Area Forecast Discussion
Issued by NWS Northern Indiana

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837
FXUS63 KIWX 091006
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
506 AM EST TUE FEB 9 2016

.SYNOPSIS...
ISSUED AT 459 AM EST TUE FEB 9 2016

LAKE EFFECT SNOW SHOWERS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY LATER TODAY AND ESPECIALLY TONIGHT INTO THURSDAY
MORNING. WHILE MOST LOCATIONS SHOULD SEE AT LEAST SOME MEASURABLE
SNOWFALL DURING THIS PERIOD...THE HIGHEST AMOUNTS AND GREATEST
IMPACTS WILL LIKELY BE CONFINED TO THE FAVORED LAKE EFFECT REGION
OF FAR NORTHERN INDIANA AND SOUTHWESTERN LOWER MICHIGAN.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 459 AM EST TUE FEB 9 2016

MULTIPLEX MID/ULVL VORTEX HAS BEEN SLOW TO DEPART WITH STRONG NOAM
BLOCK AND MULTITUDE OF STRONG DIGS OF UPSTREAM ENERGY. UNTIL
OFFSHORE NEW ENGLAND COASTAL STORM LIFTS NNEWD INTO MARITIMES AND
FINAL 160KT UPSTREAM 3H JETLET OVER SASK DIVES DIVES SWD INTO IA
THIS EVENING THE OVERALL STACKED SYSTEM THERMODYNAMICS TO PROVE
DISFAVORABLE FOR LES. STILL MORE SYNOPTICALLY DRIVEN SHSN WITH DEEP
MOISTURE TO 15KFT TO CONTINUE TODAY. WILL CONTINUE TO COVER
SUBADVISORY HAZARDS DUE TO LIGHT SNOW ACCUMS/GROUND ICE WITH SPS
PRODUCT AS NEEDED. BY LATE AFTERNOON/EVENING WILL HAVE RAPID ARRIVAL
OF 8H COLD POOL CURRENTLY IN HOLDING PATTERN ACROSS NWRN WI/FAR WRN
LK SUPR WITHIN CONGESTED FLOW. OUTPUT FROM 1.33KM/HIGH IMPACT NAM
NEST FURTHER CONFIRMS MORE GENERAL CONCEPTUAL AND OTHER
NAM/MULTICOBB MODEL SUGGESTIONS AND POINT TO 21 UTC TUE FOR START OF
A MORE COHESIVE LES EVENT AND START TIME FOR WINTER WX ADVISORY FOR
LES. PER HIGH RES OUTPUT...INITIAL PRIMARY BAND FORMATION ACRS SRN
LAKE MI INTO BERRIEN/NERN LAPORTE LATE AFTERNOON/EVE. THEREAFTER A
SECONDARY MORE NORTHWARD CONVECTIVE ROLL/LES BAND FORMS WHILE A
THIRD BAND FORMS CLOSER TO EAST CENTRAL LAKE MICHIGAN SHORELINE AND
DROPS SOUTH TAKING ON A KLUD TO NRN ST. JOE MI COUNTY TARGET.
REGARDLESS OF ACTUAL EVOLUTION INTENSITY OF/CONVECTIVE
DEPTH/SUPERSATURATION WITHIN 3KFT DGZ SHOULD LEAD TO BRIEFLY PEAKED
SNOWFALL RATES OF ONE TO TWO INCHES PER HOUR LATE TONIGHT INTO EARLY
WED WITH BEST INGREDIENTS OVERLAP AND DELTA T TO 20C. THEREAFTER AS
LOWER PART OF DGZ GOES SUBCLOUD RATES TO DIMINISH. STILL SLOW
DISINTEGRATION OF LES AGGREGATE TROF AND NEAR STEADY STATE LAKE
INDUCED PARAMETERS OF 350-400 J/KG AND 6-7KFT EQL TO MAINTAIN A
PROLONGED EVENT FOR REMAINDER OF WED INTO THU AM. TARGETED PATCHY
BLOWING SNOW IN HEART OF HIGHEST EXPECT ACCUMS TONIGHT AND WED.
THEREAFTER RATES AND SFC WIND SPEEDS SHOULD GREATLY LESSEN
OCCURRENCE. LARGELY OWING TO THE LACK OF A DEEPER DGZ AND DOWNTREND
IN MULTIMODEL AVERAGED COBB METHOD SNOW AMOUNTS HAVE TEMPERED
AMOUNTS OVER PRIOR SOMEWHAT. LONGEVITY OF EVENT SHOULD LEAD TO 6 TO
12 INCHES ESPECIALLY IN BERRIEN/WRN CASS COUNTIES MICHIGAN AND ST.
JOE AND EXTREME NERN LAPORTE COUNTIES INDIANA. MIN WIND CHILLS 5 BLO
TO 5 ABV TONIGHT THROUGH END OF ADVISORY ADDS ADDITIONAL HAZARD.

