Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 261157
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
657 AM CDT TUE AUG 26 2014

.SYNOPSIS...
ISSUED AT 402 AM CDT TUE AUG 26 2014

A FRONTAL BOUNDARY IS DRAPED ACROSS CENTRAL KANSAS. SCATTERED AND
ISOLATED SHOWERS/THUNDERSTORMS OCCURRING OVER THE CENTRAL PLAINS.
MOST OF THIS ACTIVITY HOWEVER EXTENDS FROM EAST CENTRAL NEBRASKA
INTO WEST CENTRAL IOWA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 402 AM CDT TUE AUG 26 2014

FOR TODAY...

A POSITIVELY TILTED UPPER TROUGH EXTENDS ACROSS THE GREAT BASIN AS
AN UPPER RIDGE AXIS EXTENDS ACROSS THE TENNESSEE VALLEY. WV IMAGERY
AT 08Z INDICATES A DISTURBANCE WITHIN MONSOONAL MOISTURE LOCATED IN
CENTRAL AZ. THIS DISTURBANCE WILL BOTH LIFT NORTHEAST INTO CENTRAL
CO TODAY. A DECAYING MCV LOCATED IN SWRN NEBR IS CURRENTLY BRINGING
SCATTERED SHOWERS TO CENTRAL NEBRASKA AND SHOULD EXIT EASTERN FA
PRIOR TO 15Z. OTHER WEAK DISTURBANCE FROM NERN CO INTO SERN WY
BRINGING ADDITIONAL SCATTERED SHOWERS AND THUNDERSTORMS. AS THESE
MOVE NORTHEAST ACROSS WESTERN NEBRASKA THIS MORNING...COVERAGE
SHOULD BE ISOLATED AND END BY 18Z. KEPT A SLIGHT CHANCE THROUGH THE
AFTERNOON ACROSS THE EAST TO ACCOUNT FOR THIS. MODELS INDICATE
INCREASE LOW LEVEL MOISTURE TODAY WITH PARTLY TO MOSTLY CLOUDY SKIES
EXPECTED IN STRATOCUMULUS. THIS TO LIMIT HIGHS TODAY TO NEAR 75 NORTH
CENTRAL AND UPPER 70S SOUTHWEST.

FOR TONIGHT...

BY THIS EVENING...THE MAIN DISTURBANCE IN CENTRAL COLORADO WILL LIFT
NORTHEAST. FAVORING THE ARW AND NMM OUTPUT...AN ORGANIZED AREA OF
THUNDERSTORMS SHOULD EXTEND ACROSS NERN CO WITH DISJOINTED STORMS
EXTENDING NORTH INTO NWRN NEBR. AS THE NIGHT PROGRESSES...THE
FRONTAL BOUNDARY WILL LIFT NORTH INTO SOUTHWEST AND SOUTH CENTRAL
NEBRASKA OVERNIGHT. ELEVATED THUNDERSTORMS SHOULD BECOME ORGANIZED
NORTH OF THIS FRONT WITH AREAS OF HEAVY RAINFALL POSSIBLE. AGAIN
FAVORED THE ARW AND NMM ALONG WITH A BLEND OF THE 00Z NAM. THIS TO
BRING HIGHEST POPS OF 60 TO 80 PERCENT TO AREA SOUTH OF AN AINSWORTH
THROUGH ALLIANCE LINE. AREAS TO THE NORTH...20-30 POPS INCREASE TO
50 PERCENT AFTER MIDNIGHT. PWAT VALUES WILL INCREASE TO 1.5 TO 1.75
INCHES WHICH IS 150-180 PERCENT OF NORMAL. STORM MOTION SHOULD BE TO
THE EAST AND NORTHEAST NEAR 15 KTS. POTENTIAL FOR THUNDERSTORMS
MOVING ACROSS AND REDEVELOPING OVER SOME AREAS WILL BE A CONCERN FOR
RUNOFF AND LOCALIZED MINOR FLOODING. SINCE MANY AREAS DO NOT HAVE
SATURATED SOIL SO FAR...CONCERN FOR A FLOOD WATCH IS LOW. OF ANY
COUNTIES IN WRN NEBR...HAYES AND FRONTIER HAVE RECEIVED THE MOST
RAINFALL THE PAST TWO NIGHT AND WILL HAVE THE GREATEST POTENTIAL FOR
RUNOFF. RAINFALL POTENTIAL FOR A HALF INCH TO ONE INCH WITH LOCALLY
HIGHER AMOUNTS FOCUSED SOUTH OF A LINE FROM OGALLALA THROUGH
BREWSTER AND ONEILL.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 402 AM CDT TUE AUG 26 2014

