Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/17/18

Area Forecast Discussion

National Weather Service Albany NY

933 PM EST Fri Nov 16 2018

.SYNOPSIS...
Areas of snow showers are moving across the Adirondacks
down into parts of the Capital District this afternoon with lake
effect snow showers possible for the higher terrain into tomorrow.
Otherwise, temperatures remain below normal through the weekend with
another threat for widespread light snow possible Sunday afternoon
into Monday.

.NEAR TERM /THROUGH SATURDAY/...
As of 930 PM EST, widespread low clouds persist across the
region, with only a few breaks at times. In addition, regional
radars suggest some very light precipitation, mainly flurries,
across central and northern areas, with slight enhancement
across higher terrain areas of the southwest Adirondacks and
southern VT.

Latest IR satellite imagery and both KBUF/KALY soundings suggest
cloud tops relatively warm, with little ice nuclei remaining.
So, can not rule out some spotty drizzle/snow grains in some
areas, with perhaps a touch of freezing drizzle across some
higher elevations of the Adirondacks.

With the widespread clouds and west/northwest winds from the
Great Lakes, temps may not fall off much overnight, especially
central and northern areas, where clouds and some wind should
persist. In these areas, temps have actually risen slightly over
the past few hours and expect temps to remain generally steady
overnight in the lower/mid 30s. Some breaks and lighter winds in
southern areas may allow for some upper 20s/lower 30s toward
daybreak, although if clouds persist, temps may hold above
freezing here as well.

Previous discussion follows...

GOES16 water vapor this afternoon shows an shortwave moving
eastward across Lake Erie and southern Canada. This is the
responsible lifting mechanism for the area of organized snow
showers downstream over the Adirondacks into the Mohawk Valley
and Upper Hudson Valley. The southern fringe of these snow
showers are even skirting parts of the Capital District.
Generally radar reflectivities are low ranging 15-25dbz with
the airports showing light snow and flurries although a few NYS
mesonet cameras show brief steadier bursts under the isolated
bands. With surface temperatures in these areas remaining in the
low 30s, some light accumulations are possible and updated the
latest forecast to include coatings to less than half an inch of
new snow for most areas with up to an inch in the Adirondacks.
The latest HRRR shows these snow showers exiting southern VT
and the Albany CWA by around about 00z tonight.

Zonal westerly flow continues tonight so some upslope snow
showers are possible in the typical prone areas of the
Adirondack but the air mass moving over the lakes is not
terribly cold so not expecting much assistance from lake
moisture. Some clearing is possible in the wake of the exiting
shortwave in the mid- Hudson Valley and NW CT and with snow pack
on the ground, temperatures tonight should fall into the upper
20s. Further north, flow off the lakes should keep moisture
trapped underneath the inversion giving those areas mostly
cloudy skies. Thus. there should not be much of a diurnal
temperature change and low temperatures should only fall a few
degrees into the low 30s.

Winds could be a bit breezy this evening into tonight, mainly in
areas above 1000ft, as high pressure noses into the Northeast
behind our exiting coastal storm leading to a tightening
pressure gradients. Westerly winds could gust up to 20 - 30 knots.

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
High pressure continues pushing into the Northeast with a
weakening cold front dropping down from Canada. Continued
westerly flow off the lakes should keep most areas mostly cloudy
but high temperatures should finally reach the low 40s in
valley locations with mid - upper 30s in the hill towns/higher
terrain.

The front weakens and even washes out as it drops into Upstate
NY towards 00z Sunday so we are not expecting much in the way of
precipitation.

However, there should be reinforced shot of cold air advection
behind it and with 850mb isotherms near -10C to -13C moving
over Lake Ontario where water temperatures are near +9C, there
should be a strong enough temperature difference that lake
effect snow showers become possible. The latest guidance shows
potential for a single lake effect band to develop overnight. We
have coordinated our POPs, QPF and snow amounts well with BUF
and BGM to represent the potential snow accumulations in the
typical lake effect prone regions where 1 - 2 inches look
possible.

Cold air advection overnight should allow temperatures
to fall into the 20s for most areas in the Albany CWA so any
snow melt that occurs during the day could refreeze into ice on
any untreated areas.

By Sunday, high pressure should take control of the area and end
the lake effect threat. Upstream, a broad longwave trough over
southern Canada should deepen allowing westerly winds over
eastern NY/western New England to back to the southwest. This
should lead to weak isentropic lift and warm air advection and
with the washed out front from Saturday night stalled over New
England down into NYC, we could see the leftover baroclinic zone
strengthen. At 500mb we see a weak shortwave within the broad
trough head into the northeast which could allow a weak wave of
low pressure to develop along this stalled boundary. The latest
ECMWF and GFS are in agreement with a broad area of light
precipitation developing and spreading northeastward into the
mid-Hudson Valley and western New England Sunday afternoon into
Sunday night. With temperatures in the mid-upper 30s and dew
points in the 20s, wet bulbing processes could allow
temperatures to drop to near freezing leading to a broad area
of light snow. While moisture is not terrible high with QPF
amounts generally around a tenth to less than two tenths of an
inch, this set up could lead to a period of light snow with
snow accumulations possible, especially as we head into the
night time hours. We will continue to monitor this next snow
potential in future updates.

