Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/05/21

Area Forecast Discussion

National Weather Service Bismarck ND

 953 PM CST Mon Jan 4 2021

.UPDATE...
Issued at 949 PM CST Mon Jan 4 2021

Challenge in the short term continues to be the precipitation
expected with the initial front in the west Tuesday morning. With
00Z data coming in, 00Z RAP looks worst case scenario in regards
to potentially freezing rain with the forecast sounding at
Williston becoming fully saturated and featuring a +3 C warm nose
centered around 900mb atop a subfreezing surface layer. However
00Z HRRR/NAM profiles are much slower to saturate and thus bring
precipitation into the northwest around 18Z, when surface
temperatures are more likely to be at or above freezing with
combined effects of daytime heading and warm air advection ahead
of the front. Given magnitude of dry air in the 00Z BIS raob, the
HRRR/NAM solutions seem more reasonable. There may be a small
window where the far northwest sees some freezing liquid if
precipitation can begin early enough but likelihood of this looks
low, with precipitation types likely to stay rain or snow. Thus
no changes in messaging needed with this update.

UPDATE Issued at 603 PM CST Mon Jan 4 2021

Northwest flow aloft continues with surface ridge centering over
Northern Plains. Satellite picture shows clear skies for all but the
far southwest where cirrus is beginning to arrive. Mid/upper
level clouds will continue to push in overnight in as upstream
wave approaches. Based on 00Z BIS observed sounding, there is
plenty of dry air through the atmospheric column to work through
which matches with previous discussion`s mention of precipitation
timing in the west Tuesday morning. No changes needed to the
going forecast, will see how 00Z data evolves with tomorrow`s
precipitation both in the west/central and then later in the James
River Valley.

&&

.SHORT TERM...(This evening through Tuesday Night)

Issued at 230 PM CST Mon Jan 4 2021

Forecast highlights in the short term period will be chances for
rain and snow Tuesday, followed by snow Tuesday night with some
accumulations across the James River Valley.

Currently, strong northwest flow aloft with a mid level trough
over Minnesota and a long wave ridge across the Northern Rockies.
Surface high pressure over the Central Plains results in a steady
westerly wind today, providing enough mixing coupled with a clear
sky to see another day of mild temperatures in the 30s north and
east, and 40s southwest and central.

For tonight, upper level ridge develops east into the Northern
Plains as a strong S/WV trough moves into eastern Montana.
Increasing mid/upper level cloud cover along and ahead of the
ridge, with already increasing clouds across eastern Montana early
this afternoon. WAA will also spread east across the western and
central areas of the state tonight.

S/WV mid level trough moves into eastern MT Tuesday morning, with
an associated sfc trough developing into the far western Dakotas.
This will bring a chance for light precipitation to the west after
12Z Tuesday. May take some time for moisture to reach the surface as
cloud bases are projected at around 10K ft AGL at 12Z, with the
boundary layer not saturating till later in the morning. Precip
type should be either rain or snow as we cool aloft through the
morning hours. Some guidance suggested freezing rain or sleet west,
though with the initial dry boundary layer, this window will be
short lived if open at all, as we wetbulb out to subfreezing
temperatures aloft. Thus will go all rain or snow depending on
low level temperatures.

Flow aloft morphs into split flow Tuesday afternoon/night, with
associated sfc lows developing over central South Dakota and south
central Saskatchewan during the day Tuesday. South central North
Dakota and into the James River Valley will see the best low level
forcing Tues aft/night, north/northeast of the central SD sfc
low, and where models are strongly implying a mesoscale vort max
will track through. Best area of enhanced forcing will be over the
James River Valley, and with precip type all snow and QPF near
0.3", could see 2-4" of snow accumulation through Wed AM. Will
mention in the HWO.


.LONG TERM...(Tuesday night through Monday)

Issued at 230 PM CST Mon Jan 4 2021

Mainly dry and continued mild through the long term period.

Overall a messy upper level flow pattern Wednesday through next
weekend. Deterministic and a few ensemble runs are starting to
hint at a chance for precipitation during the Thursday/Friday
period, as another mid/upper level wave passes slowly through the
region. Upper level jet dynamics are weak though, so confidence
remains low that we will get wet. NBM also came in with mainly
sub-weather mentionable POPs, and the latest WPC cluster analysis
shows most GEFS/EC/Canadian ensemble runs dry. Will stick with
NBM.

