Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 252331
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
631 PM CDT MON AUG 25 2014

.SYNOPSIS...
ISSUED AT 305 PM CDT MON AUG 25 2014

OVERALL...THE H5 PATTERN REMAINS LARGELY UNCHANGED FROM
YESTERDAY. HIGH PRESSURE WAS ANCHORED OVER THE LOWER OHIO RIVER
VALLEY WITH A RIDGE EXTENDING NEWD INTO SRN QUEBEC. ACROSS THE
WESTERN CONUS...A TROUGH OF LOW PRESSURE WAS PRESENT ACROSS THE
PACIFIC NORTHWEST...WITH A STRONG DISTURBANCE NOTED OVER SOUTH
CENTRAL OREGON. DOWN STREAM OF THIS FEATURE...A CLOSED LOW WAS
LOCATED OVER SRN MANITOBA WITH A NICE JET STREAK EXTENDING FROM
CENTRAL SD INTO WRN ONTARIO...WITH 70 KT H500 WINDS NOTED AT
ABERDEEN SOUTH DAKOTA THIS MORNING. ACROSS THE CENTRAL PLAINS...A
WEAK UPPER LEVEL DISTURBANCE BROUGHT SHOWERS AND THUNDERSTORMS TO
SOUTHERN AND EASTERN NEBRASKA THIS MORNING AND THIS IS EXITING THE
FORECAST AREA AS OF MIDDAY. UP STREAM...A SECONDARY WEAK DISTURBANCE
WAS NOTED OVER THE FOUR CORNERS. AT THE SURFACE...A COLD FRONT
EXTENDED FROM THE TWIN CITIES...SSWD INTO EXTREME SERN
NEBRASKA...THEN TOWARD FAR SERN COLORADO. LOW PRESSURE WAS SITUATED
ALONG THE FRONT FROM NORTHERN COLORADO INTO SWRN KS...WHILE HIGH
PRESSURE WAS PRESENT OVER EASTERN MT. SUBSIDENCE HAS PUSHED INTO
WESTERN AND NORTH CENTRAL NEBRASKA THIS AFTERNOON AS CONVECTION
EXITS THE AREA. THIS HAS LED TO PARTLY CLOUDY SKIES ACROSS THE
FORECAST AREA WITH TEMPERATURES GENERALLY IN THE 70S.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 305 PM CDT MON AUG 25 2014

UNSETTLED PATTERN TO CONTINUE TONIGHT WITH THE
APPROACH OF WESTERN CONUS MID LEVEL LOW.  THE MODELS REMAIN FIXED
THAT A DISTURBANCE WILL LIFT NORTHEAST FROM THE SOUTHERN ROCKIES
THIS EVENING AND INTERACT WITH A NORTHWARD RETREATING FRONT/SFC
BAROCLINIC ZONE.  ISENTROPIC UPGLIDE ON THE 310K SFC IS SHOWN TO
TARGET THE LIFTING H85 FRONT OVER SOUTHEASTERN PORTIONS OF THE CWA
FROM 03-09Z WHILE THE DISTURBANCE LIFTS NORTHEAST.  THE MODELS FOCUS
THE HEAVIEST QPF ALONG AND EAST OF A CENTRAL HAYES TO EASTERN
WHEELER COUNTY LINE...WHERE A GENERAL BLEND OF NAM...HPC...AND ARW
SUGGEST UP TO AN INCH OF RAIN COULD FALL.  BUFR SOUNDINGS REVEAL A
DEEPLY SATURATE PROFILE AFTER 3Z AS PWATS INCREASE OVER 1.50".  THIS
COMBINED WITH A EVER DEEPENING WARM CLOUD PROCESS AND NOTICEABLE
INDICATIONS OF ELEVATED UPRIGHT CONVECTION WOULD SUPPORT MODERATE TO
HEAVY RAIN ALONG AND NORTH OF THE BOUNDARY.  LOCALIZE FLOODING WOULD
BE A POSSIBILITY IF STORMS WERE TO TRAIN OVER THE BOUNDARY FOR
SEVERAL HOURS.  THERE IS A SLIGHT SIGNAL OF THIS AS THE 1000-500MB
THICKNESS & MEAN 500MB FLOW RUN SOMEWHAT PARALLEL TO THE LIFTING
BOUNDARY.

