000
FXUS63 KLBF 210529
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1229 AM CDT MON APR 21 2014

.SYNOPSIS...
ISSUED AT 312 PM CDT SUN APR 20 2014

SOUTH WINDS WILL RETURN MOISTURE NORTH THROUGH THE HIGH PLAINS
TUESDAY AND AN UPPER LEVEL DISTURBANCE MOVING OFF THE CNTL ROCKIES
WILL TRIGGER ISOLATED TO SCATTERED TSTMS TUESDAY AFTN AND TUESDAY
NIGHT. A STRONG PACIFIC COLD FRONT MOVES THROUGH WEDNESDAY FIRING
OFF A SECOND ROUND OF ISOLATED TO SCATTERED TSTMS WEDNESDAY AFTN AND
EVENING.

THE LOW PRESSURE SYSTEM ASSOCIATED WITH THE UNSETTLED WEATHER
TUESDAY AND WEDNESDAY WILL MOVE INTO THE GREAT LAKES THURSDAY AND
PULL DOWN COLD AIR INTO THE FORECAST AREA FRIDAY THROUGH SUNDAY. AT
THE SAME TIME A DEEP UPPER LEVEL LOW IS EXPECTED TO STALL ACROSS THE
CNTL PLAINS AND PRODUCE A CHANCE OF RAIN WITH MUCH COOLER
TEMPERATURES FRIDAY NIGHT THROUGH SUNDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 312 PM CDT SUN APR 20 2014

MID LEVEL FRONTOGENESIS WILL WEAKEN ACROSS THE SOUTHEAST PORTION OF
THE FORECAST AREA THIS EVENING...MEANWHILE A COLD FRONT WILL MOVE
NORTHWEST TO SOUTHEAST THROUGH THE AREA OVERNIGHT. A PV ANOMALY
LOCATED ACROSS WYOMING...WILL TRACK EAST AND INTERACT WITH THE
FRONT. THE RESULT SHOULD BE SCATTERED SHOWERS AND THUNDERSTORMS. THE
INSTABILITY IS MARGINAL...BUT ENOUGH IS PRESENT TO KEEP THE THUNDER
MENTION GOING THROUGH THE NIGHT. WINDS WILL INCREASE FROM THE NORTH
BEHIND THE FRONT...AND LOCAL GUSTS TO 25 MPH OR SO WILL BE POSSIBLE.
LOW TEMPERATURES WILL BE MILD...IN THE MID 30S NORTHWEST TO MID 40S
EAST AND SOUTHERN PORTIONS OF THE AREA.

BREEZY NORTH WINDS WILL START THE DAY...ESPECIALLY EAST OF HIGHWAY
83. BY AFTERNOON SURFACE HIGH PRESSURE BEGINS TO BUILD INTO THE
AREA...AND WINDS WILL DIMINISH. PLEASANT TEMPERATURES ARE
EXPECTED...AS THE AIRMASS WILL BE PACIFIC IN NATURE BEHIND THE
FRONT. GENERALLY EXPECTING MID 60S TO NEAR 70 DEGREES FOR
HIGHS.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 312 PM CDT SUN APR 20 2014

MONDAY NIGHT THROUGH WEDNESDAY...
PACIFIC HIGH PRESSURE WILL MOVE OFF EAST MONDAY NIGHT WITH SOUTH
WINDS DEVELOPING ACROSS WRN NEB WHICH STRENGTHEN TUESDAY TO AROUND
25 MPH. THERE IS GOOD MODEL CONSENSUS FOR INCREASING INSTABILITY
LATE TUESDAY AFTN ACROSS WRN NEB. ONE CAVEAT...THE QUALITY OF
MOISTURE RETURNING NORTH IS LIMITED TO WHATEVER IS ACROSS TEXAS
ATTM. THE PACIFIC HIGH WILL BUILD ACROSS SOUTHWEST TEXAS TUESDAY
LIMITING THE NORTHWARD FLOW OF GULF MOISTURE.

AN UPPER LEVEL DISTURBANCE MOVES OFF THE FRONT RANGE LATE IN THE
AFTERNOON OFFERING A TRIGGER. 1-6KM BULK SHEAR OF 30 TO 40 KT
PRODUCES A BULK RICHARDSON NUMBER AROUND 20 WHICH WOULD SUPPORT
ISOLATED STORM DEVELOPMENT. THE NAM SUGGESTED A CLUSTER ACROSS SWRN
NEB. ALL OF THIS ACTIVITY SHOULD MOVE NORTHEAST THROUGH THE FCST
AREA TUESDAY NIGHT WITH THE UPPER LEVEL DISTURBANCE. POPS ARE 20 TO
30 PERCENT TUESDAY NIGHT. ONE FEATURE OF INTEREST TUESDAY NIGHT
WOULD BE THE BACKING LOW LEVEL JET IN CONCERT WITH INCREASING
MOISTURE. THE BACKING MAY BE UNDERDONE IN THE MODELS WHICH WOULD
CAUSE MORE STORM COVERAGE THAN FCST.

