Possible 1" Ice for Central Indiana. Blizzard for Chicago.
Posted by JAC on 1/31/2011, 7:28 am






SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
244 AM EST MON JAN 31 2011

VALID 12Z MON JAN 31 2011 - 12Z WED FEB 02 2011

A MAJOR WINTER STORM IS TAKING AIM AT THE CENTER OF THE COUNTRY
THIS MORNING. A LARGE SWATH OF LIGHT SNOW IS BLANKETING THE
NORTHERN PLAINS AND UPPER MIDWEST...WHILE SCATTERED SNOW SHOWERS
FALL ALONG A STATIONARY BOUNDARY DRAPED ALONG THE ROCKIES. THE
CENTRAL U.S. SNOW SWATH WILL STEADILY PROGRESS EASTWARD THROUGHOUT
THE DAY MONDAY...EXPANDING SOUTHWARD INTO THE CENTRAL PLAINS
MONDAY AFTERNOON AND EVENTUALLY LINKING UP WITH THE PLUME OF
MOISTURE MOVING OVER THE SOUTHEAST BY MONDAY EVENING.  

A RAPIDLY DEEPENING UPPER-LEVEL TROUGH AND AN INTENSIFYING
DISTURBANCE OVER THE SOUTHWEST WILL DRIVE THIS SYSTEM. A LARGE
AMOUNT OF GULF MOISTURE WILL FEED INTO THE SYSTEM AHEAD OF THE
INCREDIBLY STRONG SURFACE FRONT OVER THE SOUTHERN PLAINS. AS THE
UPPER-LEVEL ENERGY KICK STARTS THE QUASI-STATIONARY BOUNDARY LATE
MONDAY NIGHT INTO EARLY TUESDAY...PRECIPITATION AMOUNTS ARE GOING
TO QUICKLY INCREASE. MODERATE ICE AND SNOW WILL BE A MAJOR CONCERN
ACROSS THE CENTRAL AND SOUTHERN PLAINS...CENTRAL MISSISSIPPI
VALLEY AND OHIO VALLEY BEGINNING EARLY TUESDAY. THE BAND OF ICING
WILL REMAIN FAIRLY CONSTANT THROUGHOUT THIS EVENT...BRINGING
DANGEROUS AMOUNTS OF SLEET AND FREEZING RAIN TO SEVERAL LARGE
CITIES ACROSS THE MIDWEST. MORE RAIN AND THUNDERSTORMS WILL PLAGUE
THE WESTERN GULF COAST REGION ON TUESDAY. SOME OF THESE
THUNDERSTORMS MAY BE SEVERE.  

THE EAST COAST WILL BEGIN TO GET IN ON THE WINTER WEATHER ACTION
MONDAY NIGHT AS THE PRECIPITATION BEGINS TO NOSE ITS WAY OVER THE
APPALACHIANS. BY TUESDAY MORNING THE MID-ATLANTIC AND SOUTHERN NEW
ENGLAND STATES WILL BE IN THE MIX. AS THE MAIN LOW BEGINS TO WRAP
UP OVER THE TENNESSEE VALLEY ON TUESDAY EVENING MODERATE TO HEAVY
PRECIPITATION WILL COVER MOST OF THE OHIO AND TENNESSEE VALLEYS
AND WILL BE POISED TO PRESS EASTWARD TOWARDS THE ATLANTIC COAST ON
WEDNESDAY.


URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE CHICAGO IL
354 AM CST MON JAN 31 2011

...DANGEROUS MULTIFACETED AND POTENTIALLY LIFE THREATENING WINTER
STORM TAKING AIM ON REGION...

A BLIZZARD WATCH REMAINS IN EFFECT FROM TUESDAY AFTERNOON THROUGH
WEDNESDAY AFTERNOON.

* TIMING...SNOW WILL INCREASE IN INTENSITY AND BECOME HEAVY AT
 TIMES SOUTH OF INTERSTATE 80 TUESDAY AFTERNOON...GRADUALLY
 SPREADING NORTH INTO NORTHERN ILLINOIS BY TUESDAY EVENING.
 SNOW...HEAVY AT TIMES...WILL CONTINUE TUESDAY NIGHT INTO
 WEDNESDAY MORNING. SNOW SHOWERS WILL CONTINUE NEAR LAKE MICHIGAN
 IN NORTHEAST LLINOIS WEDNESDAY MORNING...SHIFTING INTO NORTHWEST
 INDIANA DURING THE AFTERNOON. NORTHEAST WINDS OF 25 TO 40 MPH
 WITH STRONGER GUSTS WILL RESULT IN BLIZZARD CONDITIONS
 DEVELOPING TUESDAY EVENING AND CONTINUING THROUGH THE OVERNIGHT
 HOURS.

* ACCUMULATIONS...SNOW ACCUMULATIONS IN EXCESS OF A FOOT ARE
 EXPECTED OVER MUCH OF THE WATCH AREA FROM TUESDAY AFTERNOON
 THROUGH WEDNESDAY AFTERNOON. LOCALIZED TOTALS IN EXCESS OF 18
 INCHES ARE POSSIBLE...ESPECIALLY NEAR THE LAKE.

* HAZARDS...WHITE-OUT CONDITIONS ARE EXPECTED AT TIMES TUESDAY
 NIGHT AS VERY HEAVY SNOW AND STRONG WINDS RESULT IN BLIZZARD
 CONDITIONS. SNOWFALL RATES OF AT LEAST 2 TO 3 INCHES PER HOUR
 ARE POSSIBLE...ESPECIALLY WITH ANY THUNDERSTORMS THAT OCCUR.

