National Weather Service Raw Text Product

454 
FXUS63 KIWX 260915
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
415 AM EST WED FEB 26 2014

.SYNOPSIS...
ISSUED AT 415 AM EST WED FEB 26 2014

LAKE EFFECT SNOW WILL GRADUALLY WEAKEN AND SHIFT NORTH LATER THIS
MORNING AS WINDS BACK TO A MORE SOUTHWESTERLY DIRECTION. ANOTHER
UPPER LEVEL DISTURBANCE WILL ARRIVE TONIGHT THOUGH...WITH MORE
LAKE EFFECT SNOW EXPECTED THROUGH THURSDAY. ACCUMULATIONS WILL BE
LIGHT BUT PATCHY BLOWING SNOW MAY IMPACT THE THURSDAY MORNING
COMMUTE ACROSS SOUTHERN LOWER MICHIGAN AND EXTREME NORTHERN
INDIANA. VERY COLD CONDITIONS WILL PERSIST THROUGH FRIDAY. 

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 415 AM EST WED FEB 26 2014

LAKE EFFECT SNOW AND VERY COLD TEMPERATURES REMAIN THE FOCUS OF
THE SHORT TERM PERIOD AS UNRELENTING WINTER CONTINUES. LATEST
WATER VAPOR IMAGERY SHOWS SHORTWAVE TROUGH CURRENTLY SWINGING
THROUGH THE SOUTHERN GREAT LAKES. ASSOCIATED UPTICK IN QG ASCENT
HAS ALLOWED INVERSION HEIGHTS TO CLIMB WHILE PERSISTENT CAA FORCES
A MORE ROBUST LAKE INDUCED INSTABILITY PROFILE. PASSING VORT MAX
HAS ALSO FORCED LOW LEVEL WINDS TO VEER A BIT AND LAKE EFFECT SNOW
SHOWERS HAVE BEEN EXPANDING OVER OUR CWA AS A RESULT. WE ARE
LIKELY NEAR THE PEAK OF THIS ROUND OF LAKE EFFECT SNOWFALL THOUGH.
SHORTWAVE WILL EXIT BY LATER THIS MORNING WITH INCREASING
SUBSIDENCE AND BACKING WINDS BRINGING AN END TO SNOWFALL
EVERYWHERE BY MIDDAY. AFTERNOON TEMPS WILL REMAIN VERY COLD. 925MB
TEMPS HOVER AROUND -18C FOR MUCH OF THE DAY...SUGGESTING HIGHS
ONLY IN THE MID TO UPPER SINGLE DIGITS. THIS IS GENERALLY
SUPPORTED BY NEWEST MAV/MET GUIDANCE BUT NOT CONFIDENT ENOUGH TO
GO QUITE THAT COLD. INCREASING SOLAR INSOLATION THIS TIME OF
YEAR...AND LOWER ALBEDO NOTED BY PREVIOUS FORECASTER...WILL
PROBABLY HAVE SOME INFLUENCE AND HAVE STUCK PRETTY CLOSE TO
INHERITED HIGHS IN THE LOWER TEENS.

