Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 171804
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1204 PM CST WED DEC 17 2014

.UPDATE...
ISSUED AT 1006 AM CST WED DEC 17 2014

SOUTHERLY WINDS HAVE INCREASED BOUNDARY LAYER MOISTURE THIS
MORNING. ALSO SEEING A LITTLE WARM AIR ADVECTION IN THE STRATUS
LAYER. THIS IS LEADING TO ENOUGH LIFT TO PRODUCE SOME LIGHT
PRECIP. RADAR SHOWING A FEW WEAK ECHOES WHICH IS REACHING THE
GROUND IN A FEW LOCATION...PER LAW ENFORCEMENT REPORTS...AS
FREEZING DRIZZLE. SOUNDINGS SUGGEST TEMPERATURES ARE BORDERLINE
COLD ENOUGH FOR SNOW OR FREEZING DRIZZLE...AND WITH SATELLITE
SHOWING SOME MID LEVEL CLOUDS TO MOVE OVERHEAD. THINK A
SEEDER/FEEDER SET UP WITH BOTH FREEZING DRIZZLE OR FLURRIES ARE
POSSIBLE. GRIDS/FORECAST HAS BEEN UPDATED.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 350 AM CST WED DEC 17 2014

MODELS IN FAIR AGREEMENT IN THE NEAR TERM ALTHOUGH THE NAM IS COMING
IN COLDER AND WITH HIGH TEMPERATURES STRUGGLING YESTERDAY WILL GO
WITH THE COLDER SOLUTION AND TREND THE FORECAST TOWARDS NAM
SOLUTION. TEMPERATURES TODAY AND TONIGHT AND CHANCES OF LIGHT
PRECIPITATION OVER THE FORECAST AREA TONIGHT MAIN FOCUS. THERE IS A
SURFACE TROUGH ALONG THE FRONT RANGE OF THE ROCKIES WITH SURFACE
HIGH PRESSURE TO THE NORTHEAST OF THE FORECAST AREA. SOUTH TO
SOUTHEAST FLOW OVER THE AREA TODAY AND TONIGHT. THE GULF IS OPEN AND
THERE IS SOME MOISTURE RETURN OVER THE SOUTHERN AND CENTRAL PLAINS
TODAY. RATHER COMPLICATED UPPER PATTERN WITH H5 RIDGE INTO CENTRAL
CANADA...CLOSED LOW OVER WISCONSIN WHICH HAS DRUG COLDER AIR SOUTH
ACROSS THE NORTHERN PLAINS INTO WESTERN NEBRASKA THEN A TROUGH OVER
THE WESTERN CONUS WITH SEVERAL STRONGER WAVES MOVING THROUGH. COLD
POOL ALOFT OVER WESTERN NEBRASKA WITH 850MB TEMPERATURES -4C TO -9C
THROUGH THE DAY TODAY OVER WESTERN NEBRASKA. THIS COMBINED WITH
STRATUS AND SNOW COVER WILL GO BELOW GUIDANCE FOR TODAY AND
GENERALLY KEEP TEMPERATURES IN THE MID 20S. WILL KEEP PATCHY FOG
GOING OVER FAR WEST AGAIN THIS MORNING ALONG THE LEADING EDGE OF THE
STRATUS AS IT SLOWLY ERODES THIS MORNING.

FAST MOVING SHORTWAVE OVER SOUTHERN CALIFORNIA EARLY THIS MORNING
WILL MOVE ACROSS THE ROCKIES TODAY AND ONTO THE CENTRAL
PLAINS...WESTERN KANSAS...TONIGHT PHASING WITH A NEGATIVELY TILTED
WAVE MOVING INTO THE NORTHERN PLAINS. 100KT-130KT UPPER JET DRIVING
IT ACROSS. WAVE WILL SHEAR OUT ACROSS SOUTHEAST NEBRASKA THROUGH THE
EARLY MORNING THURSDAY. BETTER FORCING ACROSS CENTRAL KANSAS AND
SHOULD GIVE SOUTHWEST NEBRASKA A GLANCING BLOW TONIGHT. HAVE GONE
WITH PREVIOUS FORECAST THINKING ENOUGH UPGLIDE AND DEEP LAYER
MOISTURE TO 750MB WILL SEE A DUSTING TO AN INCH GENERALLY SOUTH OF
INTERSTATE 80 AND POSSIBLY SOME PATCHY FREEZING DRIZZLE AS DRIER AIR
FILTERS IN ALOFT. MILDER NIGHT WITH WAA AND CLOUD COVER HAVE KEPT
LOWS IN THE MID TEENS.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 350 AM CST WED DEC 17 2014

