000
FXUS63 KGID 061109
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
509 AM CST FRI DEC 6 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 509 AM CST FRI DEC 6 2013

TODAY...THIS IS SOME IMPRESSIVE COLD FOR NOT HAVING SNOW ON THE
GROUND. TYPICALLY IT TAKES A NICE SNOW PACK TO GET HIGH TEMPERATURES
THIS COLD IN EARLY DECEMBER. NORMAL HIGHS ARE CURRENTLY AROUND
40F...BUT WE WILL BE NEARLY 30 DEGREES BELOW NORMAL TODAY WITH HIGHS
NEAR OR JUST ABOVE 10 DEGREES IN THE TRI CITIES. THE UPPER LEVEL
PATTERN IS A CLASSIC PATTERN FOR A PLAINS COLD AIR OUTBREAK WITH A
LARGE UPPER RIDGE OVER THE EASTERN PACIFIC NORTHWARD INTO ALASKA.
THIS FORCES A DEEP TROUGH INTO MUCH OF THE CENTRAL AND WESTERN
UNITED STATES WITH A STEADY STREAM OF COLD AIR DRAINAGE FROM THE
POLAR REGION INTO THE UNITED STATES. ACTUALLY WENT CLOSER TO THE
WARMER END OF THE GUIDANCE TEMPERATURES TODAY DUE TO LACK OF SNOW
COVER AND IT IS STILL FRIGID.

TONIGHT...THE SFC RIDGE AXIS WILL MOVE ACROSS THE FORECAST AREA
RESULTING IN DECREASING WINDS AND A WIND SHIFT FROM NORTH TO
SOUTHEAST. SKIES WILL BE MOSTLY CLEAR THROUGH MUCH OF THE
NIGHT...ALTHOUGH CLOUDS MAY INCREASE ACROSS WESTERN ZONES NEAR DAWN.
THE COMBINATION OF LIGHT WINDS...MOSTLY CLEAR SKIES...UNDER AN
ALREADY EXCEPTIONALLY COLD AIR MASS...WILL LIKELY RESULT IN ACTUAL
LOW TEMPERATURES BELOW ZERO ACROSS THE ENTIRE FORECAST AREA. THE
WIND CHILL TEMPERATURES SHOULD NOT BE TOO MUCH COLDER THAN THE
ACTUAL AIR TEMPERATURES SINCE THE WIND WILL BE LIGHT.

.LONG TERM...(SATURDAY DAYTIME THROUGH THURSDAY)
ISSUED AT 509 AM CST FRI DEC 6 2013

PRECIPITATION-WISE...BY FAR THE ONLY HIGHLIGHT OF THIS 6-DAY
PERIOD IS WHAT IS EXPECTED TO BE A REASONABLY
LOW-IMPACT...DRY/FLUFFY SNOW EVENT CENTERED DURING THE 24-30 HOUR
PERIOD BETWEEN SAT EVENING AND SUN EVENING. WILL GO INTO MORE
DETAIL BELOW...BUT WILL STATE UP-FRONT THAT STORM-TOTAL SNOWFALL
FORECAST WAS LOWERED SLIGHTLY FROM PREVIOUS FORECAST...ON THE
ORDER OF 1/4 TO 1/2 INCH IN MOST AREAS. HOWEVER...THIS STILL
YIELDS A FAIRLY BROAD STORM TOTAL OF GENERALLY 1.5 TO 3 INCHES
ACROSS THE AREA. ALSO WANT TO EMPHASIZE UP FRONT THAT WE ARE STILL
AT LEAST 36-42 HOURS AWAY FROM THE ONSET OF SNOW IN MOST
AREAS...AND THUS THE STORM TOTAL FORECAST IS STILL VERY-MUCH
SUBJECT TO SOME FURTHER MODIFICATION...WHICH ACCORDING TO THE LAST
FEW SUITES OF 00Z/06Z MODELS COULD MEAN AT LEAST A SLIGHT
CONTINUED DOWNWARD TREND IN FUTURE FORECASTS. OTHERWISE...THIS
NOTABLE COLD STRETCH WITH THE VAST MAJORITY OF THE CWA FAILING TO
REACH 20 DEGREES WILL CONTINUE RIGHT ON THROUGH MONDAY...BEFORE A
MODEST "WARM-UP" INTO THE 20S-30S IS FORECAST FOR THE TUES-THURS
TIME FRAME. AS ALLUDED TO IN THE AFTERNOON DISCUSSION BACK ON DEC.
3RD...FOR MUCH OF THE CWA THE ONGOING COLD STRETCH WILL PROBABLY
END UP AS THE MOST SIGNIFICANT ONE IN ALMOST 4 YEARS...SINCE EARLY-
JANUARY 2010.

