Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 020837
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
337 AM CDT TUE JUN 2 2015

.SYNOPSIS...
ISSUED AT 334 AM CDT TUE JUN 2 2015

AT 08Z...AN AREA OF SHOWERS AND THUNDERSTORMS CONTINUES FROM
SOUTHWEST INTO SOUTH CENTRAL NEBRASKA. RECENT DEVELOPMENT IN EXTREME
NERN CO NOW MOVING INTO SWRN NEBR. TEMPERATURE MAINLY IN THE MID 60S
WITH DWPTS IN THE UPPER 50S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 334 AM CDT TUE JUN 2 2015

TODAY...LINGERING SHOWERS AND THUNDERSTORMS IN THE FORECAST THIS
MORNING ACROSS THE SRN PANHANDLE AND SWRN NEBR INTO EASTERN ZONES
UNTIL 16Z. THIS AIDED BY A WEAK DISTURBANCE CURRENTLY MOVE THROUGH
NERN CO AND THE NEBR/WYOMING STATE LINE. ALTHOUGH YET TO
DEVELOP...STRATUS IS FORECAST TO DEVELOP NEAR AND WEST OF HWY 83
TOWARD DAYBREAK...THEN SPREAD EAST AND SCATTERED OUT BY LATE
MORNING. SKIES SHOULD THEN BECOME PARTLY TO MOSTLY SUNNY IN THE AFTN.
FORECAST HIGHS THE WARMEST SEEN IN WEEKS RANGING FROM 82 TO 86.
STRONG INSTABILITY FROM 2500-3500 J/KG WILL DEVELOP BY MID/LATE AFTN
AS THE CAP WEAKENS BELOW 20 J/KG. A FAIRLY STRONG DISTURBANCE ALOFT
WILL MOVE INTO THE DAKOTAS AND WESTERN NEBRASKA THIS AFTERNOON WITH
ISOLATED THUNDERSTORMS EXPECTED TO DEVELOP NEAR AND WEST OF VTN
THROUGH ARTHUR AND IML.

TONIGHT...THE MAIN FORECAST CHALLENGES ARE PRECIPITATION CHANCES AND
LOCATIONS FOR SEVERE STORMS. THUNDERSTORMS ARE FORECAST TO INCREASE
RAPIDLY IN COVERAGE AND INTENSITY EARLY THIS EVENING. WHILE
DIFFERENCE EXIST ON LOCATION...CONSENSUS IS FOR THUNDERSTORMS TO
DEVELOP ACROSS CENTRAL CHERRY COUNTY SOUTHWARD INTO ARTHUR COUNTY IN
THE VICINITY OF THE FRONTAL BOUNDARY. 0-6KM SHEAR OF 30 TO 35 KTS
WILL BE ADEQUATE FOR SOME SEVERE STORMS. LOW LEVEL HELICITIES ARE
NOT OVERLY IMPRESSIVE...BUT WILL INITIATE ALONG THE GRADIENT OF
HIGHER HELICITIES SO A LIMITED TORNADO THREAT IS EXPECTED WITH
HAIL/WIND BEING THE MAIN SEVERE THREATS. SOME VERY LARGE HAIL OF
GOLFBALL OR LARGER IS POSSIBLE. WHILE DISCRETE STORMS ARE EXPECTED
EARLY THIS EVENING...STORMS SHOULD CONGEAL INTO A QUASI LINEAR MCS.
STORM MOTION SHOULD BE EAST SOUTHEAST AT 10 TO 15 MPH...BUT MAY
ACCELERATE IN SPEED OVER TIME. THIS MCS WILL LIKELY FORCE A FRONTAL
BOUNDARY SOUTH TO NEAR THE I80 CORRIDOR OVERNIGHT.

