Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 280915
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
415 AM EST SAT FEB 28 2015

.SYNOPSIS...
ISSUED AT 100 AM EST SAT FEB 28 2015

HIGH PRESSURE WILL DRIFT ACROSS THE AREA TODAY WITH DRY
CONDITIONS...BUT BELOW NORMAL TEMPERATURES. THE FIRST OF 2 WINTER
SYSTEMS WILL THEN TAKE AIM ON THE AREA STARTING TONIGHT...BRINGING
ACCUMULATING SNOW TO THE AREA. HIGHS TODAY WILL REBOUND TO AROUND
20 DEGREES...BUT WILL STILL CLOSE TO 20 DEGREES BELOW NORMAL.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 411 AM EST SAT FEB 28 2015

A LARGE SURFACE HIGH PRESSURE AREA WITH A CENTER READING CLOSE TO
1040 MILLIBARS WILL MOVE EAST OUT OF THE AREA AS RETURN FLOW
INCREASES ON THE BACK SIDE OF THE HIGH PRESSURE AREA. A LARGE UPPER
TROF WILL SHEAR OUT EAST AS THE REMAINDER OF THE LONGWAVE TROF
REMAINS OVER THE WEST CONUS. FAVOR THE GFS WITH DEEPER SATURATION.
EXPECT SNOW TO DEVELOP TONIGHT GIVEN FAVORABLE UPPER LEVEL JET
SUPPORT AND ISENTROPIC LIFT. THE BEST LIFT AND MOISTURE WILL BE OVER
SOUTHERN AREAS WHERE AROUND 2 INCHES OF SNOW IS LIKELY BY LATE
TONIGHT. LESSER AMOUNTS ARE EXPECTED FARTHER NORTH INCLUDING FAR
SOUTHERN LOWER MICHIGAN. OTHERWISE...THIS WILL BE THE LAST OF THE
FRIGID MORNINGS FOR AT LEAST A LITTLE WHILE GIVEN MODERATING
TEMPERATURES AND INCREASING CLOUDS AHEAD OF THIS NEXT SYSTEM.
TEMPERATURES EARLY THIS MORNING WERE SOMEWHAT SIMILAR TO FRIDAY
MORNING WITH 4 AM EST READINGS CLOSE TO -10 IN SOME AREAS. THIS
SHALLOW INVERSION WILL MIX OUT RAPIDLY ALLOWING TEMPERATURES TO
QUICKLY RECOVER.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 411 AM EST SAT FEB 28 2015

AS WE HAVE SEEN NUMEROUS TIMES THIS WINTER LATEST MODEL GUIDANCE HAS
TRENDED SLIGHTLY SOUTHWARD WITH BOTH STRONG STORM SYSTEMS COMING UP
FOR SUNDAY AND TUESDAY. STILL EXPECTING IMPACTS FROM BOTH BUT LATEST
GUIDANCE AND TRENDS SUGGEST WE WILL BE ON NORTHERN FRINGE OF BOTH
SYSTEMS. STILL VERY CAUTIOUS WITH WAVERING SOLUTIONS...ESPECIALLY
WITH THE TUESDAY EVENT AS MAIN ENERGY FOR THAT STILL IN LARGELY VOID
REGION OF UPPER AIR NETWORK.

SNOW WILL BE ONGOING SUNDAY AS LOW LEVEL JET AND STRENGTHENING UPPER
LEVEL JET COMBINE TO BRING LOW LEVEL MOISTURE AND BROAD LIFT ACROSS
THE AREA. SYSTEM RELATIVE ISENTROPIC REMAINS IMPRESSIVE WITH STRONG
WIND CONVERGENCE AND ORTHOGONAL COMPONENT TO PRESSURE SURFACES ALONG
WITH 2-3 G/KG MIXING RATIOS AND 4 G/KG JUST TO OUR SOUTH. BEST LIFT
FROM THIS REMAINS FOCUSED ALONG OUR SOUTHERN BORDER COUNTIES DURING
THE DAY. THIS ALSO SAME REGION WHERE NEAR SURFACE TEMPS WILL RISE TO
NEAR FREEZING BY EARLY AFTERNOON. THIS SHOULD AID IN COMPACTION AS
WELL AS HELPING MELT SOME OF THE SNOW ON ROADS...LIMITING
ACCUMULATIONS AS WELL AS IMPACTS. HIGHEST AXIS OF QPF HAS SHIFTED
SOUTH OF OUR AREA BUT STILL COMING UP WITH JUST OVER A TENTH OF AN
INCH NORTH...QUARTER INCH CENTRAL AND NEAR A HALF INCH SOUTH. NAM12
SNOW RATIOS START AROUND 15 TO 1 BUT DOWN TO NEAR 10 TO 1 IN SOUTH
WITH AFTERNOON WARMING. THIS SHOULD HELP LOWER ACCUMS SOUTH DESPITE
UPTICK IN QPF DURING THE DAY. DGZ STILL DEPICTED TO BE RATHER HIGH
AND NEAR THE TOP OF DEEPER MOISTURE. ALL THESE SIGNS POINT TOWARD
TOTAL ACCUMS OF 1 TO 3 NORTH...2 TO 4 CENTRAL AND 3 TO 6 FAR SOUTH.
ANY FURTHER SOUTHWARD SHIFT WILL PUSH ACCUMS TOWARD THE LOWER END OF
THESE VALUES. MUST REMIND EVERYONE TO FOCUS ON THE RANGE OF POSSIBLE
ACCUMS AND NOT THE HIGH NUMBERS. AFTER COLLABORATION WITH
NEIGHBORING OFFICES DECIDED CONFIDENCE BETTER FURTHER SOUTH FOR
HEADLINES AND NORTHERN TIER OFFICES OPTED TO HOLD OFF UNTIL LATER
TODAY FOR POSSIBLE ADDITIONAL ADVISORIES ON NORTHERN FRINGE.

