Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 150424 AAC
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1124 PM CDT TUE APR 14 2015

.SYNOPSIS...
ISSUED AT 319 PM CDT TUE APR 14 2015

H5 ANALYSIS FROM THIS MORNING IS INDICATING SIGNIFICANT
HT FALLS ACROSS THE NWRN CONUS OF 50 TO 140 METERS. THIS IS IN
ADVANCE OF A TROUGH OF LOW PRESSURE...CURRENTLY EXTENDING FROM
CENTRAL OREGON...SOUTH TO SAN FRANCISCO CA. HT FALLS WERE MOST
PRONOUNCED TO THE SE OF THE SHORTWAVE OVER CENTRAL OREGON AND WERE
LOCATED OVER NRN NEVADA. DOWNSTREAM OF THE TROUGH ...LOW AMPLITUDE
RIDGING EXTENDED FROM WESTERN NEBRASKA...NWD INTO NRN PORTIONS OF
SASKATCHEWAN AND ALBERTA. HT RISES OF 50 TO 150 METERS WERE NOTED
ACROSS THE NRN GREAT LAKES...AS WELL AS WESTERN ONTARIO AND
MANITOBA. DOWNSTREAM OF THIS RIDGE...A TROUGH OF LOW PRESSURE WAS
DEEPENING OVER QUEBEC....AND NEW ENGLAND. HT FALLS JUST TO THE EAST
OF THIS TROUGH WERE RUNNING AS HIGH AS 260 METERS IN NRN QUEBEC THIS
MORNING. HIGH PRESSURE WAS NOTED OVER CUBA...WITH LOW PRESSURE NOTED
OVER THE BERING SEA WEST OF ALASKA. AT THE SURFACE...HIGH PRESSURE
WAS LOCATED OVER THE MID MISSISSIPPI VALLEY. WEST OF THE FORECAST
AREA...A SURFACE TROUGH OF LOW PRESSURE WAS DEEPENING ACROSS EASTERN
WYOMING AND EASTERN COLORADO. A TIGHT PRESSURE GRADIENT WAS PRESENT
ACROSS THE FORECAST AREA TODAY...WHICH HAS LED TO STRONG SOUTHERLY
WINDS AND CRITICAL FIRE DANGER THIS AFTERNOON. TEMPERATURES AS OF 3
PM CDT RANGED FROM 69 AT OGALLALA TO 73 AT VALENTINE.

&&

.UPDATE...
ISSUED AT 906 PM CDT TUE APR 14 2015

THE RED FLAG WARNING FOR WESTHERN AND NORTH CENTRAL NEBRASKA HAS
BEEN ALLOWED TO EXPIRE AT 9 PM CDT.

WITH THE LOSS OF DAYTIME HEATING...TEMPERATURES HAVE FALLEN
REDUCING THE RISK OF WILDFIRES. WINDS WILL REMAIN STRONG OVERNIGHT
IN SOME AREAS OF NORTHERN NEBRASKA...ROUGHLY FROM VALENTINE WEST
THROUGH HAYS SPRINGS. HUMIDITY WILL ALSO REMAIN LOW...NEAR 20
PERCENT FOR A FEW MORE HOURS.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 319 PM CDT TUE APR 14 2015

FIRE DANAGER REMAINS HIGH THIS EVENING WITH RED FLAG WARNING IN
EFFECT UNTIL 9 PM CDT (8 PM MDT). STRONG WINDS WITH GUSTS TO AROUND
40 MPH POSSIBLE. AT 18Z DEWPOINTS WERE IN THE 20S ACROSS THE AREA
WHERE DEWPOINTS MAY REACH DOWN INTO THE TEENS IN SOME LOCALES.

OVERNIGHT THE SOUTHERLY WILL SUSTAIN YET DIMINISH AFTER MIDNIGHT
WHERE INCREASED MIXING WILL RESULT IN LOW TEMPERATURES WEDNESDAY
MORNING FROM AROUND 40 IN THE WEST TO MID 40S NORTH CENTRAL.
MOISTURE WILL BE SLOW TO RETURN ACROSS THE WEST...BUT AS A SOUTHERLY
LOW LEVEL JET STRENGTHENS ON THE HIGH PLAINS MOISTURE RETURNS ON THE
HIGH PLAINS FOR INCREASING CLOUD COVER THROUGH THE DAY.

ON WEDNESDAY A WEAK BOUNDARY WILL EXTEND SOUTH ACROSS WESTERN
NEBRASKA. AS A STRONG SHORTWAVE LIFTS NORTHEAST DURING THE AFTERNOON
THUNDERSTORM ARE EXPECTED TO DEVELOP IN THE WEST THEN LIFT NORTH AND
EAST. THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORM DEVELOPMENT
ACROSS THE FAR SOUTHWEST AFTER 3 PM CDT. DEEP MOISTURE IS LIMITED
WHERE STORMS THAT FORM INITIALLY WILL BE HIGH BASED WITH A FEW
CAPABLE OF PRODUCING DAMAGING WINDS IN THE FAR SOUTHWEST. AS
THUNDERSTORMS CONTINUE TO LIFT NORTHEAST...STORMS WILL WEAKEN.
DAYTIME HIGHS WEDNESDAY WILL BE IN THE 60S. FIRE DANAGER REMAINS HIGH
THIS EVENING WITH RED FLAG WARNING IN EFFECT UNTIL 9 PM CDT (8 PM
MDT). STRONG WINDS WITH GUSTS TO AROUND 40 MPH POSSIBLE. AT 18Z
DEWPOINTS WERE IN THE 20S ACROSS THE AREA WHERE DEWPOINTS MAY
REACH DOWN INTO THE TEENS IN SOME LOCALES.

