Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 222326 AAA
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
626 PM CDT FRI AUG 22 2014

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 258 PM CDT FRI AUG 22 2014

AT 19Z A BAND OF PRECIP CONTINUES ALONG A MID LEVEL DEFORMATION BAND
FROM NORTHEAST COLORADO INTO NORTH CENTRAL NEBRASKA. FURTHER EAST
WINDS WERE BEGINNING TO VEER FROM NORTHERLY TO EASTERLY...ADVECTING
MOISTURE UPSLOPE TO THE WEST. A FEW THUNDERSTORMS WERE ALREADY
DEVELOPING ON ALONG A FRONTAL BOUNDARY AND WESTERN PERIPHERY OF A
DEEPLY MOIST AND INCREASINGLY UNSTABLE AIRMASS. THIS BOUNDARY
EXTENDS SOUTHWEST INTO EASTRN COLORADO WHERE DEEP SFC BASED
DEVELOPMENT IS UNDERWAY. THE MAIN AREA OF THUNDERSTORM ACTIVITY IS
EXPECTED TO DEVELOP ALONG THIS BOUNDARY AND MOVE NORTH OUT OF
EASTERN COLORADO AND NORTHWEST KANSAS THIS AFTERNOON AND EVENING AS
THE UPPER LEVEL WAVE AND ANOTHER SURGE OF MONSOONAL MOISTURE
APPROACHES THE CENTRAL PLAINS....PUSHING PWATS TO OVER TWO STANDARD
DEVIATIONS ABOVE NORMAL. VERY STRONG QG ASCENT AND A WEAK EML
SUGGESTS CONVECTION WILL BE WIDESPREAD BY EARLY EVENING.
THUNDERSTORM ACTIVITY SHOULD REMAIN ROBUST AND SUSTAINED THROUGH THE
NIGHT AS THE LLJ STRENGTHENS AND SUPPLIES AMPLE WAA AND MOISTURE
TRANSPORT INTO THE AREA. EXPECTING HEAVY RAINFALL WITH PRIMARY AREA
OF CONVECTION SURGING NORTH FROM SOUTHWEST INTO NORTH CENTRAL
NEBRASKA LATE THIS AFTERNOON INTO THE OVERNIGHT...AS WELL AS IN THE
WESTERN SANDHILLS WHERE THE MID LEVELS DEFORMATION ZONE WILL
STRENGTHEN TO WEST SIDE OF THE SFC LOW PRESSURE MOVING INTO THE
CENTRAL SANDHILLS OVERNIGHT. ISENTROPIC ANALYSIS SHOWS STRONG
UPSLOPE THETA-E ADVECTION IN THE LOW TO MID LEVELS THROUGH 9Z
TONIGHT. OVERALL...WOULD NOT BE SURPRISED TO SEE NUMEROUS REPORTS OF
1" OF RAINFALL WITH HIGHER AMOUNTS POSSIBLE WITHIN AREAS OF
SUSTAINED DEEP CONVECTION.

SEVERE WEATHER WILL ALSO BE POSSIBLE ACROSS MUCH OF THE FORECAST
AREA LATE THIS AFTERNOON AND INTO THE EVERY OVERNIGHT HOURS. 1630Z
UPDATE FROM SPC HAS MOST OF THE CWA IN A SLIGHT RISK. MID LEVEL
LAPSE RATES GREATER THAN 7 C/KM AND DEEP LAYER SHEAR IN EXCESS OF
40 KTS WILL SUPPORT AN ENVIRONMENT CAPABLE OF LARGE HAIL AND STRONG
DAMAGING WINDS. HIGH RES MODELS CONTINUE TO FAVOR A NORTHEASTWARD
PROPAGATING MCS INTO CENTRAL NEBRASKA AFTER DARK AS COLD POOLS
MERGE. A SMALL WINDOW FOR A TORNADO OR TWO WILL EXIST DURING THE
EVENING HOURS AS LOW LEVEL SHEAR INCREASES IN CONJUNCTION WITH A
STRENGTHENING LOW LEVEL JET. HOWEVER THE FAVORABLE AREA LOOKS LIKE
IT WILL MOSTLY STAY SOUTH OF THE CWA IN THE VICINITY OF THE WARM
FRONT IN NORTHERN KANSAS AND FAR SOUTHERN NEBRASKA.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 258 PM CDT FRI AUG 22 2014

