Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 042320 AAA
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
620 PM CDT TUE AUG 4 2015

.SYNOPSIS...
ISSUED AT 359 PM CDT TUE AUG 4 2015

AT 20Z THE SYNOPTIC PATTERN WAS HIGHLIGHTED BY UPPER LEVEL LOWS
CENTERED OVER JAMES BAY IN SOUTHEAST CANADA AND ALONG WEST COAST
OF BRITISH COLUMBIA. AN UPPER LEVEL RIDGE WAS ESTABLISHED IN
BETWEEN THESE TWO FEATURES. A ROBUST MID-LEVEL SHORTWAVE SLOWLY
TRACKING BENEATH THE RIDGE THROUGH CENTRAL WYOMING HAS BEEN THE
MAIN PLAYER IMPACTING THE SENSIBLE WEATHER OVER THE CWA FOR MUCH
OF THE DAY. AT THE SURFACE...AN AREA OF LOW PRESSURE WAS CENTERED
IN THE EASTERN NEBRASKA PANHANDLE...WITH A DRYLINE EXTENDING
SOUTH INTO EASTERN CO...A STATIONARY TROUGH EXTENDING NORTHWARD
TOWARD THE BLACK HILLS...AND A WARM FRONT DRAPED SOUTHEAST ACROSS
FAR SOUTHWEST NEB INTO NORTHERN KANSAS. NORTH OF THE WARM FRONT
SURFACE WINDS HAVE HAD AN EASTERLY UPSLOPE COMPONENT FOR MOST OF
THE DAY...ADVECTING RICH LOW LEVEL MOISTURE INTO WESTERN NEBRASKA
WITH DEWPOINTS IN THE MID TO UPPER 60S. SHOWER AND THUNDERSTORM
ACTIVITY HAS BEEN ONGOING NORTH OF THE FRONT FOR MUCH OF THE
DAY...MAINLY IN SOUTHWEST NEBRASKA.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 359 PM CDT TUE AUG 4 2015

DEEP CONVECTION AND CLOUD COVER THROUGH THE DAY HAS MUDDLED THE
FORECAST PICTURE. HI-RES MODELS THIS MORNING ADVERTISED A
NORTHERLY PROGRESSION OF THE WARM FRONT TOWARD I-80. HOWEVER
CLOUD COVER AND COLD OUTFLOW FROM PERSISTENT THUNDERSTORM
ACTIVITY IN SOUTHWEST NEBRASKA HAS HAMPERED THIS NORTHWARD
ADVANCEMENT OF THE FRONT...AND IT HAS REMAINED STALLED NEAR THE
KANSAS BORDER FOR MOST OF THE DAY. THIS WILL KEEP THE BEST
INSTABILITY AND THE MAIN THREAT AREA FOR SEVERE WEATHER GENERALLY
SOUTH OF THE CWA THROUGH THE REMAINDER OF THE AFTERNOON AND
EVENING. WARM AIR ADVECTION ASSOCIATED WITH A STRONG LOW VEERING
WIND PROFILE NORTH OF THE SURFACE WARM FRONT WILL KEEP SCATTERED
TO WIDESPREAD THUNDERSTORM CHANCES GOING ACROSS THE CWA INTO THE
EVENING HOURS...WITH THE BEST CHANCES FROM SOUTHWEST INTO CENTRAL
NEBRASKA. ADDITIONAL DEVELOPMENT IS POSSIBLE LATER THIS AFTERNOON
IN THE VICINITY OF AN OUTFLOW BOUNDARY STALLED OVER NORTH CENTRAL
NEBRASKA WHERE MESOANALYSIS INDICATES INCREASING MOISTURE LOW
LEVEL CONVERGENCE...WITH THE HRRR MODEL RECENTLY PICKING UP ON
THIS IDEA AS WELL. STEERING FLOW ALOFT IS RATHER WEAK...SO SLOW
STORM MOTIONS WILL PROMOTE A THREAT FOR LOCALLY HEAVY RAINFALL
GIVEN PWATS AOA 1.5".

