Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 052103
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
403 PM CDT TUE MAY 5 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 330 PM CDT TUE MAY 5 2015

THERE ARE SEVERAL FORECAST CONCERNS WITH THE PRIMARY CONCERN
CENTERING AROUND THUNDERSTORM CHANCES THROUGHOUT THE PERIOD.

THIS AFTERNOON...A BROKEN ARCHING LINE OF SHOWERS/WEAK
THUNDERSTORMS HAS DEVELOPED EARLY THIS AFTERNOON AND AT 330 PM
EXTENDED FROM DAWSON COUNTY SOUTHEAST INTO PHELPS COUNTY. WE HAD
AN EARLIER REPORT OF A FUNNEL CLOUD WITH ONE OF THESE DEVELOPING
SHOWERS WHILE IT WAS NEAR CAMBRIDGE. THERE IS A 0-3KM CAPE MAX IN
THIS AREA AS WELL AS A LOCALIZED MAXIMUM OF SFC VORTICITY...WHICH
IS RESULTING IN A SLIGHT ENHANCEMENT OF THE SPC NON-MESOSCALE
TORNADO PARAMETER TO THE VALUE OF 1. THEREFORE...ALTHOUGH MOST
SEVERE PARAMETERS ARE RATHER WEAK...WE CAN NOT RULE OUT A FUNNEL
OR WEAK LANDSPOUT TORNADO THROUGH LATE THIS AFTERNOON WEST OF HWY
10 IN NEBRASKA.

TONIGHT...EXPECT THE LOW LEVEL JET WILL INCREASE DURING THE
OVERNIGHT HOURS...WHICH SHOULD HELP ENABLE THE DEVELOPMENT OF
ADDITIONAL SHOWERS AND THUNDERSTORMS ACROSS OUR FORECAST AREA.
THE FAVORED REGION FOR PRECIPITATION EARLY THIS EVENING WILL BE
WEST OF HWY 281 SHIFTING TO AREAS ALONG AND EAST OF HWY 281 AFTER
MIDNIGHT. ELEVATED INSTABILITY WILL INCREASE SOME THROUGH THE
NIGHT BUT MUCAPE VALUES FOR MOST AREAS WILL REMAIN MARGINAL AT
LESS THAN 1000 J/KG. LOW LEVEL AND DEEP LAYER WIND SHEAR WILL BE
AROUND 30 KTS TONIGHT SO WE COULD ALSO SEE A FEW STRONG
THUNDERSTORMS THIS EVENING.

WEDNESDAY...THIS APPEARS TO BE ONE OF OUR BETTER CHANCES FOR
SEVERE THUNDERSTORMS. THE BIG QUESTION MARK WILL CENTER AROUND
INSTABILITY AS WE MAY SEE TOO MANY CLOUDS TO ALLOW FOR GOOD
DESTABILIZATION ACROSS PORTIONS OF OUR FORECAST AREA. OUR
SOUTHWESTERN ZONES WILL STAND THE BEST CHANCE AT SEEING SOME SUN
AND HENCE WILL LIKELY HAVE THE HIGHER INSTABILITY AND WILL BE THE
FOCUS OF CONVECTIVE INITIATION. BASED ON MOST FORECAST
MODELS...THUNDERSTORMS SHOULD DEVELOP BETWEEN 3 PM AND 5 PM. A
POTENT SHORT WAVE WILL BE TRACKING NORTH NORTHEAST ACROSS THE HIGH
PLAINS AND WILL RESULT IN A STRENGTHENING VERTICAL WIND
FIELD...ESPECIALLY A STRONG LOW LEVEL JET AS WE REACH EARLY
EVENING AND ENHANCED MID LEVEL FLOW. THEREFORE...EXPECT SUFFICIENT
DEEP LAYER SHEAR FOR SEVERE THUNDERSTORMS AND ALSO GOOD LOW LEVEL
SHEAR TO ALLOW MENTION OF A POSSIBLE TORNADO WITH THE STRONGER
STORMS. THE 0-1 KM SHEAR SHOULD BE IN THE 20 TO 30 KT RANGE AND
HELICITY VALUES COULD BE OVER 300 M2/S2 BY 7 PM.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 330 PM CDT TUE MAY 5 2015

VERY LITTLE CHANGE IN THE PATTERN THRU SUN. ACTIVE WITH PERIODIC
CHANCES OF TSTMS.

ALOFT: SPLIT FLOW WILL REMAIN OVER N AMERICA WITH THE LONGWAVE TROF
LOCKED IN OVER THE WRN USA. AS A RESULT...THE FLOW OVER THE CNTRL
PLAINS WILL REMAIN FROM THE SW IN THE WAKE OF WED`S DEPARTING TROF.
PART OF THE LOW CURRENTLY OVER BRITISH COLUMBIA WILL BREAK OFF AND
DROP S...SLOWLY MEANDERING THRU THE SW USA FRI-SAT. THE LAST 2 RUNS
OF THE DETERMINISTIC MODELS ARE CLUSTERED FAIRLY WELL WITH EACH
OTHER AND THE GEM/GFS/EC ENSEMBLE MEANS ON THIS LOW LIFTING NE THRU
THE CNTRL PLAINS SUN-MON. THE UKMET/EC AND THE EC ENSEMBLE MEAN ARE
ON THE FASTER SIDE OF THE GUIDANCE SPREAD. MODEL DISAGREEMENT/
UNCERTAINTY INCREASES MON-TUE. DOES THIS DEPARTING LOW DEAMPLIFY AS
IT HEADS NE AND THE NEXT LOW OR TROF MOVES INTO THE W? EITHER WAY IT
DOES APPEAR WE ARE IN FOR A COUPLE DAYS OF QUIET WX AS A RIDGE
OVERTAKES THE REGION.

