Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 271713
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1213 PM CDT SAT JUN 27 2015

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 254 AM CDT SAT JUN 27 2015

SMALL RAIN CHANCE LATER TONIGHT INTO SUNDAY MORNING IS THE PRIMARY
FORECAST CONCERN. OTHERWISE A DRY FORECAST IS EXPECTED.

UPPER FLOW PATTERN WILL CHANGE VERY LITTLE THE NEXT SEVERAL DAYS AS
LONGWAVE RIDGE IN THE WESTERN STATES AND MEAN TROUGH FROM THE GREAT
LAKES TO THE GULF COAST BOTH REMAIN LOCKED IN POSITION AT LEAST
THROUGH MONDAY. THIS LEAVES EASTERN NEBRASKA AND WESTERN IOWA UNDER
NORTH-NORTHWEST MID LEVEL FLOW REGIME. WHILE RIPPLES IN THAT FLOW
COULD BRING A STRAY SHOWER TO OUR AREA...THE TENDENCY TOWARD A
MAINLY DRY FORECAST IS STRONG. LATER TONIGHT INTO SUNDAY MAY BE THE
EXCEPTION AS A STRONGER SHORTWAVE IS SCHEDULED TO PLUNGE INTO THE
PLAINS THEN.

CURRENT SURFACE SITUATION SHOWS RIDGE IN PLACE FROM NORTHERN
WISCONSIN INTO NORTHWEST KANSAS. NORTHERLY LOW LEVEL FLOW FROM
FRIDAY SHUNTED FRONTAL BOUNDARY AND MOISTURE WELL TO OUR SOUTH INTO
OKLAHOMA AND ARKANSAS...AND MOISTURE WILL BE SLOW TO RETURN GIVEN
UPPER FLOW PATTERN. WEAK INSTABILITY IS FORECAST ACROSS OUR AREA
EACH OF THE NEXT SEVERAL AFTERNOONS AS TEMPERATURES RISE WELL INTO
THE 80S EACH DAY...PROVIDING SCATTERED AFTERNOON CUMULUS BUT NOT
MUCH ELSE SAVE FOR PASSING MID LEVEL CLOUDS ASSOCIATED WITH WEAK
SHORTWAVES.

THE BEST CHANCE FOR PRECIPITATION THROUGH MONDAY WILL COME TONIGHT
INTO SUNDAY MORNING AS STRONG SHORTWAVE CURRENTLY TAKING SHAPE IN
NORTHERN MANITOBA AND SASKATCHEWAN DIVES INTO NORTHERN MINNESOTA
LATER TONIGHT...THEN TRACKS ALONG THE MISSISSIPPI RIVER INTO SUNDAY
NIGHT. POTENT MID LEVEL WARM ADVECTION WILL BE MAXIMIZED WELL TO OUR
EAST...CLOSER TO SHORTWAVE TRACK. HOWEVER SHEARED VORTICITY
EXTENDING TO THE WEST MAY CLIP OUR FAR EASTERN CWA WITH A FEW
SHOWERS OR STORMS LATE TONIGHT AND SUNDAY. WILL MAINTAIN SMALL
PRECIPITATION CHANCES FOR PARTS OF WESTERN IOWA TO ACCOUNT FOR THIS
AS MODELS HAVE BEEN RELATIVELY PERSISTENT IN SHOWING QPF THERE.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 254 AM CDT SAT JUN 27 2015

NORTHWEST FLOW ALOFT WILL BRING OCCASIONAL THUNDERSTORM CHANCES TO
THE AREA NEXT WEEK...BUT NAILING DOWN BEST RAIN CHANCES IS THE MAIN
LONGER TERM FORECAST CONCERN.

MAIN MID LEVEL FLOW PATTERN WILL TREND TOWARD A LITTLE LESS
AMPLIFICATION WITH EASTERN TROUGH AND WESTERN RIDGE NEXT
WEEK...LEAVING NEBRASKA AND IOWA UNDER NORTHWEST FLOW. AS IS THE
CASE THIS WEEKEND...SEVERAL POTENTIAL IMPULSES ROLLING THROUGH THE
FLOW COULD BRING STRAY SHOWERS FROM TIME TO TIME. HOWEVER THERE IS
SOME AGREEMENT BETWEEN MODEL FORECASTS...ESPECIALLY GFS AND
ECMWF...IN SHOWING MORE SIGNIFICANT SHORTWAVES AFFECTING OUR AREA IN
THE TUESDAY NIGHT/WEDNESDAY AND THURSDAY NIGHT/FRIDAY TIMEFRAMES.

MOISTURE RETURN WILL BEGIN TUESDAY AS MID LEVEL WAVE APPROACHES AND
INDUCES SOUTHERLY FLOW IN THE PLAINS. STRONG BAROCLINIC ZONE WILL
RESULT...TAKING A NORTHWEST TO SOUTHEAST ORIENTATION WITH TIME BY
TUESDAY NIGHT. EXPECT ECMWF IS PROBABLY MORE ACCURATE IN SHOWING
TIGHTEST GRADIENT TO OUR SOUTHWEST...SUGGESTING ISENTROPIC UPGLIDE
WILL RESULT IN BEST LIFT/SATURATION OVER EASTERN NEBRASKA AND
SOUTHWEST IOWA AS LOW LEVEL JET INTENSIFIES. GIVEN RELATIVE MODEL
AGREEMENT AND PERSISTENCE...WILL BEGIN TO INCREASE THUNDER CHANCES
FOR TUESDAY NIGHT INTO WEDNESDAY.

WOULD THINK WEDNESDAY NIGHT AND THURSDAY WILL BE MAINLY DRY IN WAKE
OF SHORTWAVE...BUT WILL MAINTAIN SMALL POPS IN CASE TIMING IS OFF A
BIT. THEN AN INCREASE IN PRECIP CHANCES IS AGAIN IN ORDER AS NEXT
WAVE APPROACHES THURSDAY NIGHT AND FRIDAY.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1159 AM CDT SAT JUN 27 2015

VFR CONDITIONS WILL PREVAIL THRU THE FCST PD.

&&

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

$$

SHORT TERM...DERGAN
LONG TERM...DERGAN
AVIATION...DEE


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