828  
FXUS63 KOAX 241818  
AFDOAX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE  
1218 PM CST SAT FEB 24 2018  
   
SHORT TERM
 
(TODAY THROUGH MONDAY)  
ISSUED AT 349 AM CST SAT FEB 24 2018  
 
WINTRY PRECIPITATION TODAY IS THE PRIMARY FORECAST CONCERN, WITH  
WARMER TEMPERATURES ARRIVING JUST IN TIME FOR THE START OF THE WORK  
WEEK.  
 
A COMPLEX SCENARIO IS BEGINNING TO PLAY OUT THIS MORNING. FIRST,  
OPEN MID LEVEL WAVE WAS BEGINNING TO EMERGE FROM THE CENTRAL ROCKIES  
WITH A BROAD BAROCLINIC LEAF PATTERN SPREADING ACROSS WESTERN AND  
NORTH CENTRAL NEBRASKA AND INTO SOUTH DAKOTA AS SHOWN ON IR  
SATELLITE LOOPS. SATURATION OF MID LEVELS THERE WAS INTRODUCING ICE  
NUCLEI TO PRODUCE SNOW AS PRIMARY PRECIPITATION TYPE. THIS AREA  
IS EXPECTED TO SPREAD NORTHEAST ACROSS NORTHEAST NEBRASKA THROUGH  
THE DAY, PRODUCING SNOW THROUGH THE EVENT. FARTHER SOUTHEAST,  
DRIER MID LEVELS WILL INHIBIT SEEDER-FEEDER MECHANISM AS LOWER  
LEVELS BECOME INCREASINGLY MORE SATURATED THROUGH THE MORNING.  
TEMPERATURE PROFILES SUPPORT MAINLY SUPER-COOLED LIQUID DROPLETS  
FROM INTERSTATE 80 AND SOUTH THROUGH THE MORNING BEFORE SOME  
MOISTENING AND COOLING TOWARD -10C AT 700MB BECOMES LIKELY. THUS  
EXPECT MAINLY FREEZING DRIZZLE OR FREEZING RAIN IN THE SOUTHEAST  
HALF OF OUR CWA MUCH OF THE MORNING BEFORE SOME MIX WITH OR CHANGE  
TO SNOW OCCURS. AND IN THE FAR SOUTHEAST SECTIONS OF SOUTHEAST  
NEBRASKA AND SOUTHWEST IOWA, TEMPERATURES CLOSE TO 30 NOW WILL  
LIKELY INCH ABOVE FREEZING BY LATE MORNING, LIMITING ICING  
POTENTIAL THERE AFTER NOON.  
 
ALSO OF NOTE, DIFFLUENT MID LEVEL FLOW AHEAD OF APPROACHING  
SHORTWAVE WAS INDUCING STRONG INSENTROPIC UPGLIDE OVER COOL SURFACE  
AIR. WE WERE ALREADY SEEING AREAS OF FREEZING RAIN AS OF 3 AM IN  
SOUTHEAST NEBRASKA, AND THAT WAS SPREADING NORTH TOWARD THE OMAHA  
METRO AREA. RADAR RETURNS SUGGESTED SMALL CONVECTIVE ELEMENTS  
WITHIN THIS LARGER AREA OF RAIN/DRIZZLE, SO THERE WILL LIKELY BE  
SOME SLEET MIXED IN WITH THE BROADER AREA OF FREEZING  
PRECIPITATION.  
 
WITH ALL THAT SAID, WE WILL CERTAINLY CONTINUE OUR WINTER WEATHER  
ADVISORY ACROSS ALL OF EASTERN NEBRASKA AND SOUTHWEST IOWA. UP TO 3  
INCHES OF SNOW IS LIKELY IN NORTHEAST NEBRASKA, WITH A MIX OF ICING  
TOTALING OVER A TENTH OF AN INCH FOLLOWED BY UP TO AN INCH OF SNOW  
ALONG AND A COUNTY OR TWO EITHER SIDE OF INTERSTATE 80. ICING WILL  
BE THE PRIMARY THREAT IN FAR SOUTHEAST NEBRASKA AND FAR SOUTHWEST  
IOWA WHERE FORECAST SOUNDINGS KEEP MID LEVELS DRY THE LONGEST AND  
TEMPERATURE PROFILES WARMER THAN -10C. COULD SEE A TENTH OF AN INCH  
OF ICE THERE THIS MORNING, BUT WITH TEMPERATURES EXPECTED TO RISE  
ABOVE FREEZING THIS AFTERNOON, THE IMPACTS SHOULD DECREASE AFTER MID  
DAY.  
 
PRECIPITATION WILL BE SWINGING THROUGH EASTERN NEBRASKA THIS  
AFTERNOON, AND WILL BE WELL EAST OF SOUTHWEST IOWA EARLY THIS  
EVENING. SUBSIDENCE BEHIND EXITING WAVE AND LOW LEVEL WESTERLY  
FLOW SHOULD HELP TO CLEAR SKIES OVERNIGHT. COLDER AIRMASS WILL  
SETTLE OVER THE REGION TONIGHT, BUT NO WHERE CLOSE TO THE ARCTIC  
AND CANADIAN AIR MASSES WE'VE SEEN THE LAST SEVERAL WEEKS. 850  
TEMPS ONLY DROP INTO THE -2C TO -4C RANGE. STILL WITH CLEAR SKIES,  
LIGHT WINDS AND SOME NEW SNOW/ICE COVER, EXPECT TEMPS TO DROP  
INTO THE TEENS MOST AREAS BY SUNDAY MORNING.  
 