EXPECT MULTIPLE LOW-AMPLITUDE SHORTWAVE TROFS TO BE EJECTED ACROSS
THE PLAINS FROM THE SW USA LOW. THESE TROFS WILL MODULATE TSTM
POTENTIAL.

SURFACE: THE COOL FRONT ASSOCIATED WITH THE DEPARTING LOW WILL MOVE
THRU WED NIGHT FOLLOWED BY A STRONGER NRN STREAM COOL FRONT LATE
THU. THE COMBINED FRONT WILL BECOME STATIONARY FROM W-E ACROSS KS
FRI-SAT. LEE CYCLOGENESIS WILL OCCUR WITH A LOW TRACKING ACROSS
KS/NEB SUN. SIGNIFICANT SVR WX WILL BE POSSIBLE NEAR AND JUST E AND
S OF THE LOW...AND TIMING/PLACEMENT OF THE LOW WILL DETERMINE.

OVERALL EXPECT TEMPS TO AVERAGE NEAR NORMAL THRU NEXT TUE...WITH
RAINFALL AT OR ABOVE NORMAL.

SOME DAILY DETAILS...

WED NIGHT: SCT TSTMS WILL PROBABLY BE ON-GOING DURING THE EVENING
AND GRADUALLY LIFT N AND E OF THE FCST AREA OVERNIGHT.

THU: THE DAY WILL BEGIN DRY FOR MOST IF NOT ALL OF THE FCST AREA AS
A SHORTWAVE RIDGE ARRIVES. THERE IS DISAGREEMENT ON WHERE THE FRONT
WILL BE DURING PEAK HEATING. THIS NOT ONLY COMPLICATES THE TEMP FCST
BUT IT ALSO WILL DETERMINE TSTM INITIATION. TEMPS ARE ONLY AVERAGE
CONFIDENCE. PRESENT INDICATIONS ARE THAT THE FRONT WILL BE JUST FAR
ENOUGH S AND E OF THE FCST AREA THAT STORM THREAT IS MINIMAL.

FRI-SAT: SHOULD BE FAIRLY QUIET. CAN`T COMPLETELY RULE OUT A COUPLE
SHWRS/TSTMS MEANDERING IN FROM THE W OR S. THERE IS VERY LITTLE
CURRENTLY DISCERNIBLE TO TRIGGER TSTMS OVER THE FCST AREA. TEMPS ARE
LOW CONFIDENCE DUE TO POTENTIAL FOR STRATUS.

SAT NIGHT-SUN: POTENT FORCING. NOT SURE YET HOW IT EVOLVES AND THE
TIMING WILL DETERMINE WHERE THE BOUNDARIES ARE DURING PEAK HEATING
SUN AFTERNOON. THIS WILL BE A DYNAMIC SYSTEM WITH STRONG WIND FIELDS
AT ALL LEVELS. ALL SVR WX POSSIBILITIES WILL BE IN PLAY OVER
PORTIONS OF (OR SOMEWHERE CLOSE TO) THE FCST AREA.

ALL INTERESTS SHOULD CONT TO MONITOR THE LATEST SPC OUTLOOKS AND
FOLLOW FCSTS AND THE HAZARDOUS WX OUTLOOK /HWO/ FROM THIS OFFICE.

MON: WE HAVE LINGERED LOW CHANCE OF TSTMS. WOULD HAVE PREFERRED TO
KEEP THE FCST DRY. THIS IS SOLELY TO ACCOUNT FOR POSSIBLE SLOWER
TIMING OF THIS LOW.

TUE: CURRENTLY LOOKING DRY.

&&

.AVIATION...(FOR THE 18Z KGRI/KEAR TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1232 PM CDT TUE MAY 5 2015

EXPECT TO SEE A FEW BREAKS IN THE LOW CLOUDS THIS AFTERNOON...BUT
EVEN THEN WE SHOULD STILL HAVE PLENTY OF MID TO HIGH CLOUDS
AROUND. LOW CLOUDS SHOULD ONCE AGAIN FILL IN AFTER DARK THIS
EVENING WITH LOWERING CEILINGS BY LATE EVENING INTO THE EARLY
MORNING HOURS. COULD VERY WELL SEE IFR OR LIFR CEILINGS AGAIN LATE
TONIGHT. THE CHANCE OF SHOWERS AND AN ISOLATED THUNDERSTORM WILL
INCREASE BY LATE EVENING. HOWEVER...WILL KEEP THUNDER OUT OF THE
TAF FOR NOW AS THE THUNDER POSSIBILITY IS MORE QUESTIONABLE. WE
MAY REMAIN SOCKED IN UNDER LOW CLOUDS THROUGH MUCH OF WEDNESDAY
MORNING.


&&

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

$$

SHORT TERM...WESELY
LONG TERM...HALBLAUB
AVIATION...WESELY


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