.LONG TERM /MONDAY THROUGH FRIDAY/...
Much of the long term will be dominated by a reinforcing broad upper
level trough across the Great Lakes/northeast U.S., favoring below
normal temperatures and generally dry conditions outside of some
possible Lake Effect snow showers and any snow showers
associated with individual upper level impulses/cold fronts
passing through.

One such upper level disturbance should be exiting southern New
England Monday morning, with some rain/snow showers lingering across
the mid Hudson Valley and NW CT. Another approaching disturbance and
Lake moisture may bring snow showers to mainly the western
Adirondacks later in the day. Otherwise, chilly with daytime highs
in the mid 30s to lower 40s in valleys, and mid 20s to lower 30s
across higher terrain.

The biggest uncertainty during the long term will be regarding a
stronger disturbance which amplifies the upper level trough, with
the 12Z/16 GFS favoring an earlier passage for Tuesday/Tuesday
night, with an ensuing cold outbreak for Tuesday night-Wednesday,
while the 12Z/16 ECMWF is about a day later, with the coldest air
passing across the region Thanksgiving Day. Have sided with a blend
at this time with the coldest temps Wednesday, with subfreezing
highs regionwide, with teens/20s for higher terrain, and 20s/lower
30s for valleys, and overnight lows mainly in the single digits and
teens for Tuesday night/Wednesday morning, along with some wind.
Slight rebound forecast for Thursday with highs mainly in the 20s
and 30s, and overnight lows still in the teens for most areas.
However, should the ECMWF prove correct, much colder max temps,
mainly in the teens and 20s, would be possible Thursday.

Also, depending on the timing of the upper level shortwave and
attendant cold frontal passage, snow showers will be possible,
especially across the southern Adirondacks, with timing favoring
mainly Tuesday night-Wednesday evening.

Slight moderation expected for Friday as heights gradually build,
with highs mainly in the 30s to lower 40s, and overnight lows mainly
in the 20s Friday morning.

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Low pressure will track into the Canadian Maritimes tonight into
Saturday.

For KGFL, KALB and KPSF, areas of low clouds will persist much
of the night, although Cigs will likely vary between MVFR and
VFR (cloud bases generally 2500-3500 FT AGL). Some flurries will
be possible at times, but not expected to reduce visibilities
or accumulate.

These low clouds may linger well into Saturday, especially at
KPSF, where occasional MVFR Cigs will remain possible.

At KPOU, after some lower clouds this evening, clearing is
expected later tonight through Saturday.

Winds will increase from the west to northwest at 5-10 KT
tonight and continue into Saturday. Some gusts up to 20-25 KT
could occur, mainly at KALB and KPSF.

Outlook...
Saturday: No Operational Impact. NO SIG WX.
Sunday: Low Operational Impact. Slight Chance of SHSN.
Sunday Night: Moderate Operational Impact. Chance of SHSN.
Monday: Moderate Operational Impact. Chance of SHRA...SHSN.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Low Operational Impact. NO SIG WX.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: No Operational Impact. NO SIG WX.

.FIRE WEATHER...
Areas of snow showers are moving across the Adirondacks
down into parts of the Capital District this afternoon with lake
effect snow showers possible for the higher terrain into tomorrow.
Otherwise, temperatures remain below normal through the weekend with
another threat for widespread light snow possible Sunday afternoon
into Monday.

.HYDROLOGY...
Mainly dry through early Sunday outside of lingering snow
showers in the higher terrain. Another system has potential to
bring some light snow to portions of the area Sunday afternoon
into Sunday night.

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

$$
SYNOPSIS...Speciale
NEAR TERM...KL/Speciale
SHORT TERM...Speciale
LONG TERM...KL
AVIATION...KL/JPV
FIRE WEATHER...Speciale
HYDROLOGY...Speciale

Area Forecast Discussion

National Weather Service Caribou ME

817 PM EST Fri Nov 16 2018

.SYNOPSIS...
Low pressure near southwest Nova Scotia this eve move toward the
eastern Maritimes. After a break between systems, a cold front
will cross Saturday night and bring more Arctic air for Sunday
and early next week.

.NEAR TERM /THROUGH SATURDAY/...
815 PM Update...Decided to let the Winter WX headlines expire
for all but the far northern zones as steadier snow has been
winding down. Another batch of light snow will move across the
region through midnight. This area of snow can be seen on the
latest radar is indicative of a sfc trof extending back from the
primary low moving across Nova Scotia. There is an area of llvl
convergence showing up across the eastern 3rd of the CWA. The
snow could be briefly heavy as it hits this area through late
evening w/up to a fresh 1-2 inches of snow. Temps were adjusted
to match the current conditions. Some freezing drizzle was being
reported around parts of the CWA. The 00z CAR RAOB and RAP
soundings show fzdz to be a possibility w/a warm layer at
850-700 mbs. Therefore, freezing drizzle was added for the
northern and central zones through midnight.

Previous Discussion...
Hvy sn banding from the dynamic lift ptn of this event is
already exiting E into New Brunswick. Following a brief break in
snfl erly this eve, a pd of steady lgt sn later this eve into
the ovrngt will return across the N associated with a weakening
trowal zone crossing this ptn of the FA from QB prov. Elsewhere
across Cntrl and Downeast areas, sn is in the process of winding
down to sct sn shwrs, with advs/wrngs to be dropped shortly.
Some places will receive upwards to 10+ inches in the wrng area,
but most lctns will receive between 6 to 10 inches.

