Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 202326 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 526 PM CST THU NOV 20 2014 .SHORT TERM...(TONIGHT THROUGH SUNDAY) ISSUED AT 315 PM CST THU NOV 20 2014 MAIN FORECAST PROBLEMS ARE PCPN CHANCES/PCPN TYPE FROM LATE FRIDAY AFTERNOON THROUGH SUNDAY AND TEMPERATURES THROUGH THE PERIOD. 500 MB PATTERN THIS MORNING FEATURED A BROAD LONGWAVE TROUGH ACROSS MUCH THE PACIFIC...A SMALLER SCALE TROUGH OFF THE WEST COAST OF WASHINGTON...OREGON AND NORTHERN CALIFORNIA AND A BLOCKING RIDGE FROM WESTERN CANADA NORTHWARD TO ABOVE THE ARCTIC CIRCLE. OUR AREA WAS IN MODEST NORTHWEST FLOW...WITH A LARGE TROUGH EXTENDING SOUTHWARD FROM HUDSON BAY INTO THE EASTERN UNITED STATES. TONIGHT INTO EARLY FRIDAY AFTERNOON...WE EXPECT IT TO BE MAINLY DRY AS THE RIDGE OF SURFACE HIGH PRESSURE CURRENTLY OVER THE AREA SHIFTS EASTWARD. 12Z NAM SNOWCOVER INITIALIZATION WAS NOT VERY GOOD...SHOWING HIGHER AMOUNTS OF SNOW ON THE GROUND IN OUR AREA THAN REALITY. SO SURFACE AND BOUNDARY LAYER PARAMETERS FROM THAT MODEL SHOULD BE USED WITH CAUTION IN THE SHORT TERM. WE WILL SEE SOME WEAK LOW LEVEL WARM AIR ADVECTION AND AN INCREASE IN LOW LEVEL MOISTURE. CLOUD COVER IS GOING TO BE TRICKY. BAND OF STRATOCUMULUS CLOUDS THAT EXTENDED FROM NORTHEAST NEBRASKA INTO SOUTHWEST IOWA SHOULD BREAK UP OR LIFT NORTH OVERNIGHT. SOME MID AND HIGH LEVEL CLOUDS WILL TRY TO SPREAD IN FROM THE WEST. IT IS POSSIBLE THAT SOME LOW CLOUDS MAY DEVELOP IN THE INCREASING SOUTHERLY LOW LEVEL FLOW...BUT A MORE SIGNIFICANT INCREASE IN LOW CLOUDS WILL OCCUR FRIDAY AFTERNOON. THE SHORTWAVE TROUGH CURRENTLY ALONG THE WEST COAST WILL DROP DOWN INTO THE FOUR CORNERS REGION BY FRIDAY EVENING...WHILE A WEAKER WAVE MOVES OVER MID AMERICA. A FEW OF THE MODELS ARE GENERATING LIGHT PCPN INTO FAR SOUTHEAST NEBRASKA AND SOUTHWEST IOWA BY LATE FRIDAY ...SO A SMALL CHANCE OF LIGHT RAIN WAS ADDED TO THE FORECAST FOR THAT. SOME PATCHY DRIZZLE POSSIBLE INTO THE LINCOLN AND OMAHA/COUNCIL BLUFFS AREAS MID TO LATE AFTERNOON. SURFACE TEMPERATURES AT THAT TIME SHOULD BE AT OR ABOVE FREEZING. IT APPEARS THAT THE STRONGEST FORCING FOR PCPN WILL STAY OFF TO OUR SOUTH AND EAST...BUT WE WILL KEEP SOME CHANCES GOING FOR ABOUT THE SOUTHEAST HALF OF OUR FORECAST AREA FRIDAY NIGHT INTO SATURDAY. THIS UNFORTUNATELY STILL LOOKS MESSY AS FAR AS PCPN TYPE GOES. SURFACE TEMPERATURES WILL BE THE KEY...SINCE PCPN FALLING WILL BE IN LIQUID FORM. RIGHT NOW IT DOES NOT LOOK LIKE A BIG IMPACT EVENT FOR MOST AREAS...SINCE AMOUNTS IF ANY WILL