Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 011105
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
605 AM EST SUN MAR 1 2015

.SYNOPSIS...
ISSUED AT 229 AM EST SUN MAR 1 2015

AN UPPER LEVEL DISTURBANCE WILL MOVE ACROSS OUR AREA TODAY BRINGING
SNOW TO THE REGION. THE HIGHEST SNOWFALL AMOUNTS WILL BE SOUTH OF
HIGHWAY 30 WHERE AN ADDITIONAL 3 TO 4 INCHES ARE EXPECTED. AMOUNTS
OVER SOUTHWEST MICHIGAN WILL BE LESS THAN AN INCH. HIGHS TODAY
AND MONDAY WILL BE IN THE UPPER 20S. LOWS TONIGHT WILL BE AROUND
15 DEGREES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 443 AM EST SUN MAR 1 2015

SEVERAL FACTORS COMING TOGETHER FOR ACCUMULATING SNOW WITH THE
POTENTIAL FOR EVENT SNOWFALL TOTALS TO EXCEED 6 INCHES BY THIS
EVENING. FAVOR THE GFS WHICH HAS BEEN CONSISTENT WITH THIS SYSTEM
AND APPEARS TO HAVE A BETTER HANDLE THAN THE NAM WITH THE MID AND
UPPER LEVEL MOISTURE FIELDS ASSOCIATED WITH THIS SYSTEM AND ALSO THE
DRY SLOT MOVING INTO THE AREA. AN UPPER LEVEL TROF WILL MOVE EAST AND
WILL BE ABLE TO TAP SOME MID LEVEL MOISTURE AS ISENTROPIC LIFT
PERSISTS ON THE 290K SURFACE. ALSO... MESO BANDING IS POSSIBLE GIVEN
FAVORABLE EQUIVALENT POTENTIAL VORTICITY OVER AN AREA OF
FRONTOGENESIS...MAINLY SOUTH OF HIGHWAY 30. IN ADDITION TO
THIS...THE DENDRITIC GROWTH ZONE IS IN THE CLOUD LAYER. OVERNIGHT
SNOW RATIOS TO LIQUID HAVE BEEN AROUND 14 TO 1. EXPECT THE HEAVIEST
SNOW WHERE THE ABOVE FACTORS COME TOGETHER BEST ON THE SOUTHEAST
FRINGE OF THE FORECAST AREA FROM MARION TO PORTLAND TO LIMA.
ANTICIPATE EVENT TOTAL SNOWFALL IN THIS AREA AROUND 7 INCHES... WITH
LESSER AMOUNTS FARTHER NORTH. GIVEN THE RELATIVELY LONG DURATION OF
THIS EVENT WITH MAINLY LIGHT SNOW WITHOUT BLOWING AND DRIFTING
SNOW...HAVE DECIDED NOT TO UPGRADE TO A WINTER STORM WARNING.

&&

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 443 AM EST SUN MAR 1 2015

INTENSE FOCUS CONTINUES ON STRONG STORM SYSTEM MONDAY NIGHT THROUGH
TUE NIGHT WITH PRECIPITATION TYPE REMAINING THE BIGGEST CONCERN AND
QUESTION. OVERALL MODELS IN AGREEMENT SYNOPTICALLY BUT AS IS ALWAYS
THE CASE...IMPORTANT THERMODYNAMIC DETAILS VARY SIGNIFICANTLY AMONG
THE MODELS AND THERE REMAINS NO CLEAR ANSWER.

WATER VAPOR SHOWS UPPER LEVEL LOW DROPPING SOUTH ALONG CA COAST THIS
MORNING AS EXPECTED. WEST SOUTHWEST FLOW ALOFT CONTINUES FROM
SOUTHWEST CONUS INTO THE MIDWEST. LEADING NOSE OF SUBTROPICAL
MOISTURE PLUME ORIGINATING OVER SOUTH CENTRAL PACIFIC ALREADY RACING
NORTHEAST INTO WEST TEXAS THIS MORNING. THIS DEEP MOISTURE PLUME
STILL EXPECTED TO BE TAPPED BY EJECTING LOW MONDAY AND WILL SPREAD
INTO OUR AREA BY TUESDAY.

THE CHALLENGE WITH THIS FORECAST CONTINUES TO BE FOCUSED ON PCPN
TYPE TUESDAY MORNING. MODELS HAVE TRENDED COOLER...ESPECIALLY LATE
MONDAY NIGHT WHERE THERMAL PROFILES SUGGEST ALL SNOW INITIALLY.
LATEST RUNS HAVE ALSO BROUGHT LIGHT QPF BACK INTO WESTERN AREAS
AFTER 09Z. EXPECT ANY PCPN THAT DOES FALL PRIOR TO 12Z TO BE LIGHT
SNOW.