THERE ARE DIFFERENCES BETWEEN THE SHORT TERM MODELS ON WHERE THE
HEAVIEST EPICENTER OF QPF WILL FALL...THE NAM/ARW/RUC/HRRR SEEMS TO
TARGET OUR SOUTH TO SOUTHEASTERN PORTION OF THE CWA...WHEREAS THE
GFS/EC/GEM IS SOUTH IN KANSAS.  WILL FAVOR THE GUIDANCE OF THE GENERALLY
HIGH RES MODELS AS THE UPPER PATTERN WOULD DIRECT STORMS/COMPLEXES
OFF THE PALMER DIVIDE/EASTERN COLORADO GENERALLY INTO SOUTHERN
PORTIONS OF THE CWA.  UNFORTUNATELY CONFIDENCE ISN/T AS HIGH AS ONE
WOULD LIKE FOR DEFINITE QPF IN THE FORECAST...SO WILL GO WITH
LIKELY/S FOR NOW.

THE POP FORECAST MAY BE A BIT OVERDONE ACROSS OUR NORTHERN AND
NORTHWESTERN ZONES FOR THE OVERNIGHT...BUT WITH THE
UNCERTAINTY...DECIDED TO LEAVE AT LEAST A SLIGHT CHANCE MENTION IN
THE OFFICIAL FORECAST.

SHOWERS TO REMAIN IN THE FORECAST ON TUESDAY...HOWEVER WILL CAP
PERCENTAGES AS LESS THAN 40 PERCENT UNTIL 00Z WEDNESDAY.  THE
EXPECTED DISTURBANCE THIS EVENING SHOULD BE OFF TO THE EAST...WITH
THE NEXT STILL OVER THE ROCKIES.  SUBSIDENCE BEHIND THE FIRST WAVE
WILL HELP LIMIT POPS...BUT THERE REMAINS SUBSTANTIAL SPREAD IN THE
MODELS...WITH SEVERAL MEMBERS PRODUCING MEASURABLE QPF THROUGHOUT
THE SANDHILLS THROUGHOUT THE DAY.  MOISTURE AND LIFT IS SHOWN BY
THESE MEMBERS TO REMAIN IN THE REGION...THUS WILL CARRY AT LEAST A
SLIGHT CHANCE/LOW END CHANCE OF QPF THROUGH THE DAY.  OTHERWISE THE
STORY WILL BE THE ALMOST FALL LIKE HIGHS ANTICIPATED.  GENERALLY
SIDED TOWARD THE COOLER GUIDANCE SINCE PLENTIFUL CLOUDS SHOULD
IMPACT SOLAR INSOLATION.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 305 PM CDT MON AUG 25 2014

TUESDAY NIGHT THROUGH THURSDAY...THE MAIN FORECAST
CHALLENGE IN THE MID RANGE CONTINUES TO BE PRECIPITATION CHANCES AND
THE THREAT FOR HEAVY RAIN...PARTICULARLY ON TUESDAY NIGHT. FOR
TUESDAY NIGHT...THE MAIN UPPER LEVEL LOW WILL TRACK FROM NEVADA INTO
UTAH...WHILE A DECENT SHORTWAVE WILL PUSH EAST OF THIS FEATURE ONTO THE
CENTRAL PLAINS TUESDAY NIGHT. ATTM...THE MODELS CONTINUE TO CONVERGE
ON THE NOTION OF A DECENT THREAT FOR HEAVY RAIN DURING THE PERIOD.
THIS IS DUE TO SEVERAL FACTORS INCLUDING...A DEEP...AND BROAD AREA
OF LIFT PER CROSS SECTIONS...INDICATIVE OF A BROAD AREA OF SHOWERS
WITH EMBEDDED THUNDERSTORMS VS. A SKINNY LINE OF STORMS WHICH IS
EXPECTED TONIGHT. FORECAST SOUNDINGS TUESDAY NIGHT ARE INDICATIVE OF
A SKINNY CAPE SETUP WITH A DEEP WARM CLOUD LAYER AROUND 10000 FT AND
ABUNDANT LIFT CO LOCATED WITHIN THIS LAYER. DEEP LAYER MOISTURE WILL
BE ABUNDANT AS WELL AS PWATS REACH 1.8" FOR KLBF TUESDAY EVENING.
THIS SEEMS TO BE A RESULT OF MID AND HIGHER LEVEL MOISTURE...EVIDENT
FROM 315K AND 320K MOISTURE TRANSPORT FROM THE DESERT SW IN
ASSOCIATION WITH HURRICANE MARIE OVER THE EASTERN PACIFIC. AS FOR
PRECIPITATION CHANCES...THE MODELS CONTINUE TO INDICATE A WIDE BAND
OF EAST TO WEST ORIENTED PRECIPITATION...WHICH LIFTS SLOWLY NORTH
OVERNIGHT. WITH THIS IN MIND...STARTED THE PERIOD OUT WITH THE
HIGHEST POPS IN THE SRN CWA TUESDAY EVENING...TRANSITIONING THIS
SLOWLY NORTH OVERNIGHT. ON WEDNESDAY...THE LEAD SHORTWAVE
DISTURBANCE WILL LIFT NORTH INTO SOUTH DAKOTA. PRECIPITATION CHANCES
WILL DIMINISH TEMPORARILY DURING THE DAY AS SUBSIDENCE AND DRIER AIR
PUSHES INTO SOUTHWESTERN NEBRASKA AND PORTIONS OF THE WESTERN
SANDHILLS. BY WEDNESDAY EVENING...THE MAIN UPPER LEVEL LOW WILL
TRACK ACROSS COLORADO...EMERGING ONTO THE HIGH PLAINS OF EASTERN
COLORADO BY 12Z THURSDAY. A COLD FRONT WILL TRACK THROUGH WESTERN
AND NORTH CENTRAL NEBRASKA WEDNESDAY NIGHT WITH PRECIPITATION
FOCUSED INVOF THE COLD FRONT AND A SECOND AREA OVER NORTHERN
NEBRASKA WHERE A NICE DEFORMATION BAND OF PCPN WILL SET UP OVER THE
PINE RIDGE INTO NORTHERN NEBRASKA. ON THURSDAY...THE MAIN UPPER
LEVEL SYSTEM WILL TRACK SLOWLY INTO NWRN KS. ATTM...THE GREATEST
THREAT FOR PCPN WILL BE INVOF THE FRONTAL BOUNDARY FROM NORTHWEST KS
INTO EASTERN NEBRASKA. SMALLER CHANCES FOR PCPN WILL EXIST ACROSS
CENTRAL AND EASTERN PORTIONS OF THE FORECAST AREA AS STEEPENING
LAPSE RATES THURSDAY AFTERNOON MAY LEAD TO INSTABILITY SHRAS MAINLY
OVER THE EASTERN 2/3RDS OF THE FORECAST AREA.

