Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 270119
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
819 PM EST THU FEB 26 2015

.SYNOPSIS...
ISSUED AT 351 PM EST THU FEB 26 2015

HIGH PRESSURE BUILDING SOUTHEAST FROM THE NORTHERN PLAINS WILL
RESULT IN GENERALLY DRY AND COLD CONDITIONS TONIGHT AND FRIDAY.
THE ONLY EXCEPTION TO THE DRY WEATHER WILL BE NEAR LAKE MICHIGAN
WHERE LAKE EFFECT SNOW SHOWERS ARE EXPECTED TO CAUSE LOCALIZED
REDUCED VISIBILITIES AND MINOR SNOW ACCUMULATION TONIGHT. LOWS
TONIGHT WILL GENERALLY RANGE FROM -4 TO -8... WITH HIGHS FRIDAY IN
THE TEENS.

&&

.UPDATE...
ISSUED AT 815 PM EST THU FEB 26 2015

A VERY SUBTLE LOW AMPLITUDE MID LEVEL SHORT WAVE TRACKING WILL
CONTINUE TO TRACK ACROSS NORTH CENTRAL/NORTHEAST INDIANA THIS
EVENING. SOME UNCERTAINTY REMAINS REGARDING INTENSITY OF LAKE
EFFECT SNOW SHOWERS OVERNIGHT WITH SOME MID LEVEL DRY AIR
ADVECTION IN THE WAKE OF THIS SHORT WAVE. SOME EASTWARD PUSH OVER
THE PAST FEW HOURS OF MORE SUBSTANTIAL LAKE EFFECT SNOW SHOWERS
ACROSS NORTHWEST LA PORTE AND SOUTHWEST BERRIEN COUNTIES...IN PART
POSSIBLY AIDED DUE TO PASSAGE OF THE WEAK MID LEVEL TROUGH. NOT
EXPECTING LAKE EFFECT SNOW SHOWERS TO MAKE MUCH MORE EASTWARD
TONIGHT DUE TO EXPECTATION OF LAND BREEZE DEVELOPMENT. MEAN LAKE
AGGREGATE TROUGHING SHOULD ANCHOR BEST COVERAGE OF LAKE EFFECT
SNOW SHOWERS ACROSS SOUTHWEST BERRIEN/NORTHERN LA PORTE THROUGH
THE OVERNIGHT HOURS. INVERSION HEIGHTS/LAKE INDUCED EQUILIBRIUM
LEVELS ARE EXPECTED TO REMAIN RELATIVELY STABLE OVERNIGHT...BUT
MORE OF A MAINTAINED FETCH AND PERSISTENCE OF LAKE AGGREGRATE
TROUGHING THROUGH THE EARLY PORTIONS OF THE OVERNIGHT HOURS COULD
BE CONDUCIVE FOR ACCUMS IN THE 1-3 OR 2-4" RANGE ACROSS EXTREME
SOUTHWEST BERRIEN/NORTHERN LA PORTE COUNTIES...WITH LOCALLY HIGHER
AMOUNTS NOT OUT OF THE QUESTION. MAIN LIMITING FACTOR WILL BE
MODEST MID LEVEL DEW POINT DEPRESSIONS AND ENTRAINMENT OF DRIER
LOW LEVEL AIR. WILL CONTINUE TO MONITOR EVOLUTION FOR POSSIBLE
LAKE EFFECT SNOW ADVISORY HEADLINES...BUT CURRENTLY NO IMMEDIATE
HEADLINE PLANS. BY LATE TONIGHT...WEAKENING WIND FIELD AND
MATURATION OF LAND BREEZE SHOULD TEND TO CONSTRICT INLAND
PENETRATION OF LAKE EFFECT SNOW SHOWERS...WITH EVENTUAL FOCUS FOR
HEAVIER SNOW SHOWERS SHIFTING OFFSHORE.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 335 PM EST THU FEB 26 2015

