Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/02/19
Area Forecast Discussion
National Weather Service Binghamton NY
949 PM EST Sun Dec 1 2019
A major winter storm system will impact the area through Monday
bringing significant snow accumulation along with some ice this
evening. Then remaining cold with scattered snow showers and
lake effect snow mid to late week.
.NEAR TERM /THROUGH MONDAY NIGHT/...
**Major winter storm will continue to impact the area tonight
through Monday. Entire forecast area is now under winter storm
Late evening update:
Low pressure late this evening is transferring to the east
coast and the RAP continues to show cold air advection in the
mid- levels which will result in the wintry mix changing back to
snow throughout the late evening into the overnight. The snow
will likely become banded and heavy at times toward midnight
centered in the Finger lakes into the overnight then building
into the Southern Tier and northeast PA toward sunrise Monday.
The latest runs of the 18z ECMWF,HRRR and Hi-res NAM focus the
banding from near Ithaca to Binghamton then into Wayne and Pike
counties across NE PA. We await the RGEM for inclusion into the
next update to better define the location of the banding.
Outside of the banding less QPF may end up being the rule.
The primary low over the OH Valley continues to fill while the
secondary low organizes near the NJ coast. Favorable forcing for
ascent will overspread the area late this evening and
especially overnight as the upper low approaches from the OH
Valley and a strengthening SEly low-level jet draws moisture
from the Atlantic. Dynamical cooling will erode residual warm
layer aloft, leading to a transition to steady snow from northwest
to southeast. Some mix with sleet could linger all night across
Sullivan NY and Pike counties.
Although there is still considerably uncertainty, this initial
mesoscale snow band is favored to develop over CNY overnight and
expand S/E toward early morning. Travel conditions will quickly
deteriorate under this heavy snowfall band with rates of 1-2"
per hour expected.
Monday...Fairly good model agreement now that the mid level low
will be reconsolidating and strengthening just to the south of
our CWA, tracking near Philadelphia by midday. This is a very
favorable track to wrap Atlantic moisture into the area from
the north-northeast. There is some worry that a mid level dry
slot could get close to our far east/southeast counties for a
short time on Monday; this would cut down on snow rates here.
Not completely sold on this yet though. Otherwise a north-
south oriented band of steady to heavy snow is forecast to sit
nearly stationary, in a strong deformation zone right through
the center of our forecast area. This band is likely to persist
much of the day Monday; perhaps eroding to snow showers toward
sunset across the far west. It is still very difficult to
pinpoint exactly where the heaviest mesoscale snow bands will
set up...and under these bands snowfall rates of 1-2"+ per hour
are expected. Current indications have shifted a bit west, and
now the corridor for heaviest snow (and best frontogenetical
banding) is forecast to be along a corridor from near Syracuse,
to Cortland, Ithaca, Elmira, Owego, Binghamton, Towanda, and
Tunkhannock. One rather big adjustment with this forecast
update was to raise snow amounts in both Steuben and Luzerne
county, with plenty of wrap around deformation snow now expected
to impact both these counties through the day. Snow amounts
have been lowered some across the Catskills, due to the shift NW
in the mid level circulation and perhaps a little downsloping
off the higher peak in the low level ENE flow. Northerly
surface winds of 10-20 mph could create patchy blowing snow.
Snow to liquid ratios are expected to range from 10-14:1...with
the lower ratios in the valleys where surface temperatures are
a bit marginal 29-33 degrees.
Monday night...Periods of snow linger well into Monday evening
as the low finally begins to move away from the NJ coast by
midnight. The snow should end from NW to SE, but should quickly
fall apart as we lose forcing by midnight or so. An additional
1-3 inches of snow is forecast after 7pm east of I-81.
Northwest winds remain breezy 10-20 mph with flurries after
midnight. Lows dip into the upper 10s and lower 20s.
