn. This low will then reach Manitoba Tue evening. At the sfc,
low pres at around 980mb will be unusually deep for that part of the
continent. As a result, wind fields will be ramping up downstream
into the Upper Lakes during the day. WAA/stability will limit sfc
wind to some degree, but mixing potential suggests gusts up to
around 35mph will be possible over the western fcst area late in the
day, particularly high terrain and areas that see downsloping with a
se wind. Elsewhere, gusts to 20-30mph should become common by
evening. WAA/isentropic ascent may generate some light pcpn by late
aftn across the w and central, though there is some question whether
this ascent will be sufficient to overcome drier air at the lower
levels before it shifts to the e. Included schc/chc pops later aftn,
highest over the Keweenaw where it appears sufficient low-level
moistening is more likely to occur. Ptype should just be rain, but
there is a small potential that evaporative cooling could support
some snowflakes for a time. Temps should reach the upper 30s/lwr 40s
at most locations.

.LONG TERM...(Tuesday night through Monday)
Issued at 334 PM EST MON NOV 15 2021

Very little change in the thinking from previous forecasts for the
long-term period. Tuesday night, a strong vertically-stacked low
will be located along the Saskatchewan/Manitoba border. This
cyclone`s LLJ will be passing over the U.P. briefly advecting warmer
air in. It still looks like there will be enough WAA forcing for
scattered rain showers to continue from tomorrow afternoon into the
evening, mainly over Lake Superior, the Keweenaw, and the eastern
U.P. After those showers lift through, models continue to show a
period of around 4-6 kft of surface-based saturation moving across
the area thanks to moist upslope SE flow off of Lake Michigan. This
means a transition to drizzle. However, seeing as temps will be
safely above freezing, this difference is purely academic. With the
ground having cooled and there likely still being at least some snow
holding on, there will probably be fog overnight as well. Have
introduced patchy fog with this forecast but would not be surprised
if it ends up being more widespread and/or locally dense. Temps will
be nearly steady in the mid to upper 30s west half and actually rise
somewhat through the night into the low to mid 40s south central and
east.

Some of that drizzle will linger into Wednesday morning over the
east half, but otherwise Wednesday looks dry. The strong low
pressure system will track eastward into northwestern Ontario on
Wednesday, dragging a cold front across the U.P. behind that front,
winds will increase, especially over the Keweenaw where a period of
30-40 mph westerly winds looks likely Wednesday afternoon and
evening.

Wednesday night, with cold air now in place (850 mb temps still look
to be around -9 to -11 C) and deeper moisture advecting in as the low
passes by to the north, lake effect snow will ramp up quickly. It
still looks like this LES will mainly impact the west wind LES belts
over the Keweenaw and far eastern U.P. through Thursday morning
before winds gradually veer around to WNW on Thursday and then NW
Thursday night into Friday. Overall this looks like a fairly
standard lake effect snow event with scattered to numerous snow
showers in the snow belts accumulating a few to perhaps locally
several inches by Friday morning. Thursday will be a blustery day
with highs struggling to get above freezing over the western half of
the U.P. Ridging building in from the west on Friday will cause the
column to warm and dry out, bringing the LES to an end by afternoon.

That ridge passes overhead Friday afternoon, quickly followed by
another strong southerly LLJ on its western periphery moving over
the area Friday night and Saturday. This will make for more breezy
conditions, especially on Saturday. There could be some rain or snow
as well, but chances don`t look too great at the moment.

