Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 242244
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
444 PM CST WED DEC 24 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 221 PM CST WED DEC 24 2014

MOSTLY SUNNY SKIES HAVE OVERTAKEN THE REGION THIS AFTERNOON AS A
SURFACE RIDGE PASSING ACROSS THE CENTRAL PLAINS HAS HELPED TO
SHIFT THE LOW LEVEL STRATUS TO OUR EAST. IN THE WAKE OF THIS
STRATUS...TEMPERATURES HAVE CLIMBED INTO THE MIDDLE TO UPPER 30S
AND EVEN LOWER 40S IN SPOTS. THANKS TO THIS RIDGE...WINDS HAVE
ALSO DECREASED SIGNIFICANTLY FROM YESTERDAY...AS THE PRESSURE
GRADIENT HAS RELAXED ACROSS THE REGION.

WITH MAINLY CLOUD FREE SKIES AND LIGHT WINDS EXPECTED TO CONTINUE
ACROSS THE REGION OVERNIGHT...OPTED TO SIDE WITH COOLER GUIDANCE
FOR OVERNIGHT LOWS...AS ALBEIT THE WIND DIRECTION WILL BE
SHIFTING AND BECOMING MORE SOUTHERLY...WINDS IN GENERAL WILL BE
LIGHT WITH A SOMEWHAT FAVORABLE RADIATIVE COOLING CONDITIONS
FORECAST. THE OTHER MAIN FACTOR FOR NOT GOING EVEN LOWER ON
TEMPERATURES OVERNIGHT IS THE EXPECTED INCREASING CIRRUS
SHIELD...WHICH CAN BE SEEN AHEAD OF THE NEXT SYSTEM ALREADY
SPILLING OVER THE ROCKIES...AND MAY ALSO HELP KEEP LOWS UP A
DEGREE OR TWO.

FOR CHRISTMAS DAY...DRY AND QUIET WEATHER CONDITIONS ARE EXPECTED
TO CONTINUE ACROSS THE REGION WITH MAINLY HIGH LEVEL CLOUDS
FORECAST TO STREAM ACROSS THE REGION AHEAD OF THE NEXT STORM SYSTEM.
WITH THE ACTUAL COLD FRONT NOT EXPECTED TO CROSS THE FORECAST
AREA UNTIL THE EVENING OR OVERNIGHT HOURS CHRISTMAS DAY...EXPECT
TEMPERATURES TO PEAK A FEW DEGREES WARMER THAN THIS AFTERNOONS
READINGS AHEAD OF THE FRONT...AND WENT AHEAD AND INCREASED
TEMPERATURES A COUPLE OF DEGREES INTO THE LOWER TO MIDDLE 40S
TOMORROW AFTERNOON. OVERALL...QUIET AND SEASONABLY WARM WEATHER IS
ANTICIPATED FOR THE NEXT 24 HOURS.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 221 PM CST WED DEC 24 2014

A MAJOR BLAST OF ARCTIC AIR WILL ARRIVE NEXT WEEK TO CLOSE 2014
AND START 2015 ON A BITTERLY COLD NOTE.

PATTERN: MULTI-DAY 500 MB MEAN HEIGHT ANOMALIES FROM THE EC/GFS
ENSEMBLE MEANS CONT IN GOOD AGREEMENT ON A LONGWAVE RIDGE FROM THE
NE PAC INTO AK WITH A DOWNSTREAM TROF OVER N AMERICA THE NEXT 10
DAYS. THIS PATTERN IS IDEAL FOR UNLOADING FRIGID ARCTIC AIR DEEP
INTO THE USA. SO WE HAVE HIGH CONFIDENCE THAT A MAJOR COLD BLAST IS
COMING IN THE 12/30-1/1 TIME FRAME. THE MAIN QUESTION IS HOW LONG
IT LASTS AND THE ENSEMBLES ARE NOT IN AGREEMENT ON THAT. THE GFS
ENSEMBLE MEAN KEEPS THE PETAL DOWN WHILE THE EC/GEM MEANS EASE OFF
THE COLD THE 1ST WEEK OF JAN.

ALOFT: A POTENT SHORTWAVE TROF WILL BE OVER THE 4-CORNERS REGION
CHRISTMAS NIGHT. THE MAIN VORT MAX WILL CROSS KS/NEB FRI NIGHT. A
BROAD/FLAT TROF WILL REMAIN SAT-SUN AS THE NEXT SHORTWAVE TROF
DIVES INTO THE NRN ROCKIES. THIS TROF WILL DIG AND REAMPLIFY THE
LONGWAVE TROF MON-WED WITH NW FLOW DEVELOPING. THERE WILL BE A
PERIOD IN WHICH SEVERAL LOW-AMPLITUDE SHORTWAVE TROFS ARE EMBEDDED
IN THE FLOW. THEY WILL RESULT IN PERIODIC FLURRIES OR A LITTLE
LIGHT SNOW...BUT OVERALL WILL BE OF MINIMAL CONSEQUENCE.