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
430 PM UPDATE...
Weak ridging will briefly allow for a return to dry conditions
for Tuesday, with skies clearing from west to east in the wake
of the exiting system. Temperatures peak in the low/mid 30s
Tuesday falling back generally into the 20s overnight. Clouds
start to work back in Tuesday evening with another surface low
working into Quebec. This will drag a cold front through the
area Wednesday, touching off snow showers during the daytime
hours. Snow may transition over to a rain/snow mix, especially
in the valleys, as temperatures peak in the mid/upper 30s ahead
of the front. Little by way of snow accumulations are expected.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
No real changes with the long term, so the previous discussion
will continue below.
400 AM UPDATE...
Northwest flow behind the shortwave will bring colder air and
and lake effect snow showers through Thursday. This activity
will end quickly however as surface ridging arrives early
Friday. This will be short lived as well as a stronger short
wave and cold front arrives late Friday with even colder air.
This will trigger yet another lake effect snow shower event that
will linger into Saturday.
Temperatures through the period will average near normal,
although will trend lower as the coldest air arrives at the end
of the period.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
A powerful winter storm will continue to spin snow and sleet
across the region. Snow will intensify overnight and cause
conditions to degrade at area terminals.
Mainly MVFR ceilings and visibilities are expected this evening
as a mix of light snow, sleet, and freezing rain falls across NY
As snow intensifies early Monday morning, IFR and LIFR
conditions will develop and persist through the afternoon hours
at all of our terminals.
Snow will begin to taper off late Monday afternoon or early
Monday night...Restrictions possible in light snow.
Wednesday...Another system moving in brings chances for rain
and snow showers with restrictions possible.
Thursday and Friday...Restrictions possible in lake effect snow
PA...Winter Storm Warning until midnight EST Monday night for
NY...Winter Storm Warning until midnight EST Monday night for
Winter Storm Warning until 7 PM EST Monday for NYZ022.
Area Forecast Discussion
National Weather Service Des Moines IA
549 PM CST Sun Dec 1 2019
.DISCUSSION.../Tonight through Sunday/
Issued at 158 PM CST Sun Dec 1 2019
.Overview...Outside of lingering very light precipitation that will
end early this evening and gusty winds decreasing through tonight,
the weather will be largely dry with temperatures becoming near or a
bit above normal for a majority of the upcoming week.
.Details...Low pressure that was near Waterloo well before dawn this
morning has advanced eastward and can be seen easily in the GOES-
East Day Snow Fog RGB with the broad counter-clockwise circulation
over the southern part of the Great Lakes. The clouds are expansive
ranging from eastern Nebraska to the East Coast with more convective
clouds along the cold front down the East Coast with a well defined
rope cloud stretched east-northeast to west-southwest over the
northern Gulf of Mexico. GOES-East is also providing a wealth of
information about the clouds over us. The Day Cloud Phase
Distinction (DCPD) shows generally liquid water clouds with the
snow/ice 1.61 micrometer channel and the Cloud Top Phase confirming
a lack of ice. The lack of ice introduction and temperatures near or
below freezing will continue to result in intermittent freezing
drizzle through the remainder of the daylight hours. There are some
high clouds that are rotating into northern Iowa as noted by the
pinkish/orangish hues in the DCPD RGB and if this introduces ice
into the column, this should lend itself to more snow versus
freezing drizzle. Regardless of precipitation type, all of it will
very light to light in intensity and not amount to much additional
snowfall or ice accretion. Yesterday, there was some thought that
horizontal convective roll induced snow showers may develop. While
recent HRRR and RAP soundings maintain some elevated instability, it
is weaker than yesterday and with the cloud cover this is seeming
less likely. Otherwise, with the pressure gradient relaxing and the
highest pressure rises also moving away from the area, will see a
downward trend in wind speeds and gusts through the remainder of the
day into tonight.
The remainder of the forecast has temperatures below normal on
Monday and then mainly near if not above normal temperatures Tuesday
into next weekend. There are no significant precipitation chances
until perhaps sometime late next weekend. The flow aloft will be
from the west-northwest much of the week with two shortwave troughs
passing over the region in this flow. The first is Monday night into
Tuesday with the best QG convergence passing northeast of the state.
