Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 281155
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
655 AM CDT SUN SEP 28 2014

.SYNOPSIS...
ISSUED AT 333 AM CDT SUN SEP 28 2014

UPPER LEVEL TROUGH ACROSS THE WESTERN CONUS...WEST OF THE
ROCKIES...WITH A BROAD RIDGE ACROSS THE REST OF THE CONUS. A CUT-OFF
CLOSED LOW IS DRIFTING ACROSS NE NEB/SE S DAKOTA/SW MIN/NW IA. LOW
LEVEL JET HAS KICK UP WITH THE NOSE VEERING INTO NE NEB. THE
COMBINATION OF THE JET AND THE UPPER LEVEL LOW CREATING ENOUGH LIFT
FOR SOME SHOWERS TO DEVELOP...SO FAR ISOLATED. MOSTLY CLEAR SKIES
ACROSS THE HEART OF THE CWA WITH A FEW CLOUDS SPREADING ACROSS THE
PANHANDLE...WHILE SOME CLOUDS HAVE DEVELOPED ACROSS N CENTRAL...NEAR
THE SHOWERS. TEMPS HAVE FALLEN INTO THE LOWER 60S AS OF 3 PM CDT.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 333 AM CDT SUN SEP 28 2014

EARLY THIS MORNING EYES WILL FOCUS ON SHOWERS ACROSS NORTHEAST
NEBRASKA. SO FAR ACTIVITY HAS REMAINED EAST OF THE CWA...WITH THE
MAJORITY OF THE NEAR TERM MODELS CONTINUING THE ACTIVITY JUST TO THE
EAST. HAVE INCLUDED SOME SPRINKLES TO ACCOUNT FOR ANY SHOWERS THAT
DO MAKE IT THIS FAR WEST. MODELS ARE TAKING THE UPPER LEVEL LOW AND
DRIFTING IT TO THE NE...AND MORNING MIXING WILL DIMINISH THE
NOCTURNAL JET SO EXPECT THE ACTIVITY TO BE SHORT LIVED IN THE CWA.
MEANWHILE ACROSS THE RIVER VALLEY...SOUTHEAST WINDS HAVE INCREASE LL
MOISTURE. A BRIEF HOUR OR TWO OF PATCHY MORNING FOG CAN NOT BE RULED
OUT...HOWEVER THE SHORT DURATION AND LOCALIZED NATURE WILL NOT
MENTION IN THE GRIDS/FORECAST.

THIS AFTERNOON WITH MOST AREAS SEEING GOOD SUN...TEMPS ONCE AGAIN
GET ABOVE 80. THE ONLY COOL SPOT WILL BE FAR NW ZONES...MAINLY NRN
SHERIDAN COUNTY...WHERE INCREASING CLOUDS FROM THE WESTERN STORM
SYSTEM....WILL HELP TO HOLD HIGHS IN THE UPPER 70S.

TONIGHT THE SW SYSTEM WILL PUSH TOWARDS THE CENTRAL ROCKIES. INITIAL
WAVE AHEAD OF THE MAIN LOW WILL EJECT ACROSS THE ROCKIES AND ONTO
THE HIGH PLAINS. THIS WILL BRING A CHANCE OF SHOWERS...MAYBE
SOME THUNDER...TO WESTERN NEB. DRY AIR WILL HAVE TO BE OVERCOME
INITIALLY AND DO NOT EXPECT ANYTHING TO REACH THE GROUND UNTIL AFTER
MIDNIGHT.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 320 AM CDT SUN SEP 28 2014