Steady snow across the N will taper off to sct sn shwrs late
ngt, ending at most lctns, xcpt the mtns of the NW where isold
to sct sn shwrs will be possible into Sat. Otherwise, the
immediate air mass behind the departing storm will not be as
cold as the one preceding it on Sat, allowing for "milder" but
still below avg hi temps. A cold front with colder semi-arctic
air will cross the region Sat ngt.

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Sunday will be nearly 10F colder then Saturday with CAA, with
building high pres and subsidence reducing cloud cover in
comparison to Saturday. Temperatures plummet initially Sunday
night, but clouds increase later in the night with an
approaching shortwave moving northward in the southern stream.
Some light snow could break out towards Bangor and the Down East
region later in the night towards daybreak. Further north in
the Saint John Valley, lows will drop into the single digits.

At this point, it looks like weak cyclogenesis could occur
towards Washington County Monday morning as the southern stream
system starts to phase with a northern stream shortwave and
associated Arctic front. The system is moving fast so looks like
a light snowfall event at best. Confidence still remains low
with spread continuing but have trended pops up a little with a
little more agreement. Still looks like high end guidance only
has 2 to 3 inches of snow across Washington County.

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Record Cold Threat for Holiday Week...
Arctic air builds behind the front Monday night and will likely
be locked in place until the end of the week with abnormally
cold temperatures and no major weather systems. With that being
said there is still some big spread in the Tuesday to Wednesday
period in regards to an arctic front/Alberta clipper system.
This pattern has the potential to impact holiday travel, so will
watch closely. Kept chance pops going with so much spread in
this period and below average confidence. Confidence remains
high on the potential record cold with the NAEFS percentile
graphics already showing 30 year return interval frequency for
850 and 700mb temps.

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
NEAR TERM: VLIFR Nrn TAF sites to IFR Downeast sites in sn will
make slow improvement to IFR Nrn TAF sites and MVFR Downeast
sites ovrngt in lighter sn/sn shwrs and then to MVFR/low VFR
clgs Nrn TAF sites and VFR Downeast sites on Sat.

SHORT TERM: All sites will become VFR Sunday afternoon and
evening. Another round of MVFR tempo IFR occurs for all sites
later Sunday night into Monday morning due to cigs and
snow,threat looks highest at KBHB and KHUL TAF sites. No major
storms expected Thanksgiving holiday week, but there could be some
weak Alberta clipper waves that could bring tempo IFR
conditions at times.

.MARINE...
NEAR TERM: The gale wrng has been dropped in lieu of an SCA for
all of our waters xpctd to cont til at least late Sat aftn. Had
to lean more with higher WW3 wv guidance to cvr very hi seas ovr
the outer waters this while retaining NWPS wv guidance for the
immediate coastal waters area, trending more toward NWPS late
tngt and Sat.

SHORT TERM: No significant coastal low pressure systems are
expected over the waters Sunday through mid-week. Some SCA
conditions are possible behind some cold fronts on Monday night
and maybe again on Thursday put confidence is still very low at
this point.

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Warning until 2 AM EST Saturday for MEZ002.
Winter Weather Advisory until 2 AM EST Saturday for MEZ001.
MARINE...Small Craft Advisory until 6 PM EST Saturday for ANZ050>052.

Near Term...Hewitt/VJN
Short Term...Dumont
Long Term...Dumont
Aviation...Hewitt/VJN/Dumont
Marine...Hewitt/VJN/Dumont

Area Forecast Discussion

National Weather Service Detroit/Pontiac MI

617 PM EST Fri Nov 16 2018

.AVIATION...

MVFR to lower VFR stratus will remain locked over area overnight
into Saturday with cold westerly flow off of Lake Michigan. This low
level moisture will be further enhanced for a time on Saturday as a
passing shortwave leads to a period of fgen forcing and resultant
light snow. In the wake of this system, winds will veer to the
northwest and cigs may edge up just a bit within subsidence region.
Best chance for -sn remains focused over/south of the I-94 area.

For DTW...Ceilings aob 5000 feet will persist through the forecast.
After lifting into the 3500 foot range overnight, expect a lowering
back to 2500 feet or less with light snow on Saturday. WSW flow will
veer to NW late in the forecast with the passing front that brings
this -sn.

.DTW THRESHOLD PROBABILITIES...

* High for ceilings aob 5000 ft throughout the forecast.

* High for precip type of snow on Saturday.

.PREV DISCUSSION...
Issued at 251 PM EST Fri Nov 16 2018

DISCUSSION...

Cold temperatures (around 10 degrees below normal) through the
Weekend, with even colder air spilling in early next week.

Temperatures have been struggling to respond today (should
still top out in mid/upper 30s vs normal highs in upper 40s), as
lingering cold low level cyclonic flow even allowing for pockets of
drizzle early this afternoon. Continuing drying of the mid levels,
lower inversion heights and increased mixing depths this afternoon
will diminish cloud depths, which should allow drizzle to wane, but
clouds likely holding through the night, holding temps mainly above
30 degrees.

