Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 311824
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
124 PM CDT SUN AUG 31 2014

.UPDATE...
ISSUED AT 123 PM CDT SUN AUG 31 2014

HAVE BEEN SEEING CLOUDS BEGIN TO BREAK UP SLIGHTLY BY EARLY THIS
AFTERNOON...BUT WITH TEMPERATURES RUNNING BEHIND FROM FORECAST
HOURLY TEMPERATURES DID ADJUST HIGHS DOWN A FEW DEGREES ACROSS
MUCH OF THE FORECAST AREA FOR TODAY. STARTING TO SEE A BIT OF
TOWERING AND CUMULONIMBUS ACROSS PARTS OF THE AREA AND WITH STEEP
MID-LEVEL LAPSE RATES CONTRIBUTING TO AN INCREASE IN
INSTABILITY...SHOULD CONTINUE TO SEE SCATTERED SHOWERS AND STORMS
ACROSS THE FORECAST AREA THIS AFTERNOON. THERE REALLY ISN/T MUCH
FOR INSTABILITY THOUGH SO THINKING STORM ACTIVITY WILL BE MORE
ISOLATED TO SCATTERED IN COVERAGE. IN TERMS OF SEVERE CHANCES YET
TODAY...WITH THE COLD FRONT COMPLETELY THROUGH THE AREA AND JUST
MARGINAL INSTABILITY NOT ANTICIPATING A HIGH THREAT FOR SEVERE
STORMS. THE PV ANOMALY IS STILL OUT OVER SOUTHWEST WYOMING AND SO
EXPECT ACTIVITY TO INCREASE LATER THIS AFTERNOON AS IT MOVES
CLOSER. THERE IS A LOT OF SHEAR BEHIND THE FRONT SO IF A FEW
STRONGER UPDRAFTS ARE ABLE TO BE SUSTAINED CAN/T DISCOUNT GETTING
A FEW STORMS WITH LARGE HAIL OR STRONG WINDS.

UPDATE ISSUED AT 936 AM CDT SUN AUG 31 2014

FORECAST HAS BEEN UPDATED FOR PRECIPITATION TRENDS THIS MORNING.
HIGHER COVERAGE OF SHOWERS ACROSS THE WESTERN SANDHILLS PROMPTED
AN INCREASE IN RAIN CHANCES THIS MORNING AS POST FRONTAL ACTIVITY
MOVES ACROSS WESTERN NEBRASKA. THIS IS EXPECTED TO DIMINISH
THROUGH THE LATE MORNING HOURS. FOR THE AFTERNOON...THE FORECAST
LOOKS TO BE ON TRACK WITH AT LEAST SCATTERED SHOWERS AND
THUNDERSTORMS AS THE PRIMARY SHORTWAVE TROUGH PROGRESSES EAST OUT
OF WYOMING. SEVERE CHANCES WILL LIKELY BE DETERMINED BY LOCATION
OF THE COLD FRONT WHICH HAD BEEN MAKING EASTWARD PROGRESSION THIS
MORNING WITH THE HELP OF OUTFLOW FROM ONGOING ACTIVITY. ONE
CONCERN IN THE LOCAL AREA IS THE INCREASING CLOUDS WHICH WILL
PROGRESS EAST AND SHOULD ENCOMPASS MUCH OF THE FORECAST AREA BY
18Z. THIS MAY INHIBIT THE DEVELOPMENT OF INSTABILITY TO HELP FUEL
STORMS. WILL CONTINUE TO CLOSELY MONITOR INTO THE AFTERNOON.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 339 AM CDT SUN AUG 31 2014

