Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 312130
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
330 PM CST SAT JAN 31 2015

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 330 PM CST SAT JAN 31 2015

...WIDESPREAD SNOW WILL ACCUMULATE TONIGHT ESPECIALLY FROM THE
TRI-CITIES N AND E WITH WINDY BITING COLD TO FOLLOW...

UPDATED AND EXPANDED THE WINTER WX ADVISORY POSTED AT 143 PM TO
INCLUDE ORD/GRAND ISLAND/HASTINGS.

ALOFT: THE FLOW WAS GENERALLY NW WITH A CUT-OFF LOW OVER THE
DESERT SW. THIS LOW HAS DELIVERED THE MOISTURE AND THE LIFT/WAA
WAS OCCURRING IN THE RRQ OF A 140 KT UPR-LVL JET. A SHORTWAVE TROF
WAS ALSO RACING SE FROM THE NRN ROCKIES. THESE DYNAMIC FEATURES
WERE INDUCING CYCLOGENESIS. THIS TROF WILL CONT SE AND CROSS THE
FCST AREA TOMORROW.

SURFACE: WEAK LOW PRES WAS ORGANIZING OVER CO WHILE AN ARCTIC
COLD FRONT WAS SURGING S THRU THE NRN PLAINS. THIS FRONT WILL
SWEEP THRU TONIGHT...WITH THE LOW EJECTING E ALONG IT THRU KS.
ARCTIC HIGH PRES SLIDES INTO THE NRN PLAINS AND BUILDS S.

NOW: SNOW HAS BEEN STEADY FOR MOST AREAS E OF HWY 281. WE HAVE
SEEN REPORTS UP TO 2" ON GRASSY SURFACES S AND E OF THE TRI-
CITIES...BUT MOST LOCATIONS HAVE REMAINED AROUND 1" OR LESS.

RADAR MOSAIC SHOWS A BROAD SHIELD OF PRECIP IN THE WAA E OF
DEVELOPING LOW PRES. THE 700 MB LOW IS CURRENTLY NEAR LBF AND WILL
HEAD E ALONG I-80 TONIGHT. THE 850 MB LOW ALONG THE KS-NEB BORDER.

TONIGHT: EXPECT THE PRECIP SHIELD TO INCREASE IN COVERAGE THRU
THE EVE WITH AREAS W OF HWY 281 GRADUALLY BECOMING INVOLVED. BUT
OVERALL EXPECT A RELATIVE MINIMUM IN PRECIP W OF HWY 281 AND S OF
I-80. IT WONT LAST AS LONG AND NOT AS MUCH ACCUM.

WE WILL SEE A BROAD EVOLUTION TO A FAIRLY COMMA-SHAPED SYSTEM
WITH THE FCST AREA GENERALLY ON THE WRN FRINGE. THIS IS CURRENTLY
UNDERWAY AND IT IS ONE OF THE REASONS THE SW 1/4 OF FCST AREA WILL
SEE RELATIVELY LITTLE.

WHAT YOU CURRENTLY SEE GOING ON OVER THE WRN SANDHILLS AND
PANHANDLE WILL BE THE LAST OF IT AND THAT WILL SLIDE THRU AFTER
MIDNIGHT. THERE WILL PROBABLY BE A BREAK FOR MANY AREAS BETWEEN
THE INITIAL PRECIP SHIELD AND WHEN THIS MOVES THRU.

ARCTIC COLD FRONTAL PASSAGE OCCURS ROUGHLY 9PM-3AM FROM NW-SE AND
THE WINDS WILL CRANK BEHIND IT. THE TOP OF THE BOUNDARY LAYER WILL
HAVE ACCESS TO 35-40 KTS. SO SURFACE WINDS WILL GUST 40-45 MPH AT
TIMES.

TRAVEL: THERE IS A LOT OF WET PAVEMENT AND ANY UNTREATED ROADS
WILL BECOME ICY AS TEMPS DROP BELOW FRZG.

SNOW/QPF: USED NCEP/WPC PRETTY MUCH VERBATIM. THIS BOOSTED
SNOWFALL AMTS REQUIRING EXPANSION OF THE ADVISORY AREA. THE 0.5"
QPF FROM THE LAST 2 GFS/NAM/EC RUNS IS CLUSTERED ALONG HWY 81. THE
09Z SREF PROBABILITIES FOR .5" QPF WERE OVER ERN NEB/KS...BUT 15Z
BACKED WESTWARD TO INCLUDE HWY 81...SUPPORTING OP MODELS.

