FXUS63 KGID 220459
AFDGID
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1059 PM CST MON DEC 21 2009
.AVIATION...06Z TAF. LOW CLOUDS HAVE ARRIVED AT KGRI...AND NOW
THAT THEY ARE IN PLACE...THEY SHOULD REMAIN AT KGRI THROUGH THE
TAF PERIOD. VISIBILITIES ARE ALSO A CONCERN FROM THE START WTIH
SOME SPOTS IN THE LOW CLOUDS FALLING TO AROUND A MILE OR
BELOW...BUT OTHER LOCATIONS SUCH AS KODX AND KLXN HAVE SO FAR
MANAGED TO NOT FALL HARDLY AT ALL. KGRI HAS JUST FALLEN TO AROUND
1SM...AND WILL KEEP THEM AROUND THAT FOR A FEW HOURS...BUT WILL
TRY TO IMPROVE THEM A BIT LATER THIS MORNING WHICH HAS SEEMED TO
BE THE TREND FOR OTHER LOCATIONS. FREEZING DRIZZLE IS ANOTHER
ISSUE TO DEAL WITH...AND CONFIDENCE IN WHEN THE DRIZZLE WILL
ARRIVE AT KGRI IS NOT VERY HIGH. FOR NOW OPTED TO KEEP IT OUT OF
THE FOREAST UNTIL THE BETTER ISENTROPIC LIFT ARRIVES ON TUESDAY
AFTERNOON.
&&
.PREV DISCUSSION... /ISSUED 347 PM CST MON DEC 21 2009/
SHORT TERM...TONIGHT THROUGH TOMORROW. VERY LITTLE GOING ON THIS
AFTERNOON...AS A DECK OF MID LEVEL CLOUDS WITH A FEW SPRINKLES IS
STEADILY EXITING SOUTH CENTRAL NEBRASKA AND NORTH CENTRAL KANSAS
FROM WEST TO EAST AS A WEAK MID LEVEL WAVE MOVES THROUGH THE
QUASI-ZONAL FLOW. AS SKIES HAVE CLEARED...WESTERN AREAS HAVE WARMED
NICELY INTO THE LOW OR MID 40S...WITH FAR SOUTHWEST AREAS NEAR 50.
BREEZES HAVE BEEN SOUTHERLY IN THE WAKE OF A DEPARTING RIDGE AXIS
AND AHEAD OF AN ADVANCING TROUGH AXIS ACROSS WESTERN NEBRASKA.
THIS EVENING...SKIES WILL START OUT MOSTLY CLEAR...BUT AS A COLD
FRONT OOZES SOUTH ACROSS THE AREA LATER TONIGHT AN AREA OF LOW
CLOUDS CURRENTLY DROPPING INTO FAR NORTHERN NEBRASKA OUT OF SOUTH
DAKOTA WILL OVERTAKE THE CWA FROM NORTH TO SOUTH. WITH SUBSTANTIAL
DRY AIR IN THE MID LEVELS ABOVE THE LOW LEVEL SATURATED
LAYER...PATCHY AREAS OF FREEZING DRIZZLE ARE LIKELY TO DEVELOP
NORTH OF INTERSTATE 80 AFTER MIDNIGHT. ANY ICE ACCUMULATION
SHOULD BE MINIMAL WITH LITTLE IMPACT. THERE IS ALSO A LIKELIHOOD
OF AT LEAST PATCHY FOG DEVELOPMENT TONIGHT...WHICH COULD BECOME A
BIT MORE WIDESPREAD THAN CURRENTLY ADVERTISED IF SKIES REMAIN
CLEAR FOR SEVERAL HOURS BEFORE THE STRATUS ARRIVES. LOW
TEMPERATURES TONIGHT WILL SETTLE IN THE LOW-MID 20S MOST AREAS.
DURING THE DAY TOMORROW...WIDESPREAD LOW CLOUDS WILL REMAIN
ENTRENCHED ACROSS THE AREA...AS THE MID LEVELS AND DENDRITIC LAYER
REMAIN UNSATURATED. THIS WILL RESULT IN CONTINUED AREAS OF LIGHT
FREEZING DRIZZLE...PRIMARILY ACROSS THE NORTHEAST 2/3 OF THE CWA.