MESSY SETUP FOR CONVECTIVE TRENDS IN THE NEXT 24 HOURS AS SEVERAL
WEAKER PV ANOMALIES MOVE OUT OF THE APPROACHING UPPER TROUGH. THESE
UPPER PV ANOMALIES HAVE HELPED TO ENHANCE LOW LEVEL CONVERGENCE ON
SEVERAL BOUNDARIES ACROSS THE CENTRAL PLAINS AND WHEN COMBINED WITH
A DECENT LLJ WHICH DEVELOPED AHEAD OF THE MAIN LEE SFC TROUGH...HAVE
DEVELOPED WEAK CONVECTION ACROSS THE FCST AREA EARLIER THIS EVENING
AND NOW MOVING OUT OF THE AREA. IR SAT PICS INDICATING CLOUD TOPS
WARMING ACROSS NEB CURRENTLY...THOUGH COOLING JUST TO THE SOUTH
ACROSS NW KS AS A CONVECTIVE CLUSTER MOVES EAST THERE WHERE BETTER
MID LEVEL LAPSE RATES EXIST. NEXT MORE SIGNIFICANT PV ANOMALY MOVING
ACROSS SRN ID AND HELPING TO GENERATE MORE TSRA ACROSS SRN WY. AS
THE NRN MOST PV ANOMALY ACROSS SD CONTINUES TO MOVE NEWD TODAY...THE
MEAN SFC TROUGH POSITION WILL REMAIN ACROSS THE CENTRAL PORTION OF
THE FCST AREA AS EVIDENCED BY LIGHT WINDS FOR THE MORNING HOURS. THE
AFOREMENTIONED STRONGER PV ANOMALY WILL MOVE THE MEAN UPPER TROUGH
AXIS TO COINCIDE WITH THE SFC TROUGH AND ENHANCE LOW LEVEL
CONVERGENCE BY AFTERNOON. AHEAD OF THIS...LOW LEVEL MOISTURE WILL
REMAIN POOLED IN THE ERN HALF OF THE STATE...AND A REDEVELOPMENT OF
THE LLJ MAINLY EAST OF THE FCST AREA TONIGHT.

AS FOR SENSIBLE WEATHER...SHOWERS WITH EMBEDDED TSRA WILL PROGRESS
INTO THE ERN PANHANDLE THIS MORNING AND INTO THE SANDHILLS DURING
THE AFTERNOON. ADDITIONAL TSRA EXPECTED TO DEVELOP ALONG THE
DEVELOPING FRONT BY MID AFTERNOON...THOUGH COVERAGE AND INTENSITY
REMAIN UNCERTAIN IN WRN NEB DUE TO LIMITED EXPECTED INSOLATION DUE
TO EXPECTED MID LEVEL CLOUD COVER. SHOULD THE CLOUDS BREAK AHEAD OF
THE SHOWERS BY AFTERNOON...A QUICKLY DESTABILIZING ATMOSPHERE WOULD
PROVIDE A BETTER CHANCE FOR STRONG TSRA AND WITH GOOD DEEP LAYER
SHEAR A FEW STORMS COULD REACH SEVERE LIMITS...WITH LARGE HAIL AND
DAMAGING WINDS THE MAIN SEVERE WEATHER THREATS. AT THIS TIME BELIEVE
THE BEST CHANCE FOR THIS SCENARIO TO HAPPEN WOULD BE EAST OF A LINE
FROM STOCKVILLE TO BROKEN BOW TO AINSWORTH...SIMILAR TO THE CURRENT
SPC DAY1 OUTLOOK. TSRA SHOULD GROW UPSCALE AFTER 02Z OR SO...MAINLY
FURTHER EAST OF THE FCST AREA AND HAVE LIMITED POPS AFTER MIDNIGHT
TONIGHT TO THE NORTHEASTERN MOST AREA.

HIGH TEMPS WILL ALSO BE DEPENDENT ON CLOUD COVER TODAY AND WILL
LIKELY BE HELD DOWN THE GREATEST IN PORTIONS OF THE NORTHEAST
PANHANDLE.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 339 AM CDT SUN AUG 31 2014

12Z MONDAY AND BEYOND. ZONAL TO SLIGHTLY NORTHWESTERLY FLOW ALOFT
WILL USHER ANOTHER PV ANOMALY ACROSS THE NORTHERN PLAINS MONDAY
AFTERNOON AND EVENING...BRINGING A CHANCE FOR SHOWERS AND STORMS
TO OUR NORTHERN COUNTIES. THE MODELS ARE PROGGING A WEAKLY
UNSTABLE ATMOSPHERE BY LATE AFTERNOON...BUT BULK SHEAR VALUES
INCREASE TO THE 30-40 KT RANGE WHEN STORM INITIATION IS
ANTICIPATED...A STRONG STORM OR TWO IS POSSIBLE. THIS ACTIVITY
WILL SHIFT EAST INTO NORTH CENTRAL NEBRASKA LATE EVENING AND EARLY
ON TUESDAY...AND FOR THIS WILL CARRY LOW END CHANCE POPS ACROSS
OUR NORTHEASTERN ZONES THROUGH 12Z TUESDAY. THE GFS REMAINS FAIRLY
PROGRESSIVE...INDICATING THAT SUFFICIENT FORCING FOR PRECIPITATION
WILL LARGELY BE EAST OF THE CWA BY 06Z TUESDAY...THE FORECAST WAS
TRENDED TOWARD THE SLOWER SOLUTION PROGGED BY THE 31.00Z NAM.