While the NAM cross section does show perhaps a bit more moisture in
the column over northern Iowa with spotty light QPF, will stay with
initial guidance and keep dry. This is because the GFS cross
sections are drier in the low levels compared to the NAM with the
other high resolution and global deterministic models maintaining no
QPF. The next shortwave trough will move quickly from off the
California coast on Wednesday and pass south of the state on
Thursday. Trend continues for this shortwave and its precipitation
to remain largely south of the state, but still maintain some token
PoPs over far southern Iowa. By next weekend, a positively tilted,
longwave trough will be changing the pattern up as it develops over
the Western US. As it moves eastward, this could bring precipitation
back to the state late this next weekend into early the following
.AVIATION.../For the 00Z TAFS through 00Z Monday evening/
Issued at 549 PM CST Sun Dec 1 2019
Secondary trough moving through area now with weak lift and a few
areas of -DZ,-FZDZ and --SN accompanying the boundary. Winds
briefly gusting again to near 30kts as well. One last push of MVFR
cigs along and just behind the boundary will give way to gradual
VFR from 04z northwest at KFOD to 09z southeast at KOTM. A brief
period of light precip with no impacts will accompany the boundary
as well. Aft 12z most areas VFR with mainly light winds and wind
shift to WSW by 18-21z as high pressure ridge settles over the
area and ridge passes east. /rev
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
932 PM CST Sun Dec 1 2019
932 PM CST
Have lowered pops for the remainder of the night across north
central IL, with snow showers ending a little quicker from the
north and northwest late this evening. Lake effect potential still
exists, though looks less than impressive and have lowered
additional snow amounts slightly.
Surface trough/secondary cold front has pushed through the cwa
since late this afternoon, with cooling surface temps allowing a
change from rain to wet snow across all but the far southeast
counties as of 9 pm. Radar mosaic currently shows most organized
area of precipitation along the I-55 corridor from Chicago
southwestward, in association with an embedded mid-level short
wave wrapping cyclonically around the west side of the departing
upper low. Guidance indicates strong mid-level height rises
developing across the region overnight in the wake of this
feature, with significant erosion of precipitation across WI and
far north/northwest IL noted in regional radar mosaic. Based on
this, have lowered/ended pops for light snow across the area a
little faster late this evening/overnight. Loss of mid-level
moisture, and temps generally warmer than -10C at the top of
shallow low cloud layer may support some patchy freezing drizzle
across the eastern cwa overnight, though impact is expected to be
minimal with temps near 30 and pavement temps likely slightly
above that. Based on above have lowered snow amounts just a bit
(lower snow:liquid ratios, less qpf where snow already ending for
the most part). Mainly just a few tenths of slushy accumulation on
Lake effect potential for parts of northeast IL and northwest IN
remains, though thermodynamic conditions are not very favorable.
North-south band of weak convective cells noted in convergent axis
just off the Wisconsin shoreline to our north will continue to
advect south into the area overnight/early Monday, but shallow
inversion heights and poor quality of ice nucleation (temps
generally warmer than -12C at the equilibrium level) suggest small
flakes and perhaps more of a rain/snow mix at times especially
downwind of the lake in Indiana. Light rain/snow shower mix
continues into Monday for northwest IN, again with similar minimal
Updated forecast products available.
225 PM CST
Through Monday night...
Low pressure, both at the surface and aloft, is now centered over
northern IN and southern MI early this afternoon. As this low
continues to shift to the east through the sunset, a surface
boundary across far northern IL which gradually shift southward
across the area allowing the surface flow to shift out of the
north. Numerous showers, with some instances of light snow and/or
sleet have developed over the area in association with a band of
frontogenesis along this frontal boundary. Thus far, however,
temperatures and dew points have remained warm enough to keep a
majority of this precipitation in the form of rain. This will
change, however, in the next couple hours as the surface boundary
shifts the winds out of the north. As this occurs, some lower dew
point air should shift south over the area, and should thus result
in lowering wet-bulb zero heights and a transition to more snow
than rain showers by late afternoon and this evening. Little to no
snow accumulation is expected through late this afternoon due to
the warm temperatures.
