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February 28-March 3rd Winter Storm


Chicago Storm

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System looks impressive but is slow-moving and most of the energy will break away and move ahead into the southern Rockies, where it will likely do approximately what the models already think it will do. Just my opinion anyway, the pattern looks flat and energy will tend to be largely confined to southern stream. For anywhere north of central IL-IN-n OH to get much snow, there would have to be lake enhancement or phasing of some northern stream energy. This could happen for Chicago, Lake Michigan is not entirely frozen and weak energy is indicated. So my punt is for 5-8 inch snowfalls in s IL-IN and s.c OH, 1-3 inches further north but some dry spots could mix in.

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dvn

 

 

A VERY CHALLENGING FORECAST IS IN STORE FOR SATURDAY INTO
SUNDAY...AS MODELS ARE AN EXTREME EXAMPLE OF DISCONTINUITY. EVEN AT
THIS LATE STAGE...THERE ARE MODELS FORECASTING EXPLICITLY HEAVY SNOW
AMOUNTS UP THROUGH HIGHWAY 30...WHILE OTHERS PRODUCING LESS THAN 4
INCHES EVEN IN THE FAR SOUTH. THIS IS TROUBLING. IN THIS
INSTANCE...THE ECMWF NOW IS A VERY DRY OUTLIER...AS IS THE
GFS...WHILE THE NAM...UKMET...AND GEM REMAIN QUITE WET...WITH 0.40
TO 0.60 LIQUID OVER MUCH OF THE SOUTHERN 2/3RDS OF THE CWA. RATIOS
LOOK TO BE IN THE 15 TO 17:1 RANGE...AS WIND SHOULD PREVENT ANY 20:1
FROM VERIFYING. WITH SNOW ARRIVING ON FGEN FORCING TOWARD 18Z IN THE
NORTHWEST...AND WITH THAT BAND SLOWLY SINKING SOUTH THROUGH THE
NIGHT...IT SHOULD NOT MODERATELY SNOW IN ANY LOCATION FOR MORE THAN 4
HOURS...WITH LIGHT SNOW POSSIBLE AFTER IT PASSES. THIS SHOULD KEEP
AMOUNTS FROM GETTING TOO HIGH IN OUR CWA. STILL...IT APPEARS THAT
OUR SOUTH COULD SEE LONG ENOUGH FORCING FOR A BROAD 5 TO 7 INCHES
OVER A 18 TO 24 HOUR PERIOD. GIVEN THE LONG DURATION...THIS STILL
SEEMS TO FIT WITH AN ADVISORY VS WARNING. I WILL ALSO GO ADVISORY
FOR AREAS UP THROUGH HIGHWAY 30 AS WELL...GIVEN POTENTIAL FOR 3 TO 4
INCHES DURING THE AFTERNOON AND EVENING HOURS SATURDAY. FOR OUR
SOUTH...I WILL BEGIN THE ADVISORY SATURDAY AT 6 PM...NORTH AT NOON.
IF THIS HAD BEEN A CLOSED LOW SITUATION WITH ALL OTHER VARIABLE THE
SAME...I WOULD HAVE EASILY SEEN A SOLID WARNING EVENT...BUT WITH THE
WAVE SO FAR SOUTH...IT FEEL AN ADVISORY IS A BEST FIT PRODUCT AT
THIS TIME.
 

 

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LOT going 2-8 inches across the area:

 

 

 

AS FOR HEADLINES...I HAVE CHOSEN TO HOLD OFF ON THE ISSUANCE OF ANY
HEADLINES. IT APPEARS THAT MOST IF NOT ALL OF THE AREA WILL BE AN
ADVISORY TYPE EVENT WITH 2 TO 5 INCHES ACROSS THE NORTHERN HALF OF
THE AREA...TO 4 TO 8 INCHES FAR SOUTH. ALTHOUGH SNOW AMOUNTS MAY
EXCEED 6 INCHES ACROSS MY SOUTHERN COUNTIES SATURDAY NIGHT THROUGH
SUNDAY EVENING...THE EVENT LOOKS TO OCCUR OVER A FAIRLY LONG
DURATION...MORE THAN 12 HOURS...THUS WE MAY BE ABLE TO GET BY IN
THESE AREAS AS WELL WITH AN ADVISORY. THE MAIN REASON FOR HOLDING
OFF...IS JUST TO MAKE SURE THAT THINGS DONT CHANGE
SIGNIFICANTLY...REQUIRING THE ISSUANCE OF A WARNING OVER AN ADVISORY
FOR PORTIONS OF THE AREA.
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yea this kind of setup is hell on earth for models. multiple waves along a front with surging cold air from the north from huge high and surging intense waa from the south. those two will be duking out and I think models are struggling with the placement of the front. I remember the early Jan event that frontogenic band ended up moving very slowly due to a shortwave that rode up the front and that stalled the movement of the cold air. a lot of little details could change at the last second. hell our southern stream system hasn't even been sampled yet. wont have a full sample till 0z runs tmrw night. the natural baroclinic zone actually sits farther north where some snowpack remains so im not sure if models captured this correctly. a lot of challenging things that could have big impact on the system. also models were trying to close off a low at 500mb I think at one time. that would greatly change this overall setup. it is funny how euro before was the southern outlier and gfs was so north and now they have switched. the consistency in the models is a joke this winter. so much wobbling all the way up till the event begins. so my forecast is 1-12" of snow for here. LOL. jk. I think 5-7in is a safe bet for me. Im sitting in Chillicothe, IL just north of Peoria. im not sold on any one solution yet. things can still change. high ratios can throw in some surprises to

