FXUS63 KDVN 051309 CCA
AFDDVN
AREA FORECAST DISCUSSION...CORRECTED AVIATION SECTION...
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
710 AM CST SAT DEC 5 2009
.SYNOPSIS...
00Z UA ANALYSIS HAS THE COLD POOL ALOFT OVER THE MID MISSISSIPPI
VALLEY WITH A TROF MOVING ACROSS IOWA. SATELLITE TRENDS INDICATE THE
LAST OF THE LOW LEVEL CLOUDS ASSOCIATED WITH THE UPPER LOW WERE
ACROSS WISCONSIN AND NORTHEAST ILLINOIS. 06Z SFC ANALYSIS HAS HIGH
PRESSURE RUNNING FROM TEXAS INTO THE OHIO VALLEY WITH SOUTHERLY
RETURN FLOW FROM THE SOUTHERN PLAINS INTO THE WESTERN GREAT LAKES.
DEW POINTS WERE GENERALLY IN THE TEENS WITH SINGLE DIGITS ACROSS THE
PLAINS.
&&
.SHORT TERM...TODAY AND TONIGHT...
QUIET WX IS EXPECTED THE NEXT 36 HRS. WAA WILL SLOWLY MODERATE
TEMPERATURES TODAY AS CI/CS SLOWLY INCREASES DURING THE DAY. LOW
LEVEL LAPSE RATES DO BECOME STEEP ENOUGH ALONG/EAST OF THE
MISSISSIPPI THAT SHOULD PRODUCE SOME COLD WX SC.
DRY CONDITIONS WILL CONTINUE TONIGHT AS WAA CONTINUES. NET RESULT
WILL BE A CONTINUED INCREASE IN HIGH LEVEL CLOUDS WITH SOME MID
LEVEL CLOUDS BY SUNRISE. ..08..
.LONG TERM...SUNDAY THROUGH NEXT FRIDAY...
...LIGHT TO LOCALLY MODERATE SNOW ACCUMULATIONS LATE SUNDAY INTO
MONDAY...THEN A MAJOR WINTER STORM TUE/WED THE MAIN FORECAST
CHALLENGE...
OVERALL INITIALIZATION AND VERIFICATION AVERAGE WITH PACIFIC ENERGY
PHASING ISSUES AND CONVECTIVE FEEDBACK WITH SOUTH PLAINS STORM A
LINGERING QUESTION BEYOND DAY 3. NEAR TERM USED BLEND OF GEM-NHEM
AND GFS WITH FORCING FROM 80 KM NAM-WRF. BEYOND DAY 3...BLEND HI-RES
ECMWF AND GEM-NHEM WITH SOME FORCING FROM GFS. HENCE...FORECAST AREA
TO EXPERIENCE A MODERATE TO HIGH END WINTER STORM TUESDAY INTO
WEDNESDAY.
SUNDAY INTO MONDAY...WARM ADVECTION WING TOOL...OR /WAWT/ SUPPORTS
1 TO NEAR 3 INCH AMOUNTS OF SNOW ALONG AND NORTH OF I-80 WITH LIGHTER
AMOUNTS SOUTH. THUS...WENT CATEGORICAL POPS NORTH 1/3. 12Z NAM-WRF
QPF VALUES TOO HIGH DUE TO LATENT HEAT FEEDBACK ISSUES WITH 18Z RUN
SLIGHTLY BETTER. DECENT HIGH TEMPERATURE GRADIENT SUNDAY TO BE
IMPACTED BY ONSET OF SNOW WITH SNOW BEGINNING ALONG/NORTH OF HIGHWAY
30 BY EARLY AFTERNOON. ADDED PM POPS THERE WITH HIGHER POPS POSSIBLY
NEEDED NW 1/3 FOR DAY SHIFT TO CONSIDER. HIGH TEMPERATURE IN FAR SE
SECTIONS POSSIBLY MAY SEE HIGHS OF 40F. MOST PROLIFIC SNOWFALL SHOULD
OCCUR BETWEEN 00-09Z WITH SUGGESTED HIGHEST AMOUNTS NEAR 3 INCHES +/-
30 MILES ALONG A FREEPORT TO WILLIAMSBURG LINE BY MONDAY AM. A BIT
CONCERNED ABOUT MOISTURE PHASING ISSUES WITH FAST MOVING SHORT WAVE
THAT MAY IMPACT AXIS AND WIDTH OF SNOW AMOUNTS WITH POSSIBLE MULTIPLE
BANDING ISSUES FOR NEXT FEW SHIFTS TO MONITOR. SNOW SHOULD DISSIPATE
TO MAINLY FLURRIES BY MID MORNING LASTING INTO LATE MONDAY.
TEMPERATURES MAY ACTUALLY FALL DURING THE DAY DUE TO DECENT CAA.
