FXUS63 KIWX 100541
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1241 AM EST THU DEC 10 2009
.AVIATION...
DEPARTING SFC CYCLONE CONTINUES TO SUPPORT CAA INTO THE
FA...RESULTING IN LAKE EFFECT SNOW ACROSS THE NORTH...WITH
LINGERING WEAK VERTICAL ASCENT PER CONTINUED STRONG MECHANICAL
MIXING OVER THE REMAINDER OF THE FA. HIGH RH BOUNDARY LAYER WILL
NOT BEGIN TO DRY OUT UNTIL MID TO LATE MORNING WITH LIGHT SNOW
ACTIVITY EXPECTED TO PERSIST ACROSS MUCH OF THE FA...WITH MVFR TO
IFR VIS EXPECTED. OTHERWISE...NW AREAS WILL SEE CONTINUED LIGHT TO
MODERATE LAKE EFFECT SNOW SHOWERS GIVEN INCREASING LAKE INDUCED
INSTABILITY. BULK OF ACTIVITY IS EXPECTED TO REMAIN NORTH OF
SBN...WITH MAIN VIS RESTRICTIONS FROM BLSN THERE.
SFC HIGH PRESSURE WILL BUILD INTO THE REGION ON THUR...WITH VFR
CONDITIONS OVER THE MAJORITY OF THE FA...SAVE THE NNW WHERE LAKE
EFFECT CLOUDS AND SNOW SHOWERS WILL CONTINUE TO SUPPORT MVFR TO IFR
CONDITIONS. SBN WILL BE ON THE EDGE OF SNOW VIS RESTRICTIONS...BUT
GIVEN DIURNAL COOLING AND SLIGHT VEERING IN THE WIND PROFILE...DO
EXPECTED AT LEAST MVFR CIGS/VIS WITH POSSIBLE IFR CONDITIONS
RETURNING BY EVENING.
&&
.PREV DISCUSSION... /ISSUED 644 PM EST WED DEC 9 2009/
UPDATE...
RESIDUAL SFC TROUGH EXTNDG SWWD FM INTENSE SFC LOW OVR
GEORGIAN BAY CONTS TO SPRT AREA OF SYNOPTIC SNOW ACRS NRN IL INTO
NW IN/SW MI. IN ADDN W/DIMINISHING GRADIENT FLW...LAKE ENHANCEMENT
NOW DVLPG W/SVRL REPORTS OF LIGHTNING/THUNDER WITHIN SINGLE BAND
EXTENDING FM JUST OFFSHORE OF WAUKEGAN WELL INLAND INTO BERRIEN
SPRINGS/BARODA.
18Z NAM/LATEST RUC SHOW EVER INCREASING LK RESPONSE ASSOCD/W GRADUAL
LL VEERING FLW AND INCREASING DELTA-T. HWVR LIMITING FCTR WILL BE
EVENTUAL LOSS OF SYNOPTIC MSTR AND XPCD WAVERING SNOW BAND. CALLS
INTO SW MI ALG W/VARIOUS WEBCAMS SHOW DETERIORATING CONDS OVR SW MI
AND HAVE UPGRADED PREV ADVISORY TO A WARNING W/SVRL ADDNL INCHES OF
ACCUMULATION AND CONTD WINDY CONDS PROMOTING WIDESPREAD BLOWING SNOW
W/NR WHITEOUT CONDS.
OTHERWISE XPC MVFR CONDS WILL HOLD OVERNIGHT W/CONTD STG GRADIENT
FLW...ESP AT KFWA W/GUSTS YET TO 40KTS EARLY THIS EVENING BUT
DIMINISHING OVERNIGHT. DVLPG LK SNOW BAND SHLD STAY NORTH OF KSBN
TERMINAL BUT STILL HAVE TO CONTEND W/AREA OF LIGHT SNOW PIVOTING EWD
OUT OF IL W/PD OF IFR RESTRICTION YET THROUGH LATE EVENING.
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT
PRIMARY CONCERNS IN THE SHORT TERM PERIOD REVOLVE AROUND POSSIBLE
BLIZZARD CONDITIONS IN THE FAR NW...FIRST TRUE COLD AIR INTRUSION OF
THE WINTER...AND STRONG WINDS INTO TONIGHT.
