000  
FXUS63 KDVN 230534  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
1134 PM CST THU FEB 22 2018  
   
..AVIATION UPDATE
 
 
   
UPDATE
 
 
ISSUED AT 745 PM CST THU FEB 22 2018  
 
I HAVE ISSUED A SMALL WINTER WEATHER ADVISORY FOR OUR IOWA HIGHWAY  
20 COUNTIES THROUGH 6 AM. THE FORECAST FOR RISING TEMPS APPEARS TO  
BE CORRECT, BUT NOT UNTIL AFTER MIDNIGHT, THUS THE LIGHT  
RAIN/LIGHT SLEET/LIGHT DRIZZLE IS POSSIBLY FREEZING ON CONTACT TO  
UNTREATED ROADS IN THE FAR NORTHWEST. THE IOWA 511 WEBSITE REPORTS  
PATCHY SNOW OR ICE IN THAT AREA, AND WITH AIR TEMPERATURES NEAR  
32 THERE, THAT PROBABLY WILL NOT IMPROVE UNTIL LATER TONIGHT, AND  
AN ADVISORY SEEMS THE BEST APPROACH TO COVER THE LIGHT GLAZE ON  
UNTREATED ROADS THERE.  
 

 
   
SYNOPSIS
 
 
ISSUED AT 315 PM CST THU FEB 22 2018  
 
WARM AIR ADVECTION AND LOW LEVEL MOISTURE TRANSPORT WAS PRODUCING  
STRATUS AND PATCHY FOG. MID AFTERNOON TEMPERATURES HAVE RISEN INTO  
THE MID TO UPPER 30S. 3 HR PRESSURE FALLS OF 4 MB WAS NOTED ACROSS  
THE DVN CWA.  
 
SYNOPTICALLY, A DEEP UPPER LEVEL TROUGH WAS ANCHORED IN THE  
WESTERN UNITED STATES WITH A FAST SOUTHWEST FLOW ALOFT OVER THE  
MIDWEST.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY)  
ISSUED AT 315 PM CST THU FEB 22 2018  
 
FORECAST FOCUS ON LIGHT RAIN TONIGHT.  
 
TONIGHT: WEAK WAVE EJECTING OUT OF THE MAIN TROUGH WILL PROVIDE  
FORCING, AND ALONG WITH INCREASING MOISTURE, WILL SPREAD LIGHT  
RAIN INTO OUR WESTERN CWA BY EARLY TO MID EVENING, WITH THIS RAIN  
THEN PUSHING ACROSS THE REMAINDER OF THE CWA BY AROUND MIDNIGHT.  
THE RAIN IS EXPECTED TO CONTINUE FOR MOST OF THE NIGHT, BUT THEN  
END FROM WEST TO EAST LATE TONIGHT. BY SUNRISE THE RAIN SHOULD  
ESSENTIALLY HAVE EXITED THE DVN CWA, AS THIS WAVE LIFTS OFF TO THE  
NORTHEAST OF THE AREA. THIS FORECAST IS HEAVILY BASED ON THE  
HRRR/NAMNEST. RAINFALL AMOUNTS SHOULD GENERALLY BE IN THE RANGE OF  
ONE-TENTH TO ONE-QUARTER OF AN INCH. HOWEVER, THIS AMOUNT OF RAIN  
SHOULD NOT HAVE ADDITIONAL IMPACT ON RIVERS. I HAVE ALSO ADDED  
PATCHY FOG IN THE GRIDS. LOWS SHOULD BOTTOM OUT IN THE LOWER TO  
MID 30S.  
 
FRIDAY: A DRY DAY BUT PLENTY OF CLOUDS FOR MUCH OF THE DAY. THERE  
MAY BE SOME PARTIAL CLEARING IN THE NORTH DURING THE AFTERNOON.  
HIGHS WILL BE IN THE UPPER 30S TO MID 40S.  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 315 PM CST THU FEB 22 2018  
 
MAIN FORECAST CONCERN FOR THE LONG TERM IS THE SYSTEM AT THE  
BEGINNING OF THE PERIOD. A WINTRY MIX WILL GIVE WAY TO RAIN AND  
THUNDERSTORMS ON SATURDAY. ONCE THIS SYSTEM MOVES OUT OF THE AREA,  
TEMPERATURE WILL BEGIN TO WARM TO ABOVE AVERAGE.  
 
