Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 190900
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
400 AM EST FRI DEC 19 2014

.SYNOPSIS...
ISSUED AT 1220 AM EST FRI DEC 19 2014

A WEAK TROUGH WILL BRING LIGHT SCATTERED SNOW SHOWERS AND PATCHY
DRIZZLE TO FAR NORTHERN INDIANA AND SOUTHERN MICHIGAN EARLY THIS
MORNING. OTHERWISE...A RIDGE OF HIGH PRESSURE WILL BRING DRY
CONDITIONS TO THE REGION THROUGH THE WEEKEND WITH NEAR SEASONABLE
TEMPERATURES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 355 AM EST FRI DEC 19 2014

WEAK SFC-850 MB TROUGH ACROSS SOUTHERN LOWER MI WILL BECOME
INCREASINGLY DIFFUSE INTO NRN IN/OH TODAY. THERE MAY BE JUST ENOUGH
LAKE ENHANCEMENT AND LOW LEVEL CONVERGENCE/MOISTURE TO FOCUS A FEW
FLURRIES OR PATCHY FREEZING DRIZZLE THROUGH MID MORNING MAINLY
ALONG/NORTH OF US 30. THIS COULD LEAD TO A FEW SLICK SPOTS EARLY
THIS MORNING. DRY/SEASONABLE OTHERWISE AS LOW AMPLITUDE SHORTWAVE
RIDGING OVERSPREADS IN ADVANCE OF A DISJOINTED HIGH PLAINS UPPER
TROUGH AXIS. THIS AND HIGH STATIC STABILITY THROUGH THE COLUMN WILL
HELP SFC HIGH PRESSURE BECOME MORE FIRMLY ESTABLISHED ACROSS THE
REGION INTO TONIGHT...WITH A BKN/OVC LOW CLOUD DECK LIKELY REMAINING
TRAPPED BENEATH A STUBBORN INVERSION FOR MOST LOCATIONS.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 355 AM EST FRI DEC 19 2014

NOT A LOT OF CHANGE IN THINKING HERE WITH RESPECT TO WINTER STORM
NEXT WEEK...BUT AS EXPECTED MODELS CONTINUE TO JUMP AROUND WITH
POTENTIAL SOLUTIONS. CONFIDENCE REMAINS HIGH ON A STRONG WINTER
STORM IN THE MIDWEST AND GREAT LAKES REGION BUT THE IMPORTANT
DETAILS ON STORM TRACK...PCPN TYPE AND SNOW AMOUNTS REMAIN QUITE
UNCERTAIN.

NORTHERN HEMISPHERIC WATER VAPOR LOOP FROM THE PAST WEEK TELLS THE
STORY OF DEVELOPING PATTERN CHANGE AND ORIGIN OF ENERGY FOR UPCOMING
WINTER STORM. POWERFUL 160-180KT JET ENERGY CURRENTLY OVER NORTHERN
PACIFIC HANDLED FAIRLY WELL BY MODEL INITIATIONS PER GOES HIGH
DENSITY WIND PLOTS. VAPOR LOOP SHOWS IMPRESSIVE MOISTURE PLUME
STRETCHING BACK TO EAST ASIA AND THE SOUTH PACIFIC. THIS PLUME HAS
BEEN ENERGIZED BY RECURVING TROPICAL DISTURBANCES FROM THE SOUTH
PACIFIC AS WELL AS THE INDIAN OCEAN. THIS HAS HELPED STRENGTHEN
NORTHERN PACIFIC JET WITH ENERGY SET TO RIDE INTO WESTERN CONUS THIS
WEEKEND AND INTO NORTHERN PLAINS EARLY NEXT WEEK. BUILDING RIDGES IN
BOTH THE WESTERN ATLANTIC AND ESPECIALLY EASTERN PACIFIC WILL HELP
THIS JET ENERGY FORM A CLOSED LOW SOMEWHERE OVER THE MIDWEST TO
GREAT LAKES REGION. THIS IS WHERE THE UNCERTAINTY IN DETAILS LIES AS
MEDIUM RANGE MODELS CONTINUE TO DIVERGE ON HOW AND WHERE THIS LOW
WILL FORM AND EVOLVE.

THE GENERAL SYNOPTIC IDEA REMAINS SIMILAR AMONG THE MODELS WITH MID
LEVEL LOW FORMING TO OUR WEST ACROSS THE PLAINS STATES SUNDAY INTO
MONDAY. SOUTHERLY LOW LEVEL JET WILL INCREASE AHEAD OF THIS LOW
MONDAY INTO TUESDAY ALLOWING DEEP MOISTURE TRANSPORT INTO OUR AREA.
THERMAL PROFILES WARM ENOUGH FOR MAINLY RAIN THROUGH TUESDAY. PWATS
AROUND THREE QUARTERS OF AN INCH BEING SHOWN BY MEDIUM RANGE MODELS
WHICH IS CLOSE TO BEING 2 STANDARD DEVIATIONS ABOVE NORMAL. THUS
SOME CONCERN GROWING WITH THIS LATEST MODEL RUN OF MODERATE TO HEAVY
RAINFALL RELATIVE TO MID DECEMBER. FORTUNATELY NO SNOW PACK TO WORRY
ABOUT AND RIVERS RUNNING NEAR NORMAL.

