Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 211149
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
649 AM CDT THU MAY 21 2015

.SYNOPSIS...
ISSUED AT 400 AM CDT THU MAY 21 2015

H5 ANALYSIS TONIGHT HAS A BROAD AREA OF LOW PRESSURE OFF
THE COAST OF CALIFORNIA WITH A TROUGH EXTENDING SWD TO OFF THE COAST
OF BAJA CALIFORNIA. DOWNSTREAM OF THE TROUGH...LOW AMPLITUDE RIDGING
WAS NOTED FROM NEW MEXICO...NWD INTO WYOMING...WHILE MAINLY ZONAL
FLOW EXTENDED ACROSS THE MIDWEST...OHIO VALLEY AND SERN STATES. AT
THE SURFACE...HIGH PRESSURE HAD NOSED INTO NORTHWESTERN NEBRASKA
OVERNIGHT...AND HAS LED TO CLEARING SKIES ACROSS NORTH
CENTRAL...CENTRAL AND EASTERN NEBRASKA. LOWER CLOUDS HAVE HUNG ON
ACROSS THE SWRN CWA OVERNIGHT...ROUGHLY SOUTH OF A LINE FROM
OSHKOSH...TO PAXTON...TO HAYES CENTER. SOME HIGHER CLOUDS HAVE
PUSHED INTO THE REMAINDER OF SWRN NEBRASKA...AND HAS KEPT TEMPS
HITTING THE LOWER 30S AS OF 3 AM CDT. FURTHER NORTH AND WEST...LOWER
30S WERE NOTED ACROSS THE NWRN CWA...IN CLOSE PROXIMITY TO THE
SURFACE HIGH. SO FAR...THE AREAL COVERAGE OF THE FROST ADVISORY IS
ON TRACK ATTM AND WILL BE RE EVALUATED NEAR FORECAST ISSUANCE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT THU MAY 21 2015

THE MAIN FORECAST CHALLENGES ARE
TEMPERATURES TODAY AND THE EFFECTS OF RESIDUAL CLOUD COVER ON
THEM...AS WELL AS THE THREAT FOR RAIN IN THE SW AND SERN PANHANDLE
OVERNIGHT TONIGHT. FOR TODAY...HIGH PRESSURE WILL BUILD SOUTHEAST
INTO MISSOURI THIS AFTERNOON...RESULTING IN A WIND SHIFT TO THE
SOUTH ACROSS THE WESTERN HALF OF THE FORECAST AREA. THIS SHIFT WILL
INCREASE LOW LEVEL MOISTURE TOWARD THE END OF THE DAY INTO TONIGHT
WITH DEW POINTS REACHING THE LOWER 40S OVERNIGHT TONIGHT.
TEMPERATURES TODAY WILL GENERALLY BE IN THE LOWER TO MID 60S WITH
THE WARMEST READINGS EXPECTED IN THE NORTHEASTERN CWA...WHERE CLEAR
SKIES AND THE DRIEST AIRMASS RESIDES. ACROSS SWRN PORTIONS OF THE
CWA...SKIES WILL BE PARTLY TO MOSTLY CLOUDY WITH INCREASING CLOUDS
EXPECTED LATE AFTERNOON AS A SHORTWAVE APPROACHES THE SRN ROCKIES
AND SRN PLAINS. FOR TONIGHT...THE BEFORE MENTIONED SHORTWAVE WILL
LIFT NORTHEAST WITH THE H5 FLOW INTO EASTERN COLORADO AND WESTERN
KS. THIS FEATURE WILL APPROACH SWRN NEBRASKA OVERNIGHT. CROSS
SECTIONS INDICATE A DECENT SHOT OF MID LEVEL MOISTURE MOVING NORTH
INTO SWRN NEBRASKA OVERNIGHT WITH DECENT MID LEVEL LIFT COMMENCING
AFTER 06Z FRIDAY. INHERITED FORECAST HAD A GOOD HANDLE ON THE POPS
TONIGHT...AND HAVE ONLY SLIGHTLY SLOWED DOWN THE ONSET OF PCPN BASED
ON THE LATEST MODEL TRENDS. THE NAM12...GFS...WARF...AND NMM
GENERALLY KEEP PCPN OUT OF THE SWRN CWA UNTIL AFTER 06Z FRIDAY. BY
12Z FRIDAY...THE PRECIPITATION SHIELD APPROACHES THE INTERSTATE 80
AND HIGHWAY 26 CORRIDOR. HAVE LEFT PTYPES AS ALL RAIN AS WAS THE
CASE WITH THE INHERITED FCST. LIFTED INDICES...BOTH SURFACE
BASED...AS WELL AS ELEVATED...ARE WELL ABOVE ZERO TONIGHT...SO
THUNDER IS NOT EXPECTED ATTM. WITH INCREASING CLOUDS IN THE CENTRAL
AND NORTH...AND PRECIPITATION EXPECTED IN THE SOUTH AND
SOUTHWEST...OVERNIGHT LOWS WILL GENERALLY BE IN THE LOWER 40S.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 400 AM CDT THU MAY 21 2015

