Forecast Discussion
NWS Omaha/Valley, NE

000
FXUS63 KOAX 071145
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
545 AM CST TUE FEB 7 2012

.AVIATION...
12Z TAFS FOR KOFK...KLNK AND KOMA.

MVFR CIGS ARE EXPECTED THROUGH THE FORECAST PERIOD...WITH
OCCASIONAL IFR CIGS/VSBYS IN LIGHT SNOW POSSIBLE THROUGH 00Z. A
LOW PRESSURE SYSTEM MOVING OUT OF THE ROCKIES WILL BRING PERIODS
OF LIGHT SNOW TO EASTERN NEBRASKA TAF SITES THROUGH THE
DAY...GRADUALLY ENDING FROM NORTHWEST TO SOUTHEAST. THE KLNK AREA
WILL SEE THE GREATEST CONCENTRATION OF SNOW...THUS A PROLONGED
PERIOD OF POSSIBLE IFR CONDITIONS THROUGH ABOUT 00Z.

DERGAN

&&

.PREV DISCUSSION... /ISSUED 321 AM CST TUE FEB 7 2012/

DISCUSSION...

MAIN FORECAST CHALLENGES WILL BE LIGHT SNOWFALL TODAY AND
TEMPERATURES THRU THE ENTIRE FORECAST.

SFC COLD FRONT CONTINUES TO SLIDE THROUGH THE FORECAST AREA EARLY
THIS MORNING. SOME MIXING ALONG THE FRONT HAS RAISED SFC TEMPS
ABOVE FREEZING HOWEVER COLDER SURGE BEHIND THE FRONT IS FINALLY
PUSHING SFC TEMPS BELOW FREEZING. LATEST WATER VAPOR IMAGERY AND
RUC ANALYSIS SHOWS MID LEVEL SHORTWAVE AXIS EXTENDING FROM WESTERN
NEBRASKA SWWD INTO COLORADO. A SECONDARY ELONGATED SHORTWAVE IS
SLOWLY MOVING SOUTH ACROSS NORTH DAKOTA AND MONTANA. REGIONAL
RADAR MOSAIC ALONG WITH SFC OBSERVATIONS SHOWS LIGHT PCPN HITTING
THE GROUND ACROSS CENTRAL NEBRASKA IN THE FORM OF FZDZ OR LIGHT
SNOW.

WE CONTINUE TO ANTICIPATE LIGHT PCPN TODAY...MAINLY
FLURRIES...WITH INCREASING DPVA AHEAD OF THE MID LEVEL SHORTWAVE.
BEST FORCING WILL BE IN ASSOCIATION WITH 700MB FRONTOGENESIS IN OUR
FAR SOUTHERN CWA. LACK OF ICE CRYSTALS IN CLOUD LAYER SUGGESTS
FREEZING DRIZZLE INTITIALLY...HOWEVER IF DOES PRECIPITATE...IT
SHOULD QUICKLY CHANGE TO SNOW AS COLD AIR CONTINUES TO DEEPEN THIS
MORNING WITH COLD SURGE BEHIND THE FRONT. STILL THINKING LESS THAN
AN INCH OF ACCUMULATION IN OUR FAR SOUTH WHERE WE HAVE A FEW LIKELY
POPS GOING. PERIOD OF FORCING WILL BE BRIEF AS WAVE MOVES OUT OF THE
AREA BY LATE AFTERNOON.

SFC HIGH PRESSURE BUILDS OVERHEAD OVERNIGHT. CHALLENGE WL BE ANY
FOG/LOW CLOUD DEVELOPMENT AND HOW LOW TEMPS WILL FALL BY WED
MORNING OVER THE SNOW PACK. WEAK SOUTHWEST RETURN FLOW SETS UP BY
LATE WEDNESDAY BUT IS SHORT LIVED AS COLD AIR FROM CANADA RETURNS.
TEMPERATURES REMAIN COOL THRU THE WEEKEND WITH A SMALL CHANCE OF
SNOW FOR OUR SOUTH LATE IN THE WEEKEND.

