416  
FXUS63 KOAX 201717  
AFDOAX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE  
1217 PM CDT MON AUG 20 2018  
   
UPDATE
 
 
ISSUED AT 1200 PM CDT MON AUG 20 2018  
 
THE FLASH FLOOD WATCH HAS BEEN EXTENDED THROUGH 7 PM. A NARROW  
BAND OF INTENSE RAINFALL IS EXPECTED TO CONTINUE OVER THE MISSOURI  
RIVER VALLEY THROUGH THE AFTERNOON. THIS INCLUDES THE OMAHA AND  
COUNCIL BLUFFS AREAS. AN ADDITIONAL 1-3 INCHES OF RAIN ARE  
POSSIBLE, AND WILL LIKELY EXACERBATE FLOODING ISSUES FOR AREAS  
THAT HAVE ALREADY SEEN 3 TO 9 INCHES OF RAIN IN THE LAST 24 HOURS.  
 

 
   
SHORT TERM
 
(TODAY THROUGH WEDNESDAY)  
ISSUED AT 322 AM CDT MON AUG 20 2018  
 
A MAJESTIC LOW PRESSURE SYSTEM WAS PROMINENT ON WATER VAPOR  
IMAGERY THIS MORNING, CENTERED OVER SOUTHEAST NEBRASKA/NORTHERN  
KANSAS. AT THE SURFACE, LOW PRESSURE DEEPENED OVER NORTHWEST  
MISSOURI. THE SURFACE LOW WILL CONTINUE TO ROTATE INTO  
SOUTHEASTERN IOWA THIS MORNING. MODERATE PRECIPITATION ASSOCIATED  
WITH THE DEFORMATION ZONE OF THIS SYSTEM CONTINUED A ALONG AND  
EAST OF THE MISSOURI RIVER THROUGHOUT SOUTHWEST IOWA OVERNIGHT.  
LATEST MODEL RUNS HAVE CONTINUED TO SHIFT HEAVIEST PRECIPITATION  
FURTHER EAST INTO SOUTH CENTRAL IOWA THROUGH THIS MORNING. WHILE  
MOST OF THE FORECAST AREA WILL LIKELY RECEIVE AT LEAST SOME  
RAINFALL THROUGH THE MORNING HOURS AS THE LOW ROTATES THROUGH,  
CURRENT GUIDANCE SUGGESTS GENERALLY ADDITIONAL ACCUMULATIONS OF 1"  
OR LESS CAN BE EXPECTED ACROSS MOST OF EASTERN NEBRASKA, WITH  
HIGHER AMOUNTS UP 3" ALONG AND EAST OF THE MISSOURI RIVER. OF  
COURSE LOCALLY HIGHER AMOUNTS MAY BE POSSIBLE, ESPECIALLY IN  
SOUTHWEST IOWA. BASED ON THIS NEW DATA, DECIDED TO TRIM FLASH  
FLOOD WATCH TO HIGHLIGHT THE MAIN THREAT EAST OF THE MISSOURI  
RIVER. SHOWERS WILL DIMINISH IN COVERAGE THIS AFTERNOON, WITH  
PRECIP FINALLY MOVING EAST OF THE FORECAST AREA MONDAY EVENING.  
 
IN ADDITION TO THE HEAVY RAINFALL, GUSTY WINDS WILL ALSO BE A FACTOR  
MONDAY. A STRONG LLJ APPROACHING 50KTS WILL MOVE THROUGH THE AREA  
THIS MORNING. ANTICIPATE GUSTS AROUND 30-40KTS COULD MIX DOWN AT  
THE SURFACE WITH ISOLATED STRONGER GUSTS PROBABLE. THE COMBINATION  
OF STRONG WINDS AND SATURATED SOIL COULD LEAD TO ISOLATED TREE  
DAMAGE. WINDS ARE EXPECTED TO DIMINISH ALONG WITH PRECIP AS THE  
SYSTEM MOVES OUT MONDAY EVENING.  
 
DRY WEATHER IS EXPECTED TUESDAY THROUGH WEDNESDAY. TEMPERATURES WILL  
REMAIN BELOW NORMAL, IN THE MID TO UPPER 70S BOTH DAYS, BUT WILL  
GRADUALLY WARM THROUGH MIDWEEK.  
   
LONG TERM
 
(WEDNESDAY NIGHT THROUGH SUNDAY)  
ISSUED AT 322 AM CDT MON AUG 20 2018  
 
TEMPERATURES WILL CONTINUE TO HEAT UP INTO THE 80S AND CLOSE TO 90  
BY THE WEEKEND. DRY WEATHER WILL CONTINUE THURSDAY BEFORE  
PRECIPITATION CHANCES INCREASE FRIDAY AS A SHORTWAVE MOVES THROUGH  
THE REGION. HIGH PRESSURE BUILDS ACROSS THE SOUTHEASTERN US OVER THE  
WEEKEND, BUT MODELS CONTINUE TO DIVERGE ON EXACT DETAILS. WHILE  
SATURDAY APPEARS TO REMAIN DRY, THE ECMWF DIFFERS FROM THE GFS,  
WHICH BRINGS AT LEAST A SLIGHT CHANCE FOR PRECIPITATION TO THE  
REGION ON SUNDAY.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)  
ISSUED AT 1215 PM CDT MON AUG 20 2018  
 
RAIN CONTINUES AT KOMA FOR ANOTHER 2-3 HOURS AND THEN BEGINS TO  
TAPER OFF BEFORE ENDING ALTOGETHER. SHOWERS IN THE VICINITY OF  
KOFK/KLNK, WITH MVFR CEILINGS, BECOMING VFR BY 21-22Z. VFR AT KOMA  
BY 21/00Z.  
 

 
   
OAX WATCHES/WARNINGS/ADVISORIES
 
 
NE...FLASH FLOOD WATCH UNTIL 7 PM CDT THIS EVENING FOR NEZ034-045-052-  
053-067-068-090-091.  
 
IA...FLASH FLOOD WATCH UNTIL 7 PM CDT THIS EVENING FOR IAZ043-055-056-  
069-079-090.  
 

 
 

 
 
UPDATE...ALBRIGHT  
SHORT TERM...KG  
LONG TERM...KG  
AVIATION...DEWALD  
 
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