Snow Advisory 1, NWS Indianapolis, IN

Boone County, IN, Carroll County, IN, Clay County, IN, Clinton County, IN, Delaware County, IN, Fountain County, IN, Hamilton County, IN, Hancock County, IN, Hendricks County, IN, Henry County, IN, Howard County, IN, Madison County, IN, Marion County, IN, Montgomery County, IN, Parke County, IN, Putnam County, IN, Randolph County, IN, Tippecanoe County, IN, Tipton County, IN, Vermillion County, IN, Vigo County, IN, Warren County, IN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
344 AM EST MON FEB 11 2008

.DISCUSSION...

FORECAST FOCUS IS ON WINTER STORM BEGINNING TONIGHT.

THE CURRENT SURFACE MAP SHOWED HIGH PRESSURE STRETCHING FROM
INDIANA NORTHWARD INTO MINNESOTA. THERE WERE A SERIES OF WEAK LOW
PRESSURE SYSTEMS ALONG THE FRONT RANGE OF THE ROCKIES. ALOFT AT H5
THERE WAS A GENERAL TROUGHING OVER THE EASTERN HALF OF THE CONUS
WITH RIDGING OVER THE WEST COAST. A STRONG SHORTWAVE TROUGH WAS
OVER CENTRAL MONTANA AND SLIDING TO THE SOUTHWEST INTO THE BROAD
TROUGH.

THE MODELS WERE FAIRLY SIMILAR IN THE GENERAL EVOLUTION OF THE
PATTERN. HOWEVER THE NAM WAS FASTER IN THE MOVEMENT OF THE SYSTEM.
THE GFS LINED UP MUCH BETTER WITH OTHER MODELS...THE SREF AND
ECMWF WERE CLOSER TO THE GFS THAN THE NAM. AND THEREFORE WILL SIDE
WITH THE GFS SOLUTION REGARDING THIS POTENTIAL WINTER STORM.

THE MAIN DIFFERENCES WITH USING THE GFS SOLUTION WERE THAT THE GFS
WAS A TOUCH FARTHER NORTH WITH ITS LOCATION OF HEAVIEST QPF. THE
NAM SHOWED THE HEAVIEST QPF ALONG AND SOUTH OF THE OHIO RIVER
WHILE THE GFS AXIS OF HEAVIEST QPF WAS OVER SOUTHWESTERN INDIANA.
HOWEVER...WENT WITH THE HPC QPF OVER THE MODEL FIELDS...AND THE
HPC VALUES WERE CONSIDERABLY LOWER THAN THE MODELS. THE OTHER MAIN
DIFFERENCE IS THAT THE NAM IS QUICKER TO MOVE THE SYSTEM EAST. IT
HAD A MUCH FARTHER NORTH TRACK OF THE H5 LOW AND ALSO HAD A DEEPER
H5 SYSTEM. AGAIN THIS WAS NOT SUPPORTED THROUGH A
CONSENSUS...WHICH THE GFS HAD WITH SEVERAL OTHER MODELS.

FOR TODAY...OVERRUNNING OF THE COLD ARCTIC AIR IN INDIANA WILL
TAKE PLACE ALL DAY. MID LEVEL MOISTURE IS ALREADY STREAMING IN AND
BRINGING CLOUDS. THIS WILL CONTINUE ALL DAY...AND SO HIGHS WILL
STRUGGLE TO MUCH BETTER THAN TEENS OR LOWER 20S...GIVEN THE FACT
THAT IT IS ONLY IN THE SINGLE NUMBERS NOW AND CLOUDS ARE EXPECTED
ALL DAY.

THE GFS SHOWS A SMALL SWATH OF LIGHT SNOW BY 18Z FROM A VORT MAX
OVER IOWA RIGHT NOW. DESPITE THE EXTREMELY DRY AIR...SOME LIGHT
SNOW HAS BEEN REPORTED IN SURFACE OBS IN IOWA. WILL MAKE A LAST
SECOND DECISION ON WHETHER OR NOT TO INCLUDE POPS FROM THE WEAK
NORTHERN SYSTEM BASED ON UPDATE SURFACE OBS.

