Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 021754
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1254 PM CDT SAT MAY 2 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 431 AM CDT SAT MAY 2 2015

BIGGEST ISSUE WILL BE DETERMINING TIME AND PLACEMENT OF POTENTIAL
THUNDERSTORMS THIS MORNING AND AGAIN THIS EVENING.

UPPER LEVEL FLOW IS ZONAL AND SPLIT. A LOW-AMPLITUDE PERTURBATION IS
EXITING THE AREA THIS MORNING...LEAVING A SMALL CHANCE OF
SHOWERS/THUNDERSTORMS IN OUR EAST EARLY THIS MORNING. THE BULK OF
THE DAY SHOULD BE DRY. THUNDERSTORMS COULD FIRE ALONG A SURFACE
TROUGH TO THE WEST OF THE CWA THIS AFTERNOON AND THE TROUGH COULD
MIGRATE EAST INTO OUR WESTERN CWA BY THIS EVENING...BRINGING ANY
THUNDERSTORMS WITH IT. I EXPECT ELEVATED BASES WITH ANY STORMS.
INSTABILITY IS LIMITED AND BULK SHEAR IN THE 0-6 KM LEVEL MAY MAKE
IT TO 30-35 KTS. THE SHEAR MAY BE POSSIBLY ENOUGH TO PRODUCE NICKEL
SIZE HAIL OUT OF SOME STORMS. ANY CONVECTION SHOULD DIE OUT BEFORE
MIDNIGHT AS ANY SUPPORT FROM THE LOW-LEVEL JET SHOULD BE WELL EAST
AND BULK SHEAR WILL WANE AFTER MIDNIGHT. THE NOSE OF THE LOW-LEVEL
JET SHOULD REMAIN SOUTH AND EVENTUALLY EAST OF THE CWA
TONIGHT...KEEPING SUPPORT FROM LOW-LEVEL CONVERGENCE CLEAR OF OUR
AREA. I WENT WITH THE HI RES NMM FOR HIGHS TODAY...CONSIDERING ITS
FAVORABLE RESULTS LATELY...AND I WENT WITH CONSRAW FOR LOWS AS WE
COULD BE WELL ABOVE NORMAL FOR LOWS...ACCORDING TO ENSEMBLES. THIS
EFFECTIVELY KEPT HIGHS SIMILAR TO THE PREVIOUS FORECAST IN THE LOWER
TO MID 80S FOR HIGHS TODAY AND LOWS MAINLY IN THE 50S TO PERHAPS
LOWER 60S IN SOME OF OUR NORTH CENTRAL KANSAS AREA. I WENT WITH
CONSRAW FOR WIND GUSTS FOR PART OF TONIGHT...WHICH GAVE A BIT HIGHER
VALUES THAN THE STANDARD ALGORITHM.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 431 AM CDT SAT MAY 2 2015

PRIMARY FORECAST CONCERN CONTINUES TO REVOLVE AROUND MULTIPLE
THUNDERSTORM CHANCES. PLENTY OF UNCERTAINTIES TO IRON OUT IN THE
COMING DAYS LEADING TO LOWER CONFIDENCE...MANY OF WHICH WILL
HOPEFULLY BECOME CLEARER WITH TIME AND BETTER MODEL AGREEMENT.

