Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 211111 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 611 AM CDT THU MAY 21 2015 .SHORT TERM...(TODAY THROUGH SATURDAY) ISSUED AT 330 AM CDT THU MAY 21 2015 THE CHANCE FOR STORMS FRIDAY INTO SATURDAY REMAINS THE PRIMARY FORECAST CHALLENGE FOR THE SHORT TERM PERIOD. MID LEVEL SHORTWAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO SOUTH DAKOTA WAS DROPPING SOUTHEAST THIS MORNING...AND WILL EXIT OUR AREA EARLY IN THE DAY. IN ITS WAKE...SHORTWAVE RIDGING IS FORECAST TO MOVE OVER MID AMERICA LATER TODAY AND TONIGHT...AHEAD OF A MORE SIGNIFICANT SHORTWAVE EJECTING INTO THE PLAINS FRIDAY INTO FRIDAY NIGHT. AT THE SURFACE...HIGH PRESSURE WAS RIDGING IN FROM THE HIGH PLAINS OF SOUTH DAKOTA INTO EASTERN NEBRASKA...AND WILL DRIFT SOUTHEAST WITH TIME TODAY. THE HIGH WAS HELPING TO CLEAR SKIES OVER EASTERN NEBRASKA AND SOUTHWEST IOWA...AND WITH SOUTHEAST MOVEMENT...EXPECT ESSENTIALLY SUNNY SKIES TO PREVAIL TODAY WITH NORTHWEST WINDS. HIGHS SHOULD CLIMB WELL INTO THE 60S IF NOT LOW 70S ACROSS OUR AREA. MID LEVEL CLOUD COVER IS EXPECTED TO COMMENCE LATER TONIGHT AHEAD OF EJECTING SHORTWAVE. FORECAST SOUNDINGS SHOW A DRY ATMOSPHERE WILL GRADUALLY MOISTEN TOP-DOWN FROM SOUTHWEST TO NORTHEAST ACROSS THE CWA ON FRIDAY. HOWEVER FORCING FOR PRECIPITATION WILL FOLLOW SHORTWAVE THROUGH WESTERN NEBRASKA NORTH INTO SOUTH DAKOTA...AND WITH A MID LEVEL JET SEGMENT PUNCHING THROUGH KANSAS. INSTABILITY IS NON-EXISTENT AS WELL. SO ASIDE FROM OUR WESTERN AND SOUTHERN CWA WHERE PROXIMITY TO UPPER SUPPORT PLAYS A ROLE...HAVING A HARD TIME SEEING WHY ANY SIGNIFICANT PRECIPITATION WILL FALL BOTH FRIDAY AND FRIDAY NIGHT. THUS HAVE TRIMMED RAIN CHANCES A BIT AND SLOWED EASTWARD ADVANCE A TAD. INSTABILITY WILL BEGIN A SLOW INCREASE DURING THE DAY SATURDAY WHEN SOUNDINGS SHOW PLENTY OF AVAILABLE MOISTURE...PRECIPITABLE WATER NEAR 1.25 WHICH IS APPROACHING 150 PERCENT OF NORMAL. WHILE THERE APPEARS TO BE NO SUBSTANTIAL LOW LEVEL CONVERGENCE OR SIGNIFICANT MID LEVEL FEATURES MOVING THROUGH...WILL LIKELY SEE ISOLATED SHOWERS OR STORMS BUBBLE UP SATURDAY AFTERNOON IN THIS MOIST REGIME. SO WILL MAINTAIN SMALL PRECIP CHANCE THROUGH THE AFTERNOON. .LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY) ISSUED AT 330 AM CDT THU MAY 21 2015 THUNDERSTORM CHANCES CONTINUE TO BE THE FOCUS FOR THE LONGER TERM FORECAST AS WELL. LINGERING ISOLATED SHOWERS OR STORMS FROM SATURDAY AFTERNOON WILL LIKELY BEGIN TO DISSIPATE SATURDAY EVENING. HOWEVER PRECIP CHANCES SHOULD INCREASE AGAIN AFTER MIDNIGHT WITH GFS/ECMWF SUGGESTING SHORTWAVE WILL EJECT THROUGH THE REGION. COULD SEE SOME SIGNIFICANT RAINS AT THIS TIME GIVEN HIGH PRECIPITABLE WATER AND POTENTIAL FOR TRAINING AS 850 FLOW PARALLELS MID LEVEL JET AND MID LEVEL DIFFLUENCE SETS UP JUST TO OUR NORTHEAST. THIS ROUND OF PRECIPITATION SHOULD LINGER TROUGH SUNDAY MORNING BEFORE SHORTWAVE LIFTS NORTHEAST. HOWEVER NO SIGNIFICANT ATMOSPHERIC DRYING WILL BE REALIZED AS SOUTHERLY FLOW CONTINUES AHEAD OF MAIN UPPER TROUGH ADVANCING TOWARD THE PLAINS. THAT TROUGH WILL SLOWLY DAMPEN AS IT LIFTS NORTHEAST AND SPITS OUT PIECES OF ENERGY ACROSS THE PLAINS THROUGH TUESDAY. THEREFORE WE CAN NOT RULE OUT SCATTERED SHOWERS AND THUNDERSTORMS FROM TIME TO TIME RIGHT INTO THE MIDDLE OF THE WEEK. && .AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 610 AM CDT THU MAY 21 2015 THERE HAS BEEN SOME PATCHY FOG AROUND EARLY THIS MORNING...BUT IT HAS NOT AFFECTED THE TAF SITES MUCH SO FAR. LOOK FOR GENERALLY VFR CONDITIONS THROUGH THE PERIOD. RAIN CHANCES WERE LOW ENOUGH TO LEAVE OUT OF THIS SET OF TAFS BUT CHANCES WILL INCREASE LATER FRIDAY. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...MILLER

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