FOR NOW WE HAVE 3-5" E OF HWY 281 WITH HIGHEST AMOUNTS ALONG HWY
81.

AT THIS POINT CONFIDENCE IS MEDIUM THAT AN ADVISORY WILL HANDLE
THE SNOWFALL FROM OSCEOLA-YORK-GENEVA-HEBRON...BASED ON SNOW
RATIOS BELOW CLIMO /ABOUT 13:1/. THERE IS A CHANCE WE COULD SEE
SOME 6-7" AMTS IN THIS CORRIDOR...WITH THE NEED TO UPGRADE TO A
WARNING. SREF PLUME DIAGRAMS INDICATE SEVERAL MODELS CLUSTERED IN
THIS RANGE WITH A MEAN OF 8" AT HEBRON. SAME AT YORK BUT WITH A
MEAN OF 9". THESE AMOUNTS ARE PROBABLY INFLATED GIVEN TOO MUCH
ACCUM DURING THE DAYTIME HRS.

SUN: COLD SECTOR BEHIND THE DEPARTING LOW. WHATEVER SNOW IS
LEFTOVER AT SUNRISE RAPIDLY DEPARTS TO THE E AND ENDS. N WINDS
CONT TO GUST 40-45 MPH. CLOUDS WILL SLOWLY BEGIN TO BREAK UP OVER
WRN AREAS...BUT EXPECT CLOUDS TO LINGER MOST OF THE DAY ALONG AND
E OF HWY 183.

BITTERLY COLD! WE HAVENT SEEN THIS KIND OF BRUTAL WINTER COLD IN
NEARLY 3 WEEKS. TEMPS WILL FALL THRU THE DAY OVER S-CNTRL NEB AND
HOLD STEADY OVER N-CNTRL KS. WIND CHILLS WILL BE SUB-ZERO OVER MOST
OF S-CNTRL NEB.


.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 330 PM CST SAT JAN 31 2015

GUIDANCE SUGGESTS AN UPPER TROPOSPHERIC SHORT WAVE WILL BE NOTED
OVER THE MID-MISSISSIPPI VALLEY TO START THE LONG-TERM FORECAST
PERIOD AT 00Z MONDAY. THIS SHORT WAVE IS EXPECTED TO QUICKLY MOVE
SOUTHEAST EARLY MONDAY MORNING...THUS ALLOWING FOR NORTHWESTERLY
UPPER TROPOSPHERIC FLOW OVER OUR AREA THROUGH MUCH OF THE LONG-
TERM FORECAST PERIOD. THERE ARE ALSO INDICATIONS FROM THE EC AND
OPERATIONAL GFS OF A SUBTLE UPPER TROPOSPHERIC PERTURBATION MOVING
OVER PORTIONS THE AREA TUESDAY MORNING...AS WELL AS AN UPPER
TROPOSPHERIC SHORT WAVE MOVING OVER THE NORTHERN PLAINS AND UPPER
MISSISSIPPI VALLEY...AND DEPENDING ON WHAT MODEL YOU LOOK AT
PERHAPS PORTIONS OF THE CENTRAL PLAINS...TUESDAY NIGHT INTO
WEDNESDAY.

GUIDANCE SUGGESTS AN OVERALL LACK IN OMEGA SHOULD KEEP US DRY
SUNDAY NIGHT THROUGH MONDAY NIGHT...AND SUCH HAS BEEN PRESENTED IN
THE OFFICIAL FORECAST. GUIDANCE FROM THE EC AND OPERATIONAL GFS
THEN SUGGEST THERE MAY BE JUST ENOUGH OMEGA...IN ASSOCIATION WITH
THE AFOREMENTIONED UPPER TROPOSPHERIC PERTURBATION...FOR
PRECIPITATION PRODUCTION ACROSS OUR EXTREME NORTHEAST TUESDAY
MORNING AFTER SUNRISE. GIVEN THIS...AND AFTER COORDINATION WITH
SURROUNDING OFFICES...OPTED TO GO AHEAD WITH ~20% POPS FOR LIGHT
PRECIPITATION ACROSS OUR NORTHEAST 12-18Z TUESDAY. ANY
PRECIPITATION THAT IS REALIZED WITH THIS PERTURBATION SHOULD BE
VERY LIGHT AND IS CURRENTLY EXPECTED TO PROVIDE LOW-IMPACT...IF
ANY...TO THE AREA.

