Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 240434 AAB
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1134 PM CDT SAT MAY 23 2015

.SYNOPSIS...
ISSUED AT 340 PM CDT SAT MAY 23 2015

UPPER LEVEL CLOSED LOW ROTATING ACROSS THE FOUR CORNERS REGION THIS
AFTERNOON. SOUTHERLY/SOUTHEASTERLY MOIST WINDS HAVE HELD TEMPS DOWN
ACROSS THE AREA MOST OF THE DAY...WITH REPORTS GENERALLY IN THE 50S.
HOWEVER SOUTHWEST NEB STARTING TO SEE A LITTLE DRY AIR ALOFT WORK
INTO THE REGION AND EVEN SOME PEAKS OF SUN. SHOULD HELP TEMPS GET
INTO THE LOWER 60S.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 340 PM CDT SAT MAY 23 2015

COMPLEX WEATHER EXPECTED TONIGHT. FIRST OFF...WITH SOME CLEARING
ACROSS SW NEB AND THUNDERSTORMS FIRING OVER COLORADO...COULD SEE
SOME STRONG THUNDERSTORMS LIFT INTO THE REGION. PRIMARILY THINK THE
STORMS WILL REMAIN CLOSER TO THE LOW...TO THE WEST OF THE
CWA...HOWEVER A FEW STRAY STORMS MAY IMPACT SW NEB INTO THE SE
PANHANDLE. SECOND WILL BE THE CHANCE FOR SHOWERS AS A MID LEVEL WAVE
ROTATES AROUND THE MAIN LOW...AND ACROSS THE AREA. MARGINAL
ISENTROPIC LIFT AT THE 300K AND 305K SURFACE HOWEVER PRESS DEF 20MB
OR LESS. SHOULD GET SOME ISOLATED TO SCATTERED SHOWERS. LIFT INDEX
VALUES AROUND ZERO AND ONLY A COUPLE HUNDRED J/KG OF CAPE AT
BEST...SO MAINLY SHOWERS BUT COULD ALSO SEE A FEW WITH THUNDER.
FINALLY ACROSS THE NORTHERN HALF OF THE CWA LOW STRATUS WITH AREAS
OF FOG AND DRIZZLE WILL LIKELY PERSIST WITH THE EASTERLY UPSLOPE
FLOW WINDS CONTINUING. AS THE UPPER LEVEL SUPPORT BRINGS
SHOWERS...THE CIGS/FOG WILL LIFT...HOWEVER AS THE RAIN ENDS A RETURN
TO THE LOW CONDITIONS ARE LIKELY. TEMPS WITH SEE LITTLE MOVEMENT
OVERNIGHT AS MOST AREAS NEAR SATURATION ALREADY.

TOMORROW THE UPPER LOW WILL LIFT TO THE WESTERN HIGH PLAINS. MORNING
WILL CONTINUE TO SEE THE STRATUS/FOG/DRIZZLE/LIGHT SHOWERS AND MAYBE
A RUMBLE OF THUNDER HERE OR THERE. BY THE AFTERNOON A DRY SLOT WILL
WRAP INTO THE LOW AND THIN CLOUDS. THIS SHOULD HELP ALLOW TEMPS TO
WARM INTO THE 60S WITH AROUND 70 IN THE SOUTH AND FAR EAST. THIS
WILL ALSO BRING A LITTLE AFTERNOON SFC INSTABILITY. SPC CURRENTLY
HAS A MARGINAL RISK FOR SEVERE WEATHER. MODELS DEVELOP 1500 TO 2000
J/KG OF CAPE HOWEVER 0-6KM SHEAR IS 25 TO 30 KTS AND HELICITY OF
AROUND 100 M2/S2 OR LESS. HAIL LOOKS TO BE THE MAIN THREAT ALTHOUGH
IF A CLEARING POCKET DEVELOPS...TEMPS WOULD GET A QUICK BOOST UP AND
SEVERE THREAT WOULD INCREASE. WILL CONTINUE TO MONITOR.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 340 PM CDT SAT MAY 23 2015

STRONG INSTABILITY CONTINUES INTO THE EVENING BUT THE SHEAR IS WEAK
AND...WITH PRECIPITABLE WATER AT OR ABOVE 1.00 INCH...HEAVY RAIN
BECOMES THE PRIMARY THREAT SUNDAY NIGHT. ON MONDAY...COOLER DRIER
AIR COMES INTO WESTERN NEBRASKA AND THE CHANCES OF THUNDERSTORMS
SHIFT TO CENTRAL AND EASTERN NEBRASKA. HOWEVER...AS THE LOW MOVES
NORTHEASTWARD ACROSS WESTERN NEBRASKA...FRONTOGENESIS CONTINUES THE
PRECIPITATION INTO THE EVENING. THE GFS40 AND THE GEMNH SOLUTIONS
ARE SIMILAR...THOUGH THEY ARE A LITTLE SLOWER AS INDICATED BY THE
SLIGHTLY MORE NEGATIVE TILT TO THE UPPER TROUGH.