SATURDAY NIGHT THROUGH MONDAY...AT THIS TIME...THE MAIN
FORECAST CHALLENGE IN THE MID RANGE IS PRECIPITATION CHANCES...IN
PARTICULAR SATURDAY NIGHT...THEN AGAIN LATE SUNDAY NIGHT INTO
MONDAY. AN ACTIVE SWRLY FLOW PATTERN WILL CONTINUE THROUGH THE END
OF THE WEEKEND INTO MONDAY. A SERIES OF UPPER LEVEL
DISTURBANCES/CLOSED SYSTEMS WILL TRACK THROUGH THE CENTRAL AND
NORTHERN ROCKIES...EMERGING ONTO THE CENTRAL AND NORTHERN PLAINS
OVER THE NEXT FEW DAYS. SURFACE LOW PRESSURE WILL DEEPEN OVER NERN
COLORADO SAT AFTERNOON AND WILL LIFT NORTH ACROSS SOUTHWESTERN AND
CENTRAL NEBRASKA OVERNIGHT. AT THE SAME TIME...A DECENT UPPER LEVEL
DISTURBANCE AND INCREASED MID LEVEL WARM AIR ADVECTION WILL
OVERSPREAD WESTERN AND NORTH CENTRAL NEBRASKA SATURDAY EVENING INTO
THE OVERNIGHT. AS FOR CONVECTIVE INITIATION ACROSS THE HIGH
PLAINS...ATTM AM EXPECTING THIS TO TAKE PLACE EITHER IN SWRN
NEBRASKA OR NERN COLORADO...AS SUBSIDENCE IN THE WAKE OF EXITING
PCPN FROM TONIGHT AND EARLY SATURDAY WILL BE STRONGEST ACROSS
CENTRAL AND NRN NEBRASKA. PCPN WILL RIDE NORTHEAST...NORTH OF AN
EXITING COLD FRONT...INTO WESTERN AND NORTHERN AREAS OVERNIGHT
THANKS TO THE DEVELOPMENT OF A LOW LEVEL JET AND INCREASING
ISENTROPIC LIFT. BY SUNDAY MORNING...MUCH DRIER AIR AND STRONG
SUBSIDENCE WILL PUSH INTO THE FORECAST AREA BEHIND THE EXITING
FRONT. SLIGHTLY COOLER TEMPS ARE EXPECTED AS WELL WITH HIGHS IN THE
LOWER TO MIDDLE 80S COMPARED TO THE MID AND UPPER 80S ON SATURDAY.
ON SUNDAY NIGHT...ANOTHER STRONG UPPER LEVEL DISTURBANCE WILL DIVE
SOUTH INTO THE NORTHERN ROCKIES. SURFACE LOW PRESSURE WILL DEVELOP
SUNDAY NIGHT OVER EASTERN COLORADO WITH A NICE FRONTAL BOUNDARY
EXTENDING ACROSS NORTHERN KS/SRN NEBR BY 06Z MONDAY. DECENT MID
LEVEL WARM AIR ADVECTION WILL RIDE TO THE EAST NORTHEAST FROM
COLORADO INTO SWRN NEBRASKA OVERNIGHT...LEADING TO ANOTHER CHANCE
FOR THUNDERSTORMS INTO MONDAY MORNING.

MONDAY NIGHT THROUGH FRIDAY...AN ACTIVE WEATHER PATTERN WILL
CONTINUE THROUGH AT LEAST MIDWEEK AS LOW AMPLITUDE SWRLY FLOW ALOFT
CONTINUES ACROSS THE WESTERN CONUS. ON THE HEELS OF THE UPPER LEVEL
DISTURBANCE SUNDAY NIGHT...ANOTHER STRONG UPPER LEVEL DISTURBANCE
AND ENHANCED MID LEVEL WARM AIR ADVECTION WILL LIFT ACROSS WESTERN
AND CENTRAL NEBRASKA MONDAY NIGHT INTO TUESDAY MORNING. DEEP LAYER
SHEAR WILL BE FAIRLY STRONG MONDAY NIGHT...SO THERE WILL BE A THREAT
FOR SEVERE STORMS. IN ADDITION...ABUNDANT LOW LEVEL MOISTURE WILL
PUSH WEST INTO SOUTHWESTERN AND WESTERN NEBRASKA WITH LAYER PWATS
BETWEEN 1.5 AND 1.8 INCHES MONDAY EVE...WHICH MAY LEAD HEAVY RAIN
AND INCREASED FLOODING POTENTIAL. WITH STRONG MODEL AGREEMENT NOTED
BETWEEN THE GFS AND ECMWF SOLNS...LIKELY POPS MONDAY
NIGHT...ESPECIALLY IN THE SRN HALF OF THE FORECAST AREA...SEEM ON
TRACK. PCPN CHANCES WILL CONTINUE INTO TUESDAY NIGHT OR WEDNESDAY AS
A PERSISTENT TROUGH IN THE ROCKIES...FINALLY MIGRATES EAST INTO THE
MISSISSIPPI VALLEY. IN ITS WAKE...RIDGING WILL BEGIN TO BUILD ACROSS
THE WESTERN HALF OF THE CONUS...LEADING TO DRIER AND WARMER CONDS
ACROSS THE CWA THURSDAY INTO FRIDAY. BOTH THE GFS AND ECMWF SOLNS ARE
INDICATIVE OF THIS SOLN MID TO LATE WEEK NEXT WEEK. HOWEVER...THE
GFS IS ABOUT 12 HRS FASTER IN PUSHING THE FINAL UPPER LEVEL TROUGH
EAST OF THE AREA TUESDAY NIGHT VS WEDNESDAY. WITH THIS IN
MIND...WILL HOLD ONTO POPS WEDNESDAY AND NOT ELIMINATE THEM FROM THE
FCST UNTIL WEDS NIGHT. WARMER AND DRIER CONDS WILL SET IN THURSDAY
AND FRIDAY WITH TEMPERATURES RETURNING BACK TO THE MID 80S
THURSDAY...FOLLOWED BY UPPER 80S FRIDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 626 PM CDT FRI AUG 22 2014

AN ACTIVE TSTM NIGHT IS IMMINENT WITH CONVECTION LIFTING NORTH
FROM KS AND BECOMING MORE NUMEROUS AND POSSIBLY MORE SEVERE. THE
RISK OF WIND DAMAGE IS EXPECTED TO INCREASE. THE RAP...THE SLOWER
MODEL...SUGGESTS STORM COVERAGE SHOULD EXIT NCNTL NEB BY 14Z-15Z
SATURDAY MORNING. VFR IS EXPECTED ALL AREAS THEREAFTER. THE MODELS
SUGGEST A MIX OF VFR AND MVFR CIGS AFTER THE TSTMS EXIT SRN NEB
LATER TONIGHT.

&&

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

$$

SHORT TERM...MARTIN
LONG TERM...CLB
AVIATION...CDC






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