THE LATEST MODEL RUNS ARE A BIT FASTER WITH THE TIMING OF THE
PACIFIC COLD FRONT WEDNESDAY. THIS WOULD PLACE JUST AREAS EAST OF
HIGHWAY 83 IN ISOLATED TO SCATTERED TSTM COVERAGE DURING THE AFTN
AND THIS MIGHT BE GENEROUS. HIGH PRESSURE MOVES OUT OF TEXAS AND THE
GULF OPENS UP BUT MOST OF THIS MOISTURE IS SHUNTED EAST OF THE FCST
AREA  WITH THE APPROACH OF THE PACIFIC FRONT.

THE BULK RICHARDSON NUMBER REMAINS NEAR 20 WEDNESDAY AFTN BUT BULK
SHEAR INCREASES TO 40 TO 50 KT WITH LIFTED INDICES AROUND -5
SUGGESTING INSTABILITY WOULD BE GREATER AND STORM DEVELOPMENT MORE
VIGOROUS. MIXED LAYER WINDS ARE SOUTH SOUTHWEST AT AROUND 20 KT
AHEAD OF THE PACIFIC FRONT SUGGESTING LIMITED FRONTAL CONVERGENCE
WOULD OCCUR. HOWEVER THE MODELS SHOW A 3 MB IN 6HR PRESSURE RISE
WHICH WILL HELP STORM DEVELOPMENT. THE NAM SHOWED A 6 MB RISE IN 3
HRS WHICH IS STRONG.

THE NAM AND GFS SHOW THE PACIFIC FRONT AND SEVERE WEATHER THREAT
CLEAR OF THE FCST AREA BY 00Z WEDNESDAY EVENING. THE NAM WAS SLOWER
PLACING THE FRONT NEAR KONL-KBBW WHILE THE GEM WAS EVEN SLOWER
SHOWING THE FRONT FROM KMER-KOGA. THE FORECAST FOLLOWS A MODEL BLEND
WHICH PLACES THE FRONT ALONG OR JUST EAST OF HIGHWAY 83 AT 00Z
WEDNESDAY EVENING. THIS TIMING IS IMPORTANT AS IT DICTATES THE AREAL
EXTENT OF THE SEVERE WEATHER WEDNESDAY AFTN.

WE ARE EXPECTING HIGHS IN THE 70S TO LOWER 80S BOTH DAYS.

WEDNESDAY NIGHT THROUGH SUNDAY...
987 MB LOW PRESSURE WILL MOVE INTO THE UPPER MIDWEST THURSDAY AND
PULL LATE SEASON ARCTIC AIR SOUTH THROUGH THE NRN PLAINS. THE FRONT
WILL REMAIN NORTH OF THE FCST AREA THURSDAY WITH PACIFIC HIGH
PRESSURE PRODUCING HIGHS IN THE 60S. THE ARCTIC AIR BACKS IN FRIDAY
AND REMAINS IN PLACE THROUGH SUNDAY. THE ECM HAS SNOW ACROSS SOUTH
DAKOTA SUNDAY AND THE GFS SHOWS IT IN NRN NEB. MAX TEMPS FRIDAY IN
THE 50S AND 60S FALL TO THE UPPER 40S AND 50S BY SUNDAY BUT A BLEND
OF THE 12Z OPERATIONAL GFS AND ECM SHOWED HIGHS IN THE 50S AND 60S
FRIDAY FALLING TO THE 30S AND 40S BY SUNDAY.

AT THE SAME TIME AN UPPER LEVEL LOW MOVES IN FROM THE 4 CORNERS AND
BASICALLY STALLS OVER THE CNTL PLAINS. A CHANCE OF RAIN IS IN THE
FORECAST FRIDAY NIGHT THROUGH SUNDAY NIGHT. TSTM CHANCES LOOK NIL AS
NO INSTABILITY IS SHOWN IN THE MODELS EITHER SFC OR ALOFT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1229 AM CDT MON APR 21 2014

SCATTERED THUNDERSTORMS WILL CONTINUE TO MOVE TO THE SOUTHEAST OVER
WESTERN NEBRASKA EAST OF A LINE FROM KVTN TO KLBF THROUGH THE EARLY
MORNING HOURS. LIMITED LOW LEVEL MOISTURE SO BASES ON THUNDERSTORMS
AROUND 8K FT. STRONG GUSTY OUT FLOW CAN BE EXPECTED ALONG AND BEHIND
THIS LINE WITH GUST 25 TO 30 KTS. SKIES WILL CLEAR THROUGH THE EARLY
MORNING HOURS WITH NORTH WINDS DIMINISHING SOME BEFORE PICKING BACK
UP THROUGH THE LATE MORNING AND AFTERNOON ON MONDAY.

&&

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

$$

SYNOPSIS...CDC
SHORT TERM...TAYLOR
LONG TERM...CDC
AVIATION...POWER