Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 260431
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1131 PM CDT MON AUG 25 2014

.SHORT TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 245 PM CDT MON AUG 25 2014

TIMING THE BEST CHANCES FOR TSTMS AND POTENTIAL FOR HEAVY RAIN WILL
PROVIDE THE MAIN FORECAST CHALLENGES.

WE HAVE KEPT VERY GOOD CONTINUITY THE PAST FEW DAYS SO THE OVERALL
THINKING THIS AFTERNOON IS SIMILAR TO PREVIOUS FORECASTS. AS WE
GET CLOSER IN TIME...WE WILL TRY TO FINE TUNE THE DETAILS OF EACH
POTENTIAL HEAVY RAIN EVENT. CAN NOT RULE OUT SOME ISOLD SEVERE
STORMS THE NEXT FEW DAYS...BUT OVERALL THREAT SEEMS RELATIVELY LOW.

LARGE SCALE PATTERN AT 12Z FOR THE 300 MB LEVEL SHOWED A JET SEGMENT
WITH WINDS OF 90 KNOTS OR SO DIGGING SOUTH FROM WA INTO NRN CA AND
ANOTHER AREA OF WINDS AROUND 80 KNOTS CURVING CYCLONICALLY FROM SRN
MN INTO ONTARIO CANADA. MUCH OF THE AREA FROM THE EASTERN ROCKIES
INTO THE CENTRAL PLAINS SHOWED WEAK HEIGHT RISES AT 500 MB. A 50
METER HEIGHT FALL CENTER WAS NOTED OVER THE NRN CA/NWRN NV BORDER
REGION. A MOIST PLUME AT 700 MB (DEWPOINTS MAINLY 3 TO 7 DEGREES C)
STRETCHED FROM SONORA AND CHIHUAHUA MEXICO UP THROUGH AZ...CO...NE
AND THEN INTO THE WRN GREAT LAKES REGION. AT 850 MB...LOW PRESSURE
WAS OVER ERN CO. SURFACE ANALYSIS EARLY THIS AFTERNOON SHOWED A
FRONTAL BOUNDARY CURVING FROM WI ACROSS IA AND THEN SWWD DOWN INTO
SWRN KS. A SECONDARY PUSH OF COOL AIR HAD MOVED INTO OUR NRN ZONES
WITH BRISK NORTH WINDS EARLIER. 19Z SURFACE MAP SPECIFICS SHOWED
TEMPERATURES LOCALLY RANGING FROM 66 DEGREES AT KOFK AND KLCG TO
89 AT KFNB. MOST OF THE HIGH RESOLUTION MODELS SHOW CURRENT TSTM
ACTIVITY MOVING OUT OR WEAKENING BY LATE AFTERNOON.

TONIGHT...EXPECT AN INCREASE IN TSTM COVERAGE...WITH HEAVY RAIN
POSSIBLE. SUBSIDENCE IN THE 700-500 MB LAYER BEHIND DEPARTING
SHORTWAVE TROUGH SHOULD ALLOW FOR A MAINLY DRY PERIOD EARLY THIS
EVENING. THIS WILL CHANGE QUICKLY THOUGH WITH FAIRLY STRONG LIFT
DEVELOPING AS A SHORTWAVE TROUGH MOVES IN FROM THE WEST AND
CONVERGENCE INCREASES WITH DEVELOPMENT OF LOW LEVEL JET. WE
SHOULD ALSO SEE SOME ENHANCED LIFT OVERNIGHT DUE TO UPPER
TROPOSPHERIC DIVERGENCE SINCE WILL BE UNDER THE RIGHT ENTRANCE
REGION (RIGHT REAR QUADRANT) OF A 300 MB JETSTREAK THAT IS
EXPECTED TO BE OVER CNTRL/NRN MN BY 12Z TUESDAY.

CURRENT PRECIPITABLE WATER VALUES ARE MAINLY 1.40 INCHES OR LESS.
POINT FORECAST SOUNDINGS AND PLAN VIEWS OF MODEL PRECIPITABLE
WATER SHOW MAXIMUM VALUES BETWEEN 1.60 AND 2.00 INCHES OVERNIGHT.
CORFIDI VECTORS ARE MAINLY 15 KNOTS OR LESS SO THERE MAY BE SOME
TENDENCY FOR BACKBUILDING. ALTHOUGH WE CAN NOT SAY FOR SURE THAT
FLASH FLOODING WILL NOT DEVELOP TONIGHT...CHANCES SEEM HIGHER
TUESDAY NIGHT AND ALSO WEDNESDAY NIGHT. AREA THAT COULD SEE HEAVY
RAIN TUESDAY NIGHT IS ABOUT THE SAME AS TONIGHT...WHICH IS THE
CENTRAL 1/3 OF THE FORECAST AREA...SO WE MAY HAVE TO CONSIDER A
HEADLINE FOR THAT DEPENDING ON HOW MUCH RAIN FALLS TONIGHT.

PATTERN DOES NOT CHANGE THROUGH MID WEEK. OUR NRN ZONES SHOULD BE
THE COOLEST AND SRN ZONES THE WARMEST...HIGHS MAINLY 70S NORTH AND
80S SOUTH. IT DOES APPEAR THAT THE HIGHEST POTENTIAL FOR HEAVY
RAIN MAY SHIFT TO OUR NORTHERN ZONES WEDNESDAY NIGHT.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 300 PM CDT MON AUG 25 2014

WE SLOWLY GET OUT OF THE WET PATTERN. THE OPERATIONAL 12Z GFS HAS
CONTINUED TO TREND SLIGHTLY JUST A BIT FASTER THAN THE ECMWF AND
CANADIAN MODELS IN REGARDS TO THE EWD PROGRESSION OF THE CLOSED
LOW AT 500 MB AT THE BEGINNING OF THIS PERIOD.

THE MID LEVEL TROUGH AXIS PROBABLY WILL NOT MOVE EAST OF OUR AREA
UNTIL SATURDAY. KEPT PREVIOUS TREND OF DECREASING POPS FROM WEST
TO EAST...WITH NO CHANCE OF PCPN MENTIONED IN THE FORECAST BY
SATURDAY NIGHT. A BRIEF PERIOD OF SHORTWAVE RIDGING IS EXPECTED
FOR SUNDAY...BUT THIS WILL CHANGE EARLY NEXT WEEK AS TROUGHING
INCREASES TO OUR WEST. THE 12Z ECMWF DOES BRING PCPN BACK IN FOR
SUNDAY NIGHT/MONDAY. ITS QPF SEEMED OVERDONE BUT DID INCLUDE SOME
20-30 PERCENT POPS BASED ON A BLEND OF ALL MODEL OUTPUT.

&&

.AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1126 PM CDT MON AUG 25 2014

SCATTERED THUNDERSTORMS HAD DEVELOPED WEST OF KOMA AND NORTHWEST
OF KLNK AROUND 04Z. PERIODS OF THUNDERSTORMS WILL BE LIKELY AT
BOTH SITES THROUGH ABOUT 10Z WITH TEMPO MVFR CIGS AND VSBYS. SOME
BREAK IN THE CONVECTION INDICATED BY SHORT RANGE MODELS AFTER 12Z
AS LOW LEVEL JET WEAKENS WITH VFR CONDITIONS FOR MUCH OF THE
REMAINDER OF THE PERIOD. KOFK IS EXPECTED TO BE NORTH OF THE
ACTIVITY WITH SOME CHANCE LATE IN THE PERIOD AS BOUNDARY LIFTS
FURTHER NORTH.

&&

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

$$

SHORT TERM...MILLER
LONG TERM...MILLER
AVIATION...FOBERT


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