Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/26/21

Area Forecast Discussion

National Weather Service Columbia SC

 1001 PM EST Mon Jan 25 2021

.SYNOPSIS...
A warm front over the central Midlands this evening will lift
northward through the northern Midlands overnight. A cold front will
push into our area on Tuesday and stall. Surface low pressure will
develop over the Southeast and bring more widespread showers
Wednesday into Wednesday night. High pressure will build into the
southeastern states late in the week into the weekend bringing cool,
dry weather.

&&

.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
Update: Warm front making little progress through the central
Midlands this evening. As a result visibilities have
deteriorated across the eastern Midlands. Have included
portions of the eastern Midlands in the Dense Fog Advisory. Both
the HRRR and RAP indicated the warm front slowly lifting north
through the early morning hours. Low visibilities may linger
across the northern Midlands and Pee Dee Region through the
predawn hours.

Previous Discussion: A warm front, bisecting the Midlands this
evening will move northward overnight. Wedge-like conditions
affecting the Northern Midlands and Pee Dee Region will hold low
clouds and fog in place until the warm front lifts north. No
significant rainfall is expected for most of the night given
weak isentropic lift. However, may see the chance for showers
return across the Piedmont and western Midlands toward dawn as a
cold front approaches from the west. A non-diurnal temperature
trend is expected with temperatures actually warming across the
north Midlands as the warm front lifts north. Low temperatures
should range from around 50 near the SC/NC border to the lower
60s across our southern counties.

&&

.SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY/...
A weak cold front move into the forecast area (FA) on Tuesday.
It will be a warm day with ridging aloft and warm advection
ahead of the front. Expect highs to generally be in the mid 70s.
As the main surface low shifts further north, the front will
slow and eventually stall near or over the southern forecast
area. Possibly along a line from AGS to MYR. Warm, moist
low-levels and weak convergence along the front will support
shower activity, the bulk of which will shift southward during
the day with the front. Coverage should be rather scattered with
westerly 850 mb flow and little upper level support.
Thunderstorms will be possible given the warm, moist conditions
near the surface. SFC LI values around -1 to -3 with SFC based
CAPE values around 500+. The highest thunderstorm chances will
be in the southern FA which will be in the deepest part of the
sector for much of if not the entire day. Weak conditional
instability and lack of upper level support will limit the
severe weather threat.

The stalled front will be picked up by an upper level trough
moving into the eastern US on Wed. In response, an area of low
pressure will develop along the frontal boundary across the
Carolinas during the day on Wednesday. Increasing moist
south/southwest flow will develop across the are Tuesday night
into early Wednesday. Showers are expected to be more widespread
with this system than the one on Tuesday. Rainfall is likely
from early Wednesday morning into the late afternoon hours.
Showers may be heavy at times with PW values approaching 1.5
inches Accumulations should generally range from 0.5 to 1.0
inches will locally higher amounts. Models suggest the warm
sector should remain south of the area in southern GA and
possibly into the Lowcountry. In addition, overcast skies and
rain should keep temperatures in the mid to near 60 degrees.

Depending on the timing of the colder drier air behind the
system on Wednesday/Wednesday night. Parts of the Midlands and
Central Savannah River could experience record high low
temperatures for Tuesday the 26th.

The record high low temperature at Columbia is 60 degrees set in
1943.

The record high low temperature at Augusta is 63 degrees set in
1943.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The area will get a reprieve from clouds and rain from
Wednesday night through Saturday. Behind the system on Wednesday
night, seasonably chilly high pressure will settle southward
from central Canada into the OH Valley and into the Carolinas
through Saturday.

This pattern supports dry weather with temperatures near or
below normal Thursday through Saturday. Another vigorous system
will eject from the southwest part of the country and move
northeast toward the Great Lakes Sat into Sun. This will bring
another chance for showers Sat night into Sunday. Temperatures
will warm slightly so that most locations will see temperatures
around/slightly above normal for Sunday and Monday.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
03z Update: Made a couple of minor tweaks to the 03z amendment.
1, I pushed the arrival of the low MVFR cigs back an hour
everywhere. Guidance is a bit slower than it was earlier. It has
developed across Alabama and Georgia ahead of the front, so
confidence is high that it`ll move into the area late tonight.
Additionally, added VCSH to all the TAF sites. I may be a bit
slow to bring that everywhere but OGB, but I didn`t want to
complicate the TAFs. CAMs generally bring showers into the area
between 12z and 15z, and a bit later at OGB. Otherwise, the
forecast is on track.

Previous Discussion: Slow moving warm front that was bogging us
down in restrictions earlier today has now progressed north of
all TAF sites, albeit only marginally. This has allowed warm air
to filter into the region, and has helped to lift cigs into VFR
(generally in the 4000-6000 foot range). This is expected to
continue as we head into this evening. Uncertainty develops
overnight, as most guidance hints at the redevelopment of cig
restrictions across the area. This looks to occur as more
moisture advects into the region ahead of an approaching surface
cold front. The severity and duration of these restrictions is
up for debate, though, and guidance is very inconsistent on
those two things. Still, almost all bring cigs down again for
some time tonight. The best overlap is for low MVFR cigs at all
sites, beginning at AGS/DNL around 07z and at CAE/CUB/OGB around
09z-10z, and lasting through early afternoon. Some guidance
(such as the HRRR) only keeps restrictions in through 14z, but
has them as IFR cigs. Others (GFSLamp/CONSShort) have a longer
duration event (through 19z-21z) with cigs around 1200-1500
feet. I tried to split the difference as much as possible, and
trend towards IFR cigs in case more guidance latches onto that
idea later. Either way, it looks like cigs restrictions will be
the main issue during the period.

Towards the end of the period, the passage of the cold front should
help alleviate any restrictions we still have. I have a feeling OGB
will be a tough one tomorrow, as the cold front will be arriving
later there, and will be slowing down quite a bit. Winds ahead of
this front will be breezy beginning later tonight. Expect generally
southwest flow, with 6-10 knots rising to 10-14 knots by mid
morning. Gusts of upwards of 20 knots can be expected. This will
wind down towards the end of the period as the front passes and
the sun sets.

EXTENDED AVIATION OUTLOOK...Periods of restrictions expected
through Wednesday night as additional systems move through the
region.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Dense Fog Advisory until 4 AM EST Tuesday for SCZ016-022-029-
     031-038-115-116.

&&

$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99



Area Forecast Discussion

National Weather Service Cheyenne WY

 735 PM MST Mon Jan 25 2021

.UPDATE...
Issued at 731 PM MST Mon Jan 25 2021

Updated forecast for tonight to extend the coverage of fog for the
high valleys west of the Laramie Range. Rawlins, Elk Mountain, and
Arlington are all reported fog with visibilities below one mile.
Will continue to monitor webcams for visibilities dropping below
one half mile, but do not expect a considerable coverage &
duration of dense fog at this time. Otherwise, current forecast
looks. Lowered POP a bit with across the eastern plains with
accumulating snowfall looking unlikely at this time given very low
snowfall rates. A better chance for snow is possible Tuesday
afternoon and Tuesday evening, but amounts will be light.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 140 PM MST Mon Jan 25 2021

Current conditions...Cold front analyzed on surface analysis from
Cody to Rawlins to Laramie...south into central Colorado this
afternoon. Widespread low clouds in upslope easterly flow being
seen on satellite imagery across much of the CWA. Panhandle
airports still IFR/LIFR in stratus and fog...while Cheyenne just
came down as winds shifted northeasterly. These low clouds may
stay in for a while as HRRR Aviation product showing widespread
solid low conditions through at least Tuesday morning.

