Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 031806
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
106 PM CDT MON AUG 3 2015

.SYNOPSIS...
ISSUED AT 350 AM CDT MON AUG 3 2015

THE H5 PATTERN REMAINS LARGELY UNCHANGED OVER THE PAST 24 HOURS
ACROSS CANADA AND THE NRN TIER OF STATES. A CLOSED LOW WAS
PRESENT OVER NRN ONTARIO WITH A TROUGH OF LOW PRESSURE EXTENDING
SWD INTO THE CAROLINAS. RIDGING WAS PRESENT ACROSS THE NRN
ROCKIES AND CANADIAN ROCKIES WHILE A CLOSED LOW WAS PRESENT
ACROSS NWRN BRITISH COLUMBIA. BROAD WEST NORTHWESTERLY FLOW
EXTENDED FROM THE CANADIAN PRAIRIE PROVINCES ESE INTO THE NRN
PLAINS AND OHIO VALLEY. ACROSS THE INTERMOUNTAIN WEST AND THE
SOUTH CENTRAL CONUS...HIGH PRESSURE REMAINED DOMINANT.
HOWEVER...A STRONG SHORTWAVE WAS NOTED OVER EASTERN UTAH THIS
MORNING AND SHOWS UP NICELY ON CURRENT WV IMAGERY. AT THE
SURFACE...A COLD FRONT EXTENDED FROM ROUGHLY OGALLALA TO EUSTIS
NEBRASKA. WINDS NORTH OF THIS FEATURE WERE CALM OR LIGHT FROM THE
NORTH...WHILE SOUTH OF THE FEATURE...WINDS WERE WESTERLY OR
SOUTHERLY. SKIES WERE MOSTLY CLOUDY AS ABUNDANT MID AND HIGH
CLOUDS STREAMED INTO SOUTHWESTERN AND WEST CENTRAL NEBRASKA FROM
THE CENTRAL ROCKIES. TEMPERATURES AS OF 3 AM CDT RANGED FROM 62
AT NORTH PLATTE TO 68 AT IMPERIAL.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 350 AM CDT MON AUG 3 2015

THUNDERSTORM CHANCES TODAY AND TONIGHT WILL BE THE MAIN
FORECASTING CHALLENGE. ELEVATED INSTABILITY WILL CONTINUE TO BE
THE DRIVING FORCE FOR CONVECTIVE DEVELOPMENT THIS MORNING...AS
WELL AS LATER TONIGHT. FOR THIS MORNING...A H700 WARM FRONT WILL
PUSH FROM CENTRAL NEBRASKA INTO NORTHERN NEBRASKA THROUGH SUNRISE.
THE LATEST NAM...AS WELL AS THE HI RES WARW AND WNMM
SOLUTIONS...AND TO A LESSER DEGREE THE GFS...INITIATE CONVECTIVE
DEVELOPMENT INVOF THIS H7 WARM FRONT THIS MORNING. HAVE
INTRODUCED POPS ACROSS NORTHERN NEBRASKA FOR THIS MORNING...AS
WELL AS THE PRE FIRST PD FCST TO ACCOUNT FOR THIS INSTABILITY AND
THE THREAT FOR STORMS THIS MORNING. ATTM...THIS ACTIVITY IS
EXPECTED TO BE ANCHORED ALONG AND NORTH OF THE FRONT...OR NORTH
OF HIGHWAY 92. THIS ACTIVITY WILL BEGIN TO DISSIPATE BY MIDDAY AS
THE H7 FRONT STALLS ACROSS NORTH CENTRAL NEBRASKA. FURTHER
SOUTH...THE SURFACE FRONT WILL BEGIN TO LIFT SLOWLY NORTH THIS
AFTERNOON. BY 21Z...THIS FEATURE WILL BE ORIENTED FROM AROUND
ANTIOCH TO CALLAWAY. ALONG AND NORTH OF THIS FEATURE...THERE WILL
DECENT THREAT FOR THUNDERSTORM DEVELOPMENT THIS AFTERNOON AS
SURFACE HEATING SUFFICIENTLY WEAKENS THE CAP. ALONG AND NORTH OF
THE FRONT...DEEP LAYER SHEAR WILL BE SUFFICIENT TO SUPPORT SEVERE
STORMS. BY EVENING...DEEP LAYER SHEAR WILL BEGIN TO WEAKEN AFTER
MID EVENING. HOWEVER...ELEVATED INSTABILITY WILL INCREASE ONCE
AGAIN OVER NORTHERN PORTIONS IF THE FORECAST AREA INVOF THE H700
FRONT. THE LATEST NAM SOLN HAS FCST CAPE OF 500 TO 1000 J/KG
CALCULATED FROM THE H700 LAYER ACROSS NORTHERN NEBRASKA BY LATE
EVENING. THIS ALONG WITH VERY STEEP LAPSE RATES IN THE H500 TO
H700 LAYER WOULD SUPPORT STORMS OVERNIGHT...IF THEY CAN INITIATE
AND THIS IS THE WILDCARD IN THE FORECAST. WITH THE PRESENCE OF
THE H85 FRONT AND A 30 KT LOW LEVEL JET TONIGHT...THE LEADING
EDGE OF THIS BEING FOCUSED ACROSS THE SANDHILLS AND NORTHERN
NEBRASKA...MAY PROVIDE ENOUGH LIFT PUSH ANY LOWER LEVEL
CONVECTION UP TO THE VERY UNSTABLE MID LEVELS TONIGHT. IF THIS
CAN BE ACHIEVED...WE COULD SEE PERSISTENT STORMS OVERNIGHT IN THE
NORTH. THERE IS GOOD SUPPORT FOR THIS PLAYING OUT WITH THE LATEST
NAM...WARW AND WNMM SOLNS FOR TONIGHT...SO FEEL CONFIDENT ENOUGH
TO RAISE POPS ACROSS THE NORTH OVERNIGHT. AS FOR TEMPERATURES
TODAY...SOUTH OF THE FRONT...READINGS WILL REACH THE LOWER TO
MIDDLE 90S. ACROSS NORTHERN PORTIONS OF THE FORECAST AREA...TEMPS
WILL STRUGGLE TO TOP THE LOWER TO MIDDLE 80S THANKS TO CLOUD
COVER AND COOLER H85 TEMPS NORTH OF THE FRONT. FOR TONIGHT...LOWS
WILL BE IN THE 60S THANKS TO INCREASING LOW LEVEL MOISTURE
OVERNIGHT...AS WELL AS EXPECTED CLOUD COVER.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 350 AM CDT MON AUG 3 2015

