Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 200523 AAA
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1223 AM CDT SAT SEP 20 2014

.SYNOPSIS...
ISSUED AT 250 PM CDT FRI SEP 19 2014

AT H5 CUTOFF LOW JUST OFF THE CENTRAL CALIFORNIA COAST WHICH WILL
BE THE WEATHER MAKER FOR THE NORTHERN AND CENTRAL PLAINS FOR MUCH
OF THE FOLLOWING WORK WEEK. REMNANTS OF ODILLE IN CENTRAL TEXAS.
HURRICANE POLO SEEN IN IR JUST WEST OF PUERTO VALLARTA. RIDGING
INTO THE PACIFIC NORTHWEST AND WEAK TROUGH FROM HUDSON BAY LOW
INTO THE NORTHERN PLAINS.

&&

.UPDATE...
ISSUED AT 1038 PM CDT FRI SEP 19 2014

ISOLATED THUNDERSTORMS HAVE DEVELOPED AHEAD OF THE COLD FRONT IN
THE NEBRASKA PANHANDLE AND WESTERN SANDHILLS. ALSO...ISOLATED
THUNDERSTORMS DEVELOPED IN THE EASTERN SANDHILLS ALONG THE SURFACE
TROUGH. SURFACE LAPS AND GOES DERIVED PRODUCT IMAGERY SHOW FAIRLY
UNSTABLE CONDITIONS AND DECENT MOISTURE OVER NORTH CENTRAL
NEBRASKA IN THE AREA BOUNDED BY ONEILL...BROKEN BOW AND
AINSWORTH...SO WE WOULD EXPECT THUNDERSTORMS TO INCREASE IN NORTH
CENTRAL NEBRASKA. THE STORMS IN THE WESTERN SANDHILLS HAVE THE
SURFACE FRONT AND A POTENTIAL VORTICITY ANOMALY TO AID THEIR
DEVELOPMENT.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 250 PM CDT FRI SEP 19 2014

TONIGHT AND TOMORROW.  THE FORECAST CHALLENGE IN THE
NEAR TERM REVOLVES AROUND PRECIPITATION CHANCES THIS EVENING AND
OVERNIGHT.  FRONTAL BOUNDARY WILL CONTINUE TO DROP TO THE SOUTHEAST
THIS EVENING...FOCUSING STORM DEVELOPMENT IN ADVANCE OF/ALONG IT/S
PATH.  THE LATEST OUTPUT FROM THE CONVECTIVE ALLOWING MODELS...BUFR
SOUNDINGS AND THE SPC MESO ANALYSIS PAGE INDICATE A SUBSTANTIAL
CAPPING INVERSION PRESENT...BUT THIS CAP IS SHOWN TO ERODE
SUFFICIENTLY FOR ISOLATED CONVECTION AS FORCING INCREASES WITH THE
SURFACE FRONT.  ATTM...THE MOST LIKELY AREA FOR CONVECTION WILL BE
ACROSS OUR NORTH CENTRAL NEBRASKA ZONES AND THE CENTRAL
SANDHILLS...WHERE THE MODELS ARE INDICATING SUFFICIENT MOISTURE
CONVERGENCE AND BULK SHEAR FOR STORMS...BUT AT THAT...CURRENT
FORECAST WOULD ONLY SUGGEST ISOLATED STORMS AT BEST.  DCAPE VALUES
ARE INDICATIVE OF A STRONG TO LOW END SEVERE WIND THREAT THIS
EVENING AS SFC TD/T SPREADS APPROACH 40F ACROSS THE HEART OF THE
SANDHILLS...BUT OTHERWISE ANY STORM SHOULD REMAIN WELL-BEHAVED.  THE
ACTIVITY IS SHOWN TO CONTINUE INTO THE OVERNIGHT WITH THE
STRENGTHENING OF A LLJ WITH THE ACTIVITY TO THE SOUTHEAST OF THE
FORECAST AREA BEFORE DAWN.

OVERNIGHT LOWS ARE A PRODUCT OF BC GUIDANCE WITH THE CURRENT
FORECAST.  CLEARING AND LIGHT WINDS ARE ANTICIPATED BEHIND THE PASSING
FRONT...LOWS SHOULD BE ABLE TO EASILY UNDERCUT GUIDANCE BY SEVERAL
DEGREES ESPECIALLY IN DRAINAGE PRONE AREAS SUCH AS THE PLATTE RIVER
SYSTEM.  WE CURRENTLY HAVE A RANGE OF LOWS FROM THE LOWER 50S ACROSS
OUR FAR NORTHWEST...TO NEAR 60S OVER THE FAR EAST AND SOUTHEAST.
MID 50S  SEEM FINE FOR KLBF AND KVTN.