FORECAST FOCUS FOR THIS PERIOD IS WITH CONTINUED THREAT FOR
SHOWERS AND THUNDERSTORMS WITH POTENTIAL HEAVY RAIN FOR WEDNESDAY
THROUGH THURSDAY.

THE MODEL OUTPUT IS COMING TOGETHER IN TERMS OF THE UPPER LEVEL
TROUGH PROGRESSING ACROSS THE CENTRAL CONUS. HOWEVER THERE REMAINS
SOME DIFFERENCES IN THE SPEED OF THE SYSTEM...WHICH IMPACTS THE
PRECIPITATION FORECAST AND THE CONFIDENCE IN THE PRECIPITATION
FORECAST FOR THIS CYCLE. THE GFS...WHICH HAD BEEN THE FAST SOLUTION
THE PAST SEVERAL DAYS IS NOW THE SLOWEST SOLUTION...WITH THE GEM NOW
WELL FASTER THAN THE GFS/ECMWF/AND NAM.

BY WEDNESDAY MORNING...MODELS ARE IN GOOD AGREEMENT WITH THE UPPER
LEVEL LOW/TROUGH CURRENTLY OVER NEVADA WILL MOVE EASTWARD SLIGHTLY
AND BE CENTERED OVER UTAH AT 12Z. WITH THE EASTWARD MOVEMENT OF THE
SYSTEM ALOFT LEADING TO INCREASED SOUTHERLY FLOW WHICH WILL HELP TO
PROMOTE THE NORTHWARD MOVEMENT OF THE SURFACE LOW AND WARM FRONT
WHICH WILL REMAIN OVER SOUTHEAST COLORADO AND ACROSS NORTHERN KANSAS
THROUGH TUESDAY NIGHT.

DURING THE DAY WEDNESDAY AND THROUGH WEDNESDAY NIGHT...THE MAIN
UPPER LOW  WILL MOVE INTO WESTERN COLORADO...WHILE THE MODELS ARE IN
GOOD AGREEMENT WITH A FAIRLY POTENT LEAD SHORTWAVE TROUGH MOVING
ACROSS NEBRASKA. STRONG LARGE-SCALE LIFT WILL BE IN PLACE OVER MUCH
OF THE FORECAST AREA DURING THE DAY WEDNESDAY AND WEDNESDAY NIGHT
WITH THE PASSING OF THIS UPPER LEVEL DISTURBANCE. THIS WAS SEEN
EASILY IN CROSS-SECTIONS OVER THE FORECAST AREA...AS WELL AS IN THE
ISENTROPIC OMEGA FIELDS AT 310K. THE SIGNALS CONTINUE TO SHOW A
THREAT OF HEAVY RAIN FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY
NIGHT. MODEL SOUNDINGS SHOW A NEARLY SATURATED COLUMN...BUT WITH
TALL SKINNY CAPE INDICATING ENOUGH INSTABILITY FOR AT LEAST EMBEDDED
THUNDERSTORMS THROUGH THE PERIOD. ALSO...PRECIPITABLE WATER VALUES
BETWEEN 1.25 AND 1.75 INCHES /GREATER THAN 150 PERCENT OF NORMAL/
FOR MOST OF THE FORECAST AREA AS WELL AS WARM CLOUD DEPTHS OF
GREATER THAN 10,000FT TO CONTINUE SHOWING THE POTENTIAL FOR HIGHLY
EFFICIENT RAINFALL PRODUCTION. THIS COULD LEAD TO AT LEAST LOCALLY
HEAVY RAINFALL. DID ADD IN MENTION OF HEAVY RAIN INTO THE AFTERNOON
PORTION OF THE FORECAST ON WEDNESDAY. ALTHOUGH THE SOUTHERN PARTS OF
THE FORECAST AREA RECEIVED RAIN TONIGHT...MOST LOCATIONS LIKELY SAW
UP 0.50 TO 1.50 INCHES SO NOT ENOUGH TO REALLY SATURATE THE GROUND
TO NEED DISCUSSIONS OF FLOOD WATCHES AT THIS POINT...DESPITE THE
POTENTIAL FOR HEAVY RAINFALL. WOULD LIKE TO SEE BETTER ANTECEDENT
CONDITIONS BEFORE GOING THAT ROUTE. ALSO...THE THREAT MOVES
NORTHWARD EACH DAY AS THE FRONT SLOWLY MOVES NORTH SO THE HEAVY
RAINS AREN/T EXPECTED OVER THE SAME AREAS EACH DAY...THIS
CORROBORATES WELL WITH THE WPC EXCESSIVE RAINFALL OUTLOOKS. WITH THE
PRECIPITATION EXPECTED TO LAST MUCH OF THE DAY...LOOKING AT FAIRLY
CHILLY TEMPERATURES FOR HIGHS. SOME MODELS WERE SUGGESTIVE OF HIGHS
IN THE 60S...BUT THE AIRMASS ISN/T THAT COLD AND IF THERE ARE BREAKS
IN THE CLOUDS FOR A SHORT PERIOD OF TIME SHOULD BE ENOUGH TO WARM
THE AREA INTO THE 70S AND EVEN NEAR 80 OVER SOUTHERN NEBRASKA WHERE
THE RAINFALL ISN/T EXPECTED TO BE AS WIDESPREAD THROUGH THE ENTIRE
DAY.