The rest of period through next weekend looks dry with cooler
temperatures. However, still 5-15 degrees above normal for highs.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 603 PM CST Mon Jan 4 2021

Increasing clouds through the TAF period, VFR until 18-21Z in the
west. A front should bring MVFR ceilings with a chance of light
rain or snow after 18Z to KXWA-KDIK. This front will continue
towards KMOT-KBIS but isn`t expected to arrive until after 00Z.
Clouds and snow will push north into southeast North Dakota as
well, deteriorating ceilings and visibility at KJMS around but
more likely after 00Z.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...AE
SHORT TERM...NH
LONG TERM...NH
AVIATION...AE



Area Forecast Discussion

National Weather Service State College PA

 1036 PM EST Mon Jan 4 2021

.SYNOPSIS...
High pressure will keep fair weather over the region tonight. A
pair of closed lows and a cold pool aloft will combine to
produce flurries and snow showers Tuesday and Tuesday night
along with minimal accumulation. Improving conditions are
expected Wednesday with tranquil conditions expected to last
through this weekend.

&&

.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
Temps just inching down. Fcst temps and wx/PoPs are on track.
Dewpoints just a little higher, so tweaked them a little. One
band of very weak showers did make some meas precip at IPT (RA
and UP). NAM 12 has this pegged with just a hairline of meas
precip progged right about now across the nrn mtns. If there
were to be breaks develop, the high dewpoints might lead to some
fog of note. But, just HGR is below 1SM attm. Something to watch
out for, but the clouds are very stubborn, and not many breaks
are possible overnight.

Prev...
Clouds rule. BFD diurnal range so far today is just ONE degree
(F): 34 max, 33 min. I`ve been a weather geek for quite a
while, and I don`t know if I`ve ever seen a diurnal range of 1
(or zero for that matter). Other sites were also very close with
the maxes and mins (so far). Expect few breaks in the clouds,
but some could try to develop, mainly SE. Temp profiles from the
RAP are cold enough to keep mentions of precip to SHSN/flurries
overnight.

Prev...
Widespread low clouds thanks to residual low level moisture
and light upslope flow are producing patchy fog and some higher
terrain spits of drizzle this afternoon. This will last into
tonight and clouds will only slowly break under influence of
upper level cyclonic flow despite weak surface ridge axis. Mins
will be above seasonal norms ranging from the mid 20s north to
the lower 30s southeast.

&&

.SHORT TERM /7 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Upper trough axis is progged with swing through the Wednesday,
accompanied by snow showers and flurries, most numerous in the
afternoon. The highest POPs and best chance of a fresh dusting
will be across the northern mountains and Laurel Highlands.
Otherwise, low level instability associated with relatively cool
temps aloft will result in plenty of stratocu and little spread
between daytime highs and nighttime lows. North America
continues to be flooded by a good deal of Pacific air, which
will result in our temperatures averaging 5-10 degrees above
average.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Most of the coming week continues to look relatively benign,
weather-wise. Temperatures will will be near to just slightly
above-normal for early January, with little in the way of
precipitation outside of a few lingering snow showers into Wed
across northern and western PA.

Low pressure will pass to our south on Friday, but model
consensus continues to keep precip south of the Mason-Dixon
line. We will continue to monitor the evolution of this system
and another that could approach the area early next week.

&&

.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
At 00z, cigs have improved to MVFR across the central and
western airfields with VFR at LNS and MDT. Periods of -DZ and
-SN are expected overnight, which will lead to brief reductions
 in visibility. Winds will go calm overnight as cloud cover
 hangs tough.

Model guidance points to a slight lowering of ceilings
overnight to IFR/MVFR areawide. Ample moisture near the ground
may result in some mist/vis reductions toward daybreak, which
has been reflected in the appropriate TAFs. It is worth noting
that IFR vis may make it all the way southeast into MDT by
morning, but not enough confidence to go IFR quite yet. Stuck
with low-end MVFR vis at this point.

