Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 010453
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1153 PM CDT THU APR 30 2015

.SHORT TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 319 PM CDT THU APR 30 2015

RAIN CHANCES BEGINNING LATER TONIGHT INTO FRIDAY...AND WHEN BEST
CHANCES ARE OVER THE WEEKEND...REMAIN THE PRIMARY FORECAST CONCERNS.

MID LEVEL SHORTWAVE EXTENDING FROM EASTERN SASKATCHEWAN INTO MONTANA
WILL CONTINUE ITS TREK EASTWARD THIS AFTERNOON AND WEAKEN LATER
TONIGHT AS IT MOVES TOWARD THE GREAT LAKES. ATTENDANT COLD FRONT NOW
IN THE HIGH PLAINS OF THE DAKOTAS WILL BE PUSHED SOUTHEAST INTO
NORTHEAST NEBRASKA AFTER MIDNIGHT...BUT WILL ONLY LIMP FARTHER
SOUTHEAST AS UPPER SUPPORT WEAKENS. CURRENT AND FORECAST MOISTURE
PROFILES ARE RELATIVELY DRY...ALONG WITH LIMITED UPPER SUPPORT. SO
WHILE AM EXPECTING SHOWERS AND ISOLATED THUNDER TO OCCUR ALONG
FRONTAL BOUNDARY...COVERAGE SHOULD BE WIDELY SCATTERED IN NATURE.
WILL INTRODUCE PRECIP ALONG FRONT BEGINNING IN NORTHEAST NEBRASKA
AFTER 06Z...THEN APPROACHING INTERSTATE 80 BY MID FRIDAY MORNING.
GIVEN LESSENING AFFECTS OF FORCING ALOFT AND ALONG FRONTAL
ZONE...HAVE GRADUALLY DECREASING CHANCES FOR PRECIPITATION FRIDAY
AFTERNOON AND EVENING.

FOR SATURDAY...ISOLATED SHOWERS COULD LINGER IN SOUTHWEST IOWA OR
SOUTHEAST NEBRASKA IN THE MORNING...BUT MOST OF THE REST OF THE DAY
SHOULD BE DRY. MODEL OUTPUT IS BASICALLY DRY SATURDAY
AFTERNOON...AND CAN NOT REALLY PIN DOWN RESIDUAL FRONTAL
BOUNDARY...AND UPPER SUPPORT IS NON EXISTENT. HOWEVER GFS IS
PAINTING AN AREA OF 1000-1500 J/KG OF SURFACE-BASED CAPE SATURDAY
AFTERNOON IN EASTERN NEBRASKA WITH LIMITED CINH. SO CAN NOT RULE
OUT AN ISOLATED STORM FIRING AT SOME POINT...BUT AREAL COVERAGE
LOOKS MINIMAL.

THEN ATTENTION TURNS TO WARMER TEMPERATURES SUNDAY AHEAD OF ANOTHER
APPROACHING COLD FRONT. MID LEVEL WAVE TRACKING ACROSS SOUTHERN
CANADA AND THE NORTHERN PLAINS WILL AGAIN PUSH A COLD FRONT INTO
NORTHEAST NEBRASKA LATER SUNDAY AFTERNOON. WARM MID LEVEL
TEMPERATURES SHOULD CAP MOST CONVECTION AT THAT TIME...AND WILL ALSO
ALLOW TEMPERATURES AHEAD OF THE FRONT TO WARM WELL INTO THE 80S.
THERMAL TROUGH AT 850MB POINTS DIRECTLY INTO NORTHEAST NEBRASKA
WHERE HIGHS IN THE MID 80S OR HIGHER SHOULD OCCUR...WITH AT LEAST
LOWER 80S ACROSS THE REST OF EASTERN NEBRASKA AND SOUTHWEST IOWA.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 319 PM CDT THU APR 30 2015

BETTER SHOWER/THUNDER CHANCES ARE IN THE OFFING FOR MUCH OF THE WEEK
AS SUNDAY COLD FRONT SLIPS INTO THE CWA AND REMAINS CLOSE TO OUR
AREA UNTIL LATER IN THE WEEK AS AN UPPER LOW/TROUGH APPROACHES.
INSTABILITY SHOULD BE AT LEAST MODERATELY HIGH SUNDAY EVENING GIVEN
WARM AFTERNOON TEMPERATURES AND INCREASING LOW LEVEL MOISTURE. AS
ATMOSPHERE COOLS IN THE EVENING...EXPECT SCATTERED STORMS ALONG COLD
FRONT AS IT MOVES TOWARD INTERSTATE 80 AND BEYOND. SOME HAIL
POTENTIAL GIVEN DEGREE OF INSTABILITY...BUT SHEAR IS RATHER WEAK AT
THIS TIME.

THERE IS SOME MODEL CONSISTENCY IN STALLING FRONT IN SOUTHEAST
NEBRASKA ON MONDAY...THE SHOVING IT BACK NORTH INTO NORTHEAST
NEBRASKA ON TUESDAY. THE POTENTIAL WILL EXIST FOR STORMS ALONG THIS
BOUNDARY BOTH DAYS...AND THE EXACT LOCATION WILL BE TOUGH TO NAIL
DOWN RIGHT NOW. HOWEVER IT SEEMS LOGICAL THAT AFTERNOON HEATING WILL
PLAY A ROLE IN TIMING OF HIGHEST PRECIP CHANCES...FAVORING THE
AFTERNOON AND EVENING BOTH MONDAY AND TUESDAY. BY WEDNESDAY...UPPER
TROUGH WILL BE ROTATING INTO THE PLAINS...BRINGING COOLER MID LEVEL
TEMPERATURES OVER GRADUALLY MOISTENING LOW LEVELS. THUS
INSTABILITY AND POTENTIAL FOR SEVERE ARE FORECAST TO INCREASE
BOTH WEDNESDAY AND THURSDAY...WITH GFS SUGGESTING 3000 J/KG OF
SURFACE-BASED CAPE THURSDAY AFTERNOON.

&&

.AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1144 PM CDT THU APR 30 2015

FORECAST REASONING REMAINS FROM PREVIOUS TAF CYCLE. VFR CONDITIONS
ARE EXPECTED TO CONTINUE. ISOLATED TO SCATTERED SHOWERS AND A
POSSIBLE RUMBLE OF THUNDER SHOULD MOVE INTO THE AREA FROM LATE
OVERNIGHT/EARLY MORNING THROUGH THE AFTERNOON...BUT COVERAGE
CONCERNS PRECLUDES MENTION AT THIS TIME. SOUTHEAST WINDS WILL
BECOME SOUTHWESTERLY...WITH SPEEDS AT OR BELOW 10KT.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$

SHORT TERM...DERGAN
LONG TERM...DERGAN
AVIATION...MAYES


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