YET ANOTHER CLIPPER SYSTEM AND YET ANOTHER SHOT OF COLDER AIR/LIGHT 
SNOWFALL WILL ARRIVE BY LATER TONIGHT. THIS SHORTWAVE IS ACTUALLY 
THE MOST IMPRESSIVE ONE YET JUDGING BY WATER VAPOR AND MODEL PV 
FIELDS...BEING DRIVEN BY 130+ KT MID/UPPER LEVEL JET MAX. DYNAMICS 
ALOFT ARE EXCELLENT BUT DRY/STABLE AMBIENT AIRMASS WILL MUTE THE LOW 
LEVEL RESPONSE A BIT. FURTHERMORE...THE BEST PV ADVECTION AND LEFT 
EXIT REGION DYNAMICS PASS JUST TO OUR NORTH...AFFECTING MAINLY 
MICHIGAN. DECENT CYCLOGENESIS IS EXPECTED BUT IT WILL BE OVER THE 
NORTHERN GREAT LAKES. PRECIP CHANCES FOR MOST OF OUR COUNTIES WILL 
DEPEND ON LOW LEVEL CONVERGENCE/CYCLONIC FLOW ASSOCIATED WITH 
PASSING COLD FRONT RIGHT AROUND 12Z. THIS DOES NOT BODE WELL FOR 
ANYTHING MORE THAN A FEW FLURRIES ALONG AND SOUTH OF US-30 GIVEN 
MIXING RATIOS CLOCKING IN AT A PALTRY 1 G/KG. BETTER CHANCES FOR 
ACCUMULATING SNOWFALL EXPECTED IN OUR NORTHERN COUNTIES GIVEN 
THETA-E CONTRIBUTION OF LAKE MICHIGAN ALONG WITH CLOSER PROXIMITY TO 
LARGE SCALE FORCING BUT AMOUNTS PRIOR TO 12Z WILL STILL BE LIMITED 
TO A FEW TENTHS. WILL BE A STRONG GRADIENT WIND THOUGH AND EXPECTED 
SMALL FLAKES MAY CAUSE SOME AREAS TO EXPERIENCE SIGNIFICANTLY 
REDUCED VISIBILITIES DURING THE MORNING COMMUTE DESPITE MARGINAL 
ACCUMULATIONS. WINTER WEATHER ADVISORY MAY EVENTUALLY BE NEEDED FOR 
SOME OF OUR NORTH/NORTHWEST COUNTIES BUT AFTER COORDINATION WITH 
LONG TERM FORECASTER DECIDED TO HOLD OFF ON ISSUANCE GIVEN MAIN 
IMPACTS STILL OVER 24 HOURS AWAY.

OVERNIGHT LOWS ARE A BIT TRICKY WITH COLDEST TEMPS LIKELY OCCURRING 
RIGHT AROUND OR JUST AFTER 12Z IN THE WAKE OF PASSING COLD FRONT. 
OVERNIGHT TEMPS WILL PROBABLY REMAIN STEADY OR EVEN RISE A BIT GIVEN 
STRONG SOUTHWEST WINDS AND MAY EVEN SEE CALENDAR DAY HIGHS FOR THE 
26/27 OCCUR DURING THE TONIGHT PERIOD. MADE A FEW SLIGHT ADJUSTMENTS 
TO MIN TEMPS BASED ON LATEST MODEL TIMING OF COLD AIR SURGE BUT 
OVERALL CHANGES MINIMAL. AFTER MODERATING THIS AFTERNOON AND 
EVENING...WIND CHILL VALUES WILL RETURN TO ADVISORY CRITERIA OF -15 
TO -20 BY THURSDAY MORNING AND ANOTHER WIND CHILL ADVISORY WILL 
LIKELY BE NEEDED.
   
&&

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 415 AM EST WED FEB 26 2014

DEEP UPR LOW OVER ONTARIO WILL BEGIN THE LONG TERM PERIOD WITH 
STRONG NW FLOW FROM THE GRTLKS TO THE ARCTIC ENSURING AN EXTREMELY 
COLD AIRMASS WILL BE OVERSPREADING THE CWA THU. AT THE SFC A RATHER 
STRONG LOW OVER SE ONTARIO THU MORNING WITH A TRAILING COLD FRONT 
ACROSS THE OH VALLEY AND ARCTIC HIGH OVER THE NRN PLAINS WILL 
PROVIDE CAA THROUGH THE DAY RESULTING IN ONLY SLIGHT TEMPERATURE 
RISES FROM MORNING LOWS WITH BRISK NW WINDS CAUSING ADVISORY LEVEL 
WIND CHILLS. LAKE INDUCED INSTABILITY FCST BY NAM BUFR SOUNDINGS TO 
BE AROUND 700J/KG THU WITH INVERSION AROUND 7500FT IN THE MORNING 
LOWERING TO AROUND 5KFT BY EVE. 1000-850MB MOISTURE ALSO FCST TO BE 
>80% THOUGH SUSPECT THIS IS TOO MOIST GIVEN ORIGINS OF AIRMASS IN 
THE ARCTIC. STRONG NW WIND SHOULD ALLOW LAKE EFFECT BANDS TO 
PENETRATE WELL INLAND. CONTD WITH SNOW SHOWERS MENTIONED ACROSS ALL 
BUT FAR SRN PORTION OF CWA AND BUMPED UP POPS TO CATEGORICAL 
ACROSS SWRN LWR MI. ACCUMS ONLY FCST AROUND AN INCH AS DGZ IN 
SFC-2KFT RANGE SHOULD KEEP FLAKES FINE AND ACCUMULATIONS COMPACT.

