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January 12-14 Winter Storm Part 2


Hoosier

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From the NWS in Northern Indiana AFD,at 411 pm today...

STILL SOME UNCERTAINTY

PER THE AMOUNT OF LAKE MI MODIFICATION TO PRECIP. THIS COMBINED

WITH THERMAL FIELD UNCERTAINTY SUPPORTS RIDING THE WATCH FOR

ANOTHER ROUND. WILL HIGHLIGHT AREAS OUTSIDE THE WATCH WITH AN

SPS...WITH AN ADV LIKELY FOR MANY OF THESE AREAS. WINDS WILL

INCREASE THROUGH THUR NIGHT...SW AREAS TO NE AS CAA INTENSIFIES

WITH THE ISALLOBARIC WIND NEARLY PARALLEL TO THE LL GEOSTROPHIC

WIND. EXPECT INCREASING AREAS OF BLOWING SNOW...WITH HAZARDOUS

DRIVING CONDITIONS AT MANY AREAS.

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From the NWS in Northern Indiana AFD,at 411 pm today...

STILL SOME UNCERTAINTY

PER THE AMOUNT OF LAKE MI MODIFICATION TO PRECIP. THIS COMBINED

WITH THERMAL FIELD UNCERTAINTY SUPPORTS RIDING THE WATCH FOR

ANOTHER ROUND. WILL HIGHLIGHT AREAS OUTSIDE THE WATCH WITH AN

SPS...WITH AN ADV LIKELY FOR MANY OF THESE AREAS. WINDS WILL

INCREASE THROUGH THUR NIGHT...SW AREAS TO NE AS CAA INTENSIFIES

WITH THE ISALLOBARIC WIND NEARLY PARALLEL TO THE LL GEOSTROPHIC

WIND. EXPECT INCREASING AREAS OF BLOWING SNOW...WITH HAZARDOUS

DRIVING CONDITIONS AT MANY AREAS.

Quite a bit of disagreement between IND and IWX. IND calling for changeover for Indianapolis by early afternoon. IWX saying changeover will hold off until evening...

A WINTER WEATHER ADVISORY IS IN EFFECT FROM THU 15Z - FRI 18Z.

CURRENT THINKING IS THAT RAIN WILL TRANSITION TO A RAIN/SNOW MIX

ACROSS THE NORTHWEST/WESTERN COUNTIES AROUND THU 15Z. ESTIMATED

TRANSITION TIME FOR THE INDY METRO IS THU 18Z...AND FINALLY SNOW

ACROSS ALL OF CENTRAL INDIANA BY MID AFTERNOON.

MODELS ARE INDICATING THAT BEST TIME FRAME FOR SNOW ACCUMULATION

WILL BE FRI 00-06Z. BEST QVECTOR CONVERGENCE AND FRONTOGENETIC

BANDING WILL BE ACROSS THE NORTHERN COUNTIES OF FORECAST AREA...WHICH

CAN EXPECT ABOUT 3 TO 5 INCHES OF SNOWFALL. FURTHER SOUTH...WENT

WITH 2 TO 4 INCHES OVER THE CENTRAL PORTIONS OF FORECAST

AREA...AND 1 TO 3 INCHES OVER THE SOUTHERN COUNTIES.

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New LOT discussion lays everything out nicely at what the expect:

