Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 202014
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
314 PM CDT WED MAY 20 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 313 PM CDT WED MAY 20 2015

AT 20Z AN UPPER LEVEL SHORTWAVE WAS SLOWLY MOVING ACROSS THE
NORTHERN PLAINS...WITH WIDESPREAD CLOUD COVER PRESENT OVER THE STATE
OF NEBRASKA. WEAK COLD AIR ADVECTION IN THE 850MB TO 700MB LAYER WAS
PROMOTING STEEP LAPSE RATES AND THE DEVELOPMENT OF ISOLATED RAIN
SHOWERS THIS AFTERNOON...GENERALLY FROM NORTH PLATTE TO THEDFORD AND
POINTS EAST. THIS ACTIVITY WILL DIMINISH BY THE EVENING HOURS. DRIER
AIR AND CLEARING SKIES WILL BEGIN TO MOVE INTO NORTHERN NEBRASKA BY
SUNSET AND STEADILY ADVANCE SOUTH. THE CLEARING SKIES COMBINED WITH
SFC HIGH PRESSURE WILL SET THE STAGE FOR ANOTHER COOL NIGHT OVER THE
FORECAST AREA AND THE POTENTIAL FOR FROST. LOWEST TEMPERATURE
READINGS NEAR TO JUST BELOW FREEZING WILL OCCUR OVER THE CENTRAL
/NORTHERN SANDHILLS AND WESTWARD INTO THE NORTHEAST PANHANDLE. A
FROST ADVISORY HAS BEEN ISSUED FOR TONIGHT INTO EARLY THURSDAY
MORNING TO COVER THIS AREA. A FEW SPOTS WHERE REMNANT SNOW COVER
STILL REMAINS MAY DROP BELOW 30 DEGREES TONIGHT...BUT THIS SHOULD BE
ISOLATED. MORE UNCERTAINTY REMAINS WITH RESPECT TO HOW FAR SOUTH THE
CLEARING WILL ADVANCE. AT THIS TIME MODEL CONSENSUS KEEPS THE I-80
CORRIDOR AND POINTS SOUTH UNDERNEATH SOME MID TO LOW LEVEL CLOUDS
THROUGH THE NIGHT...WHICH WOULD KEEP TEMPERATURES ABOVE FREEZING.

WARMER CONDITIONS...ALBEIT STILL BELOW NORMAL...ARE IN STORE FOR
TOMORROW AS A TRANSIENT SHORTWAVE RIDGE MOVES OVER THE HIGH PLAINS.
THE RETURN OF SOUTHERLY FLOW IN THE MID-LEVELS WILL BEGIN TO ADVECT
MOISTURE BACK OVER SOUTHWEST NEBRASKA. ANY STUBBORN CLOUD COVER WILL
KEEP TEMPERATURES DOWN A FEW DEGREES...SO EXPECTING THE WARMEST
READINGS IN THE UPPER 60S IN THE NORTHEAST PART OF THE CWA.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 313 PM CDT WED MAY 20 2015

THURSDAY NIGHT THROUGH SATURDAY...A WELL ADVERTISED H700 MB WARM
FRONT WILL LIFT NORTH THROUGH THE FCST AREA THROUGHOUT THE DAY
FRIDAY BEGINNING IN THE SOUTHWEST AFTER 06Z THURSDAY NIGHT.

THE RAIN FORECAST FRIDAY NIGHT AND SATURDAY IS UNCERTAIN GIVEN THE
DRY AIR MOVING IN ALOFT BEHIND THE WARM FRONT. THE MOISTURE BELOW
700 MB REMAINS IN PLACE...ESPECIALLY BELOW H850 MB. THUS OVERCAST
SKIES WOULD CONTINUE FRIDAY NIGHT AND SATURDAY.

