Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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665
FXUS63 KOAX 020230
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
830 PM CST MON FEB 1 2016

.UPDATE...
ISSUED AT 830 PM CST MON FEB 1 2016

NO BIG CHANGES TO PREVIOUS FORECAST. WATER VAPOR SATELLITE IMAGERY
LOOP EARLY THIS EVENING SHOWED CLOSED MID TROPOSPHERIC CIRCULATION
CENTER OVER SOUTHEAST COLORADO. DIFFLUENT FLOW WITH NEGATIVELY
TILTED TROUGH WAS CREATING LIFT AND SLOWLY SATURATING THE ATMOSPHERE
LOCALLY. HEAVY SNOW WAS FALLING TO THE WEST IN NORTHWEST KANSAS AND
SOUTHWEST NEBRASKA. LIGHTNING HAD DEVELOPED OVER PARTS OF
SOUTHWEST OKLAHOMA.

00Z KOAX SOUNDING HAD AROUND 0.41 PW BUT LOWER LEVELS WERE STILL
FAIRLY DRY. LAPSE RATES ABOVE 600 MB WERE FAIRLY STEEP. 300 MB
CHART AT 00Z HAD A 125 KT JETSTREAK PUNCHING NORTHEAST FROM THE
OKLAHOMA/KANSAS BORDER REGION. AT 500 MB HEIGHT FALLS ESTIMATED AT
UP TO 150 METERS IN THE PAST 12 HOURS WERE OVER EASTERN NEW
MEXICO. THERE WAS A MODEST THERMAL GRADIENT AT 700 MB ACROSS THE
CENTRAL PLAINS AHEAD OF THE LOW BACK OVER COLORADO. AT 850 MB...
THERE WAS NOT MUCH COLD AIR NOTED. ACROSS NEBRASKA...850 MB
TEMPERATURES WERE GENERALLY -2 TO -5 DEGREES CELSIUS. HIGHEST
850 MB DEWPOINTS WERE 6 TO 10 DEGREES CELSIUS ALONG THE GULF
COAST. SURFACE LOW AT 02Z WAS STILL OVER SOUTHEAST COLORADO...
WITH ANOTHER IN SOUTHWEST OKLAHOMA.

EXPECT THAT RADAR ECHOES WILL CONTINUE TO INCREASE OVERNIGHT.
SOME OF THE RECENT SHORT RANGE MODELS CONTINUE TO INDICATE A
FAIRLY STRONG BAND OF 700-600 MB FRONTOGENESIS DEVELOPING FROM
PARTS OF SOUTHWEST INTO NORTHEAST NEBRASKA AND NORTHERN IOWA.
FARTHER SOUTH...IN THE TROWAL AREA THAT WILL BE MOVING INTO THE
NEBRASKA/KANSAS/MISSOURI BORDER REGION...THUNDER IS POSSIBLE WITH
NEGATIVE EPV IN THE 700-500 MB LAYER BY AROUND 12Z. THAT AREA OF
INSTABILITY MAY LIFT UP INTO THE OMAHA AREA IN THE MORNING AS DRY
SLOT PUNCHES INTO SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. IT WILL
BE INTERESTING TO SEE IF THAT ACTUALLY HAPPENS. IF IT DOES...THERE
MAY BE A BURST OF HEAVY SNOW IN THE MORNING (AND ADDED SOME ISOLD
THUNDER INTO THE FORECAST)...A BRIEF LULL BY NOON...AND THEN SNOW
PICKING UP AGAIN IN THE AFTERNOON.

AGAIN NO BIG CHANGES FROM PREVIOUS FORECAST. WILL UPDATE ALL TEXT
PRODUCTS BEFORE 9 PM CST.

&&

.SHORT TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 252 PM CST MON FEB 1 2016

ALL EYES FOCUS ON THE IMMINENT STORM SYSTEM.  SUBJECTIVE 12Z UPPER
AIR ANALYSIS INDICATES DIGGING WESTERN US TROUGH...WITH 500MB HEIGHT
FALLS UP TO 200M IN NORTHERN AZ.  150KT+ UPPER-LEVEL JET STREAK WAS
NOTED PUNCHING IN BEHIND THE TROUGH.  AN 850MB RIDGE WAS IN PLACE
FROM EASTERN KS INTO CENTRAL/EASTERN NEB...ASSOCIATED WITH DRIER
AIR...WITH THE 0C TEMPERATURE LINE ROUGHLY ALONG THE KS-NEB BORDER
AND INTO NORTHERN MO.  SURFACE LOW AT 20Z WAS CENTERED IN SOUTHWEST
TO CENTRAL CO...WITH BROAD SURFACE RIDGE FROM THE DAKOTAS TO EASTERN
IA...AND WITH INCREASING PRESSURE GRADIENT FROM WESTERN NEB INTO KS.

