FXUS63 KDVN 080925
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
325 AM CST TUE DEC 8 2009
.SYNOPSIS...
ANALYSIS AT 2 AM SUPPORTS MUCH ADVERTISED EXTREME WINTER STORM ON
TRACK. A LARGE SWATH OF MAINLY LIGHT SNOW HAS DEVELOPED ACROSS THE
FORECAST AREA AND EXTENDS SW BACK ALL THE WAY INTO NEW MEXICO.
THIS SUPPORTS THE HEAVIEST SNOW AMOUNTS WILL OCCUR AS LOW LEVELS
ALREADY SATURATED AND LOW LEVEL SURFACE LOW INTENSITY AND ITS PATH
ARE ON TRACK. INITIALIZATION AT 06Z SUPPORTS USAGE OF FORCING AND
MOISTURE FROM HI-RES ECMWF AND UKMET. THIS MEANS A NEAR PERFECT
HEAVY SNOW AND WIND EVENT. THE TRACK OF SURFACE LOW MOVES FROM NEAR
SGF TO UIN TO CHI WITH SYSTEM RAPIDLY DEEPENING TO ABOUT A 980 MB
LOW AT CHICAGO. COMPARED TO PAST CASES IN UPPER MIDWEST...THIS
WITH FORECAST GRADIENT AS SFC LOW MOVES NE SUPPORTS BLIZZARD
CONDITIONS LIKELY ON BACKSIDE OF LOW THE LATTER HALF OF TONIGHT
AND THROUGH THE DAY WEDNESDAY OF SUSTAINED 25 TO 40+ MPH WINDS
AND FREQUENT GUSTS NEAR TO ABOVE 50 MPH. ..NICHOLS..
&&
.SHORT TERM...TODAY AND TONIGHT...
ALL INDICATIONS REMAIN ON TRACK FOR A HIGH END...HIGH IMPACT MAJOR
WINTER STORM WITH POTENTIAL CRIPPLING WEATHER IMPACTS.
TODAY...HAVE KEPT HIGHS UPPER 20S NW TO LOWER 30S SE WITH 1 TO 5 INCHES
OF NEW SNOW. SNOW SHOULD FALL MOST OF THE DAY WITH HEAVY SNOW
MOVING INTO FAR SOUTH SECTIONS TOWARD DAYBREAK. EAST TO EAST
NORTHEAST WINDS OF 10 TO 20 MPH SHOULD ONLY CAUSE MINOR DRIFTING
OF SNOW. THE SNOW WILL ACCUMULATE ON MOST ROADWAYS AS SURFACE
TEMPERATURES REMAIN NEAR TO BELOW FREEZING. SLEET WILL MIX IN WITH
THE SNOW THIS AFTERNOON SE OF A PRINCETON TO GALESBURG TO
BURLINGTON TO MEMPHIS LINE. EVEN IN THESE AREAS...THERMAL PROFILES
SUGGEST THE HEAVIEST PRECIPITATION THERE SHOULD STILL FALL MAINLY AS
SNOW.
TONIGHT...ON TRACK FOR LOTS OF SNOW...SOME THUNDER-SNOW AND THEN
LOTS OF WIND AFTER MIDNIGHT. ONLY MINOR CHANGES MADE AS AMERICAN
MODELS AND EVEN OTHER MODELS SUPPORT A RAPIDLY DEEPENING...CLOSED
SYSTEM WITH FAVORABLE PROFILE FOR THUNDER-SNOW OVER AT LEAST SE
1/2 TO 2/3. SNOW ACCUMULATION RATES OF 1 TO 2 INCHES AN HOUR...COMBINED
WITH INCREASING WINDS WITH RISK OF GRAVITY WAVES WITH WIND GUSTS
OF 35 TO 45+ MPH...WILL MAKE FOR NEAR WHITEOUT CONDITIONS AT
TIMES...MAINLY AFTER MIDNIGHT. HEAVIEST SNOW SHOULD FALL +/- 40
MILES EITHER SIDE OF A FREEPORT TO CEDAR RAPIDS TO CHARITON IOWA
LINE. LOCATIONS ALONG AND NORTH OF A STERLING TO MOLINE TO MEMPHIS
LINE WILL LIKELY HAVE AT LEAST 8 INCHES ON THE GROUND WITH 10 TO
12 PLUS INCHES ON THE GROUND ALONG AND NORTH OF A MT CARROLL TO
FAIRFIELD AXIS. FAR SOUTH SE SECTIONS WILL HAVE 4 TO 9 INCHES ON
GROUND BY DAYBREAK.
OBJECTIVE METRICS INDICATE THIS SYSTEM WILL FALL INTO THE 3.5 TO 4.5
SIGMA RANGE FOR INTENSITY. THIS IS NEAR RECORD TO RECORD TERRITORY
MAINLY SUPPORTING LOTS OF WIND. ..NICHOLS..
.LONG TERM...WEDNESDAY THROUGH NEXT MONDAY...
INTENSE WINTER STORM WILL MOVE NORTHEAST ACROSS THE GREAT LAKES
WEDNESDAY. ECMWF/GEM HAVE BEEN BY FAR THE MOST CONSISTENT FOR NEARLY
5 DAYS NOW. BOTH INDICATE A DEFORMATION ZONE ACROSS THE AREA AT 12Z
WEDNESDAY WITH THE BACK EDGE ROUGHLY ALONG THE IA/MO BORDER. THUS
ACCUMULATING SNOW WILL CONTINUE THROUGH THE MORNING BEFORE STARTING
TO SHUT DOWN IN THE AFTERNOON. TEMPERATURES WILL FALL ALL DAY FROM A
HIGH RIGHT AROUND SUNRISE.