OF REAL CONCERN IS THE TREND IN LATEST ECMWF AND NAM12 WITH COOLER
SFC TEMPS TUESDAY. BOTH MODELS MASS 2M TEMP FIELDS NOW BARELY BRING
THE 32F ISOTHERM INTO THE SOUTHWEST THIRD OF AREA BY 18Z BUT THEN
QUICKLY WARM TEMPS INTO MID TO UPPER 30S BETWEEN 18 AND 00Z. GFS
REMAINS MUCH FASTER WITH WARMING AS IT HAS ALL AREAS GENERALLY ABOVE
32F BY 18Z. AS WE HAVE BEEN DISCUSSING...THE DEEP SNOWPACK AND
RETREATING HIGH PRESSURE SHOULD HELP KEEP A COLD WEDGE NEAR THE
SURFACE TUE MORNING UNTIL THE STRONGER WARMER AIR ADVECTION ALOFT
OVERWHELMS LOWER LEVELS IN AFTERNOON. ECMWF HAS SHOWN GOOD
VERIFICATION SCORES RECENTLY WITH RESPECT TO MAX AND MIN TEMPS AND
NAM12 SHOULD HAVE A BETTER HANDLE ON THE LOWER LEVELS COMPARED TO
GFS DESPITE ITS RECENT UPGRADES. HAVE USED OUR POWT PROCEDURES TO
GENERATE PCPN TYPE WEATHER GRIDS FOR TUE. UNFORTUNATELY WE ARE NOT
ABLE TO INGEST MAXT ALOFT FROM ECMWF SO HAD TO USE NAM12 FOR THIS
WITH MANUAL ADJUSTMENT TOWARD EXPECTED ECMWF TEMPS. RESULT IS AS
EXPECTED WITH MOST AREAS SEEING SNOW INITIALLY TUE MORNING BUT
QUICKLY TRANSITIONING TO A FEW HOURS OF FREEZING RAIN AND SLEET
BEFORE FINALLY CHANGING TO ALL RAIN IN AFTERNOON. THIS RESULTS IN A
FEW INCHES OF SNOW CENTRAL AND NORTH FOLLOWED BY FREEZING RAIN WITH
ICE ACCUMULATIONS BETWEEN ONE AND TWO TENTHS DEPENDING ON AMOUNT OF
TIME BELOW FREEZING. A REAL MESSY SITUATION CERTAINLY APPEARS ON
TRACK FOR MOST AREAS WITH SNOW...ICE THEN RAIN...TRANSITIONING FROM
SOUTH TO NORTH. MORE THAN LIKELY WE ARE LOOKING AT AN ADVISORY LEVEL
SITUATION AT THIS TIME. HOWEVER...IF SFC TEMPS DO NOT WARM ABOVE
FREEZING UNTIL LATER IN DAY...MORE ICE WOULD BE POSSIBLE AND COULD
SEE SOME AREAS FLIRT WITH ICE STORM WARNING CRITERIA OF A QUARTER
INCH. HOPEFULLY MODEL THERMAL FIELDS WILL COME INTO BETTER ALIGNMENT
OVER NEXT 24 TO 36 HOURS.

THE HEAVY RAIN POTENTIAL IS QUICKLY DIMINISHING AS MODEL QPF HAS
DECREASED SUBSTANTIALLY LAST SEVERAL RUNS. HOWEVER...STILL LOOKS
LIKE A HALF INCH TO POSSIBLY THREE QUARTERS OF AN INCH OF PCPN COULD
FALL. DEEPER SNOWPACK MAY ACTUALLY ABSORB A LOT OF THIS AND DELAY
RUNOFF. THIS VERY DIFFICULT TO DETERMINE AND WILL STILL MENTION
LOCAL FLOODING POSSIBILITY IN HWO WITH ICE JAM POTENTIAL AND SNOW
PACKED STORM DRAINS POSSIBLY INHIBITING PROPER DRAINAGE.

REMAINDER OF FORECAST GENERALLY FOLLOWS SUPERBLEND AS LOADED.
TURNING VERY COLD AGAIN BEHIND THIS SYSTEM MID WEEK WITH HIGHS IN
TEENS AND LOWS AROUND ZERO.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 602 AM EST SUN MAR 1 2015

LOW CLOUDS ARE EXPECTED TO SPREAD BACK INTO SBN LATER THIS
MORNING...HOWEVER...SNOW AT FT WAYNE SHOULD CONTINUE WITH
FAVORABLE LIFT OVER THIS AREA. OVERALL...WINDS SHOULD BE LIGHT
WITHOUT BLOWING AND DRIFTING SNOW...BUT VSBYS SHOULD STAY BETWEEN
1 AND 2 MILES AT FT WAYNE WITH THE FALLING SNOW.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
     INZ022>027-032>034.

MI...NONE.
OH...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR OHZ016-
     024-025.

LM...NONE.
&&

$$

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


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