Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 031717
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1217 PM CDT SUN MAY 3 2015

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 320 AM CDT SUN MAY 3 2015

TODAY...STORMS SHOULD CONTINUE EASTWARD OUT OF THE FORECAST AREA
EARLY THIS MORNING. HIGH RES MODELS ARE IN GOOD AGREEMENT WITH
THAT. STORMS LAST EVENING DID PRODUCE SOME LARGE HAIL AND A FEW
SPOTS RECEIVED STRONG WINDS AS STORMS MIXED DOWN A STRONG LOW
LEVEL JET. AS OF AROUND 07Z RUC MODEL INITIALIZATION SHOWED WINDS
AT AROUND 1 KM AGL OF AROUND 40-50 KNOTS STRETCHING FROM WESTERN
OKLAHOMA INTO SOUTHEAST NEBRASKA AND PARTS OF IOWA. THESE WINDS
WILL DECREASE THIS MORNING. COLD FRONT AS OF 08Z STRETCHED FROM
NORTHEAST MINNESOTA BACK INTO WESTERN SOUTH DAKOTA. THAT FRONT
WILL MOVE SOUTHEAST INTO NORTHEAST NEBRASKA THIS AFTERNOON. LOOK
FOR HIGHS IN THE MID TO UPPER 80S AT MOST SPOTS TODAY WITH A FEW
HIGHS AROUND 90 POSSIBLE. THIS WILL CREATE CAPE VALUES FROM 1500
TO 2500 J/KG BY MID AFTERNOON. EXPECT CAP TO BREAK NEAR THE FRONT
BY MID/LATE AFTERNOON. SOME MODELS ALSO HINT AT THE CAP WEAKENING
FARTHER SOUTH...BUT WITH A LACK OF FOCUS AT THAT TIME WILL KEEP
HIGHEST POPS CLOSER TO THE FRONT. SOME SEVERE STORMS APPEAR
POSSIBLE...WITH LARGE HAIL AND DAMAGING WINDS THE MAIN THREATS.

GENERALLY USED A BLEND OF SHORT RANGE GUIDANCE FOR TONIGHT WITH THE
HIGHEST WEIGHT GIVEN TO THE 00Z HIGH RES WRF-ARW MODEL. LIKE SOME OF
THE OTHER MODELS...IT DEVELOPED STORMS LATE AFTERNOON THEN MOVED
THEM SOUTH AND EAST. SOME STORMS MAY CONTINUE TO BE SEVERE IN THE
EVENING. COVERAGE SHOULD DECREASE AFTER MIDNIGHT. CONVECTION WILL
LIKELY FORCE THE FRONT DOWN AT LEAST AS FAR AS SOUTHEAST NEBRASKA
AND MAYBE INTO NORTHEAST KANSAS BY 12Z MONDAY. MOST MODELS SHOW
LIFT OCCURRING OVER THE BOUNDARY DURING THE DAY MONDAY WITH PCPN
COVERAGE INCREASING...SO HAVE POPS INCREASING TO MATCH THAT. TWO
CLUSTERS OF STORMS MAY TAKE SHAPE BY LATE AFTERNOON OR EARLY
EVENING. ONE NEAR THE NEBRASKA/SOUTH DAKOTA BORDER AND ANOTHER
LIFTING FROM NORTHERN KANSAS THROUGH OUR AREA AND TOWARD CENTRAL
IOWA MONDAY NIGHT.

TUESDAY...WE MAY SEE SOMEWHAT OF A BREAK IN THE WIDESPREAD PCPN...
AT LEAST OVER SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. HAVE POPS
RANGING FROM 15 TO 50 PERCENT...HIGHEST IN NORTHEAST NEBRASKA.
SOUTHERLY FLOW WILL INCREASE AND HELP A WARM FRONT LIFT NORTH OF
THE AREA.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 320 AM CDT SUN MAY 3 2015

PATTERN WILL BE ACTIVE MUCH OF THIS PERIOD. A LARGE MID TROPOSPHERIC
TROUGH SHOULD BE OVER THE WESTERN UNITED STATES AT THE START OF THIS
PERIOD WITH EMBEDDED SHORTWAVES. ONE OF THESE WAVES WILL LIFT ACROSS
MID AMERICA WEDNESDAY/WEDNESDAY NIGHT...WHILE A CLOSED LOW STARTS TO
DIG SOUTHWARD FROM THE PACIFIC NORTHWEST. THIS WILL GENERALLY KEEP
OUR AREA IN SOUTHWEST FLOW WITH A DECENT SUPPLY OF LOW LEVEL MOISTURE
FOR SHOWERS AND STORMS TO WORK WITH. MODEL AGREEMENT STARTS TO FALL
OFF BY DAY 7...SO CONFIDENCE FALLS TO AVERAGE BY DAY 7. TEMPERATURES
AND PCPN SHOULD BE AT OR ABOVE NORMAL FOR THIS PERIOD.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1211 PM CDT SUN MAY 3 2015

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO INCREASE IN
AREAL COVERAGE THIS AFTN ALONG A COLD FRONT PUSHING THRU ERN NEB.
IT IS POSSIBLE THAT A FEW STORMS MAY APPROACH OR BECOME SEVERE
LATE THIS AFTN. HAVE ADDED TEMPO GROUPS AT ALL TERMINALS FOR
POSSIBLE LATE AFTN/EARLY EVENING MVFR CONDITIONS. VFR CONDITIONS
THEN PREVAILING THIS EVENING THRU THE REST OF THE FCST PD.

&&

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

$$

SHORT TERM...PEARSON/MILLER
LONG TERM...MILLER
AVIATION...DEE



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