Shortwave exiting the Dakotas this afternoon appears to be dampening
out within the strong westerly flow as it moves through the Great
Lakes region tomorrow. The trend of the low level circulation/ripple
moving through the Midwest is farther south, as weak surface low
reaches western Ohio River Saturday afternoon, far removed from the
upper level support (700-500 MB) which is closer to the southern
Michigan border. Lift over southern Lower Michigan looks modest, and
main thing we got going is moisture advection, as 850-700 MB
increases to around 3 g/kg, with the axis along and south of I-94.

Will adjust the higher snow pops toward the south, and still think
we will be hard pressed to see much more than a dusting to 1 inch
with just 2-6 hours of weak forcing to work with. Latest Ruc holds
off snow until around noon across the bulk of southeast Michigan,
and if that is the case, there really will be minimal impacts on the
highways as temps should be above freezing. Have also noted the 12z
Euro has backed off on QPF as well.

Pronounced surface ridge/bubble high to build in Saturday night,
allowing winds to go calm. The question is will Lake Michigan clouds
retreat closer to Lakeshore, allowing southeast Michigan to become
mostly clear, and thus allowing temps to dip into the teens across
the normally colder locations. Otherwise, if some clouds work
through, flurries are not out of the question with optimal 850 MB
temps around -10 C. Low level lapse rates really steepen up during
the day on Sunday, and NAM soundings even indicating some marginal
CAPE, but below the -10 C isotherm, so thinking there may be a cu up
at worst, as temperatures climb predominately into the mid 30s. Will
have to watch potentially active FGEN zone just south of the
Michigan border during Sunday, as shortwave through tracks through
the Midwest.

Amplifying Longwave Trough over the Great Lakes Region on Monday,
with high pressure descending from the Arctic Circle tracking into
the northern Great Lakes Monday night, resulting in 850 MB temps
lowering to -10 to -14 C by Tuesday morning over Lower Michigan. As
usual, cloud cover will ultimately determine if we fall into the teens
or hold in the lower 20s.

Continued cloud cover Tuesday and northwesterly flow bring another
round of below- normal temperatures with daytime highs peaking in the
upper- 20s to mid-30s across the state, before dropping down into
the teens to lower-20s for overnight lows. Flow is expected to turn
more zonal into Wednesday which will moderate temperatures slightly,
allowing slightly warmer westerly flow to increase temperatures into
the 30s across SE MI. Increased subsidence from an advancing high
pressure system and advent of dry air in the low to mid-levels will
also bring the chance to see some sunshine peak through the clouds
during the later part of the day Wednesday.

Moderate to high confidence to see a pattern shift starting Thursday
onwards as a shortwave trough carves across the Plains and sets up a
ridge of higher pressure across the Midwest, which will act to bring
temperatures back to normal for mid to late-November. While the GEFS
ensemble members were not on board with the warmer trend yesterday
at 12Z, today`s 12Z run displays a warming trend in the 40s Friday
and into the weekend. ECMWF runs have showed a warming pattern for a
better part of the week now and continue to show temperatures
peaking in the 40s Thursday into the weekend. 00Z ECM MOS guidance
is the most aggressive with temperatures, hinting at upper 40s to 50
degrees Thursday and Friday for the Metro region. For official
forecast, will stay slightly conservative with forecasted
temperatures in the low to mid-40s but will bump up temperatures in
the coming day if persistence between model runs hold over the next
24 hours. Increased subsidence from high pressure will also aid in
reducing cloud cover, bringing increased chances for sunshine during
the later part of next week.

Increasing pressure and dry low to mid-levels will keep
precipitation chances minimal during the midweek period. Slight
chance to see precipitation leading into next weekend, however, not
enough convergence is seen between model runs to accurately pinpoint
PoP and location at this time.

MARINE...

Departing low pressure to the northeast will lead to continued west-
northwest winds over the waters tonight, gusting to near gale force
this evening and weakening overnight. Elevated wave action in outer
Saginaw Bay and the nearshore waters off the northern Thumb will
result in hazardous small craft conditions through Saturday morning.
Winds and wave action will weaken by Saturday as high pressure
builds into the region from the west. Northwest flow will persist,
peaking around 20 kt during the afternoon. Scattered snow showers
will be possible over the lakes late tonight through Saturday before
conditions dry out Sunday. Southwest winds will pick up over Lake
Huron on Sunday as the pressure gradient tightens ahead of an
approaching cold front, and gusts to 25 kt will be possible during
the afternoon and evening.

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 7 AM EST Saturday for LHZ421-441.

Lake St Clair...NONE.
Michigan waters of Lake Erie...Low Water Advisory until 10 PM EST this evening for LEZ444.

AVIATION.....DG
DISCUSSION...SF/AM
MARINE.......TF

You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.

Area Forecast Discussion

National Weather Service Quad Cities IA IL

845 PM CST Fri Nov 16 2018

.UPDATE...
Issued at 831 PM CST Fri Nov 16 2018

First, have expanded the winter headlines to the south and east
with a later expiration time.

RAP trends so far this evening shows the snow roughly corresponds
to the 295K omega and 290K cdef surfaces. An interesting trend
has been for an area of stronger forcing to develop between
highway 30 and I-80 in central Iowa shortly after midnight that
propagates eastward through sunrise. More recent trends the past
two RAP runs has been for this forcing to get even stronger. Even
with road temperatures right around freezing this strong forcing
suggests a potentially higher snowfall rate for a time that should
allow accumulation on roads.

Given this and the fact it is an early season event, the areal
and temporal coverage of the headlines was expanded to the south
and east.