HIGH PRESSURE WILL MOVE QUICKLY ACROSS THE CWA THU NGT CAUSING 
DIMINISH WINDS AND CLEARING SKIES. WITH SNOW COVER ACROSS THE CWA AT 
LEAST PERSISTING... AND IN SOME CASES INCREASING OVER THE NEXT 
COUPLE OF DAYS... EXPECT STRONG RADIATIONAL COOLING OVERNIGHT 
LEADING TO RECORD LOWS IN THE -5F TO -15F RANGE. ALTHOUGH WINDS WILL 
BE LIGHT AND PRBLY CALM AT TIMES OVERNIGHT... GRADIENT SHOULD PICK 
UP AROUND DAWN RESULTING IN WIND CHILL ADVISORY CONDITIONS ONCE 
AGAIN BY FRIDAY MORNING. 

FOR THE EXTENDED FCST... MODELS IN DECENT AGREEMENT THAT FLOW ACROSS 
THE CONUS WILL BECOME MORE ZONAL LATE IN THE WEEK AS THE STRONG 
SHRTWV ROTATING AROUND HUDSON BAY LOW LIFTS NE FROM THE GRTLKS TO 
SERN CANADA. A WK SHRTWV MOVG EAST IN THE ZONAL FLOW FROM THE 
PACIFIC IS EXPECTED TO MOVE ACROSS OUR AREA FRIDAY NIGHT PSBLY 
CAUSING SOME LIGHT SNOW. A MORE SGFNT SNOW EVENT PSBL SAT NGT-SUNDAY 
AS A STRONGER SHRTWV MOVES EAST INTO THE SRN PLAINS TAPPING GULF 
MOISTURE AND INDUCING STRONG UPR LEVEL JET ACROSS THE GRTLKS WITH 
ATTENDANT RIGHT ENTRANCE REGION LIFT INTO THE OHIO VALLEY. THUS, 
APPEARS TO BE POTENTIAL FOR SGFNT SNOW ACCUMS ESPECIALLY ACROSS THE 
SERN PORTION OF OUR CWA IN THIS TIMEFRAME... THOUGH STILL 
SUBSTANTIAL DIFFERENCES IN MODEL FCSTS REMAIN ON WHERE BAND OF 
HEAVIEST PRECIP ASSOCIATED WITH THIS SYSTEM WILL OCCUR. 

IN THE WAKE OF THE WEEKEND SHRTWV... HIGH PRESSURE SHOULD MOVE INTO 
THE AREA PROVIDING GENERALLY DRY WX WITH JUST A SLIGHT CHC OF SNOW 
SHOWERS AND TEMPS CONTG WELL BLO NORMAL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1235 AM EST WED FEB 26 2014

LAKE EFFECT SNOW SHOWERS STEADILY INCREASING AS ROBUST MIDLEVEL
VORT MAX ENTERS THE GREAT LAKES REGION AND LOW LEVEL WINDS VEER TO
A MORE NORTHWESTERLY DIRECTION. COMBINATION OF SYNOPTIC LIFT AND
INCREASINGLY COLD AIR FILTERING OVER THE LAKE WILL CONTINUE TO
SUPPORT MODERATE SNOW BANDS THROUGH THE EARLY MORNING HOURS.
ACCUMULATIONS WILL BE LIMITED BY DRY AIR ENTRAINMENT BUT BRIEF
PERIODS OF IFR/FUEL ALTERNATE CONDITIONS ARE POSSIBLE AT KSBN WITH
HIGHER END MVFR EXPECTED AT KFWA. LAKE EFFECT SNOW WILL CLEAR BY
LATER THIS MORNING AS WINDS BACK TO THE SOUTHWEST BUT FORECAST
SOUNDINGS SUGGEST LOW END VFR/HIGH END MVFR STRATUS DECK REMAINING
OVER THE REGION FOR MUCH OF THE DAY.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WIND CHILL ADVISORY UNTIL NOON EST /11 AM CST/ TODAY FOR 
     INZ003>005-008-012>018-020-022>027-032>034.

MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...JT
AVIATION...AGD


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