STRONG HIGH PRESSURE SYSTEM OVER THE NRN PLAINS WILL MOVE SOUTHEAST
INTO THE MIDWEST DURING THIS PERIOD PROVIDING DRY WX WITH CONTD
ABNORMALLY COLD TEMPERATURES. ONLY EXCEPTION TO THE DRY WX SHOULD BE
FAR NW PORTION OF THE CWA WHICH NAM/NMM SUGGEST WILL BE IMPACTED BY
SINGLE BAND CURRENTLY EXTENDING NNE FROM CHICAGO. NEGATIVES FOR
SGFNT ACCUMS IN OUR AREA INCLUDE INVERSION HEIGHT BLO 5KFT AND DRY
ARCTIC AIRMASS ADVECTING IN WITH DWPTS UPSTREAM WELL BLO ZERO. ALSO
PER ARW AND IWX LOCAL WRF... WKNG GRADIENT OVERNIGHT WILL ALSO
RESULT IN LAND BREEZE DEVELOPMENT WHICH SHOULD LIMIT EASTWARD
MIGRATION OF THE SINGLE BAND...KEEPING HEAVIEST AMOUNTS TO OUR WEST
AND OFFSHORE. FCST ACCUMS IN THE 1-3" RANGE ACROSS NRN LAPORTE/SWRN
BERRIEN COUNTIES... BUT AS WITH ANY SINGLE BAND... THERE IS A
POTENTIAL FOR SOME HEAVY SNOWFALL RATES SO WILL NEED TO MONITOR
CLOSELY. OTRWS LIGHT GRADIENT AND DECREASING CLOUDINESS SHOULD
PROVIDE GOOD RADIATIONAL COOLING OVERNIGHT. CURRENT FCST MINS
GENERALLY A LITTLE BLO 12Z GUIDANCE AND ONLY MINOR CHANGES MADE WITH
LOWS 0F TO -10F...COLDEST NE AND WARMEST NEAR THE LAKE. DECOUPLING
BOUNDARY LAYER SHOULD RESULT IN LIGHT WINDS... ESPECIALLY LATE
TONIGHT... SO STILL EXPECT WIND CHILL VALUES TO GENERALLY STAY ABOVE
ADVISORY CRITERIA (-15F)... BUT SHOULD BE CLOSE.

LOW LEVEL FLOW WILL BACK W-SW FRIDAY AS ARCTIC HIGH MOVES INTO
CENTRAL IL/IN. LOWERING INVERSION AND CONTD DRY AIR ADVECTION SHOULD
LIMIT LAKE EFFECT TO JUST A FEW FLURRIES ACROSS SW MICHIGAN. LOW
LEVEL THERMAL TROF WILL LINGER OVER THE CWA MUCH OF THE DAY... SO
DESPITE PLENTIFUL SUNSHINE AND WINDS BACKING TO SWLY... EXPECT HIGH
TEMPS ONLY IN THE TEENS.

&&

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 335 PM EST THU FEB 26 2015

.LONG TERM...

...SIGNS OF A BRIEF WARM UP NEXT WEEK...BUT MAY BE A ROCKY ROAD TO
GET THERE...

FORECAST PERIOD WILL START OUT DRY AND QUIET...BUT WELL BELOW NORMAL
AS HIGH PRESSURE DRIFTS ACROSS THE REGION INTO SATURDAY. ONE MORE
BITTERLY COLD NIGHT IN STORE FRIDAY NIGHT WITH TEMPS LIKELY BELOW
ZERO ACROSS THE AREA WARMING INTO THE TEENS ON SATURDAY.

EXTENDED PERIOD OF INCREASED LIFT AND MOISTURE ADVECTION SATURDAY
NIGHT INTO SUNDAY WILL SET THE STAGE FOR ACCUMULATING SNOWFALL
ACROSS THE AREA. MODELS HAVE BEGUN TO CONVERGE SOMEWHAT ON GENERAL
QUARTER TO HALF INCH OF QPF WHICH WOULD TRANSLATE TO 4 TO 6 INCH
ACCUMULATIONS OVER A 24 TO 36 HOUR PERIOD USING CLIMO SNOW RATIOS OF
13:1 HAVE INCREASED POPS TO CATEGORICAL ACROSS SE HALF OR SO AND
HIGH LIKELY NW GIVEN CONVERGENCE OF SOLUTIONS AND HIGHER CONFIDENCE.
NOT ANTICIPATING MUCH IN THE WAY OF WIND CONCERNS...BUT GIVEN
EXPECTED AMOUNTS...WINTER WEATHER ADVISORY WILL LIKELY BE NEEDED IN
LATER FORECASTS FOR PART OR ALL OF THE AREA.

