Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 311734
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1134 AM CST SAT JAN 31 2015

.SYNOPSIS...
ISSUED AT 357 AM CST SAT JAN 31 2015

HIGH PRESSURE IS RIDGING SOUTH FROM MANITOBA INTO NORTH DAKOTA WHILE
LOW PRESSURE EXTENDS FROM AZ INTO COLORADO. A GOOD FETCH OF PACIFIC
MOISTURE AS WELL AS MODIFIED GULF MOISTURE IS BEING DRAWN
NORTHWARD AHEAD OF THE LOW PRESSURE...RESULTING IN OVERCAST SKIES
AND STRATUS INTO SOUTHERN NEBRASKA. SOME LIGHT RAIN OR RAIN/SNOW
MIXED IS WORKING INTO SOUTH CENTRAL NEBRASKA AND A SMALL PART OF
SWRN NEBR ATTM. TEMPERATURES HOLDING IN THE 30S ACROSS MOST OF
NEBRASKA.

&&

.UPDATE...
ISSUED AT 1130 AM CST SAT JAN 31 2015

A BAND OF SNOW...LOCALLY AND BRIEFLY MIXED WITH RAIN...HAS
DEVELOPED ACROSS PORTION OF THE SANDHILLS. THE BAND IS LIFTING TO
THE NORTH SLOWLY. THE LATEST HRRR DIMINISHES THIS BAND OVER THE
NEXT FEW HOURS THEN DEVELOPS THE MAIN BAND ACROSS NORTHERN
NEBRASKA LATER THIS AFTERNOON. THERE IS A POCKET OF DRY AIR IN THE
WATER VAPOR WHICH SHOULD BE ENOUGH TO DIMINISH THE CURRENT BAND.
THE 12Z MODELS DO AGREE IN DEVELOPING THE MAIN BAND ACROSS
NORTHERN NEBRASKA AND A FEW...ESPECIALLY THE NAM...HAS INCREASED
THE QPF AMOUNTS. THE GFS AND THE MAJORITY OF THE SHORT TERM MODELS
ARE NOT DEVELOPING AS MUCH AS THE NAM...HOWEVER THEY HAVE
INCREASED THE START TIME AND EXPANDED THE BAND FURTHER WEST...THUS
FELT IT WAS WARRANTED TO EXPAND THE ADVISORY WESTWARD AND START IT
EARLIER...21Z.

MAJOR CONCERN IS ABOUT THE QPF AMOUNTS /SNOW TOTALS WITH THIS
SYSTEM. WILL CONTINUE TO MONITOR CLOSELY THE SHORT TERM MODEL
UPDATES AND THE 18Z NAM RUN. SNOW TOTALS CURRENTLY EXPECTED ARE
GENERALLY A 3 TO 6 INCH BAND IN THE ADVISORY...WHICH MAY BE
CONSERVATIVE. IF THE NAM VERIFIES...AN UPGRADE TO A WARNING WOULD
BE NEEDED.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 357 AM CST SAT JAN 31 2015

THE LOW PRESSURE SYSTEM ACROSS THE DESERT SOUTHWEST WILL BE DRAWN
INTO KANSAS AND NEBRASKA TODAY AS A NRN STREAM TROUGH MOVES INTO
THE NRN PLAINS. THIS WILL CAUSE AN H7 LOW TO DEVELOP INTO CENTRAL
NEBRASKA BY 18Z. ISENTROPIC UPGLIDE WILL INCREASE TODAY WITH A
TROWAL TO DEVELOP ACROSS THE NEBRASKA SANDHILLS ON THE NWRN
PERIPHERY OF THE H7 LOW. MODEL ARE ALL IN GOOD AGREEMENT WITH THE
PLACEMENT AND TIMING OF THIS FEATURE. SOUNDINGS SHOW A DRY LAYER
NEAR 600MB WHICH WILL LIMIT PRECIP INITIALLY FROM REACHING THE
GROUND. ISENTROPIC LIFT SHOULD BE ABLE TO SATURATE THE LAYER BY
18Z. HAVE SUBSTANTIALLY INCREASED POPS TO LIKELY ACROSS THE
CENTRAL SANDHILLS AND DEFINITE BY LATE AFTERNOON.

ANOTHER CONCERN WILL BE PRECIP TYPE. COOLER AIR FROM THE NORTHERN
SYSTEM DRIFTS SOUTH...WHICH MODELS ARE IN AGREEMENT. KEPT MENTION AS
RAIN OR SNOW THIS MORNING...THEN TO ALL SNOW BY MID AFTERNOON
CENTRAL AND NORTHERN AREAS. A CHANGEOVER COULD OCCUR SOONER. ACROSS
THE SOUTH KEPT MENTION AS RAIN OR SNOW THROUGH THE AFTERNOON.
TEMPERATURES SHOULD REACH TO UPPER 30S TO NEAR 40 SOUTHWEST...WHILE
FALLING INTO THE UPPER 20S MUCH OF THE NCTRL IN THE AFTN DUE TO
DYNAMIC COOLING AND COOLER AIR DROPPING SOUTH. SNOW ACCUMULATIONS OF
1 TO 2 INCHES AND LOCALLY HIGHER ARE POSSIBLE ACROSS THE SANDHILLS
THIS AFTERNOON...WHILE LITTLE OR NO ACCUMULATIONS EXPECTED IN THE
SOUTH.

