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000
FXUS63 KLBF 021743
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1143 AM CST SUN MAR 2 2014

.SYNOPSIS...
ISSUED AT 308 AM  CST SUN MAR 2 2014

A 24 HOUR WATER VAPOR IMAGERY LOOP SHOWS THE POLAR FRONT WITH A
SOUTHWARD PLUNGE TO MONTANA...THE IDAHO PANHANDLE AND NORTHERN SOUTH
DAKOTA. AT THE SURFACE...THE 08Z PRESSURE SHOWED LOW PRESSURE OVER
WESTERN WYOMING NORTH OF BIG PINEY AND WEST OF RIVERTON. A WAVE IN
THE POLAR FRONT APPEARS TO BE ASSOCIATED WITH THAT SURFACE SYSTEM.
AN OCCLUDED FRONT OR SURFACE TROUGH EXTENDED FROM THE WYOMING LOW TO
ANOTHER NEAR SALT LAKE CITY. THERE WERE ALSO LOWS ALONG THE REST OF
THE FRONT IN WESTERN COLORADO AND SOUTHEAST OREGON.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 308 AM CST SUN MAR 2 2014

WIND CHILL IS THE MAIN FORECAST CHALLENGE TODAY AND TONIGHT. THE
CURRENT WIND CHILL HEADLINES SEEM TO BE ON TARGET FOR THIS MORNING
THOUGH WE ARE NOT SEEING WARNING CRITERIA YET. IT IS EARLY...SO WE
WILL NOT BE DOWNGRADING THE WARNING.

THE COLD AIR OVER SOUTHEAST ALBERTA AND SOUTHERN SASKATCHEWAN WILL
GIVE A REINFORCING SHOT OF COLD WITH THE POLAR FRONT AS IT PUSHES
INTO THE CENTRAL PLAINS TODAY.

WITH THE NEW COLD SHOT...ANOTHER WIND CHILL ADVISORY WOULD BE
APPROPRIATE FOR TONIGHT (SUNDAY NIGHT) AT LEAST FOR NORTH CENTRAL
NEBRASKA EAST OF HIGHWAY 83 AND NORTH OF NEBRASKA HIGHWAY 2.
HOWEVER...WE WILL HOLD OFF ON NEW HEADLINES UNTIL THE CURRENT ONES
EXPIRE.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 308 AM CST SUN MAR 2 2014

EVENTUAL RETROGRADE OF UPPER HIGH CURRENTLY OVER AK TO THE EAST
SIBERIAN SEA WILL ALLOW ASSOCIATED REX BLOCK PATTERN IN THE NRN
PACIFIC TO BREAK DOWN AND GET MORE PACIFIC ENERGY INTO THE U.S. AND
FINALLY KICK OUT THE ANOMALOUSLY COLD AIR ACROSS THE PLAINS OVER THE
COURSE OF THE COMING WEEK. THIS WILL SET THE STAGE FOR A MORE ZONAL
FLOW WITH A TRANSITORY UPPER RIDGE/TROUGH SEQUENCE ACROSS THE
NORTHERN HALF OF THE COUNTRY...AND AS MENTIONED A RETURN TO TEMPS AT
OR ABOVE AVE TOWARD THE END OF THE WEEK.

AS THIS TRANSITION OF THE HEMISPHERIC WEATHER PATTERN
HAPPENS...THERE WILL BE A FEW OPPORTUNITIES FOR MAINLY LIGHT
PRECIPITATION. AS THE UPPER LOW OVER THE NRN PACIFIC FILLS AND
SHIFTS EASTWARD IT WILL BREAK INTO SEVERAL PIECES OF ENERGY...EACH
OF WHICH WILL MOVE QUICKLY ACROSS THE NRN PLAINS. THOUGH TIMING OF
INDIVIDUAL SHORT WAVES BY THE MODELS ARE DIFFERENT...IN GENERAL THE
FIRST WILL MOVE ACROSS THE AREA MONDAY NIGHT INTO TUESDAY MORNING.
AHEAD OF THIS FEATURE...A WARM FRONT OWING TO SOUTHWEST WINDS IN LOW
LEVELS OF THE ATMOSPHERE WILL MOVE EAST DURING THE DAY. BUFR
SOUNDINGS FROM THE NAM HOWEVER SUGGEST SNOW COVER WILL LIMIT MIXING
AND WARM AIR WILL GENERALLY RIDE OVER THE SNOW FIELD AND NOT FULLY
BE REALIZED AT THE SURFACE. STILL SUNSHINE WILL ERODE SNOW COVER IN
SOME PLACES WHERE LESS EXISTS CURRENTLY. AFTER SHORT WAVE PASSES
WINDS RETURN TO NWRLY AND REINFORCING COLD AIR PLUNGES SOUTHWARD.
MODELS HAVE DIFFERENCES WITH HOW FAR TO THE SOUTHWEST THE COLD AIR
GETS AND THEREFORE CONFIDENCE IN TEMP FORECASTS ARE LACKING FOR THE
MID WEEK PERIOD. SNOW COVER WILL FURTHER COMPLICATE THIS. ALSO...NAM
BRING STRATUS IN BEHIND THE FRONT WHICH IS SLOW TO CLEAR OUT ON
TUESDAY.