FOR THE FORECAST...LIKELY POPS AND HIGHEST CORRESPONDING QPFS BEGIN
BETWEEN VTN AND ARTHUR THEN EAST THROUGH BBW AND ONL OVERNIGHT.
HEAVY RAINFALL ALSO EXPECTED AS PWAT VALUES TO BE AROUND 150 PERCENT
OF NORMAL. MODEL QPFS LIKELY UNDERDOING EXPECTED VALUES.
THUS...LOCAL RAINFALL AMOUNTS WILL LIKELY EXCEED AN INCH PER HOUR.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 334 AM CDT TUE JUN 2 2015

WEDNESDAY BEGINS WITH SOUTHWEST FLOW AND SUBTLE HEIGHT FALLS ALOFT.
SURFACE LOW DEEPENS OVER EASTERN COLORADO DURING THE DAY AND
ESTABLISHES MOIST EASTERLY UPSLOPE FLOW TO THE NORTH OF A WARM
FRONT. MODELS CONTINUE TO OPPOSE EACH OTHER REGARDING THE POSITION
OF THE WARM FRONT ON WEDNESDAY...WHICH WILL BE HIGHLY DEPENDENT ON
THE EVOLUTION OF ELEVATED CONVECTION TUESDAY NIGHT INTO WEDNESDAY
AM. GFS HAS BEEN THE MOST CONSISTENT MODEL SOLUTION OVER THE LAST 24
HOURS...AND PUSHES CONVECTION EAST ALONG THE NOSE OF A VEERING LLJ
AND OUT OF THE CWA BY THE MORNING HOURS. THIS FAVORS A MORE
NORTHERLY POSITION OF THE WARM FRONT INTO SOUTHWEST
NEBRASKA...WHEREAS THE NAM CONTINUES CONVECTION IN THE CWA THROUGH
THE FIRST HALF OF THE DAY WITH COOL OUTFLOW PUSHING THE WARM FRONT
FURTHER SOUTH INTO KANSAS. THE FRONTAL POSITION WILL PLAY A LARGE
ROLE IN POTENTIAL SEVERE WEATHER THREATS. STORMS WILL LIKELY DEVELOP
ACROSS EASTERN COLORADO/WYOMING DURING PEAK HEATING HOURS AND TRACK
EAST INTO WESTERN NEBRASKA FOR THE EVENING. THE ENVIRONMENT OVER THE
HIGH PLAINS WILL BE FAVORABLE FOR THE DEVELOPMENT OF SEVERE
MULTI-CELLS/SUPERCELLS GIVEN SUFFICIENT INSTABILITY...VERY STEEP
MID-LEVEL LAPSE RATES...AND DEEP LAYER SHEAR OF 35+ KTS. LARGE HAIL
WILL BE THE PRIMARY THREAT...HOWEVER A FEW TORNADOES WILL BE
POSSIBLE IN THE VICINITY OF THE TRIPLE POINT AND EASTWARD ALONG THE
WARM FRONT WHERE LOW LEVEL HELICITY VALUES WILL BE MAXIMIZED. BASED
ON THE GFS...THIS WOULD FOCUS THE TORNADO THREAT GENERALLY ALONG AND
SOUTH OF THE I-80 CORRIDOR IN SOUTHWEST NEBRASKA. THE OVERALL SEVERE
THREAT DIMINISHES TO THE NORTH AND EAST WHERE LESS UNSTABLE
CONDITIONS WILL BE REALIZED. LOW LEVEL JET CRANKS UP AGAIN AFTER
SUNSET AND KEEPS CONVECTION GOING INTO THE OVERNIGHT PERIOD. LOCAL
PWATS REMAIN WELL ABOVE CLIMATOLOGICAL MEAN...SO THE POTENTIAL
FOR HEAVY RAINFALL WILL ONCE AGAIN NEED TO BE MONITORED.