GETTING INTO MORE DETAIL AND STARTING WITH SATURDAY/SATURDAY
NIGHT...VARIOUS 00Z/06Z MODELS ARE IN GOOD AGREEMENT REGARDING THE
BIG-PICTURE ALOFT...AS THE PERIOD STARTS OUT WITH A BROAD...LOW
AMPLITUDE TROUGH STRETCHED ACROSS MUCH OF THE CONUS. BUT AS TIME
GOES BY...A MODESTLY STRONG SHORTWAVE TROUGH WILL DIG SOUTHWARD AND
SLIDE EASTWARD FROM A POSITION CENTERED IN THE PACIFIC
NORTHWEST/INTERMOUNTAIN WEST SATURDAY DAYTIME...BEFORE ENTERING
THE CENTRAL ROCKIES/CENTRAL PLAINS REGION SATURDAY NIGHT. BY
SUNRISE SUNDAY...A STOUT 125+KT UPPER JET STREAK AT 300 MILLIBARS
IS FORECAST TO STRETCH ALONG AN AXIS FROM SOUTHEAST CO ACROSS KS
INTO IL. STARTING OUT SATURDAY MORNING...CONFIDENCE REMAINS FAIRLY
HIGH IN SNOW-FREE CONDITIONS...BUT AS THE DAY WEARS ON HIGH AND
MID LEVEL CLOUD COVER SHOULD BE ON A STEADY INCREASE...WITH MID
CLOUDS LARGELY DEVELOPING IN RESPONSE TO INCREASING ISENTROPIC
LIFT AS EVIDENT PER THE 06Z NAM ON SURFACES SUCH AS 285K. ALTHOUGH
ITS QUITE POSSIBLE THAT THE ENTIRE AREA GETS THROUGH SUNSET
WITHOUT SEEING ANY SNOW AT ALL...OPTED TO RUN WITH A SLIGHT CHANCE
OF AFTERNOON FLURRIES ACROSS MUCH OF THE WESTERN 1/2 OF THE
CWA...WITH A SLIGHT CHANCE OF LIGHT MEASURABLE SNOW IN THE FAR
WEST. CERTAINLY BETTER CHANCES FOR SNOW GET GOING SATURDAY
EVENING/NIGHT...BUT VARIOUS MODELS SUCH AS THE NAM/GFS/ECMWF STILL
VARY CONSIDERABLY ON WHETHER ACCUMULATIONS BEGIN IN THE
EVENING...OR HOLD OFF MORE SO UNTIL AFTER MIDNIGHT. AT LEAST FOR
THE TIME BEING...WILL ADVERTISE 40-60 POPS IN THE EVENING...AND
THEN SOMEWHAT HIGHER 60-70 POPS POST-MIDNIGHT. AGAIN...THE MAIN
LIFTING MECHANISM WILL BE PERSISTENT...BROAD ISENTROPIC LIFT OVER
THE REGION...AIDED BY AT LEAST A SLIGHTLY-COUPLED UPPER JET
STRUCTURE BETWEEN THE ENTRANCE REGION OF ONE JET STREAK DEPARTING
EASTWARD ACROSS THE GREAT LAKES...AND THE EXIT REGION OF THE
UPSTREAM JET ARRIVING IN THE CENTRAL PLAINS. HOPEFULLY THE
SPATIAL/TIMING DETAILS ON SATURDAY NIGHT SNOWFALL CAN BE BETTER-
ADJUSTED IN THE NEXT FEW FORECAST CYCLES...BUT AT LEAST FOR NOW
HAVE TOTAL NIGHT-TIME ACCUMULATION OF 1 TO 1.5 INCHES IN MOST
AREAS. AS FOR SURFACE WINDS SAT/SAT NIGHT...THEY WILL START OUT
QUITE LIGHT AROUND SUNRISE...BUT THEN TRANSITION TO FAIRLY STEADY
SUSTAINED 10-15 MPH WITH SOME SLIGHTLY HIGHER GUSTS THROUGH THE
REST OF THE PERIOD AS THE SURFACE HIGH DEPARTS EASTWARD AND
PRESSURE FALLS COMMENCE TO THE WEST. THESE SPEEDS SHOULD BE LOW
ENOUGH TO KEEP BLOWING SNOW ISSUES TO A MINIMUM. TEMP-WISE...MADE
ONLY MINOR TWEAKS TO SATURDAY HIGHS/SAT NIGHT LOWS...WITH HIGHS
MAINLY 13-18 AND LOWS 6-11. ALTHOUGH SUB-ZERO WIND CHILLS WILL
OCCUR AGAIN SATURDAY NIGHT...THE COLDEST WIND CHILLS OF THIS
24-HOUR PERIOD WILL ACTUALLY OCCUR RIGHT AWAY SAT MORNING AS MUCH
OF THE AREA AVERAGES BETWEEN 10 TO NEAR DEGREES BELOW ZERO...BUT
APPEARS TO BE AT LEAST SLIGHTLY SHORT OF JUSTIFYING AN ADVISORY
GIVEN OUR CRITERIA OF -20F.

