Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 041732
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1232 PM CDT MON MAY 4 2015

.UPDATE...
ISSUED AT 1129 AM CDT MON MAY 4 2015

MULTIPLE SHORT-TERM UPDATES HAVE BEEN POSTED TO THE FCST. A
CONVECTIVELY GENERATED VORTEX /MCV/ IS LIFTING NE ACROSS THE FCST
AREA AND AN 88D LOOP SUGGESTS THE CENTER IS NEAR BELOIT KS. THERE
EVEN APPEARS TO BE A SFC REFLECTION/LOW IN SFC PLOTS.

A COUPLE NARROW BANDS OF TSTMS HAVE DEVELOPED OVER S-CNTRL NEB
ALONG AND JUST E OF HWY 281. MOST OF THE SHWR/TSTM ACTIVITY IS IN
THE NW SEMI-CIRCLE OF THIS CIRCULATION.

MUCAPE IS 250 J/KG OR LESS WHICH IS ENOUGH FOR LIGHTNING STRIKES
AND BRIEF HEAVY DOWNPOURS...BUT LITTLE ELSE.

AS CLOUD COVER THINS THIS AFTERNOON...EXPECT MODEST
DESTABILIZATION AND ADDITIONAL SCT COULD SHWRS/TSTMS REDEVELOP IN
NARROW ARCS/BANDS.

SEVERE: THE COOL FRONT THAT MOVED THRU SUN AFTERNOON/EVE EXTENDED
SW-NE ACROSS KS...FROM GCK-RSL-FRI-STJ. DESTABLIZATION WILL BE
GREATEST ALONG AND S OF THIS LINE AND THIS IS WHERE TSTM
INITIATION WILL OCCUR...MAINLY S AND E OF THE FCST AREA. THE NRN
FRINGE OF THE INSTABILITY WILL EXIST OVER N-CNTRL KS...WITH
1000-1500 J/KG OF MUCAPE. THERE WILL BE A FRONTAL INVERSION
/CINH/ IN PLACE...BUT ENOUGH HEATING COULD ALLOW FOR A FEW STORMS
TO DEVELOP ON THE COOL SIDE OF THE FRONT...WHERE SHEAR WOULD BE
GREATER AND ALLOW FOR BETTER STORM ORGANIATION.

ONE NEGATIVE FACTOR IS POOR MID-LVL LAPSE RATES. FCST CAPE
PROFILES LOOK SKINNY...BUT IT IS DIFFICULT TO KNOW THE EXACT
ENVIRONMENT SINCE MODEL CONVECTIVE SCHEMES ARE KICKING IN EARLY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 514 AM CDT MON MAY 4 2015

SIMILAR TO YESTERDAY...THE BIGGEST CHALLENGE WILL BE DETERMINING
CHANCES AND TIMING OF SHOWERS/THUNDERSTORMS AS WELL AS THE
POTENTIAL FOR STRONG STORMS. ANOTHER CHALLENGE WILL BE DETERMINING
HIGH TEMPERATURES FOR TODAY.

SYNOPTICALLY...WE CONTINUE THE SPLIT FLOW SCENARIO WHILE WE ARE
BETWEEN JET STREAMS. A BROAD NEGATIVELY TILTED MEAN TROUGH IN THE
WESTERN UNITED STATES NUDGES A LITTLE CLOSER AS A PERTURBATION A
SURFACE BOUNDARY HAS STALLED OVER THE FAR SOUTHEASTERN CWA. A MID-
LEVEL PERTURBATION WILL MOVE NORTHEAST OUT OF COLORADO/KANSAS INTO
OUR AREA BY MID-DAY. THIS WILL LIKELY SPARK SOME THUNDERSTORM
ACTIVITY NEAR AND NORTH OF THE STALLED FRONT. INSTABILITY COULD BE
AS HIGH AS 2000 J/KG. MID TO UPPER LEVEL FLOW WILL BE WEAK. BULK
SHEAR WILL BE WEAK AT MAYBE 20-30 KTS. THIS WILL BE ENOUGH FOR A
MINIMAL SEVERE THREAT...AT LEAST IN OUR SOUTHERN CWA...AND AN
ISOLATED TORNADO CAN NOT BE RULED OUT AS LOW-LEVEL SHEAR NEAR WILL
BE ENHANCED NEAR AND JUST NORTH OF THE SURFACE BOUNDARY.

HIGHS TODAY WILL BE TOUGH. THERE WILL BE A VERY LARGE TEMPERATURE
GRADIENT AS THE SURFACE FRONT REMAINS STATIONARY OVER THE SOUTHERN
CWA. THERE SHOULD BE PLENTY OF SKY COVER AS MODELS INDICATE AN
EXTENSIVE SHIELD OF STRATUS DEVELOPING. TEMPERATURES NORTH OF THE
BOUNDARY PROBABLY WILL NOT MAKE IT VERY FAR BECAUSE OF THIS AND
HAVE SIDED TOWARD COOLER THAN GUIDANCE NUMBERS FOR HIGHS. WE MAY
HAVE A HARD TIME BREAKING 60 IN SOME PLACES. I DECIDED TO GO WITH
A BLEND OF THE HI RES NMM AND THE RAP FOR HIGHS...AS THESE MODELS
HAVE DONE QUITE WELL LATELY. WENT WITH THE FAIRLY DEPENDABLE
SUPERBLEND FOR LOWS TONIGHT. WE COULD ALSO GET SOME DECENT GUSTS
TODAY NORTH OF THE BOUNDARY AS THE SURFACE PRESSURE GRADIENT WILL
BE A BIT TIGHT. I WENT WITH CONSRAW WIND GUSTS FOR TODAY...WHICH
IS GREATER THAN THE STANDARD WIND GUST ALGORITHM.

