Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 180520 AAB
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1120 PM CST WED DEC 17 2014

.SYNOPSIS...
ISSUED AT 325 PM CST WED DEC 17 2014

AN ACTIVE H5 PATTERN CONTINUES ACROSS THE LOWER 48 TDY
WITH NUMEROUS DISTURBANCES AND A CLOSED LOW NOTED OVER THE CONUS.
CLOSED LOW PRESSURE WAS NOTED OVER LAKE HURON AND EXTENDED WWD INTO
NRN WISCONSIN. HIGH PRESSURE WAS NOTED OVER NRN MANITOBA. ACROSS THE
WESTERN HALF OF THE CONUS...SHORTWAVES WERE NOTED OVER SERN
MT....SWRN NEW MEXICO...AND THE CALIFORNIA DESERT. HT FALLS OF 50 TO
70 METERS EXTENDED FROM EASTERN ARIZONA INTO SWRN KS. IN ASSOCIATION
WITH THE CLOSED LOW OVER THE GREAT LAKES...A NICE 50 TO 90 KT JET
STREAK EXTENDED FROM THE MID MISSOURI RIVER...EAST TO VIRGINIA AND
NORTH CAROLINA. HT FALLS IN ASSOCIATION WITH THE CLOSED LOW WERE
MOST PRONOUNCED OVER NEW ENGLAND...WHERE 50 TO 120 METER FALLS WERE
NOTED. AT THE SURFACE...ARCTIC HIGH PRESSURE WAS ANCHORED ACROSS THE
EASTERN DAKOTAS...SSE INTO MISSOURI. WEST OF THIS FEATURE...WEAK
SERLY WINDS WERE NOTED ALONG WITH PESKY LOW LEVEL CLOUDINESS AND
PATCHY FOG. TEMPERATURES THIS AFTERNOON WERE COLD WITH READINGS IN
THE LOWER 20S ACROSS WESTERN AND NORTH CENTRAL
NEBRASKA.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 325 PM CST WED DEC 17 2014

DESPITE THE MAIN UPPER PV ANOMALY AND ASSOCIATED LARGE SCALE FORCING
IS SOUTH OF THE AREA AND MOVING EASTWARD...SEVERAL FORECASTING
ISSUES REMAIN. THE STRATUS LAYER IS WARM ENOUGH TO CONTAIN
SUPERCOOLED LIQUID AND HENCE FALL TO THE GROUND IN WEAK UPSLOPE FLOW
AS FREEZING DRIZZLE IN SOME AREAS OF SOUTHWEST NEBRASKA THIS
AFTERNOON. RAP BUFR SOUNDINGS SUGGEST MINIMAL LIFT THROUGH THE
REMAINING AFTERNOON HOURS...BUT INCREASING SLIGHTLY THIS EVENING AND
OVERNIGHT. IR SAT PICS SHOW MID LEVEL CLOUDS TRYING TO MOVE OVER THE
TOP OF THE EXISTING LOW LEVEL STRATUS BUT HAVING A HARD TIME AS MID
LEVELS ARE QUITE DRY INITIALLY. BELIEVE THE INCREASING UPWARD
VERTICAL MOTION AS A RESULT OF WEAK MID LEVEL FRONTOGENESIS WILL
EVENTUALLY HELP TO MOISTEN THE MID LEVELS...BUT SOUNDINGS STILL SHOW
TOO MUCH DRY AIR TO CONNECT A SATURATED SNOW PRODUCING LAYER WITH
THE MOIST LOW LEVELS BELOW. THE END RESULT...BASED ON FORECAST
SOUNDINGS...WILL BE FREEZING DRIZZLE ESPECIALLY ACROSS THE SOUTHWEST
PORTION OF NEBRASKA THIS EVENING AND DURING THE OVERNIGHT. NEAR TERM
ENSEMBLES SUGGEST THE POSSIBILITY OF A SMALL BAND OF LIGHT SNOW FROM
SOUTHEAST FRONTIER COUNTY NORTHEASTWARD INTO CUSTER...BUT CONFIDENCE
IN SUCH A SMALL SCALE FEATURE BEING ABLE TO FULLY SATURATE THE
ATMOSPHERIC COLUMN TO SUPPORT LIGHT SNOW IS NOT HIGH...SO HAVE LEFT
PRECIPITATION MENTION AS FREEZING DRIZZLE FOR NOW.

FURTHER NORTH AND WEST...SOUTHERLY AND SOUTHEASTERLY WINDS WILL
CONTINUE TO SUSTAIN MOIST LOW LEVELS IN THE EASTERN PANHANDLE...BUT
MID AND UPPER LEVEL DRYING WILL BE GREATER HERE WHICH LEAVES A
BETTER SCENARIO FOR FOG AND HAVE THEREFORE INCLUDED THAT MENTION
THERE INTO THE MORNING HOURS. FOG WILL BE OCCURRING IN SNOW COVERED
AREAS WHICH WILL MEAN SOME DEPOSITION ON ROADS WILL BE POSSIBLE SO
THE MENTION OF FREEZING FOG WAS INCLUDED.