AS STORM DEEPENS AND TAKES ON A NEGATIVE TILT TUESDAY...SECONDARY
ENERGY IN BASE OF ELONGATED TROUGH BECOMES THE PROBLEMATIC FEATURE
FOR MODELS AND THE DETERMINING FACTOR FOR HOW MUCH SNOW WE WILL SEE
TUE NIGHT INTO WED. LATEST 00Z ECMWF AND GEM NOW REVERTING BACK TO
PREVIOUS SOLUTIONS WITH SECONDARY LOW FORMING IN MID MS VALLEY AND
MOVING NORTHEAST THROUGH WESTERN OH AS A PANHANDLE HOOK TYPE SCENARIO.
BOTH OF THESE MODELS HAVE A SUB 990MB LOW NOW OVER WESTERN OH BY 12Z
WED WITH POTENTIAL FOR DECENT SNOWFALL OVER PARTS OF THE CWA.
OPERATIONAL GFS IS SIMILAR BUT MUCH WEAKER WITH THIS SFC LOW.
MEANWHILE...PARALLEL GFS SHOWS A SIMILAR SOLUTION TO ECMWF/GEM BUT
TAKES THE LOW NORTH ALONG THE IN/IL STATE LINE WITH A 979MB SFC LOW
OVER LAKE MICHIGAN BY 12Z WED. OBVIOUSLY THIS WOULD GIVE US MUCH
LESS SNOWFALL. CONFIDENCE REMAINS LOW IN DETAILS FOR CHANGEOVER TO
SNOWFALL AND POTENTIAL AMOUNTS GIVEN THIS PLETHORA OF SOLUTIONS AND
MAIN PLAYERS STILL OVER THE DATA SPARSE NORTH PACIFIC. PAST
EXPERIENCE HAS SHOWN THAT THESE WINTER STORMS WITH A STRONG NEGATIVE
TILT TEND TO FAVOR A MORE WESTWARD SOLUTION.

WILL MAINTAIN CONSISTENCY WITH PREVIOUS FORECAST AND SURROUNDING
SITES USING SUPERBLEND INIT BUT GIVEN DECENT AGREEMENT ON
PRECIPITATION ACROSS THE AREA MONDAY NIGHT THROUGH TUESDAY NIGHT DID
NUDGE ENTIRE AREA INTO LIKELY POP CATEGORY FOR THESE PERIODS. ALSO
INCREASED SKY COVER AND WINDS. AS FOR PCPN TYPE...KEPT IT ALL RAIN
THROUGH TUESDAY AND LEFT TUE NIGHT AS RAIN OR SNOW GIVEN
UNCERTAINTY. BY WED THE STORM SHOULD BE OCCLUDING AND MOST LIKELY
NORTH OF US SO COLD AIR SHOULD BE WRAPPED AROUND AND IN PLACE GIVEN
ALL CURRENT SOLUTIONS. THUS HAVE ALL SNOW FOR WED AND WED NIGHT.
LAKE RESPONSE THEN LIKELY INTO CHRISTMAS DAY WITH WINDY CONDITIONS
OVER ENTIRE AREA. STRONG WINDS AND SHORT WNW FETCH OVER THE LAKE MAY
ACTUALLY BE A DETRIMENT TO LAKE EFFECT BUT STILL WORTHY OF CHANCE
POPS IN FAVORED NW AREAS.

NOT TO FORGET THE EARLY PART OF THE LONG TERM PERIOD BUT WEATHER
WILL BE BENIGN WITH A FEW SUBTLE SHORT WAVES. WEAK PV ANOMALY AND
SHORT WAVE ON SATURDAY MAY SQUEEZE OUT A FEW FLURRIES BUT MOISTURE
LACKING FOR ACCUMULATIONS. WARMING TREND INTO NEXT WEEK AHEAD OF
DEVELOPING STORM.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1220 AM EST FRI DEC 19 2014

WEAK SFC TROUGH NOW ACROSS FAR SOUTHERN LOWER MI WILL DROP INTO
NORTHERN IN THIS MORNING. THIS FEATURE AND SOME LAKE ENHANCEMENT
WILL LIKELY BRING A FEW SNOW SHOWERS AND POTENTIALLY PATCHY
FREEZING DRIZZLE TO MAINLY KSBN EARLY THIS MORNING. MAINLY
DRY/CLOUDY THEREAFTER AS TROUGH BECOMES INCREASINGLY DIFFUSE WITH
HIGH PRESSURE BECOMING BETTER ESTABLISHED. OTHERWISE...MVFR CIGS
EXPECTED TO PERSIST THROUGH MUCH OF THE PERIOD (MAY SEE BRIEF
IMPROVEMENT TO LOW VFR TOWARD MIDDAY/AFTERNOON) GIVEN RESIDUAL
MOISTURE UNDER LINGERING LOW LEVEL THERMAL INVERSION.

&&

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

$$

SYNOPSIS...STEINWEDEL
SHORT TERM...STEINWEDEL
LONG TERM...LASHLEY
AVIATION...STEINWEDEL


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