Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 280423 AAB
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1123 PM CDT WED MAY 27 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 309 PM CDT WED MAY 27 2015

ISOLATED TO WIDELY SCATTERED TSRA ONGOING IN THE SW NEB PANHANDLE
NEAR WY BORDER AND ALSO IN NERN CO. THOSE IN THE NEB PANHANDLE ARE
MORE ORGANIZED ALONG AN OUTFLOW BOUNDARY FROM EARLIER CONVECTION IN
SERN WY. ISOLD WEAKER CONVECTION NOTED IN THE NRN PANHANDLE. FURTHER
SOUTH IN NERN CO IS WHERE MORE ROBUST CONVECTION IS AND BASED ON SPC
MESOANALYSIS HAS THE BEST POTENTIAL FOR FURTHER DEVELOPMENT THROUGH
THE AFTERNOON AND EVE. DISCRETE SUPERCELL IN NERN CO IS MOVING
SLOWLY AND APPEARS TO BE LOCATED ALONG WARM FRONT WHICH IS SLOWLY
MOVING NWD. NERN CO STORM IS ASSISTED BY WEAK PV ANOMALY BUT IN THE
AREA OF 3K SFC BASED CAPE VALUES AND ALONG LOW LEVEL LAPSE RATE
GRADIENT. FURTHER DEVELOPMENT IS ALSO INCREASING ALONG BOUNDARY
FURTHER SOUTHWEST INTO CO...AND MORE STORMS DEVELOPING ALONG WARM
FRONT IN KS. SHORT RANGE MODELS AND OTHER CAMS AND INCLUDING CAPS 20
MEMBER ENSEMBLE SUGGEST THESE TWO AREAS WILL CONTINUE TO PROGRESS
EWD AND WILL AFFECT THE WRN CAW THIS EVENING...THOUGH MOST SUGGEST A
WEAKENING TREND WITH THE STORMS THAT MOVE OUT OF THE PANHANDLE...AND
THE MORE ROBUST STORMS IN NERN CO SHOULD MOVE INTO NWRN KS AND BE
REINFORCED BY A DEVELOPING LLJ THIS EVENING...WHICH WOULD MEAN
PROPAGATION VECTORS SHOULD BECOME MORE SERLY ORIENTED. MOISTURE HAS
BEEN POOLING ALONG AND NORTH OF THE WARM FRONT IN KS...AND KLBF HAS
GOTTEN TO 56 CURRENTLY.

ALTHOUGH STRATUS DEVELOPMENT IS POSSIBLE OVERNIGHT...PROJECTED
CLEARING BY LATE MORNING...ESPECIALLY IN SWRN NEB...SHOULD ALLOW FOR
ENOUGH TIME FOR DESTABILIZATION OF THE ATMOSPHERE AHEAD OF A MORE
ROBUST PV ANOMALY WHICH IS PROGGED TO MOVE INTO THE HIGH PLAINS BY
LATER AFTERNOON. AS THIS UPPER FORCING ENHANCES THE LIFT ALONG THE
LOW LEVEL THETA GRADIENT THAT DEVELOPS THROUGH THE DAY OVER WRN KS
AND INTO WRN NEBR...ADDITIONAL THUNDERSTORM DEVELOPMENT IS LIKELY BY
AFTERNOON. GFS MUCH QUICKER WITH ITS PREFRONTAL TROF POSITION BY
AFTERNOON AND THEREFORE DEVELOPS CONVECTIVE COMPLEXES MUCH FURTHER E
INTO CENTRAL AND NERN NEB BY THU AFTERNOON. THE NAM ON THE OTHER
HAND SUGGESTS DEVELOPMENT IN NWRN KS AND MOVING INTO CENTRAL NEBR
DURING THE EVENING. AT ANY RATE THUNDERSTORM COVERAGE SHOULD BE
GREATER FOR THE AREA TMRW...AND INTENSITY OF CONVECTION SHOULD ALSO
BE GREATER WITH THE INCREASING LOW LEVEL MOISTURE AND EVENTUAL CAPE
BY AFTERNOON. HEAVY RAIN IS ALSO POSSIBLE WITH PW VALUES INCREASING
TO OVER AN INCH.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 309 PM CDT WED MAY 27 2015

FOR THURSDAY NIGHT...PROJECTION OF THE LOW LEVEL WIND AND THETA-E
INDICATES THAT WEAK SPEED CONVERGENCE AND WARM ADVECTION IN THE
0-2KM THETA-E GRADIENT WILL CONTINUE LIFTING MOIST UNSTABLE AIR OVER
SOUTH CENTRAL AND SOUTHWEST NEBRASKA AND...TO A LESSER EXTENT...
NORTH CENTRAL NEBRASKA AND THE SANDHILLS. THE STRONG CONVECTIVE
POTENTIAL AND MORE FAVORABLE 0-6KM BULK SHEAR IS LIKELY TO BE
CONFINED TO THE SOUTHERN TWO TIERS OF NEBRASKA ZONES. HOWEVER...IT
SEEMS THAT...OVER THE LAST WEEK OR SO ANYWAY...THE LOCAL AREA HAS
HAD MARGINALLY LARGE HAIL WITH BULK SHEAR SEEMINGLY NOT FAVORABLE.
AT TIMES...STRONG CONVECTIVE POTENTIAL WITH 15-25KT BULK SHEAR HAS
BEEN SUFFICIENT FOR PRODUCING 1 INCH HAIL. THE PROJECTED SCENARIO
THURSDAY EVENING SHOWS A NARROW FINGER OF SURFACE-BASED CONVECTIVE
POTENTIAL OF 2500-3500J/KG EXTENDING OVER THE NEBRASKA SANDHILLS AND
2000-3000J/KG 800MB BASED POTENTIAL WITH 15-25KT BULK SHEAR IN THE
0-6KM LAYER...BUT THE HODOGRAPH AND STORM RELATIVE HELICITY DOES NOT
APPEAR TO BE FAVORABLE FOR ROTATING UPDRAFTS. THEREFORE...THOUGH
THERE ARE MARGINALLY FAVORABLE CONDITIONS FOR SEVERE WEATHER...WE
WILL NOT INCLUDE THE WORDING FOR SEVERE AT THIS TIME.

