Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 250905
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
405 AM EST WED FEB 25 2015

.SYNOPSIS...
ISSUED AT 405 AM EST WED FEB 25 2015

DRY CONDITIONS EXPECTED TODAY...AHEAD OF ANOTHER WEAK SYSTEM
CROSSING THE REGION TONIGHT. THIS SYSTEM WILL GENERATE SOME LIGHT
SNOW LATE TONIGHT INTO TOMORROW BUT ACCUMULATIONS WILL BE LESS
THAN AN INCH. HIGHS TODAY WILL BE IN THE LOWER 20S WITH LOWS
TONIGHT AROUND 10 DEGREES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 405 AM EST WED FEB 25 2015

QUIET WEATHER ANTICIPATED TODAY WITH JUST SOME VERY LIGHT SNOW
ARRIVING LATER TONIGHT. SURFACE RIDGE CURRENTLY BUILDING IN BEHIND
EXITING COLD FRONT. A FEW POSTFRONTAL LAKE EFFECT FLURRIES IN OUR
NORTHWEST COUNTIES EARLY THIS MORNING BUT NO ACCUMULATION/IMPACT
EXPECTED GIVEN VERY STRONG DRY AIR ADVECTION (SEE 00Z KGRB SOUNDING)
AND LIMITED INSTABILITY. SURFACE WINDS VEER TO MORE NORTHEASTERLY
DIRECTION BY LATE MORNING AND WILL SHUT OFF ANY REMAINING FLURRIES.
CALENDAR DAY HIGHS HAVE ALREADY BEEN REACHED WITH DAYTIME TEMPS
REMAINING IN THE UPPER TEENS TO LOWER 20S UNDER STRONG PUSH OF LOW
LEVEL CAA AND INCREASING MIDLEVEL CLOUDS.

NEXT SHORTWAVE TO IMPACT OUR AREA IS CURRENTLY ENTERING THE NORTHERN
PLAINS AND WILL SWING THROUGH OUR REGION BY LATE TONIGHT.
HOWEVER...CONFLUENT MID/UPPER LEVEL FLOW WILL SHEAR OUT THIS ALREADY
LACKLUSTER WAVE BY THE TIME IT REACHES US. 285K ISENTROPIC ASCENT
WASHES OUT WEST OF OUR AREA AND THE ACTUAL SURFACE LOW IS ABSORBED
BY SOUTHEAST CONUS SYSTEM. JUST SOME WEAK CVA AND ELEVATED
DEFORMATION/FGEN TO SPREAD LIGHT SNOW OVER OUR CWA. LOW LEVEL
MOISTURE ADVECTION IS ALSO LIMITED GIVEN N/NE FLOW. FORECAST
SOUNDINGS DO SHOW A VERY DEEP DENDRITIC GROWTH ZONE AND RELATIVELY
LIGHT WINDS THAT COULD LEAD TO SOME DECENT SIZED FLAKES AND HIGHER
SNOW RATIOS BUT BEST OMEGA/SUPERSATURATION WRT ICE IS MAINLY ABOVE
THE DGZ AND WILL INTRODUCE A FAIR AMOUNT OF PLATES AND COLUMNS. DID
RAISE POPS SLIGHTLY OUT OF RESPECT FOR THE 700MB FORCING BUT ANY
ACCUMULATIONS WILL BE LESS THAN A HALF INCH. OVERNIGHT TEMPS
EXPECTED TO HOLD AROUND 10F GIVEN INCREASING CLOUDS/PRECIP.

&&

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 405 AM EST WED FEB 25 2015

SNOW CHANCES WEDNESDAY NIGHT/THURSDAY AND AGAIN ON SUNDAY INTO
MONDAY...ALONG WITH ANOTHER BLAST OF ARCTIC TEMPERATURES IN
BETWEEN...REMAINS THE FOCUS OF THE LONG TERM PERIOD.

