FXUS63 KILX 090523
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1123 PM CST TUE DEC 8 2009
.DISCUSSION...
ISSUED 845 PM CST TUE DEC 8 2009
DEEPENING LOW PRESSURE OVER CENTRAL MISSOURI STILL ON TRACK TO
PUSH ACRS CENTRAL IL BEFORE HEADING NE TWDS NE IL BY 12Z WED.
IMPRESSIVE 3 HOURS PRESS RISE/FALL COUPLET WITH SYSTEM INDICATING
SFC LOW WILL START TO TRACK FAIRLY QUICKLY TO THE NORTHEAST IN
THE NEXT SEVERAL HOURS. WATER VAPOR LOOP INDICATING MID LEVEL DRY
SLOT HAS PUSHED ACRS CNTRL IL PUTTING A TEMPORARY END TO THE
PRECIP. HOWEVER...AS THE SFC LOW AND NEGATIVELY TILTED 500 MB
TROF SWINGS ACRS OUR AREA AFTR MIDNIGHT...EXPECT AN INCREASE IN
PRECIP...ESP ACRS THE NW HALF OF THE FORECAST AREA. AFTER THAT...
WITH THE SFC LOW PULLING OFF TO OUR NE AND CONTINUING TO DEEPEN...
LOOK FOR STRONG GRADIENT WINDS TO SET IN...STARTING ACRS OUR
SW COUNTIES EARLY WED MRNG...AND THEN OVR THE REMAINDER OF THE
FCST AREA BY 12Z WED. WITH THE INCREASING WINDS WILL COME FALLING
TEMPS EARLY WED MRNG...SO ADDITIONAL SNOWFALL COUPLED WITH THE
RE-FREEZING OF ROAD SURFACES WILL MAKE FOR A DIFFICULT DRIVE INTO
WORK OR SCHOOL TMRW...ESP IN THE WARNING AND ADVSY AREAS.
BASED ON THE STRONG PRESSURE RISE TO THE REAR OF THE SFC LOW OVR
CNTRL MO...FEEL THE FRONT AND STRONGER WINDS MAY GET INTO AT LEAST
OUR SW AND SRN COUNTIES A BIT EARLIER THAN ORIGINALLY THOUGHT. AS
A RESULT...HAVE ADJUSTED THE START TIME UP A BIT EARLIER ON THE
WIND ADVSY TO 09Z. RATHER THAN TRY TO BREAK IT UP INTO SRN AND NRN
AREAS WITH DIFFERENT TIMES...DECIDED TO START ALL AREAS AT 09Z.
MAY NOT MEET ADVSY CRITERIA RIGHT AWAY IN THE NORTH AS IT WILL BE
CLOSER TO THE SFC LOW...BUT BTWN 09Z-12Z...AS THE LOW SHIFTS
FURTHER TO OUR NORTH...I WOULD THINK MOST AREAS SHOULD BE SEE THE
WINDS REALLY START TO INCREASE. AREAS OF SNOW AND BLOWING SNOW
ACRS THE NORTHWEST COUPLED WITH 45 MPH WINDS OVR MOST OF THE FCST
AREA...COUPLED WITH FALLING TEMPERATURES...WL MAKE FOR A MISERABLE
DAY ON WEDNESDAY. LATEST MODEL DATA INDICATES WE WON'T BE TOO FAR
FROM WIND WARNING CRITERIA (SUSTAINED 40 MPH+ FOR 1 HOUR...OR 58
MPH GUSTS FOR ANY DURATION).
SHOULD HAVE THE UPDTATED ZONES OUT BY 915 PM...AND WILL SEND OUT
THE UPDATED WIND ADVSY BY 945 PM.
&&
.AVIATION...
ISSUED 1115 PM CST TUE DEC 8 2009
LITTLE CHANGE FROM PREVIOUS THINKING. SFC LOW NOW NEAR QUINCY
EXPECTED TO TRACK TO NEAR CHICAGO BY 12Z. WINDS SHOULD REMAIN
LIGHT WITH THE LOW MOVING OVERHEAD OVER THE NEXT SEVERAL HOURS
BUT THAT WILL DRAMATICALLY CHANGE BY WED MRNG AS THE INTENSE
STORM SHIFTS AWAY FROM CNTRL IL. IFR/LIFR CIGS AND VSBYS WL
GRDLY LIFT TO BECOME MVFR CIGS BY TMRW AFTN INTO THE EVENING
HOURS. A BAND OF RAIN PUSHING IN WITH THE COLD FRONT WILL SWING
NE ACRS THE TAF SITES EARLY IN THIS FCST PERIOD WITH AREAS OF
SNOW DEVELOPING IN THE STRONG COLD ADVECTION LATE TNT INTO
WEDNESDAY.