HEAVIEST ACCUMULATIONS WILL BE TONIGHT ACROSS NCTRL
NEBR...ESPECIALLY EAST OF VALENTINE TO BREWSTER WHERE TOTAL
AMOUNTS OF 3 TO 5 INCHES AND LOCALLY HIGHER ARE POSSIBLE. THE
TROWAL SHOULD REMAIN WELL DEFINED TONIGHT...ENHANCED BY THE
APPROACHING NRN STREAM TROUGH. NORTH WINDS INCREASING TO 15 TO 25
MPH LATE THIS EVENING AND OVERNIGHT EAST OF HWY 83 COULD CAUSE
SOME BLOWING AND DRIFTING WITH REDUCED VISIBILITIES...ESPECIALLY
EAST OF VALENTINE TO BREWSTER. THEREFORE...HAVE ISSUED A WINTER
WEATHER ADVISORY IN EFFECT TONIGHT FOR KEYA
PAHA...BOYD...ROCK...HOLT...GARFIELD AND WHEELER COUNTY. WILL NEED
TO MONITOR DEVELOPMENT OF HEAVIER SNOW BANDS THIS AFTERNOON AND
EVENING...WITH ADJACENT COUNTIES WESTWARD POSSIBLY SEEING HIGHER
AMOUNTS AS WELL. MUCH COLDER AIR WILL BE DRAWN IN TONIGHT WITH
LOWS 8 TO 12 ABOVE ACROSS NCTRL NEBR...15 TO 20 SWRN NEBR.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 357 AM CST SAT JAN 31 2015

FORECAST CONCERNS FOR THE FIRST PORTION OF THE PERIOD LIE WITH
EXITING SNOW CHANCES ON SUNDAY AND TEMPERATURES IN THE WAKE OF THE
SYSTEM FOR SUNDAY AND MONDAY. THE REMAINDER OF THE FORECAST PERIOD
DEALS WITH FAIRLY QUICK NORTHWEST TO QUASI-ZONAL FLOW...LEADING TO
DIFFICULTIES IN TIMING OF INDIVIDUAL SHORTWAVE TROUGHS INVOLVING
TEMPERATURE VARIATIONS AND CHANCES FOR PRECIPITATION.
CURRENTLY...THE HIGHEST CHANCES FOR PRECIPITATION WILL COME
TUESDAY NIGHT AND WEDNESDAY.

THE MODELS ARE IN DECENT AGREEMENT THROUGH THE PERIOD WITH THE
GENERAL PATTERN...BUT DO HAVE SLIGHT DIFFERENCES IN TIMING
PARTICULAR SYSTEMS...WHICH IS EXPECTED IN THIS FLOW REGIME.

FOR SUNDAY AND INTO MONDAY...THE SYSTEM IMPACTING THE AREA TODAY
WILL BE EXITING THE REGION AS THE UPPER LEVEL TROUGH PUSHES INTO
THE MIDDLE MISSISSIPPI RIVER VALLEY REGION. THE COLD FRONT WILL BE
WELL PAST THE AREA BY 12Z SUNDAY AND THE COLD AIR BEHIND IT WILL
BE IN PLACE WITH 850MB TEMPERATURES FROM -10C TO-18C. MODELS ARE
SHOWING GOOD SUBSIDENCE BEHIND THE SHORTWAVE AND WITH A TIGHT
PRESSURE GRADIENT LOOKING FOR BREEZY WINDS...AND WITH THE BOUNDARY
LAYER TO MIXING THROUGH THE DAY COULD GET GUSTS TO 30-35KTS. BY
MID AFTERNOON ALL OF THE SNOW SHOULD BE OUT OF THE AREA. ONE OTHER
MINOR CONCERN IS CHANCES FOR SOME LIGHT SNOW OVER THE EASTERN
PANHANDLE. MODELS ARE INDICATING THERE WILL BE SOME WEAK TO
MODERATE LIFT AS A SECONDARY PV ANOMALY MOVES SOUTH ACROSS THE
AREA. MOISTURE WILL BE WANING THROUGH THE MORNING BUT COULD GET
ENOUGH LIFT...ESPECIALLY OVER THE HIGHER TERRAIN TO INDUCE SOME
LIGHT SNOW. AS FOR TEMPERATURES...WITH THE COLD AIRMASS EXPECTED
LOOKING AT BELOW NORMAL TEMPERATURES. THE NORTHEAST HALF OF THE
FORECAST AREA WILL SEE CLOUDS HANG ON THROUGH MUCH OF THE DAY
WHICH WILL ALSO LIMIT THE TEMPERATURE RISE...WITH HIGHS IN THE LOW
TO MID TEENS. TO THE SOUTHWEST...WHERE MORE SUNSHINE AND DEEPER
MIXING IS EXPECTED...BELIEVE HIGHS IN THE MID TO UPPER 20S ARE
APPROPRIATE.

