Flooding Continues in Arenac County Along the Rifle River

                        

344

ACUS01 KWNS 211628

SWODY1

SPC AC 211627



Day 1 Convective Outlook

NWS Storm Prediction Center Norman OK

1027 AM CST Sat Dec 21 2024



Valid 211630Z - 221200Z



...NO SEVERE THUNDERSTORM AREAS FORECAST...



...SUMMARY...

Isolated lightning flashes are possible through this afternoon along

the Oregon coast and vicinity.



...OR coast and vicinity through this afternoon...

A midlevel shortwave trough and associated thermal trough will move

inland over WA/OR through the day.  Isolated lightning flashes

occurred earlier this morning in northern CA with convection/minimal

buoyancy rooted above the 700 mb level, though this threat appears

to already be diminishing.  Through this afternoon, colder midlevel

temperatures and associated steeper low-midlevel lapse rates will

spread inland over coastal OR where isolated, low-topped

thunderstorms will be possible.



..Thompson/Bentley.. 12/21/2024



$$






                

                        

018

ACUS02 KWNS 211716

SWODY2

SPC AC 211714



Day 2 Convective Outlook

NWS Storm Prediction Center Norman OK

1114 AM CST Sat Dec 21 2024



Valid 221200Z - 231200Z



...NO SEVERE THUNDERSTORM AREAS FORECAST...



...SUMMARY...

Severe thunderstorms are not expected on Sunday.



...Synopsis...

Broad upper ridging over the central CONUS will begin to break down

through the day Sunday as a shortwave trough, currently moving into

the Pacific Northwest, traverses the Rockies. A broad surface high

building over the eastern CONUS will maintain cool/dry conditions.

Weak lee troughing over the High Plains will promote gradual

moisture return along the TX Gulf coast, but moisture quality/depth

and poor mid-level lapse rates will be insufficient to support deep

convection. A pronounced upper wave noted over the northern Pacific

in water-vapor imagery will approach the West Coast through the

period. Latest forecast guidance suggests sufficient destabilization

for a few lightning flashes is possible as colder temperatures aloft

and broad scale ascent overspread the region. The potential for

severe convection remains low given very limited buoyancy.



..Moore.. 12/21/2024



$$






                

                        

700

NWUS53 KAPX 211504

LSRAPX



Preliminary Local Storm Report

National Weather Service Gaylord MI

1004 AM EST Sat Dec 21 2024



..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...

..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....

            ..REMARKS..



0700 AM     Snow             2 SE Elmira             45.05N 84.82W

12/21/2024  M4.5 Inch        Otsego             MI   Cocorahs



            Cocorahs station MI-OT-19 Elmira 2.2 ESE.



0700 AM     Snow             1 NW Waters             44.91N 84.72W

12/21/2024  M3.7 Inch        Otsego             MI   CO-OP Observer



            CO-OP Observer station APXM4 Gaylord 9 SSW.



0800 AM     Snow             2 N Suttons Bay         45.00N 85.65W

12/21/2024  M3.0 Inch        Leelanau           MI   Cocorahs



            Cocorahs station MI-LL-8 1 NNE Suttons Bay.



0700 AM     Snow             1 NW Fife Lake          44.58N 85.37W

12/21/2024  M3.0 Inch        Grand Traverse     MI   CO-OP Observer



            CO-OP Observer station FLAM4 Fife Lake 2

            WNW.





&&



$$












                

                        

823

FXUS63 KAPX 211750

AFDAPX



Area Forecast Discussion

National Weather Service Gaylord MI

1250 PM EST Sat Dec 21 2024



.KEY MESSAGES...



- Brief very cold spell today into tonight, with highs in the

  teens today, and potential for sub-zero lows tonight.



- Potential is increasing for a widespread snowfall late Sunday

  night through Monday evening as another system passes through

  the region.



- Trending warmer and drizzly for the remainder of the forecast

  period, including the Christmas holiday. Snowpack likely

  erodes substantially as temperatures and dewpoints become

  stagnant above freezing.



&&



.UPDATE...

Issued at 1128 AM EST Sat Dec 21 2024



Morning Synopsis: Classic lake aggregate heating pattern across the

Great Lakes this morning.  14Z surface analysis shows a 1038mb

Arctic high north of Lake Superior...sub-zero cold surrounds Lake

Superior and leaking southward into the upper Mississippi Valley.

