Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 291700
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1200 PM EST THU JAN 29 2015

.SYNOPSIS...
ISSUED AT 1159 AM EST THU JAN 29 2015

A SERIES OF UPPER LEVEL DISTURBANCES WILL TRACK ACROSS THE REGION
TODAY. LIGHT RAIN WILL MIX WITH AND THEN CHANGE TO ALL SNOW BY
LATE AFTERNOON AS COLDER AIR ARRIVES. A DUSTING OF SNOW IS
POSSIBLE IN A FEW SPOTS. EVEN COLDER AIR WILL FILTER INTO THE
REGION TONIGHT BEHIND A FRONTAL BOUNDARY. THIS WILL PROVIDE THE
POTENTIAL OF LIGHT SNOW ACCUMULATIONS WITH LAKE EFFECT SNOW
SHOWERS TONIGHT INTO EARLY FRIDAY ACROSS PORTIONS OF SOUTHWESTERN
LOWER MICHIGAN AND NORTHWESTERN INDIANA. STEADY OR SLOWLY FALLING
TEMPERATURES IN THE LOW TO MID 30S ARE EXPECTED THE REST OF THE
DAY. LOW TEMPERATURES TONIGHT WILL RANGE FROM THE MID TEENS TO
LOWER 20S.

&&

.UPDATE...
ISSUED AT 1143 AM EST THU JAN 29 2015

2 WAVES BEING WATCHED INTO THE AFTERNOON HOURS. FIRST WAS MOVING
ACROSS NORTHERN INDIANA WITH RAIN SHOWERS AHEAD OF IT AND A
MIXTURE OF RAIN OR SNOW SHOWERS BEHIND IT. SECOND STRONGER WAVE
WILL SWEEP ACROSS THE AREA MID AFTERNOON AND BRING A QUICK BURST
OF LGT SNOW TO MANY AREAS. LITTLE OR NO ACCUMULATIONS ARE
EXPECTED...BUT WITH FALLING TEMPERATURES SOME SLICK SPOTS MAY
REFORM ON UNTREATED ROADS.

DID INCREASE POPS THIS AFTERNOON AS SEVERAL HIGH RES MODELS
SUGGEST BIT MORE COVERAGE TO PRECIP THAN PREVIOUSLY DEPICTED WITH
UPSTREAM OBS AND RADAR DATA GIVING SOME CREDENCE TO THIS. BEHIND
THE LOW GUSTY WINDS WILL MOVE IN WITH STRONGEST GUSTS WITHIN THE
FIRST FEW HOURS OF THE SHIFT.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 421 AM EST THU JAN 29 2015

FORECAST CONCERN FOR THE SHORT TERM WILL CONTINUE TO CENTER ON
FREEZING RAIN CHANCES THIS MORNING...FOLLOWED BY POTENTIAL OF
CONTINUED LIGHT PRECIPITATION THROUGH THE DAY AND LAKE EFFECT SNOW
TONIGHT.

PRIMARY FORCING MECHANISM THROUGH MUCH OF THE OVERNIGHT HOURS HAS
BEEN A RELATIVELY NARROW ZONE OF MODERATE TO STRONG LOW/MID LEVEL
MOISTURE CONVERGENCE. THIS AXIS IS SHIFTING ACROSS EXTREME
NORTHEAST INDIANA AND SOUTH CENTRAL LOWER MICHIGAN AS OF 09Z. A
LIGHT GLAZE OF ICE ACCUMULATION WAS RECEIVED AT WFO IWX THIS MORNING
WITH THIS AXIS OF PRECIP. CURRENTLY EXPECTING THE BIGGEST CONCERNS
WILL PERSIST ACROSS EXTREME NORTHEAST INDIANA...FAR NORTHWEST
OHIO...AND SOUTH CENTRAL LOWER MICHIGAN THIS MORNING WHERE NEAR SFC
WARM ADVECTION IS WEAKER...AND NOT ABLE TO FULLY OFFSET EVAPORATIVE
COOLING EFFECTS. UP TO 0.05 INCHES OF ICE ACCUMULATION IS POSSIBLE
ACROSS ESPECIALLY NORTHEAST PORTIONS OF THE FREEZING RAIN ADVISORY
AREA. AFOREMENTIONED AXIS OF LOW/MID LEVEL MOISTURE CONVERGENCE
SHOULD BE FAIRLY PROGRESSIVE THROUGH NORTHWEST OHIO THROUGH 14Z
WHICH SHOULD MARK AN END TO ANY ADDITIONAL ICE ACCUMULATION. ONLY
WILDCARD FOR THIS FORECAST IS THE POTENTIAL OF UPSTREAM PV ANOMALY
ACROSS MID MS RIVER VALLEY TO IMPINGE ON THIS AXIS OF STRONGER
MOISTURE CONVERGENCE FORCING ACROSS NORTHWEST OHIO...WHICH COULD
YIELD AN INCREASE IN PRECIP COVERAGE/INTENSITY...ESPECIALLY
CONSIDERING THE APPROACH OF A PLUME OF VERY STEEP MID LEVEL LAPSE
RATES. FOR THIS REASON...HAVE CONTINUED TO HOLD THE EASTERN FREEZING
RAIN ADVISORY SEGMENT IN EFFECT UNTIL 10 AM EST...ALTHOUGH WILL
LIKELY BE ABLE TO CLEAR AT LEAST NORTHEAST INDIANA COUNTIES OVER THE
NEXT FEW HOURS. DID REMOVE A ST. JOSEPH INDIANA/WELLS/ADAMS COUNTY
FROM THE ADVISORY WITH SFC TEMPS HAVING RISEN ABOVE FREEZING.

