Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 161740
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1140 AM CST SUN NOV 16 2014

.SYNOPSIS...
ISSUED AT 407 AM CST SUN NOV 16 2014

THE H5 PATTERN ACROSS NORTH AMERICA TONIGHT REMAINS LARGELY
UNCHANGED FROM LAST NIGHT. A HIGH AMPLITUDE RIDGE EXTENDS UP THE
WEST COAST OF CANADA INTO THE YUKON AND EASTERN ALASKA. STRONG LOW
PRESSURE WAS PRESENT ACROSS HUDSON BAY....WITH A BROAD TROUGH OF
LOW PRESSURE PRESENT ACROSS THE CONUS. ACROSS THE CENTRAL PLAINS
AND CENTRAL ROCKIES...AN HORIZONTAL ORIENTED TROUGH OF LOW
PRESSURE EXTENDED FROM THE DAKOTAS WEST TO EASTERN OREGON. SOUTH
OF THIS FEATURE...ABUNDANT CLOUDINESS EXTENDED FROM SERN
UTAH...EAST ACROSS COLORADO...KANSAS AND INTO THE MID MISSISSIPPI
VALLEY. NORTH OF THIS FEATURE...CLEAR SKIES WERE NOTED ACROSS THE
NORTHERN PLAINS AND ROCKIES. THE EXCEPTION WAS ACROSS NORTHERN
MONTANA...WHERE INCREASED CLOUD COVER WAS NOTED IN ASSOCIATION
WITH AN APPROACHING ARCTIC COLD FRONT. MORE ABOUT THAT IN THE
SHORT TERM SECTION. AT THE SURFACE..HIGH PRESSURE WAS PRESENT FROM
SWRN MONTANA...SE INTO WYOMING AND WESTERN NEBRASKA. UNDER MOSTLY
CLEAR SKIES...3 AM CST TEMPERATURES RANGED FROM 5 ABOVE AT
OGALLALA...TO 11 BELOW ZERO AT VALENTINE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 407 AM CST SUN NOV 16 2014

OVER THE NEXT 24 HOURS...THE THREAT FOR LIGHT SNOW TONIGHT...AS
WELL AS BLOWING SNOW POTENTIAL THIS AFTERNOON AND TONIGHT...ALONG
WITH TEMPERATURES WILL BE THE MAIN FORECAST CONCERNS OVER THE NEXT
24 HOURS. FOR TODAY...A STRONG SHORTWAVE ROTATING AROUND THE
WESTERN PERIPHERY OF THE HUDSON BAY LOW...WILL FORCE AN ARCTIC
FRONT SOUTH INTO THE DAKOTAS AND NEBRASKA BY 00Z MONDAY. IN
ADVANCE OF THIS FEATURE...WESTERLY WINDS WILL INCREASE ACROSS THE
FORECAST AREA AS HIGH PRESSURE DROPS SOUTH OF THE FORECAST AREA.
THESE WESTERLIES WILL ABRUPTLY SHIFT TO THE NORTH AND NORTHWEST BY
LATE AFTERNOON AS THE ARCTIC FRONT PUSHES INTO NORTHERN AND
CENTRAL NEBRASKA. THIS FEATURE IS EXPECTED TO PASS THROUGH THE
ENTIRE FORECAST AREA BY SUNSET. WITH THE STRONG COLD AIR ADVECTION
BEHIND THE FRONT...STRONG NORTHERLY WINDS ARE EXPECTED WITH H925
WINDS BEHIND THE FRONT RANGING FROM 20 TO 35 KTS. WITH FRESH
SNOW COVER IN THE 2 TO 6 INCH RANGE PRESENT ACROSS THE NORTH
CENTRAL AND NWRN THIRD OF THE FORECAST AREA...BLOWING SNOW WILL BE
A CONCERN DURING THE PERIOD. ATTM...AM LEANING HEAVILY TOWARD
ISSUING A WINTER WEATHER ADVISORY FOR BLOWING SNOW...OVER NORTHERN
NEBRASKA AND WOULD BEGIN IT AROUND MIDDAY...CONTINUING IT
OVERNIGHT THROUGH 12Z MONDAY. IN ADDITION TO BLOWING SNOW...THE
THREAT FOR FLURRIES AND LIGHT SNOW WILL BE POSSIBLE AS WELL. WITH
RESPECT TO LIGHT SNOW...CROSS SECTIONS ACROSS NORTHWESTERN
PORTIONS OF THE CWA INVOF THE PINE RIDGE...INDICATE A SHALLOW AREA
OF LIFT FROM H850 TO H750 WHICH IS IN A NEAR SATURATED LAYER.
TEMPERATURES WITHIN THIS LAYER ARE AROUND -15C BEHIND THE
FRONT...WHICH WOULD BE FAVORABLE FOR EFFICIENT DENDRITIC GROWTH OF
SNOW. IN ADDITION...NORTHWESTERLY WINDS IN THE PINE RIDGE ARE
FAVORABLE FOR SNOW GIVEN THE WEAK UPGLIDE POTENTIAL. IN THESE
AREAS...INCREASED POPS TONIGHT INTO THE 30 TO 40 PERCENT RANGE
WITH AROUND AN INCH OF SNOW FORECAST IN THE GRIDS. ELSEWHERE...THE
STRONG CAA BEHIND THE FRONT...WILL BE FAVORABLE FOR FLURRIES...AND
PLACED THESE WHERE FCST H900 TO H850 LAYER RH WAS GREATER THAN 90
PERCENT. SPATIALLY...THIS FCST OF FLURRIES IS IN ALL LOCATIONS
EXCEPT THE SWRN CWA WHERE TEMPERATURES ARE TOO WARM IN THE MOIST
LAYER TO SUPPORT DECENT DENDRITIC GROWTH OF FLURRIES OR LIGHT
SNOW. TEMPERATURES TODAY WILL RISE INTO THE 20S AHEAD OF THE APPG
FRONT...WITH SOME READINGS AROUND 30 IN THE FAR SOUTHWEST WHERE NO
SNOW COVER EXISTS. FOR TONIGHT...LOWS WILL BE IN THE SINGLE DIGITS
TO AROUND ZERO AS WINDS AND CLOUDS WILL KEEP TEMPERATURES SOMEWHAT
ELEVATED FROM CURRENT TEMPS TONIGHT.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 407 AM CST SUN NOV 16 2014

