Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 252328
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
628 PM CDT MON MAY 25 2015

.SYNOPSIS...
ISSUED AT 402 PM CDT MON MAY 25 2015

SLOW MOVING LOW PRESSURE SYSTEM MOVING ACROSS THE STATE TODAY.
NORTHWEST DEFORMATION ZONE PRODUCING SHOWERS WITH A FEW EMBEDDED
THUNDERSTORMS. REPORTS OF 1 TO 2 INCHES WITH PORTIONS OF THIS AREA
THIS AFTERNOON. A COLD FRONT FROM THE LOW IS STRETCHED ALONG THE
EASTERN CWA. THUNDERSTORMS ARE STARTING TO FIRE ALONG THE
BOUNDARY...AND LIFT TO THE NORTHEAST. ALSO SEEING SOME ISOLATED
SHOWERS ACROSS THE REST OF THE AREA AS WRAP AROUND MOISTURE REMAINS
HIGH WITH COLD AIR ALOFT CREATING ENOUGH INSTABILITY TO PRODUCE SOME
SHOWERS.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 402 PM CDT MON MAY 25 2015

BUSY AFTERNOON WITH RECENT RAINS CAUSING BOTH THE NORTH PLATTE RIVER
UPSTREAM OF LAKE MCCONAUGHY AND THE SOUTH PLATTE RIVER TO SEE A
TREND UPWARD IN FLOWS...SEE HYDRO SECTION.

LOW PRESSURE WILL CONTINUE TO SLOWLY PUSH EAST...AS A WEAK SFC HIGH
PRESSURE MOVES IN. DEFORMATION ZONE SHOULD WEAKEN OVERNIGHT AS THE
FRONTAL BOUNDARY ACTIVITY INCREASES. STILL WILL SEE SOME ISOLD TO
SCT SHOWERS IN THE WRAP AROUND. BL MOISTURE REMAINS RICH AND SOME
FOG OR STRATUS CANNOT BE RULED OUT.

BY TOMORROW THE SFC HIGH WILL LIMIT PRECIP AS IT BRING SLIGHTLY
DRIER AIR...HOWEVER AN UPPER LEVEL DISTURBANCE WILL PUSH INTO THE
REGION. THE LOWER LEVELS MAY BE DRYING...BUT RICH ELEVATED MOISTURE
IS RETAINED AS PWATS STILL 0.75 TO 1.00 INCHES ACROSS THE REGION.
THUS WILL CONTINUE TO MENTION SHOWERS WITH THE NEXT IMPULSE.
INSTABILITY AND SHEAR IS WEAK SO PRIMARILY WILL BE SHOWERS ALTHOUGH
A FEW RUMBLES OF THUNDER WILL BE POSSIBLE.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 402 PM CDT MON MAY 25 2015

ACCORDING TO THE NAM12 THIS MORNING...A NARROW PLUME OF GULF
MOISTURE ON THE HIGH PLAINS WILL ENHANCE THE MOISTURE GRADIENT
ACROSS WESTERN NEBRASKA AND EASTERN COLORADO WEDNESDAY. WITH A
RESULTING 875MB BASED LIFTED INDEX OF -5C TO -8C IN THAT
GRADIENT...FAIRLY STRONG THUNDERSTORM DEVELOPMENT IS LIKELY
WEDNESDAY AFTERNOON OVER SOUTHWEST NEBRASKA. STORMS WILL THEN SPREAD
NORTH AND EAST ACROSS THE NEBRASKA PANHANDLE AND THE SANDHILLS
WEDNESDAY AFTERNOON AND EARLY EVENING. WITH PRECIPITABLE WATER AT OR
ABOVE 0.75 INCH...MODERATE TO HEAVY RAIN IS LIKELY IN SOUTHWEST
NEBRASKA AND OVER THE SANDHILLS. USING A BLEND OF
MODELS...PRECIPITATION TOTALS WEDNESDAY THROUGH THURSDAY NIGHT ARE
EXPECTED TO BE 0..60-1.15 INCH. ANTECEDENT CONDITIONS ALSO INCLUDE
3000-3500J/KG SURFACE BASED CONVECTIVE POTENTIAL BUT IT IS RELEASED
QUICKLY AS STORMS DEVELOP. AFTER THE STORMS DEVELOP...THE HODOGRAPH
APPEARS TO BECOME MORE FAVORABLE FOR ROTATION BUT THE BULK SHEAR
WILL PROBABLY TO BE INSUFFICIENT FOR A PERSISTENT UPDRAFT. THE
BOTTOM LINE IS THAT...AT THIS TIME...THE ENVIRONMENT DOES NOT APPEAR
TO FAVOR SUPERCELLS OR VERY LARGE HAIL. THE UPDRAFTS COULD BE STRONG
ENOUGH TO PRODUCE MARGINALLY LARGE HAIL. THE GFS40 SOLUTION IS
INDICATING A SIMILAR SITUATION BUT DEVELOPING THREE TO SIX HOURS
LATER.