DEEP NEARLY STACKED LOW...975 MB AT THE SFC...ACROSS NRN LOWER MI
WILL GRADUALLY PROPAGATE NEWD INTO SW QUEBEC BY LATE TONIGHT/THU.
STAUNCH CAA WILL CONTINUE INTO TONIGHT BEHIND THIS SYSTEM WITH TEMPS
FCST TO DROP INTO THE UPPER SINGLE DIGITS TO MID TEENS BY DAYBREAK
THU. TIGHT SFC PRESSURE GRADIENT AROUND DEEP SFC LOW STILL
YIELDING 30-40 MPH SUSTAINED WINDS WITH GUSTS OF 50-60 MPH. THESE
WINDS WILL RELAX A BIT TONIGHT BUT WILL STAY UP ENOUGH TO ALLOW
FOR WIND CHILLS TO DROP INTO THE SINGLE DIGITS BLO ZERO LATE
TONIGHT INTO THE FIRST PART OF THU MORNING. GRADIENT REALLY DOES
NOT RELAX MUCH MORE TOMORROW AS THE FA WILL BE BETWEEN THE
RETREATING SFC LOW AND A DOME OF HIGH PRESSURE TO THE SOUTH. AS
FOR PRECIP...THE TAIL END OF THE DEFORMATION AXIS IS CURRENTLY
PIVOTING THROUGH THE FA AS OF 19Z. THERE IS AN AREA OF -SN WITHIN
THIS BAND...HEAVIEST IN THE FAR NW WHERE THERE IS SOME LAKE
ENHANCEMENT. EXPECT AN INCH OR TWO OF ACCUMULATION BY EARLY THIS
EVENING IN FAR NW/NC IN AND SW LOWER MI...WITH LESSER AMOUNTS AS
YOU GO SOUTH AND EAST. THE AFOREMENTIONED STRONG WINDS WILL CREATE
BLOWING SNOW AND REDUCED VISIBILITIES. THIS COMBINED WITH THE
FALLING SNOW AND TEMPS FALLING THROUGH THE 20S WILL CREATE SLICK
SPOTS ON AREA ROADS. AS A RESULT...WILL CONTINUE WITH THE WINTER
WX ADV IN THE NW WHERE ACCUMULATIONS SHOULD EXCEED AN INCH THROUGH
EARLY THIS EVENING. COVERED THE REST OF THE FA WITH AN SPS
MENTIONING POTENTIAL SLICK SPOTS WITH ONLY LIGHT SNOW ACCUMS. THIS
ACTIVITY SHOULD TAPER OFF TO FLURRIES THIS EVENING. TONIGHT
THROUGH THURSDAY NIGHT ACROSS MOST OF IN AND OH WILL FEATURE COLD
AND DRY CONDITIONS (OUTSIDE OF A FEW FLURRIES OVERNIGHT) WITH
WINDS AND CLOUDS DIMINISHING WITH TIME...AND TEMPS WELL BLO
NORMAL.
LAKE EFFECT SNOW/BLOWING SNOW WILL DEVELOP TONIGHT AND CONTINUE
INTO THU/THU EVE ACROSS AT LEAST BERRIEN/CASS/ST JOE COUNTIES IN MI
AS COLD WESTERLY FLOW PERSIST. DELTA T/S WILL INCREASE FROM THE
MID TEENS LATE THIS AFTN TO LOW TO MID 20S BY LATE TONIGHT INTO
THU WITH CONTINUED CAA. THIS WILL ALLOW FOR LAKE INDUCED CAPES TO
INCREASE TO 600-800 J/KG...SUPPORTING CATEGORICAL POPS FOR LAKE
EFFECT SNOW IN SW LOWER MI GIVEN NEARLY 280 FETCH. HOWEVER...STRONG
FLOW THROUGH THE COLUMN AND UNFAVORABLE SHORT FETCH HINT AT A LACK
OF ANY TRUE/LONG LASTING ORGANIZATION TO BANDS IN OUR FA. THIS
SHOULD KEEP ACCUMULATIONS FROM GETTING OUT OF CONTROL IN NRN
PORTIONS OF THE AFOREMENTIONED COUNTIES. REGARDLESS...IT IS GOING
TO BE TOUGH GETTING AROUND WITH 2-6 INCHES OF SNOW ACCUMULATION
GETTING BLOWN AROUND BY SUSTAINED WINDS THAT WILL STILL BE 20-30
MPH BY THU. CONTINUED WITH A WINTER WX ADVISORY IN BERRIEN/CASS
THROUGH THU EVENING...AND EXTENDED IT INTO ST JOE MI STRONG FLOW
GETTING ANY SNOW SHOWER ACTIVITY FAR INLAND. CONSIDERED UPGRADING
TO A BLIZZARD WARNING HERE DUE TO STRONG WINDS/REDUCED VIS/COLD
TEMPS. NOT ENOUGH CONFIDENCE TO PULL THE TRIGGER AT THE POINT AS
NOT 80 PERCENT OR GREATER CONFIDENCE IN 3 OR MORE STRAIGHT HOURS
OF BLIZZARD CONDITIONS IN ANY LOCATION.