SFC WINDS WILL SHIFT INTO THE SOUTHWEST AND THEN WEST LATE TNT
INTO WED MRNG WITH SPEEDS INCREASING TO 25 TO 35 KTS WITH A FEW
GUSTS ARND 40 KTS PSBL FROM WED MRNG INTO THE EARLY EVENING
HOURS...WITH A GRDL DECREASE IN WIND SPEEDS TMRW NIGHT AS THE LOW
SHIFTS QUICKLY AWAY FROM CENTRAL IL. VSBYS MAY BE CUT DOWN TO
AROUND A MILE FOR A BRIEF TIME WITH SCATTERED SNOW SHOWERS. IF WE
DO SEE ANY BLOWING SNOW...IT WOULD BE ARND THE PIA AND BMI AREAS
BUT FOR NOW...WITH MOSTLY RAIN OCCURRING AND ONLY GRDLY CHANGING
OVER TO SNOW OVERNIGHT...AND AMTS AN INCH OR LESS LOOKING MORE
LIKELY...WL KEEP ANY BLSN OUT FOR THE TIME BEING.
SMITH
&&
.PREV DISCUSSION...
ISSUED 300 PM CST TUE DEC 8 2009
THE WINTER STORM IS CONTINUING TO TAKE SHAPE THIS AFTERNOON...AS
THE SIGNIFICANT WARM AIR SURGES NORTH AHEAD OF THE LOW. SNOW HAS
CHANGED TO RAIN IN MOST AREAS SOUTHEAST OF THE IL RIVER...WITH A
MIX OF RAIN/FREEZING RAIN/SNOW NORTHWEST OF THE IL RIVER. THIS
PRECIPITATION TYPE PATTERN MAY SHIFT SLIGHTLY FARTHER TO THE NW
THIS EVENING...BUT NOT TOO MUCH. SOME PARTS OF KNOX COUNTY HAVE
RECEIVED 3 TO 4 INCHES OF SNOW SO FAR TODAY...BUT MOST AREAS IN
THE ADVISORY PICKED UP 1-2 INCHES.
THE MAIN CHANGE FROM THE PREVIOUS FORECAST HAS BEEN TO REDUCE THE
SNOW TOTALS EVERYWHERE...ESPECIALLY ON THE EASTERN EDGE OF THE
WINTER WEATHER ADVISORY AND WARNING. HAVE ALSO ADDED A MENTION OF
LIGHT ICING DUE TO THE INCREASING POTENTIAL FOR FREEZING RAIN
ALONG AND NORTHWEST OF THE IL RIVER.
STILL A MESSY WINTER SITUATION...SO WILL NOT ALTER THE WINTER
HEADLINES THIS AFTERNOON.
HOWEVER...WE HAVE DECIDED TO ISSUE A WIND ADVISORY FOR WEDNESDAY
FOR ALL OF OUR REMAINING COUNTIES NOT COVERED IN A WINTER
HEADLINE. THE WIND ADVISORY WILL RUN FROM 6 AM TO 6 PM WED...FOR
NW WINDS OF 30 MPH GUSTING TO 45 MPH. THE WINTER HEADLINE AREAS
WILL HAVE THEIR WORDING ADJUSTED ACCORDINGLY ON WEDNESDAY...AS THE
WIND BLOWN LIGHT FALLING SNOW CREATES HAZARDOUS WINTER CONDITIONS.
SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT.
ISENTROPIC LIFT HAS INTENSIFIED SIGNIFICANTLY THIS
AFTERNOON...WITH THE MID LEVEL WARM CONVEYOR BELT BLASTING INTO
CENTRAL IL FROM THE SOUTH. THIS HAS CAUSED MOST AREAS OF SNOW TO
CHANGE TO RAIN...EXCEPT FOR THE FAR NW ZONES.
TONIGHT...THERE WILL BE SUSTAINED SUPPORT OF INTENSE LIFT DUE TO A
COUPLED JET PATTERN DEVELOPING AT 300 MB. IL IS IN THE FAVORABLE
AREA FOR MAXIMIZED UPPER LEVEL DIVERGENCE AND RESULTANT STRONG
UVM...MAINLY LATE THIS AFTERNOON AND THIS EVE. HEIGHT FALLS ON
THE ORDER OF 30 DM/12 HR ARE ALSO EXPECTED...HIGHLIGHTING THE
DYNAMIC NATURE OF THIS SYSTEM. EAST OF JACKSONVILLE TO
BMI...RAINFALL RATES MAY BE HIGH ENOUGH TO CAUSE SOME STANDING
WATER IN LOW SPOTS AND IN POOR DRAINAGE AREAS. RAINFALL AMOUNTS
AROUND 1 INCH WILL BE POSSIBLE.