WINTER STORM SYSTEM IS STILL ON TRACK TO IMPACT EASTERN NEB/WESTERN
IA...BUT OF COURSE...THE DEVIL IS IN THE DETAILS.  PRECIPITATION
WILL BEGIN AS RAIN SOUTH AND A RAIN/SNOW MIX ELSEWHERE...WITH
CHANGEOVER TO SNOW PROBABLY HAPPENING SHORTLY AFTER ONSET AS
TEMPERATURE PROFILE WET-BULBS.  EVEN SO...SURFACE TEMPERATURES WILL
HOVER VERY CLOSE TO FREEZING ALL OF TONIGHT IN MOST OF THE
AREA...WITH TEMPS FALLING A BIT LOWER IN NORTHEAST NEB AND STAYING
ABOVE FREEZING IN FAR SOUTHEAST NEB/SOUTHWEST IA.  MODELS ARE TIMING
PRECIPITATION ONSET SOMEWHAT MORE SLOWLY...SOME OF THEM HOLDING OFF
ON MUCH OR ANY PRECIPITATION IN SOUTHWEST TO WEST CENTRAL IA BEFORE
12Z.  THUS...SNOW AMOUNT FORECAST FOR 06-12Z IS PERHAPS LOWEST
CONFIDENCE OF ALL...AS THESE NEGATING FACTORS WORK AGAINST
SUBSTANTIAL INCREASE IN VERTICAL ASCENT AS FRONTOGENETIC BANDING
FROM 850-700MB DEVELOPS...ALONG WITH LOW STATIC STABILITY OR EVEN
INSTABILITY...AND WITH INCREASING SYNOPTIC FORCING FOR ASCENT AS THE
UPPER-LEVEL TROUGH EJECTS TOWARD THE PLAINS AND QG-VECTOR
CONVERGENCE AIMS AT THE MO RIVER VALLEY.  NORTHEAST WINDS WILL
INCREASE THROUGH THE NIGHT AS RIDGE SLIDES AWAY AND PRESSURE
GRADIENT TIGHTENS. HAVE NOTED IN PARTICULAR THAT SOME OF THE HIGHER-
RES MODELS HAVE TRENDED TOWARD DEVELOPING A BAND OF SNOW ON THE
EARLIER SIDE IN NORTHEAST NEB TO NORTHWEST IA...ALONG THE AXIS OF
700MB FRONTOGENESIS.  DID FACTOR THAT INTO INCREASING SNOWFALL
AMOUNTS IN THAT AREA...BUT MAY NEED TO WATCH FOR POTENTIAL FOR A
BAND OF LOCALLY HIGHER SNOWFALL AMOUNTS IF THAT DOES MATERIALIZE.

PRECIPITATION SHOULD BE OR BECOME ALL SNOW BY AROUND TUESDAY MORNING
IN ALL BUT THE SOUTHEASTERNMOST CWA...WHERE TEMPERATURES WILL
CONTINUE TO HOVER ABOVE FREEZING AT THE SURFACE THROUGH AROUND
850MB.  SLOWER SOLUTIONS NOW FAVOR TUESDAY MORNING AND AFTERNOON AS
THE TIME OF PEAK VERTICAL ASCENT AND MESOSCALE BANDING...AND THUS
THE PEAK FOR SNOW ACCUMULATIONS...WITH TEMPERATURES HOLDING STEADY
IN THE UPPER 20S TO NEAR FREEZING.  WINDS WILL INCREASE TO AROUND 20-
30KT...WITH GUSTS UP TO AROUND 35-40KT DURING THE AFTERNOON. DESPITE
THE HEAVY AND WET CHARACTER OF THE SNOW...WINDS SHOULD BE STRONG
ENOUGH TO CREATE SUBSTANTIAL BLOWING AND DRIFTING.  STORM HAS TAKEN
A SLIGHT NORTHWARD SHIFT...BRINGING HIGHER ACCUMULATIONS TOWARD
NORTHEAST NEB...AND HAVE UPGRADED THOSE COUNTIES IN A BLIZZARD WATCH
TO A BLIZZARD WARNING AS WINDS SHOULD BE AS INTENSE THERE AS IN THE
REST OF THE BLIZZARD WARNING AREA.  DID TWEAK SNOW ACCUMULATIONS
DOWN A BIT IN SOUTHEAST NEB/SOUTHWEST IA WITH WARMER AIR HANGING ON
LONGER. OTHERWISE HAVE LEFT SNOW ACCUMULATION FORECAST AND HEADLINES
INTACT...WITH HIGHEST SNOW ACCUMULATIONS PEAKING IN THE 9-13 INCH
RANGE...AND WITH A SUBTLE NORTHWARD SHIFT OF THE AXIS OF HEAVIEST
SNOW.

