Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 192001
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
301 PM CDT SAT JUL 19 2014

.SYNOPSIS...
ISSUED AT 300 PM CDT SAT JUL 19 2014

A STRONG UPPER LEVEL RIDGE OF SUBTROPICAL HIGH PRESSURE
CENTERED OVER THE SOUTHWEST WILL MODULATE THE WEATHER FOR THE NEXT 7
DAYS AS IT MOVES EAST AND WEST ACROSS THE SOUTH. RAIN CHANCES ARE
ISOLATED AT BEST AND COLD FRONTS WILL BE WEAK PRESENTING MOSTLY
ABOVE NORMAL TEMPERATURES FOR THE NEXT 7 DAYS.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 300 PM CDT SAT JUL 19 2014

FORECAST CONCERNS THROUGH SUNDAY INCLUDE THUNDERSTORM CHANCES
TONIGHT AS WELL AS HIGH TEMPERATURES AND HEAT INDICES ON SUNDAY
AFTERNOON.

AT 19Z WATER VAPOR IMAGERY SHOWED TROUGHING OVER THE EASTERN CONUS
WITH A BROAD RIDGE CENTERED OVER THE DESERT SOUTHWEST. SEVERAL
SHORTWAVES WERE EMBEDDED IN THE FLOW MOVING OVER THE RIDGE FROM THE
PACIFIC NORTHWEST INTO THE CENTRAL PLAINS. AT THE SURFACE...HIGH
PRESSURE REMAINED OVER MUCH OF THE EASTERN PART OF THE COUNTRY AND
WITH A TROUGH OF LOW PRESSURE FROM THE IDAHO INTO THE SOUTHERN
PLAINS...SOUTHERLY FLOW PERSISTS INTO THE CENTRAL PLAINS. ASIDE FROM
CLOUDS ASSOCIATED WITH THE NORTH CENTRAL NEBRASKA CONVECTION...SKIES
OVER THE LOCAL AREA WERE MOSTLY SUNNY AS LAPS SOUNDINGS SHOWED THE
ENTIRE AREA STILL CAPPED.

FOR TONIGHT...IF CONVECTION DEVELOPS OVER THE PANHANDLE AND WESTERN
SANDHILLS YET THIS AFTERNOON COULD GET SOME ACTIVITY TO SLIDE
EASTWARD THIS EVENING AS THERE WILL BE SUFFICIENT INSTABILITY ACROSS
THE FORECAST AREA FOR STORMS TO WORK WITH. THE CONCERN WITH HOW LONG
ANY ACTIVITY WILL CONTINUE IS THAT THERE LOOKS TO BE A LACK IN
FORCING AS THERE ISN/T A STRONG SHORTWAVE MOVING THROUGH AND THE LOW
LEVEL JET WILL STRENGTHEN THIS EVENING BUT PRIMARY FOCUS WILL BE TO
THE NORTH OVER SOUTH DAKOTA SO NOT EXPECTED MUCH FOR ENHANCED LIFT
ASSOCIATED WITH THAT FORCING. ALSO...MOISTURE IS LACKING ACROSS THE
AREA SO THINKING THAT ANY ACTIVITY WILL BE MORE ISOLATED IN NATURE.
THE NAM AND THE RAP BOTH INDICATE A VERY WEAK SHORTWAVE TROUGH
MOVING ACROSS NEBRASKA TONIGHT...BUT NEITHER PRODUCE ANY CONVECTION.
THE GFS ON THE OTHER HAND AFTER BEING DRY THROUGH THE
EVENING...SHOWS SOME CONVECTION OVER EASTERN NEBRASKA AFTER 06Z.
BIAS WOULD BE TO KEEP THE FORECAST DRY FOR LATE EVENING AND
BEYOND...HOWEVER MODELS DID POORLY WITH THE CURRENT CONVECTION OVER
NORTHERN NEBRASKA. SO...WITH THE INSTABILITY IN PLACE AND VERY STEEP
LAPSE RATES IN THE MID LEVELS WILL PUT AN ISOLATED MENTION IN THE
FORECAST FOR LATE TONIGHT.

FOR SUNDAY...THE UPPER LEVEL RIDGE BUILDS EAST BRINGING WARMER AIR
ALOFT INTO THE CENTRAL PLAINS. AT 700MB...TEMPERATURES ACROSS THE
FORECAST AREA INCREASE TO 15-17C BY 00Z MONDAY WHEREAS RAOB DATA
FROM THIS MORNING /19.12Z/ SHOWED TEMPERATURES AT 700MB AT 10-12C.
WITH DRY AIR ACROSS THE AREA SHOULD HAVE PLENTIFUL SUNSHINE SO
EXPECTING TEMPERATURES TO WARM EFFICIENTLY. STATISTICAL GUIDANCE
GIVES HIGHS FOR PORTIONS OF THE AREA AT OR ABOVE 100 DEGREES ACROSS
MUCH OF THE FORECAST AREA. THE CONCERN WITH REACHING THESE LEVELS OF
HEAT WILL BE THE MOISTURE IN THE LOW LEVELS. MODELS ARE CONTINUING
TO KEEP DEWPOINTS IN THE 50S AND 60S MOST AREAS WHICH WON/T HELP THE
TEMPERATURES TO REACH THOSE LEVELS. BUT...SOUNDINGS ARE INDICATING
FULL MIXING WOULD BRING HIGHS TO 105 IN PLACES. THINK THIS IS TOO
HIGH AND WHEN LOOKING AT SREF PLUMES THE MAJORITY OF THE MODEL
SOLUTIONS ARE BELOW THE CENTURY MARK. KEPT THE FORECAST VERY SIMILAR
TO THE PREVIOUS SO KEPT HIGHS FOR MOST AREAS FROM THE MID 90S TO
AROUND 100 DEGREES. HEAT INDEX VALUES WILL BE A CONCERN AS
WELL...MAINLY IN AREAS EAST OF A KIML TO KLBF TO KANW LINE. THESE
ARE THE LOCATIONS THAT WILL SEE THE COMBINATION OF THE HIGHER
TEMPERATURES AND HIGHER DEWPOINTS. TO THE WEST OF THIS LINE DRIER
AIR IS EXPECTED TO MIX DOWN WHICH COULD ACTUALLY BRING RELATIVE
HUMIDITY DOWN NEAR 15 PERCENT. HELD OFF ON ANY MENTION OF HEAT
ADVISORY DUE TO VALUES BEING RIGHT AT THE THRESHOLD OF 100 DEGREES
ALONG WITH SOME UNCERTAINTY IN REACHING THESE VALUES.

