FXUS63 KOAX 061012
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
412 AM CST SUN MAR 6 2011
.DISCUSSION...
THE 3 WEATHER SYSTEMS TO AFFECT THE FORECAST OVER THE NEXT 4 DAYS
ARE THE PRIMARY CONCERNS ATTM.
A SHRTWV TROF LOCATED OVER SW SD WILL CONT TO TRACK EWD THIS
MRNG...AS WELL AS THE NEXT UPSTREAM SHRTWV NOW OVER WRN MT PER
WV IMAGERY. THIS WILL CONT TO PROVIDE LIFT OVR THE NRN FA THRU
THE MRNG...AND THE ERN CWA DURNG THE EARLY AFTN. RADAR MOSAIC
EARLY THIS MRNG INDCS DECENT RETURNS OVER THE FAR NRN FA...AND
ALTHOUGH MOST OF THIS IS YET TO REACH THE GROUND...MODELS DO INDC
LIFT TO CONT THRU THE MRNG. THUS AT SOME POINT WE EXPECT SATURATION
WILL OCCUR AND -SN WILL GET GOING. WE HAVE LIKELY POPS RUNNING
NEAR THE SD BORDER FOR THIS WITH AMOUNTS LESS THAN AN INCH. MAY
SEE A FEW FLURRIES OR EVEN A LITTLE -SN DROP INTO WRN IA LATE THIS
MRNG AND EARLY THIS AFTN...BUT NO ACCUMULATION IS EXPECTED THERE.
THIS WILL TEND TO QUIET DOWN FOR A TIME LATE THIS AFTN AND INTO
THE OVERNIGHT HOURS. BUT THIS WILL BE SHORT-LIVED WITH THE NEXT
SYSTEM TO AFFECT THE FA IS ALREADY MOVING INTO NRN CA EARLY THIS
MRNG. THIS IS FORECAST TO TRACK THRU THE ROCKIES TONIGHT AND MOV
THRU THE CNTRL PLAINS ON MON WHILE WEAKENING. LIFT WITH THIS
SYSTEM IS A LITTLE MORE FOCUSED FOR OUR AREA...AND THE SYSTEM WILL
HAVE A BETTER THERMAL GRADIENT TO WORK WITH AS WELL. -SN SHLD GET
GOING OVER THE WESTERN HIGH PLAINS THIS EVENING...AND TRACK EWD
OVERNIGHT AND THRU ERN NEB/WRN IA THRU THE DAY ON MON. THE GFS
SEEMS A LITTLE FAST WITH THE SYSTEM AND WENT MORE WITH A SREF/EC
TIMING FOR LIFT. MODELS ARE IN FAIRLY GOOD AGREEMENT THOUGH WITH
THE THERMAL PROFILE AND INDICATE A MOSTLY SNOW EVENT FOR THE
FA...EXCEPT IN THE BOTTOM TWO ROWS OF COUNTIES OF OUR CWA NEAR THE
KS BORDER. ALTHOUGH LIFT IS FAIRLY PERSISTENT...AND MOISTURE ISN'T
TO MUCH OF AN ISSUE...WE TENDED TO TAPER AMOUNTS DURING THE DAY
ON MON. MUCH OF THE -SN WILL BE FALLING DURING THE DAYTIME HOURS
AND WE ARE GETTING INTO LATE WINTER NOW...AND THE SUN ANGLE DOES
HAVE AN EFFECT ON THE DEGREE OF WHICH LIGHT SNOW CAN ACCUMULATE /VERY
HEAVY SNOW CAN OF COURSE OFF-SET THIS/. IN ADDITION...TEMPERATURES
THROUGH THE DAY ON MON SHLD BE RUNNING AROUND OR SLIGHTLY ABOVE 30
WHICH MAKES ACCUMULATION OF -SN ON ROADWAYS DIFFICULT AS WELL
LIMITING IMPACTS. HAVE A GENERAL 1-2 INCHES MOST PLACES WITH 2-3
INCHES IN THE FAR WEST. WITH THE ABOVE REASONING...AS WELL AS THE
EVENT BEING 3RD PERIOD...NO ADVRY APPEARED NECESSARY.
AGAIN THE LIFT WILL GENERALLY WEAKENING DURING THE EVNG MON...BUT
QUICKLY INCREASE TOWARD TUES MRNG OVER THE WRN CWA. THIS IS
ASSOCIATED WITH THE WELL ADVERTISED POTENTIAL WINTER STORM TO
AFFECT THE CWA FOR TUE-TUE NIGHT. MODELS ARE IN PRETTY GOOD
AGREEMENT TONIGHT IN THE TRACK AND TIMING OF THE SYSTEM. THUS
CONFIDENCE IN THE FORECAST IS PRETTY DECENT FOR THIS RANGE. THE
00Z ECMWF BROKE CONTINUITY AND WILL BE DISREGARDED AT THIS
TIME...BUT WILL BE SOMETHING TO KEEP A VERY CLOSE EYE ON TO MAKE
SURE OTHER MODELS DO NOT TREND IN THIS DIRECTION. THUS WILL
FOLLOWING A GENERAL 12Z 05 EC/00Z GFS/00Z UK FOR THE FORECAST /THE
00Z CANADIAN WAS ALSO NOT USED DUE TO IT BEING A SLOW OUTLIER/.
SIG LIFT WILL INCREASE THRU THE DAY ON TUES AS THE MID LVL
CIRCULATION CENTER CLOSES OFF AND MOVS THRU KS. STG DPVA IS INDCD
THRU THE DAY AND INTO TUES NIGHT AS WELL AS STRONG FRONTOGENESIS.
