[LeArc] Forecast Discussion : MLI@ 8/4/02 2:17:16 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 040719
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
218 AM CDT SUN AUG 4 2002

00Z UPPER AIR ANALYSIS CONTINUES TO SHOW BEST UPPER SUPPORT JUST
NORTH OF OUR WARNING AND FORECAST AREA.  DIFFLUENCE OVER NORTHWEST
IOWA AND SOUTHERN MINNESOTA WAS GOOD INDICATION OF OVERNIGHT
CONVECTION EVOLVING INTO HEAVY RAIN HYDRO EVENT.  SATELLITE AND 500
MB SHOW TROPICAL CONNECTION OF MOISTURE PLUME FEEDING INTO EXISTING
COMPLEX. MID 70 DEW POINT POOLING STILL IMPRESSIVE ACROSS OUR AREA...
BUT THIS MAY BE COUNTERED BY +12 700 MB TEMPERATURE WHICH WAS STILL
EVIDENT ON EVENING SOUNDING.  BROAD SURFACE BOUNDARY OVER SOUTHERN
MINNESOTA AND CENTRAL WISCONSIN HAS BEEN SLOW WITH ANY SOUTHWARD
PROGRESS BUT INCHING INTO NORTHERN IOWA.  INTERESTING TO NOTE THAT
APPARENT ANVIL LIGHTNING WAS INDICATED OVER EXTREME NORTH PART OF
FORECAST AREA...JUST NORTH OF HIGHWAY 20 ON THE IOWA SIDE OF THE
MISSISSIPPI...LONG BEFORE THUNDERSTORMS ARRIVED.

PRIMARY FORECAST CONCERN IN THE SHORT TERM WILL BE TIMING OF SLOW
SOUTHWARD PROGRESSING FRONTAL BOUNDARY INTO FORECAST AREA.  ALSO WILL
HAVE TO KEEP AN EYE ON HYDRO SITUATION AS SEVERAL OF OUR NORTH RIVERS
WILL BE TAKING IN SOME SIGNIFICANT RUNOFF.  WILL HAVE TO WATCH OUR
SOUTHERN ZONES AT MEETING HEAT ADVISORY CRITERIA.  PREVIOUS PACKAGE
ALREADY COVERED THE ADVERTISED COOL DOWN FOR MIDWEEK.

MODELS KEEP POSITIVE HEIGHT ANOMALIES OVER THE UPPER MISSISSIPPI
RIVER VALLEY.  MOST OF THE MODELS ARE COMING IN LINE...WITH
AMPLIFICATION OF EAST COAST TROUGH...AND LARGE DOME OF HIGH PRESSURE.
 THE AVN HAD ALREADY DONE A PRETTY GOOD JOB WITH THIS YESTERDAY.
WILL STICK WITH THE AVN AND ITS SLIGHTLY SLOWER ARRIVAL OF COOL AIR
PUSH INTO THE MIDDLE MISSISSIPPI RIVER VALLEY ON TUESDAY.

THIS MAY GO DOWN AS A DAY UP FORECAST UPDATES...BUT FOR NOW WILL GO
AHEAD AND BRING THE FRONT SOUTHWARD ACROSS OUR FORECAST AREA BETWEEN
18Z AND 00Z. WOULD EXPECT TYPICAL WEAKENING OF LOW LEVEL JET DURING
MID TO LATE MORNING HOURS...BUT SHOULD STILL BE ENOUGH DYNAMICS TO
KEEP HIGH CHANCE...50 POPS...IN MOST OF THE AREA.  WILL WAIT UNTIL
ISSUANCE TIME TO SEE IF...LIKELY...WORDING WILL BE NEEDED IN NORTH
ZONES.  WILL NOT GO WITH HEAT ADVISORY AT THIS TIME AS THINKING IS
THE FRONT AND DEBRIS CLOUDS WILL HELP HOLD HEAT INDEX READINGS JUST
BELOW CRITERIA.  THOUGH WE MAY HIT A FEW HIGH READINGS TODAY...WILL
LIKELY NOT HOLD ONTO REQUIRED OVERNIGHT 80+ INDEX READINGS.  IF THE
FRONT HANGS UP TO THE NORTH...THE DAY CREW MAY NEED TO ISSUE ONE.
ALL OF THE INGREDIENTS WILL REMAIN IN PLACE FOR ANOTHER RAIN EVENT
TONIGHT...BUT IN VICINITY OF THE COLD FRONT.  THOUGH UPPER SUPPORT
WILL NOT BE AS IMPRESSIVE AS WHAT WE HAVE TO THE NORTH NOW...
INDICATIONS ARE THAT COMPLEX MAY DEVELOP OVER SOUTHEAST NEBRASKA
SOUTHWEST IOWA REGION...WITH SOME CONVECTION POSSIBLE ALONG ENTIRE
FRONTAL BOUNDARY.  MY BEST SHOT AT RAINFALL LOCATION WOULD BE ALONG
AND NORTH OF HIGHWAY 34.

WILL MAKE NO CHANGES TO THE EXTENDED PACKAGE.  PREVIOUS PACKAGE
ALREADY HAS A GOOD HANDLE ON THE SURFACE HIGH SINKING FROM CANADA MID
TO LATE WEEK.

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

MEYER