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January 12-14 Potential Winter Weather Event


Hoosier

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Chew on this; obviously it's nowcast time, but the Euro had been consistent for a few runs, then shifted SE and dry. Meanwhile, the GFS ensembles have gotten wetter and wetter for awhile; now several of them at the 18z have .25-.50" of liquid in SE Wisconsin. The models love to flip flop with each other.

I think you'll do ok with precip up that way. The short term guidance looks pretty good.

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creeper ice storm in the making for chicago?

I've been wondering if the ice might overperform. Heavy precip rates could throw the ptype off or make accretion a little more difficult so it's a tough call. Of course your microclimate will probably spare you and keep you at 32.3 during the event. :P

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I've been wondering if the ice might overperform. Heavy precip rates could throw the ptype off or make accretion a little more difficult so it's a tough call. Of course your microclimate will probably spare you and keep you at 32.3 during the event. :P

 

 

still 37 here but starting to drop off

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Looking at RAP fcst soundings, ARR gets very close to changing over to all snow or actually changes over near 6z. There is about a 100-150mb isothermal layer right at 0 deg C so better precip rates would favor snow in that situation

That's what I'm hoping happens for more of the Chi metro, an ice storm would be a terrible thing with the extended period of at least seasonable cold on the way.

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MKX just issued a WWA for the SE corner of the CWA.

 

 

 

WIZ065-066-070>072-131200-/O.NEW.KMKX.WW.Y.0001.130113T0300Z-130113T1200Z/WAUKESHA-MILWAUKEE-WALWORTH-RACINE-KENOSHA-INCLUDING THE CITIES OF...WAUKESHA...BROOKFIELD...MILWAUKEE...ELKHORN...LAKE GENEVA...RACINE...KENOSHA616 PM CST SAT JAN 12 2013...WINTER WEATHER ADVISORY IN EFFECT FROM 9 PM THIS EVENING TO6 AM CST SUNDAY...THE NATIONAL WEATHER SERVICE IN MILWAUKEE/SULLIVAN HAS ISSUED AWINTER WEATHER ADVISORY FOR SNOW AND SLEET ACCUMULATION...WHICH ISIN EFFECT FROM 9 PM THIS EVENING TO 6 AM CST SUNDAY.* TIMING...LIGHT TO MODERATE SNOW AND SLEET IS EXPECTED MAINLY  FROM 9 PM THROUGH 3 AM...WITH LIGHT SNOW EXPECTED FROM 3 AM TO 6  AM.* SNOW ACCUMULATIONS...ONE AND A HALF TO THREE INCHES. SLEET  ACCUMULATIONS ONE HALF TO ONE INCH.* IMPACTS...HAZARDOUS TRAVEL CONDITIONS ARE EXPECTED TO DEVELOP.  SNOW COVERED AND SLIPPERY ROADS ARE ANTICIPATED AS WELL AS  VISIBILITIES AS LOW AS A HALF MILE.
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Amazing low-level baroclinic zone with this.  Temps pushing 70 over the southern tip of IL, while northwest IL has temps in the mid 20s.  Dews range from the mid 60s to the teens from south to northwest IL. 

 

No precip yet here, but it should be all snow.  Temp down to 26.

temp.IL-large.png

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post-5865-0-59603400-1358037238_thumb.gi

 

MESOSCALE DISCUSSION 0017
   NWS STORM PREDICTION CENTER NORMAN OK
   0617 PM CST SAT JAN 12 2013
  
   AREAS AFFECTED...NWRN INDIANA...NRN/CNTRL/W-CNTRL IL...PARTS OF
   E-CNTRL/SERN/S-CNTRL MO
  
   CONCERNING...WINTER MIXED PRECIPITATION
  
   VALID 130017Z - 130615Z
  
   SUMMARY...WINTER MIXED PRECIPITATION WILL INCREASE IN COVERAGE AND
   INTENSITY THIS EVENING. THIS WILL INCLUDE THE THREAT FOR FREEZING
   RAIN WITH RATES OF 0.05 TO 0.10 IN/HR...WITH LOCALLY HIGHER RATES
   ALSO POSSIBLE. FREEZING RAIN WILL BECOME INCREASINGLY LIKELY IN THE
   CHICAGO AND ST. LOUIS AREAS AFTER 04Z.
  