WITH POST FRONTAL CONDITIONS PRESENT SATURDAY AND H85 T/S IN SOME
CASES 5C OR COOLER THAN TODAY...HIGHS WILL COOL SEVERAL
DEGREES...CURRENT FORECAST INDICATES A 7-10 DEGREE DROP FROM
TODAY...WHICH SUGGESTS HIGHS IN THE LOWER 80S FOR MOST PLACES.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 250 PM CDT FRI SEP 19 2014

MAIN FORECAST CHALLENGE WILL BE PRECIPITATION ASSOCIATED WITH
CUTOFF LOW TO THE WEST THAT WILL MOVE INTO THE NORTHERN PLAINS
THIS COMING WORK WEEK. COOL FRONT THAT MOVES ACROSS WESTERN
NEBRASKA SATURDAY WILL BE WELL INTO NORTHERN KANSAS NORTHEAST
COLORADO SATURDAY NIGHT. STRONG SUBSIDENCE BEHIND THE FRONT AS
COOLER AIR ASSOCIATED WITH THE SURFACE HIGH MOVES SOUTHEAST INTO
WESTERN NEBRASKA. LOWS IN THE 50S WITH SOME 40S OVER NORTHWEST
BACK TOWARDS COOLER AIR. CLEAR SKIES AND HIGHS IN THE 70S WITH
LIGHT WINDS AS SURFACE HIGH IS ANCHORED OVER NEBRASKA. FRONT
BEGINS TO LIFT NORTH SUNDAY NIGHT AS CUTOFF LOW TO THE WEST MOVES
INTO THE GREAT BASIN. FRONT RANGE OF THE ROCKIES FROM NEW MEXICO
TO WYOMING WILL SEE SCATTERED THUNDERSTORMS. SURFACE HIGH TO THE
EAST WILL BRING STRONG STEADY SOUTH FLOW WITH GOOD MOISTURE
TRANSPORT INTO THE FRONT RANGE AND THE NORTHERN PLAINS THURSDAY AS
THE CUTOFF UPPER LOW MEANDERS OVER THE DAKOTAS. HIGHS IN THE 70S
NORMAL FOR THE SEASON AND LOWS IN THE 50S. ON THE BACKSIDE OF THE
UPPER LOW AS RIDGE BUILDS EAST TEMPERATURES RISING TO NEAR 80 AND
DRY. QPF AMOUNTS MAY HAVE TO BE BOOSTED.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1222 AM CDT SAT SEP 20 2014

CONVECTION HAS TAKEN ITS TIME DEVELOPING IN THE LBF CWA THIS EVENING
BUT HAS NOW INITIATED IN ISOLD FASHION AS COLD FRONT BEGINNS TO
OVERTAKE SFC TROUGH AND HENCE DEEPER LIFT IN A REGION OF DECENT MID
LEVEL LASPE RATES. ISOLD TSRA IN WRN MCPHERSON COUNTY LOOKS TO TRACK
CLOSE TO KLBF IN THE NEXT COUPLE HOURS AND HAVE INCLUDED THIS IN
LATEST ISSUANCE. SHORT RANGE AND CONVECTION ALLOWING MODELS HAVING A HARD
TIME CAPTURING ACTUAL DEVELOPMENTS THIS EVENING...HRRR HAS WANTED TO
DEVELOP CONVECTION ALONG THE ENTIRE COLD FRONT EARLIER IN THE
EVENING...AND IR SAT PICS INDICATE CLOUD TOPS COOLING ALONG THE
TROUGH AXIS FINALLY. BELIEVE THE LARGER SCALE DEVELOPMENT WILL OCCUR
SOUTH AND EAST OF KLBF TAF SITE AND THERFORE ONLY INCLUDED TSRA
MENTION THROUGH 08Z. CONVECTION WILL DEVELOP WELL SOUTH OF KVTN.
COLD FRONT PUSHES THROUGH THE FCST AREA OVERNIGHT WITH THE HELP OF
CONVECTIVE OUTFLOW SO ONCE CLOUD DEBRIS CLEARS MAINLY SKC WILL
PREVAIL. WINDS WILL PICK ACROSS THE AREA AFTER 17-18Z SAT.

&&

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

$$

UPDATE...SPRINGER
SYNOPSIS...POWER
SHORT TERM...JACOBS
LONG TERM...POWER
AVIATION...CDC





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