Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 010928
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
328 AM CST SUN FEB 1 2015

.SYNOPSIS...
ISSUED AT 326 AM CST SUN FEB 1 2015

AT 07Z...WATER VAPOR IMAGERY SHOWED A SHORTWAVE TROUGH MOVING OUT OF
COLORADO AND INTO THE HIGH PLAINS...WITH A GOOD PV ANOMALY OVER
WESTERN KANSAS. TO THE NORTHWEST...ANOTHER PV ANOMALY COULD BE
PICKED OUT OVER CENTRAL MONTANA. ELSEWHERE...A LARGE UPPER LOW SPUN
OVER BAJA CALIFORNIA AND NORTHWEST MEXICO WITH RIDGING OVER THE WEST
COAST. FURTHER UPSTREAM...A LARGE UPPER LOW WAS SITUATED SOUTH OF
ALASKA OVER THE NORTHERN PACIFIC. AT THE SURFACE...THE LOW WAS
CENTERED OVER CENTRAL KANSAS WITH THE COLD FRONT EXTENDING INTO THE
TEXAS PANHANDLE. ARCTIC HIGH PRESSURE WAS CENTERED OVER SOUTHERN
SASKATCHEWAN/MANITOBA WITH COLD AIR SURGING SOUTH BEHIND THE COLD
FRONT OVER THE SOUTHERN PLAINS. OBSERVATIONS AT 08Z WERE SHOWING
TEMPERATURES BELOW ZERO OVER MUCH OF NORTH DAKOTA...WITH SINGLE
DIGITS ACROSS SOUTH DAKOTA AND INTO NORTHERN NEBRASKA. IN
ADDITION...A TIGHT PRESSURE GRADIENT CAUSED WINDS TO INCREASE...WITH
READINGS OF 15 TO 20KTS WITH GUSTS TO 30KTS FOR MUCH OF THE FORECAST
AREA. LOOKING AT RADAR...THE PRIMARY AREA OF PRECIPITATION HAS
SHIFTED EAST OF THE FORECAST AREA...NOW JUST TO THE NORTHWEST OF THE
SURFACE LOW...FROM NORTH CENTRAL KANSAS INTO EASTERN NEBRASKA. THE
SNOW OVER THE LOCAL FORECAST AREA HAS DIMINISHED IN
INTENSITY...ALTHOUGH LIGHT SNOW CONTINUES TO FALL OVER MUCH OF THE
AREA. THIS SUGGESTS THE BEST FRONTOGENETIC FORCING HAS DETERIORATED
LOCALLY AND HAS SHIFTED TO THE MAIN BAND TO THE SOUTHEAST. THE SNOW
HAS BEEN TAPERING OFF OVER THE WESTERN PART OF THE FORECAST AREA
SINCE LATE EVENING...AS CAN BE SEEN ON RADAR IMAGERY. ANOTHER AREA
OF SNOW OVER WESTERN SOUTH DAKOTA THAT DEVELOPED AHEAD OF THE
SHORTWAVE TROUGH OVER MONTANA WAS MOVING INTO THE NORTHWEST PART OF
FORECAST AREA AT 08Z AND ALTHOUGH NOT HEAVY...WITH THE STRONG WINDS
WILL CONTINUE THE THREAT FOR HAZARDOUS WINTER DRIVING CONDITIONS DUE
TO BLOWING AND DRIFTING SNOW.

A VERY ACTIVE WEATHER PATTERN HAS DEVELOPED FEATURING
AMPLE PACIFIC MOISTURE AND A CLASH OF VERY WARM AIR ACROSS THE SWRN
U.S. AND ARCTIC AIR. ANOTHER STORM WILL MOVE THROUGH WRN AND NCNTL
NEB TUESDAY NIGHT AND WEDNESDAY AS AN ARCTIC FRONT MOVES THROUGH.
WARM AIR WILL SURGE INTO THE REGION AHEAD OF THIS ARCTIC FRONT.

THE COLD AIR INTRUSION TUESDAY NIGHT AND WEDNESDAY WILL BE SHORT
LIVED AS WARM AIR AND MILD TEMPERATURES WILL RETURN THURSDAY THROUGH
SATURDAY. THE MODELS SHOW A CHANCE OF SNOW TUESDAY NIGHT THROUGH
WEDNESDAY MORNING.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 326 AM CST SUN FEB 1 2015