ZONAL FLOW ONCE AGAIN BECOMES ESTABLISHED ACROSS THE FORECAST AREA
ON TUESDAY AS A PACIFIC NORTHWEST TROUGH DIGS SOUTH INTO
WASHINGTON.  THIS WILL PROVIDE FOR DRY CONDITIONS THROUGH AT LEAST
LATE THURSDAY AS NO MAJOR ATMOSPHERIC PERTURBATIONS ARE PROGGED TO
IMPACT THE REGION. ON THURSDAY HOWEVER THE UPPER PATTERN BACKS TO
SOUTHWESTERLY AS THE PAC NW TROUGH ADVANCES ALONG THE US/CANADIAN
BORDER TOWARD CENTRAL SASKATCHEWAN.  IN RESPONSE TO THE EASTWARD
PROGRESSION OF THE TROUGH...SFC LOW PRESSURE WILL DEEPEN ACROSS THE
HIGH PLAINS AND BE FORCED EAST WITH A COLD FRONT.  WITH A STRONG LOW
LEVEL BAROCLINIC ZONE IN PLACE...ANY DISTURBANCE WOULD OPERATE ON
THE FRONT...POTENTIALLY ALLOWING FOR STORMS.  WILL LEAVE THE CR
ALLBLEND PROCEDURE FORECAST AS IS FOR NOW...WHICH INDICATES SLIGHT
CHANCE TO CHANCE STORMS OVER MUCH OF THE FORECAST AREA BEGINNING
LATE THURSDAY THROUGH THE REMAINDER OF THE EXTENDED.

LOOKING AT TEMPERATURES THIS WEEK AND INTO THE WEEKEND...POST
FRONTAL CONDITIONS ON MONDAY WILL QUICKLY GIVE WAY TO RETURN FLOW
AND SOLID WAA INTO MIDWEEK.  HIGHS WILL GENERALLY BE IN THE 70S
TO LOWER 80S MONDAY...BUT WARM SEVERAL DEGREES BOTH TUESDAY AND
WEDNESDAY...SUCH THAT HIGHS ON WEDNESDAY SHOULD TOP OUT IN THE UPPER
80S TO LOWER 90S FOR MOST LOCATIONS.  THURSDAY THROUGH SATURDAY
TEMPERATURES WILL BE IMPACTED BY THE PASSAGE OF THE AFOREMENTIONED
STRONG LATE WEEK COLD FRONT.  WIDESPREAD HIGHS IN THE MID 70S SEEM
PLAUSIBLE AT THIS POINT IN TIME. CONCERNING LOWS...UPPER 40S TO
LOWER 50S WILL BE POSSIBLE ONCE AGAIN TUESDAY MORNING AS SFC HIGH
PRESSURE ALLOWS FOR CLEARING SKIES AND WEAK WIND.  LOW TEMPERATURES
ARE EXPECTED TO WARM SEVERAL DEGREES THROUGH MID-WEEK WITH LOW 60S
POSSIBLE BY WEDNESDAY...BUT COOL ONCE AGAIN BEHIND THE LATE WEEK
COLD FRONT WITH READINGS MAINLY IN THE 50S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 123 PM CDT SUN AUG 31 2014

MAIN AVIATION CONCERN IS TIMING WITH CHANCES FOR SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND EVENING. WEAK ACTIVITY EARLY THIS
IS EXPECTED TO BECOME MORE WIDESPREAD BY MID TO LATE AFTERNOON AS
A STRONG MID LEVEL SYSTEM MOVES INTO THE CENTRAL PLAINS.
PRECIPITATION ACTIVITY SHOULD BE MOVING OUT OF THE AREA BY MID
EVENING AND THROUGH MOST AREAS BY 06Z. THERE IS CONCERN FOR SOME
STRATUS LATE TONIGHT AND INTO THE MORNING HOURS MONDAY. HAVE
INCLUDED A MVFR CEILING AT BOTH KVTN AND KLBF TERMINALS...BUT THAT
MAY BE TOO HIGH AND WILL HAVE TO WATCH IF THE CATEGORY SHOULD BE
DROPPED TO IFR. CONDITIONS SHOULD IMPROVE BACK TO VFR WITH WEST TO
NORTHWEST WINDS BY LATE MORNING.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...BROOKS
SHORT TERM...JWS
LONG TERM...JACOBS
AVIATION...BROOKS








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