OTHERWISE...WILL CONTINUE THE IDEA THAT THE ATMOSPHERE WILL TAKE
QUITE SOME TIME TO MOISTEN UP BEFORE PRECIP STARTS. BY 00Z A
FAIRLY DEEP AND CONCENTRATED LAYER OF FRONTOGENESIS IN THE LOW AND
MID LEVELS SHOULD HELP TO FORCE AND FOCUS PRECIPITATION TO DEVELOP
IN THE SOUTHWEST ZONES. AT ONSET...P TYPE SHOULD BE ALL SNOW.
ESPECIALLY GIVEN THE LOW SURFACE DEWPOINTS WHICH WILL ALLOW FOR
VERY EFFECTIVE EVAPORATIVE COOLING OF THE COLUMN.

OVERNIGHT TONIGHT...PRECIP WILL CRANK UP IN EARNEST AFTER 00Z AND
SPREAD NORTHWARD BY 06Z. STRONG FRONTOGENESIS IS SHOWN OVER THE
SOUTH CENTRAL PORTION OF THE AREA...WHICH IS INDEED WHERE THE
HEAVIEST QPF WILL FALL. BY 06Z THE GFS SHOWS A WARM FRONT STILL
WELL SOUTH OF THE AREA AND SO MOST OF THE PRECIP WILL STILL BE
SNOW. HOWEVER SOME WARM AIR WILL BEGIN TO WORK INTO THE SOUTHWEST
ZONES BY 06Z AND SO SLEET SHOULD BEGIN TO MIX IN THERE.
OTHERWISE...VERY HIGH RATIOS OF SNOW TO LIQUID ARE EXPECTED GIVEN
TEMPS IN THE TEENS AND LOW 20S.

THE MODEL SOUNDINGS INDICATE THAT BY 12Z PRECIP SHOULD BE ALL IN
THE FORM OF SLEET AND FREEZING RAIN IN THE FAR SOUTH AS TEMPS
AROUND 900MB WARM TO ABOVE 0C. FARTHER NORTH...THE CENTRAL AND
NORTHERN PARTS OF THE AREA SHOULD BE ALL SNOW BY DAYBREAK TUESDAY.

AFTER 12Z TUESDAY...THE GFS SHOWS THE LOW TRACKING UP THE OHIO
RIVER AND TO THE EAST. THIS WOULD FAVOR CHANGE OVER BACK TO ALL
SNOW IN WESTERN AREAS BY 18Z. IN THE SOUTHEAST...MUCH WARMER AIR
WILL WORK UP AHEAD OF THE H8 LOW TRACKING NEAR INDY. THIS WILL
ALLOW FOR SOME FREEZING RAIN AND EVEN JUST RAIN TO MIX IN FOR THE
SOUTHEAST ZONES DURING THE MORNING HOURS ON TUESDAY. THE SOUNDINGS
SUGGEST THE IT SHOULD REMAIN ALL SNOW FROM I-70 NORTHWARD.
TEMPERATURES SHOULD COOL THROUGH THE AFTERNOON AS COLDER AIR WORKS
IN BEHIND THE LOW.

TOTAL SNOWFALL IS EXPECTED GENERALLY FOUR TO SEVEN INCHES. SOME
ICING OF A TENTH OR TWO WILL BE POSSIBLE IN THE SOUTHERN TWO
TIERS OF COUNTIES. WITH ALL THIS IN MIND...WILL GO WITH A WINTER
STORM WARNING FOR ALL AREAS EXCEPT NORTHWESTERN COUNTIES. IN THAT
AREA...SNOW OF THREE TO FIVE INCHES WILL NOT BE ACCOMPANIED BY ANY
ICE SO JUST A SNOW ADVISORY THERE. COULD POSSIBLY GO JUST WITH A
HEAVY SNOW WARNING FOR THE NORTH...BUT WILL STICK WITH JUST A
WINTER STORM WARNING TO KEEP IT SIMPLER. ALSO THERE COULD POSSIBLY
BE SOME SLEET MIXING IN FARTHER NORTH IF THE MODELS ARE OFF ON THE
TRACK.

