Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 201716
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1216 PM CDT SUN APR 20 2014

.UPDATE...
ISSUED AT 1208 PM CDT SUN APR 20 2014

WEAK WIND SHIFT THAT WAS A COLD FRONT YESTERDAY HAS DRIFTED
SLIGHTLY NORTH EARLY THIS AFTERNOON...AND EXTENDED ACROSS
NORTHEAST NEBRASKA. MODERATE CUMULUS WAS FORMING NEAR THIS
BOUNDARY...AND COULD BLOSSOM INTO SOME SHOWERS THIS AFTERNOON.
OTHERWISE MID LEVEL SHORTWAVE WAS CLEARLY NOTED ON WATER VAPOR
IMAGERY LIFTING NORTHEAST FROM WESTERN KANSAS. THIS FEATURE IS
EXPECTED TO SPAWN MORE SHOWERS AND ISOLATED THUNDERSTORMS ACROSS
THE SOUTHERN HALF OF THE CWA LATE THIS AFTERNOON AND EVENING. HAVE
RECONFIGURED PRECIP CHANCES TO FOLLOW THIS THINKING. SEVERE STORMS
ARE STILL NOT EXPECTED WITH THIS ACTIVITY AS INSTABILITY AND SHEAR
REMAIN MINIMAL.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 305 AM CDT SUN APR 20 2014

PRECIPITATION CHANCES INTO MONDAY CONTINUE TO BE PRIMARY CHALLENGE
IN SHORT TERM.

AT THE SURFACE A STALLED BOUNDARY FROM NEAR COLUMBUS TO SIOUX CITY
AT 08Z IS FORECAST TO LIFT A BIT NORTH AND/OR WASH OUT TODAY AS
SHORTWAVE ENERGY TRACKS ACROSS THE NRN U.S. AND A SRN TROUGH
MOVES A LITTLE NORTH OF EAST ACROSS SRN PLAINS. FORECAST AREA
GENERALLY REMAINS IN BETWEEN THESE SYSTEMS TODAY/TONIGHT...ALTHOUGH
A WEAK LOBE APPARENTLY IS/WILL CONTINUE TO PIVOT UP INTO FA FROM
SRN SYSTEM. HOWEVER...MOISTURE REMAINS ON LOW SIDE ESPECIALLY
BELOW H85 AND ANY MOISTURE THERE IS WAS HAVING A HARD TIME
OVERCOMING MODEST CAP CURRENTLY IN PLACE PER 00Z OAX/LBF/TOP
SOUNDINGS. MODEL QPF HAS BEEN POOR...GENERALLY OVERDOING
PCPN...AND CONFIDENCE IN VARIOUS SOLUTIONS THEY GIVE ARE LOW TO
SAY THE LEAST. THAT SAID...THERE IS SOME WEAK CONVERGENCE NEAR
BOUNDARY AND MID LEVEL MOISTURE DOES SEEM A BIT MORE THIS MORNING
GIVEN MID DECK CIGS AT SOME LOCALS AND ACCAS APPEARANCE TO MORNING
STLT IMAGERY. AND WITH HEATING WOULD SUSPECT SOME INCREASE IN
POPS ARE IN ORDER LATER THIS AFTN THROUGH THIS EVENING AND THEN
OVERNIGHT AS NRN WAVE SENDS COLD FRONT INTO ECNTRL ZONES. OVERALL
THOUGH TRIMMED MOST POPS A BIT.

IT ALSO LOOKS LESS LIKELY THAT TEMPERATURES TODAY WILL BE HELD
DOWN SUBSTANTIALLY BY WIDESPREAD PRECIP OR CONTINUAL THICK
CLOUDINESS WITH EVEN LAST HOLD-OUT ECMWF COMING AROUND TO WARMER
READINGS. GENERALLY BOOSTED A FEW DEGREES.