OVERNIGHT THE SOUTHERLY WILL SUSTAIN YET DIMINISH AFTER MIDNIGHT
WHERE INCREASED MIXING WILL RESULT IN LOW TEMPERATURES WEDNESDAY
MORNING FROM AROUND 40 IN THE WEST TO MID 40S NORTH CENTRAL.
MOISTURE WILL BE SLOW TO RETURN ACROSS THE WEST...BUT AS A SOUTHERLY
LOW LEVEL JET STRENGTHENS ON THE HIGH PLAINS MOISTURE RETURNS ON THE
HIGH PLAINS FOR INCREASING CLOUD COVER THROUGH THE DAY.

ON WEDNESDAY A WEAK BOUNDARY WILL EXTEND SOUTH ACROSS WESTERN
NEBRASKA. AS A STRONG SHORTWAVE LIFTS NORTHEAST DURING THE AFTERNOON
THUNDERSTORM ARE EXPECTED TO DEVELOP IN THE WEST THEN LIFT NORTH AND
EAST. THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORM DEVELOPMENT
ACROSS THE FAR SOUTHWEST AFTER 3 PM CDT. DEEP MOISTURE IS LIMITED
WHERE STORMS THAT FORM INITIALLY WILL BE HIGH BASED WITH A FEW
CAPABLE OF PRODUCING DAMAGING WINDS IN THE FAR SOUTHWEST. AS
THUNDERSTORMS CONTINUE TO LIFT NORTHEAST...STORMS WILL WEAKEN.
DAYTIME HIGHS WEDNESDAY WILL BE IN THE 60S.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 319 PM CDT TUE APR 14 2015

MID TERM...WEDNESDAY NIGHT THROUGH FRIDAY...IN THE MID
TERM...THUNDERSTORM CHANCES...FOLLOWED BY SHOWER CHANCES FOR WEDS
NIGHT THROUGH FRIDAY WILL BE THE MAIN FORECAST CONCERNS. DECENT
SETUP EXISTS FOR THUNDERSTORMS WEDNESDAY NIGHT...FOLLOWED BY MORE
PERSISTENT RAINFALL FOR THURSDAY INTO FRIDAY. FOR WEDNESDAY
NIGHT...A POTENT UPPER LEVEL TROUGH OF LOW PRESSURE WILL BEGIN TO
CLOSE OFF INVOF THE FOUR CORNERS AROUND 00Z THURSDAY. AS THE UPPER
LEVEL LOW DEEPENS...SURFACE LOW PRESSURE WILL INTENSIFY OVER
EASTERN COLORADO DURING THE SAME TIME PERIOD...WITH AN INVERTED
SURFACE TROUGH EXTENDING NWD INTO WESTERN PORTIONS OF THE FORECAST
AREA. BY WEDS EVENING...SURFACE HEATING IN THE WARM SECTOR IN
EASTERN COLORADO AND SWRN KS...COUPLED WITH MOISTURE RETURN...WILL
INCREASE INSTABILITY IN WESTERN KS/EASTERN COLORADO LATE WEDS
AFTERNOON AND EARLY WEDS EVENING. WITH A LEAD SHORTWAVE
APPROACHING SWRN NEBRASKA WEDS EVENING...MID LEVEL LAPSE RATES
WILL STEEPEN CONSIDERABLY ACROSS THE SOUTHWESTERN AND WESTERN
PORTION OF THE FORECAST AREA. ATTM...BASED ON THE LATEST NAM AND
GFS SOLNS...WE SHOULD SEE TSRA INITIATION ACROSS EASTERN
COLORADO...FAR WESTERN KS ON THE NRN PERIPHERY OF THE SURFACE LOW.
AIDED BY SSW FLOW AT H5...THIS ACTIVITY SHOULD LIFT QUICKLY TO THE
NORTH NORTHEAST WEDS EVENING. WITH STEEP LAPSE RATES...ELEVATED
INSTABILITY...AND BULK SHEAR OF 25 TO 40 KTS...CONVECTION IS
EXPECTED TO CONTINUE INTO THE EVENING HOURS IN THE WESTERN CWA AND
HAVE EXTENDED THE MENTION OF THUNDER NORTH TO THE SD/NE BORDER
BASED ON THE PRESENCE OF NEGATIVE ELEVATED LI/S. WITH THE 40 KTS
OF BULK SHEAR NOTED IN THE FAR SWRN CWA...WOULDN/T BE SURPRISED TO
SEE A SEVERE STORM OR TWO...ESPECIALLY OF THE ELEVATED VARIETY
WITH LARGE HAIL AS THE THREAT. THE THREAT FOR THUNDER WILL SHIFT
EWD INTO CENTRAL AND EASTERN PORTIONS OF THE FORECAST AREA
OVERNIGHT AS THE INVERTED SFC TROUGH MIGRATES SLOWLY EAST. WEST OF
THE INVERTED TROUGH...COOLER TEMPERATURES AND SFC DEW POINTS IN
THE 30S MAY LEAD TO A RAIN/SNOW MIX ON THE WESTERN PERIPHERY OF
THE FORECAST AREA LATE WEDS NIGHT/EARLY THURSDAY MORNING. LOOKING
AT BUFKIT SOUNDINGS...A FINITE WINDOW FOR SNOW EXISTS AROUND 12Z
THURSDAY MORNING. ATTM GIVEN THE SMALL WINDOW FOR SNOW...DECIDED
TO KEEP THE MENTION OF RAIN OR SNOW AND WILL NOT PLACE ANY
ACCUMULATIONS IN THE FORECAST. ON THURSDAY AND FRIDAY...SOME
CONSIDERABLE MODEL DIFFERENCES CONTINUE WITH RESPECT TO THE
GFS/ECMWF/AND NAM SOLNS WITH THE TRACK AND PROGRESSION OF THE
CLOSED LOW OVER THE SRN ROCKIES AND PLAINS. AS WAS THE CASE
YESTERDAY...THE LATEST GFS CONTINUES TO FAVOR DUAL CLOSED
LOWS...WHICH MIGRATE INTO ONE LOW OVER THE SRN PLAINS FRIDAY. THE
ECMWF...GEFS ENSEMBLES...AND NAM...FAVOR ONE CLOSED SYSTEM...WHICH
WILL SLOWLY MIGRATE EAST OF THE FOUR CORNERS...EMERGING ONTO HE
SRN PLAINS FRIDAY NIGHT. THE FCST CONSENSUS ATTM IS FOR THE
SLOWER...SRN LOW. WITH THIS IN MIND...LOW POP CHANCES WILL
CONTINUE INTO FRIDAY AS WE REMAIN ON THE NERN QUADRANT OF THE
UPPER LEVEL LOW. ADDITIONAL SUPPORT FOR PCPN LIES WITH THE
FACT...THE SYSTEM REMAINS CUTOFF FROM THE NRN STREAM...WHICH
SHOULD ALLOW MOISTURE TO CONTINUE TO FLOW INTO THE FORECAST AREA
THROUGH FRIDAY.

LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...AS MENTIONED
EARLIER...THE LATEST EXTENDED FORECAST HEAVILY UTILIZES THE 12Z
ECMWF AS WELL AS THE GEFS ENSEMBLE MEAN FCST. THAT BEING SAID...THE
CURRENT FORECAST TRACKS THE UPPER LEVEL LOW SLOWLY EAST OF THE FOUR
CORNERS WITH THE LOW LIFTING ALONG THE KS/OK BORDER LATE SATURDAY
INTO SUNDAY. ON THIS COURSE...AND WITH THE UPPER LEVEL LOW NOT
PHASED WITH THE NRN STREAM UNTIL SUNDAY...A WET FORECAST WILL
CONTINUE ACROSS THE FORECAST AREA...AS WE REMAIN IN EAST AND
NORTHEASTERLY FLOW. CONDS WILL SLOWLY DRY OUT SUNDAY NIGHT AND
BEYOND AS THE CLOSED LOW AND NRN STREAM LOW MIGRATE EAST. SEASONAL
TEMPS ARE EXPECTED THEREAFTER WITH MAINLY DRY CONDS
FORECAST.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1122 PM CDT TUE APR 14 2015

VFR IS EXPECTED ALL AREAS OVERNIGHT THROUGH 21Z WEDNESDAY
AFTERNOON. THEREAFTER ISOLATED TO SCATTERED THUNDERSTORMS WILL
BEGIN MOVING EAST ACROSS WRN NEB IN ASSOCIATED WITH A POWERFUL
PACIFIC COLD FRONT ACROSS WY AND WRN COLO THIS EVENING. A DEEP
UPPER LEVEL LOW ACROSS IDAHO WILL MOVE EAST SOUTHEAST INTO NRN
COLORADO WEDNESDAY EVENING PROVIDING ADDITIONAL SUPPORT FOR
SHOWER AND THUNDERSTORM DEVELOPMENT. MVFR CIGS MAY DEVELOP ACROSS
WRN NEB AS THE PACIFIC FRONT MOVES INTO THE NEB PANHANDLE AFTER
00Z WEDNESDAY EVENING. THE RISK OF MVFR CIGS OVERNIGHT TONIGHT
WITH RETURN MOISTURE MOVING APPEARS LOW.

WINDS OVERNIGHT GRADUALLY DIMINISH ACROSS SHERIDAN AND WRN CHERRY
COUNTIES 17030G40KT DECREASING TO 17020G30KT BY 12Z WEDNESDAY.

&&

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

$$

UPDATE...CDC
SYNOPSIS...CLB
SHORT TERM...KECK
LONG TERM...CLB
AVIATION...CDC





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