FXUS63 KOAX 200752
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
252 AM CDT FRI MAY 20 2011
.DISCUSSION...
THUNDERSTORM CHANCES THE NEXT COUPLE OF DAYS ARE THE PRIMARY
FORECAST CONCERNS.
LARGE UPPER LOW CONTINUED TO MAKE SLOW PROGRESS THROUGH THE CENTRAL
ROCKIES. A POTENT JET SEGMENT ROTATING AROUND THE LOW INTO THE
PLAINS HELPED TO IGNITE THUNDERSTORMS ALONG DRY LINE IN WESTERN
KANSAS DURING THE LATE AFTERNOON...WITH STRONG WARM ADVECTION AIDING
IN CONVECTION ACROSS EASTERN NEBRASKA. STORMS EVENTUALLY FORMED INTO
A LINE MOVING EAST AND NORTHEAST INTO EASTERN NEBRASKA...AND CURRENT
MOVEMENT WILL TAKE MOST OF THE STRONG CONVECTION OUT OF THE CWA BY
SHORTLY AFTER SUNRISE. HOWEVER LINGERING SHOWERS OR STORMS WILL
LIKELY LAST THROUGH MID MORNING.
THE MORNING CONVECTION AND ASSOCIATED CLOUD COVER WILL CERTAINLY
AFFECT RECOVERY OF INSTABILITY FOR POTENTIAL AFTERNOON CONVECTION.
STRONG MID LEVEL FLOW WILL CONTINUE TO INDUCE SURFACE LOW PRESSURE
IN THE HIGH PLAINS...WHICH SHOULD PROMOTE STRONG SOUTHERLY FLOW IN
THE SOUTHERN PLAINS. WARM FRONT CURRENTLY IN CENTRAL KANSAS IS
EXPECTED TO EVENTUALLY LIFT NORTH AT LEAST TO THE NEBRASKA
BORDER...WITH MODELS PUSHING IT EVEN FARTHER NORTH. 60S DEW POINTS
WILL SURGE NORTH WITH THE FRONT...AND ANY BREAKS IN CLOUD COVER WILL
ALLOW TEMPERATURES TO REACH THE MIDDLE 70S. HOWEVER MID LEVEL LAPSE
RATES ARE FORECAST WELL BELOW 7C/KM ACROSS EASTERN NEBRASKA AND
WESTERN IOWA WITH MAXIMUM VALUES WELL TO THE WEST AT 00Z. SO EXPECT
BULK OF STRONG CONVECTION TO DEVELOP ALONG DRYLINE/TROUGH FROM
CENTRAL NEBRASKA THROUGH CENTRAL KANSAS IN THE LATE AFTERNOON...
AIDED BY STRONG SHORTWAVE ROTATING INTO THE PLAINS. THIS ACTIVITY
SHOULD MOVE NORTHEAST INTO OUR WESTERN CWA DURING THE EARLY
EVENING...THEN THROUGH THE REST OF THE AREA OVERNIGHT. GIVEN
RELATIVELY MODEST INSTABILITY...AM NOT EXPECTING WIDESPREAD
SEVERE...WITH HAIL IN ELEVATED STORMS THE MOST LIKELY.
SHOWERS AND THUNDERSTORMS SHOULD BE MOVING NORTHEAST OF THE AREA
SATURDAY MORNING. AGAIN ATMOSPHERE WILL ATTEMPT TO RELOAD FOR
AFTERNOON STORMS. MODELS SUGGEST SURFACE BASED CAPE WILL APPROACH
2000 J/KG IN OUR SOUTHERN CWA...BUT LITTLE SURFACE CONVERGENCE TO
FOCUS ON. WILL MAINTAIN A CHANCE FOR AFTERNOON STORMS ACROSS THE
WHOLE CWA...BUT THE BEST CHANCE FOR STRONG STORMS WILL EXIST IN OUR
SOUTH.
AM THINKING SUNDAY WILL BE MOSTLY DRY AS UPPER LOW SHIFTS INTO THE
NORTHERN PLAINS AND WEST OR SOUTHWEST SURFACE FLOW SWEEPS MOISTURE
NORTHEAST OF THE CWA. A FEW AFTERNOON SHOWERS ARE STILL POSSIBLE IN
OUR NORTH WHERE COOLER MID LEVEL TEMPS WILL RESIDE.
THE CHANCE FOR SHOWERS AND THUNDER SHOULD INCREASE AGAIN ON MONDAY
WITH COLD FRONT ON BACK SIDE OF UPPER LOW DROPPING SOUTH INTO
NEBRASKA AND IOWA. GFS SHOWS THAT FRONT INTO SOUTHEAST NEBRASKA
MONDAY AFTERNOON...SO HAVE HIGHEST CHANCES THERE. FRONT PUSHES
SLOWLY SOUTH ON TUESDAY AND WEDNESDAY...WITH OVERRUNNING SHOWERS
POSSIBLE INTO MID WEEK. HAVE NOT CHANGED FORECAST FOR THE END OF THE
WEEK WITH DRIER CONDITIONS EXPECTED.
DERGAN
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
MORNING SHOWERS AND THUNDERSTORMS WILL AFFECT EASTERN NEBRASKA TAF
SITES THROUGH ABOUT 15Z OR SO. ASSOCIATED IFR CIGS/VSBYS WITH
THOSE STORMS WILL PERSIST WITH THE RAIN...WITH IMPROVEMENT TO MVFR
CIGS BETWEEN 15Z AND 18Z. CIGS NEAR FL025 WILL GRADUALLY LIFT TO
VFR BETWEEN 18Z AND 21Z. MORE THUNDERSTORMS ARE LIKELY NEAR OR
SLIGHTLY AFTER 00Z WITH ASSOCIATED IFR CONDITIONS AGAIN POSSIBLE.
THIS SECOND ROUND OF THUNDERSTORMS SHOULD BE MOVING OUT OF EASTERN
NEBRASKA BY 12Z SATURDAY WITH CONDITIONS IMPROVING TO VFR BY 18Z
SATURDAY.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$