[LeArc] Forecast Discussion : MLI@ 6/5/2003 4:55:58 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 052140
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
440 PM CDT THU JUN 5 2003

SYNOPTIC PICTURE THIS AFTERNOON SHOWS THE SURFACE THAT AFFECTED OUR
WEATHER FOR THE PAST FEW DAYS MOVING OFF THE MID ATLANTIC COAST.
MEANWHILE...A TROUGH IS SHARPENING UP ACROSS THE PLAINS.  AT 500MB
A GENERAL NORTHWEST FLOW CONTINUES...WITH TWO CLOSED LOWS...ONE OVER
SOUTH DAKOTA AND ONE OVER SASKATCHEWAN...HEADING OUR WAY.

THE MODELS AGREE ON THE PLAINS TROUGH WORKING INTO THE AREA ON
FRIDAY...SLOWLY AS IT DOES SO.  A LEADING VORT MAX WILL BRING A
GOOD CHANCE OF PRECIPITATION LATE TONIGHT...ESPECIALLY SOUTHWEST AND
WEST...WITH STRONG VV'S AND 300MB DIVERGENCE FROM 12Z TO 18Z...
EARLIER FAR WEST AND SOUTHWEST.  LESS VV'S AND 300MB DIVERGENCE IN
THE AFTERNOON...BUT STRONG PVA.  CLOUD COVER AND COOLER SURFACE
TEMPS MAY LIMIT CONVECTIVE ASPECT.

VORT AND ASSOCIATED POS OMEGAS TO PROPAGATE TO THE NORTHEAST FRIDAY
NIGHT...BUT SCATTERED CONVECTION MAY LINGER ACRS THE CWA UNTIL
MIDNIGHT...WANING AS THE NIGHT PROGRESSES WITH LOSS OF INSOLATION AND
ARRIVAL OF NVA. ETA AND GFS ARE THEN DRY ON SAT...EVEN THOUGH THEY
PROPAGATE ANOTHER VORT PIECE INTO THE AREA AND INTO AN INCREASING
UNSTABLE AIRMASS. UKMET SOMEWHAT SLOWER WITH ARRIVAL OF THE VORT...
BUT STILL BLEEDS CONVECTION INTO THE FAR WESTERN CWA IN THE
AFTERNOON. WILL SPURN THE ETA AND GFS AND INTRODUCE A CHANCE FOR A
SAT AFTERNOON SHOWER OR STORM(WIDELY SCATTERED IN NATURE)...WITH ALL
THE ABOVE FACTORS COMING TOGETHER. STILL WITH SOME INSOLATION BETWEEN
THE CLOUDS AND PROJECTED RATHER DEEP MIXING IN UNSTABLE
ENVIRONMENT...SAT AFTERNOON TEMPS SHOULD APPROACH 80 DEGREES.

NEXT LARGE SYSTEM/UPPER VORT TO THEN MAKE ITS WAY TOWARD THE AREA
OVERNIGHT SAT...WITH LATE NIGHT ARRIVAL STILL LOOKING ON TARGET...
TAKING INTO ACCOUNT SHORT RANGE ENSEMBLE OF FORCING AND SATURATION
PARAMETERS.

.LONGER RANGE(SUN-THU)...MEDIUM RANGE MODELS STILL HAVE THEIR
DIFFERENCES/PHASING ISSUES REGARDING THE HANDLING OF SUNDAYS
SIGNIFICANT CUT-OFF UPPER SYSTEM. LATEST ECMWF IS STILL THE FURTHEST
SOUTH WITH BOTH THE UPPER AND SFC SYSTEMS(ALMOST STACKED)AND ROLLS
THE SFC FEATURE ACRS FAR NORTHERN MO. THIS WOULD BRING HEAVY DEF ZONE
RAINS OVER THE LOCAL AREA...WHILE FURTHER NORTH PLACEMENT UKMET AND
MRF(SFC LOWS OVER NORTHERN IA AND MOVEMENT INTO SOUTHWEST WI)...
WOULD BRING MORE OF A CONVECTIVE LINE AND POSSIBLE SEVERE THREAT.
CURRENT ZONE WORDING SIDES WITH THE EURO...AND HAVE NO REASON TO
ALTER IT AT THIS POINT. WILL EAGERLY AWAIT FURTHER RUNS FOR HOPEFUL
CONSENSUS. STILL FEEL CUT-OFF UPPER SYSTEM WILL LINGER ENOUGH TO
CONTINUE SCATTERED SHOWER ACTIVITY WITH WRAP AROUND VORTS INTO
MONDAY...ALTHOUGH SOME MORE PROGRESSIVE MODELS(UKMET-XGFS) HAVE
TEMPORARY RIDGING AND A MAINLY DRY START TO THE WORK WEEK. WILL SIDE
WITH SLOWER EURO...WHICH LLVL THERMAL PARAMETERS AND CLOUD COVER
SUGGEST UNDERCUTTING LATEST MEX HIGHS. MEX HAS TRENDED COOLER THIS
RUN WITH MON HIGHS AS WELL. DEPENDS ON EVENTUAL PLACEMENT OF MAIN
LLVL WEST-TO-EAST THERMAL GRADIENT LAYOUT IN STRENGTHENING ZONAL FLOW
PATTERN...BUT AGREE WITH PREVIOUS SHIFT THAT THERE IS A POTENTIAL MCS
SET UP DEVELOPING FOR MID NEXT WEEK. EURO AND MRF OMINOUS FOR HEAVY
RAINS FOR THE LOCAL AREA TUE NIGHT AND WED...WHILE LATEST XGFS
HINTING AT FURTHER NORTH BAROCLINIC PLACEMENT.

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

$$

REA/12