Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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534 FXUS63 KOAX 122321 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 521 PM CST FRI FEB 12 2016 .SHORT TERM...(TONIGHT THROUGH MONDAY) ISSUED AT 324 PM CST FRI FEB 12 2016 COLD TEMPERATURES TO START THE WEEKEND AND A CHANCE FOR LIGHT SNOW SATURDAY AND SUNDAY ARE THE PRIMARY FORECAST CONCERNS. ARCTIC HIGH PRESSURE CHARACTERIZED BY DOUBLE DIGIT SUB ZERO TEMPERATURES OVER EASTERN SASKATCHEWAN THIS MORNING IS FORECAST TO RIDE SOUTHEAST INTO THE MID MISSOURI RIVER VALLEY AND IOWA LATER TONIGHT. PERSISTENT NORTH OR NORTHEAST LOW LEVEL FLOW WILL CONTINUE TO DRY SURFACE LAYER AS SUB ZERO DEW POINTS ARE ADVECTED INTO AT LEAST THE EASTERN HALF OF OUR CWA. THIS WILL SET THE STAGE FOR A POTENTIALLY VERY COLD NIGHT TONIGHT. HOWEVER A COUPLE OF CAVEATS ARE NOTED THAT MAY HOLD TEMPS FROM BOTTOMING OUT...THAT BEING INCREASING MID LEVEL CLOUDS OVER OUR AREA...AND COLDEST TEMPS IN THERMAL TROUGH SETTING UP TO OUR EAST. WINDS WILL NOT GO CALM EITHER...WHICH WILL HELP SOMEWHAT. EXPECT LOWS TO DROP BELOW ZERO IN PARTS OF WEST CENTRAL IOWA AND A PART OF NORTHEAST NEBRASKA...WHILE REMAINING IN THE SINGLE DIGITS ABOVE OVER THE REST OF THE AREA. THE INCREASING MID LEVEL CLOUDS EXPECTED LATER TONIGHT WILL BE IN RESPONSE TO LOWERING SURFACE PRESSURES IN THE HIGH PLAINS AHEAD OF APPROACHING STRONG SHORTWAVE RIDING THROUGH THE NORTHERN ROCKIES. ISENTROPIC UPGLIDE WILL INCREASE MARKEDLY AFTER MIDNIGHT IN NORTH CENTRAL NEBRASKA AND GRADUALLY SPREAD EAST AND SOUTHEAST THROUGH DAYBREAK. LAYER MOISTURE LOOKS SOMEWHAT PALTRY OVER A GOOD PART OF EASTERN NEBRASKA UNTIL THEN GIVEN LOW LEVEL DRY FLOW. HOWEVER THE WESTERN PARTS OF NORTHEAST NEBRASKA COULD SEE SUFFICIENT SATURATION BEFORE DAYBREAK FOR LIGHT SNOW THERE. CORE OF LIFT ASSOCIATED WITH UPGLIDE WILL RIDE EAST ACROSS THE NORTHERN PART OF THE CWA DURING THE DAY. SURFACE WINDS WILL TURN SOUTHERLY DURING THE DAY AS NORTHERN ROCKIES SHORTWAVE BEGINS DIVING INTO THE PLAINS. STRONG WARM ADVECTION AHEAD OF THIS FEATURE SHOULD KEEP LIGHT SNOW CHANCES GOING FOR OUR NORTHERN AND EASTERN CWA SATURDAY EVENING...BUT BEST THETA-E COINCIDENT WITH FORCING WILL REMAIN TO THE LEFT OF VORTICITY MAXIMUM...WHICH DIVES THROUGH EASTERN SOUTH DAKOTA INTO CENTRAL IOWA SATURDAY NIGHT INTO SUNDAY MORNING. THUS BEST CHANCE FOR ACCUMULATING SNOW WILL OCCUR ALONG OUR NORTHEAST COUNTIES WHERE WE HAVE AN INCH OR SO FORECAST. WILL POTENTIALLY STILL SEE LIGHT SNOW OVER MUCH OF THE CWA SATURDAY NIGHT GIVEN STRONG WARM ADVECTION/UPGLIDE. STRONG NORTHWEST WINDS WILL FOLLOW SHORTWAVE SUNDAY AFTERNOON LEADING TO DECENT MIXING REGIME ACROSS THE CWA...ALONG WITH DECREASING CLOUDS. BASICALLY NEUTRAL TEMPERATURE ADVECTION IS NOTED HERE...WITH CORE OF COLD ADVECTION