Dec 5-6 Round Two? NAM brings "sling-shot" Upper Low into SW and the fun has just begun!

[snowstormcanuck]

_{p-type maps aren't out yet, but judging by the thickness lines on the 18z RGEM, it looks a bit warmer than the 18z NAM.}

[KeenerWx]

I will start to think that we are destined.

With that gradient on speed it resembles a 500+ mile lake effect snow band.

[KokomoWX]

Oh so close...

[Geos]

With that gradient on speed it resembles a 500+ mile lake effect snow band.

Exactly what I was thinking. That's a painfully thin band.

Interesting it looks like this model run gives Chicago a shot at lake effect.

[snowstormcanuck]

I am surprised if the bulk of frozen comes as snow. Looks more like a icy setup before the "big cat" pulls out of the west.

From just a cursory look at the sfc maps, I would have thought the same. However, looking at a variety of p-type outputs, that doesn't seem to be the case. Seems to be a RA-WTSN-SN transition zone.

[jhamps10]

Oh so close...

your telling me.... I'm right on the edge of that band too.... i'd be really pissed if Champaign Urbana or even Tuscola got 4-6" and here in Charleston you get 1-2! it really looks like a big long band of LES

[Central Illinois]

your telling me.... I'm right on the edge of that band too.... i'd be really pissed if Champaign Urbana or even Tuscola got 4-6" and here in Charleston you get 1-2! it really looks like a big long band of LES

NWS STL and NWS ILX are like night and day with the newest afd's

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE LINCOLN IL

314 PM CST SAT DEC 3 2011

.DISCUSSION...

ISSUED 314 PM CST SAT DEC 3 2011

THE PCPN WILL SPREAD NORTHWARD THROUGH THE PERIOD BUT NOT AFFECT NORTHERN AREAS OF THE CWA. COLDER AIR WILL FILTER INTO THE AREA AND THIS WILL CHANGE THE PCPN TO A MIX OF RAIN AND SNOW...AND THEN ALL SNOW. THE ALL SNOW AREAS WILL GENERALLY BE ACROSS THE CENTRAL PARTS OF THE CWA AFFECTING I-55 AND I-72...AND JUST NORTH OF I-70. SNOWFALL AMOUNTS APPEAR TO BE ON THE ORDER OF ABOUT TWO TENTHS OF AN INCH EVERY 6 HOURS. SO OVER THE 24HR PERIOD OF MON THROUGH MONDAY NIGHT...HIGHEST SNOWFALL TOTALS WILL BE LESS THAN AN INCH. WARM GROUND AND THE FACT IT WILL BE MIXED WITH RAIN AT TIMES WILL HELP TO LIMIT ACCUMULATION AMOUNTS. A MIX OF RAIN AND SNOW WILL STILL BE POSSIBLE IN THE SOUTHEAST ON TUESDAY AFTER THE SYSTEM FINALLY PULLS AWAY FROM THE AREA. AMOUNTS WILL BE MINIMAL.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE ST LOUIS MO

337 PM CST SAT DEC 3 2011

.DISCUSSION...

/330 PM CST SAT DEC 3 2011/

FOR NOW...HAVE TRIED TO KEEP THE UPCOMING FORECAST VERY SIMILAR TO

GOING FORECAST TRENDS (LEANING MORE TOWARD NAM/ECMWF SOLUTIONS)...

WHICH SUGGESTS SEVERAL INCHES OF SNOW ON THE N FRINGE OF THE PRECIP

SHIELD FROM THE NORTHERN OZARKS...THROUGH STL AREA...INTO CENTRAL

IL. HOWEVER...IT SHOULD BE POINTED OUT EVEN IF THE FASTER GFS AND

GEM SOLUTIONS VERIFY I DON`T KNOW IF WE`RE TOTALLY OUT OF THE WOODS.