THURSDAY NIGHT THROUGH MONDAY...THE UPPER LEVEL TROUGH AND LOW WILL
TRACK INTO EASTERN NEBRASKA THURSDAY NIGHT INTO FRIDAY...BRINGING AN
END TO PCPN CHANCES IN THE FORECAST AREA. AFTER DRY CONDS SATURDAY
AND SATURDAY NIGHT...THE ECMWF AND GFS SOLNS DIVERGE SLIGHTLY WITH
THEIR HANDLING OF THE NORTHERN STREAM. THE ECMWF SOLN REMAINS
PROGRESSIVE WITH ANOTHER UPPER LEVEL TROUGH CROSSING THE NRN ROCKIES
AND PLAINS SUNDAY INTO MONDAY WHILE THE GFS HOLDS BACK ON THE
TROUGH...KEEPING IT CONFINED TO SRN CANADA AND THE NRN TIER OF
STATES. CLOSER TO THE CENTRAL PLAINS...THE ECMWF SOLN HAS A DECENT
SHORTWAVE SYSTEM CROSSING THE CENTRAL ROCKIES LATE SUNDAY WHILE THE
GFS SOLN IS 24 HRS SLOWER WITH THIS FEATURE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 631 PM CDT MON AUG 25 2014

QUIET VRF EVENING ACROSS THE AREA...HOWEVER TONIGHT THINGS CHANGE.
A DISTURBANCE CURRENTLY ACROSS THE ROCKIES WILL PUSH ACROSS
PORTIONS OF THE STATE TONIGHT. MODELS ARE FOCUSING THE HEAVIEST
SHOWERS ACROSS SOUTHWEST INTO CENTRAL NEBRASKA...INCLUDING
KIML...KLBF AND KBBW. FURTHER NORTH SOME ISOLATED SHOWERS ARE
POSSIBLE...BUT NOT WIDESPREAD ENOUGH TO WARRANT MENTION IN THE
KVTN TAF YET.

A SECOND DISTURBANCE QUICKLY FOLLOWS WITH A PROB30 GROUP INCLUDE
FOR KLBF IN THE MORNING. AGAIN HIGHER CONFIDENCE OF ACTIVITY TO
REMAIN SE OF KVTN...OTHERWISE AFTERNOON CU DEVELOPS. THERE WILL
LIKELY BE REDEVELOPMENT IN THE AFTERNOON OF SHOWERS ACROSS THE
FRONT RANGE WHICH WILL LIFT ACROSS THE AREA...HOWEVER LOCATION
AND TIMING OF ACTIVITY IS LOW.

&&

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

&&

$$

SYNOPSIS...CLB
SHORT TERM...JACOBS
LONG TERM...CLB
AVIATION...MASEK




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