A SIMILAR SYNOPTIC SCENARIO IS IN PLACE THURSDAY AS THE SURFACE LOW
HOLDS FIRM POSITION IN EASTERN COLORADO. UPSLOPE FLOW UNDERNEATH
STEEP LAPSE RATES ALOFT WILL MAINTAIN A THREAT FOR AT LEAST ISOLATED
SEVERE STORMS...HOWEVER THE CONVECTION FROM WEDNESDAY NIGHT WILL
LIKELY HAVE A SIGNIFICANT IMPACT ON THE LOCATION OF CRITICAL
BOUNDARIES/SURFACE FEATURES. TIMING MAY ALSO BE UNFAVORABLE AS
MODELS ARE SHOWING A SUBTLE SHORTWAVE APPROACHING THE CENTRAL PLAINS
EARLY IN THE DAY...WHICH WOULD LEAD TO AN EARLY ONSET FOR NEW
THUNDERSTORM DEVELOPMENT. FORECAST REMAINS ACTIVE FOR THE WEEKEND
AND BEYOND AS THE UPPER LEVEL PATTERN BECOMES INCREASINGLY
AMPLIFIED. A CUT OFF LOW DROPS SOUTH ALONG THE CALIFORNIA
COASTLINE...JUST WEST OF AN AMPLIFYING SHORTWAVE RIDGE IN THE
CENTRAL AND SOUTHERN PLAINS. TROPICAL MOISTURE WILL STREAM NORTHWARD
IN THE NEAR MERIDIONAL FLOW BETWEEN THESE TWO FEATURES...OUT OF THE
EASTERN PACIFIC AND ROUNDING THE RIDGE INTO THE CENTRAL ROCKIES AND
HIGH PLAINS. THIS WILL KEEP PRECIPITATION CHANCES IN THE FORECAST
FOR THE WEEKEND AND EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1242 AM CDT TUE JUN 2 2015

LIGHT RAIN AND VFR CEILINGS WILL CONTINUE AT KLBF THROUGH 08Z. THE
WIND WILL SWING AROUND TO THE SOUTHEAST AOB 10KTS IN THE WAKE OF
THE STORMS AND WILL THEN BRING SOME LOWER CEILINGS INTO BBW AND
LBF. CEILINGS ARE LIKELY TO BE 1000-1500 FEET AGL BUT THEY WILL
SCATTER OUT BY LATE TUESDAY MORNING.

THUNDERSTORMS ARE AGAIN POSSIBLE AFTER 22Z...ESPECIALLY IN NORTHERN
NEBRASKA (INCLUDING VTN...ANW...ONL...TIF AND MHN).

&&

.HYDROLOGY...
ISSUED AT 334 AM CDT TUE JUN 2 2015

CURRENT FLOOD WARNINGS FOR THE PLATTE...SOUTH PLATTE...AND NORTH
PLATTE RIVER SYSTEMS REMAIN IN PLACE. RIVER LEVELS SHOULD REMAIN
FAIRLY STEADY OR SLOWLY FALL ALONG THE SOUTH PLATTE AND PLATTE RIVER
SYSTEMS THROUGH THE END OF THIS WEEK. WHILE ROSCOE AND BRADY WILL
CONTINUE TO REMAIN ABOVE FLOOD STAGE THIS WEEK...THE STAGE AT NORTH
PLATTE IS SLIGHTLY BELOW FLOOD STAGE AT 12.75 FEET. AT THIS
LOCATION...A FLOOD ADVISORY WILL CONTINUE. RIVER LEVELS ALONG THE
NORTH PLATTE RIVER UPSTREAM OF LAKE MCCONAUGHY ARE FORECAST TO
REMAIN ABOVE FLOOD STAGE AND FALL SLOWLY THROUGH THE END OF THE
WEEK. THE STAGE AT LEWELLEN IS CURRENTLY 8.62 FEET...ABOVE THE
MODERATE FLOOD STAGE OF 8.5 FEET. THIS IS ACTUALLY VERY NEAR THE
STAGE DURING THE JUNE FLOODS OF 2011.

THE POTENTIAL FOR HEAVY RAINFALL WILL EXIST TONIGHT AND AGAIN
WEDNESDAY AFTERNOON AND NIGHT. THIS MAY  LEAD TO LOCALIZED FLASH
FLOODING AND THIS RUNOFF COULD CAUSE RIVER LEVELS TO RISE IN SOME
AREAS. PLEASE CHECK THE LATEST FLOOD WARNING FORECASTS.

&&

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

&&

$$

SYNOPSIS...ROBERG
SHORT TERM...ROBERG
LONG TERM...MARTIN
AVIATION...ROBERG
HYDROLOGY...ROBERG






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