KERN

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$

NWS OAX Office Area Forecast Discussion

Forecast Discussion
NWS Hastings, NE

000
FXUS63 KGID 071119
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
519 AM CST TUE FEB 7 2012

.AVIATION...12Z TAF. KUEX WSR-88D EARLY THIS MORNING SHOWS LIGHT
SNOW MOVING ACROSS MUCH OF SOUTH CENTRAL NEBRASKA. THIS HAS
DEVELOPED IN RESPONSE TO AN UPPER LEVEL DISTURBANCE MOVING
THROUGH THE REGION. THE MODELS ARE IN GENERAL AGREEMENT THAT THE
CHANCE FOR LIGHT SNOW WILL CONTINUE THIS MORNING AT KGRI...AND
SOME SOLUTIONS EVEN LINGER IT INTO THE AFTERNOON. CONFIDENCE IN
HOW LONG THE SNOW WILL PERSIST IS NOT HIGH...BUT IT APPEARS IT
SHOULD BE VERY LIGHT AND WILL PROBABLY NOT CREATE ANY PROLONGED
VISIBILITY REDUCTIONS OF LESS THAN 3SM. WILL START WITH P6SM IN THE
TAF...AND LET ADJUSTMENTS OCCUR AS NECESSARY. CEILINGS ARE ALSO
TRICKY WITH IFR CONDITIONS IN PLACE AT KGRI...HOWEVER MVFR
CEILINGS ARE STARTING TO MOVE IN WEST AND NORTH OF THE TERMINAL.
PROXIMITY SOUNDINGS FROM THE NAM SUGGEST THE LOW CLOUDS WILL
PERSIST THROUGH THE ENTIRE TAF PERIOD...WHILE THE GFS IS MORE
OPTIMISTIC AND BRINGS VFR CEILINGS TONIGHT. AGAIN CONFIDENCE IS
LOW...AND HAVE GONE WITH MORE OF A MIDDLE GROUND APPROACH BY
TRENDING TO AN MVFR CEILING THIS MORNING...AND THEN HAVE KEPT IT
IN PLACE THROUGH THE NIGHT. WINDS WILL START OUT GUSTY AND FROM
THE NORTH...BUT SHOULD DIMINISH DURING THE LATE AFTERNOON.


&&

.PREV DISCUSSION... /ISSUED 500 AM CST TUE FEB 7 2012/

SHORT TERM...THROUGH THURSDAY NIGHT. PRIMARY CONCERN IS THE
GENERALLY LIGHT SNOW EVENT DURING THE NEXT 12 HOURS OR
SO...ALTHOUGH TEMPERATURES AND CLOUD TRENDS COULD POSE A CHALLENGE
AT TIMES DURING THE NEXT FEW DAYS AS WELL.

AT 09Z...OBJECTIVE SURFACE ANALYSIS AND AUTOMATED OBS REVEALED
THAT THE SURFACE COLD FRONT HAD ALL BUT CLEARED THE ENTIRE
CWA...WITH NORTH WINDS GUSTING BETWEEN 20-30 MPH IN ITS WAKE.
PRESSURE RISES WERE EMANATING FROM A RATHER PROMINENT HIGH
PRESSURE SYSTEM OF AROUND 1042MB CENTERED NEAR THE ND/CANADA
BORDER. A COMBINATION OF RADAR AND AUTOMATED OBS REVEALS THAT
INCREASING POCKETS OF -SN HAVE BEEN BREAKING OUT ACROSS THE CWA
THROUGH THE NIGHT...MAINLY ACROSS THE WESTERN HALF SO FAR. NO
ACCUMULATIONS HAVE BEEN REPORTED AT THIS TIME. A BLANKET OF LOW
STRATUS HAS SURGED SOUTH BEHIND THE COLD FRONT...AND ALTHOUGH
THERE EASILY MIGHT HAVE BEEN SOME LIGHT...PATCHY FREEZING DRIZZLE
AT TIMES DURING THE NIGHT ESPECIALLY IN THE NORTHERN
CWA...INCREASING TOP-DOWN MID LEVEL SATURATION HAS APPARENTLY
KEPT A MORE IMPACTFUL FREEZING DRIZZLE THREAT AT BAY...INSTEAD
RESULTING IN PREDOMINANT FLURRIES/SNOW. ALOFT...WATER VAPOR
IMAGERY AND SHORT TERM MODEL DATA INDICATE A RATHER COMPLEX
SITUATION UNFOLDING...AS A SHORTWAVE DROPPING SOUTH-SOUTHEAST
ACROSS THE CANADIAN BORDER CONTINUES TO PHASE WITH AN OPEN MID
LEVEL SHORTWAVE NOW PUSHING ACROSS NEB/KS.

