Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 261127
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
527 AM CST THU FEB 26 2015

...BITTERLY COLD AIR HAS RETURNED AND ACCUMULATING/PLOWABLE SNOW
IS LOOKING MORE AND MORE LIKELY THIS WEEKEND...

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 351 AM CST THU FEB 26 2015

ALOFT: A BROAD TROF WAS OVER THE CNTRL USA. IT WILL BROADEN TO
INCLUDE THE ENTIRE CONUS BY DAYBREAK FRI. NO WX-PRODUCING
SHORTWAVE TROFS WILL AFFECT THE FCST AREA.

SURFACE: BITTERLY COLD HIGH PRES WAS DROPPING S OUT OF THE
CANADIAN PRAIRIES. THIS HIGH WILL CONT SLIDING SE AND WILL BE OVER
WRN IA BY 12Z/FRI.

TODAY: BITTERLY COLD. WINDS WILL STILL BE BRISK THIS MORNING WITH
SUB-ZERO WIND CHILLS...AS LOW AS -20F AT TIMES N AND E OF THE TRI-
CITIES THRU MID-MORNING. HIGH TEMPS 15-25F WHICH WILL BE 25F BELOW
NORMAL.

TONIGHT: CONFIDENCE IS LOW IN THE LOW TEMP FCST. LOWS WILL BE
DETERMINED BY WINDS/CLOUDS. MINOR UPSLOPE INTO THE ROCKIES WILL
GENERATE MID-LVL CLOUDS THAT WILL BE OVERTAKING THE FCST AREA FROM
THE SW PER MULTI-MODEL CROSS SECTIONS. IT`S ALSO TOUGH TO
DETERMINE HOW MUCH RADIATING WILL OCCUR FROM THE TRI-CITIES N AND
E.

BOTTOM LINE...LOWS WERE INCREASED ABOVE THE PREVIOUS FCST
ESPECIALLY OVER THE SW 1/3 OF THE FCST AREA.


.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 351 AM CST THU FEB 26 2015

GUIDANCE SUGGESTS QUASI-ZONAL UPPER TROPOSPHERIC FLOW WILL BE
NOTED OVER THE CENTRAL PLAINS TO START THE LONG-TERM FORECAST
PERIOD AT 12Z FRIDAY. THIS NEARLY ZONAL FLOW SHOULD PERSIST
THROUGH THE DAY FRIDAY BEFORE ATTEMPTING TO BECOME MORE
SOUTHWESTERLY AS AN UPPER TROPOSPHERIC TROUGH STRENGTHENS OVER THE
SOUTHWESTERN CONUS. THAT SAID...ANY ATTEMPT BY THE FLOW TO BECOME
SOUTHWESTERLY WILL BE OFFSET SOMEWHAT AS AN UPPER TROPOSPHERIC
SNORT WAVE MOVES SOUTHEAST ACROSS PORTIONS OF THE NORTHERN PLAINS
AND UPPER MISSISSIPPI VALLEY SATURDAY NIGHT INTO SUNDAY. UPPER
TROPOSPHERIC FLOW OVER OUR AREA SHOULD THEN BECOME TRULY
SOUTHWESTERLY ONCE THE SHORT WAVE TROUGH AXIS CLEARS THE UPPER
MISSISSIPPI VALLEY SUNDAY NIGHT...WITH THIS SOUTHWESTERLY FLOW
THEN EXPECTED TO PERSIST THROUGH THE END OF THE FORECAST PERIOD.
AS A RESULT OF ALL THIS...AN ACTIVE LONG-TERM FORECAST PERIOD IS
EXPECTED WITH MULTIPLE CHANCES FOR PRECIPITATION THROUGH THE
MIDDLE PART OF NEXT WEEK.

STARTING WITH WHAT FEW DRY PERIODS WE HAVE...GUIDANCE SUGGESTS AN
OVERALL LACK IN OMEGA WILL PREVENT ANY PRECIPITATION FROM BEING
REALIZED FRIDAY INTO FRIDAY NIGHT...AND SUCH HAS BEEN PRESENTED IN
THE OFFICIAL FORECAST.

