Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 232156
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
356 PM CST SUN NOV 23 2014

.SYNOPSIS...
ISSUED AT 356 PM CST SUN NOV 23 2014

H5 ANALYSIS THIS MORNING CONTINUES TO SHOW AN ACTIVE
PATTERN ACROSS NOAM. THREE UPPER LEVEL LOWS WERE NOTED...ONE SOUTH
OF GREENLAND...A SECOND NORTHWEST OF HUDSON BAY...AND A THIRD OVER
THE EASTERN ALEUTIANS OF ALASKA. FURTHER SOUTH...THREE SHORTWAVES
WERE NOTED...THE FIRST OVER SRN SASKATCHEWAN...THE SECOND OVER SRN
UTAH...AND THE THIRD NEAR HOUSTON TX. THE PATTERN ACROSS THE
CONUS REMAINS PROGRESSIVE AS CURRENT WV IMAGERY HAS THESE
DISTURBANCES OVER NRN ND...NWRN NM...AND MISSISSIPPI RESPECTIVELY.
AT THE SURFACE...LOW PRESSURE WAS LOCATED OVER THE ARROWHEAD OF
MINNESOTA WITH A PACIFIC FRONT EXTENDING SSW INTO THE OZARKS. WEST
OF THE LOW...AN ARCTIC COLD FRONT EXTENDED INTO NORTHERN NORTH
DAKOTA. WINDY CONDITIONS WERE PRESENT ACROSS WESTERN AND NORTH
CENTRAL NEBRASKA THIS AFTERNOON WITH GUSTS AS HIGH AS 40 MPH AS OF 2
PM CST. SKIES WERE MOSTLY CLEAR IN THE CENTRAL AND WEST...WITH
MOSTLY CLOUDY SKIES PRESENT IN THE EAST. TEMPERATURES AS OF 3 PM CST
RANGED FROM 44 TO AINSWORTH TO 49 AT NORTH PLATTE AND BROKEN
BOW.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 356 PM CST SUN NOV 23 2014

FORECAST CONCERNS FOR TONIGHT AND MONDAY DEAL WITH LIGHT SNOW
CHANCES TONIGHT OVER NORTHERN NEBRASKA...WINDS THROUGHOUT THE
PERIOD...THEN CHANCES FOR SNOW AGAIN ON MONDAY AFTERNOON OVER THE
PINE RIDGE.

AN UPPER LEVEL PV ANOMALY WAS MOVING INTO NORTHERN NEBRASKA LATE
THIS AFTERNOON WHICH WILL BE USHERING A COLDER AIRMASS INTO THE
REGION FROM THE NORTH. ANOTHER WEAK DISTURBANCE ALOFT WILL PUSH
SOUTH OVERNIGHT FROM EASTERN NORTH DAKOTA DOWN INTO EASTERN SOUTH
DAKOTA TONIGHT. THE SURFACE COLD FRONT ASSOCIATED WITH THIS FEATURE
IS CURRENTLY OVER NORTH DAKOTA AND WILL PUSH INTO NORTHERN NEBRASKA
THIS EVENING THEN ACROSS MUCH OF THE FORECAST AREA BY 12Z MONDAY. AT
THAT POINT IT WILL BECOME FAIRLY STATIONARY...FROM SOUTHWEST SOUTH
DAKOTA INTO SOUTH CENTRAL NEBRASKA...KEEPING THE COLDER AIR ACROSS
THE EASTERN TWO-THIRDS OF THE STATE.