NEXT LONG WAVE TROUGH/CLOSED LOW WILL BE MOVING ONSHORE THE WEST
COAST FRIDAY. A LEAD SHORTWAVE WILL BE MOVING THOUGH THE AREA AHEAD
OF THIS FEATURE FRIDAY INTO FRIDAY NIGHT. ISENTROPIC LIFT/MID LEVEL
WARM AIR ADVECTION WILL BE WELL UNDERWAY BY FRIDAY MORNING. GFS AND
ECMWF CONTINUE TO BE MORE AGGRESSIVE WITH THE RAIN AND QPF AMOUNTS
ACROSS SOUTHWEST NEBRASKA FRIDAY MORNING. THE NAM CONTINUES TO BE
THE DRIER MODEL SOLUTION...AND AN INVESTIGATION OF THE NAM BUFFER
SOUNDING HINTS AT SOME DRY AIR AROUND 750MB EARLY IN THE MORNING.
THIS LAYER SATURATES COMPLETELY BY MID MORNING THOUGH...AND THE
LATEST 21/00Z NAM IS NOT QUITE AS AGGRESSIVE WITH HOLDING ON TO THE
DRY AIR AS PREVIOUS RUNS WERE...AND IS NOW GENERATING MORE QPF THAN
PREVIOUS RUNS AS A RESULT. THE GOING FORECAST ALREADY HAD
CATEGORICAL/DEFINITE POPS FOR FRIDAY MORNING ACROSS SOUTHWEST
NEBRASKA...AND SEE NO REASON TO LOWER THOSE...ESPECIALLY NOW THAT
THE NAM IS TRENDING A BIT WETTER. OTHERWISE ANOTHER CHILLY DAY WITH
THE CLOUDS AND PRECIP...BUT NOT AS CHILLY AS THE PREVIOUS RAIN EVENT
WE HAD ON MONDAY...AS THE 850MB TEMPS WILL BE ABOUT 5C WARMER THIS
TIME AROUND. GENERALLY EXPECT LOWER TO MID 50S IN THE RAINY AREAS OF
SOUTHWEST NEBRASKA...TO THE LOWER AND MID 60S ACROSS EASTERN
PORTIONS OF NORTH CENTRAL NEBRASKA WHERE THE RAIN WILL HOLD OFF TILL
LATE IN THE AFTERNOON.

