[LeArc] Forecast Discussion : MLI@ 10/27/02 1:56:03 PM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 272004
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
200 PM CST SUN OCT 27 2002

.OVERVIEW...NEXT DISTURBANCE NOW MOVING INTO IOWA WITH COMMA SHAPED
PRECIPITATION SHIELD ADVANCING WITH LEADING EDGE EXTENDING FROM
NEAR MARSHALLTOWN TO NEAR OTTUMWA AT 19Z MOVING EAST AT ~15 MPH.
LATEST SFC OBS SUPPORT COLDER LOW LEVEL THERMAL FIELDS WITH SFC HIGH
IN NORTHERN CENTRAL IOWA KEEPING LOW LEVEL COOL WITH NO WAA POSSIBLE
NEXT SEVERAL HOURS. THIS IS ALLOWING RAIN TO MIX WITH AND CHANGE TO
SNOW MOST LOCATIONS ALONG AND NORTH OF INTERSTATE 80.  SOME SNOW IS
MIXED IN WITH RAIN AS FAR SOUTH AS MISSOURI BORDER.  FLOW PATTERN
SUPPORTS THIS TYPE OF PRECIPITATION MOVING EAST INTO EASTERN IOWA AND
WESTERN ILLINOIS NEXT SEVERAL HOURS.  17-19Z PRESSURE FALL AND RISE
PATTERN WITH SYSTEM DOES SUGGEST THIS PRECIPITATION TO WEAKEN
SOMEWHAT AS MOVES IT INTO OUR AREA. ON A LARGER SCALE...SOUTHWEST
FLOW CONTINUES TO PRODUCE OVERRUNNING ENVIRONMENT MOST OF CENTRAL US
WITH EASTERLY WINDS AND COLDER AIR AT SURFACE FOR DREARY CONDITIONS.

...PRECIPITATION TYPE AND AMOUNTS TONIGHT NEAR TERM ISSUE...MID
WEEK SYSTEM AND MORE PRECIPITATION TUESDAY INTO WEDNESDAY WITH
ASSESSING RISK FOR ADVISORY/WATCH/WARNING ON WEDNESDAY BEHIND COLD
AIR FOR SNOW...THEN NEAR RECORD TO RECORD COLD LATE WEEK.

.DIAGNOSIS AND DAYS 1-3...MODELS VERIFY ADEQUATELY ON LARGE SCALES
WITH NOWCAST TOOLS BEST GUIDE TONIGHT TO BLEND WITH ETA/RUC. THUS...
GO WITH CATEGORICAL POPS MOST OF IOWA AND EXTREME NW ILLINOIS.  TYPE
OF PRECIPITATION BASED ON OBS AT 19Z AND INTEGRATE 15Z RUC WITH ETA
SUGGEST SNOW ALONG HIGHWAY 20 WITH 1 INCH OR MORE IN GRASSY AREAS
TONIGHT.  ALONG AND NORTH OF HIGHWAY 30 SHOULD SEE SNOW...MIXED AT
TIMES WITH RAIN IN IOWA AND LIKELY POPS OF SNOW/RAIN MIXTURE IN
ILLINOIS.  THEN...RAIN MIXED AT TIMES WITH SNOW ALONG HIGHWAY 80 DOWN
TO HIGHWAY 34.  SOUTH OF 34...GO WITH LOWER POPS OF RAIN AND INTO
WEST CENTRAL IOWA BASED ON CURRENT FORCING TRENDS.  LOWS WITH
MOISTURE NEAR FREEZING EXCEPT HIGHWAY 34 AND SOUTH WHERE MID TO
UPPER 30S.  CLOUDY MONDAY WITH SOME MORNING DRIZZLE AND POSSIBLY
FLURRIES FAR NORTH.  MONDAY NIGHT NEXT SHORT WAVE WILL GO WITH HIGH
CHANCE POPS SOUTH AFTER MIDNIGHT AND SLIGHT CHANCE ALONG INTERSTATE
80 AFTER MIDNIGHT.  HIGH CHANCE TO LIKELY TUESDAY WITH CATEGORICAL
POPS OR RAIN MOST AREAS TUESDAY NIGHT.  LATE TUESDAY AND WEDNESDAY...
LITTLE CHANGE NEEDED AS WELL ADVERTISED SHORT WAVE AND STRONG COLD
FRONT WILL SEE RAIN CHANGE TO SNOW MOST AREAS IN MORNING WITH SOME
ACCUMULATION POSSIBLE ALONG AND NORTH OF HIGHWAY 34.  UKMET AND ETA
ARE VERY SIMILAR IN FORCING WITH AVN UPPER AIR ALSO SIMILAR BUT SFC
FEATURES OF AVN APPEAR TO HAVE PHASING PROBLEMS AND THUS NOT
APPLICABLE.  WILL KEEP STEADY TEMPS WEDNESDAY WITH STRONG CAA. TRENDS
SUPPORT FEW INCHES OF SNOW TO OCCUR WITH THIS SYSTEM...JUST LOCATION
STILL TBD AS MODEL FIDELITY WILL TAKE ANOTHER 24-36 HOURS (IF
THEN)...TONIGHT'S SYSTEM A GOOD EXAMPLE.  WINTER STORM WATCH POSSIBLE
NEXT 24 HOURS AS MODEL BEGIN TO PICK UP ON SMALLER SCALE FEATURES.

.EXTENDED (THU-SUN)...ALL MODELS SHOW UNSEASONABLY COLD AND LARGE
ARCTIC HIGH MOVING INTO AREA THROUGH SATURDAY... THIS WILL RESULT IN
NEAR RECORD TO RECORD COLD TEMPS.  WILL ADD RECORD VERBIAGE TO
EXTENDED PORTION OF ZONES WITH WARMUP STARTING SUNDAY.   THU/FRI...
UPPER TROUGH AND VERY COLD TEMPS OF -10 TO -15+C SUPPORT KEEPING
FLURRIES WORDING. WINTER IS ARRIVING.

COORDINATED WITH DSM...THANKS.

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

NICHOLS