Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 040856
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
356 AM CDT SAT JUL 4 2015

.SYNOPSIS...
ISSUED AT 355 AM CDT SAT JUL 4 2015

UPPER RIDGE REMAINS ANCHORED ACROSS THE WRN STATES WITH AN
ANOMALOUS UPPER TROUGH MOVING SWD ACROSS WRN CANADA. FAIRLY
EXPANSIVE SMOKE ACROSS THE NRN PLAINS AND INTO THE MIDWEST FROM
FIRES FURTHER NORTH. ISOLATED TSRA HAVE DEVELOPED IN THE BLACK
HILLS IN ASSOCIATION WITH PV ANOMALY DIVING SEWD ACROSS THE NRN
HIGH PLAINS...WITH MORE WIDESPREAD MID LEVEL CLOUDINESS ACROSS
WRN SD AND WRN NEB. SOME FOG DEVELOPING IN THE EASTERN HALF OF
NEB.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 355 AM CDT SAT JUL 4 2015

DIFFICULT FORECAST TODAY AS MODELS ARE DIFFERENT IN THEIR
HANDLING OF CONVECTION INITIATION LOCATION AS WELL AS EXTENT AND
COVERAGE. ON THE LARGE SCALE...FAIRLY STRONG UPPER PV ANOMALY IS
PROGGED BY MOST MODELS TO CONTINUE ITS SEWD TRACK ACROSS SD AND
INTO THE MISSOURI VALLEY BY THE END OF THE DAY. GOOD HEIGHT FALLS
ASSOCIATED WITH THIS SHORT WAVE WITH WEAK HEIGHT RISES BEHIND AS
WRN STATES RIDGE FLATTENS AND MORE SIGNIFICANT LONG WAVE TROUGH
APPROACHES THE NRN PLAINS FROM CANADA. LEE SFC TROUGH DEVELOPS
OVER WRN NEB/SD AND INTO NERN CO AS A MORE WRLY FLOW ALOFT
DEVELOPS AND IS THE KEY TO THE DEVELOPMENT OF CONVECTIVE
INITIATION...OR NOT. SHORT RANGE MODELS ARE TRENDING TWD A MORE
CONVERGENT BOUNDARY BY LATE AFTERNOON DESPITE BEING ON THE BACK
SIDE OF THE MORE SIGNIFICANT PV ANOMALY. WILL SIDE WITH THE IDEA
THAT AS THIS SFC TROUGH DEVELOPS SRLY FLOW IN RESPONSE TO THE
EAST OF THE DEVELOPING TROUGH WILL ALLOW LOW TO MID 60S DEW
POINTS TO MOVE NWD WHICH WILL ALLOW A LOW LEVEL THETA-E GRADIENT
TO DEVELOP...SUFFICIENT FOR THE LOW LEVEL CONVERGENCE AND
ASSOCIATED CONVECTIVE INIT TO OCCUR. WHERE THIS HAPPENS IS WHERE
MODELS STRUGGLE TO AGREE ON. RUC SEEMS TO BE KEYING IN ON AN AREA
FROM CENTRAL SD SWD INTO NWRN NEB. WHAT MODELS DO AGREE ON IS
THAT IF CONVECTION DOES DEVELOP THERE IS A SUFFICIENT CAPE-SHEAR
BALANCE TO SUPPORT SUPERCELLS AS THE INITIAL CONVECTIVE MODE. IN
FACT...CONVECTION ALLOWING MODELS THAT DO DEVELOP CONVECTIVE INIT
SHOW THIS AND RESULTANT OUTFLOW BOUNDARIES DEVELOP FURTHER
CONVECTION SWWD INTO NEB. RIGHT MOVING SUPERCELLS ARE PROGGED TO
MOVE SLOWLY AND SWWD AS WELL. CONFIDENCE IS AVERAGE ON STORMS
ACTUALLY DEVELOPING BY MID TO LATE AFTERNOON...BUT CONFIDENCE IS
LOW ON WHERE AND TO WHAT EXTENT. ANY STORMS THAT DO FORM WILL
HAVE THE POTENTIAL TO BE SEVERE BASED ON THE REASONING ABOVE.

TEMPS TODAY WILL BE NEAR OR SLIGHTLY ABOVE AVE FOR THIS TIME OF
YEAR WITH SRLY WINDS INCREASING THROUGH THE DAY EAST OF THE NEB
PANHANDLE.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 355 AM CDT SAT JUL 4 2015

THE PERSISTENT WESTERN RIDGE WITH NORTHWEST FLOW OVER THE HIGH
PLAINS THE PAST WEEK OR SO WILL FINALLY MAKE A CHANGE DURING THE
LONG TERM. SUNDAY THE UPPER LEVEL RIDGE WILL BEGIN TO FLATTEN AS
A TROUGH DIGS ACROSS THE PLAINS OF CANADA INTO THE NORTHERN
ROCKIES. MEANWHILE A STRONG SFC COLD FRONT WILL PUSH SE ACROSS
THE NORTHERN/CENTRAL PLAINS.

