Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 160954
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
354 AM CST TUE DEC 16 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 354 AM CST TUE DEC 16 2014

WINTER STORM MOVES EAST BUT STRATUS BUILDS SOUTH ON NORTHERN PLAINS
INTO WESTERN NEBRASKA. THIS IS HELPING TO BUST THE OVER NIGHT LOW
FORECAST AS TEMPERATURES HOLD IN THE MID TEENS TO LOW 20S OVER
WESTERN NEBRASKA. NORTHWEST FLOW WILL DECREASE THROUGH THE MORNING.
MODELS HAVING DIFFICULTY WITH LOW LEVEL MOISTURE...STRATUS OVER
WESTERN NEBRASKA AND HAVE GONE WITH A CLOUDIER FORECAST. THIS WILL
IMPACT DAYTIME TEMPERATURES. RIDGE TO THE WEST BUILDS EAST TODAY AS
UPPER LOW OVER CANADA DROPS SOUTH INTO MINNESOTA. TEMPERATURES WILL
STRUGGLE OVER SNOW COVER AND HAVE GONE MORE CONSERVATIVE WITH MID
20S NORTH TO 30 SOUTHWEST. PACIFIC MOISTURE WILL SEND HIGH CLOUDS
OVER THE RIDGE INTO WESTERN NEBRASKA THROUGH THE DAY. TEMPERATURES
TONIGHT AGAIN QUESTIONABLE WITH SNOW COVER ON THE GROUND BUT
EXPECTED TO ONCE AGAIN REMAIN CLOUDY. HAVE GONE SLIGHTLY COLDER THAN
CONSENSUS. MAY HAVE TO BE RAISED SOME. DRY.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 354 AM CST TUE DEC 16 2014

PRIMARY FORECAST CONCERNS WITH THIS FORECAST PACKAGE DEAL WITH
TEMPERATURES THROUGH MUCH OF THE PERIOD AS WELL AS PRECIPITATION
CHANCES WEDNESDAY NIGHT INTO THURSDAY...THEN AGAIN FOR EARLY NEXT
WEEK.

MODELS ARE IN DECENT AGREEMENT THROUGH THE WEEKEND WHEN THEY BEGIN
TO DIVERGE MAINLY IN THE SPEED OF THE FLOW WHILE MAINTAINING SIMILAR
IDEAS OF THE GENERAL LARGE SCALE PATTERN.

INITIAL FORECAST CONCERNS ARE ASSOCIATED WITH THE SYSTEM MOVING
ONTO THE CALIFORNIA COAST TODAY. MODEL SOLUTIONS ARE NOW IN GOOD
AGREEMENT WITH THIS SYSTEM TRACKING ACROSS THE DESERT SOUTHWEST
AND INTO TEXAS ON FRIDAY. PRIOR TO THIS OCCURRING...MODELS ARE
BEGINNING TO COME TOGETHER ON THE HANDLING OF A LEAD SHORTWAVE
EJECTING OUT OF THE PRIMARY UPPER LOW. THE GFS/NAM HAVE NOW COME
MORE IN LINE WITH THE ECMWF/GEM WHICH LIFTS THIS SHORTWAVE TROUGH
UP THROUGH OKLAHOMA/KANSAS. THIS TRAJECTORY BRINGS INCREASED
MOISTURE UP INTO NEBRASKA AHEAD OF THE SHORTWAVE PER ISENTROPIC
LIFT THROUGH THE 285K-290K SURFACES. THIS DATA SHOWED MOISTURE
BEING PULLED NORTH FROM THE GULF INTO THE CENTRAL PLAINS. THE
MOISTURE IS NOT TERRIBLY IMPRESSIVE...BUT DO SEE PRECIPITABLE
WATER VALUES INCREASING TO ABOUT 150-175 PERCENT OF NORMAL AT
ABOUT 0.30-0.50 INCHES. THE LIFT ASSOCIATED WITH THE SHORTWAVE IS
EVEN LESS IMPRESSIVE SO NOT EXPECTING REAL EFFICIENT PRECIPITATION
PRODUCTION AND THEREFORE AMOUNTS ARE EXPECTED TO BE FAIRLY
LIGHT...MOST LIKELY LESS THAN A FEW HUNDREDTHS UP TO A TENTH OF AN
INCH OF LIQUID. NO CONCERNS ABOUT PRECIPITATION TYPE AS THE COLUMN
IS SATURATED FROM THE SURFACE THROUGH ABOUT 300MB PER FORECAST
SOUNDINGS AND CROSS SECTIONS. THE BEST LIFT IS SEEN THROUGH THE
DENDRITIC LAYER SO PERHAPS COULD GET A BIT HIGHER THAN NORMAL SNOW
TO LIQUID RATIOS...16:1 OR SO WHICH COULD LEAD UP TO AN INCH OF
SNOWFALL. ALTHOUGH IT/LL BE LIGHT...SIGNALS ARE LOOKING BETTER FOR
SNOW SO HAVE INCREASED PRECIPITATION CHANCES FOR WEDNESDAY NIGHT.

