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January 15th-17th 2024 Arctic Blast/Snow Event


John1122
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MRX disco:

 

An upper 300mb jet streak strengthens to over 140 kt into Monday
morning with broad upper-level divergence across the Tennessee
Valley and Southern Appalachians. Lower-level flow will become
convergent in response to this divergence and result in widespread
isentropic lift with light to moderate precipitation on Monday
across the region. Deterministic QPF amounts for Monday show a
likely range of 0.2 to 0.5 inches across much of the area which
is expected to fall as all snow across most of the area based on
model forecast soundings. With these QPF amounts, at least 2 to 5
inches of snow appear likely across most of the forecast area and a
Winter Storm Watch has been issued for these locations. The most
uncertainty is across our far southeastern counties which will not
have as much deep cold air in place. They may have some mixed
precipitation which would limit overall snowfall totals.
Therefore, confidence in snow totals for these counties is lower
and they are not included in the watch at this time. The
ECMWF/GFS/GDPS all show a band of 0.5 to 0.8 inch QPF, and depending
on where this band sets up, some areas could see higher than
currently forecast snow totals. Counties within the Winter Storm
Watch all have at least a portion of the county above a 50% chance
of 2 inches of snow. Portions of the valley and plateau have above
50% chances of seeing at least 4 inches of snow.

A low pressure system will develop along the Gulf Coast and move
northeast towards the Carolinas on Monday night into Tuesday.
Depending on the track of this low, we may or may not see additional
precipitation on Tuesday. At this time, we are less confident in
snowfall amounts on Tuesday than on Monday, but expected additional
QPF and snowfall appears minimal at this time, most likely 0.1 inch
of QPF or less. This may add an additional inch or two of snow to
mainly our far eastern counties near the mountains along the TN/NC
state line.
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OHX:

 

An upper level system to our west will then approach mid state
region as Sunday night through Monday progresses, eventually
pushing east of our area as day on Tuesday progresses. Lows on
Sunday night will range in low to mid teens. Highs on Martin
Luther King Jr Day will range mainly low to mid 20s. Lows Monday
night will be in low to mid teens. Highs on Tuesday will actually
be even colder than Martin Luther King JR Day, ranging upper teens
northwest to lower 20s elsewhere. Models coming more into line
with potential of an accumulating snowfall event across mid state
region during Sunday night through Tuesday morning time frame.
Best potential of accumulating snowfall will be as Martin Luther
King Jr Day progresses. Because models trending toward a common
depiction of snowfall and snowfall potential across our area, and
in coordination with surrounding offices and WPC Winter Weather
operations, have issued a winter storm watch for accumulating
snowfall amounts ranging from around 3.0 inches up to 4.5 inches
across mid state region during this time period. Some lingering
snow showers may persist across Cumberland Plateau Region on
Tuesday afternoon with flurry chances to its west, but no
additional snowfall accumulations expected presently.
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The NAM loves to amp stuff too hard in the mid-long range. It's pretty bad outside 48hrs. RGEM can do it too on occasion but is typically more reliable.

 

Globals have definitely ticked flatter since 12z yesterday. I full expect the NAM to cave at some point. RGEM is a beauty and is right in line with most overnight globals

All of the energy will be coming onshore by 00z tonight so I'll be treating 00z as the first run to take seriously for amounts and locations.

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5 minutes ago, Vol4Life said:

Thank you for posting.  How does that compare with the previous model run?  Specifically orientation of storm and qpf.

I think it sagged the precip axis a little south and cut down on qpf:

0z qpf on the left, 6z on the right:

PpmSdEg.png

 

I'm not too concerned with that just yet. NAM is still waaayyy amped and RGEM is a nice compromise between the two. 

IMO this is going to be like some of what I call the Freaking Flooding February set ups we had in some of the past Springs. Not so much that we will get like 4-7" of qpf, but there will be a "snow hose" set up somewhere in the TN Valley and that qpf maximum will fluctuate based on things like terrain, the exact location/ strength of the jet that is facilitating this lift, and small vorticity maximums swinging through in the mid levels. as long as nothing makes a huge shift today, it's probably just a wait and see where it sets up and follow short term models. 

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Yesterday, I was reading some on another forum covering the Chicago snow (can’t remember where I saw it), but was talking about the NAM being the only one not on board with a major snow). It ended up beating all the other models.  
 

It’s interesting because our system is projected so much further north than other modeling on the NAM.  If it continues to stay north, will be fascinating to see if it can score a similar victory.

 

I will say I have seen numerous overrunning setups in the past be further north and/or have that SW to NE trajectory vs the WSW to ENE trajectory once it starts developing.  The good thing is, we don’t have to wait too much longer to find out.  

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Yesterday, I was reading some on another forum covering the Chicago snow (can’t remember where I saw it), but was talking about the NAM being the only one not on board with a major snow). It ended up beating all the other models.  
 
It’s interesting because our system is projected so much further north than other modeling on the NAM.  If it continues to stay north, will be fascinating to see if it can score a similar victory.
 
I will say I have seen numerous overrunning setups in the past be further north and/or have that SW to NE trajectory vs the WSW to ENE trajectory once it starts developing.  The good thing is, we don’t have to wait too much longer to find out.  

Chicago got absolutely screwed and the NAM had it right?


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Suppressions concerns me.  The NAM "should" be the furtherst NW given its bias.  I can't think of another model that would be that far NW.  So that is the northern side of the cone.  My area has moved from the SE side of precip to the very NW edge on a lot of modeling this morning.  My guess is that modeling is now feeling the cold air push this....I also guess this will jog just so much further SE and then begin to trend NW agains IF modeling bias holds to what it used to be...and that is a big IF..

The trend overnight on pretty much all modeling is SE in small or even moderate steps.  Maybe the place to be is on the SE side of the snow axis.  

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I'm not sure who remembers AM Weather (really showing my age), but it was primarily an agricultural/aviation weather program I'd watch before school every morning in the winter time.  This map is a fancy version of what you'd see on that program.  I like it because it's old school.  lol

 

Winter Storm Map NOAA 01132024, valid Monday January 15, 2024.gif

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18 minutes ago, tnweathernut said:

That was my understanding, but I'm not sure what lead time the person was talking about.  If it was less than 24-36 hours that's a lot different than NAM had it nailed from 84.

I know its more Mesoscale but the NAM blew away the GFS and Euro the last tornado outbreak here,it did very well into its extended range.Im not saying its gonna be the same outcome as this,i'm just saying

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