SUGGEST READING THE MODEL DIAGNOSTIC DISCUSSION /PMDHMD/ FROM WPC
FOR EVALUATION OF THE MODELS. BOTTOM LINE IS THE TREND IS FOR A
SLOWER TROF COMING OUT OF THE 4-CORNERS. SPAGHETTI PLOTS AT 00Z/SAT
SHOW THE NAM/GFS/SREF MEAN ARE ALL ON THE FAST END OF THE GUIDANCE
SPREAD. WPC PREFERENCE IS FOR THE 12Z EC WHICH IS NOT AS SLOW AS THE
UKMET/GEM BUT NOT AS FAST AS THE GFS/NAM.

SURFACE: THE COLD FRONT WILL CLEAR THE FCST AREA THU NIGHT WITH THE
LEE-SIDE LOW FILLING AS IT TRACKS UP THE FRONT INTO IA BY DAYBREAK
FRI. CANADIAN HIGH PRES WILL SLIDE DOWN THE FRONT RANGE AND BE
OVERHEAD SAT. MEANWHILE...A WEAK CLIPPER WILL ORGANIZE OVER ALBERTA
AND THEN HEAD SE SUN-MON. THIS IS THE SYSTEM THAT WILL DELIVER THE
ARCTIC AIR WITH A COLD FRONTAL PASSAGE SUN NIGHT OR MON. EARLIER IN
THE WEEK THE GFS WAS ADVERTISING A 1055 MB ARCTIC HIGH COMING DOWN.
NOW THE EC HAS 1050 MB. THIS HIGH WILL GRADUALLY BUILD S AND BE
OVERHEAD WED.

THE DAILY DETAILS...

FRI: COLD SECTOR. A BROAD AREA OF LIGHT SNOW WILL OVERTAKE THE AREA
AS THE SHEARED +TILT SHORTWAVE TROF MOVES THRU. THIS LOOKS LIKE A
MINOR EVENT AND SUGGEST STAYING AWAY FROM STRONGER NAM FOR NOW.

THIS SNOW EVENT IS FAR FROM NAILED DOWN. DUE TO MODEL UNCERTAINTY...
USED WPC QPF WHICH FAVORED THE SOMEWHAT SLOWER 12Z EC AND LIGHTER
AMOUNTS.

QPF: THE LAST 4 SREF CYCLES HAVE TRENDED HIGHER WITH THE
PROBABILITIES OF .10" IN 24 HRS...WITH THE PROBS JUST NW OF THE FCST
AREA...FROM IMPERIAL-O`NEILL. THE 06Z/12Z NAM PAINT A NARROW SWATH
OF .25-.40 OVER THE NW HALF OF THE FCST AREA...SOUTH OF THE SREF
MEANS. THE 18Z RUN CAME IN WITH UP TO .30 FROM LEXINGTON-ORD.
HOWEVER...WPC PREFERENCE WAS TO LEAN AWAY FROM THE THE MORE POTENT
NAM. I MENTION THIS SOLELY TO CONVEY THE MAGNITUDE OF THE SPREAD AND
THE POTENTIAL FOR EMBEDDED MESOSCALE UNCERTAINTY IN HOW THIS EVENT
COULD UNFOLD.

FOR NOW THE HWO HAS OUR THINKING. 1 TO POSSIBLY 2" NW OF A LINE FROM
BEAVER CITY-GRAND ISLAND-FULLERTON. SOME ADJUSTMENTS WILL BE MADE TO
THIS AS FRI DRAWS NEARER.

SAT: CLEARING WITH LIGHT WINDS. HAVE A FEELING WE COULD BE TOO COLD
ON HIGH TEMPS BY 3-5F.

SUN: INCREASING MID-HIGH CLOUDS ESPECIALLY AFTERNOON.

SUN NIGHT OR MON: COLD FRONTAL PASSAGE AND IT COULD BE ACCOMPANIED
BY SCATTERED SNOW SHWRS OR FLURRIES. BLUSTERY AND COLDER.

TUE: BLUSTERY AND FRIGID. HIGH TEMPS IN THE TEENS APPEAR PROBABLE.
STILL COULD SEE SOME FLURRIES OR A FEW SNOW SHWRS.

WED: CONTINUED BITTER COLD BUT WITH LESS WIND.

&&

.AVIATION...(FOR THE 00Z KGRI/KEAR TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 440 PM CST WED DEC 24 2014

VFR CONDITIONS ARE FORECAST AS HIGH PRESSURE PREVAILS OVER THE
HIGH PLAINS.

&&

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

$$

SHORT TERM...ROSSI
LONG TERM...HALBLAUB
AVIATION...HEINLEIN


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