Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 252311
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
611 PM CDT TUE AUG 25 2015

.SYNOPSIS...
ISSUED AT 307 PM CDT TUE AUG 25 2015

AT THE 20Z...THE SYNOPTIC PATTERN OVER THE CONUS WAS HIGHLIGHTED BY
A BROAD TROUGH OVER THE EASTERN THIRD...AND A STEADILY AMPLIFYING
RIDGE OF HIGH PRESSURE CENTERED OVER THE FOUR CORNERS REGION.
ANOTHER TROUGH OF LOW PRESSURE WAS BEGINNING TO DIG INTO THE PACIFIC
NORTHWEST. CLOSER TO THE CWA...SOUTHEASTERLY WINDS IN RESPONSE TO A
DEEPENING LEE SIDE SURFACE TROUGH HAVE PUSHED 50S/60S DEWPOINTS BACK
INTO WESTERN AND NORTH CENTRAL NEBRASKA. MODELS ARE GENERALLY
UNDERSELLING THE DEGREE OF MOISTURE RETURN...WHICH LOWERS FORECAST
CONFIDENCE GOING FORWARD. SKIES WERE CLEAR OVER THE AREA WITH
TEMPERATURES IN THE UPPER 70S TO THE UPPER 80S.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 307 PM CDT TUE AUG 25 2015

RIDGE OF HIGH PRESSURE ALOFT WILL KEEP THE LOCAL WEATHER FAIRLY
QUIET THROUGH THE SHORT TERM PERIOD. LOW LEVEL MOISTURE HAS MARKEDLY
INCREASED THROUGH THE DAY AS A RESULT OF SOUTHEASTERLY WINDS DRAWING
HIGHER DEWPOINTS NORTHWARD. THIS WILL KEEP LOW TEMPERATURES TONIGHT
MUCH WARMER THAN THE WELL BELOW NORMAL LOWS EXPERIENCED OVER THE
PREVIOUS COUPLE DAYS. WARM AIR ALOFT HAS CAPPED THE BOUNDARY LAYER
DESPITE THE PRESENCE OF 2000+ J/KG OF SBCAPE. A FEW STORMS ARE
POSSIBLE CLOSER TO THE FRONT RANGE MOUNTAINS...BUT NORTHWESTERLY
FLOW ALOFT WOULD STEER ANY CONVECTION SOUTH OF THE CWA AS IT MOVES
OFF THE HIGHER TERRAIN.

SHORTWAVE CURRENTLY OVER ARIZONA ROUNDS THE TOP OF THE RIDGE THROUGH
UTAH AND WYOMING ON WEDNESDAY AND BEGINS TO DEAMPLIFY THE SYNOPTIC
FLOW ALOFT. AGEOSTROPHIC ADJUSTMENT TO THE BREAKDOWN OF THE RIDGE
WILL CAUSE 700MB WINDS TO BECOME SOUTHWESTERLY AND INCREASE TO AOA
30KTS...ADVECTING A VERY WARM AND DRY AIR NORTHEASTWARD OFF THE
MOUNTAINS AND HIGHER TERRAIN OF COLORADO. SIGNIFICANT DAYTIME
INSOLATION/WARMING WILL PROMOTE BOUNDARY LAYER MIXING AND THE
TRANSPORT OF HIGHER MOMENTUM AIR DOWN TO THE SURFACE BEHIND AN
EASTWARD ADVANCING DRYLINE. THIS WILL LOCALLY INCREASE FIRE DANGER
MAINLY OVER SOUTHWEST NEBRASKA AND OUR EASTERN PANHANDLE ZONES
HOWEVER...CURRENTLY NOT EXPECTING WIND OR RH LEVELS TO HIT CRITICAL
THRESHOLDS BASED ON CURRENT FORECAST TRENDS. FIRST OFF...THE LACK OF
A UNIDIRECTIONAL WIND PROFILE WILL BE A LIMITING FACTOR TO HOW MUCH
OF THE STRONGER FLOW IN THE MID-LEVELS CAN BE REALIZED NEAR THE
SURFACE. IT IS MORE LIKELY THAT SURFACE WINDS WILL BE PRIMARILY
DRIVEN BY LOCAL PRESSURE TENDENCIES IN THE VICINITY OF A DEEPENING
LOW OVER EASTERN WYOMING...BUT A FEW HIGHER GUSTS MAKING IT TO THE
SURFACE CANNOT BE RULED OUT. SECONDLY...THE NAM/GFS CAMP IS NOW
ADVERTISING RH LEVELS AS LOW AS 10 PERCENT BEHIND THE DRYLINE IN
SOUTHWEST NEBRASKA AND THE EASTERN PANHANDLE WITH THEIR LATEST RUNS.
TRENDED THE FORECAST DRIER OVER OUR WESTERN FIRE ZONES BUT DID NOT
DROP RH LEVELS BELOW CRITICAL THRESHOLDS DUE TO LACK OF CONFIDENCE.
MODELS ARE STRUGGLING TO GET A HANDLE ON THE AMOUNT OF LOW LEVEL
MOISTURE RETURN INTO THE AREA TODAY AND HAVE BEEN FAR FROM
CONSISTENT ON THEIR SOLUTION FOR WEDNESDAY.

