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December 20th-22nd Major Winter Storm Part II


andyhb

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LSE had this just come out:?

HAVE VIEWED STANDARDIZED ANOMALIES TO ASSESS HOW UNUSUAL THIS STORM

IS COMPARED TO HISTORICAL STORMS. A NUMBER OF PARAMETERS NOT

SURPRISINGLY ARE IN THE 2-3 STANDARD DEVIATION /SD/ FROM THE MEAN

INCLUDING SURFACE PRESSURE...PRECIPITABLE WATER AND THE WINDS

AT 850 MB /FROM 15Z THURSDAY ON/. THE 18.12Z NAM SOLUTION HAD A -3.5

SD FOR THE 850MB LOW CENTER OVER CHICAGO/LOWER MI BY NOON THURSDAY.

MORE IMPRESSIVE IS THE CHANGE IN THIS ANOMALY AS THE STORM MOVES BY

AND STRENGTHENS...WITH -2.5 SD IN NERN MO DEEPENING TO -3.5 SD BY

MICHIGAN IN 12 HOURS THURSDAY. THE BOTTOM LINE IS THIS IS AN

UNUSUALLY STRONG STORM AND WE MUST BE CAREFUL FOR MORE SIGNIFICANT

IMPACTS. LOW-LEVEL WIND DEVIATIONS ARE ALSO IN THE +2 TO 3 SD

RANGE MAKING A BLIZZARD CONDITION PART OF THE DISCUSSION.

THE 18.12Z NAM/GFS/ECMWF HAVE ALL TAKEN A SLIGHT STEP SOUTHEAST BUT

ALSO HAVE PORTRAYED A LARGER BROADER BAND OF DEFORMATION ON THE

NORTHWEST SIDE OF THE STORM. IN THE BIG PICTURE...THE SNOWFALL

TOTALS FROM THIS STORM ARE A BIT HIGHER THAN PREVIOUSLY FORECAST. NCEP

SREF POPULATIONS HAVE DRASTICALLY SHIFTED THE SNOW BAND

SOUTHEASTWARD SINCE THE MONDAY 17.15Z RUN WITH A NICE STEP EACH

MODEL RUN TOWARD THE CURRENT DETERMINISTIC MODEL RUNS. THIS HAS

LED TO MORE CONFIDENCE AS WELL. THEREFORE...HAVE DECIDED AND

COLLABORATED A WINTER STORM WARNING UPGRADE /FROM WATCH/ IN THE

HIGH PROBABILITY...MOST IMPACTED COUNTIES IN THE EAST/SOUTHEAST LA

CROSSE FORECAST AREAS. REALLY...THIS STORM HAS MANY INGREDIENTS

FOR A DANGEROUS WINTER STORM...IT IS NOT IF...BUT WHERE.

THE JET DYNAMICS ARE INTERESTING FOR THIS STORM WITH MUCH OF THE

AGEOSTROPHIC COMPONENT AND DIVERGENCE ALOFT COMING FROM THE

CURVATURE FROM THE DOWNSTREAM HIGHER AMPLITUDE RIDGE AND THE STORM

SHORTWAVE TROUGH ITSELF. THIS CURVATURE DIFFERENCE ONLY INCREASES

INTO THURSDAY WITH AMPLIFICATION OF THE RIDGE/TROUGH SYSTEM AND

NEGATIVE TILT TO THE SHORTWAVE TROUGH. THIS ENHANCES THE LOW-LEVEL

CYCLONE DEEPENING AND IT NEARLY BOMBS ON ITS WAY PAST US. THIS

ELICITS A STRONG WIND FIELD ON THE WEST FLANK OF THE LOW

CENTER...WITH THE MAXIMUM PRESSURE GRADIENT TRANSVERSING THE

SOUTHEAST HALF OF THE FORECAST AREA THURSDAY. THE MAX AREA BRUSHES

GRANT COUNTY BEFORE AFFECTING ALL OF THE MKX FORECAST AREA AND

SOUTHERN WI. BUT...THE LOW-LEVEL WIND FIELD IS STRONG WITH 25-30 MPH

AND GUSTS TO 40 MPH EXPECT THURSDAY IN NORTHEAST IOWA AND SOUTHWEST

WI. THIS AREA IS VERY CLOSE TO NEEDING A BLIZZARD WARNING.