Latest HRRR and Hires NMM mesoscale guidance for PoPs mixed on
snow through the afternoon and overnight. HRRR showing only
scattered snow...while Hires NMM showing fairly widespread snow
across the Panhandle. Decided to keep going PoPs going as they are
through the overnight hours. Either way...not a lot of
accumulations expected and the NAM guidance has really backed off
on accumulations over the Panhandle. No winter headlines expected.

Light QPF seen on ECMWF along the I-80 Corridor for Tuesday with
heavier snow south in central Colorado. Would foresee conditions
similar to today with low clouds and cold temperatures as
southeasterly upslope flow continues. Winds don`t shift west until
Tuesday afternoon after 00Z.

For Wednesday...upper ridge begins to build into southeast
Wyoming with increasing 700mb westerly winds. Craig to Casper
850/700mb height gradients up to 52/40mtrs respectively Wednesday
afternoon with elevated winds for our wind prone areas. Right
now...do not think high wind headlines are needed as 700mb winds
only get to 40kts across southeast Wyoming...but bears watching.

.LONG TERM...(Thursday night through Monday)
Issued at 140 PM MST Mon Jan 25 2021

Mild conditions across the CWA Friday with an upper ridge slipping
to the east of the area. Weekend looks to see a return to cooler
and blustery conditions as a potent shortwave moves across the
southern Rockys into the southern and central plains. Pressure
gradients get in the 60-70m range Saturday morning so wind-prone
areas may see some strong winds. Not much in the way of pcpn with
this system here given its southerly track. Sunday and Monday
look to be dry and mild with upper ridging moving across in a
progressive flow pattern.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 421 PM MST Mon Jan 25 2021

Wyoming TAFS...VFR at Rawlins, with occasional MVFR until 03Z,
then IFR from 10Z to 15Z, then MVFR until 19Z, then VFR.

Occasional IFR at Laramie until 04Z, then MVFR until 16Z, then
VFR.

IFR at Cheyenne until 16Z, then MVFR.

Nebraska TAFS...IFR until 18Z, then MVFR.


&&

.FIRE WEATHER...
Issued at 140 PM MST Mon Jan 25 2021

Minimal fire weather conditions expected through at least Thursday
as cold temperatures remain in place. Some areas east of the
Laramie Range expected to receive at least a half inch of
snow...with portions of the Nebraska Panhandle receiving 1-2
inches. Warmer...drier and windier conditions to end the week with
temperatures climbing into the 50s in the Panhandle and mid 40s to
near 50 in southeast Wyoming. Still...afternoon humidity expected
to stay well above critical levels into the weekend.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

UPDATE...TJT
SHORT TERM...GCC
LONG TERM...RE
AVIATION...RUBIN
FIRE WEATHER...GCC



Area Forecast Discussion

National Weather Service Des Moines IA

 725 PM CST Mon Jan 25 2021

...Winter Storm Update...

.UPDATE...
Issued at 725 PM CST Mon Jan 25 2021

Moderate to heavy snowfall has been steady across much of central
into southern Iowa as strong lift through the dendritic growth
zone continues to make this event an efficient snowfall producer.
As of early evening the axis of heaviest snowfall has contracted
a little bit over central Iowa, but is still dumping snow at 1-1.5
inches per hour over locations in and around the DSM metro. RAP
model suggests a few more hours of these heavier rates are
possible with robust lift and supersaturation with respect to ice
through the DGZ. Peak snowfall intensity wanes by later this
evening, but light to moderate snow will linger overnight into
Tuesday morning as the forecast area remains under a zone of mid-
level confluence and positive PV advection aloft as the parent
upper low is slow to push through. Dry air entrainment into the
southern flank of the low may lead to a loss of ice in the cloud
layer over far southern into southeast Iowa, which could flip
ptypes over to freezing rain/drizzle. Short term model soundings
barely hang on to snow, but will continue to monitor and update as
needed.

The heaviest storm totals will be focused from southwest Iowa to
near the I-80 corridor in central Iowa. SLR reports suggest a
higher SLR snow in this area compared to further south and east.
The higher snowfall rates this evening mostly overlap the same
locations that have seen heaviest snowfall so far, so expecting
that we will see reports of a foot or more in some locations by
Tuesday morning. Dry air continues to eat into the northern edge
of this system, drastically limiting snowfall potential in
northern Iowa. Some snowfall may eventually make it as far north
as Algona and Mason City, but amounts will be light compared to
the rest of the area.

&&

.DISCUSSION.../Tonight through Monday/
Issued at 242 PM CST Mon Jan 25 2021

...Impossible Travel at Times into Tonight over Southern and
Central Iowa as Major Winter Storm Impacts the State...

Highlights:
-- Major winter storm bringing severe impacts including
 impossible travel
-- Light snow over southern Iowa Tuesday night/early Wednesday]
-- Very cold conditions Thursday morning
-- Another round of precipitation next weekend

Details:
GOES-East upper level water vapor imagery shows the shortwave trough
lifting over the western Plains this afternoon. A warm conveyor belt
is into the Ohio Valley while the cold conveyor belt extends back
through Iowa into Nebraska. At the surface, flow is from the
northeast advecting in dry air into the low levels. 12z RAOBS from
GRB, MPX, and ABR have a wealth of dry air in their profiles. The
12z DVN RAOB was becoming saturated, but still had dry air in the
800 to 500mb layer. Farther west and southwest, OAX and TOP
soundings were saturated with precipitation ongoing at 12z. Warm air
advection ahead of low pressure moving out of central Oklahoma and
lifting toward St. Louis by late today will help to saturate the
atmosphere gradually from south to north. High resolution soundings
have shown the dry air being eroded from top to bottom in the
profile with saturation and snow beginning late this afternoon or
this evening along the Highway 20 corridor and likely after midnight
along the Highway 9 corridor.

Once saturation does occur, snow rates will be intense with cross
sections showing deep layer of saturation with moderate to strong
lift within the dendritic growth zone. Snow rates from the 9z SREF
and 12z HREF show high probabilities of greater than 1"/hour snow
rates moving in from our southwest early this afternoon into the Des
Moines metro fizzling over central Iowa this evening. HREF snowband
probability is also showing this as well, though the demise of the
band and high rates is a bit sooner. This timeline of snow rates
lowering overnight seems reasonable given the decreasing lift shown
in the model cross sections.