IT BEARS REPEATING THAT THERE IS A VERY FINE LINE BETWEEN EXPECTED
CONDITIONS IN THE BLIZZARD WARNING AND WINTER STORM WARNING AREAS.
BOTH WILL SEE SUBSTANTIAL SNOW ACCUMULATIONS.  THE MAIN
DIFFERENTIATING FACTOR IS THAT WE ARE MORE CONFIDENT IN *SUSTAINED*
BLIZZARD CONDITIONS IN THE BLIZZARD WARNING AREA.  IN THE WINTER
STORM WARNING AREA...WE DO EXPECT INTERMITTENT NEAR-BLIZZARD/WHITE-
OUT CONDITIONS...JUST LESS LIKELY TO HOLD ON FOR 3 CONSECUTIVE
HOURS.  THE DIFFERENCE IS SOMEWHAT SEMANTIC AND TECHNICAL...AND
IMPACTS WILL BE QUITE SIMILAR ACROSS BOTH AREAS.

BLOWING AND DRIFTING SNOW IS LIKELY TO CONTINUE EVEN AFTER SNOW
DIMINISHES ON TUESDAY NIGHT/WEDNESDAY MORNING...UNTIL WIND SPEEDS
FINALLY SLACKEN BELOW 10-15KT ON WEDNESDAY AFTERNOON.  WEDNESDAY
WILL REMAIN COOL...WITH TEMPERATURES BEGINNING TO MODERATE BACK
TOWARD NORMAL BY THURSDAY.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 252 PM CST MON FEB 1 2016

QUIETER WEATHER WILL CONTINUE THROUGH SATURDAY...WITH NEAR- TO ABOVE-
NORMAL TEMPERATURES. MODELS DO HINT AT A DIGGING TROUGH ARRIVING
FROM THE NORTHWEST AND BRINGING HIT-AND-MISS POTENTIAL FOR LIGHT
SNOW.  WITH FOCUS ON THE SHORT TERM...DID TRY TO CLEAN UP POPS JUST
A TOUCH TO BE LESS SPOTTY AND MORE FOCUSED ON TIMING WITH THE
TROUGH/FRONTAL PASSAGE.  SYSTEM ALSO WILL BRING TEMPERATURES BACK
DOWN TO NEAR- TO BELOW-NORMAL READINGS.

&&

.AVIATION...(00Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 558 PM CST MON FEB 1 2016

THROUGH 06Z...THE MOISTURE PROFILES WILL CONTINUE TO MOISTEN WITH
CEILINGS LOWERING AND SPRINKLES...THEN A RAIN/SNOW MIX AND SNOW
DEVELOPING. KLNK DID REPORT SOME LIGHT RAIN IN THE LAST HOUR AND
WE HAD SPRINKLES HERE AT THE NWS IN VALLEY...HOWEVER NOT MUCH IS
REACHING THE GROUND. VFR CIGS WILL DETERIORATE TO MVFR AS AN AREA
OF FRONTOGENESIS/UPPER LEVEL SUPPORT LIFTS NORTH AND LARGE SCALE
OMEGA ARRIVES. THE SPC HRRR AND THE NAM SHOW A GAP IN THE
LIFT...HOWEVER THE 4KM WRF TENDS TO FILL THE SNOW AREA IN AFTER
06Z. BETWEEN 06Z-12Z...THERE IS IMPRESSIVE DEVELOPMENT AND
DETERIORATION FROM MVFR/IFR TO VLIFR WITH VERY STRONG NORTHEAST
WINDS (20 TO 30KTS WITH GUSTS 30 TO 40KTS. IN
ADDITION...CONVECTION APPEARS TO DEVELOP TOWARD THE KANSAS BORDER
THEN PUSHES NORTH INTO SOUTHEAST NEBRASKA AND SOUTHWEST IOWA
BETWEEN 11-13Z AND THIS SHOULD BE WHEN WE SEE MORE WIDESPREAD
VLIFR. CONTINUE WITH VLIFR CONDITIONS IN +SN/BLSN THROUGH
18-20Z...THEN NORTHEAST WINDS DECREASING TO 15G25KTS.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 4 AM CST WEDNESDAY
     FOR NEZ045-051>053-066-067-078-088.

     WINTER WEATHER ADVISORY FROM 3 AM TUESDAY TO 4 AM CST WEDNESDAY
     FOR NEZ068-089>092.

     BLIZZARD WARNING UNTIL 4 AM CST WEDNESDAY FOR NEZ011-012-016-017-
     030-031-042>044-050-065.

     BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO 4 AM CST WEDNESDAY FOR
     NEZ015-018-032>034.

IA...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 4 AM CST WEDNESDAY
     FOR IAZ055-056-069-079-080.

     WINTER WEATHER ADVISORY FROM 3 AM TUESDAY TO 4 AM CST WEDNESDAY
     FOR IAZ090-091.

     BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO 4 AM CST WEDNESDAY FOR
     IAZ043.

&&

$$

UPDATE...MILLER
SHORT TERM...MAYES
LONG TERM...MAYES
AVIATION...ZAPOTOCNY



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