Meanwhile heating induced trough axis runs northwest-southeast from

the Keweenaw Peninsula across northern Lower/southwest Ontario and

eventually into northwest Pennsylvania.  Core of the coldest air is

east of Lake Superior but a chilly -19C at 850mb off the 12Z APX

sounding (-17C at DTX).  Boundary layer trajectories are mostly out

of the north...as a result better banding occurring in the vicinity

of Grand Traverse Bay with snow shower coverage having diminished

farther east.  Winds on eastern Lake Superior have a bit of an

easterly component which has pushed existing convective bands west

of Whitefish Point...and clouds for that matter west of the I-75

corridor with sunny and cold conditions across eastern Chippewa/

eastern Mackinac counties (except Drummond Island with clouds coming

in off the North Channel).  Elongate PV anomaly along 120kt jet axis

from northeast Manitoba south into Wisconsin...though just sending

high clouds southeast into the upper Lakes.  Thicker clouds farther

upstream into western Minnesota/Dakotas associated with onset of

warm advection.



Forecast Update: Pressure gradient weakens today as Arctic high

remains over northern Ontario...overall boundary layer flow

gradually becomes more anticyclonic with time.  Upstream PV anomaly

moves central Upper/western Lower Michigan by late afternoon/early

evening.



Most persistent snow shower activity this afternoon will be along/

west of the US-131 corridor which will benefit from a persistent

multi-lake trajectory and some decent though shallow thermodynamics.

Will also see some snow showers/flurries off Lake Huron into

northeast Lower for a while...though with low level winds

forecast to back more to the northwest eventually this may get

pushed offshore. Interior northern Lower has seen some thin

spots in the clouds though cloud cover should be reinforced by

diurnal heating cycle. Off Lake Superior most cloud cover

through early afternoon will remain west of I-75...but

eventually as winds shift more to the northwest some of this

will probably get pushed back toward the east. Temperatures at

ANJ/CIU finally climbing above zero...and suspect it will be a

struggle for those areas to rise out of the single digits this

afternoon. Warmest spots this afternoon will be west of US-131

where temperatures are already around 20F.



&&



.SHORT TERM /THROUGH TONIGHT/...

Issued at 240 AM EST Sat Dec 21 2024



Pattern Synopsis and Forecast:



Longwave troughing will slide eastward as high pressure with

arctic origins builds in through tonight. Drier air tracking

into the region will work to scour out low-level moisture while

gradients slacken to decrease winds, putting an end to any

lingering lake effect showers for most by at least this

afternoon (holds on across the Leelanau peninsula, Grand

Traverse, and Benzie counties). Through today, clouds will begin

to clear with most having partly to mostly clear skies by

tonight. Even though some may see the sun today, drainage

northerly flow will keep temperatures cold with highs largely in

the mid teens to lower 20s. Heading into tonight, clearing

skies combined with fresh snow (for some) and north winds,

overnight low temperatures look to drop substantially after

sunset, setting the stage for a very chilly night with lows in

the single digits to negative double digits across northern

Michigan, especially looking at the typical colder spots for

northern Lower (Pellston, Grayling, Atlanta, etc.). Looking at

wind chill values, looks like some could potentially reach close

to the negative teens after midnight in the early hours of

Sunday.



&&



.LONG TERM /SUNDAY THROUGH FRIDAY/...

Issued at 240 AM EST Sat Dec 21 2024



Pattern Synopsis / Forecast:



Ridging amplifying over the central Plains will be in the

process of forcing a deep longwave trough eastward, ushering in

warm and moist advection via southerly flow into the region as

an arctic borne surface high moves eastward into New England. A

strong Pacific jet (180-200kts) will lead to a subtle shortwave

trough moving eastward across the Plains and into the Great

Lakes late Sunday night into Monday. Favorable jet dynamics

should support cyclogenesis and surface pressure falls over the

Great Lakes through Monday... and coupled with an ample

southerly WAA tap (potentially originating in the western Gulf)

colliding into the hind end of the departing arctic airmass

should lead to plentiful lift to support a widespread snowfall

across much of the area late Sunday night through early Monday

night. Eventually, the aforementioned Pacific jet will really

flex its muscles as it belches a milder and drizzly regime into

the region just in time for the Christmas holiday, likely

lasting through the remainder of the forecast period.