FORECAST SOUNDINGS ARE SUGGESTING A DEEP ISOTHERMAL LAYER NEAR 0C

OVER OUR SE COUNTIES...AND A SLIGHT COOLING OF THE AMS DUE TO

DYNAMIC COOLING WOULD MAKE THE PRECIP TURN OVER TO SNOW AND OR A

WINTRY MIX FASTER...AND FURTHER S...THAN SUGGESTED USING PROGGED

LOW LEVEL THERMAL PROFILE/THICKNESSS VALUES.

[hm8]

Yanked this from C/W since the wxcaster maps aren't out yet

Imagine the sattelite picture of that if we could get a cloudless day....a 40 mile wide band of snow running from Texas to Toronto

[SchaumburgStormer]

NWS STL and NWS ILX are like night and day with the newest afd's

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE LINCOLN IL

314 PM CST SAT DEC 3 2011

.DISCUSSION...

ISSUED 314 PM CST SAT DEC 3 2011

THE PCPN WILL SPREAD NORTHWARD THROUGH THE PERIOD BUT NOT AFFECT NORTHERN AREAS OF THE CWA. COLDER AIR WILL FILTER INTO THE AREA AND THIS WILL CHANGE THE PCPN TO A MIX OF RAIN AND SNOW...AND THEN ALL SNOW. THE ALL SNOW AREAS WILL GENERALLY BE ACROSS THE CENTRAL PARTS OF THE CWA AFFECTING I-55 AND I-72...AND JUST NORTH OF I-70. SNOWFALL AMOUNTS APPEAR TO BE ON THE ORDER OF ABOUT TWO TENTHS OF AN INCH EVERY 6 HOURS. SO OVER THE 24HR PERIOD OF MON THROUGH MONDAY NIGHT...HIGHEST SNOWFALL TOTALS WILL BE LESS THAN AN INCH. WARM GROUND AND THE FACT IT WILL BE MIXED WITH RAIN AT TIMES WILL HELP TO LIMIT ACCUMULATION AMOUNTS. A MIX OF RAIN AND SNOW WILL STILL BE POSSIBLE IN THE SOUTHEAST ON TUESDAY AFTER THE SYSTEM FINALLY PULLS AWAY FROM THE AREA. AMOUNTS WILL BE MINIMAL.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE ST LOUIS MO

337 PM CST SAT DEC 3 2011

.DISCUSSION...

/330 PM CST SAT DEC 3 2011/

FOR NOW...HAVE TRIED TO KEEP THE UPCOMING FORECAST VERY SIMILAR TO

GOING FORECAST TRENDS (LEANING MORE TOWARD NAM/ECMWF SOLUTIONS)...

WHICH SUGGESTS SEVERAL INCHES OF SNOW ON THE N FRINGE OF THE PRECIP

SHIELD FROM THE NORTHERN OZARKS...THROUGH STL AREA...INTO CENTRAL

IL. HOWEVER...IT SHOULD BE POINTED OUT EVEN IF THE FASTER GFS AND

GEM SOLUTIONS VERIFY I DON`T KNOW IF WE`RE TOTALLY OUT OF THE WOODS.

FORECAST SOUNDINGS ARE SUGGESTING A DEEP ISOTHERMAL LAYER NEAR 0C

OVER OUR SE COUNTIES...AND A SLIGHT COOLING OF THE AMS DUE TO

DYNAMIC COOLING WOULD MAKE THE PRECIP TURN OVER TO SNOW AND OR A

WINTRY MIX FASTER...AND FURTHER S...THAN SUGGESTED USING PROGGED

LOW LEVEL THERMAL PROFILE/THICKNESSS VALUES.

I read ILX's AFD earlier while waiting for LOT to get one published, and was boggled. They appear to be completely disregarding the possibility of accumulation while neighboring offices are jumping on the bandwagon. Interesting...

[Central Illinois]

I read ILX's AFD earlier while waiting for LOT to get one published, and was boggled. They appear to be completely disregarding the possibility of accumulation while neighboring offices are jumping on the bandwagon. Interesting...