MOISTURE IN THE LOW LEVELS WILL MOVE SOUTH INTO NORTHERN NEBRASKA
TONIGHT ALONG AND BEHIND THE COLD FRONT. MODELS ARE SHOWING THE
MOISTURE BEING FAIRLY SHALLOW...GENERALLY BELOW 700MB...BUT THERE
APPEARS TO BE ENOUGH OF AN OMEGA SIGNAL IN THAT LAYER TO DEVELOP
PRECIPITATION. LOOKING AT THE TEMPERATURE PROFILE...THE SATURATED
LAYER DOES EXTEND ABOVE THE LEVEL OF -10 DEGREE TEMPERATURES SO ICE
WILL BE INTRODUCED SO ANTICIPATE SNOW TO BE THE PRECIPITATION TYPE.
THE DEEPER MOISTURE AND LIFT DOESN/T PERSIST LONG SO ONLY
ANTICIPATING A FEW HOURS OF SNOW POTENTIAL BEFORE THE AREA JUST
BECOMES INUNDATED WITH STRATUS. TRIED TO TIME THIS OUT OVERNIGHT IN
THE FORECAST WITH THE HIGHEST CHANCES CENTERING AROUND 03Z.
TIME-HEIGHT CROSS SECTIONS SHOW THE LOW LEVEL MOISTURE STICKING
AROUND THROUGH MONDAY MORNING AND FROM LOOKING AT THE CURRENT
SATELLITE IMAGERY THAT LOOKS APPROPRIATE AS STRATUS EXTENDS FROM
BEHIND THE COLD FRONT IN NORTH DAKOTA UP INTO MANITOBA AND
SASKATCHEWAN.

A TIGHT PRESSURE GRADIENT ACROSS THE PLAINS WILL STAY IN PLACE
THROUGH TONIGHT AND MONDAY TO KEEP WINDS FROM DROPPING OFF...WHICH
WILL ALSO KEEP THE BOUNDARY LAYER MIXED. DESPITE COLD AIR ADVECTION
OCCURRING TONIGHT BEHIND THE COLD FRONT...ESPECIALLY OVER NORTH
CENTRAL NEBRASKA WHERE 850MB TEMPERATURES DROP TO NEAR
-10C...THINKING THE LOWS TONIGHT WILL NOT FALL SIGNIFICANTLY DUE TO
THE WINDS. FORECAST SOUNDINGS KEEP THE BOUNDARY LAYER MIXED TO THE
POINT OF KEEPING GUSTS OF 25-30KTS THROUGHOUT THE OVERNIGHT HOURS.
WHILE JUST ABOVE THIS LAYER WINDS WILL CONTINUE TO BLOW AT 40-50KTS.

THE MIXING LAYER INCREASES DURING THE DAY MONDAY SO EXPECTING AN
INCREASE IN WINDS BY AFTERNOON...BUT MAY SEE A SLIGHT DECREASE BY
LATER IN THE DAY AS WINDS ALOFT BEGIN TO DECREASE. WILL STILL BE
ANOTHER WINDY DAY...ESPECIALLY OVER THE EASTERN PART OF THE FORECAST
AREA AS WINDS IN THE MIXED LAYER ARE UP TO 35KTS. THINKING HIGHS
MONDAY WILL BE A BIT COOLER AS TEMPERATURES ALOFT AT 850MB ARE 2-5
DEGREES COOLER THAN WHAT IS OCCURRING TODAY DUE TO THE COLD AIR
ADVECTION BEHIND THE COLD FRONT. SO 30S AND LOW TO MID 40S ARE
EXPECTED. THE OTHER THING TO LOOK AT IS PRECIPITATION CHANCES MONDAY
IN THE NORTHERN PANHANDLE. MODELS ARE SHOWING A WEAK MID-LEVEL
SHORTWAVE TROUGH MOVING INTO THE NEBRASKA PANHANDLE MONDAY
AFTERNOON. SOME INCREASED UPWARD MOTION WITH THIS ENERGY WILL BE IN
PLACE WHILE MOISTURE ALSO IS PUSHED INTO THE AREA. ALSO...OROGRAPHIC
LIFT ASSOCIATED WITH THE PINE RIDGE IN THE NORTHWEST LOW LEVEL FLOW
SHOULD BRING SOME ENHANCED LIFT TO THAT AREA. MOISTURE LOOKS TO BE
SUFFICIENT OVER THE NORTHERN PANHANDLE INTO NORTHWESTERN CHERRY
COUNTY TO ALLOW THIS ENHANCED LIFT TO PRODUCE PRECIPITATION. THE
TEMPERATURE PROFILE WOULD SUGGEST IT WILL BE COLD ENOUGH FOR SNOW SO
HAVE ADDED IN CHANCES FOR SNOW OVER THESE AREAS PRIMARILY ON MONDAY
AFTERNOON.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 356 PM CST SUN NOV 23 2014