Primary Forecast Concerns:



Sunday through Monday Night: Southerly return flow should be in

full swing as we head through the day Sunday, quickly

overwhelming the very cold start expected (see Short Term for

Saturday night cold). Guidance seems rather bullish on moisture

return interacting with those still quite warm Great Lakes... so

while not quite looking to be your typical system predecessor

SSW flow lake effect event is anticipated, some precip is

anticipated over western Mackinac county through the day on

Sunday. Latest guidance has JUST enough saturation within the

DGZ to make me lean to light snow and eliminate freezing

drizzle, but it`s close. Considering temps will be in the 20s,

this should be monitored closely.



Eventually, the larger system moves into the region, and should

bring a much more impressive saturation layer (PWATS balloon as

high as 0.50", and saturation stretches to dadgum near

300mb...). With northern Michigan precariously placed in the

divergent quadrants of two jet streaks, expectation is that this

system probably really blossoms right over the top of us. In

addition, with that impressive 850mb flow, strong theta-e

advection clashing with the departing arctic airmass could lead

to a narrow band of heavier snowfall via frontogenesis. This

signature shows up well on current long term guidance... most

spots have anywhere from 0.15-0.25" of QPF from this system,

with a narrow signature showing 0.45"+ of QPF. Considering the

timing of this system (likely overlaps the Monday morning

commute) and the consistency of the snow (very wet / sloppy),

this could be a more impactful event for the region even though

most places get probably a few inches of snow (where that band

sets up could certainly see a bit more... potentially in the

realm of 5-7"+ if everything comes together perfectly). This

activity will taper later in the day Monday... and with

continued warm air advection, not anticipating a lake effect

response on the backside of the system.



Rest of the Period: Minimal pressure gradient likely leads to a

stagnant airmass on the heels of the system... will have to

watch for any lingering moisture to present a drizzle threat,

and we may have to watch those temperatures Monday night into

Tuesday. Latest guidance has lows Monday night into the 20s,

which, if there`s drizzle, presents icing concerns. Eventually,

the warm air advection regime really kicks into gear... highs

Tuesday peak near freezing to the mid 30s, and increasing into

the upper 30s to mid 40s by Thursday (the day after Christmas)

through the remainder of the forecast period. Considering the

moist nature of the airmass, not expecting much of a fall in

temperatures overnight once this regime locks into place...

which, with continuous temperatures and dewpoints remaining over

freezing, will be incredibly detrimental to the existing

snowpack... and if these trends hold, could mean that much of

the area probably sees bare ground a few days after Christmas...

which is very unfortunate considering the economic draw that

the holiday week brings for winter activities across the region.



&&



.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...

Issued at 1246 PM EST Sat Dec 21 2024



MVFR ceilings to persist at KTVC/KAPN/KMBL this afternon along

with some snow shower/flurry activity. Most persistent snow

showers have been around KTVC as one last band...while now

oriented north-northeast just hasn`t been able to push west of

the airport although radar suggest this band should be on its

last legs. Eventually expect land breeze development to push

ongoing lake convection offshore and...should...result in

prevailing VFR ceilings into Sunday morning.



&&



.APX WATCHES/WARNINGS/ADVISORIES...

MI...None.

MARINE...None.



&&



$$



UPDATE...JPB

SHORT TERM...NSC

LONG TERM...HAD

AVIATION...JPB/NSC






                

                        

464

ACUS11 KWNS 191549

SWOMCD

SPC MCD 191548

WIZ000-MNZ000-191845-



Mesoscale Discussion 2273

NWS Storm Prediction Center Norman OK

0948 AM CST Thu Dec 19 2024



Areas affected...far southeastern Minnesota into west-central

Wisconsin



Concerning...Heavy snow



Valid 191548Z - 191845Z



SUMMARY...Areas of heavy snow with rates around 1" per hour to

continue through the late morning.



DISCUSSION...Bands of moderate to heavy snow are ongoing across

portions of southeastern MN into west-central WI. The heaviest snow

appears to be focused near the MN/WI/IA border where upper-level

divergence from a mid-level shortwave is leading to greater forcing

amid deep moist convergence. HREF guidance indicates that rates will

come down into the afternoon as upper-level support shifts

southward, before the backside of the low shifts across the region

later in the afternoon/evening when rates may increase again.



..Thornton.. 12/19/2024



...Please see www.spc.noaa.gov for graphic product...



ATTN...WFO...MKX...ARX...MPX...



LAT...LON   44769223 44589279 44049233 43749159 43529082 43379004

            43649010 44049035 44439087 44769223