FXUS63 KOAX 212142
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
342 PM CST MON FEB 21 2011
.SHORT TERM...TONIGHT THROUGH THURSDAY.
...SNOW POTENTIAL FOR PARTS OF THE MISSOURI RIVER VALLEY
THURSDAY...
SHORT TERM CONCERNS WILL BE SOME LINGERING CLOUDS...FLURRIES...STRONGER
WINDS EARLY ON...THEN MAINLY BE TEMPERATURES. THURSDAY THERE IS A
GOOD POTENTIAL FOR PRECIPITATION WITH THE STORM SYSTEM MOVING
THROUGH THE CENTRAL/SOUTHERN PLAINS.
OVER THE NEXT FEW DAYS...WE WILL HAVE SURFACE HIGH PRESSURE BUILD
IN TONIGHT...THEN A GRADUAL WARM UP TUESDAY AND MORESO WEDNESDAY
AHEAD OF A COLD FRONTAL PASSAGE WEDNESDAY AFTERNOON. A SHORTWAVE
TROF WILL PASS THROUGH THE NORTHERN PLAINS AND ALLOW TEMPERATURES
AND DEWPOINTS TO REALLY RISE WEDNESDAY. THIS MAY LEAD TO SOME LOW
CLOUDS AND DRIZZLE TRYING TO WORK NORTH AHEAD OF THE FRONT...THEN
BE SWEPT EASTWARD DURING THE AFTERNOON...WITH A BETTER CHANCE FOR
LIGHT RAIN JUST TO THE EAST. THE SHORTWAVE TROF WILL SWING THROUGH
AND DRAG A COLD FRONT AND HAVE HIGHS TOPPING OUT IN THE 40S AND
50S.
THE NEXT SHORTWAVE TROF WILL TRACK FARTHER SOUTH ACRS COLORADO AND
NEW MEXICO...WITH GOOD AGREEMENT BTWN THE NAM/EC TRACKING THE SFC
LOW FROM OKLAHOMA INTO MISSOURI AND THE GFS A LITTLER FARTHER
SOUTH. THE NAM/EC ARE A LITTLE STRONGER WITH THIS WAVE. THE
SHORT RANGE DETERMINISTIC MODELS HAVE A CLOSED 850MB LOW OVER KS
AND THE NAM/EC ARE A BIT STRONGER CLOSING OF THE H70 AS IT TRACKS
FROM NORTHERN KANSA INTO SOUTHERN IOWA...WHILE THE GFS KEEPS IT
OPEN. THE TRACK AND INTENSITY OF THE STORM WILL BE CRITICAL FOR
THE SNOW FORECAST. WITH FAIRLY GOOD AGREEMENT IN THE TRACK...HAVE
RAISED PROBABILITY OF PRECIPITATION (POP)AND QUANTITATIVE PRECIPITATION
AMOUNTS (QPF) FOR THURSDAY. THE PRECIPITATION MAY START AS A A
MIX OF FREEZING RAIN OR SNOW LAT WEDNESDAY NIGHT. THE CURRENT
TRACK HAS THE PREDOMINANT PRECIP TYPE AS SNOW. OUR INITIAL
FORECAST WILL BE TO HAVE WATER EQUIVALENT FROM .1 TO
.4...(CLOSER TO GFS/SREF/EC) WHICH WOULD YIELD LIGHT TO MODERATE
AMOUNTS OF SNOW. THE NAM AMOUNTS AND HPC ARE BIT MORE THAN THIS
THOUGH. IN ADDITION TO THE SNOW...THE SFC WINDS ARE EXPECTED TO BE
ON THE STRONGER SIDE WITH 15 TO 20 KTS NEAR THE KANSAS
BORDER...THUS HEADLINES WILL NEED TO BE CONSIDERED IF TRACK AND
SNOW AMOUNTS REMAIN CONSISTENT.
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY.