A WEAK MID LEVEL SHORTWAVE IS FORECAST TO PROGRESS THROUGH THE  
REGION ON SUNDAY, BUT WITH LACK OF SIGNIFICANT MOISTURE AND LIFT,  
DON'T EXPECT PRECIPITATION. HOWEVER VARIABLE CLOUD COVER WILL LIMIT  
WARMING SOMEWHAT, AND COOL 850 TEMPS REMAIN IN PLACE. SO DESPITE A  
FAVORABLE SOUTHWEST LOW LEVEL WIND COMPONENT, EXPECT HIGHS IN THE  
30S FOR MOST OF THE AREA, WITH LOWER 40S IN SOUTHEAST NEBRASKA AND  
SOUTHWEST IOWA.  
 
MONDAY IS ANOTHER STORY AS MID LEVEL HEIGHTS BEGIN TO RISE IN THE  
WAKE OF EXITING SUNDAY SHORTWAVE AND AHEAD OF DEEPENING TROUGH IN  
THE WEST. INCREASED SOUTH TO SOUTHWEST LOW LEVEL FLOW IS ALSO  
EXPECTED AS A RESULT OF STRONG SHORTWAVE MOVING ACROSS THE CANADIAN  
BORDER. 850 TEMPS GAIN ABOUT 5C BY MONDAY AFTERNOON UNDER PLENTY OF  
SUNSHINE. MODEL OUTPUT HAS BEEN PERSISTENT IN SHOWING 50S FOR THE  
SOUTHERN HALF OF OUR CWA AND 40S IN THE NORTH, AND SEE NO REASON TO  
DOUBT THAT NOW.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 349 AM CST SAT FEB 24 2018  
 
TEMPERATURES ARE EXPECTED TO AVERAGE CLOSER TO NORMAL FOR THE  
REMAINDER OF THE WEEK, WITH A CHANCE FOR PRECIPITATION COMING  
WEDNESDAY INTO THURSDAY. OVERALL MID LEVEL FLOW PATTERN WILL  
INITIALLY FEATURE A TROUGH IN THE WEST FOR TUESDAY WITH SOUTHWEST  
FLOW ALOFT ACROSS THE PLAINS. A COLD FRONT TRAILING THE STRONG  
SHORTWAVE MOVING ALONG THE CANADIAN BORDER MONDAY WILL SLIDE INTO  
OUR REGION ON TUESDAY. TIMING OF THIS FRONT HAS SLOWED WITH THE  
LATEST MODEL RUNS, SUGGESTING OUR SOUTHERN CWA WILL STAY ON THE  
WARMER SIDE OF THE BOUNDARY ON TUESDAY. A 30 DEGREE SPREAD IN HIGH  
TEMPERATURES FROM NORTHEAST NEBRASKA INTO SOUTHWEST IOWA AND  
SOUTHEAST NEBRASKA COULD OCCUR THEN, WITH 30S HIGHS IN THE NORTH AND  
60S IN THE SOUTH. WE SLIP TO THE COLDER SIDE OF THE FRONT FOR  
WEDNESDAY AND THURSDAY WHEN THE WESTERN TROUGH EJECTS INTO THE  
PLAINS AS AN OPEN WAVE. TEMPERATURE PROFILES THEN SUGGEST A VARIETY  
OF PRECIPITATION TYPES ARE POSSIBLE, BUT WOULD FAVOR SNOW IN OUR  
NORTH AND RAIN IN OUR SOUTH INITIALLY ON WEDNESDAY BEFORE CHANGING  
TO ALL SNOW WEDNESDAY NIGHT. STILL A WAY OUT FOR THIS ONE, BUT WITH  
THE SPEED OF THE SYSTEM, NOT LOOKING AT A MAJOR EVENT.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)  
ISSUED AT 1209 PM CST SAT FEB 24 2018  
 
A LIGHT WINTRY MIX OF PRECIPITATION WILL CONTINUE TO MOVE THROUGH  
REGION THIS AFTERNOON. LOWER CIGS HAVE BEGUN TO SCATTER OUT NEAR  
KOFK. OTHERWISE, IFR AND LIFR CONDITIONS PERSIST AT KLNK AND KOMA  
UNTIL THE REMAINDER OF THE PRECIPITATION MOVES OUT AROUND 00Z.  
WINDS WILL REMAIN LIGHT AND VARIABLE THROUGH THE PERIOD, BECOMING  
MORE WESTERLY AS CONDITIONS IMPROVE THIS EVENING.  
 

 
   
OAX WATCHES/WARNINGS/ADVISORIES
 
 
NE...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR NEZ011-  
012-015>018-030>034-042>045-050>053-065>068-078-088>093.  
 
IA...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR IAZ043-  
055-056-069-079-080-090-091.  
 

 
 

 
 
SHORT TERM...DERGAN  
LONG TERM...DERGAN  
AVIATION...KG  
 
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