THE PRIMARY FORECAST CONCERNS ARE TEMPERATURES THROUGHOUT THE
PERIOD WITH BELOW NORMAL READINGS EXPECTED INTO NEXT WEEKEND.

MODELS ARE IN GOOD AGREEMENT WITH THE LARGE-SCALE PATTERN ALTHOUGH
DO HAVE SOME TIMING DIFFERENCES IN MINOR WEAK SHORTWAVES PASSING
ACROSS NEBRASKA. THESE TIMING DIFFERENCES HAVE THE PRIMARY IMPACT
IN THE FORECAST WITH DETERMINING CHANCES FOR FLURRIES AND CLOUD
COVER...BUT ALSO HAVE AN IMPACT ON THE TEMPERATURE FORECAST.

THE PERIOD BEGINS MONDAY MORNING WITH THE HIGHLY AMPLIFIED UPPER
LEVEL PATTERN HAVING CHANGED LITTLE FROM THE CURRENT TIME...AS
STRONG RIDGING WILL BE IN PLACE ACROSS THE WEST COAST INTO ALASKA
WITH A DEEP TROUGH OVER MUCH OF THE REST OF THE CONUS...WITH THE
AXIS FROM SOUTHWEST ONTARIO INTO TEXAS. THE MORNING STARTS OFF
QUITE COLD AND BREEZY AS THE FORECAST AREA IS IN THE WAKE OF A
POTENT SHORTWAVE TROUGH THAT WILL HAVE PUSHED SOUTH ACROSS
NEBRASKA OVERNIGHT. THE NAM IS ONE OF THE COLDER SOLUTIONS DURING
THE DAYTIME HOURS...ALTHOUGH ALL MODELS DO START PUSHING THE
COLDER AIR TO THE EAST BY THE END OF THE DAY. THE NAM DOES KEEP
850MB TEMPERATURES ACROSS THE ENTIRE FORECAST AREA UNDER 10C
BELOW ZERO...WHILE THE ECMWF AS A WARMER SOLUTION BRINGS
TEMPERATURES AT 850MB UP TO 8C BELOW ZERO. ALSO EXPECTING A DECENT
AMOUNT OF CLOUD COVER...ESPECIALLY ACROSS THE NORTHERN AND EASTERN
PARTS OF THE FORECAST AREA TO AND ALTHOUGH THE AIR WILL BE
GENERALLY SUBSIDENT IN NATURE...EVEN A SLIGHT BIT OF LIFT SHOULD
BE ABLE TO SQUEEZE OUT SOME FLURRIES AS TEMPERATURES JUST OFF THE
SURFACE ARE IN THE DENDRITIC GROWTH ZONE. HIGH PRESSURE WILL BUILD
IN THROUGH THE DAY FROM THE NORTHWEST WHICH WILL BROADEN THE
PRESSURE GRADIENT AT THE SURFACE..BUT FORECAST SOUNDINGS INDICATE
LOW LEVEL MIXING TO NEAR 875MB WHERE WINDS WILL BE AROUND 20-30KTS
SO COULD STILL BE A BREEZY AND COOL DAY. HIGHS MONDAY WILL LIKELY
VARY FROM THE LOW TEENS TO THE MID 20S...BUT WITH THE WINDS
EXPECTED...WIND CHILLS LOOK TO STAY IN THE SINGLE DIGITS ABOVE AND
BELOW ZERO.