WITH THE APPROACH OF A DEEP UPPER LOW...CURRENTLY OFF THE WEST
COAST...LAPSE RATES STEEPEN AFTER MIDNIGHT FRIDAY AND CONTINUE
THROUGH SATURDAY. MOISTURE INCREASES WITH PWAT APPROACHING OR
EXCEEDING 1 INCH. THUS K INDICES INCREASE TO OVER 30C AND 750 MB
COMPUTED CAPE INCREASES ACCORDING SIGNALING THUNDERSTORM POTENTIAL.

THE RAIN ASSOCIATED WITH THE H700 MB WARM FRONT FRIDAY APPEARS
MAINLY STRATIFORM WITH EMBEDDED SHOWERS. K INDICES ARE IN THE
20S...LESS THAN 30C.

TEMPERATURES FRIDAY RISE INTO JUST THE 50S UNDER THE RAIN SHIELD.
COOL AIR CONTINUES TO CIRCULATE NORTHWEST AROUND THE HIGH CURRENTLY
IN PLACE ACROSS THE CNTL PLAINS. UPSLOPE WINDS...MOISTURE AND THE
COOL HIGH SHOULD PRODUCE THESE HIGHS.

CONVECTIVE RAIN CHANCES SATURDAY COULD PRODUCE A FEW STRONG OR
SEVERE STORMS...MAINLY ELEVATED. A SFC WARM FRONT IS FORECAST TO
LIFT NORTH TO NEAR INTERSTATE 80 LATE IN THE AFTERNOON. LAPSE RATES
FROM 850MB AND UP BECOME STEEP AND H300 MB WINDS INCREASE TO
70-100KT WHICH IS QUITE STRONG AND WELL WITHIN THE PARAMETERS FOR
SEVERE WEATHER. THE NAM SHOWS 800MB COMPUTED CAPE INCREASING TO 2800
J/KG ACROSS SWRN NEB AT 21Z SATURDAY AND CLOSE TO 2000 J/KG ALONG
INTERSTATE 80 AT 00Z SATURDAY EVENING.

THE BEST LIFT FOR THUNDERSTORMS FRIDAY NIGHT AND SATURDAY DEVELOPS
ACROSS KS COINCIDENT WITH A RAPID INCREASE IN PWAT. CONVECTIVE
DEVELOPMENT ACROSS KS AND WRN/NCNTL NEB PROBABLY DEVELOPS AS A
RESULT OF GRADUALLY STEEPENING LAPSE RATES AS THE UPPER LOW
APPROACHES VERSUS BRUTE FORCING.

1/3 TO LOCALLY 1/2 INCH OR MORE RAINFALL IS EXPECTED IN A 6 HOUR
PERIOD FRIDAY. POPS ARE DEFINITE AT 80 PERCENT. THEREAFTER...A SHARP
INCREASE IN ELEVATED INSTABILITY DEVELOPS LATE FRIDAY NIGHT
TRIGGERING A ROUND OF SHOWERS AND THUNDERSTORMS. POPS FRIDAY NIGHT
INCREASE TO 60 PERCENT AFTER DROPPING OFF FRIDAY EVENING. SCATTERED
POPS ARE IN PLACE SATURDAY. QPF TOTALS FRIDAY AND SATURDAY COULD BE
LOCALLY HEAVY. THE GFS SUGGESTED 1/2 ACROSS SWRN NEB LATE FRIDAY
NIGHT.

SATURDAY NIGHT THROUGH WEDNESDAY...THE UPPER LOW AND ATTENDANT SFC
LOW PRESSURE LIFTS THROUGH THE CNTL PLAINS SUNDAY PRESENTING THE
ONLY HONEST RAIN CHANCE THROUGH WEDNESDAY. THEREAFTER A DISTURBANCE
MOVES THROUGH KS MONDAY FOLLOWED BY A SECOND ONE THROUGH THE DAKOTAS
TUESDAY. RAIN CHANCES APPEAR ISOLATED AFTER SUNDAY BUT THIS COULD BE
RAISED DEPENDING ON THE TRACK OF THESE SYSTEMS.

