Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 230522
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1122 PM CST MON DEC 22 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 403 PM CST MON DEC 22 2014

COMPLICATED NEXT 24 HOURS AS A POTENT STORM SYSTEM MOVES ACROSS THE
NORTHERN AND CENTRAL PLAINS.

WATER VAPOR IMAGERY AT 20 SHOWED AMPLIFIED UPPER LEVEL FLOW WITH A
STRONG RIDGE OVER THE EASTERN PACIFIC WITH A DEEP TROUGH ACROSS THE
CENTRAL PART OF THE CONUS PUTTING THE NORTHERN AND CENTRAL PLAINS IN
NORTHWEST FLOW. A PV ANOMALY WAS NOTED OVER SOUTHERN KANSAS WHILE IT
APPEARS THE UPPER LOW OVER SOUTH DAKOTA IS IN THE PROCESS OF CLOSING
OFF. ALSO...A FEW EMBEDDED SHORTWAVES UP TOWARDS THE TOP OF THE
RIDGE...ONE OVER SOUTHWEST COLORADO AND ANOTHER OVER NORTHWEST
MONTANA. AT THE SURFACE...THE LOW HAS BECOME ELONGATED THROUGH THE
DAY AND WAS LOCATED FROM SOUTHEAST SOUTH DAKOTA INTO SOUTHEAST
NEBRASKA. THE PRESSURE GRADIENT TIGHTENED THROUGH THE DAY AND WITH
SUNSHINE ACROSS MUCH OF THE AREA...THE BOUNDARY LAYER HAS BEEN ABLE
TO MIX WELL...IN SOME LOCATIONS UP NEAR 700-750MB. THIS HAS CAUSED
WINDS GUSTING TO 30KTS TO MIX TO THE SURFACE...AND HAS ALLOWED
TEMPERATURES TO RISE INTO THE MID 40S FOR MUCH OF THE AREA.

FOR TONIGHT AND TUESDAY...THE UPPER LOW WILL DROP A BIT FURTHER
SOUTH OVER NEBRASKA THEN WILL BEGIN TO PIVOT AND HEAD EAST SLOWLY
THROUGH THE DAY TUESDAY WHILE THE PV ANOMALY OVER KANSAS WILL LIFT
INTO EASTERN IOWA. AS THIS IS A SLOW PROGRESSION...THE SURFACE LOW
WILL ALSO SEE SLOW EASTERN PROGRESSION AND BY 00Z WEDNESDAY WILL
HAVE MOVED INTO EASTERN IOWA. MOISTURE WILL CONTINUE TO BE PULLED
SOUTH ACROSS NEBRASKA ON THE BACKSIDE OF THE SYSTEM AS SHOW BY
MOISTURE TRANSPORT VECTORS FROM 925MB THROUGH 700MB. THE AMOUNT OF
MOISTURE ISN/T OVERLY ANOMALOUS...BUT THE NAM SHOWS PRECIPITABLE
WATER VALUES BETWEEN 100 AND 150 PERCENT OF NORMAL FOR MUCH OF THE
AREA TONIGHT THEN GOING DOWN SLIGHTLY FOR TUESDAY. LOOKING FOR THE
HEAVIEST SNOW AMOUNTS OVER NORTHERN SHERIDAN COUNTY WHERE UPSLOPE
FLOW WILL PROMOTE STRONGER LIFT AND HIGHER AMOUNTS. SNOW TO LIQUID
RATIOS DON/T LOOK REAL HIGH WITH THIS EVENT...AND A RANGE OF 11:1 TO
14:1 WERE USED. THIS LED TO AMOUNTS OF 4 TO 6 INCHES OVER NORTHERN
SHERIDAN COUNTY...WITH LESSER AMOUNTS OF 1 TO 4 INCHES ACROSS THE
REMAINDER OF THE FORECAST AREA.

COLDER AIR WILL ALSO BE FUNNELED INTO THE AREA OVERNIGHT AND TUESDAY
WITH 850MB TEMPERATURES FALLING TO -5C TO -8C. THIS ISN/T TERRIBLY
COLD BUT AS OF THE CURRENT TIME THE ENTIRE COLUMN /EXCEPT FOR THE
NEAR SURFACE LAYER/ HAS DROPPED BELOW 0C SO ALL PRECIPITATION WILL
SWITCH OVER TO SNOW THIS EVENING AS TEMPERATURES DROP INTO THE MID
20S TO LOW 30S. THEN ON TUESDAY...NOT EXPECTING MUCH OF A DIURNAL
RISE IN TEMPERATURES AS COLD AIR ADVECTION WILL BE ONGOING...WITH
PRECIPITATION AND OVERCAST SKIES SO HIGHS IN THE UPPER 20S TO MID
30S ARE EXPECTED.

THE LAST CONCERN IS WINDS THROUGH THE PERIOD. THE PRESSURE GRADIENT
WILL BE TIGHTEST INTO THE DAY TUESDAY WITH 6HR PRESSURE RISES OF
7MB. CLOSELY EXAMINED FORECAST SOUNDINGS WITH WINDS AT THE TOP OF
THE MIXED LAYER OF 50-60KTS THROUGH THE DAY. JUST NOT QUITE SURE HOW
WELL THIS WILL TRANSLATE TO THE SURFACE AS SOME OF THE SPEED WILL BE
LOST. THE STRONGEST WINDS ARE EXPECTED WEST OF HIGHWAY 83 WHERE THE
TIGHTEST PRESSURE GRADIENT WILL BE LOCATED...MIXING WILL BE
DEEPER...AND WINDS ALOFT WILL BE STRONGER. SUSTAINED WINDS MAY
APPROACH 40 MPH WITH GUSTS NEARING 55 MPH AT TIMES. ALTHOUGH A FEW
LOCATIONS COULD HIT HIGH WIND WARNING...NOT CONFIDENT ON WIDESPREAD
HIGH WIND WARNING CRITERIA BEING MET SO WILL NOT ISSUE ANY HEADLINES
CONSIDERING THIS THREAT AT THIS TIME.