ALTHOUGH WIDESPREAD PRECIP IS EXPECTED DURING THIS
PERIOD...ANALYSIS OF CROSS SECTIONS INDC THE H6 FRONTOGENESIS AREA
MAY BE THE MOST EFFECTIVE AT PRODUCING HEAVY SNOW. THIS IS DUE TO
THE COMBINATION OF GOOD Q-G FORCING IN A WEAKLY STABLE
ATMOSPHERE...BUT ALSO INTERACTS WTIH THE BEST THERMAL PROFILE FOR
GOOD SNOW GROWTH. PRECIP TYPE ISSUES WILL BECOMING AN INCREASING
CONCERN AS WE HEAD THRU TUES AS THE SYSTEM PULLS UP A SIG AMOUNT
OF WARM AIR...AND GIVEN TRAJECTORIES WITHIN THE WARM CONVEYOR
BELT...WE WLD NOT BE SUPRISED TO SEE EVEN WARMER AIR INDICATED IN
LATER RUNS OF THE MODELS. THUS MOST AREAS /EXCEPT VERY NEAR THE
KS/MO BORDER/ SHLD START OFF LATE MON NIGHT AND INTO TUES MRNG
WITH SNOW AS THE PRECIP TYPE...BUT AREAS ALNG AND S OF I-80 AND E
OF HIGHWAY 77 WILL MIX WITH RA BY TUE AFTERNOON...AND THIS IS
EXPECTED TO CONT INTO TUES EVNG BEFORE COLDER AIR PULLS INTO THE
SYSTEM AND SWITCHES PRECIP BACK TO SN. THUS WE WILL HAVE THE
HIGHEST ACCUMULATIONS NEAR THE H6 AXIS WHICH ALSO SHLD SEE THE
PRECIP STAY ALL SNOW. THIS APPEARS TO LINE UP FM ARND DAVID CITY
AND COLUMBUS NORTHEAST TO ONAWA. WE HAVE ELECTED TO ISSUE A WINTER
STORM WATCH AT THIS TIME FOR THIS AREA DESPITE THE EVENT STARTING
LATE IN THE 4TH PERIOD. THIS WAS MAINLY DONE DUE TO THE GOOD
AGREEMENT IN THE MODELS...AND THE POTENTIAL FOR A FAIRLY SIG
EVNT.
AS FOR AMOUNTS...MODEL PRODUCED SNOW ACCUMULATION ARE COMPLETELY
UNREASONABLE AND SHOULD NOT BE USED AT ALL /EXCEPT TO SCARE
PEOPLE/. SNOW RATIOS DURING THE EVENT WILL BE CLOSE TO 10 TO
1...SOME OF THE SNOW WILL FALL DURING DAYLIGHT HOURS...AND
SETTLING WILL ALSO OCCUR GIVEN THE HEAVY WET NATURE OF THE SNOW.
THIS WILL ALL LIMIT SNOWFALL TOTALS. SNOW TOTALS MAY APPROACH 9
INCHES IF A FEW PLACES...BUT WE EXPECTED THIS WILL BE MORE
ISOLATED THAN THE RULE. AS FOR THE METRO AREAS...WE DID NOT
INCLUDE THESE DUE TO THE EXPECTED MIXING WITH RAIN ON TUES/TUES
EVNG LIMITING ACCUMULATIONS. OF COURSE IF THE STORM SYSTEM TAKES A
MORE SOUTHERN TRACK /WHICH WE DO NOT EXPECTED AT THIS TIME/...SNOWFALL
FORECAST WLD INCREASE IN OMA/LNK. FINALLY...THE WINDS WILL
INCREASE ON TUES NIGHT AND MAY LEAD TO SOME BLOWING AND DRIFTING
OF SNOW. THIS WILL BE ESPECIALLY TRUE WHILE THE SNOW IS
FALLING...BUT WE DO NOT EXPECT MUCH BLOWING ONCE THE SNOW ENDS AS
CAA AND LOW LEVEL LAPSE RATES ARE LACKING. WE WOULD BE MORE
IMPRESSED WITH THE WIND POTENTIAL IF THERE WERE MORE OF A NORTHERN
STREAM INFLUENCE TO INCREASE THE PRESSURE GRADIENT BEHIND THE
SYSTEM. IN SHORT...BLIZZARD CONDS ARE NOT EXPECTED. NO OTHER
CHANGES WERE MADE PAST WED DUE TO TIME CONSTRAINTS.
BOUSTEAD
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
VFR CONDITIONS ARE EXPECTED THROUGH THE 06Z TAF CYCLE...THOUGH
CONDITIONS MAY BEGIN TO DEGRADE TO MVFR OR WORSE AT LEAST AT KOFK BY
12Z MONDAY. MID-LEVEL CLOUDS AT OR ABOVE 5000FT WILL MOVE IN THIS
MORNING AND LINGER THROUGH THE CYCLE. WINDS WILL BECOME
SOUTHEASTERLY THIS AFTERNOON AT 10-15KT...THEN DIMINISH IN THE
EVENING AND SWITCH TO NORTHEASTERLY AS A TROUGH MOVES ACROSS THE
SITES.
MAYES
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY
NIGHT FOR NEZ015-018-032>034-044-045-051.
WINTER STORM WATCH FROM LATE MONDAY NIGHT THROUGH LATE TUESDAY
NIGHT FOR NEZ016-017-030-031-042-043-050-065.
IA...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY
NIGHT FOR IAZ043.
&&
$$