MONDAY NIGHT THE SURFACE HIGH STAYS OFF TO THE SOUTH AND WEST
WHICH WILL KEEP ENOUGH OF A PRESSURE GRADIENT SO WINDS SHOULD NOT
DROP OFF TO CALM. HOWEVER SKIES WILL BE MOSTLY CLEAR SO ALTHOUGH
IT DOESN/T LOOK LIKE A STRONG CASE FOR RADIATIONAL COOLING...WILL
GET SOME OF THIS EFFECT. LOCATIONS WITH THE SNOW COVER AND OTHER
VALLEY LOCATIONS WILL SEE THE COLDEST READINGS...WITH LOWS IN THE
SINGLE DIGITS ABOVE AND BELOW ZERO. EVEN WITH THE LOWER
WINDS...THEY WILL COMBINE WITH THE VERY COLD TEMPERATURES TO DROP
WIND CHILLS DOWN IN THE TEENS BELOW ZERO.

THE UPPER LEVEL PATTERN BEGINS TO SHIFT SLIGHTLY ON TUESDAY AS THE
UPPER LOW OVER THE GREAT LAKES PULLS TO THE NORTHEAST WHICH BEGINS
TO DE-AMPLIFY THE TROUGH A BIT. THIS ALLOWS WARM AIR ADVECTION TO
OCCUR AS WEAK SHORTWAVE RIDGING BUILDS IN AND THE MAIN SHORTWAVE
TRACK SITS OFF TO THE EAST. THE GFS SHOWS 850MB TEMPERATURE RISING
TO AROUND 5C ACROSS MUCH OF THE FORECAST AREA ON TUESDAY WHILE THE
ECMWF AND GFS AREN/T QUITE THAT WARM. DID INCREASE THE HIGHS A FEW
DEGREES...ESPECIALLY OVER THE WESTERN PART OF THE FORECAST AREA
WHERE IT IS MORE LIKELY THAT THE WARM AIR WILL MOVE INTO.

THIS WARMER AIR INTRUSION IS SHORT LIVED AS ANOTHER WEAK SHORTWAVE
TROUGH MOVES SOUTHEAST ACROSS NEBRASKA TUESDAY NIGHT PUSHING A
COLD FRONT THROUGH THE FORECAST AREA...ALONG WITH ANOTHER BATCH OF
COLDER AIR. THERE ARE SOME DIFFERENCES WITH THE TIMING OF THIS
SYSTEM...ALONG WITH SOME OF THE DYNAMICS AS THE NAM SUGGESTS A BIT
MORE MOISTURE AND LIFT AND THEREFORE PRODUCES SOME LIGHT
PRECIPITATION. THINKING ANY SNOW WOULD BE FLURRIES BUT AT THIS
POINT DIDN/T ADD ANY TO THE FORECAST AS CONFIDENCE IS FAIRLY LOW.