Last night`s trend with the 00z suite of models was to lift the
snowfall northward. This trend has held this morning with the
alignment of the highest snow axis from southwest into central and
east central Iowa. The tight gradient remains over northern Iowa
with parts of our northern counties likely to have little if no
accumulation as dry air continues to advect in at low levels.
Farther south, National Blend was indicating some mixed
precipitation in our far southeast after midnight tonight.
Deterministic sounding data does not support this change over.
However, it is possible that some of the ensemble soundings do
lose their ice introduction if they bring the dry slot farther
north and into southeast Iowa. Observational trends will need to
be monitored for possible lower snow totals over the far south and
a change over away from snow. Overall, impacts will remain severe
with travel likely impossible late this afternoon into tonight
over southern and central Iowa with the high snow rates with
visibility reduction being enhanced and lowered due to blustery
winds blowing the snow. Snow totals have not greatly changed, but
with snow lingering tomorrow morning have pushed the advisory and
warning out until midday/18z. It is possible western portions of
these headlines can be cancelled early as snow ends from west to
east across the state, but travel impacts will likely linger
longer.

The shortwave trough dropping into the western US trough today will
advance eastward and pass through the central US around midweek.
While the bulk of the QG convergence will pass south of the state,
enough lift and saturation will occur over southern portions of the
state for some light snow. Accumulations are looking around or under
an inch for those areas.

High pressure moves across the northern and central Plains Wednesday
night into Thursday. This will create one of the colder mornings
with Des Moines right around 0 degrees. By late this week, a
longwave trough will be moving ashore the western US. Lee side
cyclogenesis will occur by Friday and this will help to aid in
milder air moving into the region along with a deep fetch of
moisture from the southern Plains/Gulf of Mexico. There are hints of
light QPF amounts as early as Thursday night into Friday as
isentropic lift increases over the state. More consensus that
precipitation, whether rain, wintry mix, or snow, will start Friday
night or early Saturday lasting through much of the day Saturday.

&&

.AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/
Issued at 527 PM CST Mon Jan 25 2021

Moderate to heavy snowfall will significantly impact flight
categories over the southern half of Iowa through the evening into
the overnight hours. Lighter intensity snow to the north may only
result in IFR to MVFR restrictions, but tempo LIFR cannot be ruled
out. Gradually improving conditions are expected as the snow
steadily moves out Tuesday morning and afternoon.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until noon CST Tuesday for IAZ033>039-
044>050-057>062-070>075-081>086-092>097.

Winter Weather Advisory until noon CST Tuesday for IAZ016-017-
023>028.

&&

$$

UPDATE...Martin
DISCUSSION...Ansorge
AVIATION...Martin



Area Forecast Discussion

National Weather Service Detroit/Pontiac MI

 957 PM EST Mon Jan 25 2021

.UPDATE...

After a few hours of delay during the late night, snow remains on
track to affect the morning commute in the Detroit metro area while
spreading quickly northward toward Flint, the Tri Cities, and
northern Thumb during the morning. A period of higher rate snowfall
is expected to limit visibility and produce hazardous driving
conditions.

Observations during the evening indicated some flurries managed to
drift north of the Ohio border only to be driven back by dry air in
the low levels. This is expected to delay onset of meaningful
snowfall until later in the night in our area. Meanwhile, the
combination of upstream observations and incoming model data is
building a more impressive case for a burst of heavier snow for SE
MI during the morning until early afternoon. Ongoing activity over
the Midwest is a combination of very respectable mid level
deformation acting on a well-developed 850 to 700 mb trowal
producing generous areal coverage of 1/2 to 3/4 sm snow in Iowa.
Incoming model data maintains the strength of this configuration
through Lower MI during the morning, sweeping through the Detroit
area then primarily affecting locations along and north of I-69.
Cross sections indicate a textbook profile of theta-e exhibiting low
stability within the trowal axis and convective potential along the
south flank centered on 15Z. This matches up with a broad area of
higher vertical motion in the 850-500 mb layer reaching 10-15 ub/s
in the latest 00Z NAM and RAP solutions. Low level moisture is
plentiful with 3 g/kg specific humidity reaching as far north as
Saginaw after 12Z. That being said, and as highlighted in the 4 PM
discussion, there is concern regarding snow to liquid ratio in this
case and the latest model soundings continue to support these
concerns. A shallow DGZ near the top of the moist layer, riming and
fracturing in a warmish low level thermal profile and a strong wind
profile below 700 mb are limiting factors for confidence in double
digit ratios. In-house probability guidance also points to lower
expectations on ratio, rate, and accumulation. Balancing the
observed dynamic forcing with ratio limitations suggests a cautious
boost in snowfall totals into the 3 to 5 inch range centered on I-69
northward along with inclusion of some stronger wording in the
advisory for higher snowfall rate. After an early morning burst,
intrusion of the dry slot still cuts off activity in the Detroit
area by 10 AM or so followed by pockets of freezing drizzle until
temperatures inch above freezing by early afternoon.

&&

.PREV DISCUSSION...
Issued at 705 PM EST Mon Jan 25 2021

AVIATION...

Low level dry air makes a fragile push from Ontario into SE MI which
acts to break up MVFR ceiling briefly during the evening. The dry
air also helps hold off the onset of snow for a couple hours longer
after midnight with some virga indicated on radar over the region.
However upstream observations depict an impressive pattern of snow
moving in from the Midwest which is expected to reach the southern MI
border after 06Z and then spread northward during the late night. At
least borderline LIFR/IFR visibility is expected at the peak during
early to mid morning. Conditions for freezing drizzle also continue
to look favorable as dry air surges into the mid levels over the DTW
corridor during Tuesday morning. It will be light using MVFR
visibility as a proxy for intensity until observations can offer some
additional guidance and before temperatures creep above freezing by
Tuesday afternoon. IFR ceiling and visibility hold otherwise as the
band of snow shifts northward toward FNT and MBS and lasts into
Tuesday evening.

For DTW... VFR below 5000 ft to occasionally MVFR is the condition
for this evening before ceiling lowers and snow begins 07-08Z. The
peak of the event occurs toward sunrise with visibility dropping to
around 1 mile a times and with accumulation around 2 inches most
likely before a transition to freezing drizzle occurs by mid morning.
Only very light icing is expected on top of freshly fallen snow
until temperatures rise slightly above freezing by Tuesday afternoon.

DTW THRESHOLD PROBABILITIES...

* High for ceiling below 5000 feet tonight.

* High for snow tonight and early Tuesday.

* Moderate for freezing drizzle mid to late Tuesday morning.

* Low for ceilings or visibilities to drop below 200ft or 1/2SM
  respectively.

PREV DISCUSSION...
Issued at 354 PM EST Mon Jan 25 2021

DISCUSSION...

Subtle height increases today in the wake of a passing cold frontal
boundary. This is leading to subtle upper height rises with dry and
stable conditions under lower level easterly flow through the
remainder of the daylight hours. Increasing mid to high clouds in
advance of the next system along with the resident thermal profile
is bringing temperatures this afternoon at or near the freezing
mark, which is right around seasonal averages.

Main focus for this forecast is on the upcoming winter system
expected to pass through southeast Michigan starting tonight and
continuing into tomorrow. The upper low in the lee of the Rockies
can be seen on satellite pushing the central plains this afternoon
with low level warm frontal zone producing widespread precipitation
across the Ohio Valley. This area of greater moisture and warm
frontal zone is expected to hold south of Michigan. However, a zone
of modest moist isentropic ascent is expected along a 800-700 mb
frontal zone that will cross through southeast Michigan tonight.
There will still be decent moisture feeding this frontal slope with
specific humidity values generally around 3 g/kg. Guidance leading
into this event has slowed the progression across the area with
later arrival times throughout tonight. Anticipate the snowfall to
lift across the OH/MI this evening sometime between the 8 pm to 10
pm time frame. Snowfall will then slowly expand northward through
the early morning hours with higher rate snowfall possibly not
moving over the I-69 corridor until about 3 am or shortly after.