WHAT THE WINDS WILL DO IS BLOW THE SNOW AROUND THAT DOES FALL
THROUGH TUESDAY. HAVE UPGRADED THE WINTER WEATHER ADVISORY FOR
SHERIDAN COUNTY AS NEAR 6 INCHES AND 30-40 MPH WINDS WILL CAUSE LOW
VISIBILITIES AND HAZARDOUS WINTER CONDITIONS. ALSO EXPANDED THE
WINTER WEATHER ADVISORY ACROSS THE REMAINDER OF THE NORTHERN HALF OF
THE FORECAST AREA WHERE AT LEAST 2 INCHES OF SNOW IS EXPECTED IN
COMBINATION WITH THE STRONG WINDS. WILL NEED TO KEEP A CLOSE EYE ON
HOW CONDITIONS EVOLVE THROUGH TONIGHT AND TOMORROW WITH THE WINDS
AND SNOW AS AREAS FURTHER SOUTH COULD NEED TO BE ADDED TO THE
ADVISORY IF THERE IS ENOUGH SNOW TO CAUSE BLOWING SNOW LEADING TO
HAZARDOUS TRAVEL CONDITIONS.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 403 PM CST MON DEC 22 2014

MODELS HAVING PROBLEMS IN THE MID TERM WITH TIMING AND PLACEMENT
OF UPPER FEATURES. TOMORROW NIGHT HAVE ENDED PRECIPITATION AND
ACCOUNTED FOR SOME PARTIAL CLEARING FROM WEST TO EAST WITH COLDER
LOWS OVER THE SNOW FIELD TO THE NORTH. AS TODAYS SYSTEM PUSHES
EAST INTO INDIANA THROUGH THE DAY WEDNESDAY A TROUGH DROPS INTO
THE WEST COAST AND A RIDGE OF WARMER DRIER AIR BUILDS NORTH INTO
THE ROCKIES AND NORTHERN PLAINS. 850MB TEMPERATURES INCREASE FROM
-7C 6Z WED TO +8C 12Z THURSDAY. HAVE WARMED TEMPERATURES OVER THE
WEST ON WEDNESDAY WITH SUN AND RIDGE BUILDING EAST. HAVE KEPT
TEMPERATURES IN THE 20S WEDNESDAY NIGHT WITH SOUTHWEST FLOW
INCREASING CLOUDS. THURSDAY WITH TIMING ISSUES WITH THE FRONT
HAVE GONE WITH DELAYING SNOW CHANCES INTO THE AFTERNOON AND THEN
ONLY A SLIGHT CHANCE AND HAVE GONE WITH HIGHER TEMPERATURES AHEAD
OF THE FRONTAL PASSAGE. OPEN WAVE AND VERY PROGRESSIVE HAVE ABOUT
AN INCH OF ACCUMULATION GOING. COLD AIR ADVECTION WILL GET RAMPED
UP THROUGH THE EVENING WITH GOOD NORTHWESTERLY FLOW. TEMPERATURES
FALLING INTO THE TEENS. ON FRIDAY AFTER A COLD START AND
CONTINUING COLD AIR ADVECTION OVER FRESH SNOW COVER WILL SEE
DAYTIME TEMPERATURES ONLY IN THE 20S. WITH PARTIAL CLEARING FRIDAY
NIGHT AND 1034MB SURFACE HIGH OVER HEAD WILL SEE TEMPERATURES IN
THE SINGLE DIGITS AND LOW TEENS. HIGHS IN THE 20S AND 30S ON
SATURDAY WITH SOUTHERLY FLOW AHEAD OF THE NEXT SYSTEM MOVING EAST
INTO WESTERN NEBRASKA. SIMILAR CONDITIONS ON SUNDAY AS WAVE MOVES
OUT OF THE WESTERN CONUS INTO THE CENTRAL PLAINS. TEMPERATURES
RISE INTO THE 30S AHEAD OF THE COOL FRONT WHICH WILL MOVE ACROSS
THE AREA SUNDAY NIGHT. SLIGHT CHANCE OF SNOW SUNDAY NIGHT AND
MONDAY WITH TEMPERATURES FALLING INTO THE 20S BEHIND THE FRONT ON MONDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1121 PM CST MON DEC 22 2014

WIDESPREAD SNOW IS EXPECTED TO CONTINUE OVER CENTRAL AND WESTERN
NEBRASKA UNTIL LATE TUESDAY MORNING. WIND 310-340 AT 15-25G27-35KT
WILL INCREASE OVER MOST OF THE AREA BY 16Z TO 20-25G30-36KT. THIS
WILL CAUSE BLOWING AND DRIFTING SNOW IN ADDITION TO ACCUMULATIONS
RANGING FROM AN INCH IN THE VICINITY OF OGA...IML...LBF AND BBW TO
MAYBE AS MUCH AS 6 INCHES SOUTH OF IEN AND UP TO 3 INCHES ALONG AND
NORTH OF AN ONL-BUB-TIF-MHN LINE. THE SNOW IS EXPECTED TO TAPER OFF
AND END BY 20Z...BUT THE BLOWING AND DRIFTING WILL CONTINUE UNTIL
ABOUT 00Z TUESDAY EVENING.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM CST /5 PM MST/ TUESDAY FOR
NEZ005>010-022>029-035>037-094.

WINTER STORM WARNING UNTIL 5 PM MST TUESDAY FOR NEZ004.

&&

$$

SHORT TERM...BROOKS
LONG TERM...POWER
AVIATION...SPRINGER






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