CONFIDNECE IS A BIT LOWER THAT BOUNDARY LAYER LAPSE RATE WILL BE

STEEP ENOUGH IN THE SNOW TO EFFECTIVELY MIX THE HIGHER GUSTS TO

THE SURFACE TO CAUSE BLIZZARD. BUT THIS MAY HAPPEN AFTER THE SNOW

STOPS. WHILE SNOW TOTALS ARE LESS TO THE NORTHWEST /CHARLES CITY-

AUSTIN/...THERE IS CONCERN FOR THE OPEN COUNTRY AND WINDS OF 25-40

MPH. 4 INCHES OF SNOW AND THOSE WIND SPEEDS COULD CAUSE A

DANGEROUS IMPACT WHERE A WARNING IS MORE APPROPRIATE.

THUS...HAVE ADDED A TIER TO THE NORTHWEST ONTO THE WINTER STORM

WATCH TO RAISE AWARENESS OF WIND AND SNOW THREATS. WE HAVE DECIDED

TO ALSO UPGRADE TO A WARNING IN THE FAR SOUTHEAST-EAST WHERE

CONFIDENCE IN A DANGEROUS STORM IS HIGHEST. RIGHT NOW...WE WILL

CONTINUE TO MONITOR FOR ANY CHANGE IN THE STORM FOR AN UPGRADE TO

BLIZZARD WARNING...WE ARE CLOSE. CONFIDENCE IS HIGH IN HEAVY SNOW

AND DRIFTING...SOME DRIFTS 2-4 FEET IN SOUTHWEST WI...IMPASSABLE

ROADS AND DRIVEWAYS...AND CLOSED SCHOOLS/BUSINESSES BY THURSDAY. ON

RIDGE TOP COUNTRY IN SOUTHWEST WISCONSIN...DRIFTS COULD BE

HIGHER...AND LOCALIZED WHITEOUT CONDITIONS ARE LIKELY THURSDAY.

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Skilling with his daily 3 p.m. slot on Garry Meier mentions "half a foot" for areas north and west of the city "out towards McHenry and Walworth counties and Rockford." Said couple inches in city but that things could still change.

Didn't sound too weenieish there. I think he has always had the enthusiasm but just has more outlets now (as has been mentioned) where we can hear/see him a bit more unplugged.

Also just advised a caller to postpone their Thursday travel from Green Bay and Kenosha to the Dells (that advice looking rather obvious :)

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From NWS Des Moines...is this really true?

I WAS LOOKING AT WHETHER OR NOT TO KICK TO WATCH UP A NOTCH TO A

BLIZZARD WATCH GIVEN THE STRONG NORTH WINDS THAT WILL ACCOMPANY THIS

STORM. SUSTAINED WINDS OF 30 TO 40 MPH ARE QUITE LIKELY WITH SOME

POTENTIAL OF GUSTS 40+ MPH. AT THIS POINT HOWEVER WE HAVE NO SNOW

ON THE GROUND AND I RECALL THAT TO GET REDUCED VISIBILITY FOR A

SUSTAINED PERIOD OF TIME THERE SHOULD BE SOME EXISTING SNOW COVER.

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Skilling with his daily 3 p.m. slot on Garry Meier mentions "half a foot" for areas north and west of the city "out towards McHenry and Walworth counties and Rockford." Said couple inches in city but that things could still change.

Didn't sound too weeniesh there. I think he has always had the enthusiasm but just has more outlets now (as has been mentioned) where we can hear/see him a bit more unplugged.

Also just advised a caller to postpone their Thursday travel from Green Bay and Kenosha to the Dells (that advice looking rather obvious :)

Should be on the radio again around 6pm I believe.

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