SUNDAY/SUNDAY NIGHT...THE STORY IN THE MID/UPPER LEVELS INVOLVES
THE AFOREMENTIONED SHORTWAVE TROUGH LIFTING EAST-NORTHEAST THROUGH
THE HEART OF THE CENTRAL PLAINS...WITH THE MAIN VORT MAX TRACKING
ACROSS KS ACROSS SOUTHEAST NEB. MEANWHILE...AN EVOLUTION TO A
LARGER-SCALE POSITIVE TILT TROUGH AXIS WILL TAKE SHAPE AS THE
CENTRAL PLAINS WAVE PHASES WITH ANOTHER SHORTWAVE DROPPING
SOUTHEAST INTO THE DAKOTAS OUT OF SOUTHERN CANADA. WITH STRONG
DYNAMIC FORCING NOT REALLY COMING INTO PLAY...SNOW CHANCES ON
SUNDAY INTO SUNDAY EVENING WILL REMAIN DRIVEN INITIALLY BY
CONTINUED ISENTROPIC LIFT...AND THEN A BRIEF PERIOD OF MID LEVEL
FRONTOGENESIS/CONVERGENCE AS THE INITIAL MID LEVEL TROUGH AXIS
PASSES BY IN THE AFTERNOON/EVENING. ALTHOUGH THE MOISTURE SUPPLY
REMAINS LIMITED WITH THIS SYSTEM...A DEEP COLD LAYER WITHIN THE
DENDRITIC GROWTH ZONE SHOULD CONTINUE PROMOTING GENERALLY LIGHT
ACCUMULATING SNOW AT LEAST THROUGH THE DAYTIME HOURS...BEFORE
PRECIPITATION ENDS/SHIFTS EAST OF THE CWA DURING THE EVENING.
UNCERTAINTY IN HOW SUNDAY PLAYS OUT THOUGH IS STILL FAIRLY
HIGH...AS MODELS SUCH AS THE NAM ACTUALLY DEPICT LITTLE IF ANY
ACCUMULATING SNOW DURING THE DAY...WHILE BOTH THE ECWMF AND
ESPECIALLY THE GFS KEEP WIDESPREAD LIGHT SNOW IN PLACE. THE
OFFICIAL FORECAST...AT LEAST FOR NOW...CALLS FOR SUNDAY
DAYTIME/EARLY EVENING ACCUMULATIONS ONLY ON THE ORDER OF 1
INCH...RESULTING IN THE STORM-TOTAL OF GENERALLY 2-3 INCHES. POP-
WISE...THOUGHT IT A BIT SOON TO BREAK DAYTIME POPS INTO ANY MORE
DETAIL THAN A 12-HOUR BLOCK OF 60-70 POPS...ALTHOUGH THIS MAY BE
OVERDONE IF IT TURNS OUT THE NAM IS ONTO SOMETHING. IN THE
EVENING...LINGERED ONLY 20-30 POPS ACROSS MAINLY THE EASTER HALF
OF THE CWA...WITH NOTHING POST-MIDNIGHT. TEMP-WISE THROUGH THE
PERIOD...AGAIN MADE LITTLE CHANGE...WITH HIGHS GENERALLY 14-20 AND
LOWS MAINLY LOWER SINGLE DIGITS. AS BREEZES PICK UP AND SHIFT
NORTHWESTERLY SUNDAY NIGHT...LATE NIGHT/EARLY MONDAY MORNING WIND
CHILLS ARE AGAIN FORECAST TO DROP INTO THE 10 TO NEAR-20 BELOW
RANGE IN MOST AREAS.

