Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 211711
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1211 PM CDT SUN SEP 21 2014

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 311 AM CDT SUN SEP 21 2014

...RAIN CHANCES MON NT AND TUE CONTINUE TO BE THE PRIMARY FORECAST
CONCERNS...

A UNIQUE UPPER FLOW PATTERN WILL DETERMINE THE WEATHER...AND
SPECIFICALLY THE RAIN CHANCES...THROUGH THE NEXT SEVERAL DAYS OVER
THE FORECAST AREA. WATER VAPOR LOOP AND UPPER AIR DATA INDICATES THIS
PATTERN CONSISTS OF AN UPPER RIDGE THAT CURRENTLY EXTENDS FROM
THE SOUTHERN ROCKIES INTO BRITISH COLUMBIA...AND A SLOW-MOVING
CUTOFF UPPER LOW THAT HAS BEEN LINGERING ON THE WEST SIDE OF THE
UPPER RIDGE AXIS...CURRENTLY SITTING OVER CALIFORNIA. THE SURFACE
REFLECTION OF THE UPPER RIDGE WAS A 1026 MB SURFACE HIGH CENTERED
OVER EASTERN MONTANA...REPRESENTING A DRY AIRMASS THAT HAS WORKED
INTO THE FORECAST AREA.

THIS DRY AIRMASS AND SURFACE HIGH WILL KEEP QUIET AND DRY WEATHER
IN PLACE THROUGH MONDAY. HOWEVER BY MONDAY EVENING THE UPPER LOW
OVER CALIFORNIA IS EXPECTED TO DRIFT INTO THE UPPER RIDGE AND MAKE
ITS WAY INTO THE NORTHERN HIGH PLAINS OF WYOMING AND MONTANA.
THERE IS VERY GOOD MODEL AGREEMENT WITH THE POSITION OF THIS
LOW...AND THE RUN-RUN CONSISTENCY IS ALSO HIGH. MODEL TRENDS ARE
TOWARD SLIGHTLY HIGHER HEIGHTS WITH THE UPPER LOW...BUT GENERALLY
THE CONSISTENCY IS QUITE GOOD.

WITH SIMILAR MODEL AGREEMENT...CYCLOGENESIS OVER THE NORTHERN
HIGH PLAINS IS PROGGED MONDAY NIGHT WITH THE SURFACE HIGH MOVING
EAST OF THE MISSISSIPPI RIVER AND STRONG SOUTH FLOW SETTING UP
OVER THE PLAINS. EXPECT ANY RAIN MONDAY NIGHT TO BE CONFINED TO
CENTRAL NEBRASKA...WITH PERHAPS A FEW LIGHT SHOWERS TRYING TO
OVERCOME THE DRY AIR AND MOVE AS FAR EAST AS COLUMBUS AND NORFOLK
LATE MONDAY NIGHT.

ON TUESDAY THE UPPER LOW MOVES INTO THE DAKOTAS WITH ASSOCIATED
UPPER TROUGH EXTENDING INTO THE SOUTHERN PLAINS...THE SURFACE LOW
DEEPENS TO OUR WEST...AND ENOUGH MOISTURE RETURNS TO SUPPORT
PRECIPITATION OVER ALL OF OUR FORECAST AREA. INSTABILITY SHOULD BE
LIMITED SO WE MAINLY EXPECT RAIN SHOWERS WITH A FEW EMBEDDED
THUNDERSTORMS. POPS RANGE FROM CHANCE IN THE EAST TO LIKELY IN OUR
WESTERN COUNTIES. TEMPERATURES WILL BE HELD DOWN A FEW DEGREES ON
TUESDAY FROM THE RAIN/CLOUDS...WITH UPPER 60S - LOW 70S COMMON.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 311 AM CDT SUN SEP 21 2014

THE PATTERN ON TUESDAY GENERALLY REMAINS IN PLACE INTO
WEDNESDAY...BUT MODEL SOLUTIONS QUICKLY DIVERGE AFTER WEDNESDAY
NIGHT. IN ADDITION...SUBSIDENCE FROM THE UPPER RIDGE SHOULD BE
OVERTAKING THE UPPER LOW WITH AN OVERALL WEAKENING OF THE VERTICAL
MOTION ASSOCIATED WITH IT. MODELS SHOW 500 MB HEIGHTS AT OR ABOVE
5880 METERS IN THE UPPER RIDGE...WITH WEAK UPPER FLOW AND WARMING
ALOFT. THIS SHOULD SUPPRESS CONVECTION MOST AREAS. THEREFORE KEPT
POPS TUESDAY NIGHT INTO WEDNESDAY NIGHT...BUT HAVE A DRY FORECAST
FOR THURSDAY THROUGH SATURDAY.

TEMPERATURES UNDER THE UPPER RIDGE SHOULD RETURN TO NEAR OR
SLIGHTLY ABOVE NORMAL VALUES IN THE UPPER 70S BY THE END OF THE
WEEK.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1210 PM CDT SUN SEP 21 2014

VFR CONDITIONS THROUGH THE PERIOD. NORTHWEST WINDS AROUND 13 KNOTS
WITH GUSTS UP TO AROUND 20 KNOTS THROUGH ABOUT 23-00Z...THEN LIGHT
AND VARIABLE WINDS BEYOND THEN.

&&

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

$$

SHORT TERM...NIETFELD
LONG TERM...NIETFELD
AVIATION...DEWALD


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