Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 201753
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1253 PM CDT WED MAY 20 2015

.SYNOPSIS...
ISSUED AT 320 AM CDT WED MAY 20 2015

THE 07Z WATER VAPOR IMAGERY INDICATED A CLOSED LOW OVER WESTERN
NEBRASKA. THE BEST POTENTIAL VORTICITY IS LOCATED OVER THE SANDHILLS
WHICH PROVIDES SOME UPPER SUPPORT FOR AN INVERTED TROUGH ACROSS OVER
THE MISSOURI VALLEY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 320 AM CDT WED MAY 20 2015

AS THE INVERTED TROUGH MOVES OUT OF THE MISSOURI VALLEY...RAIN WILL
END IN NORTH CENTRAL NEBRASKA BY MIDDAY TO EARLY AFTERNOON.
CLOUDINESS WILL SCATTER OUT BY EARLY EVENING. AS A RESULT...NEARLY
CLEAR SKIES ARE LIKELY IN CENTRAL AND NORTH CENTRAL NEBRASKA AND AT
LEAST PATCHY FROST CAN BE EXPECTED POSSIBLY AS FAR WEST AS THE
NORTHEAST PANHANDLE. AT THIS TIME...IT DOES NOT APPEAR THAT IT WILL
BE WIDESPREAD ENOUGH TO WARRANT AN ADVISORY. THAT WILL NEED TO BE
REVISITED WITH THE DAYTIME ISSUANCE OF THE FORECAST PACKAGE. IN
SOUTHWEST NEBRASKA AND THE WESTERN SANDHILLS... CLOUDINESS WILL
INCREASE AGAIN...THUS KEEPING TEMPERATURES ABOVE FROST THRESHOLDS.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 320 AM CDT WED MAY 20 2015

SURFACE HIGH PRESSURE WILL BE CENTERED IN THE FORECAST AREA
THURSDAY. CONDITIONS WILL BE QUITE PLEASANT COMPARED TO THE LAST
FEW DAYS...BUT HIGHS WILL STILL BE A BIT BELOW NORMAL FOR THIS
TIME OF YEAR. HIGHS WILL RANGE FROM NEAR 60 DEGREES IN THE
PANHANDLE TO THE UPPER 60S ACROSS NORTHEAST/EASTERN PORTIONS OF
NORTH CENTRAL NEBRASKA. SOME INCREASE IN MID LEVEL
MOISTURE/CLOUDINESS WILL OCCUR ACROSS WESTERN NEBRASKA...KEEPING
THOSE AREAS A FEW DEGREES COOLER.

THE NEXT IN THE SERIES OF LONG WAVE TROUGHS/CLOSED LOWS WILL BE
MOVING ONSHORE THE WEST COAST FRIDAY. A LEAD SHORTWAVE WILL BE
ROTATING NORTHEAST THROUGH THE AREA LATE THURSDAY NIGHT AND FRIDAY
AHEAD OF THIS FEATURE. RAIN IS SHOWN TO DEVELOP IN THE MODELS AS
ISENTROPIC LIFT AND MOISTURE TRANSPORT INCREASE LATE THURSDAY
NIGHT INTO FRIDAY. THE GFS AND ECMWF ARE THE MOST AGGRESSIVE WITH
THE ONSET OF RAIN ACROSS SOUTHWEST NEBRASKA FRIDAY MORNING...THEN
SPREADING NORTH AND EAST THROUGH THE DAY. THE NAM IS MUCH DRIER
DUE TO AN ABUNDANCE OF LOW LEVEL DRY AIR WHICH IS SLOW TO BE
DISLODGED. FOR THIS REASON WILL NOT INCREASE POPS ANY THIS
FORECAST CYCLE...AND IN FACT WILL TRIM THE NORTHEAST EDGE OF THE
RAIN BACK SOME TO THE SOUTHWEST FRIDAY MORNING. DID KEEP THE
MENTION OF THUNDER THROUGH THE DAY FRIDAY...BUT INSTABILITY IS
QUITE MEAGER AND ONLY ISOLATED THUNDERSTORMS ARE EXPECTED.

MOISTURE ADVECTION REALLY INCREASES FRIDAY NIGHT INTO
SATURDAY...AND AS LARGE SCALE LIFT FROM THE APPROACHING WEST COAST
TROUGH OVERSPREADS THE AREA...NUMEROUS SHOWERS AND THUNDERSTORMS
SHOULD RESULT. HARD TO PIN DOWN EXACTLY WHEN AND WHERE...AS REALLY
NOT A DEFINED SURFACE BOUNDARY IN THE AREA TO FOCUS CONVECTION ON.
THE MOST LIKELY SCENARIO FOR US WILL BE AN INCREASE IN NOCTURNAL
CONVECTION BOTH FRIDAY NIGHT AND SATURDAY NIGHT DRIVEN BY THE
SOUTHERLY LOW LEVEL JET. THE GFS DOES INDICATE A SURFACE TROUGH
MOVING EAST INTO WESTERN NEBRASKA SATURDAY AFTERNOON...WHICH COULD
BE A TRIGGER FOR STRONGER OR PERHAPS SEVERE STORMS. THE ECMWF
HOLDS THIS FEATURE MUCH FARTHER TO THE SOUTHWEST WELL OUT OF OUR
AREA. SO SEVERE SOMEWHAT IN QUESTION...WITH THE BIGGER THREAT AT
THIS POINT LIKELY TO BE IN THE FORM OF LOCALLY HEAVY RAIN.
SUNDAY...AGAIN MODELS DIFFER. GFS MORE AGGRESSIVE AND PUSH THE
AFOREMENTIONED SURFACE TROUGH EAST THROUGH THE AREA...BUT THE ECMWF
SLOWER AND HANGS THE SURFACE TROUGH THROUGH THE HEART OF THE
FORECAST AREA. AGAIN THIS LIKELY TO BE A FOCUS FOR STRONGER STORM
ACTIVITY. WILL CONTINUE TO MONITOR THE LATEST TRENDS IN THE MODELS
REGARDING ANY SEVERE POTENTIAL FOR THE UPCOMING HOLIDAY WEEKEND.

BY EARLY NEXT WEEK...THE FLOW ALOFT ATTEMPTS TO BECOME SOMEWHAT
MORE ZONAL COMPARED TO DAYS PAST. APPEARS AN EAST TO WEST STATIONARY
FRONT WILL BECOME ESTABLISHED...AND AS WAVES PASS WITHIN FLOW
ALOFT...MORE SHOWERS AND THUNDERSTORMS QUITE POSSIBLE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1248 PM CDT WED MAY 20 2015

MVFR CIGS WILL CONTINUE ACROSS ALL OF WESTERN AND NORTH CENTRAL
NEBRASKA THROUGH LATE WEDNESDAY AFTERNOON. CIGS HAVE BEEN TRENDING
HIGHER OVER THE LAST SEVERAL HOURS AND SHOULD RISE INTO THE VFR
CATEGORY PAST 21Z. GRADUAL CLEARING WILL COMMENCE AFTER DARK
ACROSS NORTHERN NEBRASKA AND SPREAD SOUTH THROUGH THE OVERNIGHT.
STILL SOME UNCERTAINTY WITH HOW FAR SOUTH THE CLEARING WILL
ADVANCE...BUT VFR CIGS ARE EXPECTED WITH ANY CLOUD COVER OVERNIGHT
INTO THURSDAY MORNING.

&&

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

&&

$$

SYNOPSIS...SPRINGER
SHORT TERM...SPRINGER
LONG TERM...TAYLOR
AVIATION...MARTIN







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