Survey of forecast soundings through the event depicts somewhat
underwhelming thermal profiles in the moist layer (~925-600 mb) with
temperatures residing around -4 to -5 C across southern areas and
areas to the north at around -8 to -9 C. This would lean towards
snow to liquid ratios on the wet to normal side (8:1 to 12:1 range)
throughout this event. QPF totals through the event mostly come in
around the 0.20 to 0.35 inch range, which would result in snowfall
amounts mostly in the 1 to 4 inch range. The mid level dry slot
remains a concern with this event, which is forecast to push
northward Tuesday morning. This would effectively compromise the
higher end snowfall amounts and also bring a period of light
freezing drizzle as the mid level dry air strips moisture from the
DGZ. The light freezing drizzle scenario is especially true for the
southern portions of the forecast area, but impacts expected to be
limited given it will fall onto earlier snowfall. This has also lead
to latest guidance directing greater moisture/forcing and axis of
higher snowfall amounts along portions of the I-69 corridor and
points northward. Have made minor adjustments to the previous
forecast snowfall amounts with most of the area remaining under 4
inches. The overall character of this event at the moment remains a
borderline Winter Weather Advisory event with most locations
receiving 1 to 4 inches snowfall over 8 to 12 hours. The wintry mix
in the form of light freezing drizzle across the I-94 corridor and
to the south will bring minimal ice accumulations. Have opted to
just go forth with issuing a Winter Weather Advisory with the
potential impacts to the morning commute.

The synoptic forcing will weaken throughout the day Tuesday leading
to decreasing precipitation and lower rate snowfall as the wave
begins to shear out. A weakening frontal zone along with
northeasterly winds off Lake Huron will allow for some lighter
snowfall and additional light accumulations into the late afternoon
and evening time frame, especially across Saginaw Bay and shorelines
of the Thumb region. Lingering snowfall eventually comes to an by
Tuesday night. The mid to late week time frame places southeast
Michigan between southern and northern stream waves with generally
dry conditions. Some colder temperatures push into the region
bringing a stretch of below normal temperatures. High temperatures
generally in the 20s and overnight lows in the teens to single
digits.

MARINE...

Northeast winds will continue to be on the increase this evening as
low pressure moves into the Ohio Valley. Winds gusts still expected
to reach around 25 knots over Western Lake Erie, but with
precipitation drag issues tonight, 30 knots will probably not occur.
Even so, with the longer fetch, some 4 foot waves should brush the
nearshore zone. As the low continues north, northeast winds over
Lake Huron will also reach 25 knots tonight into Tuesday, especially
over Saginaw Bay where the fetch is maximized. The prolonged onshore
flow should have no problem with waves aoa 4 feet impacting the
nearshore waters, and small craft advisories remain in effect, with
the exception of inner Saginaw bay due to ice cover. In addition to
the increased wind and waves, snow will overspread the region from
south to north this evening into Tuesday, with visibilities reaching
1 mile or less at times.

As the low exits east, winds become northerly Tuesday night into
into Wednesday, but should mostly hover around 15 knots before
increasing again Wednesday evening into Thursday as cold blast leads
to increased mixing depths. Thus, there remains a good chance the
small craft advisory will need to be reissued or extended as waves
look to remain elevated through the end of the work.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...Winter Weather Advisory from 1 AM to 4 PM EST Tuesday for
     MIZ047>049-053>055-060>063-068>070-075-076-082-083.

Lake Huron...Small Craft Advisory until 5 AM EST Thursday for LHZ421-441>443.

Lake St Clair...NONE.

Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EST Tuesday for LEZ444.

&&

$$

UPDATE.......BT
AVIATION.....BT
DISCUSSION...AA
MARINE.......SF


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



Area Forecast Discussion

National Weather Service Huntsville AL

 819 PM CST Mon Jan 25 2021

.NEAR TERM...(Tonight)
Issued at 819 PM CST Mon Jan 25 2021

02Z mesoanalysis shows a CAPE axis just west of the MS-AL line, near
where a broken line of showers is firing over NE MS, and where a
cyclic supercell is ongoing near the MS Golden Triangle. Farther to
the east, a band of showers and storms has been ongoing between
Huntsville and Birmingham for the last several hours--perhaps along a
warm front of sorts--but these storms appear to have been mostly
elevated in nature. MU/MLCAPE and low-level lapse rates drop off
rapidly as you progress east, but mid-level lapse rates steepen
somewhat, shear is more than enough, and convergence is sufficient
to keep storms going. There were a few reports of penny to dime size
hail over Sand Mtn with earlier storms.

On the other hand, despite better convergence and a relative CAPE
max, the NE MS storms have struggled to intensify. The band of storms
to the south may be interrupting the inflow of rich high theta-e air
into the NE MS storms, limiting their potential. Additional
scattered showers (such as those developing over NW AL) may continue
to cut off the inflow.

The most recent HRRR run weakens the NE MS storms in favor of the
southern band as the evening wears on. It is also interesting that
the HRRR resolves a swath of 0-3km updraft helicity near where the
cyclic supercell is located in eastern MS, and brings it up into far
southern Cullman County late this evening (around 05Z). So while
storms across the southern CWA have been mostly elevated so far, it
is still possible that they will become more surface-based later
tonight--and the wind threat (and yes, tornado threat) may not be
over until later.

.SHORT TERM...(Tuesday through Wednesday night)
Issued at 205 PM CST Mon Jan 25 2021

Tuesday will be another mild day, but with sunshine as the frontal
band shifts to the Gulf Coast through southeast GA. Expect highs in
the middle to upper 60s. A shallow cold front will drop in Tuesday
evening as the area remains beneath strong southwest flow at 7-5h in
advance of the next wave ejecting from the desert Southwest. The
frontal band to the south will begin lifting northward as a low level
jet develops. However, much of this moisture transport will shift
through south AL into central GA/SC Wednesday morning into the
afternoon. Our area may see a few showers as the upper trough
quickly swings east and deamplifies through the TN valley during the
afternoon. Cold advection will increase by late afternoon and
evening, but not before subsidence and drying ends precipitation.
Thus, not expecting snowfall at this point in our area, but to our
northeast along the Cumberland Plateau. Much colder temperatures in
the 20s are expected Tuesday night into early Wednesday morning.

.LONG TERM...(Thursday through Sunday)
Issued at 205 PM CST Mon Jan 25 2021

Heading into the end of the workweek, a ridge will amplify across
the Plains as a trough deepens as it heads into the West coast. This
will leave us in NW flow aloft and the sfc high pressure building in
from Canada will bring a chill to the TN Valley. Look for daytime
highs on Thursday to be 10-15 degrees colder than Wednesday only
reaching the low to mid 40s. Despite plentiful sunshine, with breezy
northwesterly flow ~10kts gusting slightly higher, it will make it
feel even colder. Overnight lows will be chilly in the lower 20s. Dry
conditions will persist into Friday but with lighter winds as high
pressure moves in. The increase in heights and sfc winds becoming
southerly will help daytime highs reach the lower 50s.

