FXUS63 KOAX 190918
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
418 AM CDT TUE APR 19 2011
.DISCUSSION...
FORECAST CONCERNS IN THE SHORT TERM ARE THUNDERSTORMS OVER
SOUTHEAST NEBRASKA INTO SOUTHWEST IOWA AND POTENTIAL FOR SNOW IN
NORTHEAST NEBRASKA THIS MORNING...THEN IMPROVING CONDITIONS FOR
LATER TODAY.
THE LATEST SURFACE ANALYSIS AT 08Z HAD SURFACE LOW PRESSURE NEAR
THE KANSAS/OKLAHOMA BORDER WITH THE STATIONARY FRONT JUST SOUTH OF
EMPORIA. 00Z SOUNDINGS SHOWED DEEP MOISTURE IN PLACE AT KTOP WITH
A 12 DEG C H85 DEWPOINT. THE H850 ZERO DEGREE LINE EXTENDED FROM
NORTH OF KLBF INTO NORTHEAST NEBRASKA...WITH THE +12 DEG C TEMP AT
KTOP. STRONG THETA-E ADVECTION WAS UNDERWAY. WATER VAPOR SATELLITE
IMAGEY SHOWED A TROF OVER THE ROCKIES MOVING INTO THE PLAINS.
THUNDERSTORMS STARTED TO INCREASE IN COVERAGE OVER SOUTHWEST
NEBRASKA AROUND MIDNIGHT AND WERE DEVELOPING AHEAD OF THE
MID TROPOSPHERIC TROUGH AND ALONG WITH THE STRENGTHENING H85 JET
AND DEEPER MOISTURE INTO SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. IN
ADDITION...THERE IS SUPPORT WITH STEEP MID LEVEL LAPSE RATES AND
THE RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET.
MEANWHILE...COOLER AIR IS SLOWING MAKING IT INTO THE NORTHERN PART
OF THE CWA. IT HAS BEEN SNOW AT ONEILL...AND THE TEMP IS DOWN TO
32 AT YANKTON. DISPATCH AT KNOX COUNTY MENTIONED A COUPLE INCHES
OF SNOW EARLIER THIS MORNING NEAR BLOOMFIELD. ANTELOPE COUNTY
REPORTED MIST AND 33 DEGREES ANT KOFK/KLCG HAS RAIN AND 36.
THE NAM/4KM WRF/HRRR/GFS DO A GOOD JOB OF SHIFTING THE
PRECIPITATION FROM NORTH CENTRAL NEBRASKA...TO MORE OF A CENTRAL
TO NORTHEAST-ECENTRAL NEBRASKA AREA BY 12Z. THE CONVECTION OVER
SOUTHEAST NEBRASKA MOVES NORTH AND SHIFTS INTO WESTERN IOWA.
IT WILL BE A TRICKY FORECAST IN NORTHEAST NEBRASKA AS TO HOW MUCH
SNOW WILL FALL AS TEMPERATURES ARE MARGINAL AND ARE EXPECTED TO
ONLY DROP A DEGREE OR TWO WITH GRADUALLY DEEPENING COLD AIR. IN
ADDITION...BEST LIFT AND FRONTOGENESIS IS 09-12Z...DECREASING
THROUGH 18Z. WILL LEAVE WINTER WEATHER ADVISORY IN PLACE. SOME 3
TO 5 INCHES AMOUNTS WILL BE POSSIBLE FOR PARTS OF NORTHEAST
NEBRASKA IN THE ADVISORY AREA BEFORE THE SNOW ENDS. A MIX...WITH
OTHER LIGHT ACCUMULATIONS WILL BE POSSIBLE FARTHER SOUTH FROM
NELIGH TO PENDER. THUNDERSTORMS WILL MOVE ACROSS
SOUTHEAST/ECENTRAL NEBRASKA AND SOUTHWEST IOWA THIS MORNING AND
SHOULD BE MOSTLY OUT OF SOUTHWEST IOWA BY 1PM. MODERATE RAIN CAN
BE EXPECTED IN BETWEEN THE SNOW AND TSRA WITH SOME HALF TO ONE
INCH RAIN AMOUNTS BEFORE 1PM. TEMPERATURES ARE NOT GOING TO CHANGE
MUCH TODAY WITH HIGHS IN THE UPPER 30S TO MID 40S.
HIGH PRESSURE WILL BUILD IN FOR WEDNESDAY WITH THE NEXT SHORTWAVE
TROUGH AFFECTING THE FORECAST AREA WEDNESDAY NIGHT AND THURSDAY.
SHOWERS AND THUNDERSTORMS WILL ONCE AGAIN MOVE ACROSS THE REGION
WITH STRONG H85 FLOW AND MOISTURE RETURN. TEMPERATURES WILL REMAIN
IN THE 40S AND 50S FOR WEDNESDAY AND THURSDAY.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
CIGS WILL BECOME IFR AT ALL EASTERN NEBRASKA TAF SITES BEFORE 11Z AS
-SHRA ENVELOPE THE AREA. MVFR VSBYS WILL DROP TO IFR AS WELL WITH
-SHRA AND BR THE PREDOMINANT OBSTRUCTIONS. KOFK WILL SEE A CHANGE
FROM -SHRA TO -RASN BETWEEN 09Z AND 12Z...AND COULD SEE ALL -SN
BEFORE PRECIPITATION ENDS BY 17Z. IF -SN OCCURS...VSBYS BELOW 1SM
WILL BE POSSIBLE WITH CIGS BELOW FL005. -SHRA IS EXPECTED TO END AT
KOMA AND KLNK BY 18Z...BUT IFR CIGS WILL ONLY GRADUALLY IMPROVE TO
MVFR BY 00Z. EXPECT CIGS BETWEEN FL010 AND FL020 THROUGH WEDNESDAY
MORNING.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY UNTIL NOON CDT TODAY FOR NEZ011-012-
016>018.
IA...NONE.
&&
$$
ZAPOTOCNY/DERGAN