LONG TERM...
MAIN ITEMS IN THE EXTENDED REVOLVE AROUND WHEN TO END LAKE EFFECT
POPS IN MICHIGAN COUNTIES AND TIMING OF NEXT WAVE TO AFFECT THE AREA.
TODAYS MODEL CONSENSUS KEEPS LLEVEL WINDS WESTERLY FOR 12 HOURS
LONGER THAN YDAY...THROUGH SAT 12Z..WHICH IS ALSO WHEN H85 TEMPS
WARM SUFFICIENTLY TO SHUT DOWN MECHANISM. HOWEVER...BUFR SOUNDINGS
SUPPORT CURRENT TIMING OF ENDING POPS BY 00Z SAT...AND ANY IMPACT
AFTER 12Z FRI WOULD BE MINIMAL GIVEN DRY NAM BUFR SOUNDING AND
INVERSION HEIGHT BELOW DGZ. THUS..FEW CHANGES FOR THIS PERIOD
OTHER THEN TO TIGHTEN UP POPS BASED ON WIND DIRECTION/NAM PLUME
ANALYSIS. AS TEMPS ALOFT RISE HIGHS WILL MODERATE BACK TO NEAR OR
JUST ABOVE FREEZING SAT AND CLOSER TO CLIMO SUN. WONT BUY IN
COMPLETELY TO WARMER MEX GUIDANCE WHICH HAS COME UP 10 DEGREES FOR
SUNDAY HIGHS OVER THE PAST 48 HOURS...BUT WILL TREND THAT DIRECTION
CLOSER TO THE ENSEMBLE MEAN.
LATE EXTENDED IS STILL HAMPERED BY SIGNIFICANT DIFFERENCES IN MODEL DETAILS
BEYOND SUNDAY AS HANDLING DIVERGES RAPIDLY WITH ALEUTIAN LOW AND
RETROGRESSION OF VORTEX OVER CANADA BEFORE IT SINKS SW AND
DIGS OUT RENEWED TROUGHING THROUGH THE CENTRAL PLAINS INTO THE
GREAT LAKES. BOTH MODELS BRING WAA PRECIP INTO THE CWA...BUT
DIFFER BY 12-24 HOURS SUN/MON...AND FOLLOW WITH ANOTHER WAVE COMING
OUT OF THE CENTRAL PLAINS WITH THE GFS MUCH WEAKER/FASTER AND THE
ECMWF COMPACT BUT MORE POTENT. THUS THE SOLNS CONTINUE TO INDICATE A
CHANCE FOR PRECIP AT SOME POINT EARLY IN THE WEEK BUT RUN TO RUN
CONSISTENCY IS POOR MAKING TIMING DECISION QUITE DIFFICULT. AS A
COMPROMISE BETWEEN THE MODELS AND COLLAB WITH NEIGHBORING
OFFICES...CHC POPS HAVE BEEN ADDED MONDAY. COOLER AIR SHOULD
FOLLOW MIDWEEK WITH TROUGH PROGRESSING THROUGH THE UPPER MIDWEST AND
TEMP GRIDS REFLECT A MODEST COOL DOWN DAYS 6-7.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ077>079.
OH...NONE.
LM...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LMZ043-046.
&&
$$
SHORT TERM...STEINWEDEL
LONG TERM...LUDINGTON
AVIATION...JC
UPDATE...HOLSTEN