Precipitation trends will need to be watched the remainder of the
night for any possible expansion in the winter weather headlines.

.SYNOPSIS...
Issued at 303 PM CST Fri Nov 16 2018

Low clouds were finally eroding from southwest to northeast
across the area at mid afternoon. The clouds have held
temperatures in the 30s across the north and east, while readings
have warmed into the lower 40s in the south and southwest under
the weak November sunshine and light westerly winds. Satellite
water vapor imagery showed a shortwave upstream in the northwest
flow entering the Dakotas, where snow was falling in a NW to SE
axis from ND across eastern SD into SW MN. At the surface, low
pressure was deepening over the NE panhandle with strengthening
pressure falls over eastern NE, where temperatures were in the
upper 50s.

.SHORT TERM...(This Evening through Saturday)
ISSUED AT 303 PM CST Fri Nov 16 2018

Main focus is on the well advertised storm system approaching
from the plains that will bring a quick shot of accumulating snow
as it passes through tonight through early Saturday. This system
system has shifted further south in the latest model runs, which
so far appears to be valid based on current trends. Thus, a
winter weather advisory has been issued for late this evening
through overnight along the Iowa highway 20 corridor from
Independence to Dubuque, where confidence is highest for amounts
closer to 3 inches.

An area of upper level divergence in the right entrance region of
a strengthening 300 mb jet moving across MN into the Great Lakes,
and low level frontogenesis along the baroclinic/thermal axis in
place from the Dakotas SE through the Mid MS River Valley, were
closely correlated with the current snow on area radars. These
features will be the primary driver of the light snow that will
spread into northern IA this evening and then eastern IA,
especially between 03z and 09z tonight. The mid level shortwave
appears more channeled in the flow as it tracks further north,
focusing its lift across MN and southern WI overnight.

The best overlap of these features, with a few hours of strong
lift in the dendritic growth zone transitions from northern IA
into east central IA, roughly NW of an axis from Cedar Rapids to
Dubuque between midnight and 4 am. This should result in a quick 1
to 3 inches of snow with the greatest potential for 3 inches
still in the NW. Thermal profiles and surface temperatures close
to 32 suggest snow will be wet and possibly mixed with rain at the
onset over east central IA, which may eat into potential snow
amounts. With little sunshine today and the recent stretch of
well below normal temperatures, the light snow may lead to slick
roads.

Further south and east, the forcing will be weakening as it
transitions south and east toward sunrise, limiting snowfall
amounts to generally less than 1 inch along and south of I-80.
Light additional amounts will be possible Saturday morning, but
temperatures will be more marginal for accumulations before colder
air begins to filter southward into the region with brisk north
winds by afternoon ahead of the next strong high building into the
northern plains. Lingering weak lift continues in the far south
through the day, where precipitation will likely change to rain as
temperatures climb into the mid 30s.

.LONG TERM...(Saturday Night through Friday)
ISSUED AT 303 PM CST Fri Nov 16 2018

Saturday Evening and Night

700mb confluent flow and frontogenesis, combined with moisture
advection downstream of a positively tilted trough over Colorado,
may produce a narrow band of snow across the southern CWA; generally
along and south of highway 34 (west of Galesburg, IL) from Saturday
afternoon into Saturday night.

If the signal from the models remains consistent over the next 1-2
runs, we will have to increase chances for snow and bump up the
accumulations. With that said, the NAM is an outlier keeping the
majority of the precipitation south of the forecast area. Will wait
for a little better model agreement before going with likely wording
and any accumulations above a dusting to a half inch. The higher end
potential at this point is 1-2 inches.

Sunday On

Quiet travel weather is expected across much of the Upper
Mississippi Valley through Thanksgiving Day.

The northwest flow pattern from Sunday through early next week is
forecast to break down by Thanksgiving as an upper-level ridge
overspreads the Central U.S. After starting below normal in the
beginning of this period, temperatures will moderate into the middle
to end of next week. Uttech

.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
ISSUED AT 533 PM CST Fri Nov 16 2018

An approaching storm system will take VFR conditions across
eastern Iowa and deteriorate them to MVFR and then IFR conditions
by 12z/17 with accumulating snow. KCID/KDBQ/KMLI are expected to
have the biggest impacts with SN from this storm. After 15z/17
conditions will slowly improve to MVFR as the SN slowly ends.

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Weather Advisory until 8 AM CST Saturday for Benton-Cedar-
Clinton-Iowa-Jackson-Johnson-Jones-Linn.

Winter Weather Advisory until 8 AM CST Saturday for Buchanan-
Delaware-Dubuque.

IL...Winter Weather Advisory until 8 AM CST Saturday for Carroll-Jo
Daviess-Stephenson.

MO...NONE.
&&

UPDATE...08
SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...Uttech
AVIATION...08

Area Forecast Discussion

National Weather Service Sioux Falls SD

522 PM CST Fri Nov 16 2018

.SHORT TERM...(This evening through Saturday)
Issued at 355 PM CST Fri Nov 16 2018

Current surface analysis shows the leading edge of the cold front on
the northern fringe of our forecast area. The upper wave has moved
into our western zones and is best followed by using 700-500mb QG
forcing. The current band of snow extending from north central SD to
the northern sections of southwest MN is indeed lining up right
along the 750mb frontogenesis where moisture is maximized in the
middle of the saturated layer through 6km. Checked for elevated
unstable EPV* near 700-650mb and aside from perhaps right now, there
is not a lot of banded instability this evening across our north and
northeast zones where moisture is the deepest. What we do have
aiding ascent is a jet streak over northern WI which is placing the
forecast area in a right entrance region into the overnight hours,
sluggish to leave our far eastern areas.