FOR THE REMAINDER OF THE DAY...GUIDANCE STILL SUGGESTS POTENTIAL OF
PRECIP REDEVELOPING IN WEAK DEFORMATION/FGEN AXIS ACROSS NORTHWEST
PORTIONS OF THE AREA LATER THIS MORNING...AND SHIFTING ACROSS THE
REMAINDER OF THE AREA THIS AFTERNOON. IT DOES APPEAR AS THROUGH
LOCAL AREA MAY BE SITUATED BETWEEN THE MORE PRONOUNCED MID/UPPER
LEVEL WAVES THROUGH MOST OF THE AFTERNOON...LENDING TO SOME QUESTION
AS TO EXTENT OF MEASURABLE PRECIP IN THIS WEAK DEFORMATION AXIS.
HAVE MADE SOME SLIGHT DOWNWARD ADJUSTMENTS TO POPS BUT HAVE KEPT
GENERAL IDEA OF PREVIOUS FORECAST INTACT. THERMAL PROFILES SHOULD
SUPPORT MAINLY LIQUID FROM MID TO LATE MORNING ACROSS MOST OF THE
FORECAST AREA...WITH POSSIBLE EXCEPTION ACROSS THE FAR
NORTH/NORTHWEST WHERE SOME LIGHT SNOW/SLEET MAY MIX IN. SFC LOW
PRESSURE REACHING FAR SOUTHERN LAKE HURON THIS AFTERNOON WILL ALLOW
FOR ONSET OF MORE SIGNIFICANT COLD ADVECTION ACROSS ESPECIALLY
WESTERN/NORTHERN LOCATIONS WHERE A BRIEF PERIOD OF MAINLY LIGHT SNOW
IS POSSIBLE ON WESTERN PERIPHERY OF LIGHT DEFORMATION PRECIP.
MARGINAL THERMO PROFILES/LOW LEVEL WET BULBS SUGGEST LITTLE OR NO
SNOW ACCUMULATION HOWEVER. PRESSURE RISE BUBBLE WORKING ACROSS
SOUTHERN IOWA IS EXPECTED TO ENTER THE AREA THIS AFTERNOON...WHICH
SHOULD YIELD SOME WEST NORTHWEST GUSTS TO 20 TO 30 MPH ACCOMPANYING
THE LOW LEVEL CAA.

FOR TONIGHT...LAKE EFFECT/ENHANCED SNOW SHOWERS SHOULD DEVELOP EARLY
THIS EVENING AS WEAK SYNOPTIC UPPER WAVE TRACKS ACROSS THE SOUTHERN
GREAT LAKES. A MORE VIGOROUS WAVE DROPPING OUT OF SOUTH CENTRAL
CANADA WILL BRING MORE PRONOUNCED LOW LEVEL CAA AND INCREASING LAKE
EFFECT CHANCES DURING THE OVERNIGHT HOURS. RELATIVELY DRY MID LEVELS
AND SHALLOW INSTABILITY PROFILES CONTINUE TO SUGGEST MINOR SNOW
ACCUMS OF AN INCH OR TWO POSSIBLE FOR NORTHWEST FETCH LAKE EFFECT
AREAS.

