Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 172345
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
645 PM CDT SUN AUG 17 2014

.SHORT TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 305 PM CDT SUN AUG 17 2014

...OUR PATTERN REMAINS UNSETTLED...AND WARMER THIS WEEK...

FORECAST CHALLENGES FOR THE SHORT TERM WILL BE THUNDERSTORM
CHANCES AND SEVERE POTENTIAL TONIGHT THROUGH MONDAY EARLY
AFTERNOON.

IT LOOKED FAIRLY QUIET WEATHER TO BEGIN THIS EVENING...HOWEVER IT
SEEMS LIKE THE SHORT RANGE MODELS ARE A BIT UNDERDONE WITH THE
CONVECTION OVER CENTRAL SOUTH DAKOTA BASES ON THE LATEST RADAR.
THE HRRR HAS A SHORTWAVE AND CONVECTION THAT DROPS SOUTHEAST
ACROSS THE FORECAST AREA. THIS EVENING...WHILE THE OTHER MODELS
ARE SLOWER AND LESS AGGRESSIVE UNTIL LATER TONIGHT. EVEN THE 18Z
NAM IS STILL DRY THIS EVENING. NOT SURE HOW HIGH TO GO EARLY...BUT
WILL INCLUDE ISOLATED THUNDERSTORMS FOR PARTS OF NORTHEAST
NEBRASKA EARLY THIS EVENING. THE STORM PREDICTION CENTER DOES HAVE
A SEVERE THUNDERSTORM WATCH OUT FOR COUNTIES JUST TO THE WEST OF
OUR FORECAST AREA THIS EVENING AND THE SLIGHT RISK FOR SEVERE
WEATHER DOES CLIP OUR WESTERN FORECAST AREA COUNTIES.

THE 12Z UPPER AIR MAPS SHOWED A RIDGE OVER THE SOUTHWEST U.S. WITH A
CLOSED LOW OVER SASKATCHEWAN AND LEADING SHORTWAVE TROF ENERGY OVER
MINNESOTA.  THE STRONGER HEIGHT FALLS AT H5 WERE NOTED OVER
CANADA...ASSOCIATED WITH THIS NORTHERN SYSTEM.  THERE WERE RIBBONS
OF POOLED H7 MOISTURE OVER THE PLAINS WITH THE H7 THERMAL RIDGE OVER
WESTERN NEBRASKA AND COLORADO.  SIMILAR PATTERNS WERE NOTED AT H85.
THE OAX SOUNDING HAD A PWAT OF 1.44 INCHES WHICH WAS 134% OF NORMAL.
A MAX OF 185% OF NORMAL WAS CENTERED OVER KMPX.

AS THE EVENING PROGRESSES...A LOW LEVEL JET INCREASES TO 35-40KTS
OVER CENTRAL NEBRASKA...MEANWHILE THE SHORTWAVE TROF ENERGY OVER
CANADA EXTENDS SOUTHWARD INTO THE PLAINS. UPPER LEVEL JET
SUPPORT...OMEGA... FRONTOGENESIS AND THETA-E ADVECTION ALL
INCREASE. AS A RESULT...THE DETERMINISTIC MODELS INCREASE
CONVECTION OVER THE DAKOTAS AND THIS CONVECTION EXTENDS SOUTHWARD
INTO EASTERN NEBRASKA AND IOWA TONIGHT AND MONDAY. THERE IS A
GOOD H7 WARM AIR ADVECTION SIGNAL AND GOOD 7-8 DEG C H7 DEWPOINTS.
EXPECTED TRENDS LATER TONIGHT ARE WELL HANDLED BY THE CURRENT
FORECAST WITH INCREASING POPS INTO THE LIKELY CATEGORY AND WILL
TREND FARTHER SOUTH TO COVER POTENTIAL FOR INCREASED CONVERGENCE
CLOSER TO THE SURFACE LOW.