THE MODELS BEGIN DIVERGING WITH THE SPEED OF THE TROUGH ON
THURSDAY...ALTHOUGH ALL ARE NOW SHOWING A SIGNAL FOR THE RAIN TO BE
ENDING SOMETIME THURSDAY OR THURSDAY NIGHT FOR MUCH OF THE AREA.
WITH SOME UNCERTAINTY WITH THIS AND AS THE GFS IS NOW KEEPING RAIN
ACROSS THE AREA THROUGH FRIDAY NIGHT THE FORECAST IS TRENDING DRIER
BY THURSDAY NIGHT WITH JUST SLIGHT CHANCES FOR FRIDAY...BUT NOT
GOING COMPLETELY DRY UNTIL SATURDAY. TEMPERATURES WILL REMAIN COOL
THROUGH FRIDAY WITH COOLER AIR IN PLACE BEHIND THE TROUGH AND QUITE
A BIT OF CLOUD COVER. TEMPERATURES SHOULD START TO RECOVER OVER THE
WEEKEND WITH NEAR NORMAL TEMPERATURES EXPECTED FOR SATURDAY THROUGH
MONDAY.

THE NEXT CHANCES FOR RAIN WILL COME EARLY NEXT WEEK AS THERE IS GOOD
AGREEMENT FROM THE LONG-RANGE MODELS WITH ANOTHER SHORTWAVE TROUGH
MOVING OUT OF THE NORTHERN PACIFIC AND INTO THE NORTHERN AND CENTRAL
PLAINS. AT THIS TIME...RAIN CHANCES HAVE BEEN INCLUDED IN THE
FORECAST STARTING SUNDAY NIGHT AND CONTINUING INTO THE LABOR DAY
HOLIDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 656 AM CDT TUE AUG 26 2014

SCATTERED SHOWERS WILL PASS THE KLBF TAF UNTIL 15Z. OTHERWISE...
VFR CONDITIONS ARE EXPECTED TODAY. LOWEST CEILINGS OF BKN050 ARE
EXPECTED TO SET IN AFTER 15Z. FOR TONIGHT...THUNDERSTORMS ARE
LIKELY AFTER 03Z. HAVE INCLUDED A TEMPO FOR 3SM +TSRA BKN025 AFTER
06Z. FOR KVTN...VFR CONDITIONS THROUGH THE TAF PERIOD. HAVE
INCLUDED A TEMPO FOR P6SM -TSRA AFTER 09Z.

&&

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

$$

SYNOPSIS...ROBERG
SHORT TERM...ROBERG
LONG TERM...BROOKS
AVIATION...ROBERG








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