FXUS63 KOAX 222054
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
253 PM CST SAT JAN 22 2011
.REST OF THIS AFTERNOON THROUGH TONIGHT...
SNOW IS OVERSPREADING THE AREA RAPIDLY IN THE MID-AFTERNOON HOURS AS
SYSTEM APPROACHES. 20Z WV IMAGERY AND RUC 1.5 PVU PRESSURE ANALYSIS
INDICATE UPPER TROUGHING DIVING OUT OF THE NRN ROCKIES INTO THE HIGH
PLAINS THIS AFTERNOON. BROAD 850MB WARM SECTOR WAS POKING INTO SRN
NEB AS WARM AIR ADVECTION CONTINUES INTO ERN NEB...WITH TEMPS RISING
INTO THE 30S IN THE SRN CWA AND RUC/NAM 850MB TEMPS REACHING 0-2C
THIS AFTERNOON. PRECIP TYPE INITIALLY IN SOUTH CENTRAL NEB INTO THE
SRN CWA HAS BEEN OCCURRING AS A BRIEF PERIOD OF RAIN BEFORE CHANGING
OVER TO SNOW.
MAIN FORECAST CONCERN IS IN HOW MUCH SNOW WILL OCCUR ACROSS THE
AREA...AS PROBABLY OF SNOW OCCURRENCE IS 100 PCT. WITH COLD/DRY AIR
PUSHING SOUTH OUT OF MN/SD...AND WARM/MOIST AIR NUDGING
NORTHWARD...FRONTOGENESIS WILL BE INCREASING IN THE MIDDLE CWA
THROUGH THE AFTN/EVNG. THIS WILL AID SNOW ACCUMULATIONS...IN
ADDITION TO SUPPORTIVE SYNOPTIC ENVIRONMENT OF INCREASING Q-VECTOR
CONVERGENCE AND POSITIVE PV ADVECTION. SYSTEM HAS A DECENT MOISTURE
FEED...WITH MODEL QPF RANGING FROM 0.3 TO 0.6-ISH IN HIGHEST AREAS.
EXPECT ACCUMULATIONS TO RANGE FROM AROUND 2 INCHES IN THE SWRN CWA
/COULD BE LESS IF RAIN HOLDS ON LONGER THAN EXPECTED THIS EVENING/
TO A PEAK NEAR 6 INCHES IN AT LEAST A FEW LOCATIONS IN THE CENTRAL
CWA. DID NOT FEEL CONFIDENT ENOUGH ABOUT WIDESPREAD AMOUNTS OF 6+
INCHES TO ISSUE A WARNING...BUT THINK A FEW LOCATIONS MAY REACH
ACCUMULATIONS AROUND THAT HIGH. POTENTIAL FOR HIGHEST ACCUMULATIONS
LOOKS LIKE IT WILL CENTER ON A CORRIDOR FROM AROUND KNOX CO THROUGH
NORFOLK TOWARD OMAHA AND TO AROUND RED OAK. WIND WILL BE A CONCERN
WITH THIS SYSTEM AS NERLY WINDS INCREASE TO AROUND 15KT...CREATING
AT LEAST MINOR BLOWING AND DRIFTING SNOW THAT MAY NOT BE BLOCKED
WELL BY SNOW FENCES/PROTECTION GIVEN THE EASTERLY WIND COMPONENT.
SNOW WILL TAPER FROM NORTH TO SOUTH BETWEEN 06-12Z...WITH SNOW
LIKELY LINGERING JUST PAST 12Z IN THE SOUTHERNMOST CWA. HAVE
UPDATED ADVISORY TO START AT 21Z WITH SNOW ALREADY STARTING ACROSS
THE AREA. ALSO...DECREASED MIN TEMPS IN THE NRN CWA OVERNIGHT WITH
STRONG COLD AIR ADVECTION COMBINING WITH DECREASING CLOUDS AND WINDS
OVERNIGHT.
MAYES
.SHORT TERM...SUNDAY THROUGH TUESDAY.
MODELS CONTINUING TO ADVERTISE SERIES OF VORT MAX RIDING DOWN UPPER
RIDGE ESTABLISHED OVER THE WRN CONUS. FORTUNATELY THE THREAT FOR
SNOW IS NOT LOOKING AS GOOD AS COMPARED TO THE LAST SEVERAL WAVE
CROSSING THE REGION. HAVE ADJUSTED SUNDAY MORNING POPS DOWN JUST A
BIT RELATED TO EXITING SHORTWAVE. NAM/GFS/ECM ALL INDICATING
SUBSIDENCE WILL QUICKLY FILL IN OVER THE CWA THRU 12Z. HOWEVER WILL
KEEP TOKEN POPS IN PLACE IN CASE OF LINGERING LIGHT SNOW. SUNDAY
NIGHT THE NEXT SHORTWAVE RUSHES DOWN THE NRN PLAINS AND INDUCES
MODEST SYNOPTIC SCALE LIFT OVER THE DAKOTAS/MN/NEB/IA. THE SFC
REFLECT THOUGH IS PROGGED TO OCCUPY THE UPPER MID WEST WITH BULK OF
AVAILABLE MOISTURE. 300-500MB QVEC SUGGESTING LIFT VIS DPVA WILL BE
MORE PREVALENT THOUGH MAINLY OVER WRN/CNTRL NEB AND WRN HALF OF KS.
