Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 262346
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
646 PM CDT TUE AUG 26 2014

.SYNOPSIS...
ISSUED AT 253 PM CDT TUE AUG 26 2014

UPPER LEVEL FLOW OVER THE CONUS AS OF 19Z TUESDAY WAS DEFINED BY A
FLATTENED ZONAL RIDGE FROM THE GREAT PLAINS EASTWARD...AND A DEEP
AND AMPLIFIED TROUGH MOVING OVER THE GREAT BASIN. AT THE SFC A LEE
SIDE LOW WAS POSITIONED IN SOUTHWEST COLORADO WITH A WARM FRONT
SLOWLY NUDGING NORTHWARD INTO SOUTHWEST AND CENTRAL KANSAS. A WEAK
LEE SIDE TROUGH EXTENDS JUST EAST OF THE FRONT RANGE TO THE NEBRASKA
PANHANDLE.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 253 PM CDT TUE AUG 26 2014

THE REMAINDER OF THIS AFTERNOON WILL BE QUIET ACROSS MOST OF THE
AREA. A CU FIELD CONTINUES TO DEEPEN ALONG A WEAK MID LEVEL FGEN
BAND NEAR THE PINE RIDGE. A FEW SHOWERS AND STORMS MAY DEVELOP AND
IMPACT THE NORTHWEST CORNER OF THE CWA. THE SHORTWAVE TROUGH
EXPECTED TO HELP FUEL SHOWER AND THUNDERSTORMS ACROSS THE CWA
TONIGHT IS STILL WELL OFF TO THE SOUTHWEST. WIDESPREAD POPS
FILTER INTO THE FORECAST AS THE SHORTWAVE APPROACHES AREA...WITH
LIKELY POPS STEADILY INTRODUCED AFTER 3Z AS SHOWERS AND STORMS MOVE
OUT OF EASTERN COLORADO AND NORTHWEST KANSAS. EXPECTING MORE
WIDESPREAD RAINFALL THAN MONDAY NIGHT DUE TO BETTER UPPER LEVEL
SUPPORT...HIGHLIGHTED BY A COUPLED JET STRUCTURE ALOFT WHICH WILL
HELP SUPPORT BROAD SUSTAINED LIFT. A SURGE OF MONSOONAL MOISTURE IS
ALSO SHOWN IN THE MODELS AS SOUTHWEST FLOW INCREASES...PUSHING PWATS
TO AROUND 2 STANDARD DEVIATIONS ABOVE NORMAL TONIGHT.

THE ATMOSPHERE OVER THE CENTRAL PLAINS WILL BE PRIMED FOR
POTENTIALLY HEAVY RAINFALL...GIVEN A DEEP WARM CLOUD LAYER ABOVE 10K
FEET...SKINNY CAPE PROFILE...AND AMPLE DEEP MOISTURE. THE MAIN
FORECAST CHALLENGE FOR TONIGHT WILL BE PINPOINTING WHERE THE
HEAVIEST RAINFALL WILL OCCUR. RIGHT NOW EXPECTING THE FOCUS TO BE
ALONG AND NORTH OF THE JUXTAPOSITION OF THE H85 FRONT AND NOSE OF
NOCTURNAL LLJ. THIS WOULD PLACE THE HEAVIER RAINFALL JUST A LITTLE
FURTHER NORTH THAN MONDAY NIGHT...BUT STILL GENERALLY SOUTH AND EAST
OF AN IMPERIAL TO O`NEILL LINE...WITH THE AXIS OF HEAVY RAIN
SHIFTING FROM WEST TO EAST ACROSS THE STATE AS THE LLJ VEERS
OVERNIGHT. QPF GRIDS REFLECT THIS TREND WITH A 1"+ SWATH FROM
SOUTHWEST INTO CENTRAL NEBRASKA BETWEEN 06Z AND 18Z WEDNESDAY.
LOCALIZED HEAVIER AMOUNTS ARE LIKELY.

LIKELY POPS FOR MUCH OF THE DAY WEDNESDAY WITH MOIST LOW LEVEL FLOW
BECOMING EASTERLY AND UPSLOPE. OVERALL COVERAGE MAY TEMPORARILY
DECREASE DUE TO SUBSIDENCE IN THE WAKE OF THE DEPARTING SHORTWAVE
TROUGH FROM TUESDAY NIGHT. HOWEVER SYNOPTIC SCALE LIFT SHOULD BECOME
PREVALENT AGAIN BY MID TO LATE AFTERNOON AS THE WESTERN CONUS TROUGH
MOVES OVER THE COLORADO ROCKIES. FOCUS FOR HIGHER QPF BECOMES MORE
DIFFICULT TO DISCERN AS THE MODELS ARE NOT IN BEST AGREEMENT.
CURRENT TREND IS FOR THE AXIS OF HEAVIER RAIN TO SHIFT NORTH ALONG A
MID-LEVEL FGEN BAND INTO NORTHERN AND NORTHWEST NEBRASKA BY LATE IN
THE DAY.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 253 PM CDT TUE AUG 26 2014