* IMPACTS...CONDITIONS WILL RAPIDLY DETERIORATE FROM NORTH TO
 SOUTH ACROSS THE REGION TUESDAY AFTERNOON...WITH TRAVEL LIKELY
 BECOMING VIRTUALLY IMPOSSIBLE AT TIMES TUESDAY NIGHT INTO EARLY
 WEDNESDAY MORNING. SNOW IS EXPECTED TO FALL SO HEAVILY AT TIMES
 TUESDAY NIGHT THAT PLOWS WILL BE UNABLE TO KEEP UP WITH THE
 SNOW...WITH MANY SIDE STREETS AND UNTREATED ROADS BECOMING
 IMPASSABLE.


FIRST...A VERY STRONG 500MB NEGATIVELY TILTED UPPER WAVE WILL PUSH
ACROSS THE OHIO VALLEY AND CENTRAL INDIANA.
SECOND...GFS CONTINUES TO SHOW A REGION OF COUPLING OVER THE
CENTRAL PLAINS WITH A RIGHT REAR SECTION PUSHING ACROSS THE GREAT
LAKES AND A LEFT FRONT AREA PUSHING INTO INDIANA.
THIRD...700MB TRACK SHOWS CLOSED LOW PUSHING ACROSS CENTRAL
INDIANA...AN INDICATOR FOR HEAVY SNOW WHERE IT IS COLD ENOUGH.
FOURTH...UPPER LEVEL Q VECTOR DIVERGENCE IS VERY STRONG AS THIS
SYSTEM APPROACHES AND PASSES CENTRAL INDIANA...APPROACHING EXTREME
VALUES. FIFTH...POTENTIAL VORTICITY SHOWS AN AXIS OF A VERY HIGH
GRADIENT PUSHING ACROSS CENTRAL INDIANA ON TUESDAY NIGHT.
SIXTH...850MB LOWER LEVEL JET SHOWS A 70 TO 80 KNOT JET AHEAD OF
THE LOW POISED TO PUSH INTO CENTRAL INDIANA.
SEVENTH...290K ISENTROPIC SURFACE AGAIN SHOWS VERY STRONG
ISENTROPIC LIFT WITH MIXING RATIOS ABOVE 5 G/KG.
EIGHTH...FRONTOGENESIS CROSS SECTIONS SHOW THE STRONG THERMAL
ZONAL...NEARLY VERTICAL ON TUESDAY NIGHT...WITH VALUES IN EXCESS
OF 100...WHICH IS VERY HIGH.
NINTH...TIME SECTIONS INDICATE DEEP SATURATION WITH STRONG LIFT.
TENTH...FORECAST SOUNDINGS ACROSS THE AREA SHOW DEEP
SATURATION...AND ONLY THOSE IN THE NORTHWEST FORECAST AREA SHOW
THE ENTIRE SOUNDING BELOW 0C. MUCH OF THE I-70 CORRIDOR REVEALS
A CLASSIC FREEZING RAIN SOUNDING...WHILE FORECAST SOUNDINGS ACROSS
THE FAR SOUTHERN FORECAST AREA FLIRT WITH TEMPERATURES ABOVE
FREEZING...WHICH IS GOOD NEWS FOR FOLKS IN THAT AREA.
ELEVENTH...PRECIPITATABLE WATER REMAINS NEAR ONE HALF AND 0.80
INCHES THROUGH THE TIME PERIOD...GIVEN THE FORCING...AMOUNTS NEAR
AN AN INCH SEEM VERY REASONABLE IF NOT PERHAPS A BIT CONSERVATIVE.

I COULD CONTINUE WITH A FEW MORE THINGS...BUT AGAIN...THE CASE HAS
BEEN MADE. IT DOES NOT APPEAR THAT THIS SYSTEM IS MISSING MUCH OF
ANYTHING. GIVEN ALL OF THIS I THINK IT WOULD BE A GOOD IDEA TO HAVE
100 PERCENT POPS THROUGH THE TIME PERIOD ALONG. GIVEN THE ONGOING
PRECIPITATION WILL TREND TEMPERATURES NEARLY STEADY STATE NEAR
WETBULBS.

GFS DOES HINT AT THE WARM FRONT PUNCHING NORTH TO IND BRIEFLY
AHEAD OF THE COLD FRONT LATE TUESDAY NIGHT. NAM DOES NOT SUPPORT
THIS FEATURE YET. FOR NOW...THIS APPEAR TO BE A MINOR DETAIL IN
WHAT WILL BE AN EXTENDED PERIOD OF FREEZING RAIN FOR MUCH OF THE
I-70 CORRIDOR ON TUESDAY.

WINDS OF 15 TO 25 MPH WITH HIGHER GUSTS ARE EXPECTED ON TUESDAY
NIGHT INTO WEDNESDAY AS THE DEEPENING SURFACE LOW PRESSURE SYSTEM
AND ITS STRONG PRESSURE GRADIENT PUSHES TO THE SOUTH OF INDIANA
ALONG THE OHIO RIVER. THIS COULD RESULT IN DEVASTATING CONDITIONS
FOR CENTRAL INDIANA. THE COMBINATION OF AN INCH OF ICE ALONG WITH
WINDS OF THIS MAGNITUDE WILL LIKELY RESULT WIDESPREAD TREES AND
POWER LINES DOWN. GIVEN THE LARGE EXTENT OF THE AREA THAT MAY BE
EFFECTED...LONG DURATION POWER OUTAGES APPEAR POSSIBLE.




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Conclues PDS Winter Storm - JAC, 1/30/2011, 8:07 pm
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