FXUS63 KOAX 070833
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
333 AM CDT SAT MAY 7 2011
.DISCUSSION...
THUNDERSTORM CHANCES INTO EARLY NEXT WEEK ARE THE PRIMARY FORECAST
CONCERNS.
WEAK MID LEVEL IMPULSE MOVING THROUGH NORTHWEST FLOW WAS TRIGGERING
LIGHT SHOWERS IN THE SOUTHERN CWA THIS MORNING. THIS ACTIVITY SHOULD
BE EXITING OUR AREA BY SUNRISE. THEN WEAK SURFACE HIGH PRESSURE WILL
SETTLE OVER THE CWA THIS AFTERNOON. PARTLY CLOUDY SKIES WILL ALLOW
PLENTY OF INSOLATION TO OFFSET LIGHT NORTH WINDS...PUSHING TEMPS
WELL INTO THE 70S THIS AFTERNOON.
UPPER FLOW WILL BEGIN A TRANSITION TO A WESTERN TROUGH SETUP LATER
TODAY AND TONIGHT...BRINGING SOUTHWEST FLOW OVER THE MIDDLE OF
THE COUNTRY THROUGH THE MIDDLE OF NEXT WEEK. SEVERAL IMPULSES
EJECTING THROUGH THE FLOW WILL BRING CONVECTIVE CHANCES TO PARTS
OF THE CWA FROM TIME TO TIME INTO MONDAY. OUR FIRST CHANCE COMES
TONIGHT AS AN IMPULSE RIDES THROUGH THE DAKOTAS. AN INCREASING LOW
LEVEL JET WILL DRIVE HIGHER THETA-E AIR INTO NORTHEAST NEBRASKA
WHERE CONVERGENCE BEGINS...BUT IS MAXIMIZED FARTHER NORTH INTO
SOUTH DAKOTA. STILL EXPECT AT LEAST A CHANCE FOR STORMS AFTER
MIDNIGHT IN OUR NORTH...WITH THAT CHANCE SHIFTING EAST AND NORTH
WITH TIME SUNDAY MORNING.
ANOTHER SHORTWAVE WILL EJECT INTO THE PLAINS SUNDAY AFTERNOON...
FOCUSING CONVECTION TO OUR WEST IN CONVERGENCE ZONE ALONG DRYLINE.
SOME STORMS COULD WORK INTO OUR WESTERN CWA BY SUNSET. ALSO...A
DEVELOPING WARM FRONT IN EASTERN KANSAS MAY TRIGGER STORMS THAT
COULD WORK INTO SOUTHEAST NEBRASKA IN THE AFTERNOON. BUT BETTER
CHANCES COME OVERNIGHT AS WARM FRONT LIFTS/BRIDGES NORTH INTO THE
CWA. STRONG 50+KT LOW LEVEL WILL IMPINGE ON THAT BOUNDARY PROVIDING
LIFT FOR CONVECTION. MOISTURE RETURN WILL BE ROBUST BY THEN...AND
MODELS ADVERTISE 850 LIFTED INDICES OF -5 TO -10C AND OVER 2000 J/KG
OF ELEVATED CAPE ALONG WITH 30KTS OF 0-6KM BULK SHEAR. THUS A
THREAT OF LARGE HAIL EXISTS IF STORMS DO FIRE.
MORNING STORMS COULD LINGER IN THE NORTHERN HALF OF THE CWA
MONDAY...BUT WARMING MID LEVEL TEMPERATURES SHOULD SQUELCH ANY
FURTHER ACTIVITY THROUGH THE DAY. THE WARMER MID LEVEL TEMPS AND
SOUTHWESTERLY 850 FLOW SHOULD PUSH AFTERNOON HIGHS TOWARD 90 IN
MUCH OF THE CWA.
THE FORECAST FOR THE MIDDLE OF NEXT WEEK HAS BECOME A LITTLE MORE
COMPLICATED AS GFS AND ECWMF HAVE PARTED WAYS IN HANDLING WESTERN
TROUGH MOVING INTO THE PLAINS. THE GFS SHOWS AN UPPER LOW WORKING
INTO THE NORTHERN PLAINS ON TUESDAY...PUSHING A BASICALLY DRY COLD
FRONT THROUGH THE CWA TUESDAY. THE ECMWF HOLDS THIS LOW FURTHER
WEST...AND MAINTAINS SOUTHERLY FLOW ACROSS THE CWA INTO
WEDNESDAY. HOWEVER BOTH MODELS SUGGEST A DRY FORECAST TUESDAY...SO
HAVE REMOVED CHANCES THEN. WILL MAINTAIN A CHANCE FOR STORMS ON
WEDNESDAY...MORE IN LINE WITH ECMWF...AND BUMPED UP TEMPERATURES
JUST A TAD.
THE REST OF THE WEEK SHOULD BE SOMEWHAT COOLER BEHIND UPPER TROUGH
AND COLD FRONT...WITH HIGHS IN THE 60S AND 70S.
DERGAN
&&
.AVIATION...
06Z TAFS
VFR CONDITIONS WILL PREVAIL AT ALL TERMINALS THRU THE FCST PD.
DEE
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$