• Hello, please take a minute to check out our awesome content, contributed by the wonderful members of our community. We hope you'll add your own thoughts and opinions by making a free account!

Wintry 1/20 - 1/23 Winter Storm

BMX AFD. To phase or not to phase, that is the question. Major impact differences to north/central AL. Low confidence in solutions right now.

Thursday night through Friday night:

Models generally remain in their camps regarding the Friday
shortwave, with the GEFS and European ensembles generally
following their respective deterministic models. It continues to
boil down to whether the shortwave is phased or unphased, which
determines if mid-level flow is southwesterly or west-
southwesterly, with implications for where moist isentropic lift
occurs and whether this is over the cold dome at the surface, and
whether an 850mb low forms over far southeast AL/southwest GA.
Will note that the GFS has some mid-level moisture and
frontogenesis/omega a bit to the northwest of where it has QPF,
and it is sometimes a bias of the model to not be far enough to
the north with QPF in these over-running situations. But the
overall confidence remains low. Expect mainly dry conditions
Thursday evening, with temperatures falling well below freezing
across the northwest half of the area. In the southeast counties,
cloudcover and a wind shift from northwest to northeast bringing
in a slightly less cold air mass in advance of the wedge will keep
temperatures a bit milder. General model consensus at this time
between midnight Thursday night and 6 AM Friday has the surface
freezing line setting up somewhere near approximately a
Dallas/Lowndes county up through Randolph/Chambers County. While
the highest precipitation chances are southeast of this line,
indicating rain, there is a chance there could be an overlap for a
stripe of freezing rain along the northwest side of the
precipitation shield with some wet bulb effects possibly coming
into play. Temperatures would then rise above freezing Friday
morning, but if precipitation is falling generally over the
northeast quadrant of Central Alabama by Friday afternoon and
Friday evening thermal profiles would support a wintry mix in this
area. This remains a conditional threat, but overall I think
there`s too much moisture close to too much cold air to not
mention a low confidence threat in the HWO.
 
I can’t remember the storm right off the top of my head but it was sometime in the later 2000’s or early 2010’s where a storm almost exactly like this showed a big snow storm along and south of 85 with the biggest snows back towards Greenwood and the midlands. In fact most of the models had the moisture line at the NC/SC border with places like GSP only getting a couple of inches. As the storm approached it followed model guidance but there was way more moisture on the NW side as the cutoff was actually the NC/TN border. We went from WWA to winter storm warnings in the middle of the event and got at least half a foot or more. Precip almost is always under modeled on the NW especially when WAA is one of the main drivers of it. See this last storm as an example.
 
Wulfer said:
Step 1 Chattanooga in the game with temps. (usually the hardest part.)
Step 2 Drive moisture up high enough to hit Chattanooga.
Step 3 Moisture over run longer than 2 hours.


This is what we deal with in Chattanooga and the reason my signature is properly named.

Looks like we've accomplished step 1 for Wed- Sat. this week.
Click to expand...

Step 1 cannot be emphasized enough lol. Cold chasing moisture and "just in time" cold always underperforms. Established cold is our ticket.

With arctic boundaries, there are two things I have consistently observed over the years.
1) They slow down and 2) don't push quite as far south as modeled - that opens the door to the NW trend for upstream waves.

Plus with overrunning, precip almost always ends up WELL north and west of what's modeled. January 28th 2014 was a prime example.
 
KyloG said:
EPS SLP trend past 4 runs. More progressive...the low over Greenland has been bouncing back and forth too
View attachment 107751
Click to expand...

Likely less stream interaction, fold to the gfs in my opinion. I'll just never rely on a well timed phase for my snow. Still may work out but my confidence is growing, this is an off the coast, late blooming Raleigh storm.
 
bouncycorn said:
View attachment 107726

View attachment 107727


Holy smokes, this is gonna be a monster!
Click to expand...
I like these maps that show the 850 freezing map contours! I am not a meteorologist by any means and have not acquired the skills yet to read the data and models like many of my fellow posters here have. If I see the 850 line in a weather map it gives me a good idea of where the frozen stuff might fall versus the cold rain in these storms. Looking at these maps it appears that for now, Raleigh and surrounding areas might be in the money with this storm. Keep it up and simpletons like me can keep up with the models with maps like these and the accumulation maps I see so often on here. Of course, once these storms begin, actual observations are the way to keep up with trends that might occur.
 
12z Blend of Models
snowfall_acc.us_ma.png

framexp_acc.us_ma.png
 
cyclogent said:
Step 1 cannot be emphasized enough lol. Cold chasing moisture and "just in time" cold always underperforms. Established cold is our ticket.

