Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 210938
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
338 AM CST SUN DEC 21 2014

.SYNOPSIS...
ISSUED AT 332 AM CST SUN DEC 21 2014

A LEESIDE TROUGH OF LOW PRESSURE EXTENDS ACROSS MONTANA INTO EASTERN
WYOMING AND EASTERN COLORADO. LIGHT WEST WINDS ACROSS MOST OF
WESTERN NEBRASKA WITH THE EXCEPTION OF THE FAR EASTERN ZONES. THE
WESTERN EDGE OF STRATUS REMAINS ACROSS THE FAR EASTERN ZONES ALONG
WITH AREAS OF FOG WITH VISIBILITY OF A HALF MILE AT ONL.
TEMPERATURES IN WESTERN NEBRASKA RANGING FROM 24 AT LBF TO 36 AT
IML.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 332 AM CST SUN DEC 21 2014

AREAS OF FOG...LOCALLY DENSE...MAY CONTINUE AS LONG AS 15Z FOR THE
EASTERN FOUR COUNTIES. DO THINK THAT INCREASING MID AND HIGH
CLOUDINESS WORKING INTO THAT AREA WILL IMPROVE FOG CONDITIONS TOWARD
12Z. SKIES ARE CURRENTLY CLEAR FROM FAR EASTERN WYOMING INTO THE
WESTERN NEBRASKA PANHANDLE...SO WILL SEE A PERIOD OF MOSTLY SUNNY
SKIES THIS MORNING IN THE WEST FOLLOWED BY PARTLY TO MOSTLY CLOUDY
SKIES IN THE AFTERNOON. A FAIRLY STRONG DISTURBANCE CURRENTLY
LOCATED FROM SWRN BRITISH COLUMBIA AND NORTHERN WASHINGTON STATE
WILL DIG SOUTHEAST TODAY INTO EASTERN MONTANA...SWRN SOUTH DAKOTA
INTO THE WESTERN NEBRASKA PANHANDLE. AN ASSOCIATED PV ANOMALY SHOWN
TO DESCEND TO 550MB BY 00Z MONDAY. A STRONG H25 JET MAX EXCEEDING
160KT TO EXTEND SOUTH OF THIS FEATURE ACROSS THE PACIFIC NW INTO THE
NORTHERN GREAT BASIN. THE APPROACH OF THIS SYSTEM WILL BRING A GOOD
CHANCE FOR RAIN /50 PERCENT/ TO SHERIDAN AND WRN CHERRY COUNTY BY
LATE THIS AFTERNOON. THIS IN GOOD AGREEMENT BY THE NAM AND GFS. H85
TEMPS TODAY RANGING FROM 5C TO 7C SUPPORT HIGHS OF 42 TO 47 MOST
AREAS. THE EXCEPTION TO BE ACROSS THE FAR EASTERN ZONES WHERE HIGHS
LIMITED TO THE UPPER 30S. WENT NEAR A BLEND OF THE MET AND MAV
GUIDANCE. THE PRESENCE OF SOME EXISTING SNOW COVER IN THE SANDHILLS
AND SKIES TURNING MOSTLY CLOUDY THIS AFTERNOON TO LIMIT HIGHS.

FOR TONIGHT...THE DISTURBANCE WILL DEEPEN INTO A CLOSED LOW CENTERED
NEAR YANKTON SOUTH DAKOTA BY 12Z MONDAY. STRONG UPPER RIDGING
INDICATED JUST OF THE WEST COAST AND ALSO ALONG THE EASTERN
SEABOARD. WARM AIR ADVECTION PRECIPITATION AHEAD OF THIS SYSTEM TO
BRING LIKELY RAIN CHANCES /60 PERCENT/ FOR AREAS EAST OF A
VALENTINE...MULLEN AND BROKEN BOW LINE THIS EVENING. THEN AFTER
MIDNIGHT... PRECIPITATION WILL BEGIN TO WRAP SOUTHWARD ON THE
WESTWARD SIDE OF THE CLOSED LOW FROM SOUTH DAKOTA INTO THE WESTERN
SANDHILLS. AFTER MIDNIGHT...POPS HOWEVER LIMITED TO 20-30 PERCENT.
TEMPERATURES WILL REMAIN ABOVE FREEZING TONIGHT UNTIL AFTER 09Z...SO
MENTION THEREAFTER IS FOR CHC/SLIGHT CHC RAIN OR FREEZING RAIN SOME
AREAS OF THE WEST. NORTHWEST WINDS AT H85 INCREASE CONSIDERABLY
AFTER MIDNIGHT TO 45 TO 50 KTS. AS THESE WINDS MIX DOWN...GUSTS FROM
20 TO 30 KTS ARE POSSIBLE.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 332 AM CST SUN DEC 21 2014

