Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 200528
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1228 AM CDT SUN APR 20 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 352 PM CDT SAT APR 19 2014

...MULTIPLE EPISODES OF TSTMS WILL BRING NEEDED RAINFALL TONIGHT
INTO TOMORROW WILL MINIMAL THREAT OF SEVERE...

ALOFT: WESTERLIES WERE SPLIT OVER THE CONUS. THE FAIRLY ZONAL
BRANCH ALONG THE US-CANADA BORDER WILL REMAIN STRONGER AND MORE
PROGRESSIVE. THE SRN BRANCH WILL BE MORE AMPLIFIED BUT WEAKER. THE
PRIMARY FEATURES TO IMPACT THE FCST AREA WILL BE A NRN STREAM
SHORTWAVE TROF THAT WILL MOVE INTO ONTARIO TONIGHT. THIS TROF WILL
BE FOLLOWED BY ANOTHER THAT WILL TRACK E ALONG THE US-CANADA
BORDER TONIGHT AND TOMORROW. THIS TROF WILL BE LOCATED OVER
MANITOBA BY SUNSET TOMORROW. THE SRN STREAM LOW CURRENTLY OVER NRN
MEX WILL ADVANCE INTO THE SRN PLAINS TOMORROW.

SURFACE: LOW PRES WAS OVER THE CANADIAN PRAIRIES...ASSOCIATED
WITH THE FIRST SHORTWAVE TROF. ITS COOL FRONT EXTENDED
S...BISECTING NEB TO A LEE-SIDE LOW OVER WRN KS. AT 19Z THE FRONT
WAS LOCATED ROUGHLY FROM ORD-KEARNEY-BEAVER CITY. THIS FRONT WILL
MAKE A LITTLE FORWARD PROGRESS TONIGHT-TOMORROW...AND WILL
PROBABLY BECOME MODIFIED BY TSTM COLD POOLS.

THE REST OF THIS AFTERNOON: PARTLY-MOSTLY CLOUDY. THE FIRST
STORMS SHOULD GO UP OVER WRN KS IN VICINITY OF THE LEE LOW AND
THEN APPROACH THE BEAVER CITY-PHILLIPSBURG AREA EARLY THIS
EVENING.

DEWPOINTS WERE IN THE UPPER 40S AND 700-500 MB LAPSE RATES WERE
VERY STEEP. HOWEVER...THE ELEVATED MIXED LAYER /EML/ AND POOR
MOISTURE HAS RESULTED IN A SKINNY CAPE PROFILE. DEEP LAYER SHEAR
WILL BE 25- 30 KTS NEAR THE FRONT...BUT ONLY 15-20 KTS AHEAD OF
IT.

15Z/SREF MAXIMUM MEAN MLCAPE IS FCST TO JUST BARELY REACH 1000
J/KG OVER N-CNTRL KS JUST PRIOR TO SUNSET. THEREAFTER...MUCAPE
WILL DECREASE. EXPECT A STRONG STORM OR TWO INITIALLY WITH HAIL
POSSIBLY UP TO NICKELS AND WIND GUSTS UP TO 50 MPH.

TONIGHT: TSTMS WILL MOVE IN FROM THE SW. THEY WILL BE OUTFLOW
DOMINANT DUE TO THE LACK OF STRONG SHEAR AND UNIDIRECTIONAL FLOW
PARALLEL TO THE FRONT. SO WHILE INDIVIDUAL STORM MOVEMENT
INITIALLY WILL BE ABOUT 23020KT...MOVEMENT COULD BE MODIFIED DUE
TO COLD POOL BOUNDARIES. INTERESTINGLY...WHILE THIS IS FAR FROM
AN IDEAL HEAVY RAIN SITUATION...ONCE THE LOW-LEVEL JET REDEVELOPS
...CORFIDI VECTORS DECREASE TO 10 KTS OR LESS. BY 06Z LLJ
CONVERGENCE WILL DIMINISH WITH MINIMAL FLOW INTO THE FRONT. SO
EXPECT A DECREASE IN TSTM COVERAGE BY MIDNIGHT.

FOR WHAT IT/S WORTH...THE 12Z WRF-NMM DEVELOPS ALL OF THE TSTMS
ALONG AND TO THE COOL SIDE OF THE FRONT.

FOG: RAIN UNDER THE FRONTAL INVERSION WILL SIGNIFICANTLY MOISTEN
THE LOW-LEVELS. WHAT THE REMNANT COLD POOLS DO TO THE WIND FIELD
REMAINS UNCERTAIN...BUT DID INCLUDE THE THREAT OF PATCHY FOG
WITHIN THE FRONTAL TROF 3AM-10AM SUN. TOUGH TO TELL HOW DENSE
VSBYS COULD BE.

