FXUS63 KOAX 192105
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
305 PM CST SAT FEB 19 2011
.SHORT TERM...TONIGHT THROUGH TUESDAY.
MAIN FORECAST CHALLENGE WILL BE DEALING WITH THE TIMING OF THE
COLDER AIR MOVING INTO THE AREA TONIGHT AND SUNDAY AND IMPACT ON
AMOUNT OF FREEZING RAIN IN THE NORTH.
SHARP CONTRAST IN CONDITIONS ACROSS THE PLAINS REGION AT 20Z WITH
ARCTIC AIR IN PLACE OVER THE NORTHERN PLAINS WHILE WARM MOIST AIR
MASS WAS OVER THE SOUTHERN PLAINS...LEADING TO POTENTIAL FOR SOME
SIGNIFICANT WINTER WEATHER IN THE SHORT TERM.
SOME SHOWERS WERE ALREADY SHOWING UP ON RADAR ACROSS CENTRAL
MISSOURI. INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS
DEVELOPING AND SPREADING NORTH TONIGHT AS LOW PRESSURE DEVELOPS
OVER EASTERN COLORADO AND STEEP MID LEVEL LAPSE RATES MOVE INTO
THE REGION LATE TONIGHT. MOST OF THE CWA IS EXPECTED TO REMAIN IN
THE WARM AIR WING OF SYSTEM COMING OUT OF COLORADO...EXCEPT FOR
THE FAR NORTHWEST COUNTIES WHERE SURFACE TEMPERATURES ARE EXPECTED
TO FALL INTO THE LOWER 30S. POTENTIAL FOR SOME SIGNIFICANT ICING
WILL EXIST THERE AS FREEZING RAIN BECOMES MORE LIKELY LATE TONIGHT
INTO SUNDAY MORNING AS THE COLD AIR BEGINS TO UNDERCUT THE WARM
AIR ALOFT.
WILL ISSUE HEADLINES FOR ICE STORM WARNING FOR THE FAR NORTHWEST
COUNTIES LATE TONIGHT THROUGH SUNDAY MORNING. PLENTY OF MOISTURE
AND INSTABILITY AVAILABLE FOR SOME SIGNIFICANT PRECIP ACROSS THE
AREA TONIGHT. ICING OF A QUARTER INCH OR BETTER...ESPECIALLY NEAR
THE SOUTH DAKOTA BORDER IS LIKELY. RAINFALL UP TO AN INCH ACROSS THE
REST OF THE AREA WILL ALSO COMPOUND ANY ICE JAM FLOODING CURRENTLY
TAKING PLACE ON RIVERS.
COLDER AIR OVERSPREADS THE AREA SUNDAY AFTERNOON AS SURFACE SYSTEM
TRACKS RAPIDLY EAST WITH SOME LIGHT SNOW OR FLURRIES EXTENDING
INTO SUNDAY NIGHT IN THE NORTH...UP TO AN INCH OF SNOW POSSIBLE NEAR
THE SOUTH DAKOTA BORDER ALONG WITH GUSTY NORTHWEST WINDS. COLD AIR
IN PLACE FOR MONDAY BUT WARMER TEMPERATURES RETURN TUESDAY AS HIGH
MOVES EAST AND SOUTH FLOW RETURNS.
.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY.
IT APPEARS THE SOMEWHAT COOLER PATTERN WE WILL SEE EARLY NEXT WEEK
WILL REMAIN IN PLACE THROUGH SATURDAY. WHILE UPPER FLOW REMAINS
MAINLY FROM THE SOUTHWEST...COLDER SURFACE AIR SLIPPING UNDER THAT
FLOW EARLY IN THE WEEK WILL HAVE A HARD TIME RETREATING BACK NORTH.
AND A COUPLE OF POTENTIAL IMPULSES ROLLING THROUGH THE PLAINS WILL
HELP TO KEEP OUR AREA ON THE COLD SIDE OF A FRONTAL SYSTEM STALLING
IN THE SOUTHERN PLAINS.
