Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 200824
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
324 AM CDT SAT SEP 20 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 323 AM CDT SAT SEP 20 2014

TODAY AND TONIGHT...A VERY WEAK DISTURBANCE ACROSS SRN SD THIS
MORNING IS EXPECTED TO PASS THROUGH NCNTL NEB 12Z-15Z PRODUCING
SPRINKLES FOR THE MOST PART. THE HIGH CEILINGS SHOWN BY THE SFC OBS
SUPPORT THIS BUT PHILLIP SD PICKED UP 0.05 INCHES OF RAIN AT 06Z-07Z.
THE RAP13 MODEL APPEARS TOO BULLISH SHOWING WIDESPREAD QPF ACROSS
THE FCST AREA VS THE SCATTERED TO BROKEN CLOUD COVER SHOWN IN THE
MODEL.

THE TEMPERATURE FORECAST TODAY FOLLOWS THE WARM SIDE OF A MULTIMODEL
ENSEMBLE FOR HIGHS 80 TO 85 WHICH IS CLOSE TO THE NAM AND ECM
GUIDANCE. THE MAV GUIDANCE WAS A FEW DEGREES WARMER BUT THE MODEL
CONSENSUS SHOWS COOLING AT 700 MB WHICH WOULD MORE LIKELY SUPPORT 80
TO 85 FOR HIGHS. THE WEAK AREA OF HIGH PRESSURE ACROSS ERN WY BUILDS
IN TODAY FOLLOWED BY A STRONGER PUSH OF PACIFIC HIGH PRESSURE LATE
THIS AFTN ACROSS THE NORTH AND ELSEWHERE TONIGHT. THIS HIGH IS
CURRENTLY ACROSS BRITISH COLUMBIA AND WILL BE PULLED INTO THE FCST
AREA AS A DISTURBANCE ACROSS SRN SASKATCHEWAN TRACKS THROUGH THE NRN
PLAINS AND UPPER MIDWEST.

THE STRONG PACIFIC HIGH BUILDS INTO THE NORTHWEST TONIGHT FORCING
LOWS INTO THE UPPER 30S TO LOWER 40S BY MORNING. THE 00Z ECM
GUIDANCE SHOWS A LOW OF 38 AT PINE RIDGE WHICH IS 6 DEGREES COLDER
THAN THE 00Z ECM MODEL RUN ONE DAY AGO. THE MODEL CONSENSUS SHOWS
1025 MB HIGH CENTERED OVER NWRN NEB BY 12Z SUNDAY WHICH WOULD
SUPPORT THE ECM FORECAST. MID LEVEL CLOUDS AND MIXING CONTINUE
FARTHER SOUTH FOR LOWS IN THE UPPER 40S TO LOWER 50S.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 323 AM CDT SAT SEP 20 2014

SUNDAY THROUGH TUESDAY...CUTOFF UPPER LOW OFF THE COAST OF SO CAL
WILL DRIFT NEWD THANKS TO BUILDING UPPER HEIGHTS ACROSS WRN CANADA
BEHIND EXITING NRN PLAINS UPPER PV ANOMALY. AS THE LOW MOVES INTO
THE CENTRAL ROCKIES WEAK NEARLY ZONAL FLOW DEVELOPS ON THE SRN END
OF THE UPPER LOW...WHICH WILL SERVE TO DEVELOP A LEE TROF ACROSS ERN
CO/ERN WY. AS SFC HIGH SLIDES/REFORMS ACROSS THE MID MS VALLEY
RETURN FLOW WILL DEVELOP OVER THE HIGH PLAINS REGION AND WILL
TRANSPORT ANOMALOUS MOISTURE INTO THE HIGH PLAINS REGION...POSSIBLY
AS MUCH AS 2 SD ABOVE AVE FOR THIS TIME OF YEAR AS DEPICTED BY
19/12Z NAEFS. HOWEVER...CAPE VALUES ARE PROGGED BY THE MODELS TO BE
MEAGER AT BEST AND DISTRIBUTED IN A NARROW REGION VERTICALLY. AS
SUCH WILL MAINLY WORD PRECIP AS SHOWERS WITH ISOLATED THUNDER. TEMPS
WILL BE HIGHLY DEPENDENT ON CLOUD COVER ASSOCIATED WITH THE PRECIP
AND LIKELY WILL BE HELD DOWN ESPECIALLY ON MONDAY IN THE SANDHILLS.

WEDNESDAY THROUGH FRIDAY...LOW CONFIDENCE IN ACTUAL DETAILS OF THE
FCST AS MEANDERING UPPER LOW IS HANDLED DIFFERENTLY BY THE MID RANGE
MODELS. MODELS KEEP IT IN THE NRN PLAINS REGION BUT ECMWF HAS IT IN
A WEAKENED STATE...WHILE THE GEM DROPS AN UPPER PV ANOMALY AND
ASSOCIATED STRONG HEIGHT FALLS INTO THE AFOREMENTIONED TROUGH WHICH
CAUSES IT TO SLIDE BACK TO THE SW. GFS IS SOMEWHAT SIMILAR...BUT HAS
MUCH WEAKER HEIGHT FALLS ASSOCIATED WITH THE PV ANOMALY. AS ALL THIS
DEVELOPS...MORE SIGNIFICANT LONG WAVE TROUGH MOVES ONSHORE ACROSS THE
WRN STATES BY THE END OF THE WEEK. WEAK UPPER RIDGE BUILDS IN
BETWEEN THE TWO SYSTEMS MENTIONED...AND WOULD GENERALLY EXPECT BEST
FORCING TO OCCUR ON THE ERN SIDE OF THE MEANERING UPPER LOW WHICH
SUGGESTS BETTER CHANCES FOR PRECIPITATION ACROSS THE ERN PORTION OF
THE STATE. AGAIN HOWEVER...IT DEPENDS ON WHERE THE LOW ENDS UP.
STRONG...MOIST FLOW CONTINUES HOWEVER...WHICH KEEPS PW VALUES AROUND
THE 1 INCH RANGE OR SLIGHTLY BETTER THROUGH THE END OF THE WEEK. THE
GOOD LOW LEVEL MOISTURE WILL LEAD TO SOME INSTABILITY WHICH MAY BE
REALIZED IF SUNSHINE PREVAILS. END RESULT IS PRECIPITATION CHANCES
CONTINUE FOR MUCH OF THE WEEK. LOCATIONS MAY BE DETERMINED BY
RESULTANT BOUNDARIES FROM PREVIOUS CONVECTION IN WEAK FLOW.

&&

.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.
&&

$$

SHORT TERM...CDC
LONG TERM...JWS
AVIATION...CDC






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