[LeArc] Forecast Discussion : MLI@ 2/9/03 12:50:06 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 091858
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1255 PM CST SUN FEB 9 2003

.OVERVIEW...ANALYSIS SHOWS BROAD UPPER AND SURFACE TROUGH OVER PLAINS
STARTING TO PRODUCE CLOUDS AND SOME LIGHT SNOW. THIS SYSTEM TO ROTATE
THROUGH TONIGHT.  WITH CONTINUED NW GENERAL JET FLOW...MOISTURE
REMAINS LIMITED AND WITH BROAD FORCING...LIGHT PRECIPITATION AMOUNTS
LOCATION THE KEY QUESTION.  SATELLITE SHOWS LOTS OF CLOUDS TO PASS
ACROSS REGION NEXT 24 HOURS.  SOUTH WINDS JUST NOW KICKING IN TO
ALLOW FOR MILDER CONDITIONS TIL NEXT ARCTIC SHOT ARRIVES EARLY MONDAY
BEHIND UPPER TROUGH PASSAGE.

...PRECIPITATION QUESTION TONIGHT AND EARLY MONDAY WITH COOL DOWN
NEAR TERM ISSUE...LATE WEEK SYSTEM MEDIUM RANGE QUESTION...

.DIAGNOSIS AND DAYS 1-3...LIGHT PRECIPITATION IN CENTRAL PLAINS HANDLED
BEST BY ETA/GFS-AVN.  ADDING NOWCAST TOOLS SUGGEST LIGHT SNOW AND
FLURRIES TO MOVE INTO MOST OF AREA TONIGHT RELATED TO DIFFUSE 850 MB
CONFLUENCE REGION OR FRONT.  AMOUNTS OF UP TO AN INCH ARE REASONABLE
WHICH CURRENT RADAR AND SURFACE TRENDS SUPPORT.  WILL MONITOR FOR ANY
CHANGES BUT FORCING NOT FAVORABLE AS OF 18Z...BUT WITH 15:1 RATIOS...
CHANCE MAY NEED TO ADD 1-2 INCHES AMOUNTS SOUTH SECTIONS.   THEN NEXT
ARCTIC SHOT TOWARD DAYBREAK MONDAY WITH TEMPS STEADY TO FALLING...AMOUNT
OF CAA AND SFC GRADIENT SUPPORTS BRISK NW WIND OF 15 TO 25 MPH. LOWS
TONIGHT WITH CLOUDS AND LIGHT PRECIPITATION AHEAD OF BOUNDARY 1-2
CATEGORIES ABOVE GUIDANCE ON SW WINDS.  DRY GROUND AND LIGHT SNOW COVER
WILL ALLOW FOR COLD TEMPS EARLY MONDAY NIGHT SO WILL TREND BELOW
GUIDANCE WITH LIGHT WINDS AHEAD OF NEXT SHORT WAVE. PLAUSIBLE THIS NEXT
SYSTEM TO BE A TAD SLOWER THAN MIX OF ETA/NGM/GFS-AVN/UKMET BASED ON 18Z
DATA. EITHER WAY...1-2 CATEGORIES BELOW REASONABLE WITH RISING TEMPS
LATE.  THEN WILL GO LIKELY POPS SOUTHERN 1/2 TO 2/3 WITH NEXT WEAK
CLIPPER SYSTEM.  DEPENDING ON FORCING WILL GO WITH LIGHT AMOUNTS
WORDING...OR FLUFFY 1-2 INCHES IN MOST LOCATIONS. TUESDAY WITH SW WINDS
WILL NEED TO BUMP TEMPERATURES BY SEVERAL DEGREES TO GO ABOVE GUIDANCE
BY 1-2 CATEGORIES...OR SIMILAR TO YESTERDAYS WARMUP BEFORE NEXT COOL
DOWN. PERSISTENCE VALUABLE TOOL IN THIS REGIME UNTIL FLOW CHANGES.

.EXTENDED (THU-SUN)...MODERATE CHANGE SUGGESTED BY MEDIUM MODELS OF
SOME ENERGY FROM SOUTHERN JET TO REACH AND CREATE A MORE VIGOROUS
CENTRAL PLAINS SYSTEM FRIDAY. WITH CONSISTENT NW FLOW PAST FEW
MONTHS...PLAN TO KEEP CHANCE POPS FOR ANOTHER DAY TO SEE EXACTLY HOW
MUCH SOUTHERN JET SYSTEM PHASES INTO OUR NW UPPER FLOW.  NEED AT LEAST
MODERATE AMOUNTS FOR LOW LEVEL MOISTURE AND NOT A COHERENT ENOUGH SIGNAL
AND BAROCLINIC REGIME SUGGESTING THIS FOR NOW AND THIS ALSO WOULD BE
AGAINST OUR PERSISTENT REGIME OF THE PAST FEW MONTHS.

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

$$

NICHOLS