DETERMINING CHANCES OF PRECIPITATION WAS BASED ON ENSEMBLE DATA
AS WELL AS SUPERBLEND TRENDS. CONFIDENCE HAS NOT BEEN HIGH FOR
CHANCES OF PRECIPITATION AND CONTINUES TO BE LOW FOR TODAY AND
TONIGHT. WITH THE AFOREMENTIONED PERTURBATION FOR TODAY AND A BIT
OF A LOW-LEVEL JET TONIGHT...ALONG WITH THE BOUNDARY SHIFTING
NORTH TONIGHT...WE WILL HAVE A DECENT SHOT AT PRECIPITATION AT
ALMOST ANY POINT DURING THE SHORT TERM. ANY THREAT OF STRONG TO
SEVERE THUNDERSTORMS SHOULD REMAIN PRIMARILY IN THE AFTERNOON AND
EVENING.


.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 514 AM CDT MON MAY 4 2015

EXPECT UNSETTLED WEATHER THROUGH THE WEEK. THE MAIN WEATHER
FEATURE WILL BE AN UPPER LEVEL LOW THAT MOVES FROM THE CENTRAL
ROCKIES INTO THE CENTRAL PLAINS AND OPENS THE WAVE AS IT MOVES TO
THE NORTHEAST. ANOTHER UPPER LEVEL LOW MOVES INTO THE SOUTHWEST
CONUS LATER IN THE WEEK.

ON TUESDAY THE UPPER LOW IS STILL IN THE ROCKIES AND A WAVE MOVES
INTO THE PLAINS AHEAD OF THE UPPER LOW. THE BEST CHANCE FOR
THUNDERSTORMS WILL BE IN THE WESTERN PART OF THE AREA CLOSER TO
THE UPPER WAVE. BY TUESDAY NIGHT THE WAVE MOVES ONTO THE PLAINS
AND STARTS TO OPEN. THE THUNDERSTORMS SHOULD BE ACROSS THE ENTIRE
AREA. WEDNESDAY INTO WEDNESDAY NIGHT THE UPPER WAVE IS NEAREST TO
THE FORECAST AREA. THIS LOOKS TO BE SOME OF THE BEST CHANCES FOR
THUNDERSTORMS. DURING THE AFTERNOON AND EVENING HOURS...THE MUCAPE
INCREASES TO OVER 1500 J/KG AND SOME OF THESE STORMS COULD BE
STRONG TO SEVERE.

THE INITIAL UPPER WAVE MOVES TO THE NORTH ON THURSDAY AND EVEN
THOUGH THERE COULD BE SOME SHOWERS AND THUNDERSTORMS AROUND...THE
CHANCES WILL BE A LITTLE LESS THAN BEFORE. BY THURSDAY NIGHT THE
NEXT UPPER LOW IN THE SOUTHWEST CONUS AND THE FIRST WAVE FROM THIS
WAVE STARTS TO AFFECT THE AREA THURSDAY NIGHT INTO FRIDAY. FRIDAY
NIGHT INTO SATURDAY THE UPPER LOW CONTINUES TO DRIFT TO THE EAST
AND UPPER LEVEL WAVES CONTINUE TO MOVE INTO THE AREA...AND AS THE
UPPER LOW MOVES INTO THE PLAINS SATURDAY NIGHT INTO SUNDAY THERE
CONTINUES TO BE CHANCES FOR THUNDERSTORMS.

TEMPERATURES THROUGH THE PERIOD WILL BE AT LEAST SOMEWHAT
VARIABLE. TUESDAY THROUGH THURSDAY WILL BE WARM. THEN A WEAK COLD
FRONT MOVES THROUGH THE AREA THURSDAY AFTERNOON AND EVENING
BRINGING COOLER TEMPERATURES FOR FRIDAY. SATURDAY AND SUNDAY WILL
REMAIN A LITTLE COOLER BUT STILL AROUND OR EVEN ABOVE NORMAL
TEMPERATURES ARE EXPECTED.

&&

.AVIATION...(FOR THE 18Z KGRI/KEAR TAFS THROUGH 18Z TUE AFTERNOON)
ISSUED AT 1231 PM CDT MON MAY 4 2015

THIS AFTERNOON: VARIABLE CIGS BETWEEN MVFR AND VFR WITH IFR VSBYS
IN SHWRS/TSTMS POSSIBLE. NE WINDS 10-15 KTS. CONFIDENCE: LOW DUE
TO UNCERTAINTY ON CIGS AND OCCURRENCE/TIMING OF SHWRS/TSTMS.

TONIGHT: MVFR STRATUS CIGS SHOULD INVADE AND DEGRADE TO IFR AS
WARM FRONT LIFTS N. A PERIOD OF MVFR OR IFR VSBYS POSSIBLE IN
SHWRS AND POSSIBLE THUNDER. THEREAFTER...MVFR VSBYS POSSIBLE IN
PATCHY FOG AFTER 09Z. NE WINDS DIMINISH AND SHIFT TO SE.
CONFIDENCE: LOW ON ARRIVAL TIME OF STRATUS AND CIG CHANGES.

TUE THRU 18Z: IFR STRATUS/PATCHY MVFR FOG LIFTS TO MVFR BY 15Z. SE
WINDS INCREASE 10-15 KTS. CONFIDENCE: LOW

&&

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

$$

UPDATE...HALBLAUB
SHORT TERM...HEINLEIN
LONG TERM...JCB
AVIATION...HALBLAUB



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