   DISCUSSION...A LARGE SHIELD OF CONVECTIVE-DEBRIS-RELATED
   PRECIPITATION WITHIN A WARM CONVEYOR BELT WILL CONTINUE TO
   OVERSPREAD THE AREA THIS EVENING. THIS ACTIVITY SHOULD PERSIST THE
   OVERNIGHT HOURS AS ELEVATED WARM ADVECTION OCCURS THROUGH THE
   NIGHT...WITH A TENDENCY FOR HIGHER PRECIPITATION RATES TO SHIFT NEWD
   IN TANDEM WITH THE STRONGER ASCENT.
  
   AS SUBFREEZING SFC-LAYER TEMPERATURES UNDERCUT THE ELEVATED WARM
   ADVECTION...THE LEADING EDGE OF WINTER MIXED PRECIPITATION WILL
   ADVANCE ESEWD ACROSS THE REGION. IMMEDIATELY BEHIND THIS LEADING
   EDGE...A 40-70-MILE WIDE CORRIDOR OF POTENTIAL FREEZING RAIN WILL BE
   ASSOCIATED WITH LIQUID-EQUIVALENT RATES OF 0.05-0.10 IN/HR. LOCALLY
   HIGHER RATES MAY OCCUR OWING TO A MODEST CONVECTIVE ENHANCEMENT
   ASSOCIATED WITH NARROW ELEVATED CAPE PROFILES. THE FREEZING-RAIN
   CORRIDOR WILL LIKELY MOVE INTO NWRN INDIANA BY 07Z.
  
   SENSIBLE HEAT FLUXES ASSOCIATED WITH PREVIOUSLY FALLEN LIQUID MAY
   INITIALLY DELAY THE ONSET OF ICING ON MANY SURFACES...ASIDE FROM
   ELEVATED/METAL SURFACES. REGARDLESS...OBSERVATIONS UPSTREAM ACROSS
   CNTRL MO INTO NERN OK INDICATE PERSISTENT FREEZING RAIN
   OCCURRING...AND SFC ICING WILL BE LIKELY.
  
   TO THE WNW OF THE FREEZING-RAIN CORRIDOR...DEEPER COLD AIR WILL
   LIMIT/PRECLUDE MELTING OF DESCENDING HYDROMETERS AND SUPPORT SLEET
   AND LIGHT TO OCCASIONALLY MODERATE SNOW. REMAINING PRECIPITATION
   WILL PROGRESSIVELY TRANSITION TO SLEET/SNOW FROM WNW TO ESE DURING
   THE OVERNIGHT HOURS...ESPECIALLY ACROSS NRN IL. PRECIPITATION RATES
   ARE EXPECTED TO DECREASE AREA-WIDE BY 09Z AS STRONGER FORCING FOR
   ASCENT SHIFTS NE OF THE AREA.
  
   PLEASE REFERENCE MCD 16 FOR ADDITIONAL DETAILS REGARDING ONGOING
   WINTER MIXED PRECIPITATION ACROSS NERN OK...SERN KS...CNTRL MO...AND
   W-CNTRL IL.
  
   ..COHEN.. 01/13/2013
 

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Looks like the dry air may end up eating up a lot of the qpf for the QC.  No precip reports at all in Iowa and about the northwest 1/3 of MO.  DVN radar shows precip struggling to reach the surface in the cold air.  The NE/SW oriented frontal zone and associated heavy precip may end up screwing the pooch for this area.  Glad I low-balled with my 1" call.  Could bust high even on that if this dry air doesn't saturate in a big hurry.

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Seems like this is a good time to post this. It's a paper that shows urban modification of freezing rain frequency (and also being near a large body of water in the case of Chicago) for various US cities.

http://journals.ametsoc.org/doi/pdf/10.1175/1520-0450%282003%29042%3C0863%3AUMOFE%3E2.0.CO%3B2

I meant to post this graphic earlier from the U of I

http://www.isws.illinois.edu/atmos/statecli/ice/ice.htm

post-3774-0-64005300-1358037575_thumb.pn

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Looks like the dry air may end up eating up a lot of the qpf for the QC.  No precip reports at all in Iowa and about the northwest 1/3 of MO.  DVN radar shows precip struggling to reach the surface in the cold air.  The NE/SW oriented frontal zone and associated heavy precip may end up screwing the pooch for this area.  Glad I low-balled with my 1" call.  Could bust high even on that if this dry air doesn't saturate in a big hurry.

 

wonder if thats why the euro was so dry for us @ 12z.   Do models figure in dry air- virga?

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