THERE REALLY HASNT BEEN ANY SIGNIFICANT CHANGES IN THE MODELS
LOOKING AT THE START OF THE LONG TERM PERIOD SUNDAY/SUNDAY NIGHT.
GENERALLY ZONAL FLOW IS EXPECTED TO BE IN PLACE IN THE UPPER LEVELS
ACROSS THE REGION...SET UP BETWEEN WEAK HIGH PRESSURE OVER THE SRN
PLAINS AND A DISTURBANCE NEAR THE US/CAN BORDER. BY 12Z...MODELS
ARENT IN TOO BAD OF AGREEMENT SHOWING THE ACCOMPANYING COLD FRONTAL
BOUNDARY APPROACHING FAR WRN PORTIONS OF THE CWA. DURING THE DAYTIME
HOURS...AS THAT NRN STREAM DISTURBANCE CONTINUES PUSHING EAST...THE
SFC FRONT IS EXPECTED TO DRIFT FURTHER SOUTH...BUT NOT BY A
SIGNIFICANT AMOUNT...AND EVEN BY 00Z HAS PUSHED PERHAPS INTO THE
CENTRAL PORTIONS OF THE CWA. OFF THE SWRN CONUS COAST IS AN AREA OF
LOW PRESSURE...AND MODELS SUGGEST A SHORTWAVE DISTURBANCE EJECTED
OUT AHEAD WILL PUSH THROUGH THE ROCKIES AND EMERGE ONTO THE PLAINS
LATE IN THE DAY. KEPT THE FORECAST THROUGH THE MORNING HOURS
DRY...WITH CHANCES DURING THE AFTERNOON AS LIFT INCREASES AS WELL AS
DAYTIME HEATING. SOME UNCERTAINTY WITH JUST HOW MUCH ACTIVITY
DEVELOPS PRIOR TO 00Z...SO POPS REMAIN ON THE LOWER SIDE...RAMPING
UP DURING THE EVENING/OVERNIGHT HOURS AS AN INCREASED LLJ PLAYS A
ROLE. MODELS CONTINUE TO SHOW DEWPOINTS RISING INTO THE 50S TO NEAR
60 DEGREES...WITH AFTERNOON HIGHS FORECAST TO REACH INTO THE 80S
AHEAD OF THE FRONT. MODEST AMOUNTS OF MUCAPE ARE EXPECTED TO DEVELOP
WITH DEEP LAYER SHEAR VALUES GENERALLY IN THE 25-35 KT RANGE.
POTENTIAL FOR AT LEAST A FEW STRONG/SEVERE THUNDERSTORMS
REMAINS...AND MOST OF THE CWA SITS IN THE MRGL DAY 2 OUTLOOK FROM
SPC. HAIL/WINDS ARE THE PRIMARY CONCERNS.

MORE UNCERTAINTY COMES INTO THE FORECAST AS WE GET INTO MONDAY /AND
REMAINS IN PLACE THROUGH THE REMAINDER OF THE FORECAST PERIOD/...AND
HIGH POPS REMAINS IN PLACE. ONE OF THE MAIN QUESTIONS IS WHERE THE
ULTIMATE POSITION OF THAT SFC FRONT ENDS UP...WHICH SHOULD GET MORE
OF A PUSH FROM THE PREVIOUS ROUND OF CONVECTION. MODELS ARE IN
DECENT AGREEMENT SHOWING THE POTENTIAL FOR THAT FRONT TO BE DRAPED
THROUGH THE SRN PORTIONS OF THE CWA DURING THE AFTERNOON/EVENING
HOURS. THAT ABOVE MENTIONED UPPER LEVEL LOW PRESSURE SYSTEM OFF THE
COAST OF CAL MOVES INLAND DURING THE DAY...AND LOOKS TO MOVE INTO AZ
BY EVENING. ADDITIONAL PRECIPITATION CHANCES WILL CONTINUE AS PIECES
OF SHORTWAVE ENERGY OUT AHEAD OF THE LOW MOVE THROUGH THE
REGION...AND LLJ WINDS PICK UP/INTERACT WITH THE SFC BOUNDARY IN THE
EVENING/OVERNIGHT HOURS. INSTABILITY SHOWN BY SOME MODELS IS MODEST
AT BEST...MAINLY IN THE LATE AFTERNOON...AND WANING OVERNIGHT. DEEP
LAYER SHEAR LOOKS TO BE SIMILAR /IF NOT A TOUCH LOWER/ THAN
SUNDAY...SO A FEW STRONG/MARGINALLY SVR STORMS NOT COMPLETELY OUT OF
THE QUESTION...BUT NOT LOOKING TO BE OVERLY WIDESPREAD. SRN PORTIONS
OF THE CWA SIT IN THE DAY 3 MRGL OUTLOOK. AGAIN HAIL/WINDS LOOK TO
BE THE PRIMARY CONCERNS.