This evening, the aforementioned QG forcing moves into southwest MN
and exits through extreme northwest IA close to the IA Great Lakes
region. Frontogenetic forcing in the 850-750mb layer remains very
strong in these locations below the QG forcing, with saturated
levels through 6km. Some of the newer cams such as the HRRR, as well
as the RAP and NMM really crank up the QPF on the eastern edge of
our forecast area this evening as the dynamics becomes coincident
with the deep layer moisture. Therefore decided to add Murray and
Jackson counties to the winter weather advisory and will have to
keep an eye on Dickinson county in far northwest IA. One more item
is how terrain may play into snow accumulations. With a north to
northeast low level wind component, we do have an upslope flow along
and north of the Buffalo Ridge in southwest MN. There could be a
very narrow local enhancement of snowfall in that area and manually
drew in this possibility of increased QPF, which is another reason
to add Murray county MN. As the cold front moves through, winds will
increase dramatically into the 20 to 30 mph, perhaps gusting as high
as 35 mph, which could create localized blowing snow conditions
during falling snow. In addition, lows will plummet into the teens,
perhaps near 20 at Sioux City and Storm Lake.

Cold air advection stratus may linger Saturday morning over many
areas. Not sure if the stratus layer is deep enough to produce
flurries, but it is -12 to -14C in the cloud layer so there could be
a few flurries around. At this time due to the thin stratus deck,
decided not to include a few flurries Saturday morning but it
certainly could happen with no accumulation whatsoever. Temperatures
will be so to climb with only upper teens to mid 20s, with morning
wind chills a bit below zero north of I 90.

.LONG TERM...(Saturday night through Friday)
Issued at 355 PM CST Fri Nov 16 2018

On Saturday night, lows will be cold, but how cold is rather a
question mark. The northeast half of our forecast area will likely
have snow cover. However as the 1040mb high exits to the south, our
winds begin to turn around to the southwest over locations which
will have bare ground. Therefore temperatures may steady out after
midnight. But still, lows in the single digits over southwest MN and
far northwest IA are a good bet. With warm air advection continuing
on Sunday, highs should warm into the 30s to lower 40s.

To underscore the model variability we had yesterday, in which many
of the deterministic models were showing a cold front passage Monday
night. That is gone now. The cold front now comes through a whole 24
hours faster on Sunday night. The cold front looks dry, but there
should be some stratus coming southward behind it. In addition given
some of the latest 925mb temperatures, our highs may be too warm on
Monday. Lowered them a little bit from superblend values, but would
not be surprised if we are about 5 degrees too warm given the
current low level thermal values.

Otherwise the next upper troughing makes it into our area toward the
end of the extended forecast. There is a great deal of model
discrepancy that far out with the ECMWF stronger with the wave as
opposed to the GFS. The ECMWF is primarily the reason why we have
chance pops for precipitation late Thursday night and Friday along
and east of I 29. Before then, the ECMWF brings a very large
Canadian high southeastward on Wednesday through the Great Lakes
region which would bring a chillier easterly flow of air into our
area for Wednesday. The GFS is not even close to that solution, so
for now just went with the blend for Wednesday`s highs.

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 520 PM CST Fri Nov 16 2018

MVFR ceilings will slide south through the area this evening as a
band of snow moves through. By Saturday morning mainly VFR
conditions are expected. North to northeast winds will gust abvoe
25 mph from about 3z to 18z at most locations.

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...Winter Weather Advisory until 4 AM CST Saturday for MNZ071-072-
080-081-090.

IA...None.
NE...None.
&&

SHORT TERM...MJ
LONG TERM...MJ
AVIATION...08

Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

814 PM CST Fri Nov 16 2018

.UPDATE...
814 PM CST

Not planning any noteworthy changes to going forecast for this
evening. Overall, not much to add to the short term discussion
issued earlier this afternoon below.

Couple items of note to watch for:

1) The RAP continues to be quite aggressive with a deep
frontogenetic circulation persisting into tomorrow afternoon. In
addition to the more robust/persistent f-gen band in the RAP,
cross sections cut through the f-gen band show some fairly deep
pretty strongly negative layers of saturated EPV (indicative of
less stable conditions) coincident with the stronger omega. This
certainly suggests at least some potential for exists for some
bands of moderate to heavy snow embedded within the larger snow
shield. That could result in some localized 3 to maybe near 4
inch totals, but thinking is those amounts will be very much the
exception not the rule. Given the low confidence and limited areal
coverage of heavier amounts, don`t see a need to adjust going
forecast snowfall amounts as the forecast message would largely be
unchanged.

2) Snow, potentially at a decent clip, should continue through
midday in the Chicago area, however with temps likely to be near
or a hair above freezing and battling the time of day, suspect
that it will get increasingly difficult for accums to occur on
roadways.

3) Finally, as short discussion alluded to, models are notorious
for struggling with accurate depiction of f-gen band intensity and
duration. While many models suggest a quick weakening of f-gen
circulation and resultant snowfall as it gets into northern IL, it
wouldn`t be at all surprising to see occasionally moderate
snowfall continuing through the morning and perhaps even into the
afternoon.

