000
FXUS63 KDVN 032057
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
255 PM CST WED DEC 3 2008
.SYNOPSIS...
ARCTIC COLD FRONT SLIDING EAST OF FORECAST AREA AT 2 PM WITH POST
FRONTAL BAND OF LIGHT SNOW TO EXIT EASTERN 1/3 AREA NEXT COUPLE HOURS
WITH ADDITIONAL ACCUMULATIONS LESS THAN AN INCH IN NW ILLINOIS.
TEMPERATURES FALLING INTO LOWER TO MID 20S ON GUSTY NW WINDS OF 15 TO
25 MPH PRODUCING SOME DRIFTING OF SNOW. REPORTS OF NEW SNOW TOTALS
FROM TODAY/S SNOW OVER REGION RUNNING A WIDESPREAD 1 TO 3 INCHES.
UPSTREAM SCATTERED FLURRIES NOTED ACROSS MN AND DAKOTAS WITH VERY
COLD TEMPERATURES UNDER ARCTIC HIGH MAINLY IN MID/UPPER TEENS. UPPER
AIR ANALYSIS SHOWS DIGGING UPPER TROUGH FROM SOUTH CENTRAL CANADA TO
ROTATE ACROSS FORECAST AREA NEXT 24 HOURS BRINGING VERY COLD AIR INTO
UPPER MIDWEST. GLOBAL UPPER AIR ANALYSIS SHOWS LARGE VORTEX OVER
NORTHERN CANADA WITH OMEGA BLOCK PHENOMENA EVIDENT SUPPORTING MAINLY
BELOW NORMAL TEMPERATURES WITH PERIODIC LIGHT SNOW WITH REINFORCING
SHOTS OF COLD AIR NEXT 7 DAYS WITH SUGGESTIONS COULD LAST UP TO 2
WEEKS. ..NICHOLS..
&&
.SHORT TERM...TONIGHT AND THURSDAY...
WILL CANCEL WINTER WEATHER ADVISORY BEFORE ZONE ISSUANCE AT 3 PM WITH
EXITING PRECIPITATION PER SYNOPSIS ABOVE. SKIES TO BECOME MOSTLY
CLEAR TO PARTLY CLOUDY SKIES BY MID EVENING WITH SOME SCATTERED
FLURRIES NORTH OF I-80 CORRIDOR AS ARCTIC AIR MAKES IMPACTS TO REGION
FELT WRINGING OUT ANY MOISTURE AS STRONG NEGATIVE FEEDBACK TO OCCUR
TONIGHT WITH 2 TO 5 INCH SNOW DEPTHS FROM LAST TWO SNOW EVENTS OVER
FORECAST AREA. LOWS TO BE 5 TO POSSIBLY UP TO 10 DEGREES BELOW
GUIDANCE BASED ON PERIODS OF CLEAR SKIES AND UPSTREAM DEWPOINTS IN
UPPER SINGLE DIGITS NOTED AT 2 PM. THURSDAY...COLD AND BRISK WITH
SOME MAINLY PM FLURRIES UNDER A PARTLY CLOUDY SKY WITH STRONG COLD
AIR ADVECTION ALOFT TO RESULT IN BL CONVECTIVE TEMPERATURES REACHED
WITH LOTS OF VIRGA FLURRIES AND NW TO WEST WINDS OF 10 TO 20 MPH.
KEPT HIGH/S ON LOW SIDE OF GUIDANCE WITH LOCAL TECHNIQUES SUGGESTING
HIGHS 20 TO 25 DEGREES NORTH TO SOUTH.
.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY...
GENERALLY BELOW NORMAL TO WELL BELOW NORMAL THROUGH PERIOD WITH LIGHT
SNOW FRIDAY NIGHT AND SATURDAY...
