[LeArc] Forecast Discussion : MLI@ 1/16/03 2:03:11 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 160813
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
210 AM CST THU JAN 16 2003

.OVERVIEW...WINTER STORM NOW IMPACTING AREA WITH LEADING EDGE OF
PRECIPITATION EXTENDING FROM WILLIAMSBURG TO ROSEVILLE MOVING EAST
NORTHEAST AT 15 MPH.  NOWCAST TOOLS OF RADAR...SFC AND SATELLITE
SHOW SYSTEM TO AFFECT SOUTHERN 1/3 OF AREA FOR ANOTHER 6 HOURS AND
THE FAR SOUTH AS LONG AS ANOTHER 8+ HOURS.  SNOW ACCUMULATION TRENDS
UPSTREAM SUGGEST HIGHWAY 34 AND SOUTH TO EXPERIENCE 3 TO 6 INCHES
WITH LOCALLY HIGHER AMOUNTS POSSIBLE DEPENDING ON DEFORMATION ZONE.
WILL MONITOR FOR POTENTIAL UPGRADE TO WARNING CRITERIA.  UPPER AIR
SUGGEST ACTIVE PATTERN IN NW FLOW WITH UPSTREAM IMPULSES MOVING ALONG
BAROCLINIC ZONE.  HEIGHT RISES UPSTREAM SUGGEST CLEARING TOMORROW
LATE.

...STORM TOTAL AMOUNTS AND TIMING ENDING TO FLURRIES WITH POTENTIAL
WARNING DECISION NEAR TERM FORECAST ISSUE...

.DIAGNOSIS AND DAY 1-3...AVN BEST ON PRECIPITATION COVERAGE AT 06Z.
PLAN TO USE ETA FORCING WITH AVN AND MINOR INPUTS FROM RUC TRENDS
INTEGRATED WITH NOWCAST TOOLS. THIS CURRENTLY SUPPORTS NORTHERN EDGE
MAKING UP TO AROUND I-80 TOWARD DAYBREAK BEFORE SLIDING BACK SE.  FAR
SOUTH 1-2 ROWS OF COUNTIES TO SEE LONGEST PERIOD OF LIGHT TO
OCCASIONALLY MODERATE SNOW AT 20 TO 25 TO 1 RATIOS.   AT .25 TO .5
INCH PER HOUR ACCUMULATION RATES FOR ANOTHER 4-8 HOURS WITH 2 TO 3
INCHES ALREADY ON GROUND...LEADS TO STORM TOTALS OF 3-7 INCH AMOUNTS
THERE WITH LOCALLY HIGHER AMOUNTS.   SEE WHAT HAPPENS NEXT COUPLE
HOURS AS GET MORE REPORTS ON ACCUMULATION RATES...AGAIN MAY HAVE TO
BREAK OUT FAR SOUTHERN ONE OR TWO ROWS OF COUNTIES AND GO WITH A
WARNING WITH 4 AM PACKAGE.  THEN...CLEARING TO MOVE IN FROM NW WITH
MAY BE FLURRIES LEFT FAR SOUTH BY MID DAY. WILL THEN TRY AND
INCORPORATE SNOW TO LOWER TEMPS THERE NEXT COUPLE OF DAYS.
SATURDAY...STRONG UPPER SYSTEM SHOWN BY ALL MODELS SUGGESTS GOING
WITH LIKELY POPS WITH 850 TEMPS OF -10 TO -15C FOR 20 TO 25 TO 1
RATIOS...THIS SUPPORTS 1-2 INCH AMOUNTS WITH LOCALLY HIGHER AMOUNTS
WITH A POTENTIAL DEFORMATION ZONE COULD SEE SLIGHTLY HIGHER BUT
LIKELY WILL TAKE ANOTHER 24 HOURS OF SO FOR MODELS TO BETTER CAPTURE
AND THUS ASSESS THIS.

.EXTENDED (SUN-THU)...NW FLOW CONTINUES PER ALL MODELS WITH CHANCE
OF LIGHT SNOW ALMOST EVERY DAY WITH ANOTHER 3 WEAK TO MODERATE
STRENGTH ALBERTA CLIPPERS. MORE OMINOUS IS SUGGESTING OF REX OMEGA
BLOCK ALL NEXT WEEK OF ARCTIC AIR POOLING FOR EXTENDED COLD PERIOD
WITH ARCTIC AIR TRAPPED IN CENTRAL NA. PATTERN HAS BEEN CONSISTENTLY
SHOWN IN ONE FORM OR ANOTHER BY ALL MODELS FOR SEVERAL DAYS NOW...NOT
GOOD UNLESS LIKE COLD TEMPS.

.DVN...
IA...WINTER WEATHER ADVISORY THURSDAY AM ALONG AND SOUTH OF
HIGHWAY 34.
IL...WINTER WEATHER ADVISORY THURSDAY AM ALONG AND SOUTH OF
HIGHWAY 34.
MO...WINTER WEATHER ADVISORY THURSDAY AM.

NICHOLS