A FAIRLY STRONG FRONT COMES ACROSS NEBRASKA FRIDAY. MOIST UNSTABLE
AIR IN PLACE AHEAD OF IT WILL RESULT IN PERIODS OF MODERATE TO HEAVY
RAIN FRIDAY AND FRIDAY NIGHT. THE INSTABILITY IS EXPECTED TO BE
SUFFICIENT FOR THUNDERSTORMS TO DEVELOP FRIDAY AND FRIDAY NIGHT.
CYCLOGENESIS ON THE FRONT WILL STOP THE SOUTHWARD PROGRESS OF THE
FRONT. THE MOISTURE TRANSPORT ON THE 300K AND 305K ISENTROPIC
SURFACES SHOWS ISENTROPIC UPGLIDE OVER A LARGE PART OF NEBRASKA
THROUGH SATURDAY NIGHT AND INTO SUNDAY.

BY SUNDAY NIGHT...THE FRONT BEGINS MOVING TO THE NORTHEAST AND
INCREASES THE POTENTIAL FOR PRECIPITATION...BUT IT IS TOO EARLY TO
TRY TO PIN THAT DOWN.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 629 PM CDT MON MAY 25 2015

AT KLBF...VFR CONDITIONS ARE FORECAST UNTIL 08Z...THEN FROM 08Z-12Z
4SM BR SCT005 OVC015...12Z-14Z 2SM BR OVC005...AFTER 14Z...MVFR
CEILINGS SHOULD BECOME VFR BY 16Z.

AT KVTN...VFR CONDITIONS UNTIL AT LEAST 06Z...THEN 5SM BR
OVC015. THERE IS THE POTENTIAL FOR LOW VSBY BELOW 1SM OVERNIGHT
AND WILL MONITOR TRENDS. MVFR CEILINGS AFTER 16Z SHOULD BECOME
VFR BY 18Z.

&&

.HYDROLOGY...
ISSUED AT 402 PM CDT MON MAY 25 2015

RECENT VERY HEAVY RAIN ACROSS NORTHEAST COLORADO...EASTERN WYOMING
AND THE PANHANDLE OF NEBRASKA IS COMBINING WITH HIGH WATER FROM ABOVE
NORMAL ROCKY MOUNTAIN SNOW MELT TO CREATE ELEVATED FLOWS ON THE
NORTH PLATTE RIVER UPSTREAM OF LAKE MCCONAUGHY...THE SOUTH PLATTE
RIVER AND THE PLATTE RIVER.

FOR THE NORTH PLATTE RIVER...INCREASED RELEASED FROM WYOMING
RESERVOIRS DUE TO THE RECENT HEAVY RAINFALL AND EXPECTED SNOW MELT
WILL RESULT IN AN SLOW INCREASE THROUGH THE END OF THE WEEK AND INTO
THE WEEKEND. AT THIS TIME THE FORECAST REMAINS A LITTLE BELOW THE
RECORD FLOODING SEEM IN 2011. ADDITIONAL RAINFALL...SOME WHICH COULD
BE HEAVY...IS POSSIBLE MID WEEK AND EARLY THIS WEEKEND. WILL NEED TO
CONTINUE TO MONITOR RELEASES UPSTREAM AND RAINFALL AMOUNTS.

FOR THE SOUTH PLATTE RIVER AND PLATTE RIVER...THE VERY HEAVY
RAINFALL ACROSS NORTHEAST COLORADO AND THE SOUTHERN PANHANDLE IS
CAUSING A SIGNIFICANT RISE IN THE RIVER. AT THIS TIME THE FORECAST
ALONG THE SOUTH PLATTE AND PLATTE RIVER CALL FOR A SECOND CREST VERY
NEAR THE CREST WHICH OCCURRED EARLIER THIS MONTH. UNFORTUNATELY
ADDITIONAL RAINFALL IS POSSIBLE THIS WEEK WHICH MAY RESULT IN EVEN
HIGHER FLOWS. SOMETHING THAT WILL BE MONITORED CLOSELY.

&&

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

$$

SYNOPSIS...MASEK
SHORT TERM...MASEK
LONG TERM...SPRINGER
AVIATION...ROBERG
HYDROLOGY...MASEK








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