Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 042335 AAA
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
635 PM CDT MON MAY 4 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 353 PM CDT MON MAY 4 2015

A WEAK DISTURBANCE AND MID-LEVEL WARM FRONT WILL PROVIDE FOR
ADDITIONAL SHOWERS AND THUNDERSTORMS THIS EVENING AND OVERNIGHT.
THE 04.12Z NAM SEEMS TO BE HANDLING THE CURRENT SITUATION
WELL...AND THUS WAS CONSIDERED FOR THE POP FORECAST OVERNIGHT. AT
THIS POINT...BESIDES OFF AND ON SCATTERED SHOWERS...THE GREATEST
CHANCES OF POPS OVERNIGHT COME DURING THE PRE-DAWN HOURS ACROSS
OUR SOUTHERN ZONES...THEN THE ACTIVITY LIFTS NORTH THROUGH 15Z. AT
THIS POINT WILL GENERALLY KEEP CHANCES AT 50% OR LESS OVERNIGHT.
ONLY A WEAK CONVECTIVE ELEMENT IS SHOWN IN REGIONAL PROXIMITY
SOUNDINGS OVERNIGHT...SO AT MOST A FEW CG STRIKES WOULD BE
ANTICIPATED.

A WARM FRONT WILL LIFT NORTH EARLY TUESDAY...PROVIDING A FOCUS FOR
ADDITIONAL SHOWERS AND STORMS.  MODELS REMAIN IN DECENT AGREEMENT
WITH TIMING SUGGESTING THE ARRIVAL EARLY TUESDAY AFTERNOON AS
DIFLUENCE ALOFT INCREASES WITH THE APPROACH OF A LEAD CENTRAL
ROCKIES SHORTWAVE.  THE MODELS INDICATE SUFFICIENT DESTABILIZATION
FOR THUNDERSTORM DEVELOPMENT...BUT BULK SHEAR INDICES ARE LESS THAN
OPTIMAL FOR ORGANIZED STORM ROTATION.  THUS WIDESPREAD SEVERE STORMS
ARE NOT ANTICIPATED...BUT A FEW STRONG STORMS TUESDAY AFTERNOON
CANNOT BE OVERLOOKED.  THE CONTRIBUTION OF THE INSTABILITY IS SPREAD
OVER A LARGE DISTANCE OF THE TROPOSPHERE AND GIVEN THAT PWATS ARE
SHOWN TO INCREASE TO VALUES OF ABOVE THE 99TH PERCENTILE...HEAVY
RAINFALL IS ANTICIPATED UNDER ANY CONVECTIVE STORM.  THE GREATEST
THREAT OF HEAVY RAINFALL WILL OCCUR BEYOND 21Z TUESDAY AFTERNOON
WHEN WARM CLOUD DEPTHS INCREASE ABOVE 6K FEET.  THE INHERITED
FORECAST INCLUDED LIKELY POPS TUESDAY AFTERNOON...WHICH AT THIS
POINT THERE/S NO REASON TO DEVIATE GIVEN THE SITUATION.

TEMPERATURES WILL BE MODERATED BY THE PRESENCE OF CLOUDS AND
MOISTURE...LOWS WILL FALL INTO THE 40S TO LOWER 50S OVERNIGHT...WITH
HIGHS WARMING INTO THE 60S TO LOWER 70S TOMORROW...ESPECIALLY IF THE
SUN IS ABLE TO PEEK OUT.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 353 PM CDT MON MAY 4 2015

A LARGE UPPER LEVEL LOW PRESSURE SYSTEM WILL BE DIGGING SOUTHEAST
TOWARD THE CENTRAL GREAT BASIN BY FRIDAY. IN ADVANCE OF THIS
SYSTEM...A POTENT NEGATIVELY TILTED PV ANOMALY WILL EJECT NORTHEAST
FROM THE DESERT SOUTHWEST ACROSS THE AREA TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT. THIS LEAD PV ANOMALY WILL HELP TO INCREASE
SOUTHERLY FLOW...WITH ABUNDANT LOW LEVEL GULF MOISTURE STREAMING
NORTHWARD INTO THE CENTRAL AND NORTHERN PLAINS.

THE RAIN EXPECTED DURING THE DAY TUESDAY WILL DECREASE SOMEWHAT IN
COVERAGE TUESDAY NIGHT AS THE BEST LIFT SHIFTS NORTH INTO THE
NORTHERN PLAINS. STILL CANNOT RULE OUT SHOWERS OR A FEW STORMS WITH
GOOD MOISTURE ADVECTION AND SOME LIFT PRESENT THROUGH THE
NIGHT.

THE BEST DYNAMICS ASSOCIATED WITH THE PV ANOMALY WILL CROSS THE AREA
WEDNESDAY. STILL NOT EXPECTING MUCH IN THE WAY OF DESTABILIZATION
DURING THE AFTERNOON AHEAD OF THE COLD FRONT DUE TO ABUNDANT LOW
LEVEL MOISTURE AND LOW STRATUS CLOUD COVER. THE RESULT WOULD BE
LIMITED SURFACE BASED CONVECTIVE DEVELOPMENT. THE MORE LIKELY
SCENARIO WILL BE FOR SURFACE BASED STORMS TO DEVELOP NEAR A TRIPLE
POINT ACROSS NORTHWEST KANSAS WHERE LESS LOW CLOUD COVER AND BETTER
HEATING WILL OCCUR. EXPECT THESE STORMS TO QUICKLY SPREAD NORTH AND
EAST AND BECOME MORE ELEVATED. A FEW OF THESE COULD BE SEVERE WITH
LARGE HAIL BEING THE MAIN THREAT.

STILL ON TRACK FOR A LULL IN THE PRECIPITATION LATER WEDNESDAY NIGHT
INTO THURSDAY. THEN FRIDAY INTO THE WEEKEND...THE LARGE UPPER LEVEL
LOW WILL MOVE EAST FROM THE CENTRAL GREAT BASIN TOWARD THE CENTRAL
PLAINS. ECMWF AND GEFS CONTINUE TO BE IN VERY GOOD AGREEMENT WITH
THE CLOSED LOW TRACKING SLOWLY ACROSS COLORADO AND THEN TURN
NORTHEAST AND CROSS NEBRASKA. VERY STRONG MOISTURE ADVECTION AHEAD
OF THIS SYSTEM...AND HIGH CONFIDENCE THAT RAIN WILL OCCUR FRIDAY
NIGHT INTO SATURDAY. THE GEFS AND ECMWF NOW LINGER THE SYSTEM INTO
SUNDAY...SO WILL RAISE POPS FOR THAT DAY. MONDAY SHOULD BE A DRY DAY
AS THE SYSTEM MOVES NORTHEAST AWAY FROM THE REGION.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 635 PM CDT MON MAY 4 2015

MVFR CIGS ASSOCIATED WITH RAIN ALONG I-80 WILL CONTINUE FOR A FEW
MORE HOURS. ONCE THE RAIN ENDS...A PERIOD OF VFR COULD DEVELOP FOR
A FEW HOURS ALSO. THE RAP MODEL THEN SHOWS A RAPID INCREASE IN
MOISTURE WHICH IS EXPECTED TO LOWER CIGS AGAIN TO MVFR WITH AREAS
OF IFR TOWARD MORNING AS A SECOND BATCH OF RAIN MOVES UP FROM THE
SOUTH. THE MODELS SUGGEST THIS RAIN COULD LAST THROUGHOUT THE DAY
SOUTH OF VALENTINE.

&&

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

$$

SHORT TERM...JACOBS
LONG TERM...TAYLOR
AVIATION...CDC






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