A SURFACE BOUNDARY AND UPPER TROUGH COME ACROSS NEBRASKA FRIDAY WITH
875MB BASED LIFTED INDICES OF 0C TO -2C AHEAD OF IT. THIS WILL BRING
THE LIKELIHOOD OF SIGNIFICANT RAINFALL THROUGH FRIDAY EVENING AND
THE POSSIBILITY OF THUNDERSTORMS.

AFTER FRIDAY NIGHT...AN UPPER RIDGE BUILDS IN THE WEST AND THE
SURFACE BOUNDARY IS PUSHED AGAINST THE ROCKIES. THIS WILL BRING A
REPRIEVE IN THE RAINFALL FOR MOST OF THE WEEKEND.

AS THE HIGH MOVES OFF TOWARD THE GREAT LAKES AND MISSISSIPPI VALLEY
SUNDAY...RETURN FLOW WILL BEGIN BRINGING MOISTURE ONTO THE HIGH
PLAINS FROM THE SOUTHWEST. INSTABILITY...PRECIPITABLE WATER AND LOW
LEVEL THETA-E THEN INCREASE AGAIN AS GULF MOISTURE TRACES A SOMEWHAT
CIRCUITOUS TRAJECTORY FROM TEXAS ONTO THE HIGH PLAINS WITH A MORE
DIRECT TRAJECTORY DEVELOPING BY MONDAY AFTERNOON. THEN...AS THE
SURFACE BOUNDARY BECOMES BETTER DEVELOPED WITH A SHARP THETA-E
GRADIENT...A MENTION OF PRECIPITATION IS AGAIN APPROPRIATE POSSIBLY
AS EARLY AS MONDAY OR TUESDAY WITH BETTER CHANCES TUESDAY NIGHT OR
WEDNESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1123 PM CDT WED MAY 27 2015

THE RAP AND NAM MODELS CONTINUE TO FORECAST STRATUS DEVELOPING
ACROSS SWRN NEB AROUND 06Z WHICH WOULD SPREAD NORTH TO KLBF AND
KVTN. IFR/MVFR CIGS ARE EXPECTED BY 09Z. GIVEN THE EXPECTED
INCREASE IN MOISTURE BELOW 700MB...THESE CLOUDS WOULD BE SLOW TO
MIX OUT THURSDAY MORNING. THUS VFR/MVFR IS EXPECTED 18Z-20Z.

TSTM CHANCES THURSDAY SHOULD COMMENCE ACROSS THE PANHANDLE AROUND
21Z WHICH SPREAD SLOWLY EAST INTO NCNTL NEB THURSDAY EVENING.

LASTLY...STORM ACTIVITY IS UNDERWAY ACROSS THE PANHANDLE AT 04Z.
THESE STORMS ARE EXPECTED TO MOVE EAST AND BECOME ISOLATED
OVERNIGHT.

&&

.HYDROLOGY...
ISSUED AT 309 PM CDT WED MAY 27 2015

NORTH PLATTE RIVER SLOWLY COMING UP AT LISCO AND LEWELLEN WITH
UPSTREAM RELEASES AND RAINFALL OF THE LAST FEW DAYS. FCST CREST
HEIGHT FOR LISCO IS HALF A FOOT LOWER WITH THIS MORNINGS FCST BASED
ON LESSER AMOUNTS OF WATER DUE TO RELEASES UPSTREAM...BUT
UNCERTAINTIES EXIST. PLEASE SEE FLOOD STATEMENTS PERTAINING TO THE
NORTH PLATTE RIVER AT LISCO AND LEWELLEN FOR FURTHER DETAILS.

THE SOUTH PLATTE RIVER CONTINUES ITS RISE FROM ROSCOE TO NORTH
PLATTE AND WILL CONTINUE TO DO SO THROUGH FRIDAY. THESE RISES DUE TO
RAINFALL OVER THE BASIN IN NORTHEAST COLORADO RECENTLY...PAIRED WITH
THE CONTINUED SNOW MELT IN THE ROCKIES. THE JULESBURG GAGE IS
SHOWING THE CREST HAS LIKELY PASSED THERE. ADDITIONAL
RAINFALL...SOME WHICH COULD BE HEAVY...IS POSSIBLE THURSDAY AND
THURSDAY NIGHT IN THE BASIN. CHECK WITH LATEST WARNING INFORMATION
FOR CRESTS AND TIMES.

&&

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

$$

SHORT TERM...JWS
LONG TERM...SPRINGER
AVIATION...CDC
HYDROLOGY...JWS






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