Yea interesting to say the least.... The morning afd mentioned the potential for accumulating snow.

[Chambana]

your telling me.... I'm right on the edge of that band too.... i'd be really pissed if Champaign Urbana or even Tuscola got 4-6" and here in Charleston you get 1-2! it really looks like a big long band of LES

Hey now don't give chambana bad luck for this system;). Today was a torch day, I believe the temps maxed around 54-56 degrees, next week is looking mighty chilly....and snowy?

[jhamps10]

Hey now don't give chambana bad luck for this system;). Today was a torch day, I believe the temps maxed around 54-56 degrees, next week is looking mighty chilly....and snowy?

haha, no disrespect against chambana, yes today was a very lovely day for sure, looks like the shoe drops monday though even if we don't get snow from this...

[Hoosier]

00z NAM may try to tick north.  Downstream ridging looks a little more robust compared to 12z.

[jhamps10]

00z NAM may try to tick north. Downstream ridging looks a little more robust compared to 12z.

looks about the same to me Hoosier... it's not much north if any

EDIT: Does look like more moisture compared to the 12z on the NAM though at 36..

[Hoosier]

Ugh, low level temps are a disaster around here on this run.

[Hoosier]

Puzzling why the NAM has so much boundary layer warmth around here on this run. Nothing has really changed fundamentally.

[Chicago WX]

Ugh, low level temps are a disaster around here on this run.

Reverse gradient...WL wins this time.

[jhamps10]

Puzzling why the NAM has so much boundary layer warmth around here on this run. Nothing has really changed fundamentally.

yeah i'm scratching my head on that one too... only thing that changed to me, is it's bringing up more moisture than anything

[Stevo6899]

UMM lock in the NAM please!

[Powerball]

00z NAM is actually even wetter. Somewhat faster with everything too.

Detroit's a wild card again though. SE of Detroit looks to be rain through majority of the event. Northern and western suburbs look good though (mostly/all snow).

On the NAM verbatim it's still probably a mix/rain, but I have my doubts with the stiff NE wind and temps at/below 0*C around 925mb and 850mb for most of the event.

Anyway, NW suburbs are looking good.

[Hoosier]

Reverse gradient...WL wins this time.

Airmass locally is more marginal than the one for the cutoff low which is cause for some concern but I think we'd take our chances with this general outcome and hope that precip rates can come through.

[jhamps10]

Airmass locally is more marginal than the one for the cutoff low which is cause for some concern but I think we'd take our chances with this general outcome and hope that precip rates can come through.

ya that's the best shot IMO

and our possible third wave looks to be setting up nicely at 60 as well...

[Chicago WX]

Airmass locally is more marginal than the one for the cutoff low which is cause for some concern but I think we'd take our chances with this general outcome and hope that precip rates can come through.

No question the rates look "good enough"...but there's certainly some ugliness with the temp profile. Looks like 90% cold rain via the NAM.

[kab2791]

seems a little off too me, like the gradient over Metro Detroit.

[Chicago WX]

seems a little off too me, like the gradient over Metro Detroit.

Well that would be a kick in the nuts with that gap in the snow field.

[Central Illinois]

Well that would be a kick in the nuts with that gap in the snow field.

No kidding

[Hoosier]

Well that would be a kick in the nuts with that gap in the snow field.

The question is why is that gap there on this run and not the previous one? NAM has warmer temps on this run in the lowest 50 mb for some reason.

[Chicago WX]

The question is why is that gap there on this run and not the previous one? NAM has warmer temps on this run in the lowest 50 mb for some reason.

No idea. I'm trying to figure why it wants to "bow" the 0C 850 line (and subsequent lower levels) to the west/northwest in Indiana and east central IL...versus what happens in STL and DTW. Almost like it has some negative daytime reaction, though SE MI doesn't fit that idea I guess.

[KokomoWX]

This is a cruel trick by the NAM.

[Chicago WX]

This is a cruel trick by the NAM.

That's a keeper. Only if I want to get "winter depressed" that is.