MID RANGE...MONDAY NIGHT THROUGH WEDNESDAY...IN THE MID
RANGE PERIODS...THE MAIN FORECAST CHALLENGES ARE PRECIPITATION
CHANCES MONDAY NIGHT...THEN PRECIPITATION CHANCES TUESDAY NIGHT AND
WEDNESDAY IN ASSOCIATION WITH A CLIPPER SYSTEM. FOR MONDAY NIGHT...A
WEAK EMBEDDED DISTURBANCE WILL DROP SOUTH FROM WESTERN SOUTH DAKOTA
APPG THE NEBRASKA PANHANDLE DURING THE LATE AFTERNOON HOURS. CROSS
SECTIONS TAKEN ACROSS SHERIDAN AND NORTHWESTERN CHERRY
COUNTY...INDICATE SOME LIFT AROUND H7...WHICH IS COLLOCATED WITH
DECENT LOW TO MID LEVEL MOISTURE. TEMPERATURES WITHIN THIS MOIST
LAYER ARE FAVORABLE FOR SNOW PRODUCTION MONDAY EVENING. ISENTROPIC
LIFT IN THIS LAYER IS FAIRLY WEAK PER THE 290K SURFACE...HOWEVER
COND PRESSURE DEFICITS ARE UNDER 5MB AT THIS SURFACE...SO MEAGER
LIFT MAY LEAD TO PCPN. ADDTL SUPPORT FOR LIGHT SNOW LIES IN THE
NORTHWESTERLY LOW LEVEL WINDS MONDAY EVENING...WHICH WILL FAVOR
OROGRAPHIC LIFT IN THE PINE RIDGE. WITH THIS IN MIND...INTRODUCED
SOME SLIGHT CHANCE POPS FOR MONDAY EVENING IN THE NWRN CWA. FCST
QPF`S WILL BE VERY LIGHT PER BUFKIT SOUNDINGS WITH ONLY A COUPLE OF
HUNDREDTHS FORECAST. A WEAK SURFACE TROUGH WILL LIFT ACROSS THE
EASTERN DAKOTAS INTO NORTHEASTERN NEBRASKA OVERNIGHT MONDAY NIGHT.
NO PRECIPITATION IS EXPECTED WITH THIS FEATURE...HOWEVER...WESTERLY
WINDS WILL PERSIST INTO THE OVERNIGHT BEHIND THE EXITING TROUGH.
THIS WILL HELP TO KEEP LOWS IN THE 20S. ON TUESDAY...A
SECOND...STRONGER CLIPPER SYSTEM WILL DROP SOUTHEAST FROM SRN
SASKATCHEWAN INTO SOUTHERN NORTH DAKOTA. WESTERLY WINDS WILL
INCREASE IN ADVANCE OF THIS FEATURE...LEADING TO GOOD MIXING
POTENTIAL ACROSS THE FORECAST AREA TUESDAY AFTERNOON. BASED ON H85
TEMPS TUESDAY AND GOOD MIXING...HIGHS WILL REACH THE 40S WITH SOME
READINGS NEAR 50 IN THE SOUTH. THE CLIPPER WILL TRACK FROM SRN ND
INTO NORTHERN IOWA TUESDAY NIGHT. THIS WILL FORCE A BACK DOOR COLD
FRONT INTO THE FORECAST AREA OVERNIGHT. BY WEDS MORNING THE LEADING
EDGE OF THIS COLD AIR IS EXPECTED TO BE ANCHORED ACROSS THE
PANHANDLE. BREEZY CONDITIONS BEHIND THE COLD FRONT...WILL KEEP
TEMPERATURES ELEVATED TUESDAY NIGHT WITH LOWS IN THE MID 20S
FORECAST FOR WEDS MORNING. ACROSS THE PANHANDLE TUESDAY
NIGHT...DECENT MID LEVEL LIFT WILL COMMENCE ACROSS THE PANHANDLE AS A H7
WARM FRONT TRACKS FROM SERN WYOMING INTO SWRN SD. INHERITED FCST HAD
SLIGHT CHANCE POPS IN THE WEST AND EASTERN PANHANDLE TUESDAY NIGHT
AND WILL LEAVE THEM IN WITH THIS FCST PACKAGE. ON WEDNESDAY...THE
SURFACE FRONT WILL LIFT NORTH AS A WARM FRONT ACROSS THE FORECAST
AREA. MID LEVEL FRONTOGENESIS REMAINS FAVORABLE FOR LIGHT PCPN
ACROSS THE WEST AND NORTHWEST AS THE FRONT TRACKS NORTHEAST. HIGHS
WEDNESDAY WILL RANGE FROM THE UPPER 30S INVOF THE FRONT...TO THE
LOWER 50S IN THE SOUTHWEST.

