FXUS63 KDMX 010436 AAB

AFDDMX



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE DES MOINES IA

1136 PM CDT SAT JUL 31 2010



...UPDATED AVIATION DISCUSSION...



.SHORT TERM /TONIGHT/...

WITH HIGH PRESSURE DRIFTING SEWD ACROSS IOWA TONIGHT...THE ONLY 

ISSUE IS HOW MUCH FOG WILL FORM. ABUNDANT SUNSHINE...WARMER 

TEMPERATURES AND NO RAINFALL TODAY MAKE THE CHANCES FOR FOG 

OVERNIGHT LESS THAN THEY WERE THIS MORNING. STILL...THERE IS A LOT 

OF LOW-LEVEL MOISTURE AND WEAK FLOW...SO SOME FOG IS LIKELY. 

NUMERICAL MODELS INDICATE THAT THE DEPTH OF THE MOISTURE WILL BE 

SOMEWHAT DEEPER EAST OF I-35...SO FOG IS EXPECTED TO BE MORE 

WIDESPREAD THERE AND LOCALLY DENSE FOG IS POSSIBLE. DUE TO THE LOCAL 

NATURE...DO NOT PLAN FOR A DENSE FOG ADVISORY AT THIS TIME...BUT IT 

WILL NEED TO BE MONITORED. 



.LONG TERM /SUNDAY THROUGH SATURDAY/...

SURFACE RIDGE OVER THE UPPER MIDWEST SUNDAY MORNING IS FORECAST TO 

MOVE SOUTHEAST DURING THE DAY. FLAT UPPER RIDGE WITH ITS AXIS OVER 

THE CENTRAL PLAINS SUNDAY AND SUNDAY NIGHT.  LEE THROUGH ACROSS THE 

PLAINS WITH SOUTHERLY FLOW EAST OF THE TROUGH SHOULD ADVECT MOISTURE 

NORTH INTO NEBRASKA AND THE NORTHERN PLAINS.  THUNDERSTORMS WHICH 

DEVELOP DURG PEAK HEATING SUNDAY AFTERNOON ARE FORECAST BY BOTH 

GFS/NAM TO IMPACT DMX CWA SUNDAY NIGHT AND MONDAY.  FOLLOWED THIS 

SCENARIO IN FORECAST WITH DECENT POPS.  BIGGEST SIGNIFICANT WEATHER 

RISK APPEARS TO BE MORE HEAVY RAIN.  REMNANTS OF SUNDAY NIGHT AND 

MONDAY MORNING MCS SHOULD HELP DETERMINE WHEN AND WHERE THE NEXT 

ROUND OF STORMS/MCS WILL BE MONDAY NIGHT AND TUESDAY.  SEEMS LIKELY 

THAT ANOTHER MCS WILL IMPACT THE STATE IN THIS TIME FRAME.  

OTHERWISE...IT SHOULD BE VERY WARM AND HUMID.  TEMPS ON MONDAY 

DIFFICULT DUE TO POSSIBLE MCS DEBRIS OVER CENTRAL IOWA.  LOWER MAX 

TEMPS A LITTLE. 



IN THE DAYS 4-7 RANGE /TUESDAY THROUGH SATURDAY/...UPPER RIDGE 

REMAINS ANCHORED OVER THE SOUTHERN CONUS WITH EARLY ZONAL FLOW 

ACROSS THE NORTHERN TIER STATES.  SURFACE BOUNDARY BETWEEN THE HOT 

AND HUMID AIRMASS TO THE SOUTH AND THE SLIGHTLY COOLER AIRMASS TO 

THE NORTH IS FORECAST TO BE NEAR IOWA.  THE 12Z GFS KEEPS SURFACE 

BOUNDARY JUST SOUTH OF IOWA WEDNESDAY THROUGH THURSDAY KEEPING 

SOUTHERN IOWA IN THE BEST SPOT FOR THUNDERSTORM CHANCES. 12Z GFS 

THEN BUILDS 500 MB HEIGHTS OVER THE UPPER MIDWEST BY LATE IN THE 

PERIOD.  LEE TROUGH AND SOUTHERLY FLOW OVER THE PLAINS SHOULD ADVECT 

THE HOT/HUMID AIRMASS NORTH INTO IA BY DAY SEVEN/SATURDAY/ AS THE 

FRONT MOVES NORTH AS A WARM FRONT. SHOULD SEE THUNDERSTORM ACTIVITY 

INCREASE ACROSS CENTRAL AND NORTH CENTRAL IOWA FRIDAY INTO SATURDAY 

AS WARM FRONT LIFTS NORTH. WARM TEMPS THROUGHOUT EXTENDED WITH 

WARMEST TEMPS ON DAY SEVEN PROVIDING THAT THE BOUNDARY DOES LEFT 

NORTH. USED THE OPERATIONAL GFS ALONG WITH HPC GUIDANCE TO BASE 

FORECAST. THE 00Z ECMWF SEEMS TO DEPRESS THE UPPER RIDGE TOO MUCH BY 

THE END OF THE FORECAST PERIOD. 





&&



.AVIATION...01/06Z

HIGH CLOUDS FROM CONVECTION OVER THE DAKOTAS HAVE PUSHED INTO 

CENTRAL TO NORTHERN IOWA AND LOOKS TO HINDER THE DENSE FOG 

DEVELOPMENT ACROSS THE AREA.  STILL WENT WITH MVFR TO IFR CONDITIONS 

FOR VIS FOR ALO/OTM/MCW AND MVFR FOR DSM AND FOD.  OTM VIS HAS COME 

DOWN A LITTLE AND WOULD EXPECT THIS SPOT SEE THE DENSE FOG FIRST AS 

HIGH CLOUDS STILL TO THE WEST.  OTHERWISE...CONTINUED WITH 12KT 

WINDS ACROSS THE NORTHERN TAF SITES DURING THE AFTERNOON HOURS 

SUNDAY. NO MENTION OF PRECIP IN TAFS YET AS NOT EXPECTING ANY UNTIL 

PAST 06Z MONDAY. 



&&



.DMX WATCHES/WARNINGS/ADVISORIES...NONE.



&&



$$



SHORT TERM...KJ

LONG TERM...JAJ

AVIATION...KLP