Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 221754
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1254 PM CDT FRI MAY 22 2015

.SYNOPSIS...
ISSUED AT 345 AM CDT FRI MAY 22 2015

H5 ANALYSIS FROM THIS EVENING HAD CLOSED LOW PRESSURE
OFF THE CENTRAL CA COAST...WHILE A LOW AMPLITUDE RIDGE EXTENDED FROM
TEXAS NWD INTO THE NEBR PANHANDLE. FURTHER EAST...STRONG LOW
PRESSURE WAS NOTED OVER FAR SRN PORTIONS OF HUDSON BAY WITH A TROUGH
EXTENDING SWD INTO THE OHIO VALLEY. WV IMAGERY TONIGHT HAS THE
CALIFORNIA LOW NOW APPROACHING THE SRN COAST OF CALIFORNIA. A LEAD
SHORTWAVE WAS PUSHING INTO SERN COLORADO ATTM. THIS FEATURE HAS
FIRED OFF SHOWERS ACROSS EASTERN COLORADO AND WESTERN KANSAS
OVERNIGHT. AS OF 230 AM CDT...THE LEADING EDGE OF THESE SHOWERS WERE
LOCATED ROUGHLY 30 MILES SOUTH OF A GOODLAND...TO COLBY TO HILL CITY
KANSAS LINE. TRACKING THE PROGRESSION OF THESE SHOWERS...THEY SHOULD
BEGIN TO APPROACH FAR SOUTHERN PORTIONS OF THE FORECAST AREA SOME
TIME AROUND 6 AM CDT. AT THE SURFACE...HIGH PRESSURE WAS PRESENT
OVER EASTERN NEBRASKA AND EASTERN KS. THIS HAS ALLOWED SRLY AND
SERLY WINDS TO DEVELOP ACROSS THE WESTERN HALF OF THE FORECAST AREA
TONIGHT...INCREASING DEW POINTS INTO THE LOWER TO MID 40S. COMPARED
TO LAST NIGHT...TEMPERATURES WERE MUCH WARMER DUE TO THE COMBINATION
OF CLOUDS AND INCREASED LOW LEVEL MOISTURE. READINGS AS OF 3 AM CDT
RANGED FROM 42 AT AINSWORTH TO 51 AT OGALLALA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 345 AM CDT FRI MAY 22 2015