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I find this very interesting. Looking at the current 18z run of GFS I see that it has initialized the HP too far south than where it currently is. looking at the images I posted you can see 18z gfs has the 1036mb contour in far northern Montana however looking at the most recent surface map the 1036mb contour is up in central Canada. could be one reason why models have been shifting higher QPF and snow totals further south. not saying this will hold tomorrow because the arctic air could surge more but currently it doesn't have a good handle on it. like thundersnow just stated we really wont have a good idea till the runs tomorrow. we wont even see a full sampling till 0z runs tomorrow

post-6173-0-98791200-1393631339_thumb.pn

post-6173-0-43716500-1393631349_thumb.gi

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Interesting thinking from IWX AFD this afternoon

GREATEST CONFIDENCE LIES W/SAT NIGHT EARLY SUNPD AND HAVE BUMPED POPS FOR BOTH PDS. HWVR DETAIL UNCERTAINTYREMAINS ESP W/POTENTIAL MESOBANDING INVOF ARCTIC FNT SAT NIGHT. FORNOW WENT ALONG W/RAW CONSENSUS QPF WHICH GENERALLY FOLLOWED PRIORGRIDS SANS FAR SOUTH WHERE GENERAL SOLUTION CONSENSUS IS WETTER SUNAFTN/SUN NIGHT. THUS TO GIVE SOME WIGGLE ROOM ALG PROJECTED 8 INCHSNOW CONTOUR...WILL ADD A FEW COUNTIES NORTH OF EXISTING WATCH AS AHEDGE.
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Well this is interesting for sure. 18z GFS did prog pressures across nrn MT at 0z tonight around 1036mb and looking at obs now, they are between 1028mb-1030mb

yea maybe just a slower moving high/arctic air mass which would def help our cases in seeing more snow. I totally sound like a wishcaster now. lol

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Well this is interesting for sure. 18z GFS did prog pressures across nrn MT at 0z tonight around 1036mb and looking at obs now, they are between 1028mb-1030mb

More evidence of this discrepancy:

 

Williston ND

Actual pressure at 6PM CST (0z tonight):  1029.4 mb

18z GFS forecasted pressure (0z tonight):  1032.4 mb

 

:weenie:

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yea this kind of setup is hell on earth for models. multiple waves along a front with surging cold air from the north from huge high and surging intense waa from the south. those two will be duking out and I think models are struggling with the placement of the front. I remember the early Jan event that frontogenic band ended up moving very slowly due to a shortwave that rode up the front and that stalled the movement of the cold air. a lot of little details could change at the last second. hell our southern stream system hasn't even been sampled yet. wont have a full sample till 0z runs tmrw night. the natural baroclinic zone actually sits farther north where some snowpack remains so im not sure if models captured this correctly. a lot of challenging things that could have big impact on the system. also models were trying to close off a low at 500mb I think at one time. that would greatly change this overall setup. it is funny how euro before was the southern outlier and gfs was so north and now they have switched. the consistency in the models is a joke this winter. so much wobbling all the way up till the event begins. so my forecast is 1-12" of snow for here. LOL. jk. I think 5-7in is a safe bet for me. Im sitting in Chillicothe, IL just north of Peoria. im not sold on any one solution yet. things can still change. high ratios can throw in some surprises to

 

usually when I read this from a poster inside 72 hours of an event I'm thinking :weenie: .   But I have to admit there is virtually no consensus right now and models are still flip flopping amongst themselves.   I mentioned in the Ohio thread that the 12z runs were comical for Ohio.   The ggem shows ZERO accumulations south of i70, while the euro has the axis of heaviest in southern OH.  

Safe to say, the whole idea of this needing better sampling is spot on this time.

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