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 421 AM EST THU JAN 29 2015

LAKE EFFECT SNOW WILL GRADUALLY WIND DOWN DURING THE DAY FRIDAY.
INCREASING SUBSIDENCE/LOWERING INVERSION...BACKING WINDS...AND DRY
AIR ENTRAINMENT WILL TAKE AN INCREASING TOLL ON LAKE INDUCED
CONVECTION. ACCUMULATING SNOW WILL PROBABLY END BY MIDDAY WITH JUST
SOME RESIDUAL FLURRIES POSSIBLE ACROSS BERRIEN AND CASS COUNTIES
DURING THE AFTERNOON AS LOW LEVEL WINDS BACK TO A MORE WESTERLY
DIRECTION. HIGH TEMPS WILL BE ON THE COOL SIDE WITH THERMAL TROUGH
STILL IN PLACE BUT NOTHING OUT OF THE ORDINARY FOR LATE JANUARY.
EXPECT HIGHS GENERALLY IN THE MID 20S. W/SW LOW LEVEL FLOW DEVELOPS
BY FRIDAY NIGHT AND SATURDAY...ADVECTING SLIGHTLY WARMER AIR INTO
THE REGION AHEAD OF NEXT APPROACHING TROUGH. RAISED HIGHS A BIT TO
BE MORE IN LINE WITH LATEST MOS GUIDANCE. SHOULD MAKE A RUN AT LOWER
30S IN MOST LOCATIONS AFTER OVERNIGHT LOWS IN THE MID TO UPPER TEENS.

ATTENTION THEN TURNS TO POTENTIAL SNOW ON SUNDAY. AS EXPECTED...
DETERMINISTIC MODELS HAVE STRUGGLED IMMENSELY WITH THE EVOLUTION OF
THIS SYSTEM. RUN TO RUN VARIABILITY AND INTERMODEL DISAGREEMENT HAS
BEEN VERY HIGH. THIS IS NOT SURPRISING GIVEN THE EVENT IS PREDICATED
ON A RATHER COMPLEX INTERACTION BETWEEN MULTIPLE JET STREAKS AND
SHORTWAVES THAT HAVE NOT EVEN DEVELOPED YET. GFS ENSEMBLE MEMBERS
STILL SHOW A HIGH DEGREE OF SPREAD AND CONFIDENCE REMAINS VERY LOW.
00Z OPERATIONAL GFS TRENDED A BIT FURTHER NORTH BUT STILL KEEPS BULK
OF THE PRECIP SOUTH OF OUR CWA. LATEST GEM AND NAM EXTRAPOLATION
SUGGEST A STRONGER AND FURTHER NORTH SOLUTION WHILE THE ECMWF
REMAINS THE MOST SUBDUED. WILL LARGELY STAY THE COURSE WITH THIS
FORECAST PACKAGE. STILL MAINTAIN A BETTER THAN 50/50 SHOT OF
MEASURABLE SNOW BASED ON STRENGTH AND PLACEMENT OF UPPER LEVEL JET
SEEN IN ALL OF THE LATEST DETERMINISTIC MODELS...ESPECIALLY THE
FURTHER SOUTH YOU GO. CONFIDENCE IN EXACT AMOUNTS AND LOCATION
REMAIN VERY LOW HOWEVER. STAY TUNED TO THE LATEST FORECASTS OVER THE
NEXT DAY OR TWO AS THE SOLUTION SPACE SHOULD GRADUALLY NARROW.

MUCH COLDER AIR STILL EXPECTED EARLY NEXT WEEK AS 850MB TEMPS DROP
TO AROUND -20C. THIS SHOULD KEEP MONDAY`S HIGHS IN THE TEENS WITH
LOWS SUNDAY AND MONDAY NIGHT IN THE SINGLE DIGITS. BRIEF WARM UP
SEEN ON TUESDAY IN WAA REGIME AHEAD OF ANOTHER CLIPPER SYSTEM BUT
ANOTHER...POSSIBLY COLDER...ARCTIC SURGE IS POSSIBLE FOR THE MIDDLE
AND END OF NEXT WEEK. VERY HIGH AMPLITUDE RIDGE IS SHOWN TO DEVELOP
OVER WESTERN NOAM WITH PERSISTENT TROUGHING OVER EASTERN CANADA
YIELDING VERY COLD N/NW FLOW FOR THE GREAT LAKES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1143 AM EST THU JAN 29 2015

WINDS HAVE COME AROUND TO NW AT KSBN AND WILL REMAIN ON THE GUSTY
SIDE INTO THIS EVENING. EXPANSIVE STRATUS DECK WILL CONTINUE TO
MOVE IN WITH CIGS HOVERING IN THE 800 TO 1200 FT RANGE THROUGH
MUCH OF THE PERIOD. PERIODS OF SNOW SHOWERS WILL BECOME MORE
LIKELY WITH TIME AS WE MOVE INTO THE LATE AFTERNOON
HOURS...CONTINUING THROUGH THE NIGHT.

AT KFWA...WINDS SHOULD BECOME NW CLOSE TO OR JUST AFTER VALID TIME
OF TAFS WITH SOME LIGHT RAIN/SNOW INTO LATE AFTERNOON ALONG WITH
GUSTY WINDS. CIGS WILL REMAIN AROUND 1000 FT MUCH OF THE PERIOD AS
WELL.

&&

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

$$

UPDATE...FISHER
SYNOPSIS...FISHER
SHORT TERM...MARSILI
LONG TERM...AGD
AVIATION...FISHER


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