TUESDAY/WEDNESDAY...LITTLE CHANGE WITH THE CR INIT/SUPERBLEND POPS.
AT 12Z TUESDAY...THE MAIN UPPER LEVEL LOW IS EXPECTED TO STILL BE
OVER THE DESERT SW...WHILE ANOTHER STRONGER LOW IS MOVING INTO THE
PAC NW REGION. THE DISTURBANCE HELPING DRIVE MON/MON NIGHTS ACTIVITY
IS EXPECTED TO BE SLIDING EAST...AND MODELS SUGGEST THE POTENTIAL
FOR MORE OF A BREAK DURING AT LEAST PART OF THE DAY TUESDAY. DURING
THE DAYTIME HOURS...THAT LOW LOOKS TO FILL AS IT SWINGS
E/NE...BECOMING SOMEWHAT PHASED IN WITH THAT PAC NW LOW. THAT TROUGH
STARTS SWINGING INTO THE PLAINS LATE IN THE DAY...SPARKING
ADDITIONAL ACTIVITY WHICH SLIDES IN FROM THE WEST THROUGH THE
OVERNIGHT HOURS. IT IS NOT A QUICK PASSAGE OF THAT UPPER LEVEL
DISTURBANCE...WITH MODELS SHOWING IT LINGERING AROUND AND
POTENTIALLY AFFECTING THE CWA THROUGH THE DAY ON WEDNESDAY AND
POSSIBLY WED NIGHT. MODELS IN THIS TIME FRAME SUGGEST A CONTINUED
LACK OF SIGNIFICANT INSTABILITY OR DEEP LAYER SHEAR VALUES...BUT
WILL HAVE TO SEE IF THAT TREND HOLDS UP IN THE COMING DAYS.
OVERALL SVR THREAT STILL A BIT UNCERTAIN.

HIGH TEMPS DURING THE MONDAY THROUGH WEDNESDAY TIME FRAME GENERALLY
EXPECTED TO RANGE FROM THE 60S TO LOWER/MID 70S.

THURSDAY/FRIDAY...THIS DISTURBANCE FINALLY LOOKS TO PUSH N/NE OF THE
AREA...AS THAT PAC NW LOW DIGS FURTHER SOUTH ALONG THE WEST COAST.
BY 12Z FRIDAY MODELS ARE IN GOOD AGREEMENT SHOWING THE PLACEMENT OF
THE LOW ROUGHLY IN THE NV AREA. POPS REMAIN IN THE FORECAST...AS THE
POTENTIAL FOR ADDITIONAL WEAKER WAVES MOVING OUT AHEAD OF THE LOW
INTO THE REGION REMAINS. WITH PLENTY OF UNCERTAINTY...POPS ARE IN
THE 20-30 PERCENT RANGE. HIGHS IN THE MID/UPPER 70S CURRENTLY
FORECAST.

&&

.AVIATION...(FOR THE 18Z KGRI/KEAR TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1254 PM CDT SAT MAY 2 2015

CONFIDENCE REMAINS REASONABLY HIGH IN VFR CEILING/VISIBILITY
THROUGHOUT THE PERIOD...WITH THE MAIN QUESTION MARK CONSISTING OF
WHETHER OR NOT EITHER SITE COULD POSSIBLY SEE A BRIEF PASSING
SHOWER/THUNDERSTORM PRIMARILY DURING THE 02Z-07Z TIME FRAME
TONIGHT. IN ADDITION...HAVE INTRODUCED A MENTION OF LOW LEVEL WIND
SHEAR (LLWS) FOR SEVERAL HOURS TONIGHT AT KGRI GIVEN THAT THERE
COULD EASILY BE AT LEAST A 30KT BULK SHEAR DIFFERENCE BETWEEN THE
SURFACE AND ROUGHLY 1200 FT AGL ...BUT HELD OFF AT KEAR WHERE THE
LOW LEVEL JET DOES NOT APPEAR TO BE QUITE AS STRONG. GETTING BACK
TO CHANCES FOR SHOWERS/STORMS TONIGHT...OPTED TO COVER THIS SLIM
POSSIBILITY WITH A GENERIC VICINITY THUNDERSTORM (VCTS)
MENTION...WHICH CAN OBVIOUSLY BE REMOVED OR "UPGRADED" TO A TEMPO
GROUP AS TRENDS BECOME CLEARER WITH TIME. SHOULD ANY STORMS HAPPEN
TO DIRECTLY AFFECT THE TERMINALS...A BRIEF PERIOD OF GUSTY WINDS
AND SMALL HAIL COULD OCCUR. OTHERWISE...ASSUMING NO THUNDERSTORM
INFLUENCES...PREVAILING BREEZES THROUGH THE PERIOD SHOULD REMAIN
OUT OF THE SOUTH AT AROUND 12KT OR LESS...WITH SOME SLIGHTLY
HIGHER GUSTS POSSIBLE AT TIMES MAINLY THIS AFTERNOON/EVENING.

&&

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

$$

SHORT TERM...HEINLEIN
LONG TERM...ADP
AVIATION...PFANNKUCH


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