TROUGH WILL REMAIN PROGRESSIVE AND QUICKLY EXIT THE REGION BY MONDAY
MORNING WITH ZONAL FLOW STILL IN PLACE. THIS WILL KEEP ANY ARCTIC
INTRUSIONS BOTTLED UP FURTHER NORTH FOR THE MOMENT...BUT DON`T GET
YOUR HOPES UP ON NO MORE BLASTS OF COLD AIR AS SIGNIFICANT TROUGHING
WILL TAKE PLACE OVER THE SW STATES INTO THE MIDDLE OF NEXT WEEK.
THIS WILL BRING A PERIOD OF WARMER TEMPERATURES (NEAR OR ABOVE
NORMAL) IN THE TUES TO WEDS TIME FRAME. HOWEVER...IT MAY COME AT A
COST AS POTENTIAL STILL EXISTS FOR A PERIOD OF FREEZING RAIN LATE
MONDAY NIGHT INTO TUES MORNING IN OVERRUNNING SCENARIO AHEAD OF A
NORTHWARD MOVING WARM FRONT. GFS/ECMWF HAVE LINED UP ON TRACK OF SFC
FEATURES FROM ROUGHLY MILWAUKEE TO ALPENA. HOWEVER...NEW ECMWF HAS
BACKED OFF CONSIDERABLY ON TIMING OF SYSTEM WITH PRECIP NOT ARRIVING
TILL TUESDAY AFTERNOON. HAVE DISMISSED FOR THE TIME BEING GIVEN
AMOUNT OF DYNAMICS IN PLACE WITH WARM FRONT AND OVERRUNNING SETUP.
THAT BEING SAID...HELD OFF ON TRENDS OF SOME SURROUNDING OFFICES OF
CATEGORICAL POPS FOR THE TIME BEING. DID TRENDS HIGHS TUESDAY WARMER
WITH EVERYONE ABOVE FREEZING ON TUESDAY AND HINTS OF TEMPS WELL INTO
THE MID 40S (ECMWF EVEN HINTING AT 50S BY LATE TUESDAY NIGHT).

ONCE THE TROUGH EXITS THE AREA...COLDER AIR WILL RUSH BACK IN AND
WHATEVER MAY HAVE MELTED WILL REFREEZE BY THURSDAY AND INTO THE
WEEKEND WITH POTENTIAL FOR LAKE EFFECT SNOWFALL. HAVE TRIMMED POPS
BACK ON SUPERBLEND IN LATER PERIODS THAT WERE A BIT OVERZEALOUS AT
THIS STAGE OF THE GAME.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 650 PM EST THU FEB 26 2015

MAINLY VFR CONDITIONS ARE EXPECTED THIS PERIOD. NORTH WINDS AROUND
10 KNOTS TO BEGIN THE PERIOD WILL DIMINISH IN SPEED THIS EVENING
AND BECOME LIGHT AND VARIABLE OR LIGHT WESTERLY OVERNIGHT.
GENERALLY VFR STRATOCU IS ANTICIPATED...ALTHOUGH CANNOT COMPLETELY
RULE OUT SOME HIGHER END MVFR CIGS TONIGHT. LAKE EFFECT SNOW
SHOWERS ARE NOT EXPECTED TO BE A BIG CONCERN FOR KSBN
TONIGHT...WITH CONDITIONS FAVORING DOMINANT BANDING TO REMAIN WEST
OF THE TERMINAL. CENTER OF SURFACE ANTICYCLONE TO REMAIN SOUTH OF
THE TERMINALS FROM SOUTHEAST IOWA INTO CENTRAL ILLINOIS FRIDAY
AFTERNOON...PROMOTING A LIGHT WESTERLY GRADIENT WITH SPEEDS OF 10
KNOTS OR LESS.


&&

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

$$

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


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