PRECIP CHANCES BEGIN TO END FROM WEST TO EAST OVERNIGHT AS MID-
LEVEL SHORTWAVE TROUGH SLOWLY KICKS EAST AND THE INSTABILITY
WANES WITH THE WEAKENING WAA REGIME JUST OFF THE SURFACE. LOW
LEVEL MOISTURE HANGS AROUND AS MAIN AREA OF LOW PRESSURE REMAINS
JUST OFF TO OUR WEST...WHICH KEEP LIGHT SOUTHEASTERLY WINDS AND
DEWPOINTS IN THE MID TO UPPER 60S IN PLACE. BOTH THE NAM/GFS SHOW
THE DEVELOPMENT OF FOG/STRATUS IN SOUTHWEST NEBRASKA LATE IN THE
OVERNIGHT INTO WEDNESDAY MORNING. POPS PUSH EAST OF THE AREA BY
NOON WEDNESDAY AND CLEARING SKIES PROGRESS EASTWARD. THIS WILL
LEAD TO HIGH TEMPERATURES RANGING FROM THE MID 80S IN NORTH
CENTRAL NEBRASKA WHERE SOME CLOUD COVER WILL HANG AROUND INTO THE
AFTERNOON HOURS...TO THE LOW 90S IN SOUTHWEST NEBRASKA WHERE MORE
SUNSHINE IS EXPECTED. LATEST NAM/EC GUIDANCE HAVE TRENDED COOLER
FOR TOMORROW AND KEEPS MORE CLOUD COVER AROUND...SO THIS TREND
WILL NEED TO MONITORED INTO TONIGHT. HAVE BEEN HESITANT TO MAKE
LARGE ADJUSTMENTS TO THE FORECAST GIVEN THE AMOUNT OF CONVECTION
THAT NEEDS TO PLAY OUT IN THE NEAR TERM.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 359 PM CDT TUE AUG 4 2015

A TROUGH WILL MOVE ACROSS SOUTHWESTERN CANADA WED NIGHT AND
SUPPRESS THE RIDGE TO THE SOUTHERN ROCKIES. AS A RESULT THE FLOW
ACROSS THE HIGH PLAINS WILL BECOME MORE ZONAL. THE TROUGH MOVES
ACROSS SOUTH CENTRAL CANADA TO END THE WEEK. AS THE TROUGH SLIDES
EAST THE SOUTHERN RIDGE WILL BUILD SLIGHTLY INTO THE CENTRAL
ROCKIES. OVER THE WEEKEND INTO NEXT WEEK AN UPPER LEVEL LOW WILL
SLOWLY PUSH TOWARDS THE PACIFIC NORTHWEST. THIS WILL CAUSE THE
RIDGE TO AMPLIFLY OVER THE ROCKIES.

LITTLE CHANGE TO THE ACTIVE WEATHER PATTERN. AS WE SHIFT FROM
NORTHWEST FLOW TO MORE ZONAL AND BACK...THE TRAIN OF SHORT WAVES
WILL CONTINUE TO PUSH ACROSS THE PLAINS. THUS THE FORECAST WILL
CONTINUE TO HAVE POPS IN NEARLY EVERY PERIOD...HOWEVER DO NOT
EXPECT A WASH OF A FORECAST. AS THE WAVES MOVE ACROSS A CHANCE FOR
STORMS WILL EXIST...ESPECIALLY FOR THE AFTERNOON NOON INTO THE
LATE EVENING HOURS.

AS FOR TEMPERATURES...SEASONAL IS THE BEST WAY TO EXPLAIN. IF
SHOWERS ARE OCCURING DURING THE PEAK HEAT...TEMPS MAY HOLD IN THE
LOWER TO MID 80S...OTHERWISE MID 80S TO LOWER 90S WILL BE COMMON.
LOWS GENERALLY IN THE 60S WITH A FEW LOCALLY COMMON COOL SPOTS TO
SEE A FEW LOWS DIP INTO THE UPPER 50S.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 620 PM CDT TUE AUG 4 2015

THE SREF...NAM AND RAP ARE GIVING A GOOD SIGNAL FOR IFR/MVFR
CIGS/VSBY DEVELOPING OVERNIGHT 09Z-18Z. NOT SURE THIS WILL AFFECT
KVTN AS THIS SITE WILL BE ON THE EDGE OF THE CLOUDS.

VFR IS EXPECTED FROM 18Z ONWARD TUESDAY.

&&

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

$$

SYNOPSIS...MARTIN
SHORT TERM...MARTIN
LONG TERM...MASEK
AVIATION...CDC



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