The stacked system will continue shifting away after dark,
however forcing for precipitation will continue through the
evening both on the synoptic and meso scales. The gradually
occluding system has a jet maximum wrapping around on its north as
seen on water vapor imagery within the pseudo-deformation area.
Guidance strengthens this with a left exit region over northeast
Illinois during the early-mid evening. This will help focus
stronger forcing for ascent and possibly some mid-level
frontogenesis under this. Basically this forcing is responsible
for the area of snow / snow showers across central Wisconsin to
central Lake Michigan early this afternoon that is slowly moving
south. We envision this area rotating south-southeastward through
mid-evening within the aforementioned forcing.
At the same time and persisting several hours after, a more
mesoscale feature of low-level convergence on the western
periphery of Lake Michigan is forecast to support lake enhanced
snow showers in a north-to-south corridor tonight. This will be
within the upper level forcing noted above, especially this
evening, and because of this there likely will be transient
heavier snow showers. The forecast thermodynamic profiles,
modified slightly for lower 40s near-surface lake temperatures,
have marginal equilibrium levels (5000 ft) and snow ratios
(likely only near 10:1). However, profiles do support up to
100-150 J/kg of modified surface-based CAPE, and convection-
allowing models portray solutions of a higher corridor of
mesoscale QPF. Have focused the forecast precipitation in that
late evening into overnight period more so with that convergence
and boosted QPF some. While the snow ratios will not be overly
high, the duration of snow showers and cooling surface wet-bulb
values, will likely result in an area of accumulation mainly under
an inch. There conceivably could be a narrow area of one to two
inches in some part of Lake, Cook, DuPage, and far eastern McHenry
County where the area of focus is most persistent, but confidence
on that is low.
As the synoptic forcing gradually wanes later this evening,
precipitation apart from the lake enhancement noted above, will be
largely if not entirely ending from west to east. Forecast
profiles do hint that there could be a little bit of drizzle and
with cooling temperatures to below freezing by midnight across
much of northern Illinois, this is of note. However the chance
for drizzle is with very low confidence. It`s not a great setup,
and profiles actually may still be deep enough for flurries/light
snow. Have added a slight chance of freezing drizzle into the
forecast, primarily 11 pm and after, and mainly for northeast
As the above discussion notes, northeast Illinois is the primary
area for forcing and focus tonight, and with enough of these
elements going on and during a major travel evening, have issued
an SPS and will focus messaging on this. Again this does not look
like major impacts, but at times visibility will likely be
sharply reduced, and as roads cool after dark, there may be some
patchy slick spots to develop due to the frozen precipitation. If
precipitation were to persist right up until daybreak in Chicago,
this may have more of an impact with possible residual slickness
into the start of the commute.
Going into Monday morning, true lake effect snow will be
continuing into northwest Indiana. This will continue to struggle
with snow ratios due to the coolest part of the saturation
forecast only to be around -9C. This will encompass the morning
commute in northwest Indiana and with some pockets of sharply
reduced visibility possible, it will be something we will have to
watch. Additional accumulation should again be minor. Clouds will
be slow to clear on Monday just simply looking at current
satellite, but enough dry advection is forecast that at least
north central Illinois should clear during the day and likely a
good amount of the CWA into the evening. High clouds will be
returning quickly though ahead of a northern stream disturbance.
Regarding lakeshore flooding...as the surface low shifts towards
the eastern Great Lakes early this evening the winds over Lake
Michigan will become northerly and increase. Not much has changed
with the wave forecast, with generally 8 to 12 foot waves expected
tonight into Monday over southern Lake Michigan. The highest
flooding/erosion impacts will be over northwestern IN and into
portions of Cook county due to a northerly wind component. These
areas remain under a Lakeshore Flood Warning tonight into Monday.