PRECIPITATION CHANCES THEN KICK IN BEGINNING DURING THE DAY
SATURDAY AS UPPER TROPOSPHERIC THERMAL ADVECTION INCREASES ACROSS
THE REGION AS THE AFOREMENTIONED SOUTHWESTERN CONUS TROUGH
STRENGTHENS. IN ADDITION...THE NAM...OPERATIONAL GFS AND EC ALL
SUGGEST THE LEFT- FRONT QUADRANT OF AN ~80KT UPPER TROPOSPHERIC
JET STREAK WILL DEVELOP FROM THE CENTRAL HIGH PLAINS INTO OUR
AREA...WITH ENOUGH OF A THERMALLY-INDIRECT CIRCULATION FOR
ADDITIONAL LIFT. QPF FIELDS FROM THE NAM...OPERATIONAL GFS AND EC
ALL RESPOND BY PROVIDING A SOLID BAND OF PRECIPITATION ACROSS MOST
OF KANSAS AND THE SOUTHEASTERN HALF OF NEBRASKA DURING THE DAY
SATURDAY...SATURDAY NIGHT AND INTO THE DAY SUNDAY AS WELL.
PRECIPITATION CHANCES THEN SEEM TO DECREASE SOMEWHAT ACROSS OUR
AREA HEADING INTO SUNDAY NIGHT AS THE PRIMARY AXIS OF ENHANCED
UPPER TROPOSPHERIC FLOW WEAKENS SOMEWHAT...BUT GUIDANCE SUGGESTS
UPPER TROPOSPHERIC THERMAL ADVECTION AND RESULTANT OMEGA AHEAD OF
THE TROUGH AXIS TO OUR WEST WILL REMAIN IN EXISTENCE AND CONTINUE
TO WARRANT POPS THROUGH THE END OF THE LONG-TERM FORECAST PERIOD.

VERY COMPLICATED FORECAST WITH SUCH A PROLONGED PERIOD OF POPS.
FOR THIS FORECAST ISSUANCE...TRIED TO BREAK THE UPCOMING
PRECIPITATION INTO TWO ACTS...THE FIRST BEING SATURDAY THROUGH THE
DAY SUNDAY WHICH IS WHEN FORECAST CONFIDENCE IS HIGHEST. THE
SECOND ACT THEN FOLLOWS SUNDAY NIGHT THROUGH WEDNESDAY WHICH IS
MORE OR LESS A TIME PERIOD OF CONTINUED POPS BUT WILL LIKELY
RESULT IN ON AGAIN / OFF AGAIN PRECIPITATION PRODUCTION FROM DAY
TO DAY.

FOR THE SUNDAY NIGHT THROUGH WEDNESDAY TIME PERIOD...OPTED NOT TO
GET TOO "CUTE" AND PRETTY MUCH LEFT THE SUPERBLEND SOLUTION AS- IS
WITH GENERALLY 20-40% POPS CONTINUING ACROSS THE CWA. FAR TOO
EARLY TO TRY AND PIN DOWN PRECIPITATION AMOUNTS...SO FOR NOW WILL
SIMPLY STATE THAT INCREASED CLOUD COVER WILL ACCOMPANY CHANCES FOR
PRECIPITATION FROM DAY TO DAY.

NOW TURNING OUR ATTENTION BACK TO THE WEEKEND. BASED ON THE
AFOREMENTIONED QPF FIELDS FROM VARIOUS SETS OF GUIDANCE...AS WELL
AS RUN TO RUN CONSISTENCY...IT SEEMS VERY LIKELY THAT WE WILL
OBSERVE PRECIPITATION ACROSS THE CWA...WITH THE GREATEST CHANCES
RESIDING ACROSS OUR SOUTHEASTERN CWA IN CLOSEST PROXIMITY TO THE
ENHANCED UPPER TROPOSPHERIC JET DYNAMICS. GIVEN THIS...THE
"LIKELY" POPS ACROSS OUR SOUTHEAST...AS INHERITED FROM THE DAY-
SHIFT...SEEM RIGHT ON AND IN FACT...OPTED TO RAISE THOSE POPS
ANOTHER ~10%. AS A RESULT...THE CURRENT FORECAST NOW SHOWS 40-70%
POPS ACROSS OUR CWA SATURDAY INTO SATURDAY NIGHT...AGAIN...WITH
THE HIGHEST POPS PLACED ACROSS ROUGHLY THE SOUTHEASTERN HALF OF
THE CWA. A SLIGHT DECREASE IN POPS IS THEN PRESENTED HEADING INTO
SUNDAY...PRETTY MUCH IN THE 20-50% RANGE WHICH "FLOWS" WELL INTO
20-40% POPS WHICH BEGIN SUNDAY NIGHT.

FORECAST PROXIMITY SOUNDINGS FROM ACROSS THE CWA...PER THE NAM...
OPERATIONAL GFS AND EC...SUGGEST A PERSISTENTLY COLD BOUNDARY-
LAYER AIR MASS CONTINUE TO SUPPORT SNOW AS THE PRIMARY
PRECIPITATION TYPE DURING THE LONG-TERM FORECAST PERIOD. ALTHOUGH
THERE ARE SOME INDICATIONS THAT A SLIGHT WARMING TREND ACROSS OUR
SOUTHEAST DURING THE EARLY PART OF NEXT WEEK COULD PROMOTE SOME
RAIN OR A RAIN/SNOW MIX...CONFIDENCE IS NOT HIGH ENOUGH TO DEVIATE
FROM SNOW AS THE PRIMARY PRECIPITATION TYPE AND AS A RESULT...
OPTED TO GO AHEAD WITH SNOWFALL THROUGH THE LONG-TERM FORECAST
PERIOD.