THE NORTHERN STREAM WILL BE ACTIVE AS WELL THROUGH THIS TIME
PERIOD. A WEAK SHORTWAVE TROUGH WILL MOVE ACROSS THE NORTHERN
PLAINS ON THURSDAY WHICH COULD PRODUCE A FEW FLURRIES ACROSS THE
DAKOTAS AND POTENTIALLY INTO FAR NORTHERN NEBRASKA. AT THIS
TIME...KEPT NO MENTION OF FLURRIES OR LIGHT SNOW AS CONFIDENCE IS
LOW THAT THIS WILL OCCUR. WHILE THE SOUTHERN SYSTEM MOVES ACROSS
TEXAS AND THE SOUTHERN PLAINS...A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE TROUGH WILL MOVE INTO THE NORTHERN AND CENTRAL PLAINS
AFTER MOVING EAST FROM THE PACIFIC NORTHWEST. IT CURRENTLY LOOKS
LIKE THIS SYSTEM WILL BE MOISTURE STARVED AS PACIFIC MOISTURE WILL
BE PULLED OUT AS IT CROSSES THE MOUNTAINS WHILE THE SOUTHERN
PLAINS SYSTEM WILL PROHIBIT MUCH MOISTURE FROM BEING TRANSPORTED
MUCH FURTHER NORTH THAN SOUTHERN KANSAS. SO AT THIS
TIME...SENSIBLE WEATHER IMPACTS WILL BE LOW.

THEN LOOKING INTO EARLY NEXT WEEK...THE MODELS ARE INDICATING A
BROAD LONGWAVE TROUGH PASSING ACROSS THE PLAINS AS A STRONG RIDGE
BUILDS OVER THE EASTERN PACIFIC. ALTHOUGH THERE ARE AMPLE MODEL
DIFFERENCES IN THE TIMING OF WHEN THIS TROUGH WILL MOVE THROUGH AS
WELL AS WITH ANY WEAK SHORTWAVE TROUGHS PROGRESSING THROUGH THE
MAIN FLOW...AGAIN THERE IS GOOD AGREEMENT IN THIS PATTERN SHIFT SO
WHILE TIMING WILL LIKELY NEED TO BE ADJUSTED IN UPCOMING
FORECASTS...THERE SHOULD BE PERIODIC CHANCES FOR PRECIPITATION
EARLY NEXT WEEK. ALSO...EACH PASSING WEAK SYSTEM WILL BRING THE
POTENTIAL FOR SOME STRONGER WINDS BEHIND THE SURFACE FRONTS. AT
THIS TIME MONDAY LOOKS BREEZY...BUT WITH WESTERLY DOWNSLOPE WINDS
THEY COULD ALSO PROMOTE SOME WARMER TEMPERATURES.

IN TERMS OF TEMPERATURES...NO SIGNIFICANT WARM UP IS EXPECTED
THROUGH THE NEXT 7 DAYS AS THE AREA WILL SEE MORE INFLUENCE FROM
THE NORTHERN STREAM KEEPING TEMPERATURES NEAR TO BELOW NORMAL MUCH
OF THE TIME. ALSO...WITH FRESH SNOWPACK OVER PORTIONS OF THE AREA
THESE AREAS HAVE BEEN GIVEN A COLD BIAS IN THE TEMPERATURE
FORECAST THROUGH MUCH OF THE WEEK. NOT SEEING ANY SIGNIFICANT
SIGNALS FOR DAYS WITH STRONG COLD OR WARM AIR
ADVECTION...TEMPERATURES WILL BE HIGHLY DEPENDENT ON THE CLOUD
FORECAST WHICH IS SLIGHTLY PROBLEMATIC ESPECIALLY THROUGH THE
EARLY PARTS OF THE FORECAST PERIOD. THROUGH FRIDAY...HIGH PRESSURE
AT THE SURFACE WILL HAVE INFLUENCE OF THE NORTHERN AND CENTRAL
PLAINS AS IT WILL SIT OFF TO THE EAST OF THE LOCAL AREA. THE
MODELS ARE KEEPING MUCH OF THE FORECAST AREA SOCKED IN UNDER LOW
CLOUDS ON THE BACK SIDE OF THE SURFACE HIGH WHICH IF THIS OCCURS
WILL KEEP OVERNIGHT LOWS WARM AND DAYTIME HIGHS COOLER.
HOWEVER...IF THIS DOES NOT OCCUR OVERNIGHT LOWS WILL BE QUITE COLD
DUE TO LIGHT WINDS AND GOOD RADIATIONAL COOLING WITH SLIGHTLY
WARMER HIGHS. DON/T HAVE GREAT CONFIDENCE IN THE CLOUDS STAYING IN
PLACE FOR SEVERAL DAYS WITHOUT A REAL STRONG INFLUX OF MOISTURE IN
THE LOW LEVELS SO HAVE NOT TOTALLY JUMPED ON BOARD WITH USING
TEMPERATURES WITH COMPLETE INFLUENCE FROM THE CLOUDS. BUT HAVEN/T
GONE THE OTHER DIRECTION EITHER. THIS LEADS TO HIGH CONFIDENCE
THAT ADJUSTMENTS WILL BE NEEDED IN TEMPERATURES THROUGH MUCH OF
THE PERIOD AS IT BECOMES MORE CLEAR WHAT THE CLOUDS WILL DO
THROUGH THE WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1125 PM CST MON DEC 15 2014

WIDESPREAD MVFR CIGS EXTEND THROUGH THE FCST NORTH INTO THE NRN
PLAINS AND SOME MODELS HOLD THEM IN PLACE OVERNIGHT THROUGH
TUESDAY WHILE OTHERS MIX OUT TO VFR ALMOST IMMEDIATELY. SINCE THE
MODELS ARE FAIRLY EVENLY SPLIT...NO CONSENSUS...THE FCST RELIES ON
DAYTIME MIXING WITH VFR EXPECTED 15Z-18Z TUESDAY. VFR IS EXPECTED
THEREAFTER.


&&

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

$$

SHORT TERM...POWER
LONG TERM...BROOKS
AVIATION...CDC







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