Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 201724 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1224 PM CDT WED MAY 20 2015 .UPDATE...
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ISSUED AT 1216 PM CDT WED MAY 20 2015 UPDATED THE FORECAST FOR SOME SPOTTY LINGERING LIGHT RAIN AND DRIZZLE WITH SOME WEAK WARM ADVECTION AND THE UPPER SHORTWAVE TROF IN THE AREA. LOWERED HIGH TEMPERATURES SLIGHTLY WHERE THE CLOUDS WILL HANG ON.
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&& .SHORT TERM...(TODAY THROUGH FRIDAY) ISSUED AT 327 AM CDT WED MAY 20 2015 ENDING RAIN TODAY...THEN WHEN TO INTRODUCE THUNDER CHANCES LATER THIS WEEK...ARE THE PRIMARY FORECAST CONCERNS. MID LEVEL WAVE WAS EJECTING THROUGH MID AMERICA THIS MORNING... BRINGING SHOWERS TO ALL OF EASTERN NEBRASKA AND SOUTHWEST IOWA. VORTICITY MAXIMUM WAS NOTED ALONG THE SOUTH DAKOTA BORDER IN NORTHWEST NEBRASKA...WITH LOBE OF VORTICITY STRETCHING EAST THEN SOUTHEAST INTO EASTERN NEBRASKA. THIS REPRESENTED THE BACK EDGE OF RAIN...WHICH WAS ENTERING OUR WESTERN CWA AS OF 3 AM. THIS TREND WILL CONTINUE THROUGH THE MORNING AS LOBE ROTATES NORTHEAST...BUT WILL STILL SEE ISOLATED TO SCATTERED SHOWERS INTO THE AFTERNOON AS VORT MAX SLIDES NEARLY DUE EAST. RAIN SHOULD BE ENDING BY THIS EVENING IN SOUTHWEST IOWA. THOUGH RAIN WILL END...PERSISTENT CLOUD COVER AND NORTHERLY LOW LEVEL WIND COMPONENT WILL KEEP TEMPERATURES CONFINED TO THE LOW TO MID 50S THIS AFTERNOON. CLOUDS WILL BE SLOW TO CLEAR FROM NORTH TO SOUTH OVERNIGHT. SOME CLEARING IN CENTRAL AND NORTHEAST NEBRASKA WHERE COOLEST TEMPS AND LIGHT WINDS WILL PREVAIL...COULD LEAD TO PATCHY FROST IN THOSE NORMAL COLD AIR DRAINAGE SITES. THEN NORTHWEST WINDS THURSDAY SHOULD SCOUR OUT REMAINING COVER. A SUBTLE INCREASE IN LOW LEVEL WARMTH COMBINED WITH SUNSHINE AND WESTERLY WIND COMPONENT SUGGEST 10 TO 15 DEGREES WARMER HIGHS THURSDAY AFTERNOON. WE THEN LOOK WEST AS UPPER LOW/TROUGH SETTLING INTO THE SOUTHWEST BEGINS TO EJECT ENERGY INTO THE PLAINS. THE FIRST WAVE SHOULD MOVE THROUGH THE CENTRAL ROCKIES THURSDAY NIGHT...BUT THEN LIFT MORE NORTHERLY THROUGH THE HIGH PLAINS ON FRIDAY. THE SOUTHERN EXTENT OF DAMPENING SHORTWAVE ENERGY MAY SKIRT OUR WESTERN CWA FRIDAY AFTERNOON...BUT LAYER MOISTURE AND LOW LEVEL CONVERGENCE ARE RELATIVELY SCANT. WILL KEEP SHOWER AND ISOLATED THUNDER CHANCES CONFINED TO THE WESTERN CWA FRIDAY AFTERNOON. .LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY) ISSUED AT 327 AM CDT WED MAY 20 2015 CONTINUED RAIN/THUNDER CHANCES THROUGH THE HOLIDAY WEEKEND ARE THE MAIN CHALLENGES FOR THE LONGER TERM FORECAST. WESTERN UPPER TROUGH WILL GRADUALLY DRIFT INTO THE ROCKIES...THEN BROADEN AND FLATTEN WITH TIME INTO TUESDAY. SEVERAL IMPULSES ROLLING THROUGH THE GENERAL SOUTHWEST FLOW ALOFT COULD BE THE SPARK FOR CONVECTION AT JUST ABOUT ANY TIME. MOISTURE PROFILES BECOME MORE FAVORABLE BY SUNDAY WHEN SURFACE DEW POINTS ARE EXPECTED TO REACH THE 60S. THE BEST COMBINATION OF MOISTURE AND INSTABILITY APPEAR TO RESIDE JUST AHEAD OF A COOL FRONT SETTLING INTO OUR AREA SUNDAY AFTERNOON. HOWEVER THAT INSTABILITY IS MODEST AT BEST AND SHEAR IS NOT SUBSTANTIAL. SO WHILE CHANCES FOR SHOWERS/STORMS WILL BE HIGH...SEVERE STORMS ARE NOT LOOKING LIKELY. WE SHOULD SEE A RELATIVE MINIMUM IN PRECIP CHANCES ON MONDAY BEHIND COOL FRONT. THEN GFS/ECMWF SUGGEST THAT FRONT WILL RETURN NORTH AS A WARM FRONT ON TUESDAY...WITH ATTENDANT MOISTURE/INSTABILITY BRINGING INCREASING RAIN CHANCES AGAIN. && .AVIATION...
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(18Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1216 PM CDT WED MAY 20 2015 MVFR/PATCHY IFR CIGS WILL GRADUALLY IMPROVE THIS AFTERNOON AND THIS EVENING AS DRIER AIR WORKS IN FROM THE NORTHWEST. SOME PATCHY LIGHT RAIN AND DRIZZLE INCLUDE EARLY ON AS WELL WITH THE SHORTWAVE SWINGING THROUGH. VFR CONDITIONS EXPECTED ONCE THESE LOWER CLOUDS GET SCOURED OUT. MAY SEE SOME PATCHY FOG THURSDAY MORNING WITH THE LIGHT WINDS AND WET GROUND/DECREASING CLOUDS.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ UPDATE...ZAPOTOCNY SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...ZAPOTOCNY

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