THE NEXT SIGNIFICANT PIECE OF ENERGY MOVES QUICKLY INTO SOUTHWEST
NEBRASKA TUESDAY NIGHT/WED MORNING. THOUGH THERE ARE TIMING AND
PLACEMENT DIFFS WITH THE DETERMINISTIC MODELS AS ONE WOULD
EXPECT...THEY ARE GENERALLY SIMILAR IN THE EVOLUTION. THE PV ANOMALY
IS COMPACT BUT SIGNIFICANT AND WITH FAVORABLE MID LEVEL LAPSE RATES
ADVECTING AHEAD OF THE SYSTEM...STRONG ISENTROPIC LIFT AND
ASSOCIATED MID LEVEL FRONTOGENESIS /FGEN/ DEVELOPS IN A REGION OF
INSTABILITY. THE MID LEVEL FGEN HAS CONTRIBUTION FROM BOTH
FRONTOGENETIC AND ROTATIONAL COMPONENTS AND AGAIN IS BRIEF BUT
SIGNIFICANT. CROSS SECTIONS SHOW A BRIEF PERIOD OF UPRIGHT
CONVECTION POSSIBLE SERVING TO ENHANCE THE MESOSCALE LIFT...AND NAM
SOUNDINGS SHOW A BRIEFLY SATURATED DENDRITIC GROWTH ZONE...WITH A
FAIRLY DEEP AGGREGATION LAYER BELOW. THIS WOULD SUGGEST A BRIEF
PERIOD OF LARGE SNOWFLAKES THAT COULD REDUCE VSBY. SOME LACK OF
CONFIDENCE HOWEVER WITH PLACEMENT OF ULTIMATE SHORT WAVE AT THIS
TIME.

TRANSITORY RIDGING TAKES OVER TO DOMINATE THE LARGE SCALE PATTERN
FOR WESTERN NEBRASKA LATER WED INTO THURSDAY AS INCREASING AMPLITUDE
DEVELOPS ALONG THE WEST COAST IN RESPONSE TO THE NEXT DEEPENING LOW
IN THE GULF OF AK TO END THE WEEK. THIS RETURNS THE FORECAST AREA TO
THE FAMILIAR NORTHWEST FLOW ALOFT AND QUICK MOVING SHORT WAVES
MOVING THROUGH THE FLOW. THE NEXT ARRIVES FRIDAY MORNING WHICH
BRINGS LIMITED CHCS OF LIGHT PRECIP DURING THE AFTERNOON AND AN
ASSOCIATED COOL DOWN. CONFIDENCE ON ACTUAL HIGH TEMPERATURES FRIDAY
AND THEREFORE PRECIP TYPE IS LOW AT THIS TIME. 02.00 ECE SHOWS
SIGNIFICANTLY COOLER TEMPS THAN MEX GUIDANCE AS THE ECMWF MEAN
TROUGH POSITION IS FURTHER WEST. BLENDED GRID VALUES IN THE OFFICIAL
FCST CLEARLY A MEDIUM GROUND BASED ON THAT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1143 AM CST SUN MAR 2 2014

MVFR CONDITIONS WILL CONTINUE ACROSS MUCH OF WESTERN NEBRASKA
TODAY ON THE BACK SIDE OF HIGH PRESSURE. KVTN AND KLBF TERMINALS
ARE JUST EAST OF THE LOWER CEILINGS AND ARE EXPECTED TO STAY VFR.
AFTER SUNSET...THE WINDS WILL BECOME LIGHT AND VARIABLE AS ONLY
HIGH CLOUDS /AOA 25KFT AGL/ REMAIN. A CONCERN ARISES MONDAY
MORNING WHEN SOUTH WINDS STRENGTHEN ACROSS THE AREA. ENOUGH
MOISTURE MAY WORK INTO THE AREA...ESPECIALLY KLBF...WHERE LOWER
STRATUS COULD DEVELOP.

&&

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

$$

SYNOPSIS...SPRINGER
SHORT TERM...SPRINGER
LONG TERM...JWS
AVIATION...SNIVELY/MASEK