FXUS63 KOAX 210819
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
319 AM CDT SAT MAY 21 2011
.DISCUSSION...
THE CHANCE FOR STRONG THUNDERSTORMS THIS AFTERNOON/EVENING...THEN
OFF AND ON THUNDERSTORM CHANCES THROUGH MID WEEK...ARE THE PRIMARY
FORECAST CONCERNS.
SCATTERED SHOWERS WERE MOVING NORTHEAST OF THE CWA THIS MORNING
WHILE MORE LIGHT SHOWERS WERE DRIFTING NORTH FROM NORTHEAST KANSAS
AND NORTHWEST MISSOURI INTO OUR SOUTHERN CWA. SHORTWAVE TROUGH
ROTATING AROUND UPPER LOW IN WYOMING WAS MOVING INTO THE DAKOTAS AND
WILL TAKE AREAS OF SHOWERS WITH IT. HOWEVER ANOTHER SHORTWAVE NOTED
ON WATER VAPOR LOOPS WAS PUSHING INTO WESTERN NEBRASKA THIS
MORNING...AND MAY TRIGGER A FEW SHOWERS IN WESTERN PARTS OF
NORTHEAST NEBRASKA THROUGH THE MORNING. WILL HAVE TO WATCH THIS
FEATURE AS INITIAL FORECAST THINKING WAS FOCUSING ON STRONGER
SHORTWAVE ENTERING THE PLAINS LATER TODAY.
THAT SHORTWAVE WAS PUSHING INTO CENTRAL COLORADO THIS MORNING...AND
IS FORECAST INTO EASTERN NEBRASKA DURING THE AFTERNOON. CLEARING
SKIES AHEAD OF THIS FEATURE WILL ALLOW TEMPERATURES TO APPROACH 80
TODAY AS SURFACE DEW POINTS CLIMB INTO THE LOWER 60S. COOLING ALOFT
WITH SHORTWAVE WILL STEEPEN LAPSE RATES...AND FORECAST SOUNDINGS
INDICATE SURFACE-BASE CAPE VALUES EXCEEDING 2000 J/KG IN EASTERN
NEBRASKA WITH CINH APPROACHING ZERO AFTER 18Z. SHORTWAVE SHOULD ALSO
HELP TO SHARPEN COLD FRONT/DRYLINE WHERE MOISTURE CONVERGENCE WILL
FOCUS CONVECTIVE DEVELOPMENT IN CENTRAL NEBRASKA WITH STORMS
SHIFTING QUICKLY INTO OUR CWA BY MID OR LATE AFTERNOON. MODEST 0-6KM
BULK SHEAR NEAR 30KTS WITH 45 DEGREE ORIENTATION TO FRONTAL
ZONE...COMBINED WITH STEEP LAPSE RATES NEAR 8C/KM AND HIGH
INSTABILITY...SUGGEST RAPIDLY DEVELOPING STORMS WITH SOME SUPERCELLS
CAPABLE OF PRODUCING LARGE HAIL. TORNADO THREAT LOOKS MINIMAL GIVEN
WEAK LOW LEVEL SHEAR. STORMS WILL MOVE EAST AND NORTHEAST THROUGH
THE CWA DURING THE EVENING...TAKING ON A MORE LINEAR MCS LOOK.
MOST OF THIS ACTIVITY SHOULD BE EAST OF THE CWA BY MIDNIGHT. UPPER
LOW OVER WYOMING THIS MORNING WILL BE MOVING THROUGH SOUTH DAKOTA ON
SUNDAY WITH COLD FRONT FROM SATURDAY STORMS PUSHING INTO KANSAS AND
MISSOURI. ONLY SMALL CHANCES FOR PRECIP ON SUNDAY...FOCUSING MAINLY
NEAR UPPER LOW IN NORTHEAST NEBRASKA AND NEAR FRONTAL BOUNDARY IN
FAR SOUTHEAST NEBRASKA AND SOUTHWEST IOWA.
FRONT WILL GRADUALLY SHIFT NORTH ON MONDAY INTO TUESDAY AS UPPER
TROUGH IN THE SOUTHWESTERN CONUS BEGINS WORKING INTO MID AMERICA.
LOWERING PRESSURE ALONG THE LEE OF THE ROCKIES WILL TEND TO LIFT
FRONT INTO NORTHERN KANSAS OR SOUTHERN NEBRASKA...WITH SHORTWAVES
RIDING OVER FRONTAL ZONE PROVIDING CHANCES FOR SHOWERS OR STORMS
ACROSS MUCH OF THE CWA. THE BEST CHANCES WILL BE IN THE SOUTH NEARER
THE FRONT...BUT A GRADUAL SHIFT NORTH INTO TUESDAY NIGHT LOOKS
LOGICAL. GFS AND ECMWF BOTH SHOW UPPER TROUGH MOVING THROUGH THE
PLAINS ON WEDNESDAY...SO WILL END PRECIP CHANCES THEN.
TEMPERATURES SHOULD REACH THE UPPER 70S OR LOWER 80S SATURDAY AND
SUNDAY WITH A GRADUAL COOL DOWN INTO THE 60S BY TUESDAY AND
WEDNESDAY AS COLD FRONT IS TO OUR SOUTH AND OVERRUNNING
CLOUDS/PRECIP KEEP TEMPS BELOW NORMAL.
DERGAN
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
VARIABLE CONDITIONS LIKELY THROUGH ABOUT 14Z AS PRECIP ARM LIFTS
NORTHEAST AHEAD OF CENTRAL NEBRASKA SHORT WAVE. LOWER CLOUDS
DEVELOPING AS SKIES CLEAR UPSTREAM OF THE AREA AT 06Z WITH LIFR CIGS
AND VSBY REPORTED AROUND KGRI. A PERIOD OF IFR OR LIFR POSSIBLE
THROUGH 14Z AS HIGH CLOUDS MOVE OUT THEN MVFR TO VFR CONDITIONS WITH
POSSIBLE ISOLATED SHOWERS 18Z-00Z.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$