Also, Lake County IL remains in an Advisory, as the impacts should
be reduced some due to the unfavorable wind component there.
Conditions will improve late Monday and Monday evening as the
winds abate, and begin to shift more westerly Monday night.
225 PM CST
Tuesday through Sunday...
A potentially, and seemingly rare, quiet extended period may be
ahead. As noted above a northern stream wave or two is forecast
to pass during midweek. Even with a southward shift, any
precipitation with this Tuesday night would be brief and light
given the system trajectory, but again right now that is all
north. Cyclonic flow aloft looks to be dampened into Thursday and
Friday, with a southern stream closed low forecast to move into
the Ohio Valley during the end of the week. This is forecast by
the ECMWF and almost all GEFS members to be south of the area,
which would keep the CWA quiet into at least the start of next
weekend. If that were to be the case, there is a signal of some
moderation next weekend with southwest flow in the lower to mid-
levels. The National Blend of Models provides mid 40s for highs
during the first full weekend of December and could see warmer,
but obviously it takes only little this time of year to muck that
up with clouds. So all in all, there is presently no high impact
weather seen for the local area from Tuesday-Saturday.
For the 00Z TAFs...
531 PM...Forecast concerns include...
Snow showers and associated vis/cigs this evening.
Possible light freezing drizzle overnight.
Strong/gusty northwest winds through midday Monday.
A band of light snow is moving across northeast IL early this
evening and it extends into southeast WI. While heavier snow
showers and the current band may be short in duration...there
will likely be some light snow/flurries falling for most of the
evening. There may still be some light rain mixed in for a few
hours this evening. Much of the short term guidance develops a
band of snow near the lake late this evening into early Monday
morning and it may remain east of ord/mdw with low confidence.
There remains quite a bit of uncertainty for the potential for
light freezing drizzle overnight. Air temperatures will be
dropping below freezing after midnight. If there is any precip
still falling...it could be in the form of freezing drizzle or a
mix of freezing drizzle and light snow. The hrrr model shows this
fairly well overnight so have maintained mention with this
forecast. Snow showers may continue to persist into northwest
Indiana through Monday morning.
Prevailing cigs appear to be favoring low mvfr this evening but
there will still be some ifr...especially in the heavier snow
showers. Low mvfr cigs will then continue into Monday morning when
they will scatter from west to east.
North/northwest winds in the 12-16kt range will continue through
late Monday morning with gusts into the mid 20kt range. Winds will
slowly turn more west/northwest Monday afternoon with speeds and
gusts steadily diminishing with light winds Monday evening. cms
225 PM CST
West-southwesterly winds, currently ongoing over southern Lake
Michgian, will shift northerly by early this evening as a surface
low shifts towards the eastern Great Lakes. With this wind shift,
expect winds to increase out of the north up around 30 kt, with
some occasional gale force winds to 35 kt. Northerly winds will
continue on Monday, but speeds should gradually diminish through
the day. A gale warning remains in effect for southern Lake
Michigan from early this evening into Monday morning, when the
highest winds are expected. Waves will build to 8 to 12 ft with
this event tonight, then gradually subside late Monday and Monday
evening. A small craft advisory will likely be needed following
the gale as waves will likely remain above 4` through late Monday.
IL...Lakeshore Flood Warning...ILZ014 until noon Monday.
Lakeshore Flood Advisory...ILZ006 until 9 AM Monday.
IN...Lakeshore Flood Warning...INZ001-INZ002 until 6 PM Monday.
LM...Gale Warning...IL nearshore waters until 9 AM Monday.
Gale Warning...IN nearshore waters until noon Monday.
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Area Forecast Discussion
National Weather Service Melbourne FL
940 PM EST Sun Dec 1 2019
...Strong Cold Front will Sweep Through Overnight...