Visibility should improve by mid morning, but ceilings will be
slow to lift, with prevailing MVFR hanging tough through Tuesday
afternoon. MDT and LNS may trend VFR in the late afternoon, but
recovery will be slow.

Outlook...

Wed-Sat...Generally VFR.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...DeVoir/Dangelo
NEAR TERM...DeVoir/Fitzgerald/Dangelo
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...Evanego/Banghoff
AVIATION...Evanego/Banghoff




Area Forecast Discussion

National Weather Service Grand Junction CO

 440 PM MST Mon Jan 4 2021

.SHORT TERM...(Tonight through Tuesday night)
Issued at 255 PM MST Mon Jan 4 2021

Mid and upper-level clouds have drifted eastward into eastern Utah
and western Colorado this Monday afternoon. These clouds mark the
arrival of our next minor winter weather event, set to move
through the western slope tonight through Tuesday. Clouds will
continue to thicken this evening and overnight as a shortwave
trough dives through the northern Rockies. Light snow is expected
to arrive in the mountains of northeast Utah after midnight and
will spread east along the higher terrain of the US 40 corridor
overnight through the predawn hours on Tuesday.

A few trends have been noted with this event in recent mesoscale
model runs. First, the opportunity for intense convective snow on
the front end of this event appears notably lower. Forecast
soundings do not show much instability (by winter standards) as
the front passes, partly due to poor timing in the mid-morning
hours, and partly due to weaker dynamics aloft. Mid-level frontogenesis
fields as well as surface convergence are a bit lacking in
comparison to some of the more notable frontally-forced snow
squall events of late. The NAM remains more bullish for a
brief mid-morning window for SNSQ parameter space in northern
Colorado, however even the latest extended HRRR runs do not
indicate much in the way of surface banding. Therefore, confidence
is only low to moderate for intense snow squalls to materialize.

The other trend is for a slightly more extended period of broad,
light to moderate snowfall behind the front after it passes early
Tuesday morning. Model QPF totals have increased by around 10% or
so today, and snow totals in the current advisory for the Park
Range are on the upper-end of advisory criteria. Consideration was
given for an advisory for the Flat Tops as well, however will hold
off until the evening to see if the upward model trends continue.
The I-70 corridor from Vail to Vail Pass should also see around
3-5 inches of snow - not quite enough for winter highlights but
certainly enough for some minor travel issues on Wednesday. The
lower valleys from I-70 southward will not see much if anything
from this event, with only a trace or less in Grand Junction,
Montrose, and Gunnison. Flow will turn northwesterly on Tuesday
afternoon with light snow coming to an end in the mountains
overnight. Skies will clear quickly leading to a pretty cold night
with lows running 5 to 10 degrees below average.

.LONG TERM...(Wednesday through Monday)
Issued at 255 PM MST Mon Jan 4 2021

By Wednesday morning, Tuesday`s shortwave will have ejected eastward
and will be in the process of closing off and digging into the
central and southern Plains. In its wake, high pressure at the
surface and aloft will build into the Great Basin and Four Corners.
As a result, expect a return to quiet and tranquil weather under a
mostly sunny sky. High temperatures will be within a few degrees
either side of normal.

The next shortwave trough we are watching lifts out of the Pacific
Northwest and into the Intermountain West on Thursday. The 12Z
deterministic runs of the GFS, CMC and NAM12 all keep this feature
well to the north of the forecast area while only allowing for a few
light snow showers across the far northern mountains. This solution
is further supported by the 12Z GEFS. On the other hand, the 12Z
ECMWF, EPS and GEPS all depict a stronger and deeper wave with more
widespread precipitation farther south into the CWA. Given the model
discrepancies at present, opted to continue with a blended solution
for the time being. With that being said, even if the
stronger/deeper solution came to fruition, not looking at much more
than a minor event with sub-advisory snowfall amounts. Temperatures
on Thursday will remain near normal.

After that, much of the day on Friday is looking dry as shortwave
ridging briefly returns. Quick on its heels, attention then turns to
Friday night into Saturday when the potential for a more substantial
storm comes into play. The deterministic runs of the ECMWF, GFS and
CMC are all advertising a strong shortwave trough digging into the
Great Basin and Four Corners region before closing off. While the
means of their respective ensemble suites are smoothing out the
details at this range, all are now hinting at a closed low solution.
Still some time for details to become clearer, but its looking like
Saturday will be active with potentially significant winter weather,
especially in the higher elevations.

