Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 300317 AAB
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1017 PM CDT MON SEP 29 2014

.SYNOPSIS...
ISSUED AT 335 PM CDT MON SEP 29 2014

AT 19Z...WATER VAPOR IMAGERY SHOWED A STRONG UPPER LEVEL SYSTEM
ACROSS THE WESTERN CONUS...WITH A VERY INTENSE PV ANOMALY ROUNDING
THE BASE OF THE TROUGH OVER EASTERN ARIZONA INTO NORTHWEST NEW
MEXICO. DOWNSTREAM FROM THE UPPER TROUGH...RIDGING WAS OBSERVED
ACROSS THE PLAINS...WHILE A POTENT SHORTWAVE TROUGH IN THE NORTHERN
STREAM MOVED THROUGH NORTHERN MINNESOTA AND WISCONSIN. AT THE
SURFACE LOW PRESSURE WAS OBSERVED OVER SOUTHWEST COLORADO WITH AN
INVERTED TROUGH EXTENDING TO THE NORTHEAST INTO SOUTHWEST NEBRASKA.
A WARM FRONT WAS ALSO OBSERVED FROM THE SOUTHERN NEBRASKA PANHANDLE
THROUGH AROUND KTIF AND KONL. NORTH OF THE WARM FRONT...CLOUDY
SKIES...FOG AND RAIN SHOWERS AND THUNDERSTORMS HAVE KEPT
TEMPERATURES RISES MINIMAL WITH HIGHS SO FAR IN THE 50S AND 60S.
SOUTH OF THE FRONT...AS THE BOUNDARY LAYER SAW STRONG MIXING TO NEAR
750MB...BREEZY SOUTHERLY WINDS WERE BEING MIXED TO THE
SURFACE...WITH TEMPERATURES RISING INTO THE LOW 80S.

A SECOND PORTION OF THE UPPER LEVEL LOW ACROSS THE WRN U.S. WILL
LIFT THROUGH WRN NEB TONIGHT SETTING OFF A SECOND ROUND OF HEAVY
THUNDERSTORMS AND SEVERE WEATHER. THIS UPPER LEVEL LOW WILL MOVE
THROUGH THE GREAT LAKES BAY LATER THIS WEEK AND BECOME THE BASIS
OF A DEEP HUDSON BAY LOW BY SATURDAY. THIS WILL SEND COLD AIR INTO
THE NORTHEAST U.S. WITH WARMER AIR ACROSS THE CNTL PLAINS. A
PORTION OF THIS COLD AIR WITH AFFECT WRN AND NCNTL NEB THURSDAY
AND FRIDAY BUT WARMER AIR RETURNS SATURDAY THROUGH MONDAY. A
STRONG COLD FRONT MOVES THROUGH WEDNESDAY AND WEDNESDAY NIGHT WITH
RAIN POSSIBLE SOUTH.

&&

.UPDATE...
ISSUED AT 1018 PM CDT MON SEP 29 2014

FORECAST UPDATE TO DROP TORNADO WATCH. REMAINDER OF FORECAST ON TRACK.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 335 PM CDT MON SEP 29 2014

THE SURFACE LOW OVER SOUTHEAST COLORADO WILL HEAD NORTHWARD OVER THE
NEXT SEVERAL HOURS AS THE STRONG PV ANOMALY OVER ARIZONA AND NEW
MEXICO LIFTS NORTHEAST INTO COLORADO. THE ENERGY FROM THIS SYSTEM
WILL BRING DEEP LARGE-SCALE LIFT ACROSS WESTERN NEBRASKA AND WITH
THE DYNAMICS IN PLACE...GOOD VORTICITY THROUGH THE LAYER AS WELL AS
IN THE LOW LEVELS ESPECIALLY IN THE VICINITY OF THE SURFACE LOW.
STORMS HAVE BEGUN TO DEVELOP ALONG THE SURFACE TROUGH FROM CENTRAL
COLORADO INTO SOUTHWEST NEBRASKA. ALTHOUGH INSTABILITY IS LIMITED
/LATEST SPC MESOANALYSIS DATA HAD 1000-1500 J/KG SBCAPE/ AND
EFFECTIVE SHEAR OF 30-35KTS...THE SHEAR WILL BE INCREASING THROUGH
THE REMAINDER OF THE AFTERNOON AS THE WHOLE SYSTEM APPROACHES AND
WITH THE STRENGTH OF THE LARGE SCALE LIFT IN PLACE STORMS SHOULD BE
ABLE TO INTENSIFY EASILY THROUGH THE AFTERNOON AND EARLY EVENING
HOURS. WHILE PRIMARY THREATS LOCALLY WILL BE STRONG WINDS AND LARGE
HAIL FROM STORMS...WITH THE AMOUNT OF LOW LEVEL VORTICITY IN
PLACE...ESPECIALLY AS THE SURFACE LOW PROGRESSES NORTHWARD STORMS
SHOULD SPIN SO CAN/T DISCOUNT THE THREAT FOR TORNADO DEVELOPMENT.