MONDAY - TUESDAY NIGHT

DIFLUENT FLOW ALOFT WILL OVERSPREAD THE CWA ON MONDAY IN ADVANCE OF
A STRONG PV ANOMALY/UPPER LEVEL JUST STREAK DIGGING TROUGH THE
SOUTHERN ROCKIES. RESPONSE AT THE SURFACE WILL BE A DEEPENING LEE
SIDE SFC LOW IN NORTHEAST COLORADO AND A TIGHTENING PRESSURE
GRADIENT..SO A BREEZY DAY IS EXPECTED AS SOUTHEASTERLY FLOW RAMPS UP
ACROSS THE CENTRAL PLAINS. WEAK THETA-E ADVECTION IN THE LOWER
TROPOSPHERE AND BROAD SCALE ASCENT ASSOCIATED WITH MID-LEVEL HEIGHT
FALLS WILL FAVOR AN INCREASE IN CLOUD COVER AND A MENTION OF SHOWERS
AND THUNDERSTORMS IN THE GRIDS. FOCUS FOR CONVECTION SHOULD REMAIN
IN A ZONE OF LOW LEVEL MOISTURE CONVERGENCE ALONG A NORTHWARD
LIFTING WARM FRONT FROM THE PANHANDLE INTO THE NORTHERN SANDHILLS
LATE MONDAY MORNING AND AFTERNOON.

ALL MODEL SOLNS NOW SHOW THE PROGRESSION OF AN OPEN WAVE QUICKLY
TRANSITIONING TO A NEGATIVELY TILTED CLOSED H5 LOW AS A STRONG PV
MAX EJECTS NORTHEASTWARD OUT OF THE CENTRAL ROCKIES MONDAY NIGHT.
GFS REMAINS THE FASTEST AND DEEPEST MODEL...HOWEVER THE TREND OF THE
OTHER SYNOPTIC MODELS HAS BEEN TOWARD THE GFS. REGARDLESS OF THE
MODEL CHOICE...QUICK SFC LOW INTENSIFICATION WILL OCCUR OVER
NORTHEAST COLORADO AND THE NEBRASKA PANHANDLE MONDAY EVENING IN THE
DIVERGENT LEFT EXIT REGION OF A 60+ KT H5 JET STREAK. WIDESPREAD
SHOWERS AND THUNDERSTORMS WILL DEVELOP IN A ZONE OF STRONG ASCENT
EXTENDING FROM EASTERN CO/WESTERN KS NORTHWARD INTO THE DAKOTAS. NOT
TOO CONCERNED ABOUT THE SEVERE WEATHER POTENTIAL AT THIS POINT.
LAPSE RATES AND DEEP LOW LEVEL MOISTURE ARE BOTH LACKING IN THIS
SCENARIO. HOWEVER...DEEP LAYER SHEAR OF 30 KTS MAY BE ENOUGH TO
SUPPORT A SHORT LIVED STRONG TO SEVERE STORM DURING THE EVENING
HOURS. AS FOR POPS...HAVE BUMPED UP TO CATEGORICAL AFTER 00Z TUESDAY
WEST OF HWY 61 WHERE HIGH CONFIDENCE EXISTS IN WIDESPREAD SHOWER AND
THUNDERSTORM DEVELOPMENT. LOCALIZED HEAVY RAINFALL WILL BE POSSIBLE
AS PWATS INCREASE TO 2 STANDARD DEVIATIONS ABOVE CLIMO...AS WELL AS
THE POTENTIAL FOR MULTIPLE ROUNDS OF PRECIPITATION. SHOWER AND
THUNDERSTORM CHANCES WILL OVERSPREAD THE REST OF THE FORECAST AREA
ALONG AND AHEAD OF A PACIFIC COLD FRONT THROUGH THE REMAINDER OF THE
EVENING AND OVERNIGHT HOURS.

MODELS ARE BECOMING MORE AGGRESSIVE WITH THE PUSH OF DRY AIR FROM
THE SOUTHWEST ON TUESDAY MORNING. TRENDED DOWN POPS FROM SOUTH TO
NORTH AFTER 12Z TUESDAY...BUT CONTINUE MENTION THROUGH THE DAY
ACROSS THE NORTHERN HALF OF THE CWA. STEEP LAPSE RATES IN
ASSOCIATION WITH THE UPPER LEVEL LOW/COLD POOL SHOULD BE ENOUGH TO
PRODUCE ADDITIONAL SHOWER AND THUNDERSTORM ACTIVITY...MAINLY DURING
THE AFTERNOON HOURS.