PREFER GFS AS HI-RES ECMWF AND UKMET HANDLING POORLY ENERGY OFF
CALIFORNIA. NAM-WRF ISSUES RELATED TO BL MOISTURE PROBLEMS WITH
ARCTIC AIR FOR TOO MOIST NEAR SFC IMPACTING TEMPS. MINOR CHANGES MADE
TO PACKAGE WITH CONSISTENT NW UPPER LEVEL FLOW WITH REINFORCING SHOTS
OF ARCTIC AIR SATURDAY/SUNDAY AND AGAIN TUESDAY/WEDNESDAY.
FRIDAY THROUGH SATURDAY...LOWS FRIDAY MORNING WENT WELL BELOW
GUIDANCE AS CLEAR SKIES AND LIGHT WINDS TO ALLOW MINS TO APPROACH OR
FALL BELOW ZERO. FRIDAY...SFC HIGH NEARBY AS MODEST BL MIXING
LIMITING HIGHS TO LOWER 20S. MODERATE STRENGTH ALBERTA CLIPPER TO
PASS FRIDAY NIGHT WITH JET AXIS SOUTH OF FORECAST AREA AND STRONG LOW
LEVEL JET TO ALLOW LIGHT SNOW OF AN INCH OR TWO FALL WITH WAA WING
SNOW. UPPED POPS TO 40 TO 50 WITH HIGHEST AMOUNTS NORTH OF I-80 WITH
NEARLY STEADY TEMPERATURES FRIDAY NIGHT AND AGAIN SATURDAY WITH
STRONG WAA OVERNIGHT AND THEN CAA DURING DAY SATURDAY. NIGHT SHIFT IF
TIMING CONFIRMED SHOULD BE ABLE TO UP TO LIKELY POPS IF SUGGESTING
TIMING REMAINS BETWEEN 06Z AND 12Z SATURDAY.
SATURDAY NIGHT THROUGH SUNDAY...LOWERED TEMPERATURES WITH SNOW COVER
SUGGESTING LATER SHIFTS WILL NEED TO LOWER AT LEAST A FEW MORE
DEGREES DUE TO NEGATIVE THERMAL FEEDBACK. DRY WITH MOSTLY CLEAR
SKIES AS ARCTIC AIR TO CONTINUE WELL BELOW NORMAL TEMPERATURES.
SUNDAY NIGHT THROUGH MONDAY NIGHT...LOW CHANCE POPS WITH ANOTHER
DIGGING SHORT WAVE WITH TEMPERATURES WITH STRONG WAA SUGGESTED TO
RISE TO NEAR NORMAL AND EVEN BRIEFLY SLIGHTLY ABOVE NORMAL AHEAD OF
NEXT ARCTIC AIR MASS. LIMITED MOISTURE TO AGAIN KEEP ANY SNOW
AMOUNTS LIGHT WITH EVEN COLDER AIRMASS TO SPILL INTO FORECAST AREA BY
WEDNESDAY WITH TEMPERATURES PROBABLY 5 TO 10 DEGREES COLDER THAN
FORECAST IF SUGGESTED 850 MB TEMPS OF -18-22C OCCUR. ..NICHOLS..
&&
.AVIATION...
BAND OF MODERATE SNOW BEHIND ARCTIC FRONT HAS MOVED EAST OF THE
MISSISSIPPI RIVER. LINGERING -SN OR FLURRIES UNTIL LATE AFTERNOON
FOR KMLI/KBRL. SNOW HAD ALREADY ENDED AT KCID/KDBQ. MVFR CIGS
FOR A TIME AFTER THE SNOW ENDS. SKIES WILL BE CLEARING FROM
NORTHWEST TO SOUTHEAST ACROSS THE TAF SITES AS THE EVENING
PROGRESSES. NORTHWEST WINDS 10-20 KNOTS WITH OCNL GUSTS NEAR 25 KNOTS
WILL ALSO DIMINISH THIS EVENING. ON THURSDAY BKN030 WITH SCATTERED
-SHSN OR FLURRIES WITH NORTHWEST WINDS 10 TO 15 KNOTS. ..HAASE..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
HAASE/NICHOLS