DIFFERENCES BETWEEN THE OPERATIONAL GFS AND EC PRESENT A TRICKY
FORECAST DURING THE TUESDAY NIGHT THROUGH WEDNESDAY NIGHT TIME
FRAME. THE OPERATIONAL GFS SUGGESTS THE UPPER TROPOSPHERIC SHORT
WAVE WILL MOVE FAR ENOUGH SOUTHWEST TO CLIP THE CENTRAL
PLAINS...INCLUDING OUR AREA...THUS BRINGING PRECIPITATION TO MUCH
OF OUR AREA TUESDAY NIGHT INTO WEDNESDAY. THE EC ON THE OTHER HAND
KEEPS THE UPPER TROPOSPHERIC SHORT WAVE WELL TO OUR NORTHEAST...
MORE OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY...AND
WITH THE PRIMARY AXIS OF OMEGA ALSO REMAINING TO OUR NORTHEAST
SUGGESTS OUR AREA WILL BE DRY TUESDAY NIGHT AND THROUGH PART OF
THE DAY ON WEDNESDAY. THAT SAID...THE EC DOES SUGGEST THE AXIS OF
A ~70KT UPPER TROPOSPHERIC JET STREAK WILL NOSE INTO THE CENTRAL
HIGH PLAINS BY LATE IN THE DAY WEDNESDAY AND CONTINUE WEDNESDAY
NIGHT...WITH THE LEFT-FRONT QUADRANT OF THIS JET STREAK SETTING UP
OVER OUR AREA THUS RESULTING IN PRECIPITATION PRODUCTION ACROSS
MUCH OF OUR AREA STARTING DURING THE DAY WEDNESDAY AND CONTINUING
INTO WEDNESDAY NIGHT. LOTS OF THINGS TO CONSIDER BETWEEN THE TWO
MODELS...BUT THROUGH ONE FORCING MECHANISM OR ANOTHER IT CERTAINLY
APPEARS WEDNESDAY DURING THE DAY SHOWS THE HIGHEST PROBABILITY OF
PRECIPITATION PRODUCTION AND AS A RESULT...POPS AS HIGH AS 40% ARE
IN EXISTENCE ACROSS THE CWA DURING THE DAYTIME WEDNESDAY. REAL
QUESTION IS WHAT TO DO WITH TUESDAY NIGHT AND WEDNESDAY
NIGHT...SIDE WITH THE OPERATIONAL GFS...THE EC...OR BOTH? THE
INHERITED FORECAST ALREADY HAD ~20% POPS IN THE FORECAST FOR
TUESDAY NIGHT AND GIVEN THIS...FEEL IT MUCH MORE PRUDENT TO
PRESENT FORECAST CONSISTENCY AND LET THESE POPS RIDE ACROSS OUR
NORTHWEST...WHICH IS WHERE THE GREATEST OMEGA IS EXPECTED TO
RESIDE THROUGH 12Z WEDNESDAY. TURNING AHEAD TO WEDNESDAY
NIGHT...THE INHERITED FORECAST ONLY HAD ~20% POPS ACROSS OUR
EXTREME SOUTH...AND SEEING AS HOW IT WAS JUST THE LAST COUPLE RUNS
OF THE EC WHICH STARTED SHOWING PRECIPITATION ACROSS MUCH OF THE
CWA...AND AFTER COORDINATION WITH SURROUNDING OFFICES...OPTED TO
KEEP WEDNESDAY NIGHT DRY FOR MOST LOCATIONS WITH THE ONLY
EXCEPTION BEING OUR EXTREME SOUTH. SO...THE CURRENT OFFICIAL
FORECAST SIDES MORE WITH THE OPERATIONAL GFS SOLUTION BY BRINGING
PRECIPITATION IN FROM NORTHWEST TO SOUTHEAST TUESDAY NIGHT INTO
THE DAY WEDNESDAY AND CLEARING PRECIPITATION OUT WEDNESDAY NIGHT
...BUT TRENDS WILL CERTAINLY NEED TO BE MONITORED FOR THE POSSIBLE
ADDITION/EXPANSION OF POPS WEDNESDAY NIGHT SHOULD IT BECOME MORE
LIKELY THE EC SOLUTION MIGHT VERIFY.