THE MAIN FORECAST CHALLENGE IS
PRECIPITATION CHANCES OVER THE NEXT 24 HOURS. PRECIPITATION WILL
COME IN TWO WAVES OVER THE NEXT 24 HOURS. THE FIRST WAVE WILL MOVE
INTO THE SRN FORECAST AREA NEAR SUNRISE THIS MORNING...MAKING ITS
WAY NORTH TO THE INTERSTATE 80 CORRIDOR BY 8 AM CDT. THE SHORT RANGE
MODELS...MOST NOTABLY THE NAM12...WARF...HRRR AND WNMM SOLNS CAME IN
SLOWER WITH THE ONSET OF PCPN THIS MORNING. AND INITIALLY CUT BACK
POPS IN THE NORTH...DELAYING THEM UNTIL LATER THIS MORNING.
HOWEVER...RADAR IMAGERY ACROSS KANSAS HAS THE LEADING EDGE OF THE
PRECIPITATION JUST OFF TO THE SOUTH OF A GOODLAND...TO HILL CITY
LINE. BASED ON THE FORWARD MOTION...THE LEADING EDGE OF THIS PCPN
SHOULD HIT THE FAR SRN CWA BY 6 AM CDT...AND WILL APPROACH THE
INTERSTATE 80 CORRIDOR BY 9 AM CDT. WITH THIS IN MIND...SLOWED DOWN
THE ONSET OF PCPN FROM THE INHERITED FCST...HOWEVER BROUGHT IT IN
SLIGHTLY EARLIER COMPARED TO THE SHORT RANGE MODELS...GIVEN THE
CURRENT RADAR RETURNS AND THE FORWARD SPEED OF THE AREA OF SHOWERS.
AS FOR THE THREAT FOR THUNDERSTORMS THIS MORNING...THE LATEST NAM
FORECAST LI`S ARE WELL ABOVE ZERO THIS MORNING...SO ACTIVITY WILL BE
LIMITED TO SHOWERS ONLY WITHOUT THE MENTION OF THUNDER. THIS AREA OF
PCPN WILL LIFT SLOWLY NORTH TODAY WITH A BRIEF REPRIEVE IN PCPN IN
THE SRN CWA LATER THIS AFTERNOON. BY EVENING...A SECONDARY LEAD
SHORTWAVE WILL PUSH INTO EASTERN COLORADO...INITIATING SHOWERS AND
THUNDERSTORMS. THIS ACTIVITY WILL LIFT NEWD INTO THE SRN CWA LATER
THIS EVENING PER THE LATEST NAM12...WARF AND WNMM SOLNS WHICH HAVE A
CLUSTER OF THUNDERSTORMS PUSHING INTO THE AREA TONIGHT. ELEVATED
INSTABILITY WILL BE PRESENT OVERNIGHT AS H850 AND H800 CALCULATED
LI`S ARE WELL BELOW ZERO. INHERITED FCST HAD A MENTION OF THUNDER
TONIGHT AND SEE NO REASON TO TAKE IT OUT OF THE FCST ATTM. NOW AS
FOR THE THREAT FOR SEVERE STORMS...THE THREAT APPEARS LOW ATTM AS
THE BEST CAPES ARE WELL SOUTHWEST OF THE AREA WHERE SOME SUN AND SFC
HEATING TAKES PLACE. ALSO WITH THE CWA UNDER A VEIL OF CLOUD COVER
TODAY...CONDS WILL BE FAIRLY STABLE AT THE SFC...THUS NO TSRAS ARE
EXPECTED FOR LATE THIS AFTERNOON. AS MENTIONED EARLIER...ELEVATED
INSTABILITY WILL INCREASE OVERNIGHT PER H85 AND H80 NEG LI`S. WITH
THIS IN MIND...INSERTED A MENTION OF THUNDER...ESPECIALLY IN THE
SOUTH AND WEST. IN ADDITION TO THE THREAT FOR THUNDERSTORMS...PATCHY
FOG WILL BE POSSIBLE IN THE CENTRAL AND SOUTH. NUMERICAL
GUIDANCE...AS WELL AS THE SREF VISIBILITY FCST INDICATES A DECENT
THREAT FOR PATCHY FOG TONIGHT AFTER 06Z. WITH THIS IN MIND...DECIDED
TO LEAVE IN A MENTION OF PATCHY FOG OVERNIGHT.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 345 AM CDT FRI MAY 22 2015

IT APPEARS THAT SATURDAY WILL SEE LITTLE IF ANY SUNSHINE ACROSS THE
AREA. LOW LEVEL MOISTURE WILL BE INCREASING THROUGH THE DAY...AND
STRATUS SHOULD REMAIN LOCKED IN WITH EAST TO SOUTHEAST LOW LEVEL
UPSLOPE FLOW. EXPECT THAT A FEW SHOWERS AND THUNDERSTORMS MAY
OCCUR...BUT THESE SHOULD BE SCATTERED AT BEST AS MID LEVEL DRY AIR
PASSES OVERHEAD IN THE WAKE OF FRIDAY NIGHTS DISTURBANCE. THIS MID
LEVEL DRY AIR ABOVE THE SATURATED LOWER LEVELS COULD LEAD TO PATCHY
DRIZZLE...AND WILL INCLUDE IN SATURDAY MORNING FORECAST. AS
MENTIONED WITH LITTLE SUNSHINE EXPECTED...EXPECT A RATHER COOL DAY
WITH MOST HIGHS IN THE LOWER 60S.