000 FXUS63 KLOT 112053 AFDLOT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 253 PM CST WED JAN 11 2012 .DISCUSSION... 243 PM CST WINTER STORM...TONIGHT THROUGH FRIDAY NIGHT... HAVE ISSUED WINTER WEATHER ADVISORIES FOR SNOW AND BLOWING SNOW WHICH WILL COVER THE CWA FOR THURSDAY INTO EARLY FRIDAY. STRONG SHORT WAVE TROUGH DIGGING SOUTHEAST ACROSS THE NORTHERN PLAINS WILL CONTINUE TO CARVE OUT A DEEP UPPER TROUGH ACROSS THE CENTRAL CONUS TONIGHT/THURSDAY...WITH A CLOSED UPPER LOW DEVELOPING ACROSS THE MID-MISSISSIPPI VALLEY. PRE-EXISTING SURFACE LOW PRESSURE OVER THE OHIO VALLEY WILL DEEPEN AND LIFT NORTH INTO THE GREAT LAKES REGION IN RESPONSE TO DEVELOPING UPPER LOW...AND STRONG LOW LEVEL BAROCLINICITY WITH INTRUSION OF LOW LEVEL ARCTIC AIR. UPPER DIVERGENCE IN LEFT EXIT REGION OF CYCLONICALLY CURVED UPPER JET STREAK WILL ALSO AID IN DEVELOPING DEEP SYNOPTIC SCALE ASCENT ACROSS THE THE AREA. 12Z MODEL GUIDANCE IS GENERALLY IN VERY GOOD AGREEMENT IN DEPICTION OF EVOLUTION OF SYSTEM OVER THE NEXT 36 HOURS...SAVE FOR SOME QPF DIFFERENCES...WITH THE WRF-NAM BEING MORE GENEROUS WITH THE PRECIP/SNOW AMOUNTS. GUIDANCE DOES INDICATE THAT THE GREATEST AMOUNTS WILL LIKELY BE ACROSS NORTHEAST IL/NORTHWEST INDIANA WHERE SOME LAKE-ENHANCEMENT POTENTIAL EXISTS...AND WHERE LARGER SCALE DEFORMATION AXIS EVENTUALLY SETS UP AS SYSTEM DEEPENS AND MOVES OFF TO THE EAST-NORTHEAST LATER THURSDAY AND THURSDAY NIGHT. WHILE FORCING DECREASES QUICKLY LATE THURSDAY NIGHT...LIGHTER SNOW/SNOW SHOWERS IS/ARE EXPECTED TO CONTINUE INTO FRIDAY MORNING. THE PERIOD MOST FAVORABLE FOR MORE SIGNIFICANT ACCUMULATION WILL SLIDE FROM WEST TO EAST ACROSS THE AREA FROM MID THURSDAY MORNING THROUGH VERY EARLY FRIDAY EVENING. SNOWFALL AMOUNTS ARE TRICKY WITH THIS SYSTEM...LARGELY DUE TO DEGREE OF COOLING OF THE COLUMN AS DEPTH OF ARCTIC AIR INCREASES LATE THURSDAY AND THURSDAY NIGHT...AS WELL AS DUE TO AFOREMENTIONED POTENTIAL FOR LAKE-ENHANCEMENT IN COUNTIES BORDERING LAKE MICHIGAN. MODEL SNOW/LIQUID RATIOS RANGE FROM 10:1 AT ONSET...TO 15 OR 20:1 LATER IN THE EVENT. HAVE GENERALLY USED HPC QPF...WITH A LITTLE BLENDING OF WRF OUTPUT...AND RATIOS RANGING FROM 10:1 TO 17:1 THROUGH THE EVENT FOR SNOWFALL FORECAST. THIS YIELDS ROUGHLY 3-5 INCHES ACROSS SOUTHWESTERN CWA...TO 4-6 INCHES FOR NORTHEAST CWA COUNTIES NOT ALONG THE LAKE...TO 4-8 INCHES FOR THE LAKE ADJOINING COUNTIES. ACCUMULATING SNOWFALL IS EXPECTED TO BE OVER NEARLY A 24 HOUR PERIOD...THOUGH EXPECT IT WILL FALL JUST SHORT OF THE 6 INCHES IN 12 HOURS OR 8 INCHES IN 24 HOURS CRITERIA FOR WINTER STORM WARNING. BASED ON THIS...AND COLLABORATION WITH MKX/ILX AND IWX HAVE ELECTED TO ISSUE A WINTER WEATHER ADVISORY FOR SNOW AND BLOWING SNOW. NORTHWEST WINDS ARE EXPECTED TO INCREASE TO 20-25 MPH THURSDAY AFTERNOON...AND MAY GUST 30-35 MPH THURSDAY NIGHT AS LOW DEEPENS OFF TO OUR EAST. THIS WILL LIKELY RESULT IN SIGNIFICANT BLOWING AND DRIFTING SNOW PARTICULARLY IN OPEN/RURAL AREAS. IN ADDITION TO THE BLOWING/DRIFTING ISSUES...THESE WINDS WILL COMBINE WITH ARCTIC AIR TO PRODUCE WIND CHILLS IN THE ZERO TO -10 F RANGE THURSDAY NIGHT/EARLY FRIDAY MORNING.

RATZER

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trend though....both nam and gfs are much more snowy for OH than they have been, especially in eastern areas. 18z NAM is easy advisory snow for cmh

this may be our best chance all winter, I'm getting excited.

I know hopefully that band in eastern Ohio moves further west. Dry slot is not that dry though still 0.30 precip.

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