Area Forecast Discussion
Issued by NWS Northern Indiana

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KIWX 011755
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1255 PM EST SUN MAR 1 2015

.SYNOPSIS...
ISSUED AT 1254 PM EST SUN MAR 1 2015

SNOW WILL TAPER OFF THIS AFTERNOON ACROSS THE AREA WITH CLEARING
SKIES ARRIVING TONIGHT AS HIGH PRESSURE MOVES INTO THE REGION. HIGHS
TODAY AND MONDAY WILL BE IN THE UPPER 20S. LOWS TONIGHT WILL BE
AROUND 15 DEGREES.

&&

.UPDATE...
ISSUED AT 1241 PM EST SUN MAR 1 2015

FORECAST STILL ON TRACK WITH NO ADDITIONAL HEADLINES PLANNED AS
RADAR TRENDS SUGGEST SNOW FALL MAY BE STARTING TO WIND DOWN OVER
THE NEXT SEVERAL HOURS FROM WEST TO EAST.

RADAR TRENDS SHOWING A FEW BANDS OF MODERATE SNOWFALL ACROSS
NORTHERN INDIANA INTO NW OHIO. THUS FAR...HEAVIEST SNOW HAS
REMAINED NORTH OF AREAS IMPACTED EARLIER TODAY WITH AN ADDITIONAL
INCH OR SO SINCE THE LAST UPDATE. ONE OF THE BANDS SITTING OVER
THE OFFICE HAS PRODUCED SOME NICE DENDRITES AND DROPS VSBYS TO
AROUND A HALF MILE AT TIMES. OUTSIDE OF THE HEAVIER SNOW
SHOWERS...SOME THIN SPOTS IN THE CLOUDS HAVE ALLOWED THE SUN TO
PEAK OUT...INDICATING THAT MOISTURE WAS BEGINNING TO WANE
SOMEWHAT (TEMP NOW 25). TRENDS IN GRIDS REFLECT THIS ALREADY SO
SHOULD BE IN GOOD SHAPE. COORDINATED WITH KCLE ON ADVISORIES BEING
EXPANDED NORTH. WITH TRENDS SHOWING THE RAPID DECREASE AND
TEMPERATURES WARMING...WILL HOLD OFF ON ANY HEADLINES AND ISSUE
GENERIC SPS FOR THE AREA TO COVER THE HEAVIER SNOW SHOWERS.

&&

.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 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1241 PM EST SUN MAR 1 2015

VSBYS AT BOTH SITES HAVE BEEN HOVERING IN THE 1 TO 2 SM RANGE WITH
KSBN AS LOW AS 3/4SM. CIGS HAVE GENERALLY BEEN AROUND 2000 FT.
RADAR TRENDS SHOW OVERALL SPEED OF SNOW SHOWERS IS MOVING AT A
DECENT CLIP WITH SIGNS OF SNOW BEGINNING TO TAPER OFF IN EASTERN
ILLINOIS. HAVE ENDED SNOW A TOUCH FASTER AT BOTH SITES WITH MVFR
CIGS TO PERSIST INTO EARLY EVENING BEFORE CLEARING RAPIDLY ARRIVES
WITH VFR CONDITIONS THE REST OF THE PERIOD.

&&

.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.
&&

$$

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


VISIT US AT WWW.WEATHER.GOV/IWX (ALL LOWER CASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSNORTHERNINDIANA
WWW.TWITTER.COM/NWSIWX
WWW.YOUTUBE.COM/NWSNORTHERNINDIANA





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.