THIS STORM IS DIFFERENT FROM PREVIOUS STORMS THIS WINTER IN A FEW
WAYS. FIRST...THERE IS MUCH COLDER AIR IN PLACE...AND THIS SHOULD
ENSURE GOOD RATIOS OF LIQUID TO SNOW AND ALSO ALLOW FOR ALL SNOW
AT THE ONSET. MISSING IS THE STRONG SUBTROPICAL RIDGE OVER THE
BAHAMAS THAT WAS PRESENT DURING PREVIOUS STORMS. THIS RIDGE WAS
LIKELY PART OF THE PROBLEM WITH THE MODELS BEING TOO FAR SOUTH ON
PREVIOUS STORMS WITH THE LOW. SINCE THERE IS A MUCH COLDER AIRMASS
IN PLACE...IF THE MODELS ARE TOO FAR SOUTH THIS TIME...AT LEAST
SIGNIFICANT SNOW COULD STILL TAKE PLACE SINCE IT WILL BE COLDER.
ALSO THIS TIME...THERE IS NOT EXPECTED TO BE SIGNIFICANT WARM
SECTOR CONVECTION IN THE SOUTHEAST. THIS CONVECTION LAST TIME
PROBABLY ROBBED INDIANA OF THE DEEP MOISTURE FLOW.

FURTHER OUT PAST THE STORM...DID NOT MAKE MANY CHANGES TO THE
EXTENDED FORECAST. HIGH PRESSURE WILL BUILD IN BEHIND THE STORM
FOR WEDNESDAY. A NEW STRONG SYSTEM STARTS TO DIG IN THE ROCKIES ON
THURSDAY AND SENDS TEMPERATURES UPWARDS HERE. NEXT CHANCE FOR
PRECIP LOOKS TO BE FRIDAY...AND THEN POSSIBLY ANOTHER WINTER
HEADACHE THIS WEEKEND ALTHOUGH THE CURRENT GFS SHOWS THE NEXT
SYSTEM STAYING WELL SOUTH...OVER THE GULF COAST.

&&

.AVIATION...

DISCUSSION FOR 06Z TAFS

EXPECT MID CLOUDS AROUND BKN090 TO PERSIST OVERNIGHT WITH WINDS
AROUND 10KT MOST SITES. AS NEXT SYSTEM APPROACHES FROM THE SW DURING
THE DAY ON MONDAY CIGS WILL GRADUALLY LOWER BUT SHOULD REMAIN VFR
THRU 00Z. VERY DRY ATMS SHOULD INHIBIT PRECIP FROM REACHING THE
GROUND UNTIL AROUND 00Z AT HUF/BMG AND A FEW HOURS LATER AT LAF/IND.
WITH VERY COLD TEMPS TO START OFF WITH...PRECIP WILL BE SNOW. DID
NOT GET TOO DETAILED SINCE PRECIP WILL BE IN LAST 6 HOURS OF TAF
PD...BUT DID GO MVFR VSBYS AND LOW VFR TO MVFR CIGS IN -SN.
CONDITIONS WILL DETERIORATE AFT 06Z MON NIGHT.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 PM EST TUESDAY
FOR INZ037-039>042-045>049-053>057-060>065-067>072.

SNOW ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST TUESDAY FOR
INZ021-028>031-035-036-038-043-044-051-052.