BE LIGHT. BUT...IT MAY BE ENOUGH TO CAUSE SOME PROBLEMS...ESPECIALLY FOR AREAS WITHIN ABOUT 20 MILES OF THE MISSOURI BORDER IF THEY ARE BELOW FREEZING. AGAIN...SURFACE TEMPS WILL BE THE KEY FACTOR. ENERGY IN THE NORTHERN STREAM TRACKING MAINLY ACROSS THE DAKOTAS MAY BE ENOUGH TO PRODUCE A BIT OF MIXED PCPN IN OUR FAR NORTHERN ZONES EARLY SUNDAY...SO THAT WAS ADDED. CURRENT TIMING SUGGESTS THAT LIGHT RAIN CHANCES IN THE SOUTHEAST PART OF THE FORECAST AREA WILL DECREASE A BIT BY SUNDAY AFTERNOON. TRENDED POPS DOWN A BIT BY LATE AFTERNOON ...BUT DID NOT GO COMPLETELY DRY. A FEW MODELS SUGGEST THAT IT COULD END UP BEING DRY THOUGH WITH NORTHWEST LOW LEVEL WINDS SUNDAY AFTERNOON. .LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY) ISSUED AT 315 PM CST THU NOV 20 2014 THE 12Z GFS/ECMWF/GEM AND ENSEMBLES ALL START OUT IN PRETTY GOOD AGREEMENT AT THE BEGINNING OF THIS PERIOD. THEY SHOW A RIDGE EXTENDING FROM NEAR 30N/130W NORTHWARD INTO THE YUKON...WITH A BROAD TROUGH FROM MANITOBA AND ONTARIO SOUTHWARD INTO TEXAS. IN GENERAL...THE RIDGE WILL TRY TO BUILD EASTWARD EARLY NEXT WEEK. THE MODELS DIVERGE CONSIDERABLY BY MID WEEK...AND SO CONFIDENCE DOES DROP OFF BY THAT TIME AS WELL. THIS IS SIMILAR TO WHAT THINGS LOOKED LIKE AT THIS TIME YESTERDAY. HIGHS WILL BE IN THE 30S MONDAY INTO WEDNESDAY BUT IT APPEARS THEY WILL SLIDE TOWARD THE 20S BY THURSDAY. LOWS ARE EXPECTED TO BE MOSTLY TEENS AND LOWER 20S BUT POSSIBLY A LITTLE COLDER TOWARD THURSDAY NIGHT. WILL KEEP THE PERIOD FROM TUESDAY INTO WEDNESDAY DRY FOR NOW...WITH A SLIGHT CHANCE OF SNOW FOR AT LEAST PARTS OF THE AREA WEDNESDAY NIGHT INTO THANKSGIVING DAY. && .AVIATION...(00Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 525 PM CST THU NOV 20 2014 A BAND OF LOW CLOUDS WERE JUST NORTHEAST OF KOMA AND KOFK AT 23Z AND WERE EXPECTED TO REMAIN AWAY FROM THOSE SITES...ALTHOUGH THERE IS A SMALL CHANCE THEY COULD SPREAD BACK IN FOR A FEW HOURS BEFORE WINDS TURN MORE SERLY LATER THIS EVENING/EARLY TONIGHT. WITH LIGHT WINDS AND FAIRLY MOIST LOW LEVELS...MVFR FOG WAS POSSIBLE AT TAF SITES LATER TONIGHT BEFORE WINDS INCREASE FRIDAY MORNING. A STRENGTHENING LOW LEVEL JET COULD PROVIDE LOW LEVEL WIND SHEAR CONDITIONS AT KOFK LATER TONIGHT AND THIS WAS MAINTAINED IN FORECAST. ON FRIDAY...A CONTINUED SRLY LOW LEVEL FLOW WAS EXPECTED TO BRING MVFR CIGS BACK ACROSS TAF SITES LATER FRIDAY AFTERNOON. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...MILLER LONG TERM...MILLER AVIATION...CHERMOK

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