SPREADING ACROSS CENTRAL IOWA. EXPECT NORTHEAST PART OF THE CWA WILL STRUGGLE TO CLIMB OUT OF THE 20S...BUT DECREASING INFLUENCE OF SNOW COVER FARTHER WEST WILL ALLOW ADIABATIC WARMING TO PUSH TEMPS TOWARD THE LOWER 40S...ESPECIALLY IN OUR SOUTH WHERE BARE GROUND EXISTS. SOUTHWEST WINDS AND SLOWLY RISING MID LEVEL HEIGHTS/TEMPERATURES SUGGESTS MONDAY SHOULD BE EVEN WARMER...WITH HIGHS IN THE 40S MUCH OF THE CWA. ONE NEGATIVE THEN IS POTENTIAL FOR THICKENING AFTERNOON CLOUD COVER IN BROAD WARM ADVECTION ZONE AHEAD OF ANOTHER NORTHERN PLAINS SHORTWAVE. .LONG TERM...(MONDAY NIGHT THROUGH FRIDAY) ISSUED AT 324 PM CST FRI FEB 12 2016 THE ONLY REAL CHANCE FOR PRECIPITATION IN THE LONGER TERM PERIOD APPEARS TO BE MONDAY NIGHT...WITH A WARMING TREND TO FOLLOW...ESPECIALLY BY THE END OF THE WEEK. BROAD WARM ADVECTION WILL BE ONGOING AT THE START OF THE LONG TERM PERIOD AS ONE MORE SHORTWAVE DIVES THROUGH THE NORTHERN PLAINS MONDAY NIGHT AND SWINGS THROUGH TENNESSEE TUESDAY. TRACK OF ASSOCIATED SURFACE LOW IS SHOWN WITH A MORE SOUTHWESTERLY PATH ON THE ECMWF AS OPPOSED TO THE GFS...RIDING THROUGH EASTERN SOUTH DAKOTA AND WESTERN IOWA AS OPPOSED TO SOUTHERN MINNESOTA AND EASTERN IOWA. THUS THE ECMWF HAS A MUCH GREATER CHANCE FOR ACCUMULATING SNOW ALONG THE MISSOURI RIVER AND EAST. BUT EVEN WITH THIS MORE AGGRESSIVE TRACK...MOST OF EASTERN NEBRASKA AND WESTERN IOWA WILL BE ON THE DRIER SIDE OF THIS FAST-MOVING SYSTEM...SUGGESTING SNOW AMOUNTS WILL REMAIN LIGHT. WILL MAINTAIN AT LEAST A SLIGHT CHANCE FOR SNOW THEN. BY TUESDAY...THIS SHORTWAVE WILL BE MOVING WELL OFF TO THE SOUTHEAST LEAVING RISING MID LEVEL HEIGHTS AND WARMER TEMPERATURES IN ITS WAKE. NORTHWEST MID LEVEL FLOW WILL DOMINATE OUR AREA INTO WEDNESDAY BEFORE RIDGING BUILDS OVERHEAD ON THURSDAY. 850 TEMPERATURES RISE FROM 2C TO 4C BELOW TUESDAY AT 18Z TO THE 10C TO 14C RANGE BY THURSDAY 18Z ON BOTH THE ECMWF AND GFS. HAVE HIGHS AVERAGING IN THE 40S OR SO TUESDAY AND WEDNESDAY...AND A WHOLE LOT OF 50S BY THURSDAY. 50S AGAIN FOR FRIDAY IS THE CURRENT THINKING...BUT A RELATIVELY PROGRESSIVE SHORTWAVE IS NOTED MOVING INTO THE PLAINS THEN. TIMING/TRACK DIFFERENCES ABOUND...SO WILL MAINTAIN AN OPTIMISTIC FORECAST FOR NOW...BUT COULD EASILY SEE TEMPERATURES MUCH COOLER THAN GOING FORECAST FOR FRIDAY. && .AVIATION...(00Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 520 PM CST FRI FEB 12 2016 VFR CONDITIONS INITIALLY. SOME LIGHT SNOW COULD DEVELOP AT KOFK 10-16Z...AND KOMA 17-22Z. COULD BE TEMPORARY MVFR CONDITIONS WITH THE SNOW...THEN MVFR BEYOND THEN. SNOW MAY STAY NORTH OF KLNK. NORTHEASTERLY WINDS LESS THAN 12 KNOTS...THEN BECOMING SOUTHEAST THROUGH THE PERIOD AND INCREASING TO ABOVE 12 KNOTS. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...DEWALD

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