AS MENTIONED SOME PLACES MAY SEE RELATIVE HUMIDITY DROP NEAR 15
PERCENT OVER PORTIONS OF THE PANHANDLE AND WESTERN SANDHILLS.
DESPITE THE HOT AND DRY CONDITIONS...DON/T ANTICIPATE FIRE DANGER
GETTING TO A CRITICAL LEVEL AS WINDS ARE NOT EXPECTED TO BE STRONG
IN THE AFTERNOON.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 300 PM CDT SAT JUL 19 2014

SUNDAY NIGHT THROUGH TUESDAY...THE DRYLINE SURGE SUNDAY CONTINUES
MONDAY. A SLIGHT RETREAT IS EXPECTED SUNDAY NIGHT BUT LOW PRESSURE
DEEPENING ACROSS SD MONDAY SHOULD MOVE IT BACK EAST OF HIGHWAY 83.
AT THE SAME TIME...A SUBTROPICAL DISTURBANCE ACROSS SRN CA THIS AFTN
WILL LIFT NORTHEAST THROUGH THE FCST AREA MONDAY SETTING UP THE
POTENTIAL FOR ISOLATED HIGH BASED TSTMS IN THE AFTN OR AT NIGHT
AFFECTING AREAS EAST OF HIGHWAY 83. MOISTURE WITH THE STORMS WILL BE
LIMITED AND OPERATE ABOVE 700 MB.

HEAT AND MOISTURE AHEAD OF THE DRYLINE MAY PRODUCE HEAT ADVISORY
CONDITIONS MONDAY ALONG AND EAST OF HIGHWAY 183 WITH HIGHS 95 TO 100
AND HEAT INDICES 100 TO 105.

THE UPPER LEVEL DISTURBANCE DEEPENS ACROSS THE MIDWEST MONDAY NIGHT
AND SENDS A WEAK COLD FRONT THROUGH THE FCST AREA TUESDAY FOR HIGHS
90 TO 95. THE FRONT UNDERCUTS THE UPPER LEVEL RIDGE AND THE
ATMOSPHERE REMAINS CAPPED AND DRY TUESDAY.

TUESDAY NIGHT THROUGH SATURDAY...CANADIAN HIGH PRESSURE BACKS IN AND
THE SUBTROPICAL HIGH RETREATS WEST. THIS SHOULD SET UP A STATIONARY
FRONT ACROSS WRN NEB WITH LOW PRESSURE ACROSS THE NRN HIGH PLAINS. A
DEEP UPPER LEVEL LOW WILL MOVE ASHORE ACROSS THE PACIFIC NORTHWEST
AND THIS ANCHORS THE LOW ACROSS THE HIGH PLAINS AND DRAWS COOLER AIR
WEST THROUGH THE FCST AREA. IN TIME A PACIFIC COLD FRONT WILL SWEEP
THE FCST AREA ALONG ABOUT FRIDAY AS THE UPPER LOW MOVES INTO CNTL
CANADA.

THERE ARE SOME ISOLATED POPS IN THE FORECAST BUT THE SIGNAL THE
MODELS GIVE IS DRY OWING TO WARM AIR ALOFT EFFECTIVELY CAPPING
CONVECTION ACROSS THE FCST AREA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 106 PM CDT SAT JUL 19 2014

ONGOING CONVECTION OVER NORTH CENTRAL NEBRASKA WILL CONTINUE TO
MOVE EAST THROUGH THE AFTERNOON. THIS WILL KEEP SOME SHOWERS AND
POTENTIALLY A THUNDERSTORM IN THE VICINITY OF THE KVTN TERMINAL
THROUGH MID AFTERNOON. THERE COULD BE ADDITIONAL THUNDERSTORM
DEVELOPMENT THIS AFTERNOON OVER THE PANHANDLE AND WESTERN
SANDHILLS BUT EXPECT COVERAGE TO BE ISOLATED AND DON/T HAVE HIGH
CONFIDENCE ON HOW FAR EAST ANY STORMS WILL GO. THEREFORE HAVE NO
MENTION OF STORMS LATER THIS AFTERNOON AND EVENING IN THE TERMINAL
FORECASTS. A SURFACE BOUNDARY WILL MOVE ACROSS WESTERN NEBRASKA
SUNDAY MORNING AND APPROACH BOTH KVTN AND KLBF SITES BY 18Z. THIS
BOUNDARY WILL SHIFT WINDS AROUND TO THE WEST-NORTHWEST. PRIOR TO
THIS WIND SHIFT...THE WINDS WILL STAY SOUTHERLY.

&&

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

$$

SYNOPSIS...CDC
SHORT TERM...BROOKS
LONG TERM...CDC
AVIATION...BROOKS






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