Winter Weather in Illinois, February 18, 2006

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PADUCAH KY
955 PM CST FRI FEB 17 2006

.UPDATE...
RADAR SHOWS UPSTREAM ECHOES IN SRN MO/NRN AR NOT YET REACHING
GROUND...BUT SOME REPORTS FURTHER WEST INTO NW AR STARTING TO SHOW
UP IN NETWORK. TEMP CURVE SHOWS TEMPS NOT DROPPING AS MUCH AS PREVIOUSLY
ANTICIPATED...AND INCOMING 00Z MET DATA PICKS UP ON THIS AND
SLIGHTLY WARMS GOING AND OVERNIGHT TEMPS...WHICH WE TWEEKED IN
GRIDS/ZONES. THIS WL NOT MAKE MUCH DIFFERENCE IN EXPECTED PCPN
THOUGH...EXCEPT ALONG AR/TN BORDERS...WHERE 00Z RUC AND NAM SOUNDINGS
SHOW PCPN MAY BEGIN AS BRIEF PERIOD OF SLEET IF ANY REACHES THE
GROUND PRIOR TO 06Z...CONFIRMED IN BOOTHEEL ALREADY. SINCE SAME
SOUNDINGS DONT SHOW LOWER TROP SATURATION TIL AFT 06Z...WE CHOSE TO
THROW A MENTION OF THIS INTO THE ZFP BUT RETAIN THE WSW LARGELY AS
WRITTEN. SOME CONSIDERATION GIVEN TO SLIGHT EXPANSION NORTHWARD INTO
MORE OF SEMO SINCE 00Z GFS TRICKLED IN...BUT 00Z NAM
CONTRADICTS...SO WE LEFT IT ALONE AND WILL INCLUDE ON THE BRIEF FOR
A CLOSE MONITORING ON THE DEVELOPING PCPN ZONE. LATEST HPC WWD
PAINTS SRN FA IN 2-4 SWATH POSSIBLE AND 00Z MODEL QPF SUPPORTS OUR
CURRENT 1-3 WORDING GIVEN 15-1 RATIOS. ISOLATED HIGHER AMOUNTS ARE
POSSIBLE AND IS LIKEWISE MENTIONED.

.SHORT TERM /TONIGHT THROUGH MONDAY/...

AS STATED IN PREVIOUS AFD...HAVE SPREAD THE ADVISORY UP A ROW OF
COUNTIES ACROSS THE SOUTHERN TIP OF ILLINOIS AND IN WEST KENTUCKY.
THE TIMING REMAINS THE SAME...10 PM TO 8 AM.

STRATOCU DECK HANGING FAIRLY STRONG ACROSS SOUTHERN ILLINOIS AND
SOUTHWEST INDIANA...ELSEWHERE MID AND HIGH CLOUD BEGINNING SPREAD
EASTWARD INTO WESTERN ZONES. SHOULD SEE MID AND HIGH CLOUDS
INCREASING RAPIDLY ACROSS THE AREA THIS EVENING...AHEAD OF
APPROACHING WINTER STORM. MEANWHILE...DECENT NORTH WINDS WILL
CONTINUE THROUGH THE NIGHT...BRINGING MUCH COOLER AIRMASS OVER THE
REGION. ALOFT...SOME FRONTOGENETICAL FORCING IN THE 800MB TO 700MB
LAYER WILL HELP SNOW TO DEVELOP FROM WEST TO EAST LATE THIS
EVENING THROUGH THE OVERNIGHT HOURS. MODELS ARE IN DECENT
AGREEMENT ON THESE POINTS...BUT QPF IS A DIFFERENT ISSUE.