Southwest flow ahead of a strong cold front is keeping temps mild
this evening, in the low to mid 70s. The front is forecast to push
across most of EC FL overnight with some post frontal cooling
reaching Lake and Volusia counties by morning with lows in the mid
50s. The front will push south of Martin county a little after
sunrise so min temps will remain mild in the mid and upper 60s along
the Treasure coast.
Mesoscale guidance such as HRRR and HREF members show a thin band of
showers redeveloping along the front as it reaches North
Lake/Volusia counties in the next couple hours. This band of showers
should progress steadily to the SE overnight and clear Martin county
just after sunrise. Rainfall amounts will be less than a tenth of an
inch and no thunder is expected.
On Monday, cold advection will be partly offset by full sunshine.
Temps will be noticeably cooler than today with highs ranging from
the mid 60s Orlando northward to the mid 70s Okeechobee to the
Ocnl MVFR CIGs expected thru the overnight ahead of and along a cold
front which will push south of SUA just after 12Z. Southwest winds
10 knots becoming West overnight with some higher gusts immediately
behind the front. On Monday, W/NW winds 15 knots and gusty with CLR
Small Craft Advisory conditions are occurring across the Volusia and
Brevard coastal waters as southwest pressure gradient tightens
producing 20-25 knots with occasional gusts to Gale force (34 knots)
over the open Atlc. These higher winds will spread southward
offshore the Treasure coast overnight and become westerly. Seas are
suppressed nearshore due to the offshore flow so higher seas (7-8
ft) will remain confined to the offshore waters, beyond 20 nm, thru
.PRELIMINARY POINT TEMPS/POPS...
DAB 53 62 39 59 / 40 0 0 0
MCO 59 66 42 60 / 40 0 0 0
MLB 60 70 41 63 / 30 0 0 0
VRB 62 73 42 64 / 30 10 0 0
LEE 55 62 40 60 / 40 0 0 0
SFB 58 65 39 60 / 40 0 0 0
ORL 58 66 42 60 / 40 0 0 0
FPR 63 74 41 65 / 30 10 0 0
AM...Small Craft Advisory until 10 AM EST Monday for Flagler Beach to
Volusia-Brevard County Line 0-20 nm-Volusia-Brevard County
Line to Sebastian Inlet 0-20 nm.
Small Craft Advisory until 10 PM EST Monday for Sebastian Inlet
to Jupiter Inlet 20-60 nm.
Small Craft Advisory until 10 PM EST Monday for Flagler Beach to
Volusia-Brevard County Line 20-60 nm-Volusia-Brevard County
Line to Sebastian Inlet 20-60 nm.
Area Forecast Discussion
National Weather Service Marquette MI
626 PM EST Sun Dec 1 2019
.SHORT TERM...(This evening through Monday)
Issued at 248 PM EST SUN DEC 1 2019
GOES imagery and RAP show the well-defined Colorado Low across the
Ohio River Valley this afternoon, as models indicated this low will
continue eastward towards the mid-Atlantic tonight. Snow is beginning
to taper off across the north and west this afternoon, and is
expected to continue this afternoon. Models continue to indicated a
large area of q-vector conv this afternoon as rapid refresh models
show continued isentropic ascent across Upper Michigan, especially
east. A band of heavy snow oriented across much of Marquette County
picked up additional moisture flux across Lake Huron before wrapping
around the low in Upper Michigan. Due to this, did extend some of
the Winter Storm Warnings and Advisories across central and eastern
UP into this afternoon. Radar estimates prolonged snowfall rates of
1 in/hour and current radar trends suggests that this will continue
for at least another hour or two. Another intense band of snow
remains to the south across Delta and Schoolcraft counties as well.