FORECAST CONCERNS DEAL WITH LINGERING LIGHT PRECIPITATION CHANCES
THURSDAY MORNING...TEMPERATURES THROUGHOUT THE PERIOD...THEN WITH
PRECIPITATION CHANCES AND STRONG WIND POTENTIAL FOR EARLY NEXT WEEK.

MODELS ARE IN GOOD GENERAL AGREEMENT WITH THE OVERALL PATTERN
THROUGH THE NEXT 7 DAYS...HOWEVER DO SEE SOME DIFFERENCES IN DETAILS
WHICH DO AMOUNT TO LESSER CONFIDENCE IN THE FORECAST FOR A FEW
FORECAST PERIODS. ON THE WHOLE THOUGH...THE TREND IS FOR AN ACTIVE
WEATHER PATTERN ACROSS THE CONUS THROUGH THE WEEKEND...AS IT MOVES
TOWARD A LARGE SCALE CHANGE WITH RIDGING OVER THE EASTERN PACIFIC
AND WEST COAST WITH A LONGWAVE TROUGH IN PLACE ACROSS THE CENTRAL
PORTION OF THE COUNTRY BY THE EARLY PARTS OF NEXT WEEK.

WATER VAPOR IMAGERY THIS MORNING SHOWS A COUPLE OF SEPARATE PV
ANOMALIES AMONG THE TROUGH THAT HAS PUSHED INTO THE CALIFORNIA COAST
OVER THE LAST 12 HOURS. THE FIRST WAS LOCATED OVER NORTHWEST MEXICO
WHILE THE SECOND WAS JUST PUSHING INLAND ACROSS SOUTHERN CALIFORNIA.
THESE TWO PV ANOMALIES WILL MERGE TOGETHER OVER THE NEXT 24 HOURS
AND MOVE INTO THE CENTRAL PLAINS WHICH WILL BRING CHANCES FOR LIGHT
SNOW TO THE SOUTHERN PART OF THE FORECAST AREA WEDNESDAY NIGHT.
PRIOR MODEL RUNS HAD BEEN A BIT SLOWER MOVING THIS SHORTWAVE TROUGH
EAST INTO THE MID MISSISSIPPI RIVER VALLEY REGION ON THURSDAY WHICH
HAD KEPT LINGERING CHANCES FOR SNOW IN THE SOUTHEAST PART OF THE
FORECAST AREA. THE MODELS ARE IN GOOD CONSENSUS THAT ANY POTENTIAL
FOR MEASURABLE PRECIPITATION WILL HAVE MOVED EAST OF THE AREA BY 12Z
THURSDAY AS MOISTURE WILL HAVE DIMINISHED SUBSTANTIALLY BY THAT
TIME. THEREFORE...HAVE REMOVED THE MENTION OF ANY MEASURABLE
PRECIPITATION FROM THE FORECAST FOR THURSDAY MORNING.
HOWEVER...FORECAST SOUNDINGS ARE SHOWING A SATURATED NEAR SURFACE
LAYER WHICH IS ABOUT 2500FT DEEP AND BASICALLY ISOTHERMAL BETWEEN 0C
AND -10C. THIS SIGNAL DOES GET TO BE LESS GOING WESTWARD AS THE
MOISTURE LAYER DECREASES GOING FURTHER INTO THE LBF FORECAST AREA.
ABOVE THIS...DRY AIR EXISTS SO NO ICE WILL BE INTRODUCED INTO THIS
LAYER SO IF THERE IS ANY PRECIPITATION IT WILL BE DRIZZLE.
AND...WITH TEMPERATURES BELOW FREEZING...IT WOULD BE FREEZING
DRIZZLE. THE LIFT IN THIS LAYER IS QUITE WEAK SO REALLY THINKING
THAT DRIZZLE MAY BE HARD TO PRODUCE AND MAY JUST BE AN EXTENSIVE
STRATUS DECK...BUT PREVIOUS FORECAST HAD MENTION OF FREEZING DRIZZLE
AND WITH THE SIGNAL FOR SATURATION IN THE LOW LEVELS STILL THERE
DIDN/T WANT TO REMOVE IT AT THIS POINT BUT WILL MONITOR CLOSELY IN
UPCOMING FORECASTS IF IT WILL REMAIN NEEDED.