&&

AVIATION...CS/SH
PUBLIC...JOHNSON

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1031 PM EST SUN FEB 10 2008

INZ044>049-051>057-060>065-067>072-111100-
PARKE-PUTNAM-HENDRICKS-MARION-HANCOCK-HENRY-VIGO-CLAY-OWEN-MORGAN-
JOHNSON-SHELBY-RUSH-SULLIVAN-GREENE-MONROE-BROWN-BARTHOLOMEW-
DECATUR-KNOX-DAVIESS-MARTIN-LAWRENCE-JACKSON-JENNINGS-
1031 PM EST SUN FEB 10 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL INDIANA.

.DAY ONE...TONIGHT.

SIGNIFICANT TO MAJOR FLOODING IS EXPECTED ON THE WHITE...EAST
FORK WHITE...WABASH AND OTHER CENTRAL INDIANA RIVERS. CHECK THE
LATEST FLOOD STATEMENT FOR FURTHER DETAILS.

BITTERLY COLD AIR WILL REMAIN ACROSS CENTRAL INDIANA TONIGHT.
TEMPERATURES WILL BOTTOM OUT IN THE SINGLE DIGITS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

SIGNIFICANT TO MAJOR FLOODING IS EXPECTED TO CONTINUE ON THE
WHITE...EAST FORK WHITE...WABASH AND OTHER CENTRAL INDIANA RIVERS.
CHECK THE LATEST FLOOD STATEMENT FOR FURTHER DETAILS.

A WINTER STORM WATCH HAS BEEN ISSUED FOR MONDAY NIGHT AND TUESDAY.
THERE IS A POTENTIAL OF 6 INCHES OF SNOW OR MORE AND SIGNIFICANT
AMOUNTS OF FREEZING RAIN.

.SPOTTER INFORMATION STATEMENT...

WINTER WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SNOW OR ICE
ACCUMULATIONS MONDAY NIGHT AND TUESDAY.

&&

MORE INFORMATION...ALONG WITH OTHER WEATHER...HYDROLOGICAL AND
CLIMATE INFORMATION CAN BE FOUND...AT HTTP://WEATHER.GOV/IND (ALL
LOWERCASE)

INZ021-028>031-035>043-111100-
CARROLL-WARREN-TIPPECANOE-CLINTON-HOWARD-FOUNTAIN-MONTGOMERY-
BOONE-TIPTON-HAMILTON-MADISON-DELAWARE-RANDOLPH-VERMILLION-
1031 PM EST SUN FEB 10 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL INDIANA.

.DAY ONE...TONIGHT.

BITTERLY COLD AIR WILL REMAIN ACROSS CENTRAL INDIANA TONIGHT.
TEMPERATURES WILL BOTTOM OUT AROUND ZERO.

SIGNIFICANT TO MAJOR FLOODING IS EXPECTED ON THE WHITE...EAST
FORK WHITE...WABASH AND OTHER CENTRAL INDIANA RIVERS. CHECK THE
LATEST FLOOD STATEMENT FOR FURTHER DETAILS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

A WINTER STORM WATCH HAS BEEN ISSUED FOR MONDAY NIGHT AND TUESDAY.
THERE IS A POTENTIAL OF 6 INCHES OF SNOW OR MORE AND SIGNIFICANT
AMOUNTS OF FREEZING RAIN.

SIGNIFICANT TO MAJOR FLOODING IS EXPECTED TO CONTINUE ON THE
WHITE...EAST FORK WHITE...WABASH AND OTHER CENTRAL INDIANA RIVERS.
CHECK THE LATEST FLOOD STATEMENT FOR FURTHER DETAILS.

.SPOTTER INFORMATION STATEMENT...

WINTER WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SNOW OR ICE
ACCUMULATIONS MONDAY NIGHT AND TUESDAY.

&&

MORE INFORMATION...ALONG WITH OTHER WEATHER...HYDROLOGICAL AND
CLIMATE INFORMATION CAN BE FOUND...AT HTTP://WEATHER.GOV/IND (ALL
LOWERCASE)

KOCH