GUSTY WINDS MAY BE A CONCERN ON TUESDAY ACROSS THE NORTHERN PART OF
THE CWA AS WELL. 1.5 PVU SFC DROPS BELOW 400MB ACROSS NORTHERN
NEBRASKA IN CONCERT WITH A TIGHT PRESSURE GRADIENT ASSOCIATED WITH
THE EASTWARD ADVANCING FRONT. SCATTERED AFTERNOON SHOWER ACTIVITY
COULD ALSO HELP MIX DOWN STRONGER WIND GUSTS FROM THE MID LEVELS.
LATEST MAV GUIDANCE AT CDR AND VTN ADVERTISES SUSTAINED WINDS OF 25
TO 30 KTS DURING THE AFTERNOON HOURS IN THE WAKE OF THE FRONT. THE
NAM IS ON THE LOWER END OF THE GUIDANCE ENVELOPE DESPITE A FAVORABLE
SYNOPTIC SETUP FOR WINDY CONDITIONS..SO THE GRIDS WERE TRENDED
TOWARD A EC/MAV GUIDANCE BLEND FOR NOW. FURTHER ADJUSTMENTS WILL BE
NEEDED AS CONFIDENCE INCREASES.

WEDNESDAY - SATURDAY

LONGWAVE TROUGH WITH SEVERAL EMBEDDED SHORTWAVES SLOWLY MOVES EAST
OVER THE CENTRAL CONUS THROUGH THE SECOND HALF OF THE WEEK...SENDING
MULTIPLE COLD FRONTS AND SHOWER CHANCES THROUGH THE CWA. LATEST EC
HAS TRENDED SLIGHTLY WARMER TOWARD THE END OF THE WEEK...HOWEVER THE
MORE CONSISTENT RUN TO RUN TRENDS OF BOTH THE GFS AND EC HAS CALLED
FOR HIGHS IN THE MID 50S TO THE MID 60S BY FRIDAY...THEN WARMING
BACK UP FOR THE WEEKEND. FROST/FREEZE POTENTIAL WILL HAVE TO BE
MONITORED FOR THE END OF THE WEEK AS A SFC HIGH SETTLES INTO THE
HIGH PLAINS UNDERNEATH STRONG SUBSIDENCE ALOFT. ALLBLENDS CURRENTLY
GIVES LOWS IN THE MID TO UPPER 30S FRIDAY NIGHT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 653 AM CDT SUN SEP 28 2014

UPPER LEVEL CLOSED LOW DRIFTING TOWARDS SRN MINNESOTA HAS SPARKED
A FEW SHOWERS EAST OF KONL...AND EXPECT THE ACTIVITY TO REMAIN TO
THE EAST. MEANWHILE SOUTHEASTERLY WINDS HAVE INCREASED BL MOISTURE
TO THE POINT OF DEVELOPING SOME PATCHY FOG BRIEFLY THIS
MORNING...MAINLY IN THE LOW LYING AND RIVER VALLEY. FORECAST IS
CONSERVATIVE WITH A TEMPO OF 4SM BR FOR KLBF.

AFTERNOON INTO TONIGHT EXPECT VFR CONDITIONS. LOW PRESSURE SYSTEM
WILL BEGIN TO CROSS THE CENTRAL ROCKIES OVERNIGHT WITH A CHANCE
FOR SHOWERS SPREADING EAST ACROSS THE AREA LATE TONIGHT INTO
TOMORROW AHEAD OF THE MAIN LOW.

&&

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

&&

$$

SYNOPSIS...MASEK
SHORT TERM...MASEK
LONG TERM...MARTIN
AVIATION...MASEK





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