Sunday likely sees improving conditions with just some lingering
light snow showers in the mountains near the Continental Divide.
Beyond that, another system is possible either Monday or Tuesday of
next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 440 PM MST Mon Jan 4 2021

Mid and high level cloudiness spreading across E.Utah and
W.Colorado ahead of the next system moving in early Tuesday. The
biggest impacts appear to be over the ski country TAFs as the the
lower valley terminals should stay VFR...though temporary ILS
conditions are possible. KHDN to KEGE to KASE appear to be most
under the gun with MVFR or below likely to occur by mid morning
with KASE forecast to hit mins by 17Z. Improvement looks to arrive
by mid afternoon as this systems translates to the Plains. Some
post frontal winds could bring some gusts over 25 mph in some
areas behind the system by 20Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory from 11 PM this evening to 5 PM MST
     Tuesday for COZ004.

UT...None.
&&

$$

SHORT TERM...MAC
LONG TERM...MDM
AVIATION...TGJT



Area Forecast Discussion

National Weather Service Grand Rapids MI

 1040 PM EST Mon Jan 4 2021

LATEST UPDATE...
Update

.SYNOPSIS...
Issued at 255 PM EST Mon Jan 4 2021

- A weak cold front brings light snow showers overnight

- Shallow cold air behind front results in days of cloudy skies

- Patten of quiet weather may last through next week

&&

.UPDATE...
Issued at 1040 PM EST Mon Jan 4 2021

Not much change to previous thinking. What was once an
impressively solid line of precipitation over Wisconsin has now
mostly dissipated as it moves eastward from Wisconsin into Lake
Michigan. However, the HRRR and other short range guidance
indicate redevelopment of this line occurring in the vicinity of
US-131 in the 5 am to 6 am EST timeframe and then continued
movement of this line towards the east.


Accumulations still are expected to be on the order of a couple
tenths of an inch...but even a skiff of snow at this time of day
could have ramifications for the Tuesday morning commute,
especially where there might be patches of underlying ice. Will be
updating the hazardous weather outlook to mention this.

&&

.DISCUSSION...(This evening through next Monday)
Issued at 255 PM EST Mon Jan 4 2021

- A weak cold front brings light snow showers overnight

We have a weak cold front comes through the area tonight and will
bring light snow showers with it. The timing suggest the snow
showers will mostly from around midnight till around sunrise on
Tuesday.

In the larger scale of things, we have a digging northern stream
shortwave that ends up merging with several other systems near
the east coast, by Wednesday. This creates an Omega Block of sorts
over the CONUS. This initial shortwave that comes through this
area tonight, at upper levels, looks like a negative tilt
shortwave. Typically that would bring enhanced precipitation, but
in this case, we have limited mid level moisture. The cold air is
marginally cold at best (-6c 850 in early January is hardly what
I would call cold). The lift in the DGZ is pathetic at best. That
lift, what there is of it, is strongest between TVC and MKG, near
and west of US-131 around midnight.

The result of all this will be glorified snow flurries. Maybe we
can get few tenths of a inch of snow out of this. Most of the CWA
will see some snow overnight ( I would say there is a nearly 100%
chance of a trace of snow across the area but a less than 40% it
will be measurable). Once again it will be more like flurries then
anything that would really accumulate.

- Shallow cold air behind front results in days of cloudy skies

What happens here from Tuesday into early Friday, is we get a
really shallow layer of cold air (less than 6000 ft in depth) so
air temperatures will be warmer at 7000 ft above the ground than
at 3000 ft above the ground from Tuesday through Thursday. This is
not a good thing if you want to see sunshine anytime soon in
Southwest Michigan. So even though we will have a northeast winds
by Wednesday as a shallow Canadian high builds into the area.
Normally that would clear our skies. This time it will not. What
we get is temperatures that will stay between 28 and 37 degrees
(mostly near 33 actually) for the next 4-5 days.