SUN: VERY LOW CONFIDENCE IN CLOUD COVER AND TEMPS. THE DAY COULD
START OFF WITH A LOT OF STRATUS ON THE COOL SIDE OF THE FRONT.
THIS CASTS SIGNIFICANT DOUBT ON HIGH TEMPS.

THE APPROACH OF THE UPPER TROF WILL REIGNITE TSTMS IN A SOMEWHAT
MORE FAVORABLE ENVIRONMENT. TONIGHT/S RAIN WILL PUSH DEWPOINTS
INTO THE 50S. 15Z/SREF SUGGESTS MLCAPE OF 750-1000 J/KG IN THE
PRECONVECTIVE ENVIRONMENT. HOWEVER...ENVIRONMENTAL WIND FIELDS
WILL WEAKEN SIGNIFICANTLY. 0-6 KM SHEAR AT OR BELOW 10 KTS WILL
RESULT IN OUTFLOW DOMINANT PULSE-TYPE STORMS. THIS WILL LIMIT THE
THREAT TO HAIL UP TO THE SIZE OF NICKELS AT WORST. THE CAPE
PROFILE WILL BE SKINNY ONCE AGAIN.

WHERE TSTMS DEVELOP...HIGHLY LOCALIZED HEFTY RAINFALL LOOKS
PROBABLE. PRECIPITABLE WATER WILL BE 1-1.25" ...HIGHEST E OF HWY
281. THIS IS 2 STANDARD DEVIATIONS ABOVE NORMAL FOR MID APRIL.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 352 PM CDT SAT APR 19 2014

WE START OUT THE LONG TERM SUNDAY EVENING WITH A SPLIT FLOW
REGIME...WITH AN UPPER LEVEL JET WELL TO THE NORTH NEAR THE
CANADIAN BORDER AND TO THE SOUTH ACROSS TEXAS AND EAST INTO THE
NORTHERN GULF OF MEXICO. A SHORTWAVE TROUGH WILL CONTINUE TO MOVE
EAST ACROSS THE CENTRAL PLAINS WITH THE TROUGH AXIS CROSSING THE
CWA SUNDAY EVENING. DEWPOINTS WILL BE IN THE 50S...WHICH WILL HELP
BOOST INSTABILITY SOME...BUT IT STILL LOOKS FAIRLY MODEST MUCAPES
NOT LIKELY EXCEEDING 1000 J/KG. WIND SHEAR WILL BE WEAK AS
WELL...GENERALLY IN THE 5 TO 15 KT RANGE IN THE LOWEST 6 KM. THIS
WILL GIVE US A SHOT AT SOME STRONG TO MARGINALLY SEVERE
THUNDERSTORMS EARLY. HAIL WILL BE MAINLY WHAT TO WATCH OUT FOR AND
ANY STORMS SHOULD BE MORE PULSE-TYPE IN NATURE. ALTHOUGH WE STAND
A BETTER SHOT AT RAIN IN OUR SOUTHEAST WHERE MOISTURE IS MORE
BOUNTIFUL...WE PERHAPS STAND A BIT MORE OF A SHOT AT SOME SEVERE
HAIL IN OUR NORTH WHERE SHEAR MAY BE NEAR 20 KTS IN THE LOWEST 6
KM NEAR A SURFACE TROUGH/FRONTOLYTIC STATIONARY BOUNDARY...BUT
THIS WILL BE A FAIRLY SMALL WINDOW AS INSTABILITY DECREASES DURING
THE EVENING AND THE TROUGH AXIS MOVES EAST. SOME LOCATIONS COULD
GET A GOOD DOSE OF RAIN AS STORM MOTION WILL BE SLOW. THIS WILL BE
RATHER HIT OR MISS...BUT A BETTER CHANCE OF A SOAKING IN OUR
SOUTHEAST.

WIND WILL BE SIGNIFICANTLY STRONGER BEHIND THE TROUGH BY LATE
SUNDAY NIGHT INTO MONDAY MORNING WITH A TIGHTLY PACKED SURFACE
PRESSURE GRADIENT HELPING TO BOOST NORTH WIND. THIS SHOULD
DECREASE DURING THE AFTERNOON AS THE GRADIENT RELAXES AND A
SURFACE HIGH APPROACHES. WIND COULD STILL BE STRONG ENOUGH IN THE
AFTERNOON...HOWEVER...TO MENTION NEAR CRITICAL FIRE DANGER IN THE
HWO. WITH THE POTENTIAL FOR RAIN FROM SUNDAY AND SUNDAY
EVENING...OUR FUEL STATUS BY THEN IS QUESTIONABLE...BUT A MENTION
IN THE HWO PROBABLY WOULD NOT HURT.