HIGH PRESSURE AT THE SURFACE WILL BE EAST OF THE REGION...CENTERED
OVER THE UPPER MISSISSIPPI RIVER VALLEY REGION THROUGH THURSDAY AND
THURSDAY NIGHT BEFORE BEGINNING TO MIGRATE EASTWARD. THIS WILL KEEP
SOUTHERLY RETURN FLOW IN THE LOW LEVELS ONGOING OVER MUCH OF
NEBRASKA AND THE MODELS WANT TO HOLD ONTO STRATUS ACROSS SOUTHWEST
INTO NORTH CENTRAL NEBRASKA. CLOUD COVER WILL HAVE A HIGH IMPACT ON
TEMPERATURES THURSDAY AND THURSDAY NIGHT. WILL START TO SEE SOME
WARM AIR ADVECTION ON THURSDAY AT 850MB BUT SURFACE FLOW WILL BE
LIGHT SO NOT EXPECTING MUCH MIXING EVEN IF THE CLOUDS DO BREAK UP
ALLOWING SUNSHINE. ALSO...AREAS WHERE THE SUN IS MORE LIKELY TO
SHINE IS WHERE THERE IS THE 4-9 INCH SNOWPACK WHICH WILL ALSO HELP
LIMIT THE MIXING/WARMING POTENTIAL. SO HAVE KEPT HIGHS ON THE COOLER
SIDE FOR THURSDAY EVEN THOUGH MOST AREAS SHOULD SEEN NEAR OR
SLIGHTLY ABOVE FREEZING READINGS. TEMPERATURES THURSDAY NIGHT WILL
ALSO BE HIGHLY DEPENDENT ON CLOUD COVER. ACROSS THE
NORTHWEST...AGAIN BETTER CHANCES FOR CLEARER SKIES AND WITH LIGHT
WINDS AND THE SNOWPACK...COULD BE A PRETTY COLD MORNING. KEPT
TEMPERATURES NEAR PRIOR FORECAST AS IT LOOKED GOOD WITH LOWS
GENERALLY IN THE TEENS AND POSSIBLY DOWN INTO THE SINGLE DIGITS OVER
THE NORTHEAST PANHANDLE/WESTERN SANDHILLS.

THE PRIMARY UPPER LOW WHICH IS MOVING INTO CALIFORNIA CURRENTLY WILL
MOVE ACROSS THE SOUTHWESTERN CONUS OVER THE NEXT 24-36 HOURS AND BY
12Z FRIDAY WILL BE MOVING INTO/ACROSS WESTERN TEXAS. THE MODELS HAVE
BEEN CONSISTENT WITH THIS SIGNAL...WHILE A SEPARATE SHORTWAVE TROUGH
MOVES INTO THE NORTHERN AND CENTRAL PLAINS THROUGH THE NORTHERN
STREAM. THE SOUTHERN SYSTEM WILL BE THE DOMINANT ONE...KEEPING ALL
MOISTURE BEING PULLED NORTH FROM THE GULF OVER THE SOUTHERN PLAINS.
HAVING NO MOISTURE IN PLACE LOCALLY...ALONG WITH THE NORTHERN SYSTEM
LOOSING ANY OF ITS ASSOCIATED MOISTURE UPON MOVING ACROSS THE ROCKY
MOUNTAINS WILL LEAD TO A DRY PASSAGE OF THIS SYSTEM. BY SEE WINDS
INCREASE A BIT BUT SENSIBLE WEATHER IMPACTS LOOK TO BE LOW AT THIS
TIME. WITH THE PACIFIC FRONT MOVING THROUGH FRIDAY NIGHT COULD SEE
TEMPERATURES A BIT WARMER FOR THE WEEKEND AS DOWNSLOPE LOW LEVEL
FLOW GETS IN PLACE AND TEMPERATURES ALOFT INCREASE /850MB
TEMPERATURES RISE UP TO 5C. KEPT THE CURRENT FORECAST ON THE
CONSERVATIVE SIDE AND WILL SEE HOW TEMPERATURES TREND THE NEXT FEW
DAYS BEFORE GOING WARMER.

