[LeArc] Forecast Discussion : MLI@ 5/29/2003 3:31:30 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 292027
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 PM CDT THU MAY 29 2003

HIGH AMPLITUDE MID LEVEL FLOW IN PLACE TODAY WITH H5 RIDGE OVER THE 
ROCKIES AND SHARP H5 TROF OVER ERN FOURTH OF THE COUNTRY.
AT THE SURFACE RIDGE AXIS IS LOCATED OVER CENTRAL IA EARLY THIS 
AFTERNOON. WINDS STILL QUITE GUSTY EAST OF THE RIDGE AXIS IN 
RESPONSE TO PRESSURE GRADIENT NEAR EAST COAST SURFACE TROF.  CI SHIELD 
ASSOCIATED WITH S/W TOPPING RIDGE IN SW CANADA HAS SPREAD SOUTHEAST 
OVER THE MID MS VALLEY.  RADAR COMPOSITE SHOWING SOME SHRA/TSRA AHEAD
OF THIS SYSTEM FROM NW CORNER OF IA INTO CENTRAL SD.

MAIN CONCERN WILL BE THE SYSTEM DROPPING OUT OF WESTERN CANADA 
TONIGHT AND FRIDAY.  MODELS ARE IN GOOD AGREEMENT ON THE MOVEMENT OF 
THE SYSTEM WITH ETA SLIGHTLY DEEPER WITH THE SURFACE LOW THAN THE 
GFS BY FRIDAY MORNING.  CURRENT FCST HAS CHANCE POPS IN THE WEST 
AFTER MIDNIGHT TONIGHT WHICH LOOKS REASONABLE BASED ON INCREASING H8 
FLOW ACROSS THETA E RIDGE PROGGED TO MOVE FROM CENTRAL PLAINS INTO 
WRN IA BY LATE TONIGHT.  DIMINISHING H7-5 LAPSE RATES FURTHER E NR 
THE MS RIVER AND NORTHERN IL SUGGEST THAT SHRA/TSRA WILL DIE BEFORE 
REACHING ERN CWA BEFORE 12Z FRIDAY. HIGH CHANCE POPS WILL BE 
MAINTAINED OVER MOST OF CWA FRIDAY MORNING AHEAD OF THE SURFACE 
FRONT.  AT THIS TIME...WITH FRONT EXPECTED TO BE CROSSING THE MS 
RIVER AROUND 18Z...IT DOESN'T APPEAR THERE WILL BE MUCH OF SEVERE 
THREAT EXPECT IN THE FAR EAST DURING THE EARLY AFTERNOON. WIND WILL 
BE SOME CONCERN BEHIND THE FRONT...SIMILAR TO YESTERDAY.  LINEAR 
FLOW FROM SURFACE THRU H8 AND STEEP LOW LEVEL LAPSE RATES WILL ALLOW 
WINDS TO MAINTAIN THEIR MOMENTUM AS THEY MIX DOWN. NORTHERN SECTIONS 
OF THE CWA MAY ESCAPE THE STRONGER WINDS WITH MODELS SUGGESTING  H8 
WRAP AROUND MOISTURE SPREADING OVER THE AREA BY LATE AFTERNOON.  
REGION RETURNS TO BELOW NORMAL TEMPS FOR THE WEEKEND WITH A LARGE 
HIGH PRESSURE SYSTEM SETTLING IN.  LOOKS LIKE THE COOLEST NIGHT WILL 
BE SATURDAY NIGHT WITH META SUGGESTING H8 TEMPS MAY NEAR 4C.
WE COULD GET WITH IN A CATEGORY OR TWO OF RECORD LOWS FOR SUNDAY 
MORNING 6/1. RECORD LOWS RANGE FROM UPPER 30S NORTH TO LOW 40S 
SOUTH.  WILL INTRODUCE LOW CHANCE POPS FOR LATE SUNDAY NIGHT AHEAD 
OF NEXT SYSTEM MOVING IN FROM THE NW.  

EXTENDED...
BROAD MID LEVEL TROUGH IS ANCHORED OVER THE CENTRAL U.S. THROUGH THE 
PERIOD KEEPING TEMPS NEAR TO JUST BELOW NORMAL.  PCPN FORECAST QUITE 
TRICKY WITH MODELS SHOWING SEVERAL IMPULSES MOVING THROUGH THE 
TROUGH. BUT...AS WITH THIS TYPE OF PATTERN...TIMING DIFFERENCES 
EXIST...MAKING IT HARD TO PIN PRECIP CHANCES TO A SPECIFIC PERIOD. 
HAVE DECIDED TO KEEP PCPN CHANCES LIMITED TO MONDAY AND TUESDAY WITH 
GFS DEPICTION OF THE H3 JET KEEPING REGION SOUTH OF THE JET AXIS.  
BY WEDNESDAY PCPN THREAT DIMINISHES AS JET AXIS SAGS SOUTH  OF CWA.



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

$$

DLF