TUESDAY SHOULD BE DRY WITH SHORTWAVE RIDGING PASSING BY...WITH
INCREASING WIND SPEEDS FROM WEST TO EAST WITH AN INCREASING
PRESSURE GRADIENT DUE TO A DEVELOPING TROUGH IN THE LEE SIDE OF
THE ROCKY MOUNTAINS.

BY WEDNESDAY...A SURFACE LOW IS FORECAST TO PULL OUT OF THE ROCKY
MOUNTAINS INTO THE NORTHERN GREAT PLAINS ASSOCIATED WITH A
NEGATIVELY TILTED SHORTWAVE. A NARROW WARM SECTOR WILL DEVELOP TO
THE SOUTH OF THE FRONT WHERE INSTABILITY WILL INCREASE. ALTHOUGH
THERE ARE CONSISTENCY ISSUES AMONG NUMERICAL MODELS AND
DIFFERENCES IN SOLUTION...THERE IS POTENTIAL FOR STORMS TO DEVELOP
ALONG THE LEE TROUGH/DRY LINE AND MOVE EAST AS THE COLD FRONT
SWEEPS INTO THE CENTRAL PLAINS. DEWPOINTS ALONG THE AXIS OF
INSTABILITY COULD HIT NEAR 60 DEGREES. BULK SHEAR WILL ALSO BE IN
THE 35 TO 40 KT RANGE. THIS ALONG WITH THE NEGATIVELY TILTED
TROUGH WILL GIVE US A DECENT SHOT AT SOME SEVERE STORMS WEDNESDAY
AFTERNOON AND INTO THE NIGHT.

WE DRY OUT BEHIND THE TROUGH AXIS HEADING INTO REST OF THE WORK
WEEK AND INTO THE WEEKEND.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1228 AM CDT SUN APR 20 2014

VFR CONDITIONS ARE FORECAST THROUGH THE NEXT 24 HOURS...BUT
CONVECTIVE ACTIVITY REMAINS POSSIBLE.

CLOUD COVER WITH BASE NEAR 15000FT AGL...GENERALLY SCATTERED TO
BROKEN IN NATURE...WILL REMAIN POSSIBLE TO START THE TAF
PERIOD...WITH THE CLOUD COVER BASE EXPECTED TO DECREASE TO AROUND
8000FT AGL THROUGH THE NEXT 24 HOURS. LOWER BASES NEAR 4000FT AGL
WILL ALSO BE POSSIBLE IF CONVECTIVE ACTIVITY IS REALIZED AT GRI
DURING THE TAF PERIOD. CONVECTIVE ACTIVITY IS CURRENTLY WEST OF
GRI...CLOSER TO EAR...HDE AND LXN. THIS ACTIVITY IS MOVING
NORTHEAST AND BASED ON ITS CURRENT MOMENT SHOULD MISS GRI TO THE
WEST AND NORTH. THAT BEING SAID...RADAR HAS INDICATED THIS
CONVECTIVE ACTIVITY ATTEMPTING TO EXPAND EAST AT TIMES. GIVEN THE
POTENTIAL THAT THIS CONVECTIVE ACTIVITY COULD EXPAND EAST...WENT
AHEAD WITH VCTS 06-09Z. BEYOND 09Z...DRY CONDITIONS ARE EXPECTED
AT GRI UNTIL 18Z...AT WHICH TIME A 30% CHANCE FOR CONVECTIVE
ACTIVITY WILL OVERTAKE THE AREA 18-06Z...THUS THE PROB30 GROUP IN
THE TAF. THE SURFACE WIND WILL START THE TAF PERIOD LIGHT AND
VARIABLE...BUT WILL EVENTUALLY BECOME SOUTH/SOUTHEASTERLY AS A
LOWER TROPOSPHERIC BAROCLINIC ZONE MOVES NORTHWEST ACROSS THE
AREA. THIS BAROCLINIC ZONE IS THEN EXPECTED TO MOVE BACK TO THE
SOUTHEAST BY SUNDAY EVENING...THUS RESULTING IN A ANOTHER LIGHT
AND VARIABLE SURFACE WIND FIELD 02Z ONWARD. VISIBILITY RESTRICTION
IS NOT CURRENTLY EXPECTED AT GRI THROUGH THE NEXT 24 HOURS.

&&

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

$$

SHORT TERM...HALBLAUB
LONG TERM...HEINLEIN
AVIATION...BRYANT



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