A POTENT SHORTWAVE ALOFT CURRENTLY IN UTAH...WILL LIFT NORTH INTO
WYOMING TONIGHT AND THEN TURN EAST AND CROSS THE AREA TUESDAY AND
TUESDAY NIGHT. ALTHOUGH T HE MODELS VARY SOMEWHAT WITH THE
STRENGTH AND EXACT LOCATION OF THE WAVE AS IT CROSSES THE
AREA...THEY ALL INDICATE AN UPTICK IN TSTM ACTIVITY. A SURFACE
FRONT WILL BE NEARLY STATIONARY FROM NORTHWEST TO SOUTHEAST
ACROSS THE IMMEDIATE AREA TUESDAY INTO TUESDAY NIGHT...AND EXPECT
THAT THIS WILL HELP FOCUS TSTM DEVELOPMENT. SCATTERED TSTMS
SHOULD ACTUALLY ALREADY BE ONGOING EARLY TUESDAY MORNING ACROSS
MUCH OF THE AREA IN ZONE OF BROAD ISENTROPIC LIFT. TSTMS...AT
LEAST IN A SCATTERED FASHION...MAY CONTINUE THROUGH MOST OF THE
DAY...AND EXPECT QUITE A BIT IN THE WAY OF MID AND HIGH LEVEL
CLOUDINESS AS A RESULT. THIS COULD CUT DOWN SOME ON THE SEVERE
THREAT AS SURFACE BASED INSTABILITY MAY BE SOMEWHAT MEAGER.
ANOTHER LIMITING FACTOR FOR ORGANIZED SEVERE STORMS WILL BE
RATHER WEAK WINDS ALOFT. THE BIGGER THREAT WILL LIKELY BE LOCALLY
HEAVY RAIN IN SOME PLACES. HAVE MAINTAINED THE 40 TO 50 POPS FOR
THE TUESDAY/TUESDAY NIGHT TIMEFRAME AS THE WAVE CROSSES THE AREA.

WEDNESDAY INTO THE WEEKEND...THE SURFACE FRONT WILL LINGER IN THE
AREA...WITH SEVERAL WEAK UPPER LEVEL DISTURBANCES CROSSING THE AREA
WITHIN WESTERLY FLOW ALOFT. ECMWF INDICATES A STRONGER WAVE MAY
CROSS THE AREA SATURDAY AND SATURDAY NIGHT...AND WILL CARRY SOMEWHAT
HIGHER CHANCES FOR TSTMS DURING THAT PERIOD. TEMPERATURE WISE...WITH
THE UPPER LEVEL RIDGE REMAINING ACROSS THE SOUTHERN PLAINS...EXPECT
THE HOT TEMPERATURES TO REMAIN IN THAT AREA UNDER THE RIDGE. IN OUR
REGION TEMPERATURES WILL AVERAGE NEAR NORMAL...IN THE MID TO UPPER
80S. NO HEAT WAVES SEEN IN THE IMMEDIATE FUTURE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 105 PM CDT MON AUG 3 2015

ISOLATED TO SCATTERED THUNDERSTORMS WILL BE POSSIBLE THIS
AFTERNOON AND OVERNIGHT ACROSS THE ENTIRE AREA...HOWEVER MOST
MODELS DEVELOP ACTIVITY NORTH OF INTERSTATE 80 THIS AFTERNOON AND
KEEP IT NORTH OVERNIGHT. THUS WILL NOT MENTION ANY T IN THE NORTH
PLATTE TAF. FOR NOW CONTINUED THE PROB 30 GROUP FOR KVTN THIS
EVENING AS THIS REMAINS THE HIGHEST LIKELYHOOD OF THUNDERSTORM
ACTIVITY. THAT SAID...WILL CONTINUE TO MONITOR CLOSELY FOR ANY
DEVELOP AND AMEND AS NEEDED. THE NAM AND RAP SUGGEST MVFR/IFR
STRATUS OVER PORTIONS OF SW NEB IN THE MORNING. SINCE WE HAD A
BRIEF STRATUS LAYER THIS MORNING...CANNOT RULE IT OUT. WINDS
GENERALLY SOUTHEAST AT 10 T0 20 MPH.

&&

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

&&

$$

SYNOPSIS...CLB
SHORT TERM...CLB
LONG TERM...TAYLOR
AVIATION...MASEK



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