PRECIP TYPE IN THE WESTERN CWA TONIGHT IS STILL DIFFICULT TO
PINPOINT. THE LOW TRACK STILL LOOKS CLOSE TO THE PREVIOUS
FORECASTS FROM THE LAST DAY OR SO...BUT WARM AIR IS SURGING
FARTHER NORTH. IT APPEARS THAT NW KNOX/STARK COUNTIES WILL HAVE
THE BEST CHANCE TO HAVE MEASURABLE SNOW THIS EVENING...ALTHOUGH
PERIODS OF FREEZING RAIN WILL WORK TO REDUCE ANY SNOW ACCUMS.
GLAZING OF ELEVATED OBJECTS AND UNTREATED ROADS WILL BE POSSIBLE
IN THE WARNING AND ADVISORY AREAS. HAVE ADDED THAT TO THE MIX FOR
OUR WINTER HEADLINE PRODUCTS...AS IT COULD MAKE TRAVEL THAT MUCH
WORSE.
THE WARM SURGE WILL BEGIN TO PULL EAST AFTER 06Z. THAT WILL CAUSE
THE RAIN TO CHANGE TO SNOW FROM WEST TO EAST. SNOWFALL AMOUNTS OF
1 TO 2 INCHES WILL BE POSSIBLE MAINLY FROM LINCOLN AND
NORTH...WITH A DUSTING SOUTHWEST OF THERE. AREAS THAT RECEIVE JUST
RAIN ALL NIGHT...WILL STILL HAVE TO DEAL WITH FREEZING OF WET
ROADS AND WALKWAYS LATE TONIGHT AND WEDNESDAY.
A DRY SLOT WILL BLAST INTO EAST CENTRAL IL AFTER MIDNIGHT...WHICH
WILL WORK TO REDUCE OR END PRECIP IN THAT AREA FOR SEVERAL HOURS.
THE DEFORMATION ZONE SNOWS WILL EVENTUALLY WRAP INTO OUR N CWA
LATER TONIGHT...AS THE LOW PULLS INTO SW LOWER MICH. THAT SNOW WILL
EXPAND EASTWARD ON WEDNESDAY MORNING...AS WINDS INCREASE TO
ADVISORY LEVELS.
BLOWING SNOW MAY REDUCE VISIBILITY QUITE LOW...AS WINDS GUST OVER
40 MPH. AS MENTIONED EARLIER...WILL KEEP THE WINTER HEADLINES
THROUGH 6 PM WED TO COVER WINTRY TYPE CONDITIONS DUE TO BLOWING
SNOW. THE WIND ADVISORY WILL COVER THE REMAINING COUNTIES FOR
SIGNIFICANT WINDS CREATING ITS OWN HAZARDOUS TRAVEL. RE-FREEZING
OF ALL WET SURFACES COULD ALLOW THE WIND TO START VEHICLES
SLIDING.
TEMPS WILL SLOWLY FALL ALL DAY WEDNESDAY...WITH HIGH TEMPS ON
WEDNESDAY LIKELY TO BE AT MIDNIGHT.
BY WEDNESDAY NIGHT...AREAS NW OF THE IL RIVER WILL COME CLOSE TO WIND
CHILL ADVISORY CRITERIA...WITH READINGS DOWN TO -15F BETWEEN 5
AM AND 8 AM THURSDAY MORNING. LOW TEMPS WILL DIP INTO THE LOWER
SINGLE DIGITS...WITH NORTHWEST WINDS OF 15 TO 20 MPH.
LONG TERM...THURSDAY THROUGH TUESDAY.
NO MAJOR SYSTEMS ARE EXPECTED. THERE WILL BE A SLIGHT CHANCE OF
SNOW ON FRIDAY NIGHT/SAT...AS A SYSTEM PASSES BY TO THE SE OF IL.
THERE IS A SLIGHT CHANCE OF RAIN/SNOW MONDAY...AS A COLD FRONT
PASSES ACROSS THE AREA.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 3 AM TO 6 PM CST WEDNESDAY FOR ILZ038-042>057-
061>063-066>068-071>073.
WINTER WEATHER ADVISORY UNTIL 6 PM CST WEDNESDAY FOR ILZ029>031-
036-037-040-041.
WINTER STORM WARNING UNTIL 6 PM CST WEDNESDAY FOR ILZ027-028.
&&
$$