A PV ANOMALY WILL BE DIVING SOUTHEAST INTO WESTERN NEBRASKA ON
EASTERN PERIPHERY OF 170 KT JET DIGGING INTO THE NORTHERN
ROCKIES...AND AS A RESULT...A CYCLONE BOTH AT THE SURFACE AND ALOFT
WILL RAPIDLY STRENGTHEN ACROSS SOUTHEAST SOUTH DAKOTA DURING THE DAY
MONDAY. THESE FEATURES WILL CONTINUE TO DEVELOP SOUTHEASTWARD INTO
EASTERN NEBRASKA AND WESTERN IOWA MONDAY NIGHT...THEN START TO TRACK
EAST NORTHEAST ACROSS IOWA TOWARD WISCONSIN TUESDAY AND TUESDAY
NIGHT. MODELS HAVE QUICKLY COME INTO GOOD AGREEMENT ON THE TRACK OF
THIS SYSTEM TONIGHT...AS THE UPPER LEVEL ENERGY IS NOW BEING SAMPLED
BY THE UPPER AIR NETWORK ACROSS THE PACIFIC NORTHWEST AND WESTERN
CANADA.

THERE HAS BEEN A SIGNIFICANT ADJUSTMENT SOUTHWARD WITH THE TRACK OF
THE SYSTEM IN THIS EVENINGS MODEL RUNS...AND ALSO A MORE ORGANIZED
AND STRONGER SYSTEM. THIS SYSTEM HAS BECOME A REAL
CONCERN...ESPECIALLY ACROSS NORTHERN NEBRASKA...AND HAVE
SIGNIFICANTLY INCREASED SNOW CHANCES MONDAY AFTERNOON AND MONDAY
NIGHT. THE CENTERS OF THE H500 MB AND H700 MB CLOSED LOWS SHOULD BE
LOCATED ACROSS SOUTHEAST SOUTH DAKOTA BY LATE MONDAY
AFTERNOON...WITH A MODERATELY DEEP SURFACE LOW NEAR SIOUX FALLS.
THESE FEATURES WILL ONLY VERY SLOWLY TRACK SOUTHEAST INTO WESTERN
IOWA BY MIDDAY TUESDAY. DEEP NORTHERLY FLOW ON THE WESTERN SIDE OF
THE SYSTEM WILL WRAP MOISTURE INTO NORTHERN NEBRASKA THROUGH THE
DAY MONDAY AND INTO MONDAY NIGHT...AND A PROLONGED PERIOD OF LIFT
IS NOTED THROUGH THE SATURATED DGZ. THIS TYPE OF SET UP /DEEP
MOIST NORTHERLY FLOW/ CAN BRING NORTHERN SHERIDAN COUNTY SEVERAL
INCHES OF SNOW WITHIN THE UPSLOPE AREA OF THE PINE RIDGE. HAVE A
TOTAL SNOWFALL OF AROUND 4 INCHES IN THIS AREA BY TUESDAY
MORNING...WITH GENERALLY 1 TO 3 INCHES ACROSS THE REST OF NORTHERN
NEBRASKA. H850 MB WINDS INCREASE TO AROUND 55 KTS MONDAY
NIGHT...AND BLOWING SNOW COULD BECOME A PROBLEM AS SURFACE WINDS
INCREASE TO AROUND 25 MPH WITH HIGHER GUSTS. SOME LIGHT SNOW IS
POSSIBLE FARTHER SOUTH...BUT LESS THAN AN INCH OF TOTAL
ACCUMULATION IS EXPECTED AT THIS TIME.

HAVE LOWERED HIGHS IN THE WAKE OF THE SYSTEM TUESDAY AND WEDNESDAY.
MODELS STILL DEVELOP A DOWNSLOPE CHINOOK WIND WEDNESDAY...BUT WITH
POTENTIAL SNOW COVER WILL KEEP HIGHS ON THE CONSERVATIVE
SIDE.

THE NEXT SYSTEM ARRIVES CHRISTMAS DAY. THE MODELS ARE INDICATING AN
OVERALL WEAKENING TREND WITH THIS SYSTEM...HOWEVER IT STILL
APPEARS A PERIOD OF AT LEAST LIGHT SNOW IS POSSIBLE CHRISTMAS DAY
AND CHRISTMAS NIGHT...ALONG WITH FALLING TEMPERATURES AND GUSTY
NORTH WINDS. MAINLY DRY AND CHILLY WEATHER IS EXPECTED IN THE WAKE
OF THIS SYSTEM FRIDAY AND SATURDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1112 PM CST SAT DEC 20 2014

WIDESPREAD VISIBILITY BELOW 3SM WILL CONTINUE IN NORTH CENTRAL
NEBRASKA...EAST OF AN ANW-BBW LINE WHICH INCLUDES BUB AND ONL.
VISIBILITY COULD BE RESTRICTED TO LESS THAN 1SM IN THAT AREA. THERE
IS ALSO A POSSIBILITY OF RESTRICTED VISIBILITY ALONG AND SOUTH OF A
BUB-OGA LINE WHERE 3SM OR LOWER IS LIKELY WITH BR. THE REST OF
WESTERN NEBRASKA...INCLUDING VTN...TIF AND MHN IS EXPECTED TO HAVE
CEILING AND VISIBILITY IN THE VISUAL CATEGORY.

&&

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

&&

$$

SYNOPSIS...ROBERG
SHORT TERM...ROBERG
LONG TERM...TAYLOR
AVIATION...SPRINGER



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