FXUS63 KOAX 060901
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
400 AM CDT WED APR 6 2011
.DISCUSSION...
...MAIN FORECAST PROBLEM IS POPS...
MID AND UPPER LEVEL HEIGHTS WERE FALLING OVER MOST OF THE WESTERN
CONUS ON THE 00Z UPPER AIR ANALYSIS...AND WATER VAPOR LOOP CONTINUED
TO SHOW A DEEPENING UPPER TROF ON THE WEST COAST. AT THE
SURFACE...COLD FRONT WAS MOVING SOUTH THROUGH THE FORECAST AREA
EARLY THIS MORNING.
THIS FORECAST IS PRIMARILY A FUNCTION OF THE TIMING AND LOCATION OF
THE UPPER TROF AND JET STRUCTURES...AS WELL AS THE SURFACE/LOW LEVEL
FRONTAL ZONE. ABOVE MENTIONED COLD FRONT WILL EVENTUALLY STALL TO
OUR SOUTH AND MOVE BACK NORTH THURSDAY INTO FRIDAY. ALTHOUGH THERE
IS SOME GENERAL AGREEMENT ON THESE FEATURES WITH THE DETERMINISTIC
MODELS...WE ARE SEEING TWO SCENARIOS BEING ADVERTISED BY 12Z
SATURDAY. THE NAM AND ECMWF ARE SIMILAR WITH KEEPING A WEAK SURFACE
LOW OVER THE WESTERN HIGH PLAINS WITH A MORE DIFFUSE WARM FRONT
EXTENDING EAST FROM THE LOW...WHILE THE GFS AND GEM ARE SIMILAR WITH
A MUCH MORE DEFINED BAROCLINIC ZONE CUTTING THROUGH NORTHEAST
NEBRASKA. THE ECMWF IS ABOUT 12 HOURS BEHIND THE GFS WITH PULLING
60+ SURFACE DEWPOINTS NORTH INTO NEBRASKA AND IOWA...BUT BY 00Z
SUNDAY THE GFS AND ECMWF SHOW SURFACE DEWPOINTS IN THE 60S OVER MOST
OF THE FORECAST AREA. THIS REQUIRED A SIGNIFICANT ADJUSTMENT TO THE
GOING FORECAST TO RAISE SATURDAY HIGH TEMPERATURES AND DEWPOINTS.
IF THESE SURFACE DEWPOINTS ARE REALIZED...THE RESULTING
THERMODYNAMIC PROFILE WILL BE QUITE UNSTABLE...WITH ML CAPE VALUES
AT OR ABOVE 2000 J/KG BY SATURDAY AFTERNOON AND CONVECTIVE
INHIBITION VALUES WELL UNDER 100 J/KG.
ALSO ON SATURDAY THE UPPER TROF IS PROGGED TO BE AS FAR EAST AS THE
4-CORNERS PER THE FASTER GFS SOLUTION...AND AS FAR WEST AS THE
NORTHWEST ARIZONA PER THE SLOWER ECMWF AND GEM SOLUTIONS. GIVEN THE
UPPER SUPPORT FROM THE TROF AND THE VERTICAL MOTION ASSOCIATED WITH
THE BAROCLINIC ZONE...THE POPS CURRENTLY FORECAST FOR SATURDAY
AFTERNOON INTO SATURDAY NIGHT LOOK GOOD. DEEP LAYER SHEAR PROFILES
AHEAD OF THE UPPER LOW ARE IMPRESSIVE...ABOVE 60 KNOTS ON ALL
MODELS. WILL EMPHASIZE THE POTENTIAL FOR SEVERE THUNDERSTORMS
SATURDAY AFTERNOON AND EVENING IN THE HAZARDOUS WEATHER OUTLOOK.
THE POP FORECAST FOR THURSDAY APPEARS TO BE ON TRACK AND ONLY MADE
MINOR ADJUSTMENTS FOR TIMING AND TO PUT A LITTLE MORE EMPHASIS ON
THE NORTHERN COUNTIES. THERE HAS BEEN GOOD MODEL AGREEMENT AND
CONSISTENCY FOR RAIN ON THURSDAY AS 850 MB FRONT SURGES NORTH AND
INITIAL SHORTWAVE MOVES THROUGH THE PLAINS. ANY THUNDERSTORMS
SHOULD BE ELEVATED AND CONFINED TO SOUTHERN COUNTIES...WITH FAIRLY
WEAK UPDRAFTS.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
A COLD FRONT WILL CONTINUE TO MOVE SOUTHEAST ACROSS THE CENTRAL
PLAINS THIS MORNING. NORTH WINDS WILL OCCUR AT THE TAF SITES TODAY
BEHIND THE FRONT...WITH WINDS BECOMING LIGHT NORTHEAST OR EAST
TONIGHT. VFR CONDITIONS ARE EXPECTED...WITH MOSTLY VARIABLE MID AND
HIGH LEVEL CLOUDINESS. NO SIGNIFICANT AVIATION ISSUES ARE FORECAST
OVER THE NEXT 24 HOURS.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
DISCUSSION...NIETFELD
AVIATION...MILLER