&&

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 459 AM EST TUE FEB 9 2016

LAKE EFFECT SNOW SHOWERS SHOULD DIMINISH AS INVERSION
HEIGHTS LOWER AND WINDS BACK IN RESPONSE TO THE NEXT WAVE
RAPIDLY MOVING SE TOWARDS THE REGION. LIGHT ACCUMULATIONS MAY BE IN
STORE DURING THE DAY FRIDAY WITH TRANSITION BACK TO LAKE EFFECT SNOW
SHOWERS FRIDAY NIGHT.

MORE PRONOUNCED LAKE RESPONSE WILL LIKELY TAKE PLACE SATURDAY INTO
MONDAY AS ARCTIC LOW DROPS INTO NEW ENGLAND FOR THE WEEKEND AND
SENDS TEMPERATURES PLUMMETING ACROSS THE AREA. MODELS NOW SEEM TO BE
IN AGREEMENT ON BULK OF COLDEST AIR STAYING EAST OF HERE, BUT STILL
PLENTY LOW ENOUGH TO END UP WITH HIGHS IN THE LOW TO MID TEENS FOR
SATURDAY. POTENTIAL EXISTS FOR ACCUMULATING SNOWFALL AGAIN ACROSS
THE AREA...BUT GIVEN CONCERNS AS TO EXACTLY HOW MOISTURE PROFILES
AND TRAJECTORIES WILL SET UP...LITTLE MORE THAN CHC POPS WARRANTED.

WITH TRENDS BEING FURTHER EAST WITH THE COLDER AIR...MOS GUIDANCE
HAS TRIED TO INCREASE TEMPERATURES SEVERAL DEGREES. HAVE WENT WITH
BLEND OF PREVIOUS FORECAST AND NEW SUPERBLEND DATA TO HOLD DOWN
MASSIVE CHANGES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1239 AM EST TUE FEB 9 2016

DIFFICULT TAFS THROUGH THE PERIOD ESPECIALLY AT KSBN AS EXACT
LAYOUT OF FORECASTED LAKE EFFECT SNOW BANDS THROUGH THE PERIOD
WILL CAUSE HIGHLY VARIABLE CONDITIONS. CONFIDENCE HIGH IN SNOW
SHOWERS OCCURRING WITH IMPACTS BUT CONFIDENCE LOW TO MEDIUM ON
PLACEMENT OF BANDS WITH RELATION TO TAF SITES.

ONE BAND WAS MOVING EAST OF KBEH AND BASED ON ESE TRAJECTORY MAY
BYPASS KSBN ENTIRELY. HOWEVER HIGH RES MODELS INDICATE SOME
EXPANSION IN COVERAGE IS POSSIBLE BETWEEN 6 AND 12Z TUES. HAVE
TONED DOWN TAFS IN THAT PERIOD AND WILL MONITOR TRENDS. KFWA
SHOULD SEE LITTLE MORE THAN FLURRIES OR LIGHT SNOW SHOWERS WITH
MAINLY MVFR CIGS TO DEAL WITH.

A LULL IN SNOW SHOWERS APPEARS LIKELY AFTER 14Z TUES THROUGH AT
LEAST 00Z WEDS AS DEEPER MOISTURE AND LIFT BRIEFLY WANE.
HOWEVER...LAKE EFFECT SHOULD KICK IN FAIRLY QUICKLY AFTER 00Z WITH
GREATEST IMPACTS BEING SEEN AT KSBN AFTER 2Z AND PERSISTING WELL
THROUGH THE VALID PERIOD. AT KFWA...HAVE KEPT LITTLE MORE THAN
FLURRY MENTION AFTER 14Z WITH TEMPO GROUP TOWARDS THE END OF THE
PERIOD TO HANDLE POTENTIAL FOR LAKE EFFECT SNOW SHOWERS BEGINNING
TO MOVE SE TOWARDS THE SITE.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY FROM 4 PM EST /3 PM CST/ THIS AFTERNOON
     TO 10 AM EST /9 AM CST/ THURSDAY FOR INZ003>005.

MI...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM EST
     THURSDAY FOR MIZ077>079.

OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 10 AM EST THURSDAY FOR LMZ043-046.

&&

$$

SYNOPSIS...FISHER
SHORT TERM...MURPHY
LONG TERM...FISHER
AVIATION...FISHER


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