POTENT BUT SHEARING NORTHERN STREAM WAVE WILL BE DIVING EAST
SOUTHEAST THROUGH THE GREAT LAKES LATE WEDNESDAY NIGHT AND THURSDAY.
LIGHT SNOW WILL OVERSPREAD THE AREA EARLY THURSDAY MORNING.
CONTINUED TREND FOR WARMER MIN TEMPS WEDNESDAY NIGHT W/ RAPID
INCREASE IN CLOUD COVER EXPECTED. WEAK FORCING/ASCENT AND INITIAL
DRY LAYER CENTERED AROUND 850MB WILL YIELD LITTLE MORE THAN FLURRIES
INTO THE EARLY PART OF THE OVERNIGHT...HOWEVER NOTED AN OVERALL
FASTER TREND WITH ONSET OF PRECIP/SHEARING WAVE PASSAGE. SUBTLE
HEIGHT FALLS AND OVERALL WEAKER ASCENT SHOULD KEEP SNOW LIGHT
THROUGH THE DAY...AS SYSTEM EXITS EAST OUT OF THE AREA DURING THE
AFTERNOON INTO EVENING HOURS. FORECAST SNOW AMOUNTS ARE GENERALLY
LESS THAN AN INCH THROUGH THIS PERIOD.

YET ANOTHER ARCTIC INTRUSION IS EXPECTED THURSDAY NIGHT AS
SFC HIGH CENTER SLIDES SOUTHEAST ALONG THE LEE OF THE NORTHERN
ROCKIES INTO THE GREAT LAKES/OHIO VALLEY BY FRIDAY NIGHT. 850MB
TEMPS DROPPING TO -20C THURSDAY NIGHT SHOULD YIELD MODEST LAKE
RESPONSE...HOWEVER BACKGROUND NORTH/NORTHEASTERLY FLOW SHOULD KEEP
BEST LAKE EFFECT SNOW CHANCES WEST OF THE FORECAST AREA THURSDAY
NIGHT THROUGH FRIDAY. CONTINUED A DOWNWARD TREND IN MIN TEMPS
THURSDAY NIGHT OUTSIDE OF LAKE EFFECT CLOUD COVER. WITH SFC RIDGE
EXPECTED DIRECTLY OVER THE REGION FRIDAY NIGHT...SIGNIFICANT
RADIATIONAL COOLING EXPECTED AND HAVE ACCOUNTED FOR THIS WITH A
LOWERING OF MIN TEMPS FRIDAY NIGHT...SEVERAL DEGREES LOWER THAN 12Z
SUPERBLEND.

EJECTION OF SWRN CONUS TROF ENERGY WILL BRING PRECIP CHANCES SUNDAY
INTO MONDAY. LATEST 12Z GUIDANCE CONTINUES TO SHOW A MORE
SOUTHERLY/SUPPRESED SNOWFALL TRACK AS STRONG NORTHERN STREAM VORT
SWINGS EAST ACROSS THE NORTHERN GREAT LAKES. OWING TO LATEST
TRENDS...THERMODYNAMIC PROFILES SUPPORT ALL FROZEN PRECIP...SO
REMOVED RAIN MENTION FOR SOUTHERN HALF OF THE FORECAST AREA SUNDAY
AFTERNOON.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1238 AM EST WED FEB 25 2015

DRY SURFACE COLD FRONT WILL CROSS THE AREA DURING THE NEXT FEW
HOURS. FORECAST SOUNDINGS AND MOS GUIDANCE STILL SUGGEST A BRIEF
PERIOD OF HIGH END MVFR CEILINGS POSSIBLE AT KSBN IMMEDIATELY
BEHIND THE FRONT GIVEN QUICK SHOT OF BOUNDARY LAYER COOLING AND
MOISTURE FLUX FROM LAKE MICHIGAN. DRY AIR ADVECTION SHOULD
SCATTER LOW CLOUDS BY LATE MORNING THOUGH AND VFR CONDITIONS
EXPECTED THROUGH THE REST OF THE DAY. NEXT CHANCE OF LIGHT SNOW
AND REDUCTION IN FLIGHT CATEGORY LOOKS TO BE JUST OUTSIDE THIS TAF
FORECAST PERIOD...AS A WEAK AND MOISTURE STARVED SHORTWAVE SWINGS
THROUGH THE REGION.


&&

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

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...LASHLEY
AVIATION...AGD


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