GIVEN ALL THIS...ACCUMULATING SNOWFALL IS LOOKING MORE AND MORE
LIKELY THIS WEEKEND...WITH GUIDANCE FROM THE NAM AND OPERATIONAL
GFS SUGGESTING SNOW-WATER RATIOS ON THE ORDER OF 15-20:1 WILL BE
OBSERVED...AND FOR MANY LOCATIONS WILL LIKELY BE CLOSER TO 20:1.
AS ALREADY MENTIONED...IT REMAINS TOO EARLY TO TRY AND PIN DOWN
PRECIPITATION AMOUNTS BEYOND SUNDAY. FOR THE WEEKEND HOWEVER...
TAKING A BLEND OF THE NAM...OPERATIONAL GFS AND EC PROVIDES LIQUID
PRECIPITATION AMOUNTS OF 0.05-0.15" DURING THE DAY SATURDAY...WITH
ANOTHER 0.01-0.10" SATURDAY NIGHT AND THEN ANOTHER 0.01-0.10"
DURING THE DAY SUNDAY...WITH THE HIGHEST AMOUNTS LOCATED ACROSS
OUR SOUTHEAST. TAKING THESE LIQUID PRECIPITATION AMOUNTS WITH THE
PREVIOUSLY MENTIONED SNOW-WATER RATIOS YIELDS SNOWFALL
ACCUMULATION GENERALLY IN THE 1-4 INCH RANGE...WITH LOCALIZED
AMOUNTS CLOSE TO 5 INCHES ACROSS OUR EXTREME SOUTHEAST.

AT THIS TIME GUIDANCE DOES NOT SUGGEST THE BOUNDARY-LAYER WIND
FIELD WILL BE OVERLY STRONG THROUGH THE WEEKEND...10-15KTS ON
SATURDAY AND THEN DECREASING IN INTENSITY SATURDAY NIGHT INTO
SUNDAY. GIVEN THIS...SIGNIFICANT VISIBILITY RESTRICTION IS NOT
CURRENTLY EXPECTED...THUS MAKING THE SNOWFALL THE PRIMARY HAZARD
THIS WEEKEND.

PREVIOUS ISSUANCES OF THE HWO FEATURED "ACCUMULATING SNOWFALL"
AND "TRAVEL ISSUES" DURING THE WEEKEND AND AT THIS TIME...THAT
MESSAGE STILL APPEARS TO BE RIGHT ON. AGAIN...BECAUSE
PRECIPITATION CHANCES DURING THE LONG-TERM FORECAST PERIOD ARE SO
PROLONGED ITS HARD TO TELL WHEN/WHERE TO PRESENT "BREAK POINT"
BETWEEN THE END OF ONE PERIOD OF SNOWFALL AND THE BEGINNING OF
ANOTHER. AS A RESULT...ITS HARD TO CLEARLY DEFINE HOW MUCH SNOW
GOING TO FALL. BUT BREAKING OUR PROLONGED PERIOD OF SNOWFALL INTO
"TWO ACTS" GIVES US AN OPPORTUNITY TO PROVIDE A MESSAGE TO THE
PUBLIC THAT SUGGESTS LESS THAN IDEAL TRAVEL CONDITIONS WILL LIKELY
BE OBSERVED THIS WEEKEND...AND THAT THE FORECAST NEEDS TO BE
CONTINUALLY MONITORED FOR THE POTENTIAL OF ADDITIONAL SNOWFALL
THROUGH AT LEAST THE MIDDLE PART OF NEXT WEEK. SO...FOR THE
HWO...WILL GO AHEAD AND CONTINUE TO CENTER ATTENTION ON THIS
WEEKEND...BUT WILL ALSO GO AHEAD AND INTRODUCE SNOW AMOUNTS...
GENERALLY IN THE 1-5 INCH RANGE.

&&

.AVIATION...(FOR THE 12Z KGRI/KEAR TAFS THROUGH 12Z FRI MORNING)
ISSUED AT 527 AM CST THU FEB 26 2015

TODAY: A FEW STRATOCU BETWEEN 2500-3500 FT COULD DRIFT THRU UNTIL
15Z...OTHERWISE SKC. N WINDS GRADUALLY DIMINISH AND GUSTINESS
ENDS. CONFIDENCE: HIGH

TONIGHT: VFR SKC. WINDS BECOME LIGHT /UNDER 10 KTS/ FROM THE NE
AND COULD EVENTUALLY TURN CALM AFTER 06Z BEFORE ORGANIZING FROM
THE SE LATE. CONFIDENCE: HIGH

&&

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

$$

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


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