Only planned changes to the grids/forecast this evening are:
* tweaking hourly temps a bit to reflect a trend driven more by
precip than diurnal influences.
* adjust pops to 100% over northern CWA
* adjust sky cover to remain overcast through the day Saturday

Updated grids and test products will be out shortly...

- Izzi

.SHORT TERM...
310 PM CST

Through Sunday...

Main concern is our next round of light snow accumulations tonight
into Saturday, with some minor additional snowfall possible
Saturday night for portions of east central Illinois and northwest
Indiana. Will not be issuing any winter headlines for tonight-
Saturday`s minor event given expected amounts below typical
criteria, mostly light snow rates, and Saturday morning timing.

Regional radar early this afternoon mosaic indicates the
advertised fairly narrow swath of snow from portions of the
Dakotas to southwest Minnesota. This is being driven by an
elongated but potent mid-level short-wave diving southeast across
the aforementioned areas. In addition, a tight thermal
gradient/baroclinic zone was noted over the central and northern
Plains, with this contributing mesoscale frontogenetic enhancement
to the snow. The overall trend in observations and in the guidance
has been a slight southward shift in the snow swath, with
ingredients looking to maximize from northeast IA into southwest
WI. Initial narrow band or bands of warm advection light snow
driven by a modest west-southwest ~20 kt 850 mb low level jet may
try to push into portions of northern Illinois mainly north of
I-88 as early as the late evening hours. With this initial push
encountering antecedent dry air aloft, it may end up being mostly
virga, so kept PoPs low through around midnight. The initial WAA
wing will also start the top down saturation process, helping to
get steadier precip going overnight.

A roughly west-east and still fairly narrow axis of snow will set
up mostly north of I-88 after midnight as mid-level short-wave
draws closer and low-level convergence and f-gen increases.
Forecast soundings indicate a relatively small dendritic growth
(snow growth) zone, though with decent lift co-located within the
DGZ for a time. Therefore anticipate steady light to temporary
moderate snow rates. While forcing ingredients will be fairly
impressive for a time just to our northwest, there is good
agreement in the model guidance that the mid-level short-wave
driving large scale forcing to dampen/weaken into Saturday
morning. Thus, for this reason the snowfall intensity overall may
trend downward Saturday morning over northern IL into far
northwest Indiana.

The main question is how long into Saturday morning does the
support for transient stronger banding as the area of snow shifts
more steadily southward with a southward moving cold front. Have
gone with the idea of some maintenance of banding signatures
despite evidence in some of the short range guidance of a quicker
erosion of the precip shield. While there doesn`t look to be
instability above the lower-level frontogenesis, have to consider
the possibility of f-gen banding remaining stronger longer than on
a majority of the guidance (as shown on 12z WRF-ARW and NMM).
The narrow DGZ, only short period of lift maximizing within DGZ,
and temps close to freezing during the event will keep ratios
mostly below 10:1, perhaps highest far north and northwest.
Amounts are favored to be up to/around an inch roughly between
I-80 and I-88, 1-2" north of I-88 and best chance for 2 to locally
3" amounts closer to the Wisconsin border. There may be some minor
travel impacts Saturday morning given mostly light snowfall rates.

As the precip area likely further diminishes in intensity Saturday
afternoon with southward progression, it will also encounter
temps likely having warmed to above freezing, so any accums south
will be likely a dusting to a few tenths at most on colder/grassy
surfaces. A marginal set-up for lake effect precipitation will
then evolve with northerly flow over the lake, CAA, and with time
lower-level convergence late day into Saturday night. Given low
inversion heights below 6kft, suspect lake effect precip will be
spotty, so kept PoPs in only slight to low chance range for this
for now, but will need to monitor trends. Finally, elevated
frontal zone will remain stalled near or south of southern CWA
Saturday night into Sunday morning with subtle low amplitude
wave(s) interacting with it. This could bring some additional
light snow accums to areas south of the Kankakee River, with low
magnitude of forcing likely keeping any accums under 1". Sunday
will feature decreasing clouds and light winds but continued
unseasonably chilly highs in the lower to mid 30s after starting
in the 20s.

Castro

.LONG TERM...
310 PM CST

Sunday night through Friday...

Sunday night through Tuesday night: Broad troughing over Hudson Bay
will begin to slowly shift east during this time, with deep cyclonic
flow remaining over the western Great Lakes. However, conditions
should remain dry across the area. The one exception will be the
potential for a brief shot of LES for mainly northern Porter County
sometime Monday night into Tuesday behind a mid-level trough. H8
temps are only marginally supportive of LES, so would not expect
any significant impacts.

Wednesday through Friday: Guidance begins to differ in the eastward
progression of the broad trough over eastern Canada by this time.
However, the general evolution will be toward mid-level ridging and
southerly surface winds over the central CONUS by Friday, promoting
temps closer to normal for late November.

Kluber

.AVIATION...
For the 00Z TAFs...