THE SHORTWAVE TROUGH OVER THE HIGH PLAINS AND THE SURFACE LOW OVER
KANSAS WILL ALL PUSH EAST TODAY. THIS WILL CONTINUE THE DIMINISHING
TREND IN THE SNOWFALL FROM WEST TO EAST THROUGH THE MORNING HOURS.
MEANWHILE...THE SHORTWAVE TROUGH OVER MONTANA WILL DROP SOUTHEAST
THROUGH WESTERN NEBRASKA WHICH WILL LIKELY PUSH SOME OF THE SNOW NOW
OVER WESTERN SOUTH DAKOTA INTO NEBRASKA. THE BULK OF IT WILL PUSH
EAST AND COMBINE WITH THE SYSTEM OVER THE AREA NOW...WHILE RIGHT
ALONG THE PV ANOMALY...ENOUGH LIFT MAY KEEP SOME LIGHT SNOW OVER THE
NORTHERN PANHANDLE. MODELS MAY BE A BIT SLOWER WITH THE PROGRESSION
OF THE SYSTEM TODAY SO HAVE LINGERED PRECIPITATION OVER THE AREA
LONGER THAN THE PRIOR FORECAST. SO NOW THERE CONTINUES TO BE SNOW
CHANCES INTO THE AFTERNOON FOR THE FAR NORTHEAST. ADDITIONAL
ACCUMULATIONS COULD BE UP TO ANOTHER INCH OR TWO AT THE MOST OVER
NORTH CENTRAL NEBRASKA WHILE THE REMAINDER OF THE AREA WILL SEE LESS
THAN AN ADDITIONAL INCH. COLD AIR ADVECTION AND SUBSIDENCE ARE SEEN
OVER THE REGION THROUGH THE DAY BEHIND THE SYSTEM...SO LOOKING FOR
DIMINISHING CLOUD COVER AND THE BOUNDARY LAYER TO MIX. DEEPER MIXING
WILL OCCUR OVER THE SOUTHWEST FORECAST AREA AS IT WILL BE THE FIRST
TO SEE SUNSHINE AND SOME WARMING. THE NORTHEAST PART OF THE AREA
WILL STILL SEE MIXING...BUT WILL BE TO A LOWER LEVEL...POSSIBLY
900MB. WINDS AT THESE LEVELS WILL BE STRONG THROUGH THE DAY SO
ANTICIPATE WIND SPEEDS STAYING ELEVATED...AT LEAST THROUGH MID
AFTERNOON. WITH THE STRONG WINDS...ANY SNOW THAT CONTINUES TO FALL
THROUGH THE DAY WILL LIKELY BLOW AND DRIFT SO HAVE CONTINUED THE
MENTION OF BLOWING SNOW IN THE FORECAST THROUGH THE MORNING...AND
WITH THESE IMPACTS EXTENDING PAST 12Z OPTED TO EXTEND THE WINTER
WEATHER ADVISORY THROUGH 18Z FOR MUCH OF THE NORTHEAST HALF OF THE
FORECAST AREA WHICH WERE PREVIOUSLY SET TO EXPIRE AT 12Z.

TEMPERATURES WILL NOT RISE MUCH TODAY AS THE COLD AIR FROM THE
ARCTIC HIGH CONTINUES TO FILTER INTO THE FORECAST AREA. DID ADJUST
HIGH TEMPERATURES DOWN A BIT FROM THE PRIOR FORECAST AS MODELS WOULD
SUGGEST WITH MIXING TO 900 OR 850MB...HIGHS IN THE SINGLE DIGITS
OVER THE NORTHEAST WHERE CLOUDS WILL HOLD ON LONGER...TO UPPER TEENS
IN THE SOUTHWEST LOOK APPROPRIATE.

THEN FOR TONIGHT...HIGH PRESSURE AT THE SURFACE WILL SLIDE EAST
WHICH WILL DROP THE WINDS OFF TO LIGHT AND VARIABLE BEFORE SHIFTING
AROUND TO THE SOUTH BY DAYBREAK MONDAY. THE AIR WILL BE VERY DRY SO
NOT ANTICIPATING MUCH IF ANY CLOUD COVER OVERNIGHT...SO FEEL THAT
EVEN WITH A BRIEF PERIOD OF CLEAR SKIES AND LIGHT WINDS...ALONG WITH
THE FRESH SNOWPACK...TEMPERATURES WILL QUICKLY FALL WITH GOOD
RADIATIONAL COOLING OCCURRING. DID DROP LOWS A FEW MORE DEGREES
LOWER...SO NOW LOOKING AT SINGLE DIGITS BELOW ZERO TO SINGLE DIGITS
ABOVE ZERO.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 326 AM CST SUN FEB 1 2015

MONDAY THROUGH TUESDAY NIGHT...A WARM FRONT WILL MOVE INTO THE FCST
AREA MONDAY WITH CHINOOK CONDITIONS DEVELOPING DURING THE AFTN. THE
MODELS SHOW NORTHWEST H850 MB WINDS INCREASING TO 25 TO 30 KT AND
SFC WINDS 15 TO 20 MPH. THIS SHOULD SCOUR OUT THE ARCTIC AIR AND THE
BEST GUESS FOR HIGHS IS LOWER 30S NEAR ONEILL TO NEAR 50 NEAR
IMPERIAL. THE MODELS SHOW SIGNIFICANT MIDLEVEL MOISTURE...CLOUD
COVER AND MIXING HEIGHTS AROUND 500M AGL. THE RISK WITH THE FORECAST
IS THAT TEMPERATURE MAY BE SEVERAL DEGREES COOLER THAN FORECAST.