Finally by Friday we get enough dry air from the Northeast to
clear the skies. However, then, another weak front comes through
and brings more clouds. So, if all goes well, we may have a few
hours of sunshine on Friday.

- Patten of quiet weather may last through next week

On a much larger scale, we have primary pool of cold air in the
northern Hemisphere taped under a large stable circulation over
northern and central Asia. That creates a series of strong
shortwaves and jet streaks that come off eastern Asia then track
across the Pacific, only to run into the upper ridge over western
North America. That results in split flow and hence our weather
pattern. This does look stable enough to last through most of next
week. If you like real winter weather, there is some suggestion
in the long range models (ECMWF weeklies/CFSv2 weeklies) that this
pattern will finally change the third week of January. It will
change in way that puts the center of the coldest air over North
America instead of Asia. That in turn will allow cross polar
flow (which brings Michigan it`s coldest weather). All of this
would mean we finally get some real west Michigan winter weather
the last 2 weeks of January. We shall see!

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 647 PM EST Mon Jan 4 2021

Poor aviation conditons will persist into the night with low
ceilings and visbys. While most areas are already at IFR ceilings
now, further drops in ceilings are expected with the passage of a
cold front this evening and overnight. This will bring ceilings
into the 200-500 ft range. Meanwhile, visibility will drop with
the passage of the front into the 1-2 mile range through Tuesday
morning. Light snow will also be possible, with accumulations of
around a dusting to 1/2 inch expected. Conditions will begin to
improve by Tuesday afternoon and evening.


&&

.MARINE...
Issued at 255 PM EST Mon Jan 4 2021

Our weak (pathetic) frontal system is just strong enough to result
in marginal small craft conditions in our northern Marine zones
while we are in the southerly flow ahead of the frontal system.
Once it comes through the marginally strong enough conditions for
Small Craft will extend over our entire Near Shore (mostly late
tonight into late afternoon on Tuesday). Once the winds go
northeast, they will stay that way into Thursday. So the next
event may be in the Friday time frame.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 4 PM EST Tuesday for LMZ844>849.

&&

$$

UPDATE...TJT
SYNOPSIS...WDM
DISCUSSION...WDM
AVIATION...Thielke
MARINE...WDM



Area Forecast Discussion

National Weather Service Lincoln IL

 748 PM CST Mon Jan 4 2021

.SYNOPSIS...
Issued at 744 PM CST Mon Jan 4 2021

A cold front will push across our area this evening, moving out
much of the fog that has recently plagued the region. High
pressure will build into the Midwest behind the front. Other than
a few periods of fog, dry conditions are expected through the rest
of the week. Temperatures are expected to be near seasonal
normals for early January.

&&

.UPDATE...
Issued at 748 PM CST Mon Jan 4 2021

Weak band of light freezing sprinkles/snow has reached near I-55
this evening and should exit the eastern CWA before midnight.
Visibility has markedly improved along and west of this band, and
the west half of the dense fog advisory has been cancelled. The
east half remains in effect until 4 am, though high-res models are
more mixed as to how much this will go away.

Clearing line has edged into far western Illinois this evening,
and HRRR suggests potential for it reaching the Illinois River
valley after midnight before some renewed stratus development,
especially from Peoria north and west. Backed off some on the sky
cover, though will keep it partly cloudy there after midnight.

&&

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 218 PM CST Mon Jan 4 2021

Strong inversion remains anchored over central Illinois allowing
only sporadic improvements to visibility. The inversion was
reinforced by warm advection aloft. A weak surface feature will
push east across the forecast area overnight. Drier air will
advect into the area behind the feature improving the foggy
conditions.

Temperatures should be mostly near normal with the exception of
the area between I-72 and I-55 where several inches of snow still
need to melt.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 218 PM CST Mon Jan 4 2021

Models remain consistent in splitting incoming energy toward
midweek. The southern system is expected to pass just south of the
area Wednesday Night and Thursday and will likely enhance the
potential for clouds and fog. Relatively weak flow will be in
place for most of the rest of the week with periods of clouds and
near normal temperatures.

