Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 241139
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
639 AM CDT SUN AUG 24 2014

.SYNOPSIS...
ISSUED AT 403 AM CDT SUN AUG 24 2014

A PACIFIC FRONT HAS PUSHED THROUGH MOST OF WESTERN NEBR. DRIER AIR
HAS WORKED INTO THE PANHANDLE WITH DEWPOINTS RANGING IN THE LOWER TO
MID 40S. A DEWPOINT NEAR 70 STILL AT ONL...WHERE PACIFIC FRONT HAD
NOT YET REACHED. SCATTERED SHOWERS AND THUNDERSTORMS CONTINUED IN
NERN NEBR...WITH THE MAJORITY OF STORMS EXITING ERN SOUTH DAKOTA AND
MOVING INTO WESTERN MINNESOTA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 403 AM CDT SUN AUG 24 2014

FOR TODAY...

THE SYSTEM CURRENTLY EXITING THE FORECAST AREA WILL CONTINUE TO
BRING PARTLY TO MOSTLY CLOUDY CONDITIONS TO THE SERN HALF OF FA
THROUGH EARLY AFTERNOON. CANNOT RULE OUT A BRIEF LIGHT SHOWER OR A
FEW SPRINKLES...ALTHOUGH MODELS INDICATE LIFT WILL BE INSUFFICIENT
FOR A MENTION. BEHIND THE WEAK PACIFIC COLD FRONT...HIGHS TODAY WILL
BE ABOUT 1 TO 3 DEGREES BELOW CLIMO RANGING FROM NEAR 83 SOUTHEAST
TO THE UPPER 70S FAR NORTHWEST. A WESTERLY DOWNSLOPE WIND WILL ALSO
LOWER DEWPOINTS INTO THE 40S WEST HALF WITH LOW TO MID 50S EAST.

FOR TONIGHT...

MODELS ARE IN FAIRLY GOOD AGREEMENT WITH A MID LEVEL DISTURBANCE
CURRENTLY LOCATED IN SWRN UTAH LIFTING NORTHEAST INTO NORTH CENTRAL
COLORADO BY 00Z MONDAY. FORECAST TO BE FAIRLY CLOSE TO PREVIOUS
BRINGING IN A SLIGHT CHANCE EARLY THIS EVENING IN SWRN NEBR...TO
20-30 POPS SOUTH OF HWY 2 BY 06Z...THEN 20-30 POPS NORTH TO NEAR HWY
20 LATE TONIGHT. GIVEN FASTER SWRLY FLOW...FAVORED THE FASTER TIMING
OF THE NAM MODEL TONIGHT. REGARDING THE SURFACE FRONT...IT IS
FORECAST TO STALL AND LIFT BACK NORTH SLIGHTLY TO A NWRN KS/SERN NEBR
LINE BY 12Z TUESDAY.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 403 AM CDT SUN AUG 24 2014

PRIMARY FORECAST CONCERNS DEAL WITH THUNDERSTORM CHANCES AND
POTENTIAL FOR HEAVY RAIN MONDAY NIGHT THROUGH TUESDAY NIGHT...THEN
WITH PRECIPITATION CHANCES LATE IN THE WEEK. ALSO LOOKING AT
COOLER TEMPERATURES THROUGH THE PERIOD.

OVER THE NEXT 24 HOURS THE UPPER LEVEL SYSTEM CENTERED OVER MONTANA
WILL CONTINUE TO MOVE EAST NORTHEAST...WHILE THE TROUGH MOVING
SOUTHEAST DOWN THE BRITISH COLUMBIA COAST WILL DIG SOUTH TOWARDS THE
GREAT BASIN.

SHOWER AND THUNDERSTORM CHANCES REMAIN IN THE FORECAST FOR MONDAY AS
CONVECTION LOOKS TO DEVELOP OVER COLORADO OVERNIGHT ON THE NOSE OF
THE LOW LEVEL JET. IN THE SOUTHWEST FLOW...THIS ACTIVITY SHOULD
TRAVEL EAST NORTHEAST...IMPACTING MUCH OF WESTERN AND NORTH CENTRAL
NEBRASKA. TEMPERATURES WILL BE COOLER...ESPECIALLY OVER NORTHERN
NEBRASKA WHERE MUCH COOLER TEMPERATURES ADVECT INTO THE REGION
/850MB TEMPERATURES DO RECOVER THROUGH THE DAY...BUT STILL ONLY IN
THE MID TEENS BY 00Z TUESDAY. SOME MODEL SOLUTIONS WOULD DROP THE
HIGH TEMPERATURES DOWN INTO THE 60S OVER NORTHERN NEBRASKA...BUT
WITH SOME SUNSHINE POSSIBLE...SHOULD AT LEAST REACH THE LOW 70S AS
IS IN THE FORECAST.

