Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 260659
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
159 AM EST THU FEB 26 2015

.SYNOPSIS...
ISSUED AT 151 AM EST THU FEB 26 2015

A LOW PRESSURE AREA WILL MOVE SOUTHEAST OUT OF THE REGION EARLY
TODAY...LEAVING SOME LIGHT SNOW ACCUMULATIONS. SNOWFALL AMOUNTS
OVER NORTHEAST ILLINOIS SHOULD RANGE FROM 1 TO 3 INCHES...WITH
AROUND AND INCH OVER NORTHERN INDIANA. MUCH COLDER AIR WILL
RETURN TO THE REGION BEHIND THIS SYSTEM...WITH HIGHS TODAY ONLY
AROUND 15. TEMPERATURES WILL PLUMMET BELOW ZERO LATE TONIGHT.

&&

.UPDATE...
ISSUED AT 836 PM EST WED FEB 25 2015

HIGHLY SHEARED UPPER LEVEL WAVE FROM WEST CENTRAL ILLINOIS INTO
SOUTHWEST LOWER MICHIGAN WILL CONTINUE TO PUSH EASTWARD ACROSS THE
SOUTHERN GREAT LAKES OVERNIGHT. MID LEVEL SPEED MAX ASSOCIATED
WITH THIS SHORT WAVE IS ALSO EVIDENT PER 00Z DVN RAOB WITH 35-45
KNOT 700 HPA WINDS. SYNOPTIC FORCING WITH EASTWARD EXTENT OF THIS
FEATURE SHOULD BE ON THE WANE HOWEVER DUE TO HIGHLY SHEARED
NATURE. ASSOCIATED WEAK LOW/MID LEVEL FGEN FORCING TO ALSO
OVERSPREAD THE AREA OVERNIGHT...AND THIS FORCING COMBINED WITH A
PROGRESSIVE WEAK LOW LEVEL MOISTURE AXIS SHOULD BE ENOUGH TO AT
LEAST ALLOW LIGHT SNOW TO AFFECT MOST AREAS OVERNIGHT. NAM/RAP
SUGGEST STRONGEST FGEN FORCING TO RESIDE ACROSS THE
WEST/SOUTHEAST...WHERE MOISTURE PROFILES ALSO MAY BE A BIT MORE
RESPECTABLE. ALL IN ALL...CURRENT TRENDS SEEM TO SUPPORT PREVIOUS
FORECAST WITH ACCUMULATIONS AROUND AN INCH OR LESS...EXCEPT PERHAPS
IN THE 1 TO 2 INCH RANGE ACROSS THE WEST/SOUTHWEST. UPDATED
FORECAST SENT MAINLY TO ACCOUNT FOR SLIGHTLY EARLIER ONSET ACROSS
THE WEST THIS EVENING AND TO INCREASE TO CATEGORICAL POPS FOR
THESE LOCATIONS.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 307 PM EST WED FEB 25 2015

FOCUS WILL BE ON WEAKENING SYSTEM APPROACHING THE SOUTHERN GREAT
LAKES TONIGHT INTO EARLY THURSDAY.

MID/HIGH CLOUDS WILL CONTINUE TO STREAM IN AHEAD OF AN UPPER LEVEL
WAVE DROPPING THROUGH SOUTH DAKOTA EARLY THIS AFTERNOON. SYSTEM WILL
BRING DECENT ACCUMULATIONS TO PARTS OF IOWA AND ILLINOIS BUT LOSE A
LOT OF ITS IMPACT AS IT SHIFTS EAST AND SOUTH AS ENERGY BECOMES
ABSORBED IN TROUGH TAKING SHAPE ACROSS THE SE US. PLENTY OF MOISTURE
WILL MOVE IN WITH RAPID SATURATION IN THE 4 TO 8Z THURS WINDOW WITH
A LARGE DGZ OF 10-12 KFT. HOWEVER LIFT REMAINS GENERALLY ABOVE THE
DGZ IMPACTING FLAKE SIZE AND TYPE. THIS COMBINED WITH A FAIR AMOUNT
OF DRY AIR WILL LIKELY KEEP SNOW AMOUNTS DOWN WITH AN INCH OR SO...
LESSER AMOUNTS EAST. HAVE INCREASED TO LIKELY...BLENDING WITH
SURROUNDING OFFICES MAINLY LATE EVENING INTO THURSDAY MORNING. SREF
PLUMES SUGGESTS 1 TO 2 INCHES ACROSS THE AREA WHICH ISN`T COMPLETELY
OUT OF THE REALM OF CHANCE BUT WITH MAIN WAVE DROPPING SE VS MOVING
ACROSS THE AREA THINK CHANCES ARE ON THE LOW SIDE RIGHT NOW. WILL
DEFER TO EVE SHIFT TO WATCH TRENDS.