THE LAST STRONG ARCTIC SYSTEM OF THE WEEK TO MOVE THROUGH COMES
THURSDAY AND THURSDAY NIGHT. THE MODELS ARE SHOWING THE SURFACE
HIGH DROPPING SOUTH THURSDAY NIGHT...AND THE ECMWF HAS IT CENTERED
OVER NEBRASKA AT 12Z FRIDAY. THIS COULD BE ANOTHER REAL COLD
MORNING. AT THIS TIME THE FORECAST ISN/T PARTICULARLY COLD SO IF
THIS TREND CONTINUES TEMPERATURES WILL LIKELY NEED TO BE LOWERED.
THE MODELS THEN DO SHOW THE PATTERN QUICKLY CHANGING TO MORE OF A
ZONAL...AND MORE PROGRESSIVE PATTERN THROUGH THE WEEKEND. THIS
WOULD MEAN PACIFIC SYSTEMS MOVING THROUGH RATHER THAN ARCTIC
SYSTEMS...SO A WARM UP. HOWEVER...THE MODELS MAY BE CHANGING THE
PATTERN A BIT TOO FAST SO CONFIDENCE IS NOT REAL HIGH ON THIS
HAPPENING BY SATURDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1140 AM CST SUN NOV 16 2014

DETERIORATING FLIGHT CONDITIONS ANTICIPATED FROM NORTH TO SOUTH
THIS AFTERNOON WITH THE PASSAGE OF A STRONG ARCTIC FRONT. MODEL
GUIDANCE IS STRONG IN THAT WIND GUSTS IN EXCESS OF 35KTS ARE
POSSIBLE FOR ALL AREA TERMINALS THIS AFTERNOON AND INTO THE
EVENING. WHERE FRESH SNOWFALL OCCURRED YESTERDAY...BLSN MAY
BECOME AN ISSUE. THE MOST LIKELY TERMINALS WHERE BLSN IMPACTS
AVIATION TRAVEL WILL BE KVTN...KANW...AND/OR KONL. TAKING A WAIT
AND SEE APPROACH WITH THE BLOWING SNOW POTENTIAL...BUT UPDATES TO
VISIBILITY ARE ANTICIPATED LATER THIS AFTERNOON. CEILINGS WILL
LOWER BEHIND THE FRONT...WITH LIGHT SNOW AND/OR FLURRIES POSSIBLE
THIS EVENING AND OVERNIGHT FOR ALL TERMINALS NORTH OF A KLBF TO
KOGA LINE.

&&

.HYDROLOGY...
ISSUED AT 407 AM CST SUN NOV 16 2014

ICE JAMMING WILL CONTINUE THIS WEEK AS TEMPERATURES REMAIN COLD.
THERE ARE SEVERAL DAYS WITH TEMPERATURES RISING ABOVE FREEZING
DURING THE DAYTIME HOURS...BUT WITH HIGHS ONLY IN THE UPPER 30S
TO MID 40S DON/T KNOW HOW MUCH MELTING OF THE ICE WILL OCCUR AND
WITH LOWS DROPPING BACK BELOW FREEZING AT NIGHT THINK THE ICE JAMS
WILL STAY IN PLACE FOR MUCH OF THIS WEEK. THERE HAS BEEN REPORTS
OF WATER FROM THE SOUTH PLATTE RIVER BACKING UP OUT OF THE BANKS
IN AREAS AROUND NORTH PLATTE. THE READING AT THE GAGE SITE IS
SEVERAL FEET BELOW FLOOD STAGE...BUT WITH THE NATURE OF ICE JAMS
THAT DOES NOT NECESSARILY MEAN THERE IS NO FLOODING ONGOING IN
NEARBY AREAS...ESPECIALLY UPSTREAM WHERE WATER IS ABLE TO SPREAD.
AT THIS TIME ONLY SOME MINOR FLOODING OF LOW LYING AREAS ALONG THE
RIVER IS EXPECTED. THE SAME IS OCCURRING ALONG THE NORTH PLATTE
RIVER NEAR LEWELLEN. BOTH LOCATIONS HAVE ONGOING FLOOD ADVISORIES
IN PLACE.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 AM CST /5 AM MST/ MONDAY FOR
NEZ004>006-008-009-094.

&&

$$

SYNOPSIS...CLB
SHORT TERM...CLB
LONG TERM...BROOKS
AVIATION...JACOBS
HYDROLOGY...BROOKS








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