THE MAIN ISSUE TODAY IS OBVIOUSLY HOW MUCH...IF ANY MEASURABLE
SNOW POTENTIAL EXISTS ACROSS THE CWA...AS THE GENERALLY WEAK MID
LEVEL OPEN WAVE SLIDES ACROSS THE HEART OF THE CENTRAL
PLAINS...ALONG WITH ASSOCIATED MID LEVEL SATURATION/CONVERGENCE.
OVERALL...00Z/06Z RUNS OF VARIOUS MODELS INCLUDING NAM/GFS/ECMWF
HAVE MAINTAINED A FAIRLY CONSISTENT STORY...WITH THE BEST
ACCUMULATING SNOW POTENTIAL SKIRTING SOUTH OF THE CWA ACROSS
KS...IN CLOSER PROXIMITY TO STRONGER FORCING FROM AN 80+KT 300MB
JET. HOWEVER...WITH AT LEAST WEAK FORCING ACROSS THE CWA AND
SOUNDINGS INDICATING THE MID LEVEL DENDRITIC LAYER REMAINING
FAIRLY SATURATED THROUGH AT LEAST EARLY-MID AFTERNOON...MUCH OF
THE CWA SHOULD AT LEAST REALIZE A LIGHT DUSTING OF SNOW...BEFORE
ISENTROPIC DOWNGLIDE AND RESULTANT LOSS OF MID LEVEL SATURATION
KICKS INTO GEAR LATER THIS AFTERNOON AS THE 700-500MB TROUGH AXIS
PASSES BY. OVERALL...MADE LITTLE CHANGE TO FORECAST SNOW
AMOUNTS...WITH MOST NEB ZONES LOOKING AT AMOUNTS UNLIKELY TO
EXCEED ONE HALF INCH...WHILE KS ZONES ARE MORE LIKELY TO CATCH THE
NORTHERN EDGE OF THE MORE FOCUSED SNOW AREA PASSING TO THE
SOUTH...THUS HAVING MORE POTENTIAL FOR AMOUNTS UP TO THE 1-1.5
INCH RANGE. POP-WISE...HIT IT HARDEST THROUGH 18Z...WITH AT LEAST
50S IN MOST AREAS...AND 60S-80S FROM THE TRI CITIES SOUTHWARD INTO
KS WHERE THE STRONGEST AXIS OF MID LEVEL FORCING ALIGNS. THIS
AFTERNOON...MAY NOT HAVE KEPT POPS HIGH ENOUGH...BUT KEPT 30S-50S
GOING ACROSS THE SOUTHEAST HALF OF THE CWA...WHILE ENDING SNOW
MENTION NORTHWEST. HAVE ALL POPS/SNOW MENTION GONE BY THIS EVENING
AS WAVE PASSES SOUTHEAST. HOWEVER...AS DENDRITIC LAYER DRIES
OUT...CONSIDERABLE LOW LEVEL STRATUS IS LIKELY TO STICK AROUND
WELL INTO THE NIGHT. ALTHOUGH THE CONTINUED PRESENCE OF LOW
STRATUS RAISES CONCERNS FOR A POSSIBLE LIGHT FREEZING DRIZZLE
THREAT...DECREASING LIFT AND MIXING IN THE BOUNDARY LAYER SHOULD
HELP HOLD THIS AT BAY...AND WILL NOT MENTION IN FORECAST.

AS FOR TEMPERATURES TODAY...THEY WILL ESSENTIALLY GO NOWHERE FROM
READINGS AROUND SUNRISE...WITH A NEAR-STEADY TREND LIKELY THROUGH
THE DAY OWING TO STEADY COLD AIR ADVECTION AND CLOUD COVER. THIS
SPELLS TEMPS SOMEWHERE IN THE 20S ACROSS MOST OF THE CWA THROUGH
THE DAY...WITH THE NORTH WINDS RESULTING IN WIND CHILL VALUES ONLY
AROUND 10-15 DEGREES MOST AREAS...MAKING FOR QUITE A CHILLY DAY.

