Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 221124 AAA
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
624 AM CDT MON SEP 22 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 401 AM CDT MON SEP 22 2014

TODAY AND TONIGHT...A DEEPENING SFC TROF WILL ADVANCE SOUTHEAST INTO
WRN NEB TODAY AND TONIGHT. SFC WINDS ARE EXPECTED TO INCREASE TO 15
TO 25 MPH WITH GUSTS TO 35 MPH ACROSS NWRN ZONES. WINDS RELAX A BIT
TONIGHT BUT REMAIN STRONG OFF THE SFC. THE LATEST MODEL CONSENSUS
SUGGESTS CLUSTERS OF SHOWERS AND THUNDERSTORMS SHOULD BE UNDERWAY BY
21Z THIS AFTN AS AN UPPER LOW ACROSS IDAHO ADVANCES EAST TOWARD AND
INTO WRN SD TODAY AND TONIGHT.

THE SEVERE WEATHER POTENTIAL LOOKS LOW TODAY AND TONIGHT AS THE
BETTER INSTABILITY REMAINS OVER ERN COLO. THE MODEL CONSENSUS
SUGGESTS 1/4 TO 1/2 INCH OF RAIN TODAY AND TONIGHT ACROSS THE FCST
AREA BUT THERE IS CERTAINLY THE POTENTIAL FOR MORE GIVEN PWS
INCREASING TO 1.33 INCHES WHICH IS 200 PERCENT OF NORMAL. THE NAM
INDICATED HIGHER VALUES.

THE ONGOING CLOUD COVER ACROSS WRN NEB IS EXPECTED TO INCREASE AND
EXPAND EAST TODAY. SOME CLEARING MAY DEVELOP IN THE WEST LATE
TONIGHT. GIVEN THE HIGH MOISTURE AVAILABLE POPS ARE LIKELY SOUTH AND
EAST TONIGHT.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 401 AM CDT MON SEP 22 2014

THE PRIMARY FORECAST CONCERN WILL BE THUNDERSTORM CHANCES
TUESDAY...THEN WITH TEMPERATURES AND RAIN CHANCES WITH A
RETROGRADING UPPER LEVEL SYSTEM THROUGHOUT THIS WEEK.

TUESDAY...THE UPPER LEVEL LOW WILL BE PUSHING OUT OF THE ROCKY
MOUNTAINS AND INTO THE NORTHERN PLAINS. THE MODELS ARE IN GOOD
AGREEMENT WITH THE UPPER LOW CENTER MOVING ACROSS SOUTH DAKOTA
THROUGH THE DAY...WITH VARIOUS WEAK SHORTWAVE IMPULSES MOVING AROUND
THE SYSTEM.

SHOWERS AND POTENTIALLY A FEW ISOLATED THUNDERSTORMS SHOULD BE
EXITING THE FORECAST AREA TO THE EAST DURING THE MORNING HOURS. BY
AFTERNOON...A SURFACE TROUGH WILL MAKE ITS WAY ACROSS THE PANHANDLE
AND INTO WESTERN NEBRASKA. FORECAST SOUNDINGS SHOW LOCATIONS
GENERALLY WEST OF HIGHWAY 83 WILL MIX OUT AND WITH STEEP LOW LEVEL
AND MID LEVEL LAPSE RATES...CAPE VALUES INCREASE TO 1000-2000 J/KG
BY LATE AFTERNOON AND WITH THE STRONG WARMING...SURFACE BASED
CONVECTION IS LIKELY. THERE IS SOME DISCREPANCIES BETWEEN MODELS IN
TERMS OF DEEP LAYER SHEAR...AS THE GFS IS MUCH STRONGER...SUGGESTING
IN EXCESS OF 40KTS...WHILE THE NAM IS 20 TO 30KTS. EVEN WITH THE
LOWER SHEAR...IT SHOULD BE SUFFICIENT FOR AT LEAST A FEW STRONGER
STORMS LATER TUESDAY AFTERNOON. AREAS TO THE EAST WILL SEE COOLER
HIGHS...IN THE UPPER 60S AND LOW 70S DUE TO THE PRECIPITATION
EARLIER IN THE DAY AND ARE LOOKING TO STAY VERY CAPPED. THESE AREAS
WILL STILL SEE STORMS MOVE IN DURING THE EVENING AND OVERNIGHT
HOURS...BUT THEY SHOULD BECOME ELEVATED QUICKLY AND WITH A LACK OF
INSTABILITY WOULD EXPECT THUNDER TO DECREASE...BUT THERE WILL BE AT
LEAST A WEAK LOW LEVEL JET THAT COULD CONTINUE TO FEED THE STORMS
THROUGH THE NIGHT AS THEY MOVE EAST.

