Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 062349 AAA
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
649 PM CDT MON JUL 6 2015

.SYNOPSIS...
ISSUED AT 312 PM CDT MON JUL 6 2015

SYNOPTIC PATTERN AS OF MONDAY AFTERNOON WAS DOMINATED BY A BROAD
TROUGH OVER MUCH OF CANADA WITH THE MAIN UPPER LEVEL LOW PUSHING
EAST INTO HUDSON BAY. ANOTHER SHORTWAVE WAS ROTATING THROUGH THE
BASE OF THE TROUGH AND TRACKING SOUTHEAST THROUGH MANITOBA AND INTO
THE NORTHERN PLAINS. A STRONG COLD FRONT HAS PUSHED SOUTH AND EAST
THROUGH THE STATE WITH NORTHERLY FLOW ESTABLISHED AT SURFACE. COOLER
AND DRIER AIR HAS ADVECTED SOUTHWARD BEHIND THE FRONT WITH
TEMPERATURES IN THE LOW TO 70S...20 TO 30 DEGREES COOLER THAN THIS
TIME SUNDAY. THE NORTHERLY WINDS HAVE ALSO TRANSPORTED SMOKE FROM
CANADIAN WILDFIRES INTO THE AREA WITH HAZY CONDITIONS REPORTED.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 312 PM CDT MON JUL 6 2015

RATHER COOL TEMPERATURES FOR JULY ARE EXPECTED TONIGHT AS AN AREA OF
SURFACE HIGH PRESSURE DRIFTS INTO THE DAKOTAS. THE LOW TEMPERATURE
FORECAST MAY STILL NEED A FEW ADJUSTMENTS DUE TO UNCERTAINTIES WITH
CLOUD COVERAGE TONIGHT. EXPECTING MOSTLY CLEAR CONDITIONS FOR MOST
OF THE NIGHT AS MODELS SHOW SIGNIFICANT MID-LEVEL DRYING AS
SHORTWAVE TROUGH AXIS PUSHES EAST. THIS TREND IS REFLECTED ON
VISIBLE SATELLITE WITH AS MOST UPSTREAM CLOUD COVER IS DIURNALLY
DRIVEN CUMULUS WHICH SHOULD DISSIPATE TOWARD SUNSET. THE CLEARING
SKIES AND COOL AIRMASS WILL ALLOW TEMPERATURES TO FALL INTO THE LOW
50S...BUT WOULD NOT BE SURPRISED IF A FEW SPOTS DROP INTO THE UPPER
40S IF MOST OF THE CLOUD COVER ERODES. THE HAZY CONDITIONS FROM
CANADIAN SMOKE MAY STICK AROUND THIS EVENING AND TONIGHT...BUT THIS
FORECAST IS HIGHLY UNCERTAIN. THE EASTWARD PROGRESSION OF THE
SURFACE HIGH WILL RESULT AIR PARCEL IN TRAJECTORIES THAT WOULD PUSH
THE MAJORITY OF THE SMOKE EAST OF THE CWA. HOWEVER...THE DECOUPLING
OF THE BOUNDARY LAYER AND CALMING WINDS TONIGHT MAY TRAP SOME OF THE
SMOKE THROUGH TOMORROW MORNING...PRIMARILY IN LOCAL VALLEYS.

SYNOPTIC FLOW ALOFT BECOMES QUASI-ZONAL ON TUESDAY. BELOW NORMAL MAX
TEMPERATURES ARE EXPECTED ONCE AGAIN AS 850MB HOVER AROUND 12C-14C.
LOW LEVEL WINDS BECOME SOUTHERLY OVER THE HIGH PLAINS AND STEADILY
INCREASE THROUGH THE DAY AS THE SURFACE HIGH MOVES INTO SOUTHERN
MINNESOTA. HOWEVER MOISTURE ADVECTION WILL BE MEAGER AS THE DEEP
GULF MOISTURE IS BLOCKED BY THE COLD FRONT HUNG UP ACROSS THE
SOUTHERN PLAINS. ISOLATED TO SCATTERED CONVECTION WILL LIKELY FIRE
ALONG THE HIGHER TERRAIN TO OUR WEST BY THE AFTERNOON HOURS...BUT
MODELS KEEP OUR CWA DRY THROUGH 00Z WEDNESDAY.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 312 PM CDT MON JUL 6 2015

TUESDAY NIGHT THROUGH THURSDAY...THE MODELS HAVE DELAYED THE ONSET
OF RAINFALL TUESDAY NIGHT UNTIL WEDNESDAY OR WELL...NOT AT ALL.
THERE ARE SOME SERIOUS DIFFERENCES IN THE GEM...GFS...NAM...SREF AND
ECM. THE GFS AND SREF COVER THE FCST AREA WITH QPF WHILE THE NAM AND
ECM JUST SOUTH...THE GEM SHOWS NEARLY NONE AT ALL.

AT THE 500 AND 300 MB HEIGHT LEVELS THE MODEL CONSENSUS SHOWS A
SERIES OF DISTURBANCES MOVING THROUGH COLORADO WEDNESDAY AND
THURSDAY AND THE MODELS SHOW SUFFICIENT 850-500MB FOR RAINFALL. BUT
THE FORCING MAY WEAKEN AS IT MOVES EAST ACROSS THE TOP OF DRY HIGH
PRESSURE CURRENTLY IN PLACE ACROSS NEBRASKA RESULTING IN JUST
MIDLEVEL CLOUDINESS AND SPRINKLES.