AFTER MONDAY NIGHT...THE MEDIUM RANGE MODELS DEVIATE SIGNIFICANTLY.
THE NAM12 SHOWS THE UPPER TROUGH PIVOTING ON THROUGH THE AREA AND
DRY WEATHER RESULTING. THE GEMNH IS SIMILAR TO THE NAM12 BUT THE
GFS40 HAS A SECOND TROUGH PIVOTING THROUGH TUESDAY AFTERNOON WITH
ENOUGH INSTABILITY FOR THUNDERSTORMS TO DEVELOP. SINCE TWO OF THE
THREE INDICATE DRY WEATHER...WE WILL SKEW THE FORECAST IN THAT
DIRECTION.

SOUTH FLOW ON THE HIGH PLAINS WILL HELP KEEP THE THETA-E RIDGE OVER
WESTERN NEBRASKA THROUGH THURSDAY NIGHT WHEN A FRONT FORCES IT
SOUTH. THE FRONT THEN STALLS ACROSS KANSAS. IN THE MEANTIME...THE
PRESENCE OF A SURFACE BOUNDARY IN THE THETA-E GRADIENT WILL BRING
CHANCES OF THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING AND AGAIN
THURSDAY AFTERNOON AND EVENING. FOR WEDNESDAY EVENING...THE
SURFACE-BASED CONVECTIVE POTENTIAL ENERGY INCREASES TO MORE THAN
2000J/KG WITH 0-6KM BULK SHEAR OF 20-30KT WHICH DOES ALLOW POTENTIAL
FOR LARGE HAIL. FRIDAY LOOKS TO BE MORE FAVORABLE FOR SEVERE WEATHER
IN CENTRAL AND NORTH CENTRAL NEBRASKA WITH SURFACE-BASED CONVECTIVE
POTENTIAL ENERGY OF 3000-4000J/KG AND 0-6KM BULK SHEAR OF 25-35KT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1134 PM CDT SAT MAY 23 2015

IFR/LIFR CIGS AND VSBY OVERNIGHT SHOULD IMPROVE TO VFR/MVFR SUNDAY
BY 18Z. ISOLATED TO SCATTERED SHOWER AND THUNDERSTORM ACTIVITY
WOULD LIKELY DEVELOP 20-24Z SUNDAY AFTN...MAINLY WEST OF HIGHWAY
83. THE NAM AND SREF SUGGEST ISOLATED SHOWER AND THUNDERSTORM
ACTIVITY IS POSSIBLE SUNDAY EVENING.

OVERNIGHT...A 700MB WARM FRONT LIFTS NORTH THROUGH THE FCST AREA.
WIDESPREAD CONVECTION ACROSS THE SOUTHERN PLAINS IS LIMITING STORM
COVERAGE ACROSS NEBRASKA. STILL...ISOLATED TSTM ACTIVITY
OVERNIGHT IS POSSIBLE...MAINLY WEST OF HIGHWAY 61...OTHERWISE
LIGHT RAIN...DRIZZLE AND SHOWERS PREVAIL.

&&

.HYDROLOGY...
ISSUED AT 340 PM CDT SAT MAY 23 2015

THE SOUTH PLATTE RIVER IS HOLDING STEADY OR SLIGHTLY FALLING...AND
WILL CONTINUE TO DO SO OVER THE NEXT COUPLE OF DAYS. STILL AMPLE
SNOW MELT WHICH WILL CONTINUE TO RESULT IN ELEVATED FLOWS INTO JUNE.
ALSO GOING TO ADD SOME WATER AS THUNDERSTORMS WITH LOCALLY HEAVY
RAINFALL MOVE ACROSS NORTHEAST COLORADO AND THE SOUTHWESTERN
NEBRASKA PANHANDLE TONIGHT. THIS WILL BE MONITORED CLOSELY AS THIS
AREA IS BECOMING MORE SATURATED AND COULD SEE MORE RUNOFF...WHICH
ENDS UP IN THE SOUTH PLATTE RIVER. AT THIS TIME A SECOND RISE IS
ANTICIPATED TO MOVE DOWN THE RIVER FROM MID WEEK THROUGH THE
WEEKEND. THIS CREST IS EXPECTED TO BE BELOW THE FIRST
CREST...HOWEVER WITH RAIN CHANCES OVER THE NEXT COUPLE OF DAYS AND
AGAIN DURING THE WEEK...THE SECOND CREST HEIGHT IS NOT A CERTAINTY.
ANYONE ALONG THE SOUTH PLATTE RIVER WILL NEED TO CONTINUE TO MONITOR
THE LATEST FORECAST.

&&

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

$$

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






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