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January 12-14 Potential Winter Weather Event


Hoosier

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

 

Not sure.  Usually it's not a long term problem, more of a brief issue at the onset of a system.  The precip echoes show no sign of backing in more from a southerly direction, just quickly scooting northeast.  This is a sign that there's really not any moisture wrapping back into the cold sector.  I think the virga filled deform area is all from forcing alone.  The northwesterly low-level winds only add to it, with the slow advection of drier air. 

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Mr Izzi

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL

656 PM CST SAT JAN 12 2013

MESOSCALE DISCUSSION

654 PM CST

CLOSELY MONITORING OBSERVATIONAL TRENDS THIS EVENING FOR POTENTIAL OF FAIRLY SUBSTANTIAL FREEZING RAIN/SLEET EVENT FOR PORTIONS OF THE CWA. EVENING SOUNDINGS SHOWED A STRENGTHENING 300MB JET STREAK OVER THE UPPER MS VALLEY WITH 300MB WINDS NEARLY 160KT AT MPX THIS EVENING. REGIONAL RADAR IMAGERY SHOWS AN EXPANDING/INTENSIFYING AREA OF PRECIPITATION OVER MO INTO WESTERN ILLINOIS EARLY THIS EVENING IN THE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET AND CO-LOCATED WITH STRENGTHENING BAND OF 800-700MB FRONTOGENESIS AS DEPICTED BY THE RAP/SPC MESOANALYSIS. VERTICAL CROSS SECTIONS OF RAP MODEL GUIDANCE CUTTING THROUGH THIS BAND SHOW VERY IMPRESSIVE UPWARD VERTICAL VELOCITIES WITH STRONGLY NEGATIVE SATURATED EPV VALUES AND NEGATIVE THETA-E LAPSE RATES...BOTH INDICATE OF POTENTIAL INSTABILITY THAT COULD RESULT IN ENHANCED PRECIPITATION RATES AND POSSIBLY EVEN A COUPLE ROGUE LIGHTNING STRIKES AS THIS BAND INTENSIFIES OVER THE CWA DURING THE MID-LATE EVENING HOURS.

P-TYPE IS EXTRAORDINARILY TRICKY...EXAMINING FORECAST SOUNDINGS FROM THE U OF I ENSEMBLE WRF MEMBERS...MOST OF THEM SHOW A SUBSTANTIAL WARM LAYER OVER CHICAGO DURING MOST OF THE PRECIP EVENT WITH UP TO 100MB DEEP WARM LAYER WITH MAX TEMPS OF AT LEAST 3C IN THE WARM LAYER WHICH WOULD SUGGEST COMPLETE MELTING AND MAKE FREEZING RAIN THE MOST LIKELY PRECIP TYPE. OPERATIONAL MODELS ARE MUCH LESS PRONOUNCED WITH THE WARM BULGE AND WOULD FAVOR MORE SLEET. THE 00Z SOUNDING FROM ILX CERTAINLY SHOWED A DEEP WARM LAYER WITH WET BULB 0C WELL ABOVE FREEZING LENDING A BIT MORE CREDENCE TO THE HIGH-RES WRF SOLUTIONS WHICH SUGGEST THE POTENTIAL FOR MORE OF A FREEZING RAIN EVENT FOR A DECENT SIZED CORRIDOR OF THE CWA. POTENTIAL CERTAINLY EXISTS FOR SOME AREAS TO SEE ICE ACCUMULATIONS OF AT LEAST 0.25 INCHES...THOUGH THAT WILL BE HIGHLY DEPENDENT ON P-TYPE REMAINING MOSTLY FREEZING RAIN FOR A SUFFICIENT ENOUGH TIME AND NOT TRANSITIONING BACK FORTH BETWEEN SLEET.

PLAN FOR NOW IS TO CONTINUE CLOSELY MONITORING OBSERVATIONAL TRENDS AND LET WINTER WX ADVISORY RIDE...HOWEVER SHOULD IT BECOME APPARENT THAT A MORE PROLONGED PERIOD OF FREEZING RAIN MAY OCCUR THEN MAY NEED TO CONSIDER AN UPGRADE TO A WINTER STORM OR ICE STORM WARNING FOR SOME PORTIONS OF THE CWA. PRESENT INDICATIONS ARE THE MOST LIKELY CORRIDOR FOR POTENTIAL MORE SIGNIFICANT ICING PROBLEMS WOULD BE FROM CHICAGO SOUTHWEST ALONG THE I-55 CORRIDOR TOWARD PONTIAC.

HAVE MASSAGED AND SENT SOME UPDATED GRIDS TO HIT THE FREEZING RAIN POTENTIAL AND ICE ACCUM A BIT HARDER.

IZZI

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Not sure.  Usually it's not a long term problem, more of a brief issue at the onset of a system.  The precip echoes show no sign of backing in more from a southerly direction, just quickly scooting northeast.  This is a sign that there's really not any moisture wrapping back into the cold sector.  I think the virga filled deform area is all from forcing alone.  The northwesterly low-level winds only add to it, with the slow advection of drier air. 

 

 

Thanks much for the reply.  I'm kinna too buzzed up to make any type of coherent response..  any thoughts for up this way? :weenie:

 

Good luck down there!

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Thanks much for the reply.  I'm kinna too buzzed up to make any type of coherent response..  any thoughts for up this way? :weenie:

 

Good luck down there!

 

 

You're a little further southeast relative to the northwest fringe compared to me from what I can tell.  I think you're good for 1-2", with maybe a 3" if you guys can get lucky and get stuck under a narrow band for awhile on the northwest fringe. 

 

EDIT:  Rockford reporting a mix of sleet and snow.  Still nada here.  Except for some vigorous virga of course.  :tomato:

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