THERE IS DECENT AGREEMENT BETWEEN MODELS FOR THE BEGINNING OF THE
LONG TERM PERIOD...FRIDAY AND SATURDAY...BUT THAT AGREEMENT
DISSOLVES SOMEWHAT SUNDAY INTO MONDAY. THE MAIN UPPER AIR FLOW
PATTERN WILL CONTINUE TO SHOW BROAD TROUGH OVER MUCH OF THE
COUNTRY FRIDAY THROUGH MONDAY...WITH MODELS SHOWING UPPER LOW
DROPPING SOUTH ALONG THE WEST COAST. HOW AND WHEN THAT UPPER LOW
EJECTS INTO THE PLAINS IS NOT CONSISTENT BETWEEN MODELS...NOR WITH
PREVIOUS RUNS AND ENSEMBLE MEMBERS OF THE SAME MODEL. THUS
FORECAST CONFIDENCE IS LOW FOR THE SECOND HALF OF THE LONG TERM
PERIOD.
UPPER WAVE WILL BE EXITING OUR AREA ON FRIDAY. LIGHT SNOW ON THE
BACK SIDE OF THIS SYSTEM WILL AFFECT MAINLY OUR EASTERN COUNTIES
THURSDAY NIGHT...WITH COLD AIR FUNNELING SOUTH BEHIND IT. STRONG MID
LEVEL JET SEGMENT AND MODERATELY STRONG SHORTWAVE DROPPING SOUTH
INTO THE NORTHERN PLAINS WILL PROVIDE LIFT FOR LIGHT SNOW AGAIN ON
FRIDAY...ESPECIALLY IN OUR NORTH. THIS CONTINUES INTO FRIDAY NIGHT
BEFORE EXITING TO THE EAST ON SATURDAY.
MODELS AND ENSEMBLE MEMBERS DIVERGE ON HANDLING OF THIS NORTHERN
PLAINS SHORTWAVE. SO EVEN FRIDAY NIGHT/SATURDAY SNOW CHANCES ARE IN
QUESTION. OPERATIONAL 12Z GFS IS MOST ROBUST WITH THIS FEATURE...AND
SPREADS A GOOD SWATH OF PRECIPITATION ACROSS THE NORTHERN PLAINS.
00Z AND 12Z ECMWF AND SEVERAL GFS ENSEMBLE MEMBERS KEEP NORTHERN
PLAINS WAVE LESS AMPLIFIED WHILE HOLDING MORE ENERGY TO OUR WEST AND
SOUTHWEST IN AXIS OF UPPER TROUGH/LOW. PUBLISHED FORECAST WILL
FOLLOW MORE CLOSELY THE GFS...WHICH IS SUPPORTED BY HPC FORECAST.
THIS WILL CARRY SMALL PRECIPITATION CHANCES THROUGH AT LEAST
SATURDAY MORNING WITH TEMPERATURES RATHER COOL FRIDAY AND SATURDAY.
GFS WOULD SUGGEST LITTLE CHANCE FOR PRECIP ON SUNDAY AS SHORTWAVE
RIDGING BRIEFLY SETS UP OVER THE CENTRAL PLAINS. 12Z ECMWF HAS COME
AROUND TO THIS LINE OF THINKING AS WELL. THEN WEST COAST UPPER LOW
BEGINS TO MOVE INTO THE PLAINS ON MONDAY...INCREASING CLOUD COVER
INITIALLY WITH PRECIP POSSIBLE IN THE AFTERNOON. FOR NOW WILL KEEP
MONDAY DRY...THINKING BRUNT OF PRECIPITATION WILL COME MONDAY NIGHT
AND TUESDAY. SOUTHERLY FLOW AHEAD OF THIS SYSTEM SHOULD PUSH TEMPS
WELL INTO THE 30S ON MONDAY.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
UPPER LEVEL LOW PRESSURE SYSTEM OVER SOUTHWEST MINNESOTA WILL MOVE
TOWARD THE GREAT LAKES THIS AFTERNOON AND TONIGHT. LOW CLOUDS ARE
EXPECTED TO LINGER ACROSS PARTS OF EASTERN NEBRASKA INTO SOUTHWEST
IOWA ALONG AND NORTH OF KOFK TO KOMA LINE UNTIL AFTER 00Z. MVFR CIGS
SHOULD MOVE EAST OF THE AREA OR DISSIPATE 00Z-03Z AS THE LOW TRACKS
FURTHER EAST. WINDS ALSO DIMINISH AFTER 00Z AS HIGH PRESSURE BUILDS
INTO THE AREA.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
ZAPOTOCNY/DERGAN/FOBERT