Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 240500
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1200 AM CDT FRI APR 24 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 239 PM CDT THU APR 23 2015

PRIMARY FORECAST CONCERNS FOR TONIGHT DEAL WITH INCREASING CLOUDS
AND THE CHANCE FOR SHOWERS/THUNDERSTORMS.

MID AFTERNOON SURFACE ANALYSIS SHOWED A RIDGE OF HIGH PRESSURE
STRETCHING FROM THE ND/MN BORDER DOWN INTO NRN AR. WINDS LOCALLY HAD
INCREASED MAINLY INTO THE 10-20 MPH RANGE WITH SOME STRONGER GUSTS.
SOUTH/SOUTHEAST WINDS WILL CONTINUE OVERNIGHT...WHICH WILL BRING AN
INCREASE IN LOW LEVEL MOISTURE. DEWPOINTS CURRENTLY IN THE MID 20S
TO MID 30S SHOULD RISE INTO THE LOWER AND MID 40S. THUS WITH THIS
INCREASE IN MOISTURE...ALONG WITH AN INCREASE IN CLOUDS...EXPECT
LOWS MAINLY 44-48 TONIGHT. RAIN CHANCES WILL RISE INTO THE LIKELY
CATEGORY FOR MUCH OF THE FORECAST AREA LATER TONIGHT.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 239 PM CDT THU APR 23 2015

LEAD SHRTWV TROUGH /CURRENTLY OVER NE NM THIS AFTERNOON/ WILL BE
MOVG THROUGH ERN NEB/WRN IA ON FRI MRNG ASSOCIATED WITH LARGE-
SCALE FORCING FOR ASCENT WITH AN AREA OF 700-300 MB DPVA AND
STRONG LOW TO MID LEVEL WAA. THIS SHOULD LEAD TO INCREASING
SHOWERS AND THUNDERSTORMS FRI MORNING...MOVING EWD INTO IA DURING
THE AFTERNOON. 12Z UPPER AIR ANALYSIS INDICATED AN AREA OF STEEP
MID-LEVEL LAPSE RATES /700-500 MB DELTA-T VALUES OF 20-23 C/ OVER
THE HIGH PLAINS OF WY/CO...AND THESE SHOULD ADVECT EWD OVER THE
NEXT 24 HOURS INTO SRN NEB/KS GIVEN THE FLOW WITHIN THIS LAYER.
THE 12Z 850 MB ANALYSIS INDICATED SOME GULF MOISTURE OVER THE SRN
PLAINS WITH 850 MB MIXING RATIOS OF 10-12 G/KM ALONG THE GULF
COAST. SOME OF THIS MOISTURE WILL MAKE IT NWD INTO ERN NEB/WRN IA
FRI MRNG UNDER THESE INCREASING LAPSE-RATES CREATING INCREASING
INSTABILITY. POINT FORECAST SOUNDINGS FRI MRNG INDICATE AROUND
1000-1200 J/KG OF MUCAPE FOR A PARCEL LIFTED AROUND 1-2 KM.
EFFECTIVE SHEAR THOUGH IS FAIRLY MARGINAL...AROUND 25-30 KT...BUT
COULD BE SUFFICIENT FOR A FEW STRONGER STORMS ON FRI
MRNG...ESPECIALLY IN THE SRN CWA.

BY FRI AFTN WE SHOULD SEE A DECREASE IN PRECIP POTENTIAL AS THE
SHRTWV MOVES TO THE EAST AND THE NEXT UPSTREAM SHORTWAVE IS STILL
WELL TO THE SOUTHWEST. MODELS DIFFER ON THE PLACEMENT OF THE
SURFACE FEATURES ON FRI AFTERNOON WITH THE GFS/GEM MUCH FARTHER
NORTH THAN THE NAM...BUT GIVEN THE MORNING CONVECTION AND
ASSOCIATED CLOUD DEBRIS WE FEEL THE FARTHER SOUTH SOLUTION SHOULD
VERIFY. TSRA SHOULD DEVELOP AHEAD OF THE LOW PRESSURE OVER KS ON
FRI AFTN AND LIFT QUICKLY NEWD FRI EVENING WITH A FEW OF THOSE
POTENTIALLY CLIPPING THE FAR SRN FA. OTHERWISE AS THE LARGE-SCALE
FORCING AGAIN INCREASES FRI NIGHT AS THE SRN CA LOW MOVES THROUGH
THE CNTRL PLAINS WE SHOULD AGAIN SEE AN UPTICK IN SCT SHRA...ENDING
TOWARD SAT MRNG AS THE SYSTEM PULLS OFF TO THE EAST. EXPECT COOL
WEATHER FOR THE WEEKEND WITH NERLY WINDS AND A GOOD DEAL OF
CLOUDS BUT GENERALLY DRY.

THE NEXT SYSTEM DIVING INTO THE WRN US STILL LOOKS TO TAKE A
TRACK WELL TO OUR SOUTH WITH ANY PRECIP...AND WE WILL HAVE A DRY
FORECAST FROM SUN THROUGH NEXT THU. THE WESTERN US RIDGE WILL
EVENTUALLY START TO EXPAND EWD...ESPECIALLY TOWARD THE END OF THE
PERIOD...WHICH SHOULD ALLOW FOR TEMPERATURES TO FINALLY RETURN TO
NEAR OR EVEN ABOVE NORMAL BY THE END OF THE PERIOD.

&&

.AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1157 PM CDT THU APR 23 2015

VFR CIGS NEAR FL050 WILL CONTINUE TO LOWER THROUGH THE
NIGHT...REACHING MVFR LEVELS BETWEEN 09Z AND 12Z AT ALL SITES. A
FEW SHOWERS MAY AFFECT TAF SITES AS WELL BETWEEN 10Z AND 18Z...AND
AN ISOLATED THUNDERSTORM IS POSSIBLE AT KLNK DURING THAT TIME.
CIGS COULD DROP BELOW FL010 FOR A FEW HOURS IN THE MORNING AS
WELL. EXPECT A PERIOD OF VFR CIGS BETWEEN 18Z AND 00Z...BUT CIGS
SHOULD BECOME MVFR AGAIN SHORTLY AFTER 00Z. THUNDERSTORMS COULD
REACH KLNK AND KOMA AFTER 00Z AS STORMS IGNITE ALONG A WARM FRONT
DRAPED ALONG THE KANSAS AND NEBRASKA BORDER...BUT THOSE SHOULD
STAY MAINLY SOUTH OF THE TAF SITES MUCH OF THE 00Z THROUGH 06Z
PERIOD.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$

SHORT TERM...MILLER
LONG TERM...BOUSTEAD
AVIATION...DERGAN



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