THE PATTERN CHANGE WILL BE WELL ON ITS WAY BY SUNDAY AS THE MODELS
REALLY START TO BUILD THE RIDGE OVER THE EASTERN PACIFIC. AS THIS
OCCURS...A TROUGH MOVES ACROSS THE CENTRAL PART OF THE CONUS. A LACK
OF MOISTURE WILL KEEP THE FORECAST DRY AS THIS PASSES ON SUNDAY BUT
COULD SEE A NEED TO ADD IN SOME LOW CHANCES AT SOME POINT. THIS IS A
CASE WHERE THE MODELS ARE IN GOOD AGREEMENT WITH THE LARGE SCALE
PATTERN...BUT ON THE LOCAL LEVELS THERE ARE DIFFERENCES IN THE
DETAILS WHICH MAY OR MAY NOT HAVE ENOUGH MOISTURE TO PRODUCE
PRECIPITATION. THEN BY MONDAY AND TUESDAY...THE TROUGH DEEPENS WITH
THE AXIS CENTERED JUST EAST OF THE LOCAL AREA AND EXTENDS DOWN INTO
EASTERN TEXAS. THIS PUTS THE LOCAL AREA DEEP IN NORTHWEST FLOW
ALOFT. ONCE THIS PATTERN GETS SETTLED IN MAY SEE DAILY CHANCES FOR
PRECIPITATION AS A MULTITUDE OF WEAK SHORTWAVE TROUGHS IS SET TO
MOVE DOWN THROUGH THE LARGE-SCALE FLOW AND ACROSS NEBRASKA. TIMING
OF PRECIPITATION CHANCES WILL LIKELY BE MODIFIED IN FUTURE FORECASTS
AS THESE DETAILS BECOME BETTER MODELED. A BIG DIFFERENCE IN THE
MODELS IS THE THERMAL PROFILES. THE ECMWF HAS MUCH COLDER AIR BEING
PULLED INTO THE PLAINS WHEN COMPARED TO THE GFS. THE COLDER SOLUTION
WOULD GIVE THE AREA MUCH COOLER TEMPERATURES ALONG WITH HAVING
PRECIPITATION ALL SNOW. ON THE OTHER HAND...THE GFS IS WARMER AND
WOULD LEAD TO NEAR OR EVEN ABOVE NORMAL TEMPERATURES AND
PRECIPITATION AS RAIN OR A MIX OF RAIN/SNOW. USED A BLENDED APPROACH
FOR THE FORECAST AT THIS POINT AND KEPT WITH CONTINUITY SAKE FOR THE
FORECAST AT THIS TIME WITH LITTLE CONFIDENCE ON WHAT SOLUTION WILL
PROVE TO BE BETTER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1200 AM CST WED DEC 17 2014

PREVAILING WIDESPREAD LOW STRATUS WITH A CHANCE FOR SOME PATCHY
FREEZING DRIZZLE AND/OR LIGHT SNOW ACROSS SOUTHWEST NEBRASKA THE
NEXT 24 HOURS. GENERALLY IFR OR BELOW CIGS ACROSS THE AREA TO
PERSIST THROUGH 18Z TOMORROW. A WEAK DISTURBANCE WILL LIFT ACROSS
KANSAS AND EASTERN NEBRASKA OVERNIGHT WITH SOME WEAK LIFT AND
LIGHT SNOW POSSIBLE ACROSS SOUTHWEST NEBRASKA. A DRY LAYER ABOVE
THE MOIST BOUNDARY LAYER MAY RESULT IN SOME PATCHY FREEZING
DRIZZLE INSTEAD OF LIGHT SNOW...ESPECIALLY ON THE NW SIDE OF THE
SIDE WHICH IS WHERE KLBF IS LIKELY TO END UP...AND WILL HAVE TO
BE MONITORED. IN ADDITION TO THE STRATUS...WILL SEE LOCAL AREAS OF
FOG WITH VISIBILITIES AT TIMES DOWN TO 3SM OR LESS.

&&

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

&&

$$

UPDATE...MASEK
SHORT TERM...POWER
LONG TERM...BROOKS
AVIATION...MASEK





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