FXUS63 KOAX 302107
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
307 PM CST THU DEC 30 2010
.SHORT TERM...TONIGHT THROUGH SUNDAY.
WINTER WEATHER THROUGH FRIDAY CONTINUES TO BE THE MAIN FORECAST
CONCERN.
COLD FRONT HAS BEGUN ITS PUSH THROUGH THE CWA THIS AFTERNOON...
MOVING THROUGH OMAHA AS OF 230 PM. 2 PM TEMPERATURES RANGED FROM 67
IN FALLS CITY UNDER SUNSHINE AND GUSTY SOUTHWEST WINDS TO 23 IN
ALBION WHERE CLOUDS...FREEZING DRIZZLE AND GUSTY NORTHWEST WINDS
WERE NOTED. TEMPS IN THE TEENS WERE IMPLIED IN OUR FAR NORTHWEST.
COLD FRONT WAS MAKING A STEADY PUSH EAST...AND WAS CLEARLY
DELINEATED BY STRATUS MARCHING THROUGH EASTERN NEBRASKA. CURRENT
MOVEMENT SUGGESTS TEMPS WILL DROP BELOW FREEZING FOR ALL OF OUR CWA
BY 9 PM THIS EVENING.
INITIAL SURFACE LOW WAS MOVING NORTH THROUGH NORTHWEST IOWA...
HELPING TO PUSH ARCTIC AIR THROUGH OUR AREA IN ITS WAKE. LITTLE
PRECIPITATION IN OUR CWA WITH THIS LOW THIS AFTERNOON AS MAIN PRECIP
SHIELD ROTATED THROUGH NORTH CENTRAL NEBRASKA. HOWEVER FREEZING
DRIZZLE WAS NOTED IN THICK STRATUS LAGGING FRONT BY A FEW COUNTIES.
STRONG SOUTH AND WEST WINDS NEAR 850MB WAS PROVIDING WARM ADVECTION
LIFT OVER COLD SURFACE AIR...SO AT LEAST PATCHY FREEZING DRIZZLE IS
EXPECTED TO CONTINUE THROUGH THE EVENING...AND WILL LIKELY SPREAD
SOUTHEAST TOWARD THE INTERSTATE 80 CORRIDOR BY MIDNIGHT.
BY THAT TIME...OUR SECOND AND MORE POWERFUL LOW PRESSURE AREA WILL
BE PUSHING INTO SOUTHWEST KANSAS WITH AN EVENTUAL TRACK INTO
NORTHERN MISSOURI AND CENTRAL IOWA FRIDAY AFTERNOON. ATTENDANT UPPER
LOW IS PROGGED TO ROLL THROUGH CENTRAL NEBRASKA...WITH TRACK OF
850MB LOW THROUGH EASTERN NEBRASKA. WARM ADVECTION WITH THIS FEATURE
WILL BE MAXIMIZED IN THE 12Z-15Z TIME FRAME...AND THAT IS WHEN
GREATEST PRECIPITATION POTENTIAL EXISTS. WHILE MODELS HAVE BEEN
DIVERGING ON PLACEMENT OF HIGHEST QPF OVER THE LAST SEVERAL DAYS...
THEY HAVE CONVERGED ON FRIDAY MORNING AS BEING TIME OF MAXIMUM
POTENTIAL AS WARM ADVECTION WING SWINGS THROUGH EASTERN NEBRASKA AND
WESTERN IOWA. LIFT ASSOCIATED WITH UPPER LOW AND 850 WARM ADVECTION
WILL BEGIN IN OUR WESTERN CWA NEARER MIDNIGHT BEFORE SPREADING
ACROSS MOST OF THE CWA BY 12Z.
PRECIPITATION TYPE IS STILL IN QUESTION WITH SHALLOW COLD AIR AT THE
SURFACE AND WARM NOSE LIFTING NORTH AND NORTHWEST THROUGH THE CWA.
CROSS SECTIONS OF TEMPERATURES FROM BOTH GFS AND NAM ARE SIMILAR IN
DEPTH AND EXTENT OF WARM NOSE...SO WERE FOLLOWED CLOSELY WHEN
DETERMINING PRECIP TYPE AND TIMING OF PHASE CHANGES. ASIDE FROM
FREEZING DRIZZLE IN STRATUS LAYER THIS EVENING...EXPECT AN ALL SNOW
EVENT FOR MOST OF THE NORTHWEST CWA...GENERALLY NEAR AND NORTHWEST
OF AN ALBION TO NORFOLK TO WAYNE LINE. HIGHER QPF IS EXPECTED HERE
AS WELL...AND A CONSERVATIVE 15 TO 1 SNOW/WATER RATIO YIELDS 5 TO 8
INCHES FROM SOUTHEAST TO NORTHWEST. GARCIA CALCULATIONS ALSO SUGGEST
THIS TOTAL FROM MIDNIGHT THROUGH FRIDAY AFTERNOON. AMOUNTS WILL
TRAIL OFF QUICKLY AS WE HEAD SOUTHEAST WITH SLEET THE MAIN PRECIP
TYPE INITIALLY JUST NORTH AND WEST OF THE OMAHA METRO. AGAIN TOTALS
COULD GO UP OR DOWN DEPENDING ON SLEET DURATION...BUT AMOUNTS FROM 2
TO 4 INCHES OF SNOW/SLEET LOOK LIKELY. AROUND THE INTERSTATE 80
CORRIDOR...PRECIP WILL LIKELY BEGIN AS FREEZING RAIN THEN QUICKLY
TURN TO SLEET. COULD SEE A FEW HUNDREDTHS OF ICE BEFORE THE CHANGE
JUST AFTER DAYBREAK FRIDAY. THEN EXPECT A SEVERAL HOUR PERIOD WHEN
SLEET IS THE MAIN PRECIP TYPE BEFORE CHANGING TO SNOW BY LATE FRIDAY
MORNING. THIS COMBINATION OF FREEZING RAIN THEN 1 TO 2 INCHES OF
SLEET/SNOW SUGGESTS WINTER WEATHER ADVISORY IS NEEDED. AND TO THE
SOUTHEAST...FREEZING RAIN SHOULD BE THE PRIMARY PRECIP TYPE GIVE
SHALLOW COLD AIR LINGERING THERE. HAVE PAINTED A SWATH OF A TENTH OR
SO OF ICE ACCUMULATION IN FAR SOUTHWEST IOWA AND SOUTHEAST NEBRASKA.