530 PM...Primary forecast concern is snow timing/chances and
associated vis/cigs.

A quick moving and likely narrow band of light snow is expected to
move across far northern IL later this evening but there remains
some uncertainty regarding how far south this band may move. For
now...included tempo mention at rfd/dpa/ord but the overall
duration could be an hour or less. Very light snow or flurries may
continue behind this band until the main area of light snow
spreads across northern IL early Saturday morning. Visibilities
with this snow are expected to lower to 1-2sm across most of the
terminals. Occasionally lower vis is possible...mainly across
northwest IL/rfd. Ifr cigs will also be possible but for now have
maintained prevailing 1kft cigs for the Chicago terminals and
trends will need to be monitored. Timing for the quick moving band
tonight appears to be faster and adjusted timing accordingly.
Timing for the snow overnight looks generally on track...perhaps a
tad faster and then the trend up looks potentially an hour or two
faster late Saturday morning. Very light snow or flurries may
persist Saturday afternoon and slowly end from north to south.
Some lake effect snow showers are possible Saturday night but
confidence for coverage/location is low so no mention for the 30
hr ord/mdw tafs.

Mvfr cigs 1-2kft this evening may begin to scatter/lift later this
evening but confidence is low and low mvfr cigs would fill back in
once snow begins later tonight. Mvfr cigs are likely to continue
Saturday after the snow tapers off with cigs possibly lifting into
low vfr by late afternoon/early evening.

West/northwest winds will diminish this evening and are expected
to become light and variable by late evening...then shift light
northerly by Saturday morning. Confidence on wind directions is
low and they may remain more north/northwest during the snow and
then turn more north/northeast Saturday afternoon with speeds
increasing toward 10kts. cms

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...IN nearshore waters until 9 PM Friday.

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Area Forecast Discussion

National Weather Service Paducah KY

929 PM CST Fri Nov 16 2018

.UPDATE...
Issued at 929 PM CST Fri Nov 16 2018

Updated the forecast to drop low temperatures tonight by a couple
degrees considering we`re already down to the lower and middle 30s
in much of the area. Also decreased late night sky cover and added
a mention of patchy fog to the northeastern half of the area, which
includes southwest Indiana, the Kentucky Pennyrile, and much of
southern Illinois. Already seeing patchy fog at Carmi, Mt. Carmel,
and Marion, Illinois, and Greenville, Kentucky as of mid evening.
Earlier guidance from the NAM, WRF, and HRRR was hammering dense
fog area wide overnight, while the latest WRF guidance keeps it
confined to northern/eastern portions of the forecast area. The
GFS and RAP hardly have any signs of fog overnight. The truth
probably lies somewhere in between, and it makes sense to mention
at least patchy fog in our northeastern half where more low level
moisture remains from recent snow/ice melt. Patchy freezing fog
is also possible where temperatures drop below freezing for several
hours.

.SHORT TERM...(Tonight through Sunday night)
Issued at 317 PM CST Fri Nov 16 2018

As an area of high surface pressure moves through the PAH forecast
area late today and tonight, light westerly winds will go calm or
nearly calm overnight, then pick up a bit out of the south on Sat
as the warm-up continues on the back side of the high. Temps are
forecast to rise easily into the 50s everywhere on Sat. Though
there will be some clouds in the northern third of the region Sat,
cloudiness will be on the increase Sat night ahead of the next
pcpn-generating system.

This system will come in the form of two un-phased shortwaves in
the cyclonic northern stream moving through our region, the
second shortwave accompanied by a surface pressure trof/weak cold
front. This set-up should result in a surface wind shift to the
north as early as Sat night, ahead of the pcpn. Early Sun, light
rain may begin west of the MS River (limited PoPs) and expand
across the remainder of the region by nightfall. Sun night, the
wedge of colder air will be sinking further south into our region,
providing additional lift of moisture (better PoPs). Late Sun
night, there may be enough cold air in place across parts of
southern IL and the higher elevations of southeastern MO to create
a brief period of a wintry mix as the pcpn ends. Warmer surface
temps should preclude impacts.

.LONG TERM...(Monday through Friday)
Issued at 317 PM CST Fri Nov 16 2018

Quiet weather in the long term, until possibly Friday. The models
made one adjustment and indicate a small chance of rain Monday
morning across mainly the KY Pennyrile region. Given 3 solutions
point toward this, we went with the addition. Back to the bigger
picture, WPC points out that the ECENS slightly slower solutions
with recent systems has verified better, and we followed their line
of thinking. We will transition out of NW flow aloft as mid level
ridging develops across the area ahead of a west U.S. trof, forecast
to move toward and into the central U.S. Thursday through Friday.
Dry weather is anticipated through Thursday, as high pressure will
be in control for the most part. We will carry a chance of rain
Friday as a result of the forecast position of the aformentioned
upper trof just to our west. Temperatures overall will remain below
normal. However, moderation is anticipated through the end of the
week.

.AVIATION...
Issued at 541 PM CST Fri Nov 16 2018

High pressure will provide mostly clear skies and light winds for
tonight. Some of the hi-res guidance is hinting at some fog
potential overnight, but given low confidence in this occurring,
left out of TAFs for now and will monitor this evening. Some mid
and high clouds will be on the increase tomorrow ahead of a system
moving in from our northwest. Winds will take on a southerly
component tomorrow before switching around to the north very late
in the period or just beyond. MVFR cigs may move into northwestern
portions of the region late in the period, and then spread
southward through the area just beyond this forecast period.

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

UPDATE...RJP
SHORT TERM...DB
LONG TERM...CN
AVIATION...SP