LONG RANGE...WEDNESDAY NIGHT THROUGH SUNDAY...AS WAS THE CASE
YESTERDAY...THE MID RANGE MODELS ARE IN POOR AGREEMENT...LEADING TO
A LOW CONFIDENCE FCST. FOR EXAMPLE...THE ECMWF NUMERICAL GUIDANCE
FOR LAST NIGHT HAD HIGHS THURSDAY...FRIDAY AND SATURDAY AT 21...19
AND 25 RESPECTIVELY. THE LATEST GFS MEX GUIDANCE FROM THIS MORNING
HAD HIGHS OF 47...64 AND 38 FOR THE SAME DAYS! EVEN THE GFS ENSEMBLE
GUIDANCE HAS A SPREAD OF NEARLY 30 DEGREES FOR HIGHS ON THOSE THREE
DAYS. WITH THE LARGE MODEL SPREAD...A PERSISTENCE FORECAST WAS
UTILIZED WHICH HAD HIGHS FOR NORTH PLATTE GENERALLY FROM THE UPPER
30S TO MID 40S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1221 PM CST SUN NOV 23 2014

WINDS WILL DECREASE A BIT THIS EVENING AS THE BOUNDARY LAYER
MIXING IS REDUCED...BUT A TIGHT PRESSURE GRADIENT AND ANOTHER COLD
FRONT MOVING INTO NEBRASKA TONIGHT WILL KEEP WINDS BREEZY TO
STRONG INTO THE DAY MONDAY. SO KEPT GUSTS THROUGH THE ENTIRETY OF
THE FORECAST. BEHIND THE COLD FRONT THIS EVENING AND
TONIGHT...MODELS ARE PICKING UP ON SOME LOW LEVEL MOISTURE WHICH
WILL BRING A CHANCE FOR SOME LIGHT SNOW AND ALSO SOME MVFR
CEILINGS. THIS WILL BE MOST LIKELY OVER NORTHERN NEBRASKA SO DID
PUT 5SM VISIBILITY REDUCTION IN THE KVTN FORECAST. THIS SHOULD
ONLY LAST FOR A FEW HOURS BUT STRATUS BEHIND THE FRONT MAY STAY IN
PLACE INTO THE MORNING HOURS. IMPROVED CONDITIONS ARE EXPECTED BY
MONDAY AFTERNOON WITH CLEARING SKIES...WHILE THE STRONG NORTHWEST
WINDS WILL PERSIST.


&&

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

$$

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





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