The dry pattern won`t last long as a the previously mentioned West
Coast trough will weaken as it swings towards the region this
weekend but return showers to the forecast. With overnight lows
Friday night/Saturday morning hovering around freezing, we could see
a brief window around sunrise of a rain/snow mix before precip
becomes, and stays, all liquid. Breezy southerly flow will provide an
increase in moisture and push daytime highs into the mid 50s on
Saturday. As a sfc low lifts into the Midwest, we will see showers
increasing in coverage through the day, becoming numerous by
Saturday night ahead with an increase of isentropic lift ahead of a
warm front lifting northward. Showers will persist into Sunday
before the cold front moves through and brings precip to an end by
sunset.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 550 PM CST Mon Jan 25 2021

A bit of uncertainty exists for the TAF sites through the first 6
hours of the forecast period. Showers and thunderstorms ahead of a
cold front will move across the area this evening. Cigs are expected
to lower to MVFR over the next hour and cigs around 800 feet are
possible as the storms move through. At this point, uncertainty is
high as to the exact timing of storms and therefore have a TEMPO for
the KMSL between 01 and 04Z and at KHSV between 03 and 06Z.
Amendments may be necessary if storms develop sooner than expected.
Gusty winds and hail will be possible in any storm that impacts the
area. These storms will move east of the area by 06Z, with conditions
expected to improve to VFR by 09Z.


&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

NEAR TERM...BCC
SHORT TERM...17
LONG TERM...JMS
AVIATION...73


For more information please visit our website
at weather.gov/huntsville.



AREA FORECAST DISCUSSION

National Weather Service Jackson KY

 907 PM EST Mon Jan 25 2021

.UPDATE...
Issued at 907 PM EST MON JAN 25 2021

Showers and thunderstorms continue to move rapidly eastward across
the region, and the forecast still has this covered. Have adjusted
temperatures through Tuesday morning based on obs and latest model
guidance, but the changes are rather minor. Readings are expected
to be nearly steady in our southern counties tonight, and rising
in the north.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 541 PM EST MON JAN 25 2021

Surface low pressure over the Ozarks will shift eastward through
the overnight, riding up the Ohio River Valley. This slow moving
system will lift a warm front northward through eastern Kentucky
during the overnight period and then a cold front through the area
by Thursday morning.

WPC maintained an area of a marginal threat of excessive
rainfall for the Commonwealth through tonight. Additional
convection is firing upstream and short term high resolution
models show that activity riding northeast into and through our
area during the overnight. SPC mesoanalysis shows an upstream
environment of 250-500 J/kg MUCAPE and effective shear of 35-60
kts. RAP forecasts show this environment lifting northeast into
our area and SPC HREF suggests that mean 250-500 MUCAPE and shear
will lift into eastern Kentucky over the next several hours. Thus
maintained thunder through the evening as yet another round of
precipitation pushes through the region. Already seeing a few
stronger cells being highlighted by upstream WFOs. So an isolated
strong storm with mainly gusty winds can not be completely ruled
out. Brief, locally heavy rainfall will also be possible. Excessive
runoff will cause local streams and rivers to swell through the
day Tuesday. The current HWO has this handled.

Once we get through tonight, sensible weather settles down
considerably. Tomorrow, dry weather and sunshine will lift
temperatures to around 60 across the south, and in the 50s across
our north, where lingering clouds will help keep temps slightly
cooler.

.LONG TERM...(Wednesday through Monday)
Issued at 541 PM EST MON JAN 25 2021

We begin the extended portion of the forecast Wednesday in a brief
period of modest ridging aloft across the eastern Ohio Valley. Just
to our west, a shortwave trough rides over the Middle Mississippi
Valley. Ridging across the Rockies and western Plains separates this
shortwave trough from a deeper trough of the northwestern US coast.
The system at the surface that is currently bringing the widespread
rainfall in the near term will have moved well off to our east at
this point. Meanwhile, another area of low pressure will be
beginning to develop in the deep south.

The shortwave trough to our west will beginning to move over our
area through the day Wednesday, while the surface low will continue
to travel east and northeast across the Southeast, sending precip
towards our area. Generally, precip is set to begin impacting the
area not too long after 18z Wednesday afternoon. Most guidance is in
fair agreement over the pattern evolution, other than the Canadian
keeping the shortwave further to the west a little longer,
consequently delaying the initial onset of precipitation. However,
given that this solution is not as favored in ensembles, have
elected to put less stock in it. With the surface low passing to our
south, our area is kept in the cooler sector, allowing for some snow
to mix its way in. Generally this change over will happen as a
gradual transition from northwest to southeast, with the exception
of the higher terrain generally transitioning earlier. Accumulations
look to be modest, generally less than an inch, though higher
amounts are possible in the higher terrain.

Generally the precip will exit out to the east by Thursday morning
as the surface low pushes east off the coast. Heights aloft will be
on the rise through the day as ridging moves in from the west, while
high pressure dominates at the surface. All combined, conditions
will stay clear and dry through the first part of the weekend.
However, the dry weather does not last. Another upper level trough
will work its way towards the region over the second half of the
weekend, supporting the development of a low at the surface over the
Plains. This sends along our next round of precip, generally
beginning Saturday afternoon. However, while there is more agreement
over the general pattern, the specifics around the evolution of both
the features aloft and at the surface are still not well resolved.
So, have kept more in line with the thinking of the previous
forecaster and kept the PoPs constrained to just likely given all
the uncertainty.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 907 PM EST MON JAN 25 2021

Conditions at the start of the period ranged from VFR to LIFR,
with the better conditions generally in our southern counties, and
the worst in the north. Showers and a few thunderstorms continued
to move rapidly east over the region. Strong winds just off the
surface were bringing a threat of low level wind shear as well.

The precipitation will persist this evening, but is expected to
mostly move out to the southeast overnight. Wind shear should also
subside overnight. However, flight categories are expected to
worsen, with most places becoming IFR or worse overnight.
Improvement is forecast on Tuesday morning, with a return to VFR
for everywhere but north of I-64, with that scenario carrying over
through the remainder of the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...HAL
SHORT TERM...RAY
LONG TERM...HAS
AVIATION...RAY



Area Forecast Discussion

National Weather Service Louisville KY

 629 PM EST Mon Jan 25 2021

...Updated Aviation Discussion...

.Short Term...(This evening through Tuesday)
Issued at 345 PM EST Mon Jan 25 2021

Upper low over the Plains with an occluded 998mb sfc over SW
Missouri this afternoon. Triple point is near the Bootheel, with the
most solid precip shield north of the warm front in mainly central
Kentucky. We have had a few strong to marginally severe storms
across south-central Kentucky in a slightly better mixed
environment, but that has been worked over and the unstable air mass
is now confined to Tennessee.