A CAVEAT FOR ICE AMOUNTS IN OUR SOUTHEAST IS THE POTENTIAL FOR
CONVECTIVELY ENHANCE PRECIP AMOUNTS. MODELS SHOW A LAYER OF ELEVATED
INSTABILITY ROTATING NORTH THROUGH EASTERN KANSAS UNDER STEEP LAPSE
RATES ALOFT. SPC HAS PAINTED THUNDER UP TO OUR SOUTHEAST NEBRASKA
BORDER...SO THERE IS A POTENTIAL FOR MUCH MORE PRECIP IN SOUTHEAST
NEBRASKA AND SOUTHWEST IOWA. WILL HAVE TO WATCH THIS AS THE EVENING
PROGRESSES AND MAKE ADJUSTMENTS AS NECESSARY.
PRECIPITATION WILL LIFT QUICKLY TO THE NORTH FRIDAY AFTERNOON.
LATEST NAM SHOWS LINGERING TROWAL PATTERN IN NORTH CENTRAL AND
NORTHEAST NEBRASKA FRIDAY NIGHT...SO HAVE MAINTAINED POPS PAST 00Z.
OTHERWISE EXPECT DECREASING CLOUDS FOR THE WEEKEND AS UPPER SYSTEM
PULLS OFF TO THE NORTHEAST.
TEMPERATURES WILL TRY TO REBOUND SATURDAY AND SUNDAY...BUT AMOUNT OF
SNOW COVER AND ARCTIC AIRMASS WILL MAKE THAT DIFFICULT. SHOULD SEE
TEMPERATURES BELOW ZERO IN OUR NORTHWEST ON SATURDAY AND SUNDAY
MORNINGS GIVEN EXPECTED SNOW COVER. WESTERLY WINDS AND SUNSHINE
SATURDAY AFTERNOON WILL BEGIN TO SCOUR OUT COLD SURFACE AIR...BUT
HIGHS THEN WILL ONLY REACH THE TEENS. HIGHS SUNDAY COULD REACH THE
20S WITH SOUTHWEST LOW LEVEL FLOW.
DERGAN
.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY.
NO MAJOR STORM SYSTEMS ARE IN THE HORIZON AND TEMPERATURES ARE THE
ONLY FORECAST CHALLENGE IN THE EXTENDED PERIOD. A WEAK UPPER
SHORTWAVE TROF WL SLIDE TO OUR NORTHEAST ON MONDAY NIGHT INTO
TUESDAY WHICH COULD DRAG DOWN SLIGHTLY COOLER TEMPERATURES.
OTHERWISE WEAK NORTHWEST FLOW ALOFT WL REMAIN OVER THE AREA THRU THE
PD WITH TEMPERATURES REMAINING NEAR NORMAL FOR THIS TIME OF THE YEAR.
KERN
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
COLD FRONT PUSHING THROUGH EASTERN NEBRASKA AT 18Z WITH MVFR CIGS
MOVING INTO KLNK AND KOMA 20Z-22Z. MAIN UNCERTAINTY WILL BE TIMING
OF PRECIP AND TYPE. KOFK CURRENTLY REPORTING ZR- AND AS COLD AIR
DEEPENS EXPECT TO CHANGE TO SNOW BY 21Z...SOME BREAK EXPECTED FOR A
TIME TONIGHT BEFORE NEXT WAVE MOVES INTO THE AREA. KLNK AND KOMA
MAY SEE SOME ZL- OVERNIGHT WITH MORE GENERAL PERIOD OF ZR/SNOW AFTER
12Z.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST FRIDAY
FOR NEZ045-052-053-066>068-078-088>093.
WINTER WEATHER ADVISORY UNTIL 6 PM CST FRIDAY FOR NEZ015-032>034-
042>044-050-051-065.
WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR NEZ011-012-
016>018-030-031.
IA...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST FRIDAY
FOR IAZ055-056-069-079-080-090-091.
WINTER WEATHER ADVISORY UNTIL 6 PM CST FRIDAY FOR IAZ043.
&&
$$