GFS AND ECMWF MODELS BOTH SHOW SOUTHWEST UPPER FLOW PATTER THROUGH
THE END OF THE WEEK...BUT ECMWF ADVERTISES SOME MINOR RIDGING
STARTING TO TAKE SHAPE NEXT WEEKEND. THE GFS DELAYS THIS PATTERN A
COUPLE OF DAYS. AND BOTH MODELS EJECT A SHORTWAVE THROUGH THE PLAINS
DURING THE WEEK...BUT TIMING IS OFF BY AT LEAST 24 HOURS.
HAVE FOLLOWED THE ECMWF FOR THE MOST PART...BUT DID ALLOW SOME
LEEWAY TOWARD THE GFS SOLUTION. ECMWF SHOWS SHORTWAVE MOVING INTO
THE PLAINS WEDNESDAY NIGHT...INDUCING SURFACE LOW IN WESTERN KANSAS.
WARM AND MOIST FLOW AHEAD OF THIS LOW WILL BRING CHANCE FOR ELEVATED
SHOWERS TO AT LEAST SOUTHEAST NEBRASKA WEDNESDAY NIGHT...BUT WE ARE
MORE LIKELY TO SEE PRECIPITATION THURSDAY ACROSS MUCH OF EASTERN
NEBRASKA AND SOUTHWEST IOWA. TEMPERATURE PROFILES SUGGEST OUR SOUTH
WILL SEE MAINLY RAIN THROUGH THURSDAY...WITH A MIX OR SNOW TO THE
NORTH. SURFACE LOW EXITS RAPIDLY TO THE EAST THURSDAY NIGHT...SO AM
APT TO SHUT OFF PRECIP THEN. HOWEVER...GFS EJECTS A SHORTWAVE
THROUGH OUR AREA THEN...AND SPREADS SIGNIFICANT SNOWS ACROSS SOUTH
DAKOTA INTO NORTHERN NEBRASKA. SO HAVE MAINTAINED A SMALL CHANCE FOR
SNOW FOR MUCH OF OUR AREA THROUGH FRIDAY FOR THIS SCENARIO. BOTH
MODELS SHOW NORTHERLY LOW LEVEL FLOW WEDNESDAY NIGHT THROUGH
FRIDAY...SO AM FAIRLY CONFIDENT TEMPERATURES WILL FALL BACK TO OR
BELOW NORMAL FOR ALL OF THE WEEK.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
CLEAR SKIES OVER EASTERN NEBRASKA TAF SITES WILL QUICKLY GIVE WAY TO
AT LEAST MVFR CIGS AS BAND OF FL025 STRATUS LIFTS NORTH FROM EASTERN
KANSAS AND SOUTHEAST NEBRASKA. EXPECT MVFR CIGS IN KLNK AND KOMA
BEFORE 00Z...THEN CIGS SHOULD CONTINUE A GRADUAL LOWERING AS A WARM
FRONT LIFTS NORTH TOWARD THE AREA. KOFK SHOULD SEE MVFR CIGS BEFORE
02Z. AS LOW LEVEL JET STREAM INCREASES DURING THE LATE EVENING...
RELATIVELY WARM AND MOIST AIR WILL BE LIFTED OVER THE WARM FRONT
WHICH WILL LEAD TO SHOWERS AND POSSIBLY THUNDERSTORMS AT ALL TAF
SITES. SATURATION OF LOW LEVEL AIR FROM PRECIPITATION WILL DRIVE
CIGS AND VSBYS LOWER...WITH OCCASIONAL IFR IF NOT LIFR CONDITIONS
AFTER 06Z. AS WARM FRONT LIFTS NORTH OF KLNK/KOMA AFTER 14Z
SUNDAY...SOME IMPROVEMENT IN CIGS/VSBYS IS LIKELY...BUT VFR
CONDITIONS ARE NOT EXPECTED. A TURN TO NORTHERLY LOW LEVEL FLOW AND
THE CHANCE FOR SNOW WILL AFFECT KOFK NEAR 18Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...ICE STORM WARNING FROM MIDNIGHT TONIGHT TO NOON CST SUNDAY FOR
NEZ011-012-016-017.
IA...NONE.
&&
$$
FOBERT/DERGAN