Main concern through this evening will be just how much additional
rain falls, especially where the heaviest rain already fell across
south central Kentucky. We could be looking at 1-2 inches of
additional rainfall, and if it remains focused near the Western
Kentucky and Bluegrass Parkways as currently progged, impacts should
be limited to nuisance flooding. However, if heavy rain falls
farther south where we are now fairly saturated, there could be
more impactful flooding.

Spotty convection is developing over western Kentucky and western
Tennessee, and that pushes through late this evening. Latest HRRR
actually takes that batch of rain across south-central Kentucky,
which could raise flood concerns.

Precip ends after midnight as the dry slot cuts in, but temps will
remain nearly steady overnight. Sharp temp gradient expected to
persist Tuesday as southern Kentucky clears out under the stronger
westerlies aloft, while north central KY and southern IN remain
fairly socked in.  Better temp recovery in the south, where we could
touch 60 again, while southern Indiana will be stuck in the mid 40s.

.Long Term...(Tuesday night through Monday)
Issued at 252 PM EST Mon Jan 25 2021

Upper level ridging along the eastern seaboard and deep troughing
across south central CONUS will place the OH Valley under deep SW
flow at the beginning of the long term. A 5H closed low over central
US will continue tracking eastward, filling as it tracks over the
southern OH Valley and northern TN Valley. Best chances of precip
will begin Wednesday afternoon and continue through early Thursday
morning. Sounding profiles would suggest mostly rain south of the
Parkways and transitioning to mostly snow towards the I-64 corridor,
but a rain/snow mix is likely between the two. EPS/GEFS members
continue to show agreement on minor accumulations with up to 1 inch
possible along our northernmost counties in Indiana and most
locations receiving a half inch or less. Temperatures will fall into
the low to mid 20s in the cold air behind the front, so impacts will
likely include some slick spots on any untreated roads for the
Thursday morning commute.

Large amplitude ridging and Canadian high pressure moves over the
region Thursday through the start of the weekend bringing cold but
dry weather. Thursday will be the coldest with highs only reaching
into the low 30s across southern Indiana and mid 30s across central
KY. Friday morning will likely be the coldest morning of the week
with lows in the upper teens to low 20s, but afternoon temps will
recover nicely with the aid of WAA along southerly winds with highs
in the 40s.

Our next chance of rain will come Saturday as system approaches from
the Central Plains. This looks to be an all-rain event lasting
through Sunday. Finer details will come later as long range models
reconcile differences.

&&

.Aviation...(00Z TAF Issuance)
Issued at 625PM EST Mon Jan 25 2021

KLVX radar showing another round of showers and storms working
through the central Kentucky region. Expect to see ongoing RA or
TSRA through the evening hours as the warm front lifts northward. By
06z tonight, most precip should be exiting the region, but the low
ceilings and visibilities will stick around through the overnight
hours. Guidance is strong on fog development and low ceilings
keeping IFR or even LIFR possible during the 06-12z time period for
SDF, LEX, and HNB. Wouldn`t rule out some VLIFR conditions either if
vis drops below 1/2SM for some time. We will continue to monitor and
amend if needed. Ceilings will finally start to break up mid/late
Tuesday morning. Winds become more southwesterly tonight as the
cyclonic flow spins out of the region. Winds will be gusty tomorrow,
but mostly around 20kts for all terminals.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Short Term...RAS
Long Term...CG
Aviation...CJP



Area Forecast Discussion

National Weather Service Baltimore MD/Washington DC

 935 PM EST Mon Jan 25 2021

.SYNOPSIS...
Low pressure will pass through the area on Tuesday. An upper
level disturbance is expected to pass through the area Thursday
morning while low pressure develops well southeast of the area.
High pressure will gradually build toward the area early next
week. A storm system may impact the area next Monday.

&&

.NEAR TERM /THROUGH TUESDAY/...
EVENING UPDATE...
As noted in the 00Z upper air from KIAD, a warm nose has
developed around 850-mb which has led to more of a mixed wintry
precipitation event than earlier suspected. A mixture of
rain/snow was anticipated during the first phase of this system.
Thus, expect some of the snow totals to be cut down given the
widespread sleet reports from local spotters. 1 to 2 inches of
snow will be the more likely outcome across the region. There
currently is a brief lull in the action while upstream radar
imagery shows another healthy band of precipitation heading
across West Virginia. With the warm nose continuing to push
northward based on HRRR solutions, expect a mix of
sleet/freezing rain to be the main precipitation types during
the overnight hours. This will lead to hazardous travel,
especially on any untreated road surfaces.

PREVIOUS DISCUSSION...
There have been some notable trends in
the 12Z model cycle today, more importantly, for a colder
solution and also less QPF tonight with the heaviest precip
aimed at the upslope areas of the Appalachians. Observational
trends support this colder solution with sfc ridging still in
place and current dewpoints still in the upper teens at BWI and
lower 20s at DCA. It`s difficult to get all precip to be all
rain when dewpoints are still so low. To add to the uncertainty
is a deep isothermal layer right at freezing seen on model
soundings. Only a degree or two degree difference could make a
big difference in p-type and specific snow/ice amounts. Please
refer to our snow and ice forecasts at weather.gov/lwx.
Definitely expecting a period of wintry precip tonight before
precip turns lighter overnight and Tue as mid-level dry slot
moves in. Precip should end or if not exit the area by 18Z Tue,
although some drizzle may persist across northeast MD longer.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Tranquil conditions Tue night through Wed. Next upper level
trough will swing through the area Wed night into Thu morning with
light snow possible for areas south of U.S. Route 50.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
For Thursday, models continue to suppress most of the wintry precip
probabilities further south of our CWA. Any potential for
bombogenesis would be later than the onset moisture/decreasing
temperatures for our area to cause much of an issue. Still could see
a period of rain/snow mix early on Thursday with any moisture that
makes its way into the area along with temperatures forecasted to be
below freezing for most areas west of I-95. Conditions will continue
to cold and windy for the area Thursday night into Friday. A system
to our NE Friday could continue to allow the chance for a few
flurries to be mixed in with these gusty NW winds. Not expected much
in terms of impacts for this time period but a northern shift in the
track of the low pressure system could inhibit higher threat levels
for impacts Thursday into Friday.

High pressure builds in from the west Friday night and pushes
offshore by early Sunday morning. This will allow for our next
potential wintry system to take aim. With temperatures currently
forecasted to be in the upper 30s to low 40s across most of the area
Sunday, impacts for this system appear minimal currently. Onset
precip may start out wintry before moving over to all rain for most
of the duration of the event. With it still be 7 days out,
conditions and impacts may change with any shift in parameters.
Should be something to continue to monitor as we head closer to this
event.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
IFR with occasional LIFR conditions developing this evening
with a wintry mix of precip. Improving cigs Tue afternoon as
precip ends.

VFR conditions likely Thursday and Friday with some gusty NW winds
on Thursday before diminishing as high pressure begins to move
overhead for our area. Could see a few flurries and reduced
instances of visibility but it will be brief in nature.

&&

.MARINE...
Light and variable winds through Tue evening. Possible SCA Wed
in NW flow.