A SIGNIFICANT PV ANOMALY WILL EJECT NORTHEAST THROUGH THE PLAINS ON
THE EASTERN PERIPHERY OF THE UPPER LEVEL LOW SATURDAY NIGHT. THIS
WILL COINCIDE WITH A MODESTLY STRONG SOUTHERLY LOW LEVEL JET...AND
EXPECT A ROUND OF SHOWERS AND THUNDERSTORMS TO LIFT NORTHEAST ACROSS
THE AREA. THE THREAT FOR SEVERE LOOKS LOW...BUT SHEAR IS STRONG AND
SOME SMALL HAIL IS POSSIBLE WITH THE STRONGER STORMS. AN ISOLATED
SEVERE STORM WITH QUARTER SIZE HAIL CANNOT BE RULED OUT.

MODELS ARE COMING INTO BETTER AGREEMENT SUNDAY. GEFS MEAN HAS THE
CENTER OF THE UPPER LEVEL LOW NEAR DENVER SUNDAY MORNING. THE 22/00Z
NAM...GFS AND ECMWF MODELS ARE ALL IN A SIMILAR LOCATION WITH THE
UPPER LOW. CONFIDENCE IS INCREASING THAT A MID LEVEL DRY SLOT WILL
MOVE NORTHEAST ACROSS THE FORECAST AREA THROUGH THE DAY. WILL CARRY
THE HIGHER POPS DURING THE MORNING SUNDAY...AND TAPER TO JUST SLIGHT
CHANCE FOR ALL BUT THE PANHANDLE AND FAR WEST DURING THE AFTERNOON
AS THE MID LEVEL DRY SLOT MOVES OVERHEAD. A WARMER TREND IS ALSO
NOTED IN THE MODELS TONIGHT. NAM AND GFS SCOUR OUT SOME OF THE LOW
STRATUS CLOUDS DURING THE AFTERNOON...AND THE ECMWF IS COMING AROUND
TO THIS IDEA AS WELL. THIS COULD LEAD TO AT LEAST PARTLY SUNNY SKIES
SUNDAY AFTERNOON...AND HAVE BOOSTED HIGHS A BIT INTO THE LOWER TO
PERHAPS MID 70S FROM PORTIONS OF NORTH CENTRAL THROUGH SOUTHWEST
NEBRASKA. WILL KEEP THE MID TO UPPER 60S GOING FARTHER WEST IN
CLOSER PROXIMITY TO THE UPPER LEVEL LOW...WHERE MORE CLOUDS AND
BETTER CHANCES FOR SHOWERS AND STORMS WILL BE LOCATED.

SPEAKING OF STORMS...WILL HAVE TO AT LEAST EXPLORE THE IDEA OF A FEW
STRONG OR PERHAPS SEVERE THUNDERSTORMS LATER SUNDAY AFTERNOON INTO
SUNDAY EVENING. BOTH THE 22/00Z GFS AND NAM HAVE AN INVERTED TROUGH
EXTENDING NORTHEAST THROUGH THE FORECAST AREA UNDER THE DRY SLOT
FROM A SURFACE SLOW IN EASTERN COLORADO. SHOULD BE SOME FAIRLY STEEP
MID LEVEL LAPSE RATES OVERSPREADING THE AREA DURING THE AFTERNOON
AND EVENING...WHICH WILL HELP YIELD POTENTIALLY 1500 TO 2500 J/KG OF
SURFACE BASED CAPE. 0 TO 6 KM BULK SHEAR IS AROUND 30 KTS...A BIT
MORE THAN THAT IN THE GFS AND A BIT LESS IN THE NAM. IF ENOUGH
HEATING CAN TAKE PLACE TO REALIZE THE POTENTIAL CAPE...THEN SHEAR
WOULD BE SUPPORTIVE OF A FEW STRONG TO SEVERE STORMS. BACKED WINDS
TO THE SOUTHEAST ARE EXPECTED EAST OF THE SURFACE TROUGH...OR
ROUGHLY EAST OF HIGHWAY 83...AND SUPERCELL STRUCTURES COULD
MATERIALIZE. THE THINKING IS THAT STORMS WILL DEVELOP ALONG THE
SURFACE TROUGH VERY LATE SUNDAY AFTERNOON OR EARLY SUNDAY EVENING
ALONG OR NEAR HIGHWAY 83. THE STORMS WILL BE AIDED BY LARGE SCALE
ASCENT FROM UPPER LOW WHICH WILL BE LOCATED JUST WEST OF THE
AREA...AND A SOUTH-SOUTHWESTERLY LOW LEVEL JET WHICH STRENGTHENS
SUNDAY EVENING. SO EXPECT STORMS TO CONGEAL INTO A LINE OR CLUSTER
AND MOVE NORTHEAST ACROSS NORTH CENTRAL AND CENTRAL NEBRASKA SUNDAY
NIGHT.