TONIGHT...A 1036MB SURFACE HIGH SETTLES ACROSS THE HEART OF THE
CWA...PROMOTING DECREASING BREEZES ESPECIALLY AFTER MIDNIGHT.
ALTHOUGH THIS WOULD NORMALLY BE AN IDEAL SETUP FOR QUITE A
TEMPERATURE DROP...MODELS SUCH AS THE NAM AND ITS ASSOCIATED MET
GUIDANCE ARE QUITE INSISTENT THAT EXPANSIVE LOW STRATUS WILL
REMAIN IN PLACE OVERNIGHT...OR AT THE LEAST BE QUITE STUBBORN TO
BREAK UP. NEEDLESS TO SAY CONFIDENCE IN CLOUD TRENDS IS LOWER THAN
USUAL FOR ONLY BEING 12-24 HOURS OUT. GIVEN CONCERNS ABOUT
CLOUDS...RAISED LOW TEMPERATURES SLIGHTLY FROM PREVIOUS
FORECAST...BUT STILL TAKING MOST OF THE CWA DOWN INTO THE SINGLE
DIGITS ABOVE ZERO...EXCEPT SLIGHTLY WARMER IN THE SOUTHEAST. AGAIN
THOUGH...THIS IS HIGHLY CLOUD DEPENDENT AS ANY PROLONGED CLEARING
COULD EASILY DRIVE SOME AREAS TOWARD ZERO...WHILE IF A SOLID
STRATUS BLANKET REMAINS IN PLACE MOST AREAS PROBABLY WILL STRUGGLE
TO DROP BELOW 10.

WEDNESDAY/WEDNESDAY NIGHT...THE GENERAL STORY ALOFT IS THE
PRESENCE OF ACTIVE NORTHWEST FLOW...AS A SHORTWAVE SLIDES OUT OF
THE EASTERN MT AREA DOWN ACROSS NEBRASKA...FOLLOWING THE ENTRANCE
REGION OF THE UPPER JET. AT THIS TIME...MID LEVEL SATURATION/LIFT
DOES NOT APPEAR STRONG ENOUGH TO GENERATE PRECIP WITH THIS
WAVE...AND FORECAST WAS LEFT DRY. AT THE SURFACE...THE RIDGE AXIS
REMAIN OVER MUCH OF THE CWA DURING THE DAY...PROMOTING VARIABLE
TO LIGHT SOUTHERLY BREEZES AT BEST...WHILE WED NIGHT BREEZES PICK
UP SLIGHTLY FROM THE WEST-SOUTHWEST IN THE WAKE OF THE DEPARTING
WAVE. UNFORTUNATELY...CONFIDENCE IN CLOUD COVER REMAINS LOW...WITH
NAM/MET SOLUTIONS STUBBORNLY TRYING TO HOLD ONTO LINGERING LOW
STRATUS THE ENTIRE TIME. NOT GOING TO BUY THIS WHOLESALE YET
THOUGH...AND SKY COVER IS THUS A MIDDLE GROUND. TEMPERATURE
WISE...LOWERED HIGHS FOR WED 1-3 DEGREES MOST AREAS GIVEN LIMITED
MIXING IN RIDGE AXIS AND THE COLD START TO THE DAY...WITH HIGHS
MOST AREAS NOW IN THE 26-28 RANGE EXCEPT FOR LOW 30S SOUTHEAST.
FOR LOWS WED NIGHT...LEFT SIMILAR TO PREV FORECAST WITH 9-15 MOST
AREAS EXCEPT UPPER TEENS SOUTH.

THURSDAY/THURSDAY NIGHT...MAINTAINED DRY FORECAST AS NORTHWEST
FLOW CONTINUES. THE DAYTIME HOURS ARE CURRENTLY ADVERTISED AS THE
WARMEST OF THE NEXT SEVERAL DAYS...WITH MODEST WARMING EVIDENT AT
850MB ALONG WITH WESTERLY DOWNSLOPE FLOW. AS LONG AS THERE IS AT
LEAST PARTLY CLOUDY SKIES...THIS SHOULD YIELD HIGHS AT LEAST
SIMILAR TO THOSE ATTAINED YESTERDAY...IF NOT HIGHER...WITH MID-
UPPER 30S ACROSS MOST NEB ZONES...AND 40S COMMON IN KS ZONES.
THURS NIGHT...ANOTHER SHORTWAVE DROPPING SOUTH OUT OF CANADA SENDS
A COLD FRONT SOUTHWARD ACROSS THE CWA...WITH 850MB TEMPS DROPPING
AROUND 10 DEGREES BETWEEN 00Z AND 12Z.