Possibility for gales for the water between a low pressure system to
our SE and an incoming high pressure from the west on Thursday.
SCAs likely Thursday and Friday with that mentioning of gales
possible. Winds will decrease Friday as high pressure briefly
settles overhead.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Winter Weather Advisory until 9 AM EST Tuesday for DCZ001.
MD...Winter Storm Warning until 7 AM EST Tuesday for MDZ001-501-502.
     Winter Weather Advisory until 9 AM EST Tuesday for MDZ013-014.
     Winter Weather Advisory until 10 AM EST Tuesday for MDZ003>006-
     008-011-503>508.
VA...Winter Storm Warning until 7 AM EST Tuesday for VAZ503-504-507-
     508.
     Winter Weather Advisory until 9 AM EST Tuesday for VAZ053-054.
     Winter Weather Advisory until 7 AM EST Tuesday for VAZ025>031-
     038>040-501-505-506.
WV...Winter Storm Warning until 7 AM EST Tuesday for WVZ050-055-
     501>506.
     Winter Weather Advisory until 10 AM EST Tuesday for WVZ051>053.
MARINE...None.

&&

$$
SYNOPSIS...LFR
NEAR TERM...LFR/BRO
SHORT TERM...LFR/JMG
LONG TERM...ADM
AVIATION...LFR/BRO/ADM
MARINE...LFR/ADM



Area Forecast Discussion

National Weather Service Marquette MI

 658 PM EST Mon Jan 25 2021

.SHORT TERM...(This evening through Tuesday)
Issued at 221 PM EST MON JAN 25 2021

Water vapor imagery and RAP analysis show a mid-upper level trough
over the western U.S. and a low amplitude ridge downstream over the
se portion of the U.S. Around a strong positive height anomaly/500mb
anticyclone just n of Hudson Bay, mid-level troughing wraps from nw
Canada se across northern Ontario and then off the east coast of
Canada. Between the troughing to the n and the se U.S. ridge,
confluent flow extends from the northern Plains eastward into the
Upper Great Lakes. This confluence is supporting sfc high pres
ridging extending from the Arctic through Saskatchewan southeast
into the Upper Mississippi Valley and Upper Great Lakes. As a result
with the slow progression eastward of this ridge, nw winds today
will veer n-ne tonight into Tue. Light snow/flurries have been
reported at KCMX, KIWD and KERY and noted on webcams out west and
east today. Expect little if any snow accumulation through this
afternoon based on very dry upstream 12z KINL sounding and fcst
soundings showing inversion hgts 2-3 kft with dry air blo it.

Northerly flow late today will veer to the nne to ne tonight. Fcst
soundings indicate that inversions will remain low tonight into
Tuesday at around 3kft. Combination of the low-inversion height and
dry upstream air advecting over the lake will continue to be
negatives for LES. However, the DGZ is fcst to dominate the cloud
layer, so SLRs should be on the higher side with the developing -
shsn/flurries. Light shsn/flurries will shift to the nne wind
snowbelts and remain that into Tue morning before winds become a bit
more northerly late Tue. Coverage will increase gradually tonight
into Tue morning into the north central U.P. as the low-level flow
becomes more cyclonic and convergent over eastern Lake Superior
mainly due to the development of a land breeze off Ontario. Still,
snow accumulations will be light tonight into Tue given the more
dominant negatives previously mentioned. Expect snow accumulations
out west to be generally a dusting to an inch tonight into Tue, with
maybe 1-2 inches of accumulation possible into Baraga and Marquette
counties where -shsn are more persistent and could be aided by
convergent flow.

Lows tonight should range from around 5F above interior w, where
there will still be some breaks in the clouds, to mainly the teens
elsewhere. Winds may veer sufficiently to the ene due to the Ontario
land breeze for lower clouds to scatter out over the far e, so temps
there may fall into the single digits as well. Highs Tuesday under
mostly cloudy skies and a northeast to north flow will range from
the upper teens west to the lower to mid 20s east half and south
central.

.LONG TERM...(Tuesday night through Monday)
Issued at 252 PM EST MON JAN 25 2021

Little to no change in the longterm forecast from the past few
cycles as Upper Michigan will see a prolonged period of light lake-
effect snow with temperatures trending slightly abv normal by the
weekend. Troffing in the west with slight ridging to the eastern
CONUS is leading to active southern stream as a train of shrtwvs
impacts the CONUS this week and into the weekend. An arctic high
will extend a ridge towards Upper Michigan as light northerly flow
will bring persistent, albeit light, lake-effect snow showers
through Wednesday night. This high pressure moves overhead Wednesday
night into Thursday, bringing some clearing skies and cooler night.
By Friday, this high will be to the east of the UP as return
southerly flow, brings a building ridge over Upper Michigan with
slightly abv normal temperatures Friday and Saturday. Another shrtwv
will move on shore in the desert SW Saturday, before lifting through
the Central Plains Saturday night into Sunday. There is a non-zero
chance that this system shifts north and moves through the UP, but
so far deterministic and ens means are keeping it to the south and
relatively weak.

On Tuesday night, first wave on the train will be exiting across the
northeast as the next wave ejects from the Rockies and into the
Central Plains. A closed mid-level low will be dropping south from
Ontario ahead of an arctic high pressure system as light northerly
flow continues over Lake Superior. With model 850mb temps between -
17 to -19C, and saturation in the DGZ, some LES will be seen. Dry,
Canadian air will be moving over the lake, though, as seen by the
inverted V soundings...so expect this to limit accums.

Under the split flow regime, this closed mid-level low is slow to
shift eastward as the Central Plains wave shifts through the
Appalachians. This will bring a prolonged period of 60 hrs or snow
of light lake-effect snow. This lake-effect snow will come to an end
Wed night across the east as ridging and rising heights start to
build into the west. This may bring some clearing, and with 850mb
temps near -18C, could be in store for a colder night as high
pressure shifts overhead. This high will slowly shift east through
Thursday as LES comes to an end across the east Thursday aftn. A
whopping 2 to 4 inches could be seen in the northerly wind snowbelts
through Thursday, as snow showers will be hindered by the drier air.
NAM has some run to run consistency on a convergent wind field
across the east for Wednesday, which could bring just slightly
higher snow totals, but not seeing anything close to advy levels.

As the ridge moves overhead Friday and Saturday, temps climb to
around 30 for some spots with some clearing skies. Models have some
differences, but some WAA ahead of the next shrtwv could bring some
light snow across the UP on Saturday as well as the increased
cloudiness. Otherwise UP will remain unscathed for the most part
from this shrtwv as models and their ens means show the wave
remaining to the south through the Ohio River Valley, as the UP may
pick up some lake-effect snow on the backside of the low.
&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 654 PM EST MON JAN 25 2021

Expect persistent MVFR cigs through the forecast period with n to
nne winds off of Lake Superior bringing lake effect clouds and
flurries into the TAF sites. As slightly colder air moves in late
tonight into Tue morning, a brief period of IFR conditions may be
possible.

&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 221 PM EST MON JAN 25 2021

High pres will slowly build toward Lake Superior over the next
several days with the ridge axis drifting across Lake Superior Thu
into Fri. Until the ridge passes, expect northerly winds to prevail,
though direction will vary between northwest and at times northeast.
Wind speeds will be mostly under 20kt, but expect some periods with
winds gusting up to 25kt. After the ridge passes, southeast winds
will be on the increase Fri night into Sat with the approach of
another low pressure trough from the Plains. Southeast winds will
increase to 20 to 30 knots, highest over eastern and north central
Lake Superior.
&&

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

$$

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



Area Forecast Discussion

National Weather Service Nashville TN

 535 PM CST Mon Jan 25 2021

.UPDATE...
FOR 00Z AVIATION DISCUSSION.