COVERAGE IN THUNDERSTORM ACTIVITY WILL INCREASE THROUGH THE EVENING
HOURS AS THE UPPER LEVEL SYSTEM GETS CLOSER SO A FAIRLY FULL LINE OF
STORMS AND SHOWERS IS EXPECTED FROM NORTHWEST NEBRASKA THROUGH
SOUTHWEST NEBRASKA...WHICH THEN IS EXPECTED TO SWING TO THE
NORTHEAST IMPACTING MUCH OF THE FORECAST AREA. PRECIPITATION CHANCES
HAVE BEEN INCREASED FOR MOST AREAS THROUGH THE OVERNIGHT PERIOD AS
CONFIDENCE HAS INCREASED WITH HOW THE SYSTEM AND ASSOCIATED RAINFALL
WILL PROGRESS. PRECIPITABLE WATER VALUES WHERE THE LINE OF STORMS
AND SHOWERS IS EXPECTED WILL APPROACH 200 PERCENT OF NORMAL SO DO
BELIEVE MODERATE TO HEAVY RAINFALL WILL BE POSSIBLE...ESPECIALLY
UNDER STRONGER THUNDERSTORMS. HOWEVER WITH THE SYSTEM EXPECTED TO BE
FAIRLY PROGRESSIVE...EVEN WITH A BIT OF TRAINING WITH SHOWERS AND
STORMS THAT HAVE BEEN SEEN THROUGH THE DAY DON/T THINK FLOODING WILL
BE OF CONCERN AS ANTECEDENT CONDITIONS ARE FAIRLY DRY.

BY 12Z TUESDAY THE SYSTEM WILL HAVE STRENGTHENED AND BE STACKED AND
CENTERED OVER THE NORTHERN NEBRASKA PANHANDLE. AS THIS OCCURS...THE
BAND OF SHOWERS AND STORMS WILL PROGRESS TO THE EAST/NORTHEAST WHILE
MUCH OF THE FORECAST AREA WILL BE DRY SLOTTED. SHOWERS AND ISOLATED
THUNDERSTORMS WILL REMAIN LIKELY CLOSER TO THE VICINITY OF THE LOW
AS MOISTURE WRAPS AROUND INTO THE PANHANDLE AND NORTHWEST NEBRASKA.
MOVEMENT OF THE SYSTEM THROUGH THE DAY TUESDAY WILL BE SLOWLY TO THE
NORTHEAST AS AT 00Z WEDNESDAY IT IS EXPECTED TO BE OVER CENTRAL
SOUTH DAKOTA. THIS SLOW MOVEMENT WILL KEEP SHOWERS AND ISOLATED
THUNDERSTORMS POSSIBLE OVER NORTHWEST NEBRASKA THROUGH MUCH OF THE
DAY. IN ADDITION...STRONG WINDS ARE LIKELY ALSO IN THE VICINITY OF
THE SURFACE LOW AS A VERY TIGHT PRESSURE GRADIENT DEVELOPS. THE WIND
FORECAST HAS BEEN INCREASED FOR TUESDAY...BUT MAY NEED TO BE
INCREASED A BIT MORE. AT THIS TIME...WOULDN/T BE SURPRISED TO SEE A
PERIOD WITH 30KT SUSTAINED WINDS...WITH GUSTS TO 45KTS...MAINLY IN
THE MORNING HOURS.