LONG TERM...FRIDAY THROUGH MONDAY.  NORTHWESTERLY FLOW WILL BE IN
PLACE AT H5 ACROSS THE CENTRAL PLAINS TO START THE EXTENDED FORECAST
PERIOD.  A WAVE MOVING ACROSS THE UPPER MISSISSIPPI VALLEY WILL
CONTINUE TO USER COLDER AIR INTO THE CENTRAL PLAINS...WHICH ALSO
HELPS LOW LEVEL UPSLOPE FLOW BECOME ESTABLISHED ACROSS THE HIGH
PLAINS ON FRIDAY.  THE GFS KEEPS THE UPSLOPE FLOW IN PLACE UNTIL AT
LEAST SATURDAY WHICH COULD BRING A CHANCE OF SNOW TO PARTS OF
WESTERN NEBRASKA AND KANSAS.  THE 07.00Z ECMWF IS NOT AS AGGRESSIVE
WITH THE UPSLOPE FLOW SCENARIO...BUT EVEN IF THE GFS IS RIGHT...THE
MAIN CHANCES OF PRECIPITATION ON FRIDAY AND SATURDAY WOULD STAY WEST
OF THE FORECAST AREA.

THE PRIMARY SNOW CHANCES ACROSS THE FORECAST AREA SHOULD HOLD OFF
UNTIL SUNDAY AND SUNDAY NIGHT AS AN UPPER TROUGH ACROSS THE WESTERN
UNITED STATES WORKS ITS WAY INTO THE CENTRAL PLAINS.  THE 07.00Z
DETERMINISTIC GFS AND ECMWF ARE IN GENERAL AGREEMENT WITH THIS
SCENARIO...AND HAVE BROUGHT IN  A CHANCE OF SNOW STARTING SATURDAY
NIGHT FOR FAR SOUTHWEST PORTIONS OF THE FORECAST AREA WHICH SPREADS
NORTH AND EAST ON SUNDAY.  GEFS POPS ARE HIGHEST IN THE SOUTHERN
PORTION OF THE FORECAST AREA...WHICH LINES UP WELL WITH THE ALLBLEND
SOLUTION AND THE QPF OUTPUT FROM THE DETERMINISTIC GFS/ECMWF...SO
HAVE FOLLOWED THAT LAYOUT IN THE GRIDS.  OBVIOUSLY ITS STILL
EXTREMELY EARLY TO TALK ABOUT SNOW AMOUNTS...BUT WITH THE GENERAL
CONSENSUS AMONGST THE VARIOUS MODEL SOLUTIONS...IT APPEARS THAT AT
LEAST A PART OF THE FORECAST AREA COULD RECEIVE SOME SNOW
ACCUMULATIONS OVER THE WEEKEND.  AT THIS POINT THE AREAS BEING
TARGETED APPEAR TO BE NORTH CENTRAL KANSAS...AND AREAS GENERALLY
SOUTH OF INTERSTATE 80 IN SOUTH CENTRAL NEBRASKA.

IN REGARDS TO TEMPERATURES...THE LATEST MODEL RUNS HAVE TRENDED
COOLER...AND WITH THE THREAT OF SNOW OVER THE WEEKEND...THAT IDEA
APPEARS REASONABLE.

PREV DISCUSSION... /ISSUED 1124 PM CST MON FEB 6 2012/

AVIATION...06Z TAF. A COLD FRONT DROPPING SOUTHEAST ACROSS THE
REGION EARLY THIS MORNING WILL MOVE ACROSS KGRI NEAR THE START OF
THE FORECAST PERIOD. AN AREA OF STRATUS WILL ARRIVE NEARLY IN
TANDEM WITH THE FRONT WHICH WILL DROP CEILINGS INTO AT LEAST THE
MVFR RANGE. FORECAST SOUNDINGS SUGGEST CEILINGS COULD AT TIMES
FALL INTO IFR LEVELS...WITH LIGHT SNOW OR FLURRIES POSSIBLE. THERE
IS ALSO SOME CONCERN FOR LIGHT FREEZING DRIZZLE...BUT AT THIS
POINT WILL STAY WITH FLURRIES AND ADJUST IF IT BECOMES MORE OBVIOUS
THAT THE FREEZING DRIZZLE WILL MATERIALIZE. THE LOWER CEILINGS
ARE EXPECTED TO CONTINUE AT KGRI THROUGH MUCH OF THE FORECAST
PERIOD...BUT MAY IMPROVE LATE.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$

SHORT TERM...PFANNKUCH
LONG TERM/AVIATION...KING

NWS GID Office Area Forecast Discussion