TAKING A FAIRLY BRIEF LOOK AT THE MONDAY THROUGH THURSDAY
PERIOD...HAVE MAINTAINED A PRECIP-FREE FORECAST THROUGHOUT THIS
ENTIRE TIME AT LEAST FOR NOW...BUT MAY HAVE TO KEEP AN EYE OUT FOR
THE EVENTUAL INCLUSION OF AT LEAST SOME PASSING FLURRIES MAINLY IN
THE TUES NIGHT-WED TIME FRAME. IN THE LARGE SCALE ALOFT...A
GENERALLY NORTHWESTERLY FLOW WILL PERSIST DURING THIS TIME IN THE
WAKE OF THE LARGE-SCALE TROUGH AXIS THAT PASSES THROUGH THE REGION
ON MONDAY...AS ANOTHER WEAKER DISTURBANCE PASSES MAINLY JUST NORTH
OF THE LOCAL AREA IN THE WED/WED NITE TIME FRAME. TEMPERATURE
WISE...CONFIDENCE IS FAIRLY HIGH THAT MONDAY REMAINS QUITE COLD
WITH HIGHS ONLY IN THE TEENS MOST AREAS. THEN TUESDAY IS FORECAST
TO CLIMB INTO THE 25-30 RANGE MOST AREAS WITH THE AID OF LOW-LEVEL
WESTERLY FLOW AND SUBSEQUENT WARMING. IN FACT...THE LATEST 00Z
ECMWF SUGGESTS HIGHS COULD BE A BIT WARMER YET...ALTHOUGH THIS
COULD BE TEMPERED BY SNOW COVER FROM THIS WEEKEND. WEDNESDAY COULD
THEN BE A BIT COOLER AND DROPPED A FEW DEGREES FROM PREVIOUS
FORECAST...WITH MOST OF THE AREA TOPPING OUT 23-29. BY THURSDAY A
RETURN TO SOUTHWESTERLY LOW LEVEL FLOW IS THEN PRELIMINARILY
FORECAST TO RESULT IN THE WARMEST DAY THE AREA HAS SEEN IN NEARLY
A WEEK AND A HALF...WITH HIGHS CLIMBING BACK UP INTO THE 30S ALL
AREAS.

&&

.AVIATION...(FOR THE 06Z KGRI TAF THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1149 PM CST THU DEC 5 2013

VFR CONDITIONS ARE EXPECTED WITH LIGHT NORTH WINDS THROUGHOUT THE
TAF VALID PERIOD. THE ONLY CLOUDS EXPECTED WILL BE MID TO HIGH
CLOUDS.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...WIND CHILL ADVISORY UNTIL 10 AM CST THIS MORNING FOR NEZ039>041-
     046>048-060>062.

KS...NONE.
&&

$$

SHORT TERM...WESELY
LONG TERM...PFANNKUCH
AVIATION...WESELY