DEEP LAYER SHEAR IS FROM 30- 40KTS TONIGHT...HOWEVER DROPS CLOSER
TO 30KTS MONDAY. THE SURFACE AND H85 FRONT ARE STILL IN EASTERN
NEBRASKA MONDAY MORNING...AND GRADUALLY PUSH OUT OF THE FORECAST
AREA BY 00Z MONDAY. INSTABILITY IS 500-2000J/KG TONIGHT...BUT
INCREASES TO 3000+ MONDAY. FORECAST SOUNDINGS LOOK TO FAVOR
ELEVATED STORMS TONIGHT...HOWEVER THEY ARE MORE SURFACE BASED FOR
MONDAY. ALTHOUGH FREEZING LEVELS ARE HIGHER AND INSTABILITY IS
O.K. STRONGER SHEAR...PLUME OF STEEPER LAPSE RATES AND BETTER LOW
AND MID LEVEL FORCING MAY SUPPORT SOME SEVERE STORMS. SEVERE
WEATHER CHANCES CONTINUE INTO MONDAY AS THUNDERSTORMS WILL BE
ONGOING WITH INCREASED INSTABILITY...ALTHOUGH FORCING AND SHEAR
APPEAR TO BE NOT AS HIGH. TREND WITH HIGHER POPS IN THE
AM...DECREASING FROM WEST TO EAST IN THE AFTERNOON. STORM MOTION
IS AROUND 20KTS...BUT WITH HIGH PWATS/H7 DEWPOINTS AND POTENTIAL
FOR STORMS MOVING OVER THE SAME AREA COULD PRODUCE HEAVY RAIN.

MAINLY DRY FOR MONDAY NIGHT INTO TUESDAY WITH A WARM FRONT
SITUATED OVER NORTHERN KANSAS. THERE IS LIFT OVER THE FRONT AND
THE FRONT LIFTS NORTH TUESDAY NIGHT AND WEDNESDAY...SO HAVE
SCATTERED THUNDERSTORMS MENTIONED. WARMER HIGHS IN THE 90S CAN BE
EXPECTED SOUTH OF THE FRONT.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 305 PM CDT SUN AUG 17 2014

STILL QUITE A FEW MODEL DIFFERENCES WEDNESDAY NIGHT THROUGH
SUNDAY. IT LOOKS LIKE A FRONT WILL BE IN THE AREA WEDNESDAY NIGHT
THROUGH FRIDAY...WITH A MID LEVEL RIDGE TO OUR SOUTH AND A
FLATTER...TROF INFLUENCE TO OUR NORTH. WARM H85 TEMPS FROM 20-24
DEG C PERSIST THROUGH FRIDAY NIGHT...HOWEVER THE EC BRINGS COOLER
WEATHER IN FOR SATURDAY...WHILE THE GFS HOLDS OFF UNTIL SUNDAY
NIGHT.

&&

.AVIATION...(00Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 622 PM CDT SUN AUG 17 2014

REGIONAL RADAR THIS EVENING REVEALING SEVERAL AREAS OF CONVECTION
FROM CNTRL NEB INTO WRN/CNTRL SD PUSHING TO THE SE. GIVEN
THIS...TIMING CONVECTION AT EACH TERMINAL IS PROBLEMATIC AT BEST.
FOR KOFK...EXPECT COMPLEX DROPPING OUT OF SD WILL BE THE ONE TO
AFFECT KOFK. MODEL GUIDANCE/TIME TRAJECTORY INDICATE ACTIVITY
SHOULD BE MOVING IN AROUND 03Z THIS EVENING. AT THIS
POINT...UNSURE IF SECONDARY LINE OF TSRA CURRENTLY OVER WRN SD
WILL HOLD TOGETHER TO BE A FACTOR AT KOFK. THUS WILL NOT INCLUDE
TEMPO GROUP.

KLNK...GIVEN LATEST TRAJECTORY OF SEVERE TS CELL CURRENTLY IN
CNTRL NEB...APPEARS THAT MOVEMENT WILL TAKE IT JUST WEST OF KLNK.
HOWEVER...SEEMS TO BE AN OUTSIDE CHANCE FOR SOME TSRA ACTIVITY
EARLY MON MORNING...THUS HAVE INCLUDED PROB30 GROUP.

KOMA...AREA OBS ARE REVEALING A SUBTLE SFC BNDRY EXTENDING FROM
NERN NEB TO SRN MN. ENVIRONMENT ALONG THE MO RIVER VLY IS NOT VERY
FAVORABLE FOR INDUCING TSRA SO TSRA SHOULD NOT BE MUCH OF AN
ISSUE.


&&

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

$$

SHORT TERM...ZAPOTOCNY
LONG TERM...ZAPOTOCNY
AVIATION...DEE


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