2014-15 Winter Thread (Northern Hemisphere) (parallel, snow, Chicago, days)

[Shalop]

Powerful cold front making its way down into the northwest US.
Meanwhile unseasonably hot air making its way up into the south central & eastern US:

[Summerwhale]

I'm watching this weather station to see the front come through.
Custer, South Dakota (57730) Conditions & Forecast | Weather Underground

[Cambium]

Lets count how many times the word Polar is said... LOL

NWS NY NY

NATIONAL WEATHER SERVICE NEW YORK NY
115 PM EST SAT NOV 29 2014

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
INCREASING WARM AIR AND MOISTURE ADVECTION WITH THE APPROACHING WARM FRONT WILL HAVE TO MONITOR THIS FOR POTENTIAL ISSUANCE OF A FREEZING RAIN ADVY LATE TONIGHT INTO SUNDAY MORNING.

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
COLD FRONT WILL BE WELL TO THE SOUTH BY MON EVENING...WITH CAA ON GUSTY NW WINDS IN ITS WAKE. WITH ARCTIC HIGH PRESSURE BUILDING FROM THE NORTH IN ITS WAKE...EXPECT DRY CONDS MON NIGHT...BUT AN UPPER JET STREAK AND MID LEVEL SHORTWAVE MOVING ACROSS SHOULD MAINTAIN POST-FRONTAL CLOUDINESS UNTIL TUE MORNING. TEMPS SHOULD FALL SEVERAL DEGREES BELOW NORMAL BY TUES MORNING.

MODERATING POLAR HIGH BUILDS IN TUESDAY...WITH DRY BUT UNSEASONABLY COLD CONDITIONS. TEMPS WILL LIKELY RUN 10 DEGREES BELOW NORMAL...WITH HIGH GENERALLY IN THE 30S.

UNCERTAINTY IN THE FORECAST INCREASES FOR THE MID TO LATE WEEK AS MODELS DIFFER IN THE INTERACTION OF SHORTWAVE ENERGY ROTATING AROUND A CLOSED POLAR LOW NW OF HUDSON BAY AND ITS INTERACTION WITH NORTHERN STREAM ENERGY. THE 28/12Z CMC/ECMWF AND ASSOCIATED ENSEMBLES WERE AGGRESSIVE WITH THIS INTERACTION...PIVOTING A PHASED AND STRONG SHORTWAVE THROUGH THE NORTHEAST WED NIGHT. THE 28/12Z GFS WAS TAME WITH THIS INTERACTIONS AND SIGNALING A PRACTICALLY FLAT UPPER FLOW...WHILE THE 28/12Z GEFS DEPICTED A MORE AMPLIFIED SHORTWAVE PASSAGE. HAVE LEANED TOWARD THE MORE AMPLIFIED FLOW AS DEPICTED BY THE ENSEMBLE MEANS. IN TERMS OF SENSIBLE WEATHER...A RETURN FLOW TUE NIGHT IN WAKE OF EXITING POLAR HIGH AND APPROACHING SHORTWAVE AND ASSOCIATED FRONTAL SYSTEM...SHOULD SPELL AN INCREASING CHANCE FOR PRECIP TUES NIGHT INTO WED. THERMAL PROFILES SUPPORT WINTRY PRECIP TO START TUE NIGHT...THEN GRADUALLY CHANGING TO RAIN FROM S TO N ON WED. COLD AIR DAMMING COULD MAKE FREEZING RAIN STUBBORN ACROSS INTERIOR TRI-STATE ON WED. THIS SYSTEM SHOULD EXIT WED NIGHT AS THE SHORTWAVE AXIS PIVOTS THROUGH...WITH ANOTHER GLANCING SHOT OF CAA IN ITS WAKE.

MODERATED POLAR HIGH PRESSURE WILL LIKELY BUILD IN ON THU...WITH DRY AND BELOW SEASONABLE TEMPS. THEN MODELS WERE IN GOOD AGREEMENT WITH A PAC SHORTWAVE AND ASSOCIATED QUICK MOVING LOW PRESSURE APPROACHING LATE WEEK...BUT TIMING INTO REGION DIFFERS FROM THU INTO FRI BASED ON ABOVE MENTIONED DIFFERENCES WITH THE PRIOR NORTHERN STREAM SHORTWAVE. HAVING FAVORED MORE AMPLIFIED AND SLOWER PATTERN...

[Cambium]

Europe will need a fundamental change in the entire atmosphere to get a hard cold winter. I said a 2nd half winter for them weeks ago but I don't know now..

Once again I glance at the mid level temps and sure enough... which continent are the 2 Vortex's leaning towards?

And if you look back at my previous image from weeks ago there were no "aqua blues" in the northern Hemisphere.

Naturally the air is getting colder and building but interesting to see it in Canada already.. Anything below -15C at this level is impressive type cold right now in Canada and northern tier U.S.

You don't change the upper levels fast (it takes several weeks or months)

so this cold air will curl and pinwheel in and out of the U.S next few weeks. First its the northern Plains/NW, then Mid West, then finally into the East. The further south the vortex goes the more brutal the weather will get at the surface in the U.S.

[chicagogeorge]

Originally Posted by Cambium

GFS12z goes Vortex BOOM. Sitting that low? Yikes.

That would be nice.


Cold first couple of days of December. Check out the lows Monday night. Down to 5F in the western and northwest suburbs (15 in the city by the lakeshore)




You are right however, After this week's cold shot, I think we are an additional 8-10 days out before serious cold comes back into the US. Looks like a zonal pattern if not an eastern ridge set up in the 6-10 day range.







So moral of the story, cold lovers will need to wait 2 weeks into December


Andrew blogged about it.... Polar Vortex splitting in mid December





http://theweathercentre.blogspot.com...ng-arctic.html

[chicagogeorge]

Milder temperatures expected early this winter season | Chicago Weather Center: Skilling's Forecast and Chicago Severe Weather Alerts

[chicagogeorge]

First day of winter will feel wintery in the Central US





Could this be?




Lot's of buzz about an Arctic invasion in the middle of December. Maybe not just for North America...


CFSv2 still forecasting blow torch for December....




Bastardi forecasting colder than normal for December





Remember this is what CFSv2 put out for November back in late October



And this is reality top 10 coldest Novembers over the last 50+ years for sure




Obviously I'm going with JB's forecast

[chicagogeorge]

6-10 day GFS ensemble




6-10 day GFS operational looks pretty similar



Big difference in the 11-15 day


Ensemble




Operational

[Hiromant]

Since there's no winter photo thread I'll just leave these here.

Beautiful day today, a crisp and clear -11°C. I took some shots at a friend's place. At 3 PM the sun was already on its way to setting.

[chicagogeorge]