AHEAD OF THE FRONT ON SUNDAY TEMPS STILL ON THE WARM SIDE...UPPER
80S TO MID 90S. THE FRONT WILL BEGIN TO WORK INTO FAR NORTHWEST
CWA DURING THE LATE MORNING HOURS OR EARLY AFTERNOON...THEN
SLOWLY PROGRESS SE THROUGH DAY AND INTO THE OVERNIGHT PERIOD. DEW
PTS CLIMB WELL INTO THE 60S AND MAYBE A FEW AROUND 70 DEGREES
AHEAD OF THE FRONT. THIS CORRELATES TO GOOD MOISTURE THROUGH THE
COLUMN AS PWATS ABOVE 1.75 INCHES AND COULD SURPASS 2 INCHES
WITHIN THE SHOWERS. MODELS IN VERY GOOD AGREEMENT WITH GOOD LIFT
WITH THE FRONTAL PASSAGE AND CONTINUED THE 60 OR HIGHER POPS.
WILL HAVE TO MONITOR THE SLOW MOVING STORMS AS LOCALLY HEAVY
RAINFALL IS POSSIBLE...1.50 INCHES OR MORE.

IN THE WAKE OF THE FRONT COOLER TEMPS AND SUBSIDENCE RESULTING IN
DRY CONDITIONS AND TEMPS ONLY IN THE 70S ON MONDAY AND SIMILAR TO
A COUPLE DEGREES WARMER FOR TUESDAY AS HIGH PRESSURE DRIFTS
ACROSS THE NORTHERN PLAINS. THE HIGH PRESSURE WILL DRIFT EAST
TOWARDS THE MID MISS RVR VALLEY TUESDAY AFTERNOON INTO WEDNESDAY
AND BEGIN A RETURN SOUTHERLY SFC FLOW OVER AREA. MODELS FAVOR
DEVELOPMENT OF STORMS OVER THE FRONT RANGE...THEN WITH MORE MID
LEVEL WESTERLY FLOW...IT SHOULD DRIFT TOWARDS THE CWA. COVER
STILL IN QUESTION AS UPPER SUPPORT IS MARGINAL AND STORMS MAY DIE
AS THE MOVE INTO THE LOWER ELEVATIONS.

ACTIVE PATTERN SETS UP FOR THE REST OF THE WEEK WITH FLOW TO
PRIMARILY TO BE ZONAL. DIURNAL DEVELOPMENT OVER THE HIGHER
TERRAIN THE EASTERLY MOVEMENT WILL BRING THEM OVERHEAD. RIDGE
DOES BUILD A LITTLE AND THIS WILL WARM TEMPS UP A FEW MORE
DEGREES...CLOSER TO SEASONAL MID AND UPPER 80S BY THE END OF THE
WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1146 PM CDT FRI JUL 3 2015

THE LACK OF CONVECTION ACROSS NERN WYOMING AND SERN MONTANA WAS
NOT HANDLED BY THE NAM AND GFS SOLNS TONIGHT AS THEY WERE
INDICATING QPF WHICH SHOULD BE ONGOING ATTM. WV IMAGERY CURRENTLY
IS INDICATING A WEAK SHORTWAVE OVER CENTRAL MT...WHICH IS
EXPECTED TO LIFT EAST INTO NORTH DAKOTA AN THE NORTHERN HALF OF
SD OVERNIGHT. WITH THE LACK OF DECENT FORCING TONIGHT...HAVE
OPTED FOR A CLOUD FREE FORECAST FOR BOTH THE KLBF AND KVTN
TERMINALS OVERNIGHT. HAZE ALOFT WILL CONTINUE TO BE A CONCERN
OVER THE NEXT 24 HOURS...AS SMOKE FROM FIRES IN
CANADA...CONTINUES TO PUSH SOUTH INTO THE CENTRAL AND NRN PLAINS.
BY AFTERNOON...HIGH CLOUDS WILL BEGIN TO PUSH INTO THE REGION IN
ADVANCE OF A WEAK UPPER LEVEL DISTURBANCE. THIS DISTURBANCE MAY
LEAD TO THE DEVELOPMENT OF THUNDERSTORMS DURING THE EVENING HOURS
ON SATURDAY. HOWEVER...WITH LITTLE OR NO SURFACE FOCUS FOR
DEVELOPMENT LATE SAT AFTN/EVE...PINPOINTING WHERE AND IF
CONVECTION DEVELOPS IS VERY DIFFICULT AT BEST. WITH THIS IN
MIND...WILL HANDLE THE TSRA MENTION WITH A VCTS GROUP FOR BOTH
TERMINALS AND CONFINE THIS TO THE EARLY EVENING HOURS WHEN
LOW/MID LEVEL INSTABILITY AND LAPSE RATES ARE THE GREATEST.


&&

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

&&

$$

SYNOPSIS...JWS
SHORT TERM...JWS
LONG TERM...MASEK
AVIATION...CLB




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