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Tuesday, March 5, 2013

WX UNIT DISCUSSION 03/05/2013 1030Z

UNUSUALLY DISORGANIZED WEATHER AND DIFFICULT FORECAST NOW BECOMING BETTER REALIZED:

THE COMPUTER MODELS ARE NOT AIDING FORECASTERS

WX UNIT DISCUSSION FOR WI AND ADJOINING STATES:

This is one of those times you have to chuck the models no matter how wonderful you may think they are and quite honestly I'm not going to even peek at one.  In fact when I look at data I look at the basics:
  • WINDS ALOFT
  • SURFACE DATA
  • RADAR
  • TRENDS
  • SATELLITE TRENDS
  • NATIONAL COMPOSITE TRENDS
  • RUC ANALYSIS (WELL I'M FORCED TO DO THIS ONE)
Actually I'm kind of a dinosaur when it comes to this stuff because I think the name RUC was changed to RAP but that doesn't matter right now and I still believe rain showers and snow showers should be written as RW and SW instead of the NEW WORLD ORDER METAR FORMATS WHICH I CANNOT STAND.  Thank you very much.

This complicated weather system that has been changing it's shape over the last 24 hours is making a slower progression eastward and has proven to be a forecast pest so far and also proves the importance of really knowing your weather. As the saying goes, "Weathermen are the only ones that can be wrong and still keep their job."  Well I wasn't even wrong and wasn't able to keep mine---but that's another story.

This shortwave has very impressively amplified now across the nation's mid section and is funneling in a very notable cold air mass behind it with gusty winds driving south across the Great Plains deep into Texas.   A strong surface cold front runs from eastern Texas through the ARKLATEX region northeastward into a strengthening area low pressure area now taking shape just west of Memphis.  From this low a well defined inverted trough has formed north westward into eastern Iowa and then further northwestward into the eastern Dakotas where another are of low pressure is now morphing into that inverted trough.  

This system is tapping the Gulf moisture flow now and it looks like GAME ON for a MAJOR WINTER STORM EVENT that is likely to produce some incredible amounts of snow and SEVERE WINTER CONDITIONS including all modes of severe weather from winter storm and blizzard conditions to freezing rain, sleet, rain, severe thunderstorms and even some possible isolated tornadoes.  This is also creating setup for major flooding given more upstream storms are expected by mid March with a market warming trend and above normal precipitation which could induce major flooding in a week or so.   Any warming trend coupled with large amounts of rain on top of what this storm will lay down for snow accumulation is certain to cause some flooding concerns.  

For now this remains a difficult forecast to pinpoint the exact location of heavy snow and mark the areas where the usual 1-3, 4-6, 6-10, or 8-14 inch snowfalls will occur.  Ongoing area of light snow with some scattered heavier snow bands that has persisted over the last 18 hours in the upper Mississippi valley region and upper Midwest continues to persist in an area of forcing just east of the inverted trough across much of Minnesota, eastern Iowa, northeastern Missouri and western Illinois now moving into extreme western Wisconsin.  This area prompted the onset of Winter Storm Watches and Warnings on Sunday and produced some impressive snow amounts across North Dakota with areas receiving on the order of generally 6 to 15 inches of snow depending on location.  Across Minnesota and Iowa this has been generally a 2 to 6 inch accumulations.  

This storm system concerns me since it has not been as progressive as I initially expected it to be.  For starters it looked like an Alberta Clipper type system would merge into sort of a western type system but downstream and off the east coast an UPPER ATMOSPHERIC BLOCKING PATTERN with a retrograding cyclone of the coast of New Brunswick seems to have been holding the progressive flow back a bit.  The southern stream has become well pronounced now at H500 and above and is rifling a strong jet stream west to east across the south half of the continental United States.   This has cause a real brain teaser of a forecast pest as it had the makings of each of the four main types of winter low pressure systems that would usually affect this region.  They are:

1)  The Alberta Clipper
2)  The western type low
3)  The Panhandle Hook
4)  The Lower Mississippi Type low

This system initially gave a blend of everything but for now we will get on with the discussion and expected track of this storm below:

KEEP IN MIND THERE IS ANOTHER STORM UPSTREAM OFF THE WEST COAST THAT NEEDS WATCHING FOR LATER THIS WEEK AND NEXT.

I'M GOING TO ABBREVIATE THE REST OF THIS TO SAVE TIME:

STRG WELL AMPLIFIED SWAVE NOW IN CENTRAL US AS YESTERDAY'S NRN STREAM NOW MERGED WITH SRN BRANCH UPR FLOW.  SFC LOW J W OF MEM AROUND 1007MB AND WATCHING WITH GREAT INTEREST TO SEE IF THIS WILL FALL BELOW 1000MB DURING NEXT 6 HOURS.  STRGR JET MAXES ARE IN SRN TX AND ALSO THE WRN HIGH PLAINS DIVING S ALG WRN PERIPHRY OF TROUGH.  

LOOKS LIKE A LARGE SCALE SNOWFALL WILL DUMP ALONG AND N OF STORM TRACK AS MEM LOW MOVES SLOLY NEWD INTO OH VLY RGN AND THEN PROBABLY EWWD INTO THE DELMARVA.  HPC TRACK SHOWN BELOW LOOKS ACCURATE ENOUGH GIVEN CURRENT DYNAMICS:
CLICK TO ENLARGE
NEED TO MENTION IMPRESSIVE INVERTED TROUGH AND NOTABLE MOISTURE FETCH WHICH WILL WRAP AROUND THE NRN PERIPHRY OF STRM SYS TO CAUSE ADVISORY CRITERIA SNW ALG AND N OF HVY SNOW DEFORMATION ZONE LIKELY TO CAUSE ADDTL SHORT TERM FCST  ADJUSTMENTS AS THE SYSTM UNFOLDS ACROSS ALL OF WI AND INTO LOWER MICH.

LOOKS LIKE THE STORM SYS IS GOING TO RAKE SRN WI, NRN IL, SRN LK MICH, IN, OH, SRN LWR MICH, EWWRD WITH IMPRESSIVE HVY SNOW ON THE ORDER OF 6-12 INCHES MAKING TRAVEL HAZARDOUS.  IT MAY MOVE SLOW WHICH COULD CAUSE SOME AMTS TO BE AMENDED TO HIGHER ACCUMS AS THIS SYTEM MOVES E ESPECIALLY IN THE HIGHER APPALACH MTN AREAS AND EWWD.  KEEP UP WITH THE FORECAST.

UPSTREAM IS ANOTHER MAJOR CONCERN WITH NEXT SYS MVG ONSHORE ALG U.S. WEST COAST.  WILL DISCUSS THIS FURTHER IN NEXT DISCUSSION.

PRESENT THOUGHT IS HVST SNOW IN WI HERE WILL REMAIN SO OF A LINE FROM MSN TO MKE BUT DOES NOT DIMINISH THE POTENTIAL OF SOME ISOLD HIGHER AMTS N OF THIS LINE.  I'LL CALL 6-10 SO OF A LNR MSN MKE LINE and 4-6 INCHES N OF THIS LINE.   RFD TO ORD AND EVEN ENW AND RAC COULD GET SOME 12+ INCHES.  MIGHT HAVE TO ADJUST THE LINE FROM SAY MSN TO UNU TO SBM IF LOW TRACKS FURTHER N.  
ALL INTERESTS SHOULD KEEP UP WITH THE FORECAST ON THIS ONE AND PLAN TRAVEL SAFETY ACCORDINGLY.  

FOR OFFICIAL INFORMATION SEE WWW.WEATHER.GOV 

STORM CHASER CASPER WX UNIT




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