MONDAY NIGHT THROUGH TUESDAY NIGHT...WET WEATHER IS EXPECTED FOR
MUCH OF THE FORECAST AREA. IN THE MID LEVELS...MOISTURE TRANSPORT
VECTORS SHOW A FETCH OF MOISTURE BEING PULLED INTO THE CENTRAL
PLAINS FROM HURRICANE MARIA OFF OF THE BAJA CALIFORNIA COAST. WHILE
THE MID LEVELS BECOME MOISTENED FROM THIS PROCESS...GOING DOWN
TOWARDS THE SURFACE...THE GULF OPENS UP WITH A RIDGE OF HIGH
PRESSURE IN PLACE OVER THE OHIO RIVER VALLEY INTO THE SOUTHEASTERN
PART OF THE COUNTRY. THIS FLOW WILL INCREASE THE MOISTURE IN THE
LOWER LEVELS...MEANWHILE AT THE SURFACE HIGH PRESSURE OVER THE
NORTHERN PLAINS WILL LEAD TO EASTERLY SURFACE FLOW. MODELS ARE
SHOWING SURFACE DEWPOINTS FROM THE UPPER 60S THROUGH THE MID 70S
ACROSS IOWA WHICH WILL BE ADVECTED WESTWARD INTO THE AREA. THE
COMBINATION OF THESE PROCESSES WILL LEAD TO A DEEP MOIST
TROPOSPHERE...WITH PRECIPITABLE WATER VALUES UP BETWEEN 1.50 AND
2.00...ESPECIALLY OVER CENTRAL AND EASTERN NEBRASKA. THESE VALUES
ARE AROUND 2 STANDARD DEVIATIONS ABOVE NORMAL. IN ADDITION...WARM
CLOUD DEPTHS MONDAY NIGHT THROUGH TUESDAY NIGHT ARE QUITE DEEP... >=
3500 M. THIS WOULD SUGGEST HIGH PRECIPITATION EFFICIENCY.
ALSO...FORECAST SOUNDINGS ARE SHOWING TALL...SKINNY CAPE THROUGH THE
36 HOUR TIME FRAME SO WILL LIKELY HAVE THUNDERSTORMS WITH THIS
ACTIVITY. AT THE SURFACE...MODELS CONTINUE TO SHOW A LOW OVER
SOUTHEAST COLORADO MONDAY NIGHT WHICH STAYS FAIRLY STATIONARY UNTIL
THE UPPER LEVEL TROUGH STARTS TO MOVE INTO THE PLAINS AND KICK IT
EASTWARD DURING THE DAY WEDNESDAY. A WARM FRONT EXTENDS NORTHEAST
THROUGH SOUTH CENTRAL NEBRASKA AND ALSO STAYS NEARLY STATIONARY
THROUGH THIS PERIOD. ALTHOUGH NOT OVERLY ROBUST...THE MODELS DO
DEVELOP A NOCTURNAL LOW LEVEL JET BOTH MONDAY NIGHT AND TUESDAY
NIGHT TO ENHANCE THE LIFT OVER THE WARM FRONT AND INCREASE SHOWER
AND STORM DEVELOPMENT. THIS IS THE AREA THAT WILL BE THE FOCUS FOR
HEAVY RAIN. ALTHOUGH THE LOCATION OF THE WARM FRONT WILL DETERMINE
WHAT AREAS RECEIVE THE HEAVY RAIN...THERE HAS BEEN A GOOD AMOUNT OF
CONSISTENCY THAT THIS WILL OCCUR SOMEWHERE OVER NEBRASKA...MOSTLY
LIKELY OVER THE SOUTHERN AND CENTRAL PARTS OF THE STATE. WITH GOOD
MODEL CONSISTENCY AND STRONG SIGNALS FOR THE POTENTIAL FOR HEAVY
RAIN HAVE ADDED MENTION OF LOCALLY HEAVY RAIN INTO THE FORECAST FOR
BOTH MONDAY NIGHT AND TUESDAY NIGHT.

HAVE MODIFIED TUESDAY/S PRECIPITATION CHANCES SLIGHTLY WITH THE
THOUGHTS THAT THERE MIGHT BE A RECOVERY PERIOD DURING THE DAY...MOST
LIKELY BETWEEN 15Z AND 21Z WHERE LITTLE ACTIVITY WILL BE ONGOING.
WITH THE UNCERTAINTY TO HOW TUESDAY WILL PLAY OUT AS SOME MODELS
CONTINUE TO KEEP RAIN GOING THROUGH THE DAY...REALISTICALLY DON/T
KNOW IF THAT WILL HAPPEN. BUT WILL POTENTIALLY STILL HAVE SOME
LINGERING ACTIVITY IN THE MORNING...ALONG WITH STORMS STARTING TO
DEVELOP IN THE AFTERNOON SO WILL KEEP THE CHANCE PRECIPITATION
CHANCES GOING THROUGH MUCH OF THE DAY UNTIL THERE IS BETTER
CONFIDENCE IN TIMING.

PRECIPITATION SHOULD BEGIN TO TAPER OFF ON WEDNESDAY...WITH A
LOWERING TREND THROUGH THE END OF THE WEEK. HOWEVER THERE IS A LARGE
AMOUNT OF UNCERTAINTY IN THE FORECAST FROM WEDNESDAY ON THROUGH NEXT
WEEKEND. THIS IS OCCURRING WITH DIFFERENCES IN THE PROGRESSION OF THE
TROUGH MOVING EAST THROUGH THE PLAINS AND EXITING THE REGION. FROM
THE 00Z MODELS...THE GFS CONTINUES TO BE THE FASTEST SOLUTION IN
TERMS OF THE EASTWARD PROGRESSION OF THE TROUGH OUT OF THE PLAINS.
HOWEVER...THE 18Z RUN WAS SLOWER AND MORE IN LINE WITH THE ECMWF AND
GEM. THIS LEADS TO FORECAST PROBLEMS DEALING WITH PRECIPITATION FOR
WEDNESDAY AND BEYOND. THE SPEED OF THE SYSTEM THROUGH THE AREA WILL
ALSO IMPACT THE TEMPERATURE FORECAST. AT THIS TIME...THE FORECAST
FOLLOWS A BLEND OF THE MODEL SOLUTIONS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 631 AM CDT SUN AUG 24 2014

ANY ISOLATED SHOWERS HAVE SHIFTED JUST EAST OF THE KLBF TERMINAL.
THERE WILL BE BROKEN CLOUDINESS UNTIL 16Z...THEN SCT120.
INTRODUCED A PROB30 GROUP ATER 06Z/25TH. AT KVTN MOSTLY SUNNY
TODAY WITH JUST SCT120 AT TIMES.

&&

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

&&

$$

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










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