THE GEF AND OTHER MODELS ARE SHOWING A WARMING TREND WITH SFC LOW
PRESSURE MIGRATING INTO NRN NEB/SRN SD BY WEDNESDAY. H850
TEMPERATURES WARM INTO TEENS TO NEAR 20C. THE BAIS CORRECTED DATA
KEEPS HIGHS IN THE 60S TO LOWER 70S WHILE THE DETERMINISTIC SOLNS
SHOW A SHARP RISE INTO THE 70S TO NEAR 80 TUESDAY AND WEDNESDAY. THE
FORECAST CALLS FOR 60S SUNDAY AND 70S MONDAY AND BEYOND. LATER
FORECAST MAY HAVE TO MARK UP HIGHS TUESDAY AND WEDNESDAY. THE GFS
SHOWS 75 TO 85 TUESDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1248 PM CDT WED MAY 20 2015

MVFR CIGS WILL CONTINUE ACROSS ALL OF WESTERN AND NORTH CENTRAL
NEBRASKA THROUGH LATE WEDNESDAY AFTERNOON. CIGS HAVE BEEN TRENDING
HIGHER OVER THE LAST SEVERAL HOURS AND SHOULD RISE INTO THE VFR
CATEGORY PAST 21Z. GRADUAL CLEARING WILL COMMENCE AFTER DARK
ACROSS NORTHERN NEBRASKA AND SPREAD SOUTH THROUGH THE OVERNIGHT.
STILL SOME UNCERTAINTY WITH HOW FAR SOUTH THE CLEARING WILL
ADVANCE...BUT VFR CIGS ARE EXPECTED WITH ANY CLOUD COVER OVERNIGHT
INTO THURSDAY MORNING.

&&

.HYDROLOGY...
ISSUED AT 313 PM CDT WED MAY 20 2015

THE SOUTH PLATTE AND PLATTE RIVERS IN SOUTHWEST NEBRASKA CONTINUE TO
SLOWLY RECEDE AS OF WEDNESDAY AFTERNOON. ADDITIONAL MINOR REDUCTIONS
IN RIVER LEVELS WILL CONTINUE THROUGH THE NEXT 24 TO 48 HOURS BEFORE
HOLDING STEADY THROUGH THE WEEKEND. RECENT RAINFALL IN THE UPSTREAM
SOUTH PLATTE RIVER BASIN WILL BRING ADDITIONAL RIVER LEVEL RISES FOR
THE FIRST HALF OF NEXT WEEK...HOWEVER THE CRESTS SHOULD NOT BE
HIGHER THAN WHAT WAS EXPERIENCED LAST WEEKEND AND EARLIER THIS WEEK.

MORE SHOWERS AND THUNDERSTORMS ARE FORECAST WITHIN THE RIVER BASIN
LATER THIS WEEK. WHILE THE RAINFALL IS NOT EXPECTED TO RESULT IN
IMMEDIATE RISES ALONG THE RIVER...IT MAY BE A CONCERN FOR LOCAL
FLOOD MITIGATION EFFORTS DUE TO LOCALLY HEAVY RAINFALL RATES. THE
ADDITIONAL RAINFALL AND SNOW MELT RUNOFF FROM THE COLORADO FRONT
RANGE WILL KEEP ELEVATED FLOWS ON THE SOUTH PLATTE AND PLATTE RIVERS
IN SOUTHWEST NEBRASKA THROUGH THE END OF THE MONTH.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
FROST ADVISORY FROM MIDNIGHT CDT /11 PM MDT/ TONIGHT TO 8 AM CDT
/7 AM MDT/ THURSDAY FOR NEZ004-005-022>025-035>037-094.

&&

$$

SHORT TERM...MARTIN
LONG TERM...CDC
AVIATION...MARTIN
HYDROLOGY...MARTIN






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