Models do begin to diverge a but toward day 6 and 7 with
differences on the intensity and impact of a northern stream
system. Will need to monitor this system as it approaches toward
the end of the week - for now will keep things dry.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 511 PM CST Mon Jan 4 2021

Dense fog covering a large portion of the TAF sites early evening
except for KCMI, which should go down soon. A weak frontal
boundary will sweep from west to east late evening, and should
allow for some improvement in visibilities, though some additional
dense fog may occur closer to 12Z and will include a TEMPO period
for this chance. VFR conditions expected to finally return toward
18Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 4 AM CST Tuesday for ILZ038-043>046-
052>057-061.

&&

$$

UPDATE...Geelhart
SYNOPSIS...Barker/Geelhart
SHORT TERM...Barker
LONG TERM...Barker
AVIATION...Geelhart



Area Forecast Discussion

National Weather Service Marquette MI

 638 PM EST Mon Jan 4 2021

.SHORT TERM...(This evening through Tuesday)
Issued at 407 PM EST MON JAN 4 2021

WV imagery and RAP analysis indicated a low amplitude split flow
pattern with nrn stream mid/upper level trough from northeast
Manitoba into MN/IA. At the surface, a trough extended from
northwest Ontario through western Lake Superior into northwest WI.
800-600 mb fgen ahead of the mid level trough supported a narrow
band of snow from the MN arrowhead through far western Upper
Michigan that has dropped vsby to around 1SM as it moves through.
Otherwise, southerly flow ahead of the trough as maintained low or
allowed low clouds to spread through the rest of Upper Michigan.

Tonight, expect the trough and associated area of snow to spread
west to east through Upper Michigan with snowfall amounts less than
a half inch. Over the east, there may be period of fzdz preceding
the snowband as sw low level flow off of Lake Michigan brings
additional moisture into the area. As the deeper moisture departs
late this evening and overnight, some fzdz may also develop over
northwest Upper Michigan, especially where convergent upslope wnw
flow is strongest.

Tuesday, lingering shallow moisture and 850 mb temps in the
-6C to -8C range will support continued potential for fzdz/dz in
areas favored by northwest flow over the west in the morning and in
the east into the afternoon. Under persistent clouds, temps will
still remain above normal with highs in the low to mid 30s.

.LONG TERM...(Tuesday night through Monday)
Issued at 335 PM EST MON JAN 4 2021

For winter recreation enthusiasts, this snow season has been a big
disappointment so far. Unfortunately, the outlook is bleak for
snowfall across Upper MI for at least the next 10 days. In fact,
despite being Jan, it will even be difficult to get an air mass in
here cold enough to generate any LES. The main culprit to the warm
conditions and blo normal snowfall across Upper MI since the
beginning of Nov has been the flow across the N Pacific. A strong
Pacific jet and a persistence of negative height anomalies across
the ne Pacific (and extending westward across basically all of the N
Pacific to Asia for that matter), has largely kept the Lower 48
awash in Pacific air and has prevented any sustained build up of
Arctic air to the n in Canada. This +EPO pattern has been the prime
driver of the warmth and blo normal snowfall for the last 2 months,
and has muted the responses of the AO which has been negative since
the beginning of Dec and the more recent -NAO. Often, a -AO supports
lower heights in the mid latitudes of N America and thus increased
potential for arctic air to push southward, and a -NAO is also a
colder signal as it supports lower heights across the ne portion of
the Lower 48. Not only will conditions across the ne Pacific not
change for at least the next 10 days, but there will also be an
expansive area of strong positive height anomalies at 500mb
developing over the e half of Canada. End result will be a pattern
that prevents a buildup of arctic air in Canada and even prevents
much southward push of any notably colder air at all. Split flow,
which has also been dominant across the Lower 48 and southern Canada
for the last couple of months, will also continue with the more pcpn
active southern stream way to the s of here. So, for the next 7 to
10 days, above normal temps and much blo normal pcpn will be the
rule for Upper MI...certainly, a quiet and warm pattern for Jan
standards.