With arctic boundaries, there are two things I have consistently observed over the years.
1) They slow down and 2) don't push quite as far south as modeled - that opens the door to the NW trend for upstream waves.

Plus with overrunning, precip almost always ends up WELL north and west of what's modeled. January 28th 2014 was a prime example.
Click to expand...
Robert (WxSouth) has preached that for years. He called the Feb 2010 and Jan 2014 IMBY. None of the models showed much my back to Huntsville and he kept on saying it would fill in. The rest is history.
 
iGRXY said:
I can’t remember the storm right off the top of my head but it was sometime in the later 2000’s or early 2010’s where a storm almost exactly like this showed a big snow storm along and south of 85 with the biggest snows back towards Greenwood and the midlands. In fact most of the models had the moisture line at the NC/SC border with places like GSP only getting a couple of inches. As the storm approached it followed model guidance but there was way more moisture on the NW side as the cutoff was actually the NC/TN border. We went from WWA to winter storm warnings in the middle of the event and got at least half a foot or more. Precip almost is always under modeled on the NW especially when WAA is one of the main drivers of it. See this last storm as an example.
Click to expand...
I think you’re referring to the February 12, 2010 storm. That one was supposed to be completely an I-20 and south and then coastal sections of the Carolinas, then starting about 36 hours out the models really started expanding the snow back to the north and west to the point that about 18 hours out GSP issued WWAs for the SC upstate and southern NC Piedmont and then kept expanding them throughout the day before upgrading a large portion to WSW. I ended with just over 5” after not having anything forecasted 30 hours before. The funny thing is that I remember Frank Strait at Accuweather had been adamant all week that the snow would extend up to the I-40 corridor even though the models weren’t showing it
 
Another thing is there is a difference between the NW precip shield expanding and a NW trend....just because the NW edge of the precip moved does not mean there was a NW trend with the low track....if this ends up being a weaker strung out system there will be a rather large expansion of the NW precip shield.
 
Downeastnc said:
Another thing is there is a difference between the NW precip shield expanding and a NW trend....just because the NW edge of the precip moved does not mean there was a NW trend with the low track....if this ends up being a weaker strung out system there will be a rather large expansion of the NW precip shield.
Click to expand...
Yea, people get this confused sometimes, imo.

The Euro might nail the 5h pattern, but bust on the northern extent of qpf. It definitely happens a lot with the ukmet.

All the verification scores you can find that show Euro/Ukmet dominance... are 500mb height scoring. Not qpf scoring. (If there is qpf scoring somewhere I'd be interested in the link!).
 
Will the nws start posting winter storm watches tonight or tmrw am?


Sent from my iPhone using Tapatalk
 
SnowNiner said:
Likely less stream interaction, fold to the gfs in my opinion. I'll just never rely on a well timed phase for my snow. Still may work out but my confidence is growing, this is an off the coast, late blooming Raleigh storm.
Click to expand...
The thing is even though there was less phasing on the Euro, the GFS is still trending more NW with the low and the precip and that is gaining support on the GEFS. More than likely we’re probably headed towards a blend of the Euro/GFS/CMC where there is still plenty of moisture back here to the west from overrunning to put down a decent snow with temperatures in the 20s, but the heaviest QPF is east of Hwy 1 where things are aided by the phase. The big question whether or the WAR plays nice and stays backed off to keep the warm nose at bay more
 
EmersonGA said:
Robert (WxSouth) has preached that for years. He called the Feb 2010 and Jan 2014 IMBY. None of the models showed much my back to Huntsville and he kept on saying it would fill in. The rest is history.
Click to expand...
Yep, and precip shield is almost always more expansive to the NW than what is depicted on the models. Seent it many times.
 
rburrel2 said:
Yea, people get this confused sometimes, imo.

The Euro might nail the 5h pattern, but bust on the northern extent of qpf. It definitely happens a lot with the ukmet.

All the verification scores you can find that show Euro/Ukmet dominance... are 500mb height scoring. Not qpf scoring. (If there is qpf scoring somewhere I'd be interested in the link!).
Click to expand...
Finally someone with some prestige said it. The term "nw trend" is so over used but rarely explained. More times than not it's only the precip field has expanded nw not the Low itself, although that does happen. Robert did a real good job explaining this back in the day when he hung out in these lowly forums before going big time. Thanks Burrel!
 
A blend of the GFS/EURO is my call as of right now. Maybe not as amped as the EURO has been but definitely not a sheared out mess like the GFS either. Guess where that paints the best temps and highest QPF together? I'll let you take a guess but it's that long road at the base of them mountains to our NW.
 
You must log in or register to reply here.
Back
Top