FRIDAY NIGHT INTO SATURDAY, THE MAIN H5 TROF IS FORECAST TO SWING  
THROUGH THE AREA. A RESPONSE IN THE LOW LEVELS WILL LEAD TO H85 WAA  
DURING THE DAY ON SATURDAY. DEPENDING ON THE MODEL, THE WARM SECTOR  
AND TRIPLE POINT EITHER TRAVELS THROUGH THE CWA OR JUST TO THE SOUTH  
OF THE CWA. REGARDLESS, OVERALL TEMPERATURES WILL WARM ABOVE  
FREEZING ACROSS THE AREA, MELTING ANY FROZEN PRECIP THAT HAS FALLEN.  
MAIN CONCERNS TURNS TO WHERE THE WARM SECTOR IS. WITH A DEEPENING  
SURFACE LOW, WINDS WILL BE BACKED NEAR THE WARM FRONT. BETWEEN 00Z  
SUNDAY AND 06Z SUNDAY THE H5 TROF TURNS NEGATIVE THIS WILL LEAD TO  
A STRONG WIND FIELD THAT SHOWS SPEED AND DIRECTIONAL SHEAR. IF  
CONVECTIVE UPDRAFTS CAN FORM IN THE WARM SECTOR AND THEN APPROACH  
THE WARM FRONT STORMS COULD ROTATE. THIS COULD LEAD TO A CHANCE FOR  
SEVERE WEATHER. THE LOCATION OF THE WARM FRONT AND TRIPLE POINT  
WILL BE THE LIMITING FACTORS AND WILL NEED TO BE WATCHED BY LATER  
SHIFTS.  
 
OVERALL RAINFALL TOTALS LOOK TO BE LIGHT WITH THIS SYSTEM. OVERALL  
TOTALS LOOK TO BE LESS THAN HALF AN INCH. THIS WILL LIKELY NOT  
AFFECT ANY OF THE CURRENT RIVER FLOODING. HOWEVER, IF THERE ARE  
THUNDERSTORMS THEN RAINFALL AMOUNTS COULD BE HIGHER. THUNDERSTORMS  
COULD LEAD TO MORE FLOODING.  
 
AFTER THIS TIME, TEMPERATURES WILL WARM AS SW FLOW LEADS TO WARM AIR  
ACROSS THE AREA.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)  
ISSUED AT 1129 PM CST THU FEB 22 2018  
 
VERY LOW CIGS AND VISIBILITIES IN LIGHT RAIN AND DRIZZLE WILL  
CONTINUE INTO THE NIGHT, WITH CIGS GENERALLY LESS THAN 500 FT AND  
VISIBILITY BETWEEN 1/4 MILE AND 2 MILES. AROUND 10Z THIS MORNING,  
WINDS WILL SWITCH TO SOUTH AND SOUTHWEST, USHERING IN DRIER AIR  
AND ENDING THIS FOG EVENT, LIKELY ALSO ENDING RAINS. BY MID  
MORNING FRIDAY, WINDS WILL BECOME NORTHWEST AND VFR WEATHER WILL  
RETURN TO THE REGION.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 213 PM CST THU FEB 22 2018  
 
FLOODING IS ONGOING IN THE ROCK RIVER AND WAPSI RIVER BASINS. WITH  
THE EXCEPTION OF COMO, ALL SITES ARE RISING. WITH THE FLOODING ON  
THE PECATONICA RIVER, YELLOW CREEK IS ALSO BACKED UP AND LEADING  
TO FLOODING. AS A RESULT AN AREAL FLOOD WARNING HAS BEEN ISSUED  
FOR YELLOW CREEK. THIS WILL LIKELY NEED TO BE CONTINUED UNTIL THE  
PECATONICA CRESTS AND STARTS TO DROP THROUGH THE WEEKEND.  
 
ON THE ROCK RIVER, A LONG ICE JAM RUNS FROM ERIE TO PROPHETSTOWN.  
THIS ICE JAM IS LEADING TO HIGH WATER AND IMPACTS ALONG THE RIVER.  
THIS WILL CONTINUE UNTIL THE JAM BREAKS. ICE WILL LEAD TO RAPID  
CHANGES IN THE RIVER. THOSE ALONG THE RIVER SHOULD PAY ATTENTION  
TO FUTURE FORECASTS.  
 

 
   
DVN WATCHES/WARNINGS/ADVISORIES
 
 
IA...WINTER WEATHER ADVISORY UNTIL 6 AM CST FRIDAY FOR BUCHANAN-  
DELAWARE-DUBUQUE.  
 
IL...NONE.  
MO...NONE.  

 
 

 
 
UPDATE...ERVIN  
SYNOPSIS...HAASE  
SHORT TERM...HAASE  
LONG TERM...GIBBS  
AVIATION...ERVIN  
HYDROLOGY...GIBBS  
 
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