337
FXUS63 KOAX 211157
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
557 AM CST MON JAN 21 2019
SHORT TERM
(TODAY THROUGH WEDNESDAY)
ISSUED AT 330 AM CST MON JAN 21 2019
THE MAIN FORECAST CONCERNS ARE IN REGARDS TO THE SYSTEM THAT WILL
BRING MIXED PRECIPITATION AND SOME ACCUMULATING SNOW TO PORTIONS
OF THE FORECAST AREA. LIGHT PRECIPITATION MAY START AS EARLY AS
THIS AFTERNOON, THE SPREAD OVER PART OF THE AREA. STARTED A WINTER
WEATHER ADVISORY AT 3 PM FROM ALBION TO COLUMBUS, DAVID CITY AND
SEWARD, FOR MUCH OF THE AREA AT 6 PM AND THEN IN FAR SOUTHWEST
IOWA AT MIDNIGHT. THESE ADVISORIES LAST UNTIL 6 PM TUESDAY, AT
LEAST FOR NOW.
MODEL UNCERTAINTY IS STILL QUITE LARGE FOR AS CLOSE TO THE EVENT
AS WE ARE. ADJUSTED SNOW AND ICE AMOUNTS A BIT, AND EXPECT THAT WE
WILL DO THAT A FEW MORE TIMES. SURFACE TEMPERATURES, AND IF THERE
WILL BE ICE ALOFT WHEN IT IS PRECIPITATING, WILL BE CRUCIAL TO
ICE AND SNOW AMOUNTS.
MAIN FEATURES OF NOTE FROM THE UPPER AIR CHARTS LAST EVENING WERE
12 HOUR HEIGHT FALLS OF 50 TO 150 METERS AT 500 MB OVER THE
WESTERN US. HIGHEST VALUE WAS AROUND 150 METERS AT KREV. A JET
STREAK AT 300 MB OF AROUND 140 KNOTS FROM EASTERN IA INTO CENTRAL
IL WAS HELPING DRIVE AN AREA OF SNOW FROM SOUTHEAST SD INTO IA
EARLY THIS MORNING, IN THE RIGHT ENTRANCE REGION OF THE JET. TO
THE WEST, THERE WAS A 125 KNOT JET STREAK PUNCHING NORTHEAST FROM
SOUTHERN CA ACROSS SOUTHERN NV. AT 850 MB COLDEST AIR WAS OVER THE
GREAT LAKES REGION BUT WARMER AIR WAS NOTED WITH +2 C TEMPS AT
BOTH RAPID CITY AND NORTH PLATTE. SOME OF THIS WARMER AIR ALOFT
WILL MOVE INTO THE AREA AS SHOWN IN FORECAST SOUNDINGS. MESSY
PRECIPITATION PATTERN SETS UP TONIGHT. OF THE 00Z MODELS, THE GFS
AND GEM SHOWED THE HEAVIEST PRECIPITATION WITH A DEFORMATION ZONE,
WHILE THE NAM WAS DRIER/SHOWED LESS SNOW. THE ECMWF ALSO HAD LOWER
SNOW AMOUNTS THROUGH MID DAY TUESDAY, THEN HAD A BAND OF 2 TO 4
INCHES TUESDAY AFTERNOON. USED WPC GUIDANCE AND COORDINATED WITH
NEIGHBORING OFFICES, USING SOMEWHAT OF A MODEL BLEND, SINCE THERE
IS QUITE A BIT OF UNCERTAINTY. EXPECT THAT WITH GOOD UPPER AIR
SOUNDINGS THIS MORNING THAT MODELS WILL HOPEFULLY COME INTO BETTER
AGREEMENT. THE SYSTEM MOVES THROUGH MAINLY AS AN OPEN WAVE, BUT
SOME MODEL OUTPUT TRIES TO CREATE A WEAK CLOSED LOW AT 500 MB IN
OUR AREA.
THERE SHOULD BE DECENT MOISTURE TO WORK WITH (750-700 MB MIXING
RATIOS AROUND 3 G/KG AT TIMES, BUT MID LEVEL OMEGA VALUES ARE NOT
EXTREMELY IMPRESSIVE.
WINDS WILL BE INCREASING TUESDAY WITH COLDER AIR MOVING IN AND
TEMPERATURES SHOULD FALL THROUGH THE DAY. IN LOCATIONS WHERE SNOW
IS ON THE GROUND, THERE WILL BE BLOWING SNOW, ESPECIALLY FOR THE
NORTHERN HALF OF THE FORECAST AREA. TEMPERATURES SHOULD FALL TO
THE SINGLE DIGITS FROM NORTHEAST NE INTO WESTERN IA WITH LOWS 10
TO 15 IN SOUTHEAST NE. MILDER AIR WILL TRY TO MOVE IN FROM THE
WEST WEDNESDAY.
LONG TERM
(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 330 AM CST MON JAN 21 2019
A STRONG COLD FRONT SHOULD PUSH THROUGH THE REGION WEDNESDAY NIGHT
WITH SOME SNOW SHOWERS. THE 00Z GFS MODEL WAS PROBABLY A BIT TOO
AGGRESSIVE WITH SNOW AMOUNTS, BUT WE COULD SEE SOME VALUES TO
AROUND AN INCH OR MORE. LOWS THURSDAY NIGHT SHOULD DROP BELOW ZERO
FOR MOST OF THE AREA. FRIDAY AND SATURDAY WILL BE COLD THEN EXPECT
A SMALL MODERATION IN TEMPS.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 458 AM CST MON JAN 21 2019
AVIATION CONCERNS ARE MOSTLY ANTICIPATE -FZDZ EXPANDING ACROSS ERN
NE THIS AFTERNOON AS WELL AS DURATION. EXPECT ONSET OF -FZDZ AT
ALL TAF SITES BY LATE AFTERNOON AND CONTINUING THRU THE MAJORITY
OF THIS EVENING. POTENTIAL ICE ACCUMULATIONS THRU TONIGHT
ANYWHERE FROM 0.01"-0.02" AT KOMA WITH UP TO 0.01" AT KOFK AND
KLNK.
OAX WATCHES/WARNINGS/ADVISORIES
NE...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST
TUESDAY FOR NEZ011-012-015>018-031>034-043>045-051>053-
066>068-078-088>090.
WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 6 PM CST
TUESDAY FOR NEZ030-042-050-065.
IA...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST
TUESDAY FOR IAZ043-055-056-069.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST
TUESDAY FOR IAZ079-080-090-091.
SHORT TERM...MILLER
LONG TERM...MILLER
AVIATION...DEE
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