Beginning Tue night, mid-level ridge will be approaching the western
Great Lakes in the wake of the shortwave passing tonight/Tue. Temps
at the base of an inversion based at 3-4kft are fcst to be near -9C,
marginal at best for any LES with Lake Superior water temps around
4C. Of course, with temps only as low as -9C, there`s no guarantee
of ice nucleation to result in snowflakes if pcpn occurs. With sfc
high pres ridge arriving over western Upper MI, will leave fcst dry
in that area. Over the e, low-level flow across the e half of Lake
Superior, at least during the evening, is cyclonic, and this might
support some flurries/patchy -fzdz into the n central and ne fcst
area. Otherwise, fcst soundings suggest plenty of stratocu/stratus
will linger across the area, even over the w where high pres ridge
arrives. Leaned more toward the higher end of guidance for min
temps, but if any interior locations clear out, temps could easily
fall off toward 10F.

Mid-level ridge will then setup shop across the northern Great Lakes
on Wed/Thu and probably on into Fri. At the sfc, associated high
pres ridge will settle over Upper MI, extending from building sfc
high pres center shifting from far northern Ontario to northern
Quebec. Result will be tranquil days with light winds. Given little
advection of drier air heading into Wed, it`s quite possible stratus
will dominate the area for both Wed and Thu and maybe Fri, and if
not, fog development may be an issue at night. At this point,
leaning toward low clouds dominating, especially Wed/Thu, with any
breaks mainly in areas that see some downsloping, though
downsloping will be weak with winds light. Thus, kept diurnal
ranges on the lower side with expectation of clouds holding
daytime temps down and conversely nighttime temps up. There will
be fairly big temp bust potential on the min temp side if there
is less cloud cover than anticipated right now.

Over the weekend and into early next week, a couple of northern
stream shortwaves may try to dig se into the Great Lakes region. CMC
and GFS are more aggressive with these waves into the Great Lakes
than the ECMWF has been. If the former are on track, there will be a
couple of opportunities for some -sn and maybe some LES, but even
these solutions lack any decent push of colder air for LES. The
ECMWF with support from the UKMET suggests dry weather will
prevail, and fcst will favor that idea. So, it`s possible that
after some light pcpn tonight/Tue, there may be no measurable pcpn
Wed thru Mon.
&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 630 PM EST MON JAN 4 2021

At KIWD, MVFR cigs are expected through the forecast period. A few
lingering flurries are possible this evening.

At KCMX, a brief period of snow showers this evening could result
in temporary IFR vsbys, but otherwise winds veering to an upslope
west-northwest direction behind a cold front will support MVFR
cigs through the period.

At KSAW, LIFR strata deck could lift to IFR later this evening
as a low pressure trough moves across the area. A period of snow
showers could bring MVFR to IFR vsbys as well. As winds veer to
the northwest tonight, expect some improvement to at least low
end MVFR cigs.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 407 PM EST MON JAN 4 2021

SW winds of 20-30 knots late this afternoon will diminish tonight
and veer to the west as a trough moves eastward through Lake
Superior. Behind the trough, northwest winds of 15 to 25 knots are
expected late tonight into Tue morning before diminishing to less
than 20 knots.  After that, winds will remain unseasonably light
across the lake through at least the end of the week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

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




Area Forecast Discussion

National Weather Service Nashville TN

 954 PM CST Mon Jan 4 2021

.UPDATE...
FOR 00Z AVIATION DISCUSSION.

&&

.DISCUSSION...

Radar showing some light reflectivity returns to our northwest, as
well as southwestern middle TN. Sfc reports, however do not concur
with any rainfall reports. Latest HRRR shows more respectable
returns firing up aft 06Z, mainly across the Plateau area.
Thus, current pop and wx grids appear to be in good shape.

Latest sfc temps are generally in the 40s with dewpoints in the
mid 30s to lower 40s. Our current overnight min temp fcst appears
to be on track as well. No changes to the fcst at this time.

&&

.AVIATION...
00Z TAF DISCUSSION.

VFR conditions are expected at airports for a few more hours
before a MVFR cloud deck spreads across terminals after 09Z.
Models continue to be too aggressive on ceiling heights and have
will only show MVFR cigs in TAFs due to low confidence. A few
showers will pass near CSV around sunrise with VCSH. Otherwise,
light westerly winds early in the TAF period will become northwest
up to 11 knots on Tuesday morning.

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION......21
AVIATION........Shamburger