TOMORROW AFTERNOON CLOUDS WILL THIN ALTHOUGH STILL HAVE MUCH OF THE
AREA WITH A SNOW PACK. THIS WILL LIMIT THE ABILITY TO WARM...WITH
TEMPS STRUGGLING TO REACH FREEZING. SOME PARTIAL SUN IS EXPECTED
ACROSS WESTERN NEBRASKA THANKS TO SOME WESTERLY DOWNSLOPING WINDS
WHICH IS WHERE FORECAST HIGHS ARE THE WARMEST.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 325 PM CST WED DEC 17 2014

MID RANGE...THURSDAY NIGHT THROUGH SATURDAY...THE MAIN
FORECAST CHALLENGES IN THE MID RANGE ARE THE THREAT FOR FREEZING
DRIZZLE THURSDAY NIGHT INTO FRIDAY MORNING...AS WELL AS CLOUD COVER
AND TEMPERATURES. FOR THURSDAY NIGHT...WITH THE EXCEPTION OF THE FAR
NORTHWESTERN CWA...LOW CLOUDS AND AN ARCTIC DRAPE WILL REMAIN
ENTRENCHED ACROSS THE BULK OF THE FORECAST AREA. BOTH THE NAM AND
GFS SOLNS THIS MORNING PER FCST SOUNDINGS ARE INDICATING A NICE
LAYER OF NEAR 100 PERCENT RH FROM THE SURFACE TO 1000 TO 1500FT AGL.
WITHIN THIS LAYER...WEAK VEERING OF THE WINDS ARE PRESENT ALONG WITH
SOME WEAK OMEGA AND TEMPERATURES RANGING FROM ZERO TO -5C IN THIS
MOIST LAYER. IN ADDITION...WARMING AND DRYING IS INDICATED PER
FORECAST SOUNDINGS ABOVE THE MOIST LAYER DURING THE PERIOD. ALL
TOLD...THIS IS A DECENT SETUP FOR FREEZING DRIZZLE AND HAVE
INTRODUCED IT IN THE GRIDS. DURING THE EVENING HOURS...WITH THE
EXCEPTION OF THE PANHANDLE COUNTIES AND FAR NORTHWEST...CONDS WILL
BE FAVORABLE FOR FZDZ. THIS AREA WILL SHRINK EAST INTO THE OVERNIGHT
HOURS AND MORNING PERIOD FOR FRIDAY. BY FRIDAY AFTERNOON...MOSTLY
CLEAR SKIES IN THE CENTRAL AND WEST...AND PARTLY CLOUDY SKIES IN THE
EAST ARE EXPECTED. THIS WILL ALLOW TEMPS TO REACH THE LOWER TO
MIDDLE 30S FRIDAY...EFFECTIVELY ENDING THE FREEZING DRIZZLE THREAT.
ON FRIDAY NIGHT AND SATURDAY...FORECAST SOUNDINGS OVER THE EASTERN
THIRD OF THE FORECAST AREA ARE INDICATIVE OF ANOTHER EPISODE OF
FREEZING DRIZZLE LATE FRIDAY NIGHT INTO SATURDAY MORNING. ATTM...THE
THREAT FOR FREEZING DRIZZLE IS INDICATED ONLY IN THE NAM SOLN AS THE
GFS IS MORE AGGRESSIVE IN PUSHING THE ARCTIC AIRMASS EAST FRIDAY
NIGHT. GIVEN THE MODEL DIFFERENCES...WILL HOLD OFF ON MENTION OF
FREEZING DRIZZLE ATTM. ON SATURDAY...AN UPPER LEVEL DISTURBANCE
ACROSS THE NRN TIER OF STATES...WILL FORCE WARMER AIR INTO THE
FORECAST AREA...FOLLOWED BY A WEAK COOL FRONT SATURDAY NIGHT. LIGHT
WESTERLY WINDS SATURDAY WILL PUSH HIGHS INTO THE LOWER 40S.

SUNDAY THROUGH WEDNESDAY...AS THE UPPER LEVEL SYSTEM PUSHES EAST
MONDAY AND MONDAY NIGHT...THERE WILL BE AN INCREASED THREAT FOR LIGHT
PRECIPITATION IN THE FAR NORTHEAST...ALONG WITH A THREAT FOR
PRECIPITATION ACROSS THE CENTRAL AND NORTHERN ROCKIES...WHICH WILL
BE ENHANCED BY A STRONG UPPER LEVEL JET STREAK. BEYOND MONDAY
NIGHT...A DRY AND COLDER FORECAST IS EXPECTED ACROSS WESTERN AND
NORTH CENTRAL NEBRASKA AS ARCTIC AIR PUSHES SOUTH TUESDAY INTO
WEDNESDAY. ATTM...THE BEST THREAT FOR SNOW WILL BE OFF TO THE WEST
OF THE FORECAST AREA...HOWEVER...WE WILL NEED TO MONITOR NEXT
THURSDAY INTO NEXT WEEKEND AS THE LATEST ECMWF SOLN DIGS A DEEP
TROUGH INTO THE INTERMOUNTAIN WEST BY DAY 10.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1120 PM CST WED DEC 17 2014

A CLEARING LINE SHOULD BECOME ESTABLISHED ALONG OR NEAR HIGHWAY 83
THURSDAY.

LIFR/IFR CIGS AND VSBY CONTINUE OVERNIGHT AND IMPROVE TO VFR 18Z-
21Z ALONG AND WEST OF HIGHWAY 61. LIFR/IFR/MVFR CIGS CONTINUE ALONG
AND EAST OF HIGHWAY 83 THROUGH THURSDAY EVENING.

&&

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

$$

SYNOPSIS...CLB
SHORT TERM...MASEK/JWS
LONG TERM...CLB
AVIATION...CDC






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