FXUS63 KOAX 210919
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
318 AM CST FRI JAN 21 2011
.DISCUSSION...
MAIN FORECAST CONCERNS ARE SNOW CHANCES TODAY...SNOW CHANCES/AMOUNTS
SATURDAY INTO SUNDAY...THEN AGAIN ON MONDAY.
RADAR RETURNS HAVE BEEN INCREASING IN COVERAGE ACROSS MOST OF
NEBRASKA THIS MORNING...AHEAD OF MID LEVEL WAVE DROPPING SOUTHEAST
FROM EASTERN MONTANA. CEILINGS HAVE BEEN GRADUALLY LOWERING AS
SATURATION OF LOW LEVELS CONTINUED...AND REPORTS OF LIGHT SNOW HAVE
BEGUN IN NORTHEAST NEBRASKA. EXPECT WIDESPREAD LIGHT SNOW ACROSS
MOST OF THE CWA...BUT ENHANCED LIFT IN AREA OF WARM ADVECTION AND
ISENTROPIC UPGLIDE IN 280-285K LAYER WILL FOCUS BEST CHANCE FOR
ACCUMULATING SNOWS FROM NORTHEAST NEBRASKA INTO WESTERN IOWA.
AMOUNTS SHOULD REMAIN NEAR OR UNDER AN INCH FOR MOST AREAS USING
GARCIA METHOD TECHNIQUES WITH THIS FAST-MOVING CLIPPER SYSTEM.
EXPECT SNOWS TO END FOR THE MOST PART BY MID AFTERNOON...BUT
FLURRIES OR VERY LIGHT SNOW COULD CONTINUE UNTIL SUNSET.
TEMPERATURES TODAY WILL BE HELD IN CHECK BY CLOUDS/PRECIP IN THE
EAST...BUT SOME MIXING OF LOW LEVEL AIR IN THE WEST IN THE AFTERNOON
WILL PUSH HIGHS TO OR ABOVE 20.
BREAKS IN THE CLOUD COVER AND LIGHT WINDS TONIGHT SHOULD ALLOW FOR A
COLD START TO SATURDAY. HAVE LOWS IN THE SINGLE DIGITS IN MOST
AREAS...BUT COULD SEE COLDER LOWS IN OUR EAST WHERE SOME NEW SNOW
COVER SHOULD EXIST.
CLOUDS AGAIN INCREASE SATURDAY AS OUR NEXT SYSTEM APPROACHES FROM
THE NORTHWEST. MODELS HAVE GOTTEN QUICKER WITH THIS SYSTEM OVER THE
LAST SEVERAL RUNS...AND DECENT TIMING CONSISTENCY NOW EXISTS. GFS
AND ECMWF ARE IN AGREEMENT IN BREAKING OUT SNOW IN NORTHEAST
NEBRASKA SHORTLY AFTER NOON SATURDAY...THEN SPREADING THAT SNOW
SOUTHEAST THROUGH SUNDAY. EXACT TRACK OF HEAVIEST SNOWFALL IS STILL
IN QUESTION...BUT MOST LIKELY AXIS WILL FALL JUST WEST OF THE OMAHA
METRO IN ZONE OF STRONGEST FRONTOGENETICAL FORCING IN 700-750MB
LAYER AND LEFT OF 850MB LOW TRACK AS PER GFS FORECAST. GARCIA
CALCULATIONS SUGGEST 4 TO 6 INCHES OF SNOW IS POSSIBLE FOR A 12- TO
18-HOUR EVENT...AND AVERAGE MODEL QPF PROGS PAINT UP TO 0.40" OF
LIQUID WHICH EQUATES TO 6 INCHES OF SNOW AT A 15 TO 1 RATIO. AM
FAIRLY CONFIDENT ON SNOW FALLING SATURDAY AFTERNOON/NIGHT...BUT
EXPECT AMOUNTS TO MOSTLY BE UNDER 6 INCHES. THUS NO WINTER STORM
WATCH WILL BE ISSUED NOW.
SNOW WILL BE EXITING THE SOUTHEAST CWA SUNDAY AFTERNOON...THEN YET
ANOTHER UPPER WAVE WILL BE DROPPING SOUTH INTO THE MISSOURI RIVER
VALLEY SUNDAY NIGHT. AGAIN GFS AND ECMWF ARE SIMILAR IN SHOWING THIS
FEATURE...BUT THE GFS IS STRONGER AND PRODUCES A DECENT AMOUNT OF
QPF OF A TENTH OR TWO OF LIQUID FROM LATE SUNDAY NIGHT THROUGH
MONDAY. FOR NOW WILL JUST INCREASE POPS SUNDAY NIGHT AND MONDAY.
TEMPERATURES OVER THE WEEKEND SHOULD HOLD IN THE TEENS AND 20S FOR
HIGHS WITH CLOUDS AND SNOW DOMINATING THE FORECAST. THEN CAN NOT SEE
MUCH OF A WARMING TREND THROUGH THE WEEK AS MEAN TROUGH REMAINS OVER
THE MIDDLE OF THE COUNTRY WITH SEVERAL IMPULSES REINFORCING COLD
TEMPERATURES IN OUR PART OF THE WORLD. NO CHANGES WERE MADE TO
FORECAST BEYOND MONDAY.
DERGAN
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
WEAK SHORT WAVE ENERGY WILL MOVE THROUGH THE REGION DURING THE
PERIOD WITH MVFR AND IFR CONDITIONS DEVELOPING AS LIGHT SNOW SPREADS
INTO THE AREA AFTER 12Z. SNOW SHOULD END BY 00Z BUT MVFR CIGS
EXPECTED TO LINGER THROUGH THE REMAINDER OF THE FORECAST PERIOD.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$