FOR FRIDAY NIGHT THROUGH THE WEEKEND...MODELS UNFORTUNATELY ARE NOT
IN VERY GOOD AGREEMENT IN THE HANDLING OF THE WESTERN CONUS LONG
WAVE TROUGH/CLOSED LOW. OVERALL IT DOES NOT LOOK LIKE A COMPLETE
RAIN OUT THIS WEEKEND. CONTINUES TO BE HARD TO NAIL DOWN WHEN AND
WHERE THE BEST CHANCE FOR PRECIPITATION WILL BE...AS EACH MODEL HAS
IT/S OWN IDEA. THE BEST CHANCE APPEARS TO BE SATURDAY NIGHT AS A
FAIRLY POTENT MID LEVEL DISTURBANCE ROTATES NORTH THROUGH THE AREA
ON THE EASTERN PERIPHERY OF THE CLOSED UPPER LOW WHICH WILL BE
LOCATED NEAR NORTHWEST COLORADO BY THIS TIME. SUNDAY INTO
MONDAY...THE GEFS MEAN KEEPS THE UPPER SYSTEM CLOSED AS IT TRACKS
ACROSS SOUTH DAKOTA INTO NORTHERN MINNESOTA. THE OPERATIONAL GFS
AND ECMWF ARE MUCH SLOWER AND HOLD THE MAIN UPPER LEVEL SYSTEM BACK
IN THE ROCKIES. WITH ALL THE MODEL DIFFERENCES...HAVE TRIED TO TREND
POPS DOWN FOR THE WEEKEND OVERALL. MODELS ARE REALLY NOT GENERATING
A WHOLE LOT OF QPF AT ANY ONE TIME...AND MY THINKING IS THAT IT WILL
BE MORE OF A SCATTERED MID LEVEL WARM AIR ADVECTION TYPE PRECIP
EVENT...AS NO REAL FOCUS FOR ANY ONE AREA TO RECEIVE CONCENTRATED
HEAVY RAINFALL. THIS COULD CHANGE AS MODELS EVENTUALLY WILL HAVE TO
COME INTO BETTER AGREEMENT...AND WILL WATCH THIS CLOSELY. ONE MAJOR
DIFFERENCE IN THE MODELS IS ON SUNDAY. THE 21/00Z GFS INSISTS THAT A
SURFACE TROUGH WILL MOVE EAST INTO THE FORECAST AREA...WITH
INCREASING INSTABILITY AND POSSIBLE STRONGER THUNDERSTORMS. THE
21/00Z ECMWF WILL HAVE NONE OF THIS...AND KEEPS A BROAD COOLER/MOIST
SOUTHEAST TO EAST FLOW WITH LOW CLOUDS SOCKED IN. WILL CONTINUE TO
MONITOR THE LATEST MODEL TRENDS AND HOPEFULLY BEGIN TO SEE SOME
BETTER AGREEMENT.

WITH THE POOR MODEL AGREEMENT ALREADY SEEN BY SUNDAY AND
MONDAY...TUESDAY AND WEDNESDAY NOT EASY TO FORECAST GIVEN EVEN
FARTHER INTO THE FUTURE. OVERALL...WOULD APPEAR THAT RICH LOW LEVEL
GULF MOISTURE WILL BECOME ESTABLISHED EAST OF THE ROCKIES BY THIS
POINT. BUT TIMING ON ANY DISTURBANCE AND SURFACE BOUNDARY TO FOCUS
CONVECTION JUST CANNOT BE DETERMINED AT THIS POINT.
NEVERTHELESS...PATTERN RECOGNITION WOULD SUGGEST AT LEAST SOME
CHANCE FOR T-STORMS ALONG WITH WARMER TEMPERATURES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 648 AM CDT THU MAY 21 2015

EXPECT SCATTERED HIGH CLOUDS AROUND 25000 FT AGL TODAY WITH BROKEN
CIGS OF 10000 FT AGL SETTING IN TONIGHT. LIGHT RAIN WILL BE
POSSIBLE AT THE KLBF TERMINAL AFTER 09Z TONIGHT WITH CIGS DOWN TO
4000 FT AGL.

&&

.HYDROLOGY...
ISSUED AT 400 AM CDT THU MAY 21 2015

MINOR FLOODING IS EXPECTED TO CONTINUE ALONG THE SOUTH
PLATTE RIVER AT ROSCOE...AND ALONG THE MAINSTEM OF THE PLATTE RIVER
AT BRADY FOR THE NEXT SEVERAL DAYS. AT NORTH PLATTE...THE SOUTH PLATTE
RIVER IS EXPECTED TO REMAIN BELOW THE FLOOD STAGE OF 13.0 FEET FOR
THE FORESEEABLE FUTURE. HOWEVER...THE RIVER IS EXPECTED TO REMAIN IN
THE 11.0 TO 12.3 RANGE OVER THE NEXT SEVERAL DAYS. FLUCTUATIONS IN
RIVER LEVELS WILL REMAIN POSSIBLE OVER THE NEXT SEVERAL DAYS...AS
RAIN IS FORECASTED THIS WEEKEND FOR ALL OF WESTERN AND NORTH CENTRAL
NEBRASKA...AS WELL AS OVER THE SOUTH PLATTE RIVER BASIN IN
NORTHEASTERN COLORADO.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
FROST ADVISORY UNTIL 8 AM CDT /7 AM MDT/ THIS MORNING FOR NEZ004-
005-022>025-035>037-094.

&&

$$

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





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