HIGH PRESSURE AT THE SURFACE SLIDES EAST ACROSS THE FORECAST AREA
SUNDAY NIGHT...BUT BY 12Z MONDAY MORNING IS OFF TO THE EAST WITH
SOUTHERLY RETURN FLOW TAKING OVER. THIS MAY LEAD TO A NON-DIURNAL
TEMPERATURE CURVE OVERNIGHT AS TEMPERATURES WILL LIKELY DROP
QUICKLY AS THE HIGH MOVES OVERHEAD WITH CLEAR SKIES AND LIGHT
WINDS.

ON MONDAY...THE MODELS ARE SHOWING A WEAK SHORTWAVE TROUGH MOVING
ACROSS THE DAKOTAS AND NORTHEAST NEBRASKA IN THE NORTHWEST FLOW.
THIS SYSTEM WILL BRING A WARM FRONT ACROSS THE AREA...WHILE THE
MAJORITY OF THE MODELS ARE KEEPING ANY CHANCES FOR PRECIPITATION
TO THE NORTHEAST OF THE AREA. KEPT THE FORECAST DRY BUT MAY NEED
TO WATCH HOW THIS SYSTEM PROGRESSES OVER THE WEEKEND AS EVEN A
SLIGHTLY MORE AMPLIFIED SYSTEM WOULD LIKELY BRING CHANCES FOR
PRECIPITATION TO PORTIONS OF THE AREA. TEMPERATURES WILL BE A BIT
WARMER FOR MONDAY AND TUESDAY WITH TUESDAY LOOKING TO BE WELL
ABOVE NORMAL FOR PORTIONS OF THE FORECAST AREA. THIS WILL OCCUR
AHEAD OF THE NEXT SYSTEM THAT WILL MOVE ACROSS THE REGION. THE
MODELS ARE IN GOOD AGREEMENT WITH AN UPPER LEVEL SYSTEM COMING OUT
OF NORTHWEST CANADA AND DROPPING THROUGH THE NORTHERN PLAINS LATER
TUESDAY AND WEDNESDAY. THE COLD FRONT IS CURRENTLY TIMED TO PUSH
THROUGH THE FORECAST AREA TUESDAY AFTERNOON. AHEAD OF THE
FRONT...TEMPERATURES SHOULD RISE SIGNIFICANTLY...WITH UPPER 50S
AND 60S POSSIBLE. ACROSS THE NORTH...WHERE THE COLDER AIR MOVES IN
EARLIER...HIGHS MAY BE LIMITED TO 40S...WITH STEADY OR FALLING
TEMPERATURES THROUGH THE AFTERNOON. SNOW CHANCES WILL COME BEHIND
THE PASSAGE OF THE FRONT AS MOISTURE AND LIFT WILL BE LACKING
IMMEDIATELY FOLLOWING. THIS HAS MUCH TO DO WITH THE UPPER JET...AS
IT IS BASICALLY NON-EXISTENT OVER THE REGION UNTIL TUESDAY NIGHT
AND WEDNESDAY. THE FORECAST WILL CONTINUE CHANCES FOR SNOW FOR
TUESDAY NIGHT AND WEDNESDAY...HOWEVER ANY AMOUNTS ARE UNCERTAIN AT
THIS TIME. COLDER TEMPERATURES ARE EXPECTED WITH THIS SYSTEM...BUT
THE MODELS ARE IN GOOD AGREEMENT WITH BUILDING A RIDGE IN OVER THE
ROCKIES AND PLAINS BY THE WEEKEND SO IF THE TREND CONTINUES...NEAR
OR ABOVE NORMAL TEMPERATURES WOULD BE EXPECTED INTO NEXT WEEKEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1130 AM CST SAT JAN 31 2015

COMPLEX AVIATION WEATHER THE NEXT 24 HOURS. A LOW PRESSURE SYSTEM
WILL MOVE ACROSS THE PLAINS WITH WIDESPREAD IFR CONDITIONS.
PLENTIFUL LOW LEVEL MOISTURE WILL RESULT IN MOST AREAS SEEING IFR
CLOUDS INTO TONIGHT...THEN LIFTING OVERNIGHT INTO TOMORROW
MORNING TO MVFR. ALSO EXPECT SNOW TO DEVELOP AND REDUCE
VISIBILITIES TO 3 MILES OR LESS AT TIMES. IN ADDITION TO THE SNOW
WILL BE GUSTY NORTHERLY WINDS /GUSTS 20 TO 30 KTS/ DEVELOPING LATE
TONIGHT INTO THE MORNING HOURS. THIS COULD RESULT IN LOCAL AREAS
OF BLOWING SNOW...HOWEVER UNCERTAIN ABOUT SNOW TOTALS AT THE
TERMINALS RESULTED IN NO BLSN IN THE TAF AT THIS TIME.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 3 PM CST /2 PM MST/ THIS AFTERNOON
TO 6 AM CST /5 AM MST/ SUNDAY FOR NEZ005>010-023>029-094.

&&

$$

UPDATE...MASEK
SYNOPSIS...ROBERG
SHORT TERM...ROBERG
LONG TERM...BROOKS
AVIATION...BROOKS






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