[LeArc] Forecast Discussion : MLI@ 2/20/03 1:50:31 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 200759
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
155 AM CST THU FEB 20 2003

.OVERVIEW...SURFACE HIGH SLIDING EAST ALLOWING FOR MILDER SOUTHWEST
WINDS TO SET UP ACROSS AREA.  WEAK LEE SIDE TROUGH IN HIGH PLAINS
DEVELOPING SHOULD ALLOW FOR MORE WARM AIR TO MOVE IN ON STRENGTHENING
SW WINDS TODAY.  UPPER AIR SHOWS WESTERLY FLOW WITH SLIGHT RIDGING
SUPPORTING FAIR WEATHER NEXT 12-24 HOURS WHICH SATELLITE SUPPORTS.
STRONG CLOSED LOW DIVING INTO ARIZONA STARTING TO INTERACT WITH SUB
TROPICAL JET TO PRODUCE LOTS OF PRECIPITATION IN SOUTHERN PLAINS
WITH SOME POSSIBLY AFFECTING AREA ON FRIDAY.

...WARMUP NEXT TWO DAYS AND THEN WEEKEND POP POTENTIAL AND MAJOR COOL
DOWN WITH NEXT ARCTIC SYSTEM FORECAST ISSUES...

.DIAGNOSIS AND DAYS 1-3...WIDE VARIANCE IN MODELS IN HIGH ENERGY FLOW
AND PHASING ISSUES WITH SIGNIFICANT RUN TO RUN CHANGES.  ETA 2M TEMPS
REMAIN POOR DUE TO SNOW FEEDBACK PROBLEMS.  PERSISTENCE SUPPORTS
GOING CLOSE TO FWC IN SNOW FREE AREAS AND TREND 2-4 DEGREES BELOW
WHERE SNOW REMAINS.  PROFILERS AND LOTS OF SUNSHINE TODAY SUPPORT SW
WINDS OF 15 TO 25 MPH UNDER A MOSTLY SUNNY SKY SHOULD SEE TEMPS PUSH
NEAR TO JUST ABOVE 50 DEGREES IN SNOW FREE AREAS. SWATCH OF SNOW JUST
SOUTH OF I-80 LIKELY TO REMAIN IN MID TO UPPER 40S FOR ONE MORE DAY
BUT EXPECT ALL SNOW TO BE GONE BY MID DAY FRIDAY.  FRIDAY TO BE VERY
MILD UNTIL NEXT FRONT PASSES LATE IN THE DAY FRIDAY FROM NW.  THEN
COMES QUESTION OF POPS AS SW SYSTEM LIFTS NE...NGM AND UKMET MUCH
FURTHER NORTH ON PATH INTO OHIO VALLEY...THROWING SIGNIFICANT SNOW
INTO REGION WITH GFS-AVN AND ETA FURTHER SOUTH.  PHASING OF SHOT OF
VERY COLD ARCTIC OOZING SOUTH FROM CANADA FURTHER COMPLICATES
THINGS...ADD VIGOROUS SHORT WAVE FROM NW PACIFIC INTERACTING WITH
THIS ARCTIC MAKES FOR QUITE AN INTERESTING SPECTRUM OF CHOICES.  GFS-
AVN ENSEMBLE DO SUPPORT A NORTHWARD TRENDING OF SW US SYSTEM VERY
CLOSE TO UKMET AND NGM.  WILL TRY AND LOOK AT NEXT RUN OF ENSEMBLES
BEFORE ISSUANCE BUT FOR NOW PLAN TO INTRODUCE POPS FRIDAY NIGHT
ESPECIALLY SE PARTS AS LOW LEVEL THERMAL FIELDS ALSO SUGGEST THIS.
THEN TURNING COLDER WITH CHANCE OF SNOW SATURDAY AND SUNDAY.
INTERACTION OF NW IMPULSE WITH ARCTIC FRONT ALSO SUPPORT RISK OF MORE
SNOW.  WILL EMPHASIZE POTENTIAL FOR SOME ACCUMULATIONS AS ARCTIC AIR
FILTERS IN WITH HIGHER THAN NORMAL UNCERTAINTY DUE TO COMPLEX
INTERACTIONS IN NEXT HWO.

.EXTENDED RANGE(SUN-WED)...GFS-AVN AND UKMET BRING VERY COLD AIR IN
LATE SUNDAY AND MONDAY WITH LINGERING LIGHT SNOW AND FLURRIES.
VERY COLD TEMPS USHERING IN SUPPORT FALLING DAYTIME TEMPS LATE SUNDAY
INTO MONDAY AS 850 TEMPS OF -20C AND POSSIBLY AS COLD AS -28C MOVE
IN BY LATE MONDAY SO ONCE AGAIN EVEN WITH LITTLE OR NO SNOWCOVER...
SHOULD SEE LOWS IN SINGLE DIGITS TO BELOW ZERO.  NW WINDS OF AT
LEAST 15 TO 25 MPH SUGGEST WIND CHILLS OF 10 TO 20 BELOW OR LOWER
OR NEAR WIND CHILL ADVISORY CRITERIA.  COLD ARCTIC HIGH SLIDES EAST
BY WEDNESDAY WITH CHANCE OF SNOW AS WARM FRONT APPROACHES AND SLOW
WARMING.

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

$$

NICHOLS