MODELS CONTINUE TO SHOW CONVECTION HOLDING OFF UNTIL VERY LATE
THURSDAY...SO A DRY DAYTIME FORECAST WAS MAINTAINED. THE BEST CHANCE
FOR CONVECTION WILL BE NORTH AND WEST OF THE AREA WHERE LOW LEVEL
MOISTURE CONVERGENCE WILL BE MAXIMIZED IN THE VICINITY OF THE SFC
LOW AND THE CAP WILL BE WEAKER. 700MB TEMPS CLOSE TO 15C AND WEAKER
UPPER LEVEL SUPPORT WILL LIKELY KEEP THE SANDHILLS REGION CAPPED
WITH RESPECT TO SURFACE BASED CONVECTION THROUGH 00Z THURSDAY.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 307 PM CDT TUE AUG 25 2015

WEDNESDAY NIGHT..STRONG SOUTHERLY LOW LEVEL JET WILL VEER TO
SOUTHWEST AFTER MIDNIGHT. DECENT ELEVATED INSTABILITY DEVELOPS
ACROSS NORTH CENTRAL INTO NORTHEAST NEBRASKA AFTER MIDNIGHT. WARM
AIR ADVECTION APPEARS SUFFICIENT TO DEVELOP ISOLATED STORMS ABOVE
THE CAPPED BOUNDARY LAYER. WILL CONTINUE LOW CHANCE POPS IN THAT
AREA.

SHORTWAVE/UPPER LEVEL LOW MOVES FROM WYOMING AND COLORADO AND
CROSSES THE REGION THURSDAY AND THURSDAY NIGHT. PREFER THE 12Z GFS
AND 12Z ECMWF WRT TO H7 POSITION. THERE WILL BE AN AREA OF
SURFACE LOW PRESSURE AND ASSOCIATED SURFACE TROUGH THAT MOVES
EASTWARD ACROSS OUR FORECAST AREA DURING THE DAY THURSDAY INTO
THURSDAY NIGHT. SOME CHANCE OF TSTM DEVELOPMENT ALONG AND AHEAD OF
THIS SURFACE TROUGH...HOWEVER BROADSCALE LIFT FROM UPPER LEVEL
LOW/TROUGH SUFFICIENT FOR 30 TO 50 POPS MOST AREAS. SLIGHT CHC
LIMITED ONLY TO PORTIONS OF SWRN NEBR.

FRIDAY...ON INTO THE WEEKEND AND MONDAY/TUESDAY OF NEXT WEEK...THE
UPPER LEVEL RIDGE OF HIGH PRESSURE BUILDS NORTHEASTWARD ONCE
AGAIN AND EXPANDS ACROSS THE CENTRAL/NORTHERN PLAINS. WILL
CONTINUE THE MAINLY DRY FORECAST AND SEASONABLY WARM TEMPERATURES
IN THE FORECAST. ONLY MENTION IS A SLIGHT CHANCE OF TSTMS MONDAY
AND MONDAY NIGHT AS A WEAK FRONT MOVES INTO THE REGION.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 611 PM CDT TUE AUG 25 2015

VFR IS GENERALLY EXPECTED OVERNIGHT AND THROUGH 21Z WEDNESDAY
AFTERNOON. THEREAFTER...AN ISOLATED TSTM MAY DEVELOP ACROSS SWRN
SD WHICH COULD PERHAPS BRUSH NRN NEB. 09Z-13Z WEDNESDAY...PATCHY
VALLEY FOG MAY FORM WITH THE BEST GUESS ON VSBY 3-5 MILES.

&&

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

$$

SYNOPSIS...MARTIN
SHORT TERM...MARTIN
LONG TERM...ROBERG
AVIATION...CDC


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