MID AND LONG TERM MODELS IN FAIR AGREEMENT. WIDESPREAD MODERATE TO
HEAVY RAIN WAS RATHER ISOLATED LAST NIGHT. MODELS HAVE BEEN HAVING
PROBLEMS WITH PRECIPITATION AMOUNTS. WILL GENERALLY FOLLOW HPC
QPF. MONSOONAL MOISTURE WILL CONTINUE TO STREAM ACROSS FORECAST
AREA THROUGH THURSDAY AND THEN THE GULF IS TAPPED. THE UPPER LOW
WILL SLOWLY MEANDER EAST THROUGH MID WEEK WITH THE MOISTURE
FINALLY MOVING EAST OF THE FORECAST ARE BY FRIDAY. COOLER
TEMPERATURES WITH UPPER LOW PRODUCING CLOUD COVER OVER WESTERN
NEBRASKA. HIGHS IN THE 70S TO AROUND 80 WEDNESDAY THROUGH FRIDAY.
LOWS IN THE UPPER 50S AND LOW 60S. BEST DYNAMICS IN MID TERM WILL
FALL AROUND WEDNESDAY NIGHT INTO THURSDAY MORNING. HAVE TRIMMED
POPS BACK SOME TUESDAY NIGHT AND WEDNESDAY...ESPECIALLY TO THE
NORTHWEST. BOUNDARY ALONG KANSAS BORDER WEDNESDAY NIGHT WITH
DEEPENING SURFACE LOW AND STRONGER MID LEVEL WAVE MOVING OUT OF
TROUGH TO THE WEST HAVE ADDED MODERATE RAIN TO THE
GRIDS...GENERALLY EAST OF HIGHWAY 83 AS 850MB JET OF 35KTS +
DEVELOPS IN THE OVER NIGHT HOURS. STORMS CONTINUING THROUGH THE
DAY ON THURSDAY BUT DECREASING IN INTENSITY AND AREAL COVERAGE.
PRECIPITATION MOVING EAST THROUGH THE DAY ON FRIDAY AND ENDING
ACROSS THE FORECAST AREA FRIDAY EVENING. CHANCES OF PRECIPITATION
IN THE FORECAST THROUGH THE WEEKEND INTO THE FIRST OF NEXT WEEK AS
AN UPPER TROUGH CROSSES THE NORTHERN PLAINS. BEST CHANCES OF
PRECIPITATION MONDAY NIGHT AS COOL FRONT PUSHED SOUTH THROUGH THE
FORECAST AREA. GULF IS CLOSED OFF SO SYSTEM WILL HAVE TO WORK WITH
PACIFIC MOISTURE. HIGHS IN THE 80S SATURDAY AND SUNDAY AND FALLING
BACK INTO THE 70S THE FIRST OF THE WORK WEEK AS COOL FRONT MOVES
SOUTH.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 645 PM CDT TUE AUG 26 2014

THERE IS CONSIDERABLE VARIABILITY AMONG THE SHORT RANGE FORECAST
OUTPUT...PRIMARILY IN THE TIMING OF THE PRECIPITATION TONIGHT. A
CONSENSUS WOULD PUT THE LOCATION ALONG AND SOUTH OF A BBW-OGA LINE.
TIMING FOR THE RAIN REACHING LBF RANGES FROM 02Z TO 09Z. UNTIL
THINGS BEGIN DEVELOPING AND BECOME MORE PREDICTABLE...WE WILL PUT
THE ONSET TIME FOR BBW-LBF-OGA ABOUT 06Z AND ADJUST AS NEEDED. IT IS
UNLIKELY THAT THE RAIN WILL REACH AS FAR NORTH AS ONL-TIF-MHN-AIA.
THERE IS ENOUGH INSTABILITY THAT THUNDERSTORMS WILL BE THE TYPE...
AT LEAST INITIALLY WITH PERIODS OF HEAVY RAIN LIKELY RESTRICTING
VISIBILITY TO LESS THAN 3SM AND POSSIBLY LESS THAN 1/2SM. THE RAIN
WILL PROBABLY CONTINUE TO 15Z OR LATER WITH EMBEDDED THUNDERSTORMS
POSSIBLE.

OTHERWISE...THERE IS POTENTIAL FOR CEILING AT OR BELOW 1000 FEET AGL
IN NORTHERN NEBRASKA BY EARLY WEDNESDAY.

&&

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

$$

SYNOPSIS...POWER
SHORT TERM...MARTIN
LONG TERM...POWER
AVIATION...SPRINGER






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