Latest RAP run suggests this isentropic lift to gradually decrease
over the next few hours, as PoPs will mirror that trend. Left SLRs
around 10:1 given latest MQT observation at 9:1 at 18Z. Per webcams
across western Upper Michigan, snowfall and impacts have become
generally benign with snowfall coming to an end. Upstream obs and
GOES imagery support this showing continued drier air filtering in
across the west. Models suggest this drier air to continue filling
in from the north and west this afternoon into the evening. By 00Z
only PoPs remaining across Upper Michigan will remain along US-2 and
the Seney stretch as low pressure and associated lift continue to
pull away to the east. As far as snow totals go, expecting another 2-
4 inches across central and eastern Upper Michigan.
Tonight into Monday, as drier air and a ridge of high pressure move
across Upper Michigan, skies are expecting to become partly cloudy.
Some high-res models indicate clouds to stick around through the
overnight hours into tomorrow morning across western and central UP
as northerly winds create some clouds downwind of Lake Superior. By
tomorrow afternoon, the ridge of high pressure passes over the UP,
bringing lighter southerly winds...cutting off any flow from Lake
Superior and bringing clearing skies. ARW/NMM WRFs suggest the
development of some lake-effect -shsn, or perhaps fzdz, but upstream
obs and model trends suggest the increase of drier air in the low-
levels will alleviate the risk of any accumulation. With a fresh
snowpack, temps should be able to fall into the teens tonight,
despite any lingering low-level moisture and climb to near 30 on
.LONG TERM...(Monday night through Sunday)
Issued at 503 PM EST SUN DEC 1 2019
Models suggest that a low amplitude pattern will prevail with
several northern stream shortwave troughs bringing brief colder
periods along with some light northwest flow LES.
Monday night, behind the mid level and sfc ridge, WAA will quickly
take over. Some -shsn will be possible over the northwest ahead of a
weak trough moving the region. Otherwise, temps may drop quickly
during the evening into the teens inland and then climb late as
clouds move in along with increasing southwest winds.
Tuesday, mainly dry conditions are expected as westerly low level
flow moves behind the sfc trough. 850 mb temps dropping to near -8C
late may support some light LES into the Keweenaw.
Tue night and Wed, a shrtwv and associated cold front dropping
through the northern Great Lakes will bring increasing LES chances
for northwest flow favored locations. 850 mb temps to around -12C
(water temps 4C to 5C) will provide enough instability for LES
especially combined with the shrtwv and deeper moisture. However,
overall accumulations should only amount to a few inches given the
relatively weak lake induced CAPE to 200 J/Kg.
Thu-Sun, a more vigorous shrtwv with moderate to strong 700-300
qvector conv will brush the area. Although most of the the snow with
this system will remain to the north near the stronger forcing. CAA
in the wake of the shrtwv and sfc low is likely to drop 850 mb temps
to near -17C by Friday favoring another batch of LES for nw flow
locations. Dry WAA Saturday will bring milder conditions with temps
in the low 30s with the potential for another shrtwv and light pcpn
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 625 PM EST SUN DEC 1 2019
Snow continues to slide to the south of the Upper Peninsula this
evening...leaving behind VFR conditions at KSAW and KCMX. MVFR
ceilings will persist at KIWD into the early morning hours due to
continuing moisture advection off the lake...but this too will end
as drier air pushes in with the approaching high pressure
system. Winds will remain light through the forecast period.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 248 PM EST SUN DEC 1 2019
Northeast winds gusting up to 35 knots this morning and afternoon
will continue to relax this afternoon and evening as a ridge of high
pressure moves across Lake Superior. Northerly winds will be under
20 knots by sunrise on Monday, before becoming southwesterly and
increasing up to 25 knots on Monday night. As a trough moves across
the lake on Tuesday afternoon, winds will become northwesterly and
remain between 20 and 30 knots through Wednesday evening. Expect a
brief break below 20 knots on Thursday before another trough passes
over the lake on Thursday night, bringing the return of 30-knots
gusts from the NW to N. High pressure will move across the area for
the weekend, but the pressure gradient will remain with
southwesterly winds between 20 and 30 knots.
Winter Storm Warning until 7 PM EST /6 PM CST/ this evening for
Gale Warning until 10 PM EST this evening for LMZ221-248-250.