AS THE SYSTEM MOVES AWAY...N TO NE FLOW WILL SETUP WITH LK TO 850 MB
DELTA T`S AROUND 20. NAM/GFS TRY TO BRING THE BAND BACK EAST WITH
TIME AFTER 18Z THURS WITH LOCAL WRF POINTING MORE TOWARDS 00Z FRI.
INVERSION HGTS WILL PEAK OUT AROUND 6000 FT BUT NOT UNTIL NEAR THE
END OF THE FORECAST PERIOD INTO THE LONG TERM. HAVE BACKED OFF ON
TIMING OF BAND INTO LAPORTE COUNTY BUT WENT WITH LIKELY POP LAST
HOUR OR 2 TO BLEND WITH MORE FAVORABLE WINDOW IN LONG TERM.

LOWS TONIGHT WILL DROP OFF IN THE SINGLE DIGITS NE WHERE SKIES WILL
TAKE LONGER TO CLOUD OVER AND MID TEENS WEST AND SOUTH. ON THURSDAY
EXTENSIVE CLOUD COVER MUCH OF THE DAY SHOULD KEEP HIGHS CONFINED TO
THE TEENS WITH COLDER AIR BEGINNING TO EDGE IN TOWARDS EVENING.

&&

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 307 PM EST WED FEB 25 2015

QUIET/UNSEASONABLY COLD WX EXPECTED FRIDAY INTO SATURDAY AS ARCTIC
HIGH PRESSURE ENCOMPASSES THE AREA. A MORE ACTIVE WEATHER PATTERN
WITH GRADUAL TEMP MODERATION WILL THEN TAKE HOLD ON THE REGION
SUNDAY INTO NEXT WEEK AS THE FLOW ALOFT BECOMES WSW DOWNSTREAM OF A
DIGGING WESTERN CONUS TROUGH. LEAD/SHEARED SHORTWAVE ENERGY WITHIN
STRENGTHENING MID-UPPER LEVEL FLOW...AND WHAT SHOULD AMOUNT TO A
DECENT SURGE OF MOISTURE (3-3.5 G/KG WITHIN A CONTINUES STREAM OF
SYSTEM RELATIVE ISENTROPIC ASCENT)...WILL LIKELY ALLOW A WIDESPREAD
AREA OF SNOW TO DEVELOP ALONG A MID LEVEL BAROCLINIC ZONE LATER
SATURDAY NIGHT INTO SUNDAY MORNING...WITH FGEN FORCING ENHANCED
LOCALLY LATER SUNDAY-SUNDAY EVENING AS A SEPARATE NORTHERN STREAM
SHORTWAVE DROPS INTO THE WESTERN LAKES. SOME ACCUMULATION APPEARS
LIKELY (2-4"?)...THOUGH EXPECT MODELS TO TREND A LITTLE DRIER AND
MORE SUPPRESSED AS WE GET CLOSER TO THE EVENT. THE AFOREMENTIONED
NORTHERN STREAM WAVE SHOULD FORCE THE BAROCLINIC ZONE/PCPN SOUTH
OF THE AREA BY MONDAY SUPPORTING A BRIEF LULL BEFORE THE NEXT WAVE
EJECTS OUT AROUND TUESDAY-TUESDAY NIGHT WITH THE NEXT CHANCE FOR
PCPN (ALL PTYPES POSSIBLE FOR THIS EVENT) AND POTENTIAL IMPACTS TO
TRAVEL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 103 AM EST THU FEB 26 2015

A WEAK LOW PRESSURE AREA WITH WEAK LIFT WILL MOVE SOUTHEAST OUT OF
THE AREA EARLY TODAY AS MUCH COLDER AND DRIER SPREADS BACK OVER
NORTHERN INDIANA FROM LOWER MICHIGAN. UPSTREAM CONDITIONS OVER
LAKE HURON AND EASTERN LAKE SUPERIOR WILL NOT CONTRIBUTE MUCH
MOISTURE GIVEN NEAR 100 PERCENT ICE COVERAGE OF THESE LAKES...SO
EXPECT CONDITIONS TO IMPROVE LATER TODAY WITH DRY AIR ENTRAINMENT
IN THE LOWER ATMOSPHERIC LAYERS. MAY HAVE TO ADJUST THE TRANSITION
TIME FROM MVFR TO VFR...FOR NOW...HAVE SBN BECOMING VFR AT 14Z AND
FWA AT 23Z.

&&

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

$$

UPDATE...MARSILI
SYNOPSIS...SKIPPER
SHORT TERM...FISHER
LONG TERM...STEINWEDEL
AVIATION...SKIPPER


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