AREAS THAT END UP IN THE DRY SLOT WILL SEE WARMER AIR BEING PULLED
INTO THE SYSTEM SO TEMPERATURES ACROSS THE FORECAST AREA COULD AGAIN
SEE A LARGE RANGE...FROM THE LOW 60S OVER THE NORTHWEST WHERE IT
WILL RAIN MUCH OF THE DAY...TO THE UPPER 70S OVER THE SOUTHEASTERN
AREAS WHICH WILL SEE SUNSHINE AND WARMER AIR IN PLACE.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 335 PM CDT MON SEP 29 2014

TUESDAY NIGHT THROUGH THURSDAY...LOW PRESSURE LIFTS INTO SRN CANADA
TUESDAY NIGHT AND WEDNESDAY AND WEAK PACIFIC HIGH PRESSURE BUILDS
INTO THE FCST AREA. THE MODELS ARE SHOWING A STRONG COLD FRONT
MOVING THROUGH WEDNESDAY NIGHT WITH FORMIDABLE DYNAMICS AND
MOISTURE. MOST OF THE ENERGY AND RESULTANT RAINFALL IS EXPECTED TO
MOVE THROUGH THE WRN AND SRN EDGES OF THE FCST AREA MAINLY AFFECTING
WY...COLO AND KS. IT IS A POSITIVELY TILTED TROF AT H700MB AND THIS
IS VERY TYPICAL OF THESE TYPES OF SYSTEMS WHICH ARE VERY EFFICIENT
AT DRIVING DRY AIR THROUGH THE FCST AREA WHICH LIMITS RAIN CHANCES.

H850MB TEMPERATURES FALL INTO THE SINGLE DIGITS BY THURSDAY MORNING
BUT GIVEN THE MID LEVEL CLOUD COVER SHOWN BY THE MODELS...NO FROST
IS EXPECTED THIS MORNING AS LOWS FALL INTO THE UPPER 30S NORTHWEST
TO UPPER 40S EAST. HIGHS NEAR 60 ARE EXPECTED WEDNESDAY IN THE
NORTHWEST AS COLD AIR BEGINS TO BUILD IN WITH 60S AND 70S ELSEWHERE.
60S ARE EXPECTED ALL AREAS THURSDAY WITH A WEAK SHOT OF WARM AIR
DEVELOPING AHEAD OF A SECOND COLD FRONT DUE TO MOVE THROUGH THURSDAY
NIGHT.

THURSDAY NIGHT THROUGH MONDAY...A FAST MOVING COLD FRONT AND
ATTENDANT CANADIAN HIGH PRESSURE SYSTEM MOVES THROUGH THE FCST AREA
THURSDAY NIGHT AND FRIDAY. THE COLD AIR RESIDES ON THE EAST SIDE OF
THE HIGH PRESSURE ACROSS THE UPPER MIDWEST. THIS HIGH IS TO BE
FOLLOWED BY LOW PRESSURE TRACKING THROUGH THE UPPER MIDWEST SATURDAY
AND SUNDAY WHICH WILL DRAW WARMER AIR OFF THE ROCKIES. MILD
CONDITIONS SHOULD CONTINUE MONDAY. NO RAIN IS EXPECTED THURSDAY
NIGHT THROUGH MONDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 642 PM CDT MON SEP 29 2014

THUNDERSTORMS TO CONTINUE OVER THE NEBRASKA PANHANDLE THROUGH THE
NIGHT AND SPREAD SLOWLY EAST INTO THE SANDHILLS AND SOUTHWEST
NEBRASKA THROUGH THE EARLY MORNING HOURS WITH MAIN ACTIVITY TO THE
WEST OF VALENTINE KVTN TO NORTH PLATTE KLBF LINE. SHOWERS AND
ISOLATED THUNDERSTORMS EXPECTED AT BOTH TAF SITES OVER NIGHT. MVFR
CEILINGS AND VISIBILITIES EXPECTED. STRONG SOUTHEASTERLY FLOW
SUSTAINED AT 25KTS EXPECTED.


&&

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

$$

UPDATE...POWER
SYNOPSIS...BROOKS/CDC
SHORT TERM...BROOKS
LONG TERM...CDC
AVIATION...POWER





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