000
FXUS63 KIWX 070732
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
232 AM EST SAT DEC 7 2013

.SYNOPSIS...
ISSUED AT 215 PM EST FRI DEC 6 2013

LAKE EFFECT SNOW WILL END TODAY OVER LOWER MICHIGAN WITH DECREASING
CLOUDINESS. ANOTHER DISTURBANCE WILL RACE INTO THE REGION LATE
THIS WEEKEND...BRINGING A PERIOD OF LIGHT SNOW SUNDAY AFTERNOON.
HIGHS TODAY AND SUNDAY WILL BE IN THE 20S. LOWS TONIGHT WILL
MAINLY BE IN THE TEENS.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 409 PM EST FRI DEC 6 2013

HIGHLY ACTIVE/SERIAL SHORTWAVES CONTINUE WITHIN WRN PORTION OF
CANADIAN/WRN CONUS LONGWAVE TROF LEADING TO JAMES BAY CENTROID TO
SHEAR OUT ACRS SERN CANADA. POLAR VORTEX DIVES IN BEHIND TO REAFFIRM
NORTH CENTRAL CANADA TO INTERMOUNTAIN TROF AXIS BY F48. SLIGHT
LONGWAVE RIDGING INTO SRN GRTLKS/LWR OHIO VALLEY IN WAKE OF NEAR
TERM SHORTWAVE PASSAGE...AND THEREIN LIES THE RUB. EXTREMELY HIGH
ELEVATED FGEN RESPONSE WITHIN H6-5 LYR ON UPPER FRINGE OF SATURATION
LEVEL ASSOCD WITH MID DECK. DERISIVE DRYING WITHIN SUBCLOUD REGION
OF ARCTIC AIRMASS BELIES OTHERWISE IMPRESSIVE MID TROPOSPHERIC
DYNAMICS. FINELY HONED NORTHERN FRINGE OF COLUMN SATURATION...WHILST
EXHIBITING SOME INFLECTION NWD AMID VORTICITY CHANNEL CURRENTLY ACRS
LWR OHIO VALLEY...HAVING DIFFICULTY IN OVERCOMING MAGNITUDE OF DRY
AIR OFFSET. SHARP DISCOUNTENANCE BTWN P6SM TO IFR/LIFR VSBYS AT
BORDER WL RESULT IN SIMILARLY SHARP DELINEATION BTWN NO ACCUM TO 1
PLUS INCHES THIS EVENING...FALLING UPON PRIOR LATE NIGHT/EARLY AM
EPISODE. STILL SOME POTNL FOR LOW END ADVISORY CRITERIA AND EVENING
COMMUTE IMPACTS IN SOUTHEASTERN MOST COUNTIES OF PRIOR
ADV...SUGGESTS NON CONTIGUOUS CONTINUATION FOR JAY IN/ALLEN OH BEST
ROUTE FOR AFTN PACKAGE. ELSEWHERE MIDDLING LES THERMAL PROFILES WITH
DELTA T INTO THE MID TEENS WITH LK INDUCED CAPES AOB 200 J/KG AND
STRONGLY SUBSIDENT DRY AIR ABOVE 1-4KFT AGL LAYER SUGGESTS LESS THAN
STELLAR RESPONSE. COMBINED WITH DRY AIR ADVECTION INTO WRN LK
MICHIGAN SHORELINE PER SINGLE DIGIT SFC DPS INTO SERN WI ATTM...HAVE
SQUELCHED POP/ACCUMS/AREAL EXTENT ACRS FAR NWRN CWA AS WELL. CONTD
LOWRG OF TEMPS IN NEAR TERM...STRONGLY INFLUENCED BY 3 HRLY HIR RES
SHORT MODEL CONSENSUS AND BIAS NUDGE. SHARPER FALLS IN WRN CWA WHERE
MID DECK CLEARING TOWARD DAYBREAK APPEARS INEVITABLE...INTO SINGLE
DIGITS AS SEEN IN FAR ERN IA LAST NIGHT. LIKEWISE HAVE CAPPED
THERMAL RESPONSE ON SAT GIVEN STRENGTH OF SUBSIDENCE INVERSION AS
EXTREME ARCTIC RIDGE ACRS ALB/NRN ROCKY PLATEAU BEGINS TO ENVELOPE
THE WESTERN GREAT LAKES TO THE NORTHERN PLAINS.

&&

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 409 PM EST FRI DEC 6 2013

INITIAL CONCERN IS A SYSTEM WHICH WILL MOVE THROUGH THE AREA ON
SUNDAY. SLIGHTLY SLOWER MOVEMENT OF THIS SYSTEM AND SIGNIFICANT TOP
DOWN SATURATION NEEDED LED TO PUSHING DRY WEATHER BACK TO 18Z. MOST
OF THE SIGNIFICANT PRECIPITATION WITH THIS SYSTEM WILL SPLIT OUR
FORECAST AREA AS DEEPER MOISTURE/BETTER ISENTROPIC LIFT WILL REMAIN
SOUTHEAST OF THE AREA AND THE BETTER MID AND UPPER LEVEL SUPPORT
WILL REMAIN NW OF THE AREA. RAN POWT TOP DOWN WEATHER TOOL FOR
WEATHER GRIDS SUNDAY NIGHT THROUGH MONDAY MORNING WHICH GIVES
FREEZING DRIZZLE SUNDAY NIGHT AS THE 700 MB DRY SLOT EJECTS
OVERHEAD.

THIS SYSTEM EXITS OUR AREA BY MONDAY MORNING WHICH WILL ALLOW AN
ARCTIC AIRMASS TO POUR OUT OF SOUTHERN CANADA AND INTO THE GREAT
LAKES. THIS WILL TURN ON THE LAKE EFFECT MACHINE...ALTHOUGH WNW FLOW
WILL KEEP MOST LAKE EFFECT PRECIPITATION IN OUR MICHIGAN COUNTIES
(AT LEAST INITIALLY.) MOST FAVORABLE LAKE EFFECT TIME PERIOD WILL BE
FROM TUESDAY AFTERNOON AND INTO THE EARLY OVERNIGHT HOURS ON
WEDNESDAY BEFORE THE INVERSION HEIGHTS AND EQUILIBRIUM LEVEL LOWER.

SLIGHT WARMING TREND BY THE END OF THE WEEK AS THE ARCTIC TROUGH
FINALLY KICKS EAST OF OUR AREA...BUT THIS WONT LAST FOR LONG AS THE
NEXT ARCTIC SURGE IS POISED FOR SOMETIME NEXT WEEKEND.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 210 AM EST SAT DEC 7 2013

LOW LEVEL WINDS SHOULD BACK LATE OVERNIGHT THROUGH SATURDAY
MORNING...KEEPING LIGHT SNOW SHOWERS AND FLURRIES NORTH OF THE SBN
TERMINAL. HIGH PRESSURE SHOULD CONTINUE TO BUILD INTO THE
AREA...WITH DEEP LAYER SUBSIDENCE...HELPING TO CLEAR OUT CLOUDS
LATER TODAY. IN THIS REGARD...WENT A LITTLE OPTIMISTIC WITH THE
SCATTERING OUT OF THE MVFR LAKE CLOUDS...AT 19Z AT FWA AND 22Z AT
SBN...ALTHOUGH IT IS POSSIBLE LOW CLOUDS COULD LINGER A LITTLE
LONGER GIVEN MOISTURE TRAPPED UNDER THE BASE OF THE INVERSION.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR LMZ043-046.

&&

$$

SYNOPSIS...SKIPPER
SHORT TERM...MURPHY
LONG TERM...BENTLEY
AVIATION...SKIPPER


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

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