&&

.DISCUSSION...

A line of heavy showers is currently moving across Middle
Tennessee mainly north of I-40. These showers earlier produced
some strong winds at the surface, but they have since diminished
somewhat. An ACARS sounding for BNA taken at 1709Z shows very
little CAPE with nearly total saturation from the surface up to
about 650 mb. There is some speed and directional shear in the
low-levels, but at this time helicities aren`t excessive. A warm
front that moved northward through Middle Tennessee overnight has
become quasi-stationary near the TN/KY border, so most of Middle
Tennessee is now in the warm, moist sector. A pre-frontal trough
will swing through the mid state later this afternoon and evening,
and this will provide some focus for the expected storms. The HRRR
does suggest some convective organization along this boundary, but
given the lack of instability in this air mass, it still appears
that the primary threats are going to be wind-related. SPC
currently gives us a 5% risk of damaging winds and a 2% risk of
tornadoes in the marginal/slight risk area, which covers nearly
all of Middle Tennessee. Even though the bulk of the active
weather will move across and exit the mid state overnight, the
cold front won`t actually arrive until Wednesday. That`s going to
be our next chance of rain, with perhaps some snow for the
Cumberland Plateau Wednesday night. (It`s going to be another
battle of cold air vs. moisture.) After that, look for cooler
temperatures the remainder of the week, with perhaps a weekend
cold front representing our next chance of rain.

&&

.AVIATION...
00Z TAF DISCUSSION.

Showers and occasional storms will impact BNA/MQY/CSV through the
evening which will reduce vis to IFR conditions periodically. A
surface front will move through the area from west to east which
will shut off rain chances by 07z. Cigs will gradually improve to
VFR for the remainder of the taf period by the morning. Behind
the surface front winds will shift to the WSW.

&&

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

&&

$$

DISCUSSION......08
AVIATION........Reagan



Area Forecast Discussion

National Weather Service Pueblo CO

 730 PM MST Mon Jan 25 2021

.UPDATE...
Issued at 724 PM MST Mon Jan 25 2021

Based on latest HRRR and 00z NAM, plus persistent snow over nrn El
Paso County, will expand Winter Wx Advisory to include the entire
I-25 corridor and also the srn Sangres. Snow amounts on the low
end of the advisory range, but with heavier snow falling over much
of the area during/near the morning commute, impacts could be more
significant. Other than adding the advisory and making some minor
adjustments to snow amounts, forecast is in pretty good shape and
won`t be making any major changes.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 250 PM MST Mon Jan 25 2021

...More snow expected across southern Colorado tonight and Tuesday...

First storm has pulled east of the area with wrap around snow
continuing across the northeast portions of the forecast
area...across Kiowa county.  Roads have stayed fairly clear in spite
of some moderate snowfall at times.  This band will pull off to the
northeast late this afternoon through the evening.  Meanwhile,
convective snow showers have developed across the mountains this
afternoon which will continue to expand and become more widespread
as southern Colorado comes under the influence of the next upper low
across southern CA, which will lift northeastward through the Desert
Southwest towards the 4 corners region tonight, then across southern
Colorado on Tuesday. System develops 2 circulation centers as it
crosses the mountains Tuesday morning and the leading impulse
tightens up again across east central CO by mid day.  Once again,
the timing and exact track of this intensification will play a big
role in snowfall amounts.  Overall, this storm looks a little weaker
than the last as far as upglide and development of the wrap around
snow band/trowal.  But this system will also be colder with
persistent light snow expected to continue through Tuesday as
trailing energy moves across.  This could lead towards greater
travel impacts for the urban corridor of southern Colorado. Overall,
snowfall amounts are coming out on the light side of advisory range,
so will issue Winter Weather Advisory for the southeast mountains
and adjacent I-25 corridor from roughly Walsenburg northward.  With
some southeast to easterly upslope flow, expect some snow to spread
up the Arkansas River Valley of Fremont county and perhaps into
southern Chaffee county.  Current advisories do not include the
Sangre De Cristo mountains as of yet but an earlier storm
intensification, or stronger upslope could necessitate upgrades.
Northern El Paso county is another area to watch but for now we are
keeping higher totals on the southern slopes of the Palmer Divide. A
tad farther south track and the southern I-25 corridor down to Raton
could also get in on the action, but with less of an upslope
component down that way, have left them out for now. Expect some
improvement Tuesday afternoon as focus for the heavier snow shifts
eastward across the plains.

Tuesday will be much colder with persistent cloud cover across
southern Colorado.  High temperatures will likely stay in the 20s
across the lower elevations with teens and single digits across the
higher terrain.

.LONG TERM...(Tuesday night through Monday)
Issued at 250 PM MST Mon Jan 25 2021

Tuesday night...

The major shortwave with very cold air associated with it will be
exiting the CWA with only a few lingering snow showers over the
highest elevations of all mountain ranges. Some snow will still be
possible over the plains as well due to the wrap-around moisture
overrunning cold surface temperatures in the deformation zone. All
precipitation should completely exit the region by midnight with
clearing throughout early Wednesday morning.

Wednesday through Friday...

High pressure is going to dominate the area once the low pressure
system exits the region by  early Wednesday morning. Both of the GFS
and ECMWF models are picking up on a weak upper level low from the
subtropical ridge to the southwest over the Pacific Ocean that will
absorb into the ridge and could allow for some higher level
precipitous clouds over the region on Friday, while the mid and
lower levels remain very dry.

Friday night through Sunday...

All of the deterministic models are in relative agreement with the
timing of the next major shortwave trough to influence the CWA late
friday night, except that the ECMWF has this system moving into the
region about 3 hours earlier late Friday night. Due to the
orientation of this trough, most of the precipitation will be
confined to the mountainous areas of the CWA, especially for
Saturday morning, where the greatest amounts of snowfall will be
located on the southwestern facing slopes of the San Juan Mountains.
The low pressure center associated with this trough will propagate
quickly out over the Great Plains and not provide much in the way of
any snowfall for the plains within the CWA.

Sunday night through Tuesday...

A ridge will begin to build back in with warmer and drier conditions
for a majority of the CWA with only a few snow showers over the
Sawatch range due to some troughing to the northwest of the region.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 250 PM MST Mon Jan 25 2021

VFR conditions are currently dominating at all locations for the
moment. As the next low pressure system approaches, expect CIGs and
vis to drop into IFR criteria for COS as early as 01Z due to -SN/BR,
for PUB as early as 02Z, and for ALS as early as 03Z...and expect
these conditions to prevail throughout the rest of the forecast
period.


&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM MST Tuesday for COZ068-074-
075-084-088.

Winter Weather Advisory until 8 PM MST Tuesday for COZ076-077-
079>083-085>087.

&&

$$

UPDATE...PETERSEN
SHORT TERM...KT
LONG TERM...STEWARD
AVIATION...KT