Looking even further out, it still looks like there will be another
shot of even colder air early next week. Model ensemble plumes show
considerable spread, mostly due to timing uncertainty, but the
median of both the GEFS and EPS approaches -15 C by next Tuesday.
That would of course mean more lake effect snow chances.
&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 630 PM EST MON NOV 15 2021

Sfc high pres ridge will drift slowly e across the area tonight,
bringing an end to lake effect shsn. At IWD, this improvement has
already begun. Expect VFR conditions to prevail at that terminal
thru this fcst period. At CMX, conditions could fluctuate btwn
VFR and MVFR early this evening before becoming prevailing VFR
into Tue. Improvement will occur latest at SAW. Expect MVFR to VFR
conditions to prevail through the evening in scattered -shsn before
prevailing VFR settles in overnight into Tuesday. South-southeast
winds will become gusty to 25-30 kt by mid-late Tue afternoon
ahead of strong low pressure system developing over southern
Saskatchewan. Strongest winds will likely be at IWD. LLWS could
develop late in the period at CMX.
&&

.MARINE..

Winds across the lake will continue to be less than 20 kts through
midday tomorrow. Tomorrow afternoon, SE winds will increase to 20-30
kts across most of the lake, becoming gales by early evening. It
looks like there will be a short period (around 3 hours) of strong
gales to 40-45 kts north-central and east, and a brief rogue storm-
force gust can`t be completely ruled out. However, it will be a
short-lived event as winds will subside below gale force by daybreak
Wednesday. Have upgraded the Gale Watch to a Warning with no changes
to the timing or location.

There will be a period ~12 hours long Wednesday morning when winds
subside into the 20-30 kt range. However, by Wednesday afternoon, a
cold front moving across the lake will cause WSW winds to strengthen
to gales on the west half. A short period of 40 kt gales is possible
Wednesday afternoon, particularly in the favored funneling region
between the Keweenaw and Isle Royale. But outside of that short
period, these will mostly be low-end gales. Stiff westerly winds
will continue on Thursday. However, models continue to trend away
from gales. Instead, it looks like winds will be in the 30-35 kt
range with just a few gale force gusts at times, rather than
persistent gales. Winds will subside below 20 kts by Friday morning.

One more system to talk about, this one Friday night and Saturday.
It looks like there could be another brief southerly gale during
this period, similar to what`s expected tomorrow night, though at
the moment with the wind signal not as strong. Have capped winds at
30 kts during this period for now.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 5 PM Tuesday to 3 AM EST Wednesday for LSZ244-
     245-249>251-264>267.

  Gale Watch from Wednesday afternoon through late Wednesday night
     for LSZ162-240>244-263-264.

Lake Michigan...
None.
&&

$$

SHORT TERM...Rolfson
LONG TERM...RJC
AVIATION...Voss
MARINE...RJC



Area Forecast Discussion

National Weather Service Sacramento CA

 235 PM PST Mon Nov 15 2021


.SYNOPSIS...
Light showers are possible over far northern California tonight.
Areas of patchy Valley fog Tuesday morning. Breezy north to
northeast winds Tuesday into Wednesday morning. Chance of more
widespread showers Thursday into Friday.

&&

.DISCUSSION...
Areas of dense fog have mostly lifted as of 2:00 PM this
afternoon. However, cloudy conditions remain widespread across
interior northern California. Visible satellite imagery shows
increasing high clouds moving across Northern California
associated with a trough forecast to pass over the Pacific
Northwest. The tail end of this system is forecast to pass over
our area this evening. Little precip is expected with many Valley
locations remaining dry. A few hundredths are expected for the far
northern Sierra and southern Cascades.

HREF and HRRR point at the possibility for redevelopment of
Valley fog again tomorrow morning with best chances generally
along the east side of the Valley. Northerly winds are expected
to begin to increase through the Valley tomorrow morning as the
trough pushes to our east. Gusts of 20 to 30 mph are forecast
with the strongest winds expected in the Sacramento Valley.
Continued northerly to northeasterly flow overnight will limit the
potential formation of Valley fog on Wednesday morning.

By Thursday ensembles depict another trough moving across
northern California. IVT analysis shows the bulk of the moisture from
this system will stay to our west. Interior northern California is
expected to see widespread chances for generally light showers.
Snow levels are forecast to start around 6500 to 7500 feet,
lowering to 5000 to 5500 feet by early Friday morning. Uncertainty
still exists in expected precip and a few inches of snow at pass
levels can`t be ruled out.

