FXUS63 KOAX 201945
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
245 PM CDT SAT AUG 20 2011
.SHORT TERM...TONIGHT
MAIN QUESTION FOR TONIGHT WILL BE FOG DEVELOPMENT AND ASSOCIATED
CLOUD COVER. ISOLATED SHOWERS WILL MOVE EAST AND SOUTH OF THE AREA
LATER THIS AFTERNOON...WITH HIGH PRESSURE BRINGING CLEARING SKIES
AND LIGHT WINDS TONIGHT. DUE TO RAINFALL FROM PREVIOUS DAYS...EXPECT
SOME PATCHY FOG TO DEVELOP. TEMPERATURES WILL FALL INTO THE UPPER
50S AND LOWER 60S FOR LOWS TONIGHT.
.LONG TERM...SUNDAY THROUGH SATURDAY
MID LEVEL RIDGE ACROSS THE PLAINS SUNDAY IS FORECAST BY THE GFS
AND EUROPEAN TO RETROGRADE TOWARD THE FOUR CORNERS THROUGH
TUESDAY. THIS WILL ALLOW CYCLONIC NORTHWEST FLOW TO REMAIN IN
PLACE PROVIDING PERIODIC OPPORTUNITIES FOR CONVECTION AS EMBEDDED
SHORT WAVE ENERGY MOVES OVERHEAD.
12Z GEFS MEAN PRECIPITABLE WATER VALUES CLIMB ABOVE 1.5 INCHES
MONDAY WHICH IS +1 TO +2 STANDARD DEVIATIONS FROM CLIMATOLOGY.
MEANWHILE...09Z SHORT RANGE ENSEMBLES BEGIN TO SHIFT INSTABILITY
AXIS INTO EASTERN NEBRASKA...WHILE SUGGESTING A GOOD CHANCE FOR
40KTS OF EFFECTIVE SHEAR. IF TIMING OF SHORT WAVE IS AS 12Z NAM
SUGGESTS...MONDAY AFTERNOON COULD BE THE NEXT OPPORTUNITY FOR
ORGANIZED SEVERE CONVECTION.
BY TUESDAY...THE BEST SHEAR IS TO OUR SOUTH AND THE MOISTURE PLUME
BEGINS TO SHIFT EAST...THOUGH THE NAM SUGGESTS ONE MORE SHORT WAVE
WILL PASS OVERHEAD. 09Z SHORT RANGE ENSEMBLES DOES PLACE THE
INSTABILITY AXIS OVERHEAD...SO WITH THAT IN MIND INCREASED POPS TO
ALLOW FOR ONE LAST DAY OF SCATTERED CONVECTION.
THE FOUR CORNERS RIDGE IS FORECAST TO AMPLIFY NORTHWARD AND EXPAND
EASTWARD DURING THE MID TO LATE WORK WEEK. THIS TAKES THE MEAN
FLOW TO THE NORTH...DRYING OUT THE REGION WITH TEMPERATURES RISING
ABOVE NORMAL.
BY LATE IN THE WORK WEEK OR NEXT WEEKEND...THE CHANCE RETURNS THAT
THE RIDGE WEAKENS AND ALLOWS NORTHWEST FLOW TO REASSERT
ITSELF...INCREASING THE PROSPECTS FOR SOMEWHAT COOLER AND MORE
ACTIVE WEATHER. GIVEN THE FORECAST RANGE AND THUS LOWER
CONFIDENCE...DID NOT REFLECT THIS IN THE GRIDS AT THIS TIME.
&&
.AVIATION...
FOR TAF SITES KOFK/KOMA/KLNK
18Z TAFS
ISOLATED SHRA WILL CONTINUE TO MOVE EAST...AND NOT AFFECT TAF SITES.
STRATUS DECK SLOWLY ERODING WITH TIME...WITH BKN/OVC DECK AROUND 7K
FEET. AS HIGH PRESSURE MOVES IN TONIGHT...SKIES WILL CLEAR...BUT
ALSO ALLOW FOR FOG DEVELOPMENT DUE TO HIGH MOISTURE CONTENT NEAR THE
SURFACE. HAVE INCLUDED MVFR VSBY IN THE TAFS...AND WILL HAVE TO
MONITOR FOR IFR DEVELOPMENT TOWARDS SUNRISE. HAVE CONDITIONS
IMPROVING AFTER 21/15Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
SHORT TERM/AVIATION...NIPPER
LONG TERM...ROGOWSKI