Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 051114
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
614 AM CDT SAT SEP 5 2015

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 352 AM CDT SAT SEP 5 2015

CHANCES FOR THUNDERSTORMS THROUGH MONDAY...WITH A SEVERE POTENTIAL
SUNDAY...ARE THE MAIN FORECAST PROBLEMS.

SOUTHWEST FLOW ALOFT CONTINUED THIS MORNING FROM THE BASE OF AN
UPPER TROUGH ALONG THE WEST COAST INTO THE NORTHERN PLAINS. MID
LEVEL RIDGING WAS NOTED FROM THE SOUTHERN PLAINS INTO EASTERN
KANSAS. WARM MID LEVEL TEMPERATURES UNDER RIDGE AXIS WAS
SQUASHING ATTEMPTS AT CONVECTION IN EASTERN NEBRASKA AND
SOUTHWEST IOWA...BUT PERSISTENT 45KT LOW LEVEL JET FINALLY LEAD TO
A FEW STORMS IN WEST CENTRAL IOWA. WE MAY SEE A FEW MORE OF THESE
EARLY THIS MORNING...BUT MOST SHOULD BE OUT OF OUR AREA SHORTLY
AFTER SUNRISE.

OTHERWISE MAIN STORM TRACK WILL REMAIN MOSTLY TO OUR WEST AND
NORTHWEST MUCH OF TODAY BEFORE UPPER LOW IN THE PACIFIC NORTHWEST
BEGINS TO EJECT INTO THE NORTHERN ROCKIES. MID LEVEL THETA-E AXIS
WILL NUDGE EAST AS THIS OCCURS...PUTTING PARTS OF NORTHEAST NEBRASKA
IN AREA OF SMALL PRECIPITATION POTENTIAL BEFORE SUNSET. THAT
POTENTIAL GRADUALLY INCREASES TONIGHT AND SHIFTS EAST AS UPPER LOW
CONTINUES LIFTING INTO SOUTHERN CANADA AND HEIGHTS ARE SUPPRESSED
SOUTHEAST IN THE PLAINS. ATTENDANT INCREASE IN WIND FIELDS COMBINED
WITH SOUTHEAST SHIFT IN THETA-E AXIS WILL RESULT IN SCATTERED
ELEVATED CONVECTION FIRING IN NORTHEAST NEBRASKA DURING THE EVENING
AND SPREADING TOWARD INTERSTATE 80 BY LATE TONIGHT.

WILL LIKELY SEE A DECREASE IN ACTIVITY SUNDAY MORNING AS LOW
LEVEL JET SUBSIDES FOR A TIME. THEN BY LATER SUNDAY MORNING...COLD
FRONT BEING DRIVEN EAST AND SOUTHEAST BY NORTHERN PLAINS TROUGH
WILL ENTER NORTHEAST NEBRASKA. QUALITY OF ATMOSPHERE AHEAD OF THIS
FRONT IS STILL IN QUESTION GIVEN POTENTIAL FOR MORNING
CLOUDS/CONVECTION. HOWEVER MODEL FORECASTS ARE HONING IN ON A
RIBBON OF SIGNIFICANT INSTABILITY ON THE ORDER OF 2000 J/KG OR
GREATER JUST AHEAD OF WIND SHIFT SUNDAY AFTERNOON. 0-6KM BULK
SHEAR OF 35KT IS FORECAST AS WELL...STARTING OUT NEARLY
PERPENDICULAR TO LINE OF CONVECTION SUGGESTING SUPERCELL STORMS
ARE POSSIBLE DURING EARLY STORM DEVELOPMENT PHASE. SHEAR VECTORS
BECOME MORE PARALLEL TO FRONT/CONVECTION WITH TIME DURING THE
EVENING...LEADING TO MORE LINEAR STORM STRUCTURES AND A POTENTIAL
FOR TRAINING OF STORMS AS FRONT BEGINS TO STALL OUT IN SOUTHEAST
NEBRASKA AND SOUTHWEST IOWA. SIGNIFICANT QPF IS NOTED FROM GFS IN
00Z-06Z MONDAY TIMEFRAME WHEN 2 TO 4 INCHES OF RAIN IS PAINTED
ACROSS SOUTHWEST IOWA.

FRONT IS EXPECTED TO ONLY SLOWLY DRIFT SOUTH LATER SUNDAY NIGHT INTO
MONDAY MORNING...BASICALLY STALLING OUT NEAR THE KANSAS BORDER.
SHOULD SEE GENERAL DECREASE IN STORMS TOWARD MONDAY MORNING WITH
UPPER SUPPORT WANING AND LOW LEVEL JET DECREASING. HOWEVER WILL SEE
AN INCREASE IN ACTIVITY THROUGH THE DAY WHEN MID LEVEL SHORTWAVE/JET
ROTATE THROUGH BROAD TROUGH IN THE PLAINS...LEADING TO STRONG
ISENTROPIC UPGLIDE OVER FRONT MONDAY AFTERNOON. IN FACT...GFS
SHOWS MORE INSTABILITY MONDAY AFTERNOON THAN SUNDAY DESPITE
NORTHERLY SURFACE WINDS. WE COULD AGAIN SEE SIGNIFICANT RAINFALL
IN PARTS OF EASTERN NEBRASKA AND SOUTHWEST IOWA WITH TRAINING OF
STORMS.

TEMPERATURES SHOULD CLIMB INTO THE 90S OVER MOST OF THE CWA TODAY
BEFORE COOLING BEGINS SUNDAY BEHIND COLD FRONT. WILL LIKELY SEE SOME
90S AHEAD OF THE FRONT SUNDAY AFTERNOON IN SOUTHEAST NEBRASKA AND
SOUTHWEST IOWA...BUT ONLY MID 80S IN OUR NORTH. LOW TO MID 80S ARE
FORECAST MONDAY BEHIND THE FRONT AND UNDER CLOUDS/PRECIP.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 352 AM CDT SAT SEP 5 2015

MUCH COOLER WEATHER IS FORECAST THROUGH THE BALANCE OF THE WEEK AS A
BROAD TROUGH REMAINS OVER THE MIDDLE OF THE COUNTRY. A COUPLE OF
SHORTWAVES MOVING THROUGH THE MAIN FLOW WILL BRING A CHANCE FOR
SHOWERS AND THUNDERSTORMS TUESDAY AND THEN AGAIN THURSDAY.
RELATIVELY STABLE BOUNDARY LEVEL AIR SUGGESTS SEVERE POTENTIAL IS
LOW DURING THIS TIME. AND A STRONG COLD FRONT ACCOMPANYING THURSDAY
WAVE WILL LEAD TO EVEN COOLER TEMPERATURES ON FRIDAY. LOOK FOR HIGHS
CLOSE TO 80 TUESDAY AND WEDNESDAY BEFORE COOLING INTO THE 70S
THURSDAY...AND PERHAPS 60S FOR FRIDAY.

&&

.AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 614 AM CDT SAT SEP 5 2015

MAINLY VFR CONDITIONS ARE EXPECTED THROUGHOUT THE PERIOD.  LLWS WILL
BE POSSIBLE THIS MORNING BEFORE DIMINISHING AS SURFACE WINDS
INCREASE TODAY.  A FEW SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE
ACROSS THE REGION TONIGHT...HOWEVER WILL NOT MENTION IN THE TAFS AT
THIS TIME DUE TO LOW CONFIDENCE IN TIMING AND LOCATION OF STORM
DEVELOPMENT.

&&

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

$$

SHORT TERM...DERGAN
LONG TERM...DERGAN
AVIATION...KG



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