NATURE OF FORCING WITH THIS EVENT MAY ALLOW FOR GREATER CHANGES IN
MODELS NEXT 24 HOURS WITH ISOLATED 4 PLUS INCH AMOUNTS POSSIBLE FROM
NEARLY STATIONERY BANDING. THIS WOULD SUPPORT AN ADVISORY.
MONDAY NIGHT...LOTS OF CLOUDS SUGGEST LIMITING MINS AND HAVE KEPT
LOWS HIGHER THAN GUIDANCE WITH SW FLOW ALOFT AND UPGLIDE. SOME
EVIDENCE MAY SEE ISOLATED FLURRIES FOR LATER SHIFTS TO CONSIDER
ADDING AHEAD OF DEVELOPING SOUTHERN PLAINS WINTER STORM.
TUESDAY AND WEDNESDAY...A MODERATE TO HIGH END WINTER STORM WILL MOVE
INTO AREA LASTING TIL LATE WEDNESDAY. HAVE HIGH END LIKELY POPS WITH
MOST TO ALL OF FORECAST AREA TO RECEIVE MODERATE TO HEAVY SNOW
AMOUNTS OF 4 TO LOCALLY 8 PLUS INCHES SUGGESTED. LATENT HEAT
FEEDBACK WILL GREATLY IMPACT RATE OF CYCLOGENESIS WITH CONCEPTUAL
MODELS SUGGESTING MOST MODELS HAVE LINGERING ISSUES WITH THIS. A
DECENT DEFORMATION ZONE WILL DEVELOP OR MOVE ACROSS FORECAST AREA AS
INTENSIFYING STRONG SURFACE LOW MOVES FROM SW MISSOURI INTO MICHIGAN.
WEDNESDAY...ADDED AREAS OF BLOWING SNOW TO FORECAST AS NW WINDS OF 25
TO 40+ MPH WITH GUSTS OVER 45 MPH TO PRODUCE NEAR BLIZZARD CONDITIONS
AT TIMES. THIS WILL MAKE FOR VERY DIFFICULT TRAVEL CONDITIONS. CLOSE
ANALYSIS STILL SUGGESTS PARTS OF FORECAST AREA MAY EXPERIENCE
BLIZZARD CONDITIONS WITH THIS SYSTEM AS SOME TECHNIQUES SHOW GUSTS
~50 MPH FOR NEAR WHITEOUT CONDITIONS. CURRENT TRENDS SUGGEST HEAVIEST
SNOW THREAT TO OCCUR OVER SOUTH 2/3 TO 3/4 SECTIONS WITH FURTHER
CLARIFICATION PROGGED NEXT 12-24 HOURS. STRONG WINDS MAY LINGER INTO
WEDNESDAY NIGHT WITH ADDITIONAL BLOWING OF SNOW. TEMPERATURES WILL BE
A CHALLENGE WITH SURFACE LOW TRACK AND RATE OF OCCLUSION THE KEY
PLAYER...WENT MILDER THAN MOST GUIDANCE WITH CRASHING TEMPERATURES
WEDNESDAY FOR LATER SHIFTS TO CONSIDER WITH WEDNESDAY HIGHS AT
TUESDAY MORNING LOWS. LOCAL HEAVY QPF AND FORCING TOOLS CONTINUE TO
SUGGEST A FOOT OR MORE OF SNOW REMAINS POSSIBLE WITH THIS SYSTEM.
WILL HIT WINTER STORM HARDER IN HAZARDOUS WEATHER OUTLOOK OF A HIGHER
END EVENT OF SNOW AND WIND TO HIT ALL OR MOST OF FORECAST AREA
TUESDAY AND WEDNESDAY. TRENDS CONTINUE TO SUPPORT SHOULD HAVE HIGH
IMPACT LOCATIONS AND ANY RISK OF THUNDER-SNOW CONFIRMED NEXT 12-24
HOURS. WEDNESDAY NIGHT...LOWS WITH SNOW COVER HAVE LOWERED WITH
INDICATIONS FROM CRASHING BL TEMPS LATER SHIFTS WILL NEED TO REDUCE
AT LEAST A FEW MORE DEGREES.
THURSDAY AND FRIDAY...NO CHANGES MADE...ALL INDICATIONS TEMPERATURES
NEED LOWERING AT LEAST AN ADDITIONAL 5 PLUS DEGREES WITH MINS BELOW
ZERO POSSIBLE AND HIGHS IN TEENS TO LOWER 20S. ..NICHOLS..
&&
.AVIATION...
VFR WX EXPECTED THROUGH 12Z/06. WAA WL BE SEEN ACRS THE AREA WITH
MAINLY HIGH LEVEL CLDS INCREASING. LOW LEVEL LAPSE RATES DO INCREASE
DURING THE DAY SO DIURNAL SC MAY BE SEEN AT KBRL/KMLI/KDBQ. WAA
CONTINUE AFT SUNSET WHICH WILL GRADUALLY INCREASE HIGH LEVEL AND
THEN MID LEVEL CLDS.
...08...
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
08/NICHOLS