&&
.EXTENDED DISCUSSION (Friday THROUGH Monday)...


Pacific frontal system moves through interior NorCal on Friday
bringing mainly light precip to portions of the forecast area.
Best chances for precip are in the foothills and mountains north
of I-80 in the Central Valley. Rain chances diminish by the
overnight hours Friday into Saturday. Drier and warmer weather
develops over the weekend into Monday as high pressure builds
inland.

&&

.AVIATION...


Widespread MVFR with local LIFR/IFR conditions due to fog and
stratus continue through tonight in the Central Valley. A weak
weather system will bring light precipitation chances to areas
north of Chico 01-06z Tuesday. North to northeast winds increase
after 15z Tuesday, especially in the northern Sacramento Valley,
with gusts to 20-25 kt.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$



...Update to aviation forecast discussion...



 .DISCUSSION...
Issued at 247 PM CST Mon Nov 15 2021

20Z water vapor imagery continues to show northwest flow over the
Northern and Central Plains ahead of broad low-amplitude upper
ridging over most of the western CONUS. This is ahead of an upper
trough off the coast of British Columbia and the Pacific Northwest.
Closer to the surface, dry air in the low and mid levels has kept
little more than some wispy cirrus across the area. Weak low surface
pressure has been passing through near the KS/NE border, with
southerly winds and WAA combining with plenty of insolation to bring
temperatures into the 70s faster. Have bumped highs up a couple of
degrees for today, but even this may not be quite enough.

With this in mind, have trended on the warmer side of guidance for
highs tomorrow given the continuation of WAA tonight into tomorrow
and breezy south winds. There are some indications that east central
KS could see more of an increase in clouds during the afternoon,
which could hinder temperatures if we see more cloud cover than
currently forecast. Agree with previous thinking that the NAM
appears to be overdone in its saturation of the low-levels,
particularly during the afternoon and early evening. However, based
on this and the 15Z RAP showing an increase in 925mb RH, can`t
entirely rule out the possibility of stratus moving in from
southeast KS. Am not overly confident in that scenario, however, so
overall think the entire area has another good shot at reaching the
low to mid 70s within the WAA regime.

The bigger forecast question continues to be whether there will be
any precip ahead of an advancing cold front, which is progged to
move across the area Tuesday evening and overnight. Isentropic
ascent increases ahead of the boundary in east central KS, with the
best chances of precip looking to be after 06Z if it occurs, which
is in line with the latest ECMWF. Have continued with only light
rain or drizzle given sounding profiles and weak ascent. This should
move out of the area Wednesday morning with more widespread clouds
and CAA keeping temperatures cool. Not much of a warmup is expected
with highs in the upper 40s near the KS/NE border to mid 50s
southeast of the Turnpike. It`s also worth mentioning that brisk
northwest winds at 15-25mph along with much drier air, especially in
north central KS where afternoon RH could drop as low as 25 percent,
could result in some elevated fire concerns. Confidence is low at
this time given the cloud cover and cool temperatures, but it is
something worth monitoring.

Surface ridging builds in behind the front and upper trough,
allowing for clearing skies Wednesday night and lows in the 20s to
low 30s by Thursday morning. Although the CAA should be coming to an
end on Thursday, we don`t really see any meaningful change to
temperatures again until Friday, when low-level winds turn back
around to the south ahead of a developing lee trough within zonal
upper flow. This brings a slight warm-up into the weekend before
another weak cold front on Saturday. A lack of moisture until the
boundary passes south keeps a dry forecast at this time.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 522 PM CST Mon Nov 15 2021

VFR conditions will prevail through the TAF period. Winds will
increase tomorrow with gusts up to 25 from the south at all
terminals.


&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...Picha
AVIATION...Gargan