AT 12Z WEDNESDAY MORNING...THE MODELS HAVE MOVED THE UPPER LOW
CENTER OVER SOUTHEAST SOUTH DAKOTA AND NORTHEAST NEBRASKA...AND WITH
THE UPWARD FORCING SHIFTING TO THE EAST...PRECIPITATION SHOULD BE
CLOSE TO...IF NOT COMPLETELY FINISHED LOCALLY. FAIRLY STRONG
SUBSIDENCE BUILDS IN ACROSS THE FORECAST AREA THROUGH THE DAY
WEDNESDAY BEHIND THE UPPER LEVEL SYSTEM LEADS TO A DRY FORECAST.
WARMER AIR WILL BE ADVECTING INTO THE AREA DURING THE DAY AND WITH
THE DRY AIR IN PLACE AND PLENTY OF SUNSHINE...STRONG WARMING IS
EXPECTED WITH HIGHS IN THE 80S FOR THE WESTERN TWO-THIRDS OF THE
FORECAST AREA. WITH THE UPPER LOW REMAINING OVER EASTERN
NEBRASKA...THE EASTERN PARTS OF THE FORECAST AREA MAY SEE SOME
RESIDUAL CLOUD COVER AND WITH COOLER TEMPERATURES ALOFT...WILL SEE
COOLER TEMPERATURES WITH HIGHS LOOKING TO BE IN THE MID TO UPPER 70S.

BEYOND WEDNESDAY THERE BEGINS TO BE SLIGHT DIVERGENCE IN THE MODEL
SOLUTIONS IN TERMS OF THE UPPER LEVEL PATTERN. WHAT IS IN GOOD
AGREEMENT IS A DEEP LONGWAVE TROUGH MOVING INTO THE WESTERN
CONUS...WITH RIDGING BUILDING AHEAD OF IT INTO THE NORTHERN
PLAINS. WHAT IS STARTING TO GET PROBLEMATIC IS THE CURRENT SYSTEM
GETS STUCK UNDER THE LARGE RIDGE WHICH SPANS INTO THE EASTERN PART
OF THE COUNTRY AND STARTS TO RETROGRADE. THE DISCREPANCIES LIE
WITH HOW FAR WEST IT WILL MAKE IT. THE RIDGE TO THE WEST WILL KEEP
SOUTHERLY FLOW IN THE LOWER LEVELS...KEEPING LOW LEVEL MOISTURE
ACROSS THE FORECAST AREA WITH DEWPOINTS REMAINING IN THE UPPER 50S
AND 60S...WHILE WEAK AND MINI SHORTWAVES MAY MOVE ACROSS THE FORECAST
AREA AT TIMES LATER IN THE WEEK. THESE SMALL IMPULSES OF ENERGY
AREN/T LOOKING TO GENERATE ENOUGH LIFT AT THIS POINT TO PROVIDE A
NEED FOR RAIN IN THE FORECAST SO WILL KEEP A DRY FORECAST AT THIS
TIME. WHAT THIS WILL MEAN IS LIKELY COOLER TEMPERATURES FOR LATE
IN THE WEEK AS THE WARMER AIR WILL BE KEPT TO THE WEST AND NORTH
OF THE LOCAL AREA DUE TO THE INFLUENCE OF THE UPPER LEVEL SYSTEM.

THEN LOOKING INTO THE WEEKEND...OUT OF THE LONGWAVE TROUGH MOVING
ONTO THE WEST COAST...A LOW WILL CLOSE OFF AND SLOWLY MIGRATE
TOWARDS THE EAST. THERE IS DIFFERENCES WITH THE SPEED AS THE
OPERATIONAL GFS IS FASTER THAN THE ECMWF AS WELL AS THE GFS
ENSEMBLE MEAN. THE FASTER SOLUTION WOULD BRING CHANCES FOR SHOWERS
AND THUNDERSTORMS BY SUNDAY AFTERNOON...WHILE THE SLOWER WOULD
KEEP THINGS DRY INTO MONDAY. WILL BE KEEPING A CLOSE EYE ON THIS
SYSTEM AS TIME GETS CLOSER TO GET A BETTER HANDLE ON THE FORECAST
FOR THESE PERIODS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 624 AM CDT MON SEP 22 2014

AREAS OF SHOWERS AND SCATTERED THUNDERSTORMS ARE EXPECTED TO
DEVELOP ACROSS WRN NEB 18Z- 20Z AND MOVE EAST NORTHEAST THROUGH
NCNTL NEB LATE THIS AFTN AND TONIGHT. THIS ACTIVITY IS EXPECTED TO
EXITING THE FCST AREA TO THE EAST 06Z- 12Z TUESDAY MORNING. MVFR
CIGS MAY DEVELOP ALONG AND NEAR HIGHWAY 61 06Z-09Z TUESDAY MORNING
IN THE WAKE OF THE TSTMS.

&&

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

$$

SHORT TERM...CDC
LONG TERM...BROOKS
AVIATION...CDC






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