UPPER LOW WILL EJECT NORTHEAST THROUGH THE AREA MONDAY...WITH A
CONTINUED CHANCE FOR SHOWERS AND STORMS. ANOTHER LONG WAVE/CLOSED
LOW WILL DROP INTO THE NORTHERN ROCKIES TUESDAY AND DEVELOP SOUTH
THROUGH THE CENTRAL AND SOUTHERN ROCKIES MID TO LATE WEEK. SHOULD BE
A BROAD SOUTHWEST FLOW ALOFT ATOP A TROPICAL MARITIME AIRMASS ACROSS
THE CENTRAL AND SOUTHERN PLAINS...WITH MORE CHANCES FOR
THUNDERSTORMS. COVERAGE LOOKS SCATTERED THOUGH...WITH WARMER
TEMPERATURES EXPECTED.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1252 PM CDT FRI MAY 22 2015

A BAND OF LIGHT TO MODERATE RAINFALL WILL LIFT ACROSS THE AREA
THIS AFTERNOON. MORE LIGHT RAIN SHOWERS WILL FILL IN BEHIND THE
BAND. MVFR TO LOCALLY IFR CONDITIONS WILL ACCOMPANY THE RAIN.
OVERNIGHT A CHANCE FOR A FEW THUNDERSTORMS COULD LIFT INTO SW NEB.
OTHERWISE MVFR/IFR OR LOWER CIGS/FOG DEVELOPS ACROSS THE AREA.
THIS WILL BE SLOW TO IMPROVE IN THE MORNING.

&&

.HYDROLOGY...
ISSUED AT 345 AM CDT FRI MAY 22 2015

THE SOUTH PLATTE RIVER AT ROSCOE AND THE PLATTE RIVER
AT BRADY ARE EXPECTED TO BE AT MINOR FLOOD STAGE OVER THE NEXT
SEVERAL DAYS. ELEVATED RIVER LEVELS WILL CONTINUE ALONG THE SOUTH
PLATTE RIVER AT NORTH PLATTE...AS WELL AS THE NORTH PLATTE RIVER AT
LEWELLEN. RECENT HEAVY RAIN IN THE PANHANDLE AND NORTHEASTERN
COLORADO...ALONG WITH SNOWMELT FROM THE COLORADO ROCKIES...HAS LED
TO THE ELEVATED RIVER LEVELS. ABUNDANT RAIN IS FORECAST OVER THE
NEXT COUPLE OF DAYS...ESPECIALLY IN THE SOUTH AND NORTH PLATTE RIVER
BASINS WHICH WILL PROBABLY CONTRIBUTE TO ADDITIONAL RISES IN RIVER
LEVELS TOWARD THE END OF NEXT WEEK. BOTTOM LINE...RIVER LEVELS ALONG
THE NORTH AND ESPECIALLY THE SOUTH PLATTE RIVER WILL BE ELEVATED FOR
AT LEAST THE NEXT 2 TO 4 WEEKS.

&&

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

&&

$$

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



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