GIVEN THAT ALL MODELS SHOW 850-300MB RH INCREASING 80 PERCENT OR
HIGHER AT TIMES...THE FORECAST USES A BLEND OF THE PREVIOUS AND
CURRENT MODEL SUITE. THIS PRODUCES RAIN CHANCES...MAINLY WEDNESDAY
THROUGH THURSDAY WITH THE BEST CHANCES SOUTH AND WEST. ELEVATED
INSTABILITY IS VERY LIMITED WHICH SUGGESTS THUNDERSTORMS MIGHT ONLY
OCCUR ACROSS THE PANHANDLE AND SWRN NEB...SOUTH OF INTERSTATE 80.

HIGHS RISE JUST INTO THE 70S WITH CLOUDS EXPECTED. HIGH PRESSURE
WILL CONTINUE TO CIRCULATE COOL AIR IN THE FCST AREA. LOWS FALL INTO
THE 50S. EXPECTED CLOUD COVER SHOULD LIMIT RADIATIONAL COOLING AT
NIGHT.

AN UPPER LOW OFF THE CALIFORNIA COAST WILL PIN WHEEL EAST INTO SRN
NEVADA THURSDAY AFTN AND A SERIES OF DISTURBANCES SHOULD EJECT EAST
INTO THE CNTL PLAINS. THE LONG WAVE TROF SHOULD FLUSH HOT AIR FROM
THE DESERT BUT THIS AIR WILL REMAIN ACROSS KS SOUTH OF A STATIONARY
FRONT DRAPED ACROSS NCNTL KS ASSOCIATED WITH SFC LOW PRESSURE OVER
SERN COLORADO. THE NAM SHOWS STRONG MOISTURE ADVECTION INTO SWRN NEB
WEDS NIGHT AND THURSDAY WHICH COULD PRODUCE HEAVY RAIN. THUS...THE
REALM OF RAINFALL POSSIBILITIES IS LARGE.

THURSDAY NIGHT THROUGH MONDAY...THE UPPER LEVEL LOW ACROSS THE WRN
U.S. LIFTS AND PARTIALLY SHEARS OUT ACROSS THE NRN PLAINS SATURDAY.
THE RESULT IS A SURGE OF VERY DRY AIR INTO THE FCST AREA SATURDAY
AND DRY NORTHWEST FLOW DEVELOPS SUNDAY. THE MEX GUIDANCE INDICATES
WIDESPREAD HIGHS IN THE 90S SATURDAY AND SUNDAY WITH 100S SUNDAY
SOUTH AND WEST. BIAS CORRECTION LOWERS THE HIGHS SEVERAL DEGREES AND
REMOVES THE 100S. THE GEM...GFS AND ECM SHOW H700MB TEMPERATURES
RANGING FROM 10C TO 15C WHICH MEANS HIGHS COULD BE ABOUT 5F HIGHER
OR LOWER THAN MEDIAN FORECAST IN PLACE.

GIVEN THE DRY AIR SURGING ACROSS THE ROCKIES AND THE DRYLINE
POSITIONED EAST OF HIGHWAY 83 IN THE MODEL CONSENSUS...SOME DEGREE
OF THE WARMER GFS MIGHT VERIFY...ESPECIALLY IF LITTLE RAIN FALLS
ACROSS SWRN NEB THIS WEEK. MOST OF MODELS HOWEVER KEEP THE HOTTEST
AIR ACROSS COLORADO BENEATH THE H500MB RIDGE CENTER.

THUNDERSTORMS ARE POSSIBLE FRIDAY AS A WARM FRONT LIFTS THROUGH THE
FCST AREA. THE GFS AND ECM SHOW A 60KT 300MB JET LIFTING ACROSS THE
ROCKIES FOR UPPER LEVEL SUPPORT AND BULK SHEAR. SFC DEW POINTS IN
THE 60S WOULD PRODUCE SUFFICIENT CAPE FOR STRONG OR SEVERE STORMS
AND THE CAP IS MODEST WITH H700MB TEMPERATURES AT OR BELOW 12C.
STORM COVERAGE WOULD LIKELY REMAIN SCATTERED GIVEN THE RELATIVELY
WEAK FORCING AND THE CAP STRENGTH. AFTER FRIDAY...DRY AIR MOVES IN
AND RAIN CHANCES VANISH.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 650 PM CDT MON JUL 6 2015

AREAS OF SMOKE CONTINUE TO REDUCE VISIBILITIES OVER WESTERN
NEBRASKA. VISIBILITIES HAVE IMPROVED THIS EVENING BUT STILL MAY
APPROACH MVFR CATEGORIES. AS THE WINDS DECOUPLE SOME OF THIS SMOKE
MAY BE TRAPPED BELOW THE INVERSION ALONG THE RIVER VALLEYS. WINDS
WILL BECOME LIGHT AND VARIABLE OVE NIGHT AND ARE EXPECTED AT LESS
THAN 10 KTS OVER WESTERN NEBRASKA ON TUESDAY.

&&

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

$$

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






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