SECOND SYSTEM FOR MONDAY NIGHT AND TUESDAY STILL LOOKS ON TRACK. GFS
STARTING TO BACK OFF ON PCPN ARRIVAL UNTIL TUESDAY. KEPT LOW TO MID
CHANCE POPS GOING LATE MONDAY NIGHT. THIS LATER ARRIVAL WILL
ACTUALLY ALLOW LOW TEMPS TO DROP MONDAY NIGHT INTO TEENS AND LOWER
20S. STILL EXPECT ACTUAL SFC TEMPS TO LAG WARMING ALOFT TUE GIVEN
THE CURRENT ARCTIC AIR IN PLACE WITH DEEP AND FRESH SNOWPACK AND A
FROZEN GROUND DOWN TO A DEPTH OF NEARLY A FOOT. THEREFORE PERIOD OF
FREEZING PCPN TUESDAY MORNING STILL LOOKS POSSIBLE AT ONSET AND WILL
KEEP THE MIXED TYPE IN FORECAST. ALSO A LITTLE CONCERN THAT DESPITE
MEASURED 2M AIR TEMPS RISING ABOVE FREEZING...ACTUAL SFC TEMPS MAY
REMAIN AT OR BELOW FREEZING A LITTLE LONGER DUE TO THE EXTREME COLD
AND SNOW PACK. THIS IS SIMILAR TO AN EVENT LAST WINTER IN NORTHERN
IL WHERE FREEZING RAIN CONTINUED ON SURFACES DESPITE AIR TEMPS IN
THE MID TO UPPER 30S FOR SEVERAL HOURS. THIS IS RARE BUT HAS
OCCURRED FOLLOWING PROLONGED EXTREME COLD EVENTS. SOMETHING TO KEEP
IN MIND TUESDAY ESPECIALLY ACROSS OUR FAR NORTH AND NORTHEAST. FOR
NOW KEPT TREND OF ENDING FREEZING PCPN ALL AREAS BY 18Z AS WARM AIR
ALOFT INCREASES AND DEEPENS. RAIN THEN EXPECTED THROUGH AFTERNOON
AND INTO EARLY EVENING. AGAIN...HIGHEST QPF AXIS HAS SHIFTED SOUTH
BUT MODELS STILL GENERATING RESPECTABLE AMOUNTS FOR SOUTHERN HALF OF
CWA WITH AN INCH OR SO POSSIBLE. THIS WOULD STILL BE ENOUGH FOR
FLOODING CONCERNS WITH FROZEN GROUND...STORM DRAINS BLOCKED BY
SNOW...AND RIVERS BEING FROZEN LEADING TO POSSIBLE ICE JAM FLOODING.

COLD AIR WILL SLOWLY SPILL IN FROM NORTHWEST TUE NIGHT CHANGING ANY
PCPN OVER TO LIGHT SNOW FROM WEST TO EAST. A RETURN TO DEEP FREEZE
THEN EXPECTED WITH TEMPS BACK WELL BELOW NORMAL FOR EARLY MARCH WITH
POSSIBILITY OF SINGLE DIGITS AND EVEN SOME MORE BELOW ZERO TEMPS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1255 AM EST SAT FEB 28 2015

A 1041 MB HIGH PRESSURE WILL DRIFT OVER THE AREA THIS MORNING WITH
CALM OR NEARLY CALM WINDS. LIGHT SNOW IS POSSIBLE BY THE END OF
THE TAF PERIOD AS RETURN FLOW BECOMES ESTABLISHED WITH INCREASING
MOISTURE IN THE LOW LEVELS.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...SKIPPER
SHORT TERM...SKIPPER
LONG TERM...LASHLEY
AVIATION...SKIPPER


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