SOME MOISTURE/INSTABILITY LAGS ACROSS SERN ZONES MONDAY
AFTN...POSSIBLY EVEN BEHIND WEAKENING COLD FRONT PER NAM. BECAUSE
OF THAT LINGERED A SLIGHT CHC FAR SE INTO MID AFTN. OTHERWISE PCPN
CHANCES WILL BE DECREASING BEHIND FRONT AS WINDS AND PROBABLY
FIRE DANGER INCREASE AGAIN AS DEWPOINTS LOWER INTO THE 30S/LOW
40S AND HIGHS REACH 70 OR BETTER.

RETURN FLOW EXPECTED TUESDAY WITH SIMILAR READINGS TO MONDAY.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 255 AM CDT SUN APR 20 2014

WARM ADVECTION PRECIPITATION CHANCES STILL LOOK TO BE ON THE
INCREASE TUE NIGHT/WED PERIOD AS STRONG LOW LEVEL JET OVERSPREADS
AREA IN ADVANCE OF DEEPENING UPPER TROUGH. GFS/ECMWF HAVE TRENDED
WITH LESS COVERAGE FOR PART OF WEDNESDAY AND HAVE RESPONDED WITH
WARMER GUIDANCE VALUES...MOST NOTABLY THE ECMWF. BOOSTED HIGHS A
FEW DEGREES OVER PREV FORECAST/EARLIER MODEL BLEND ON WED.
ALTHOUGH SOME UNCERTAINTY ON HOW FAR EAST FRONT PUSHES DURING THE
DAY WED...STILL APPEARS SOME SEVERE WEATHER THREAT WILL
EXIST...POSSIBLY A BIT FARTHER SE THAN IT LOOKED EARLIER.

ALTHOUGH WE`LL HAVE TO OVERCOME A STRONG WRLY-DOWNSLOPE COMPONENT
TO LOW LEVEL WINDS BEHIND FRONT ON THURSDAY...HEATING AND SOME
MOISTURE LAGS AS MAIN CIRC CENTER...BY THEN THE PROBABLY
DEVELOPED...UPPER LOW WILL LIKELY REMAIN NW OF THE FORECAST AREA.
THUS THE LINGERING POPS PER PREV FCST STILL LOOK IN ORDER.

SOMEWHAT COOLER TEMPS ALSO IN ORDER FRIDAY INTO SATURDAY AS UPPER
TROUGH AXIS SHIFTS EWD...BUT AMOUNT OF WHICH WILL LIKELY CHANGE AS
EXACT LATITUDE IT DOES EVENTUALLY SHIFT BECOMES MORE CERTAIN.
ALSO LATE NEXT WEEKEND...NEW DAY 7...LOOKS POTENTIALLY INTERESTING...
ESPECIALLY PER 00Z ECMWF.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1208 PM CDT SUN APR 20 2014

GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH MONDAY MORNING. WEAK
COLD FRONT ACROSS NORTHEAST NEBRASKA WILL EVENTUALLY MOVE
SOUTHEAST LATER TONIGHT...WITH NORTH WINDS BEHIND THE FRONT
REACHING KOFK BEFORE 12Z AND KOMA/KLNK SLIGHTLY AFTER. A FEW
SHOWERS COULD AFFECT TAF SITES THIS AFTERNOON AND EVENING...WITH
AN ISOLATED THUNDER ALSO POSSIBLE BUT NOT MENTIONED IN TAFS AS
CHANCES ARE RELATIVELY SMALL. BETTER CHANCES FOR SHOWERS OR STORMS
WILL COME WITH THE COLD FRONT OVERNIGHT. STILL LOW LEVEL MOISTURE
IS LIMITED SO GENERALLY VFR CIGS/VSBYS ARE EXPECTED EXCEPT RIGHT
UNDER THE STRONGER STORMS. CLEARING SKIES AND 15 TO 25KT NORTH
WINDS ARE EXPECTED BY 18Z MONDAY.

&&

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

$$

UPDATE...DERGAN
SHORT TERM...CHERMOK
LONG TERM...CHERMOK
AVIATION...DERGAN



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