A SIMILAR STRATEGY IS IN PLACE TUESDAY. ANOTHER ROUND OF MIDLEVEL
CLOUDINESS ASSOCIATED WITH A STRONGER PUSH OF WARM AIR OFF THE
ROCKIES WOULD PRODUCE HIGHS IN THE MID 30S IN THE NORTHEAST NEAR
ONEILL TO MID 50S NEAR IMPERIAL.

THE MODEL CONSENSUS INDICATES AN ARCTIC COLD FRONT WILL DROP INTO
NRN NEB TUESDAY AFTN. THE NAM...SREF AND GEF MODELS WERE SLOWER THAN
THE GFS...ECM AND GEM WAITING UNTIL TUESDAY NIGHT TO BRING THE FRONT
IN. THE SLOWER MODELS HOLD THE FRONT AND THE SNOW ACROSS SOUTH
DAKOTA UNTIL WEDNESDAY MORNING WHILE THE GFS...GEM  AND ECM FLOG THE
FCST AREA WITH SNOW AND SHARPLY COLDER TEMPERATURES TUESDAY NIGHT.

ALL MODELS SHOW AN AREA OF MIXED PRECIPITATION ON THE LEADING EDGE
OF THE SNOW BAND THAT IS EXPECTED TO DEVELOP IN CONJUNCTION WITH THE
RIGHT REAR QUADRANT OF AN UPPER LEVEL JET. MIDLEVEL FRONTOGENESIS
AND MOISTURE 850-500MB WILL FEED A FAST MOVING BAND OF SNOW THAT THE
MODELS SHOW MOVING WEST TO EAST THROUGH THE SRN SANDHILLS. A BRIEF
PERIOD OF RAIN...SLEET OR FREEZING RAIN SHOULD BE EXPECTED GIVEN THE
ARCTIC AIR WILL BE UNDERCUTTING A STRONG THERMAL RIDGE.

WEDNESDAY THROUGH SATURDAY...THE MODELS SHOW THE SNOW ENDING
WEDNESDAY MORNING AND POPS FOR THIS STORM SYSTEM ARE SET AT 50
PERCENT. THE MODEL RUN TO RUN CONTINUITY TONIGHT LOOKS REASONABLY
GOOD. HPC AND THE MODELS SUGGESTED SNOWFALL IN THE RANGE OF 2 TO 4
INCHES TUESDAY NIGHT THROUGH WEDNESDAY MORNING.

ARCTIC AIR WEDNESDAY WILL AT MOST PRODUCE HIGHS IN THE 20S BUT THIS
COULD BE 10 DEGREES TOO WARM WITH H850MB TEMPERATURES -10C TO -15C.
THIS HIGH WILL MOVE QUICKLY EAST AND VERY STRONG THERMAL RIDGING
SHOULD DEVELOP THURSDAY THROUGH SATURDAY. TEMPERATURES SHOULD RISE
INTO THE 30S AND 40S THURSDAY AND ADVANCE INTO THE 40S AND 50S BY
SATURDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 1210 AM CST SUN FEB 1 2015

ONGOING STORM SYSTEM DOMINATES THE FORECAST FOR THE NEXT 24 HOURS.
MODERATE TO HEAVY SNOW WILL CONTINUE TO FALL ACROSS MUCH OF
WESTERN AND NORTH CENTRAL NEBRASKA THROUGH 01.12Z...WHILE SLOWLY
TAPERING OFF FROM THE WEST. IN ADDITION TO THE SNOW...STRONG
NORTHERLY WINDS ARE CAUSING BLOWING SNOW...FURTHER REDUCING
VISIBILITIES EVEN WHERE LIGHTER SNOW IS FALLING. THIS TREND WILL
CONTINUE THROUGH THE MORNING HOURS...AND EXPECT THE IFR CEILINGS TO
PERSIST AT LEAST THROUGH 01.18Z...THEN WILL LIFT THROUGH THE
AFTERNOON. WINDS WILL ALSO DIMINISH LATE IN THE
AFTERNOON...THEREFORE MUCH IMPROVED CONDITIONS ARE EXPECTED FOR
21Z AND BEYOND WITH VFR CEILINGS AND VISIBLITIES AND WINDS
BECOMING LIGHT AND VARIABLE.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 AM CST /5 AM MST/ EARLY THIS
MORNING FOR NEZ004-022-023-025-035>037-056-057-059-094.

WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR NEZ005>010-
026>029-038.

WINTER STORM WARNING UNTIL 5 AM MST EARLY THIS MORNING FOR
NEZ024.

&&

$$

SYNOPSIS...BROOKS/CDC
SHORT TERM...BROOKS
LONG TERM...CDC
AVIATION...BROOKS





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