Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 290557
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1257 AM CDT FRI AUG 29 2014

.SHORT TERM...(THIS EVENING THROUGH TONIGHT)
ISSUED AT 309 PM CDT THU AUG 28 2014

THE PRIMARY FORECAST CONCERN THROUGH TONIGHT WILL ONCE AGAIN
CENTER AROUND THE CHANCE OF THUNDERSTORMS...LOCALLY HEAVY
RAINFALL...AND POSSIBLE FLOODING. SHOWERS AND THUNDERSTORMS SHOULD
BE LESS WIDESPREAD AND OVERALL LESS HEAVY THAN WHAT WE SAW LAST
NIGHT. THE PRIMARY TRIGGERING MECHANISM CONTINUES TO BE AN UPPER
LEVEL TROUGH THAT HAS VERY SLOWLY BEEN SLIDING EAST ACROSS
NEBRASKA. THE 500 MB TROUGH AXIS WILL EVENTUALLY SLIDE EAST INTO
OUR CWA BY DAWN. AS LONG AS WE ARE OUT AHEAD OF THIS TROUGH AXIS
WE WILL SEE AT LEAST SOME CHANCE OF SHOWERS AND
THUNDERSTORMS...WHICH WILL BE THE CASE THROUGH THE NIGHT.

THE 18Z NAM AND A RUN OR TWO OF THE HRRR ARE NOW HINTING AT THE
POSSIBILITY OF SOME ELEVATED THUNDERSTORMS FORMING WITHIN A FEW
HOURS AFTER SUNSET AROUND HIGHWAY 281 OR A LITTLE EAST OF HIGHWAY
281. IF THESE STORMS FORM THEY WILL TRACK NORTHEAST AND COULD BE
HEAVY RAIN PRODUCERS WITH AN OUTSIDE CHANCE OF A LOW END SEVERE
HAIL OR WIND EVENT. INSTABILITY HAS BEEN RATHER LOW TODAY DUE TO
THE EXTENSIVE CLOUD COVER...WHICH IS THE PRIMARY LIMITING FACTOR
FOR SEVERE POTENTIAL. IN ADDITION...THE DEEP LAYER WIND SHEAR IS
ONLY AROUND 30 KTS...WHICH IS WEAK TO MODEST AND CERTAINLY NOT
OVERLY IMPRESSIVE FOR SEVERE POTENTIAL. THEREFORE...GIVEN A FAIRLY
SIMILAR MOIST ENVIRONMENT TO LAST NIGHT BEING LOCATED OUT AHEAD OF
THE UPPER TROUGH...WITH JUST A BIT LESS LIFT OUR PRIMARY CONCERN
WILL REALLY CONTINUE TO BE HEAVY RAIN...BUT JUST LIKELY NOT AS
WIDESPREAD AS THE OTHER NIGHT. THE GROUND IS VERY SATURATED ACROSS
PRETTY MUCH OUR ENTIRE FORECAST AREA SO ANY HEAVY RAIN WILL RESULT
IN RUNOFF AND POSSIBLE FLOODING. AM MOST CONCERNED FOR THE AREA
ALONG AND EAST OF HIGHWAY 281 BASED ON THE LATEST 18Z NAM.
OVERALL...THE PROBABILITY OF RAIN IS LOWER TONIGHT THAN LAST
NIGHT GIVEN THAT THE COVERAGE AREA WILL BE LESS AND IT IS HARD TO
PIN POINT EXACTLY WHERE THE THUNDERSTORMS WILL DEVELOP WITHIN THE
MORE BROAD FAVORABLE ZONE.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 309 PM CDT THU AUG 28 2014

FORECAST FOCUS IS ON THE CHANCES OF STORMS FRIDAY AND THEN CHANCES
OF SEVERE STORMS ON SUNDAY.

MODELS ARE IN GOOD AGREEMENT WITH MOVING AND TIMING OF MAJOR
FEATURES AT LEAST THROUGH MONDAY. IN GENERAL THE ATMOSPHERE IS
FORECAST TO MORPH FROM A CUTOFF LOW PATTERN BACK TO A MORE ZONAL
FLOW...SO OUT OF A HEAVY RAIN PATTERN AND BACK INTO A SEVERE WEATHER
TYPE REGIME.

THE LOW PRESSURE AREA THAT HAD BEEN PARKED OVER THE CENTRAL ROCKIES
THE LAST SEVERAL DAYS WILL EJECT EASTWARD ON FRIDAY AND LEAVE DRY
WEATHER BEHIND. AS IT MOVES THROUGH THERE WILL BE A THREAT OF
STORMS...BUT MAINLY OVER THE EASTERN THIRD OF THE AREA ON FRIDAY
AFTERNOON AND EARLY EVENING.

A RIDGE BUILDS OVER THE AREA ON SATURDAY BRINGING THE FIRST DRY AND
WARM DAY IN QUITE A WHILE. LOW CHANCES OF STORMS ARE BACK IN THE
FORECAST FOR SATURDAY NIGHT AND SUNDAY MORNING WITH A WEAK WAVE
MOVING ACROSS THE AREA.

HOWEVER...THE CHANCE OF STORMS FROM MID DAY SUNDAY INTO THE EVENING
IS MORE IMPRESSIVE. A COLD FRONT AND FAIRLY STRONG MID LEVEL WAVE
MOVE THROUGH DURING THAT TIME FRAME. MOST MODELS ARE IN AGREEMENT
WITH THE THE TIMING AN STRENGTH OF THE SYSTEM. THE STRONG
INSTABILITY AND GOOD SHEAR ARE MORE COMMON FOR MAY THAN AUGUST. SO
THERE IS A THREAT OF DAMAGING WINDS AND LARGE HAIL WITH STORMS THAT
DEVELOP. AS WITH ANY FORECAST OF CONVECTION SO MANY DAYS OUT THE
MODELS WILL LIKELY CHANGE...SO WE WILL CONTINUE TO MONITOR IT.

AS FOR THE WORK WEEK (MONDAY THROUGH THURSDAY)...OVERALL...MUCH
DRIER THAN THIS LAST WEEK...BUT HARD TO RULE OUT A HIT AND MISS
AFTERNOON AND EVENING STORM ESPECIALLY MONDAY...BUT THE MODELS ARE
STILL WAFFLING WITH TIMING AND STRENGTH OF FEATURES SO WILL LEAVE
DRY OR LOW PROBABILITIES UNTIL OUR CONFIDENCE RISES MORE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1252 AM CDT FRI AUG 29 2014

VFR CONDITIONS ARE FORECAST. WIND WILL REMAIN LIGHT AND SKY COVER
WILL REMAIN MID-HIGH LEVEL. DISCOUNTING FOG AND STRATUS ADVERTISED
BY THE NAM NUMERICAL MODEL. WE COULD GET A THUNDERSHOWER DURING
THE DAY FRIDAY ASSOCIATED WITH A PASSING TROUGH AXIS...BUT CHANCES
ARE FAIRLY LOW AND TIMING IS DIFFICULT TO DETERMINE.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$

SHORT TERM...WESELY
LONG TERM...EDDY
AVIATION...HEINLEIN


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