THE AFOREMENTIONED DIFFERENCES BETWEEN SETS OF MODEL GUIDANCE
RESULTS IN A LOW-CONFIDENCE FORECAST REGARDING POTENTIAL
PRECIPITATION AMOUNTS AND SNOWFALL ACCUMULATION TUESDAY NIGHT
THROUGH WEDNESDAY...AND THUS IT IS TOO EARLY TO PRESENT POTENTIAL
SNOW AMOUNTS IN THE OFFICIAL FORECAST. THAT SAID...IT IS WORTH
MENTIONING THAT THE OPERATIONAL GFS DOES SUGGEST SNOW ACCUMULATION
OF THREE INCHES OR GREATER COULD BE REALIZED ACROSS PORTIONS OF
THE CWA TUESDAY NIGHT INTO WEDNESDAY AND THUS...THIS IS SOMETHING
TO CLOSELY MONITOR THROUGH THE NEXT SEVERAL DAYS.

AS FOR TEMPERATURE READINGS DURING THE LONG-TERM FORECAST
PERIOD...IT CURRENTLY APPEARS THE ARCTIC AIR MASS WILL REMAIN IN
PLACE THROUGH MONDAY MORNING WITH LOWS GENERALLY IN THE SINGLE
DIGITS. SOUTHERLY RETURN FLOW THROUGH THE BOUNDARY LAYER IS THEN
EXPECTED TO PRESENT WARMER WEATHER LATER IN THE DAY MONDAY AND
INTO TUESDAY...WITH HIGHS RANGING FROM THE UPPER 20S ACROSS OUR
EAST TO THE LOWER 40S ACROSS OUR WEST ON MONDAY...AND HIGHS IN THE
40S AND 50S CURRENTLY EXPECTED ON TUESDAY. THE PASSAGE OF ANOTHER
BOUNDARY- LAYER BAROCLINIC ZONE TUESDAY NIGHT IS THEN EXPECTED TO
BRING ABOUT ANOTHER ROUND COLD AIR...WITH HIGHS BACK INTO THE 20S
ON WEDNESDAY AND LOWS IN THE SINGLE DIGITS THAT NIGHT. GUIDANCE
SUGGESTS THIS SECOND SHOT OF COLD AIR WILL BE SHORT LIVED HOWEVER
AS AFTERNOON HIGHS QUICKLY REBOUND INTO THE 30S FOR MOST LOCATIONS
ON THURSDAY...AND INTO THE 40S AND 50S FOR FRIDAY AND SATURDAY.
LOWS IN THE 20S ARE ALSO CURRENTLY FORECAST TO FINISH THE LONG-
TERM FORECAST PERIOD. IMPORTANT TO NOTE THAT THIS TEMPERATURE
FORECAST HAS A DECENT CHANCE TO BE ADJUSTED DOWNWARD...PENDING ANY
SNOWFALL THAT IS POSSIBLY REALIZED DURING THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z KGRI/KEAR TAFS THROUGH 18Z SUN AFTERNOON)
ISSUED AT 1139 AM CST SAT JAN 31 2015

THIS AFTERNOON: IFR/LIFR STRATUS WILL REMAIN. RADAR SHOWS THE SN
EXITING TO THE E. SO AN EXTENDED PERIOD OF UNRESTRICTED VSBYS WILL
OCCUR. HOWEVER...GUIDANCE INDICATES -SN REDEVELOPING IN THE 21Z-
00Z TIME FRAME. SE WINDS UNDER 10 KTS WILL GRADUALLY BECOME NE.
CONFIDENCE: MEDIUM

TONIGHT: -SN SHOULD SHIFT N/E OF THE TERMINALS BY 04Z LEAVING IFR
STRATUS. ARCTIC COLD FRONTAL PASSAGE WILL OCCUR 07Z-09Z WITH A
DRAMATIC UPSHIFT IN WINDS. ANOTHER PERIOD OF SNOW SHOULD MOVE IN
BEHIND THE FRONT. CIGS MAY LIFT A LITTLE BEHIND THE FRONT
CONFIDENCE: MEDIUM

SUN THRU 18Z: ANY IFR SNOW EXITS TO THE E AND CIGS SHOULD LIFT TO
MVFR. N WINDS CONT TO CRANK...POSSIBLY GUSTING UP TO 40 KTS.
CONFIDENCE: MEDIUM

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY UNTIL NOON CST SUNDAY FOR NEZ039>041-
     047>049-062>064-075>077-086-087.

KS...NONE.
&&

$$

SHORT TERM...HALBLAUB
LONG TERM...BRYANT
AVIATION...HALBLAUB



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