THE 12Z GFS GENERATES UP TO A TENTH OF AN INCH OF QPF IN THE
NORTHERN HALF OF THE AREA TONIGHT...WHICH WAS A SIGNIFICANT CHANGE
FROM THE PREVIOUSLY DRY RUNS IN THAT AREA. IT APPEARS TO LATCH ON
TO SOME MINOR UPPER DIFFLUENCE IN A VERY STRONG UPPER LEVEL JET.
THIS SEEMS LIKE A VERY MINOR FEATURE AND THEREFORE I DO NOT HAVE
MUCH CONFIDENCE IN THAT SOLUTION...OPTING MORE FOR A MIDDLE OF THE
ROAD APPROACH FOR NOW...KEEPING A 50 POP IN THE NORTHERN ZONES FOR
TONIGHT. THE 18Z NAM HAS BACKED DOWN ON ITS QPF IN THE FAR SOUTH
AND SOUTHWEST...MORE INTO LINE WITH 12Z GFS QPF. GIVEN THE MODEL
DISCREPANCIES...DECIDED TO FOLLOW THE HPC QPF AND USE A 15 TO 1
RATIO TO GET SNOW GRIDS. THE MODELS ARE IN AGREEMENT IN HAVING
TEMPERATURES WELL INTO THE LOW TO MID 20S DURING THE
EVENT...LEADING TO THE HIGHER RATIO. SNOW AMOUNTS WILL RANGE FROM
UNDER AN INCH IN THE NORTH TO 1 TO 3 IN THE SOUTHERN HALF OF THE
AREA. CATEGORICAL POPS IN THE SOUTH LOOK REASONABLE.

ALL 12Z GUIDANCE IN AGREEMENT IN BRINGING A QUICK END TO THE
PRECIPITATION IN THE MORNING...AND CLEARING SKIES FROM THE NORTH
DURING THE AFTERNOON AND EVENING. MODELS ALSO IN GOOD AGREEMENT IN
SHOWING LITTLE REBOUND IN TEMPERATURES SATURDAY...LEADING TO VERY
COLD DAY WITH LOWS IN THE UPPER TEENS NORTH TO LOWER 20S SOUTH.
THE POTENTIAL SNOW COVER WILL MAKE TEMPERATURES INTO EARLY NEXT
WEEK VERY INTERESTING.

THE MODELS CONTINUE TO BE DRY OR MOSTLY SO...FOR SUNDAY THROUGH
MONDAY. THE GFS CONTINUES TO BRING SOME LIGHT QPF INTO FAR
SOUTHERN PORTIONS OF THE AREA SUNDAY NIGHT AND MONDAY...SO KEPT A LOW
POP FOR LIGHT SNOW THEN. THE MODELS SEEM TO HAVE FIGURED OUT THAT
THE ARCTIC HIGH IS STRONGER THAN PREVIOUSLY THOUGHT AND WILL NOT
ALLOW FOR SURFACE PRESSURE FALLS TO OUR EAST...AS PREVIOUSLY
ADVERTISED. DO NOT WANT TO PULL ALL MENTION OF THE EVENT AT THIS
TIME...GIVEN THE TREND IN THE LAST 24 HOURS ON TONIGHTS EVENT.

TEMPERATURES WILL BE BRUTALLY COLD SUNDAY MORNING AS THE SURFACE
HIGH SETTLES OVER THE AREA. IT WILL HANG OUT OVER US THROUGH MONDAY.

SHOULD SEE SINGLE DIGIT TEMPERATURES SUNDAY MORNING AND HIGHS ONLY
IN THE MID 20S SUNDAY AFTERNOON...DESPITE SOME SUNSHINE. WENT WITH
THE COOLER MET SUNDAY NIGHT AND UNDERCUT THE 12Z MEX FOR MONDAY.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...

NO PRECIPITATION IS EXPECTED MONDAY NIGHT INTO TUESDAY.  FOR TUESDAY
NIGHT...GFS BRINGS THE 0.01 QPF LINE INTO SOUTHERN PORTIONS OF THE
PAH FORECAST AREA.  BASED ON THE PLACEMENT OF A STATIONARY FRONT
ACROSS THE GULF COAST STATES...LOOKS LIKE ANY PRECIP PRODUCED FROM
OVERRUNNING WOULD STAY WELL SOUTH OF OUR REGION...SO KEPT FORECAST
DRY.  GFS THEN INDICATES A MID TO LATE WEEK PRECIP CHANCE AS THE
STATIONARY FRONT LIFTS NORTH AND A COLD FRONT APRROACHES FROM THE
NORTHWEST.  06Z GFS WAS MUCH QUICKER WITH THIS SYSTEM THAN THE
12Z...AND THE ECMWF LOOKS MORE SUPPORTIVE OF THE LATER TIMING OF
THE 12Z RUN. HOWEVER...DUE TO SUCH DRASTIC TIMING
DIFFERENCES...PREFER TO KEEP FORCAST DRY FOR NOW AND WAIT FOR SOME
RUN TO RUN CONSISTENCY BEFORE INTRODUCING POPS. BY THURSDAY NIGHT
AND FRIDAY...BOTH GFS AND ECMWF SHOW HIGH PRESSURE ACROSS THE
REGION.