THIS STORM IS IMPRESSIVE. SNOW AMOUNT WISE...IT HAS BEEN ABOUT 10
YEARS SINCE SNOWS OF THIS MAGNITUDE AND EXPANSE HAVE BEEN SEEN.
STORM STRENGTH IS ANOTHER MATTER. BASED ON THE CURRENT FCST OF A
980MB OR BETTER SFC LOW...IT HAS PROBABLY BEEN 20 TO 30 YEARS SINCE
A WINTER STORM OF THIS MAGNITUDE HAS BEEN SEEN IN THE AREA.
WINDS WILL QUICKLY INCREASE ACROSS THE AREA WEDNESDAY MORNING. THE
MODELS HAVE TRENDED WIND SPEEDS LOWER. HOWEVER...THE MODELS DO A
POOR JOB OF HANDLING OR INCORPORATING NON-ADIABATIC PROCESSES AND
ISALLOBARIC WINDS. THUS THE WINDS WILL BE HIGHER THAN FCST BY THE
MODELS. THE MODELS HAVE BEEN VERY CONSISTENT IN INDICATING 25 TO 30
MB OF GRADIENT ACROSS IOWA FOR THIS EVENT. THE 00Z RUNS ARE PUSHING
30 MB. THEREFORE...SUSTAINED WINDS MINIMALLY OF 25 TO 40 MPH WITH
GUSTS LIKELY NORTH OF 50 MPH SHOULD BE SEEN. WINDS OF THIS MAGNITUDE
WILL PRODUCE WHITEOUT CONDITIONS.
SNOW TO END WEDNESDAY EVENING AND WINDS WILL GRADUALLY DIMINISH.
THERE IS A GOOD CHANCE THAT HEADLINES WILL NEED TO BE EXTENDED INTO
WEDNESDAY EVENING. SINCE THIS IS A HIGHLY NONLINEAR EVENT...WILL
DEFER THE EXTENSION TO THE NEXT SHIFT. THE CURRENT BLIZZARD WATCH
WILL REMAIN IN PLACE. THE MODELS CONTINUE TO TREND STRONGER SO THE
TRUE MAGNITUDE OF THIS EVENT IS NOT YET FULLY KNOWN.
ADDITIONAL HEADLINES FOR COLD WILL LIKELY BE NEEDED LATE WEDNESDAY
NIGHT INTO THURSDAY. HOWEVER...GIVEN THE MAGNITUDE OF THE CURRENT
EVENT...IT HAS BEEN DECIDED TO NOT ISSUE ANY ADDITIONAL HEADLINES IN
ORDER TO EMPHASIS THE SEVERITY OF THE WINTER STORM.
THURSDAY/FRIDAY...MINOR CHANGES WERE DONE TO MAX AND MIN
TEMPERATURES IN AN ATTEMPT TO ACCOUNT FOR THE DEEP SNOWPACK.
SATURDAY ON...NO CHANGES WERE MADE TO THE CURRENT FCST.
..08..
&&
.AVIATION...
MAINLY IFR TO BRIEF MVFR CONDITIONS THROUGH 21Z...THEN IFR TO LIFR THE
NEXT 24 HOURS. CEILINGS TO STAY AOB 1-2,000 AGL WITH VSBYS 1-2 MILES
IN LIGHT SNOW MOST OF TODAY FALLING TO BELOW 1 MILE AND CIGS BELOW
800-1,000 FEET BY 21Z IN LIGHT TO MODERATE SNOW. AFTER 21Z...CIGS
AOB 500 AND VSBYS 1/2 MILE OR LESS IN MODERATE TO HEAVY SNOW AND THEN
COMBINED WITH BLOWING SNOW AFTER 09Z. NEAR WHITEOUT TO WHITEOUT
CONDITIONS MOST OF WEDNESDAY. ..NICHOLS..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WARNING FROM 6 AM THIS MORNING TO 6 PM CST
WEDNESDAY FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DES
MOINES-DUBUQUE-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-
JONES-KEOKUK-LEE-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-
WASHINGTON.
BLIZZARD WATCH FROM LATE TONIGHT THROUGH WEDNESDAY AFTERNOON FOR
BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DES MOINES-DUBUQUE-
HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-JONES-KEOKUK-LEE-
LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.
IL...WINTER STORM WARNING FROM 6 AM THIS MORNING TO 6 PM CST
WEDNESDAY FOR BUREAU-CARROLL-HANCOCK-HENDERSON-HENRY IL-JO
DAVIESS-MCDONOUGH-MERCER-PUTNAM-ROCK ISLAND-STEPHENSON-
WARREN-WHITESIDE.
BLIZZARD WATCH FROM LATE TONIGHT THROUGH WEDNESDAY AFTERNOON FOR
CARROLL-JO DAVIESS-ROCK ISLAND-STEPHENSON.
MO...WINTER STORM WARNING FROM 6 AM THIS MORNING TO 6 PM CST
WEDNESDAY FOR CLARK-SCOTLAND.
BLIZZARD WATCH FROM LATE TONIGHT THROUGH WEDNESDAY AFTERNOON FOR
CLARK-SCOTLAND.
&&
$$
NICHOLS/08