BECAUSE THERE IS LIFT ON THE WHOLE...WILL GEAR SUNDAY NIGHT POPS A
BIT HIGHER OVER THE NRN CWA WHERE MOISTURE WILL BE MORE ATTAINABLE...
WITH DECREASING POPS HEADING SW. ON MONDAY ATTENDANT COLD FRONT
PUSHES INTO THE CNTRL PLAINS. APPEARS THAT BEST AGEOSTROPHIC FORCING
WILL EXIT AREA BY AFTERNOON...SO WILL FOCUS SMALL POPS DURING THE
MORNING HOURS. THEN AGAIN ON TUESDAY ANOTHER PAC NW SHORTWAVE
APPROACHES THE PLAINS. BECAUSE MOIST PROGS ARE SOMEWHAT WEAK PREFER
TO GO WITH DRY FCST. AS FOR TEMPS...SHOULD BE SOME RECOVERY MONDAY
AND TUESDAY PROVIDED BY A WARM FRONT CROSSING THRU THE REGION.
DEE
.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY.
THE LARGE SCALE PATTERN OF WRN RIDGE AND ERN TROF IS EXPECTED TO
CONT THRU THE EXTENDED PERIOD. THE MAIN STORY THOUGH DURING THIS
TIME RANGE WILL BE A WARMING IN THE TEMPERATURES DURING THE THU/FRI
TIME FRAME AS THE WRN US RIDGE...FOR A SHORT TIME...WILL AMPLIFY TO
THE E. UNTIL THEN...A COUPLE OF WEAK SHRTWV TROFS WILL AFFECT THE
AREA ON WED INTO THURS. FORCING WITH THESE SYSTEMS CONTD TO LOOK
WEAK TODAY AND THUS WL MAINTAIN A DRY FORECAST...BUT LATER SHIFTS WL
HAVE TO MONITOR FOR SOME LIGHT PRECIP. A WARM FRNT THEN PUSHES THRU
THE AREA ON THU LEADING A NICE WARMING TREND THRU FRI. HAVE
WARMED/HIGHS LOWS MOST LOCATIONS AND ESPECIALLY IN THE WRN AND SW
FA. OF COURSE THE DEGREE OF WARMING WL DEPEND AT LEAST IN PART ON
THE SNOW COVER...BUT THE DEGREE OF PACIFIC AIR INVADING THE AREA
DURING THE TIME PERIOD LEADED TO WARMING OF THE TEMPERATURES. MODELS
THEN AGREE...FOR THE MOST PART...IN A STG CDFNT TO MOV THRU THE AREA
ON FRI NIGHT WITH MUCH COLDER AIR SPILLING INTO THE REGION ON SAT.
ATTM IT LOOKS AT THOUGH THE BULK OF FORCING AND THUS PRECIP WITH THE
FRI NIGHT FNT WL BE TO THE EAST AND THUS WE WILL HAVE A DRY
FORECAST.
JB
&&
.AVIATION...
18Z TAFS
DETERIORATING CONDITIONS ARE EXPECTED AT ALL TAF SITES THIS
AFTN/EVNG AS SNOW OVERSPREADS THE AREA. SNOW WILL LAST AROUND 12-15
HOURS AT ALL SITES...WITH MODERATE SNOW RATES FOR AROUND 6-8 HOURS
FROM LATE AFTERNOON/EARLY EVENING ONWARD. VIS COULD REACH 1/2SM OR
LESS IN THE HEAVIEST SNOW...WHICH COULD OCCUR INTERMITTENTLY FOR
AROUND 4 HOURS. ALSO...CIGS WILL DROP TO IFR OR LIFR RANGE THROUGH
MUCH OF THE EVENT. NORTHEASTERLY WINDS WILL INCREASE THIS
EVENING...PEAKING DURING THE SNOW AND THEN DIMINISHING TOWARD
DAYBREAK...WHICH COULD CREATE BLOWING SNOW AT TAF SITES /THOUGH THIS
WAS NOT INCLUDED IN THE 18Z TAF CYCLE/. CIGS AND VIS WILL IMPROVE
OVERNIGHT AT KOFK AND TOWARD DAYBREAK AT KLNK/KOMA.
MAYES
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY UNTIL NOON CST SUNDAY FOR NEZ034-044-
045- 050>053-065>068-078-088>093.
WINTER WEATHER ADVISORY UNTIL 6 AM CST SUNDAY FOR NEZ011-012-
015>018-030>033-042-043.
IA...WINTER WEATHER ADVISORY UNTIL NOON CST SUNDAY FOR IAZ043-055-
056- 069-079-080-090-091.
&&
$$