12Z MEX TRENDING WARMER NEXT FOR NEXT WEEK.  OVERALL...WITH A COUPLE
OF EXCEPTIONS...WENT A LITTLE BELOW MEX GUIDANCE FOR TEMPS THROUGH
THE EXTENDED...PREFERRING A SLOWER MODERATION IN TEMPS DUE TO PRECIP
CHANCE UNCERTAINTIES.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
KY...SNOW ADVISORY FROM 10 PM THIS EVENING TO 8 AM CST SATURDAY FOR
     BALLARD-CALDWELL-HOPKINS-LIVINGSTON-LYON-MCCRACKEN-
     MUHLENBERG-CALLOWAY-CARLISLE-CHRISTIAN-FULTON-GRAVES-HICKMAN-
     MARSHALL-TODD-TRIGG.

MO...SNOW ADVISORY FROM 10 PM THIS EVENING TO 8 AM CST SATURDAY FOR
     BUTLER-CARTER-MISSISSIPPI-NEW MADRID-RIPLEY-SCOTT-STODDARD-
     WAYNE MO.

IL...SNOW ADVISORY FROM 10 PM THIS EVENING TO 8 AM CST SATURDAY FOR
     ALEXANDER-MASSAC-PULASKI.

IN...NONE.
&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PADUCAH KY
352 PM CST FRI FEB 17 2006

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-
100-107>112-114-181100-
JEFFERSON-WAYNE IL-EDWARDS-WABASH-PERRY IL-FRANKLIN-HAMILTON-
WHITE-JACKSON-WILLIAMSON-SALINE-GALLATIN-UNION IL-JOHNSON-POPE-
HARDIN-ALEXANDER-PULASKI-MASSAC-GIBSON-PIKE-POSEY-VANDERBURGH-
WARRICK-SPENCER-FULTON-HICKMAN-CARLISLE-BALLARD-MCCRACKEN-GRAVES-
LIVINGSTON-MARSHALL-CALLOWAY-CRITTENDEN-LYON-TRIGG-CALDWELL-
UNION KY-WEBSTER-HOPKINS-CHRISTIAN-HENDERSON-DAVIESS-MCLEAN-
MUHLENBERG-TODD-PERRY MO-BOLLINGER-CAPE GIRARDEAU-WAYNE MO-CARTER-
RIPLEY-BUTLER-STODDARD-SCOTT-MISSISSIPPI-NEW MADRID-
352 PM CST FRI FEB 17 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHERN
ILLINOIS...SOUTHWEST INDIANA...WESTERN KENTUCKY AND SOUTHEAST
MISSOURI.

.DAY ONE...THIS AFTERNOON AND TONIGHT

ONE TO THREE INCHES OF SNOW WILL BE POSSIBLE TO THE SOUTH OF A
LINE FROM PERRYVILLE MISSOURI TO CALHOUN KENTUCKY...MAINLY AFTER
MIDNIGHT TONIGHT. A SNOW ADVISORY HAS BEEN ISSUED FOR THE AREA
SOUTH OF A LINE FROM GREENVILLE MISSOURI TO GREENVILLE
KENTUCKY...WHERE 2 TO 3 INCHES WILL BE POSSIBLE.

NORTH WINDS WILL RESULT IN WIND CHILLS IN THE SINGLE DIGITS
THROUGHOUT THE REGION OVERNIGHT. THE WIND CHILL COULD APPROACH
ZERO AT TIMES.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE SNOWS WILL MOVE EAST OF THE AREA QUICKLY SATURDAY MORNING.
WIND CHILLS WILL BE IN THE SINGLE DIGITS THROUGHOUT THE REGION AT
TIMES SATURDAY AND SATURDAY NIGHT.

THERE IS A SMALL CHANCE OF LIGHT SNOW WITH MINOR ACCUMULATIONS
POSSIBLE SUNDAY NIGHT AND MONDAY...MAINLY IN THE SOUTHERN HALF
OF THE AREA.

.SPOTTER INFORMATION STATEMENT...

WE REQUEST THAT SPOTTERS AND OBSERVERS REPORT ANY SNOWFALL
ACCUMULATIONS TONIGHT AND EARLY SATURDAY.

DRS