ACROSS THE SOUTHWEST 8 OR SO COUNTIES...AFTERNOON TEMPERATURES
COULD NUDGE JUST ABOVE FREEZING...RESULTING IN ONLY LIGHT DRIZZLE.
ALTHOUGH THERE COULD BE A FEW SLICK SPOTS FROM ANY FREEZING
DRIZZLE TOMORROW...THIS PRECIPITATION WILL BE HARD PRESSED TO
MEASURE...AND DO NOT ANTICIPATE ANY WIDESPREAD TRAVEL IMPACTS.
HIGH TEMPERATURES TOMORROW WILL ONLY CLIMB TO BETWEEN 28-32
DEGREES ACROSS MOST OF THE CWA.
LONG TERM...BEGINNING TUESDAY NIGHT. A MAJOR WINTER STORM
CONTINUES TO TARGET THE CENTRAL PLAINS MID WEEK ON...INCLUDING THE
FIRST PART OF CHRISTMAS DAY AS MODELS HAVE BEGUN TO SLOW/DEEPEN
THE SYSTEM TOWARD THE END OF THE WEEK. A POTENT UPPER LOW PRESSURE
SYSTEM CURRENTLY ALONG THE COAST OF BRITISH COLUMBIA IS FAIRLY
CONSISTENTLY FORECAST BY MODELS TO DEEPEN NEAR THE FOUR CORNERS
REGION ON TUESDAY...TRACK EAST ACROSS OKLAHOMA/SOUTHERN KANSAS
WEDNESDAY...THEN LIFT NORTH THROUGH WESTERN MISSOURI THURSDAY ON
INTO SOUTHWEST IOWA/NW MISSOURI FRIDAY MORNING. THE TIMING OF THE
SYSTEM HAS SLOWED WITH THE UPPER LOW NOW PROGGED TO DEPART INTO
EASTERN IOWA LATER ON FRIDAY.
AS THE SYSTEM IS JUST REACHING LANDFALL...WE WILL SEE HOW MODELS
HANDLE THE SYSTEM IN THE NEXT COUPLE OF RUNS. THE 12Z ECMWF HAS
ARRIVED WITH SOME THERMAL DIFFERENCES/WARMER MID LEVEL TEMPERATURES
THAN THE PREVIOUS 00Z RUN WHICH WAS MORE SIMILAR TO THE 12Z GFS.
FOR NOW HAVE OPTED TO NOT FLIP FLOP TO THE WARMER ECMWF RUN WHICH
WOULD BRING THE CURRENT FORECAST RAIN LINE FARTHER NORTH AND THE
ICE/MIXED PCPN FARTHER NORTH AS WELL.
AS IT STANDS ATTM...ISENTROPIC LIFT AS INDICATED ON THE 300K SURFACE
INCREASES TUESDAY NIGHT...ESPECIALLY AFTER MIDNIGHT AS THE FOUR
CORNERS H7 LOW DEEPENS AND EDGES EASTWARD. FORECAST SOUNDINGS
GRADUALLY SATURATE THE DENDRITIC LAYER ACROSS THE NORTHERN TWO
THIRDS OF OUR CWA BY MORNING SO INITIALLY PCPN TYPE SHOULD BE
FREEZING DRIZZLE...WHICH SHOULD THEN CHANGE TO SNOW BY WEDNESDAY
MORNING. ACROSS FAR SOUTHERN NEBRASKA AND NORTH CENTRAL
KANSAS...THE DENDRITIC LAYER IS EVEN SLOWER TO SATURATE AND KEPT
PCPN TYPE AS A WINTRY MIX OF FREEZING RAIN OR SLEET.
ON WEDNESDAY...AGAIN PERIODS OF ISENTROPIC LIFT CONTINUE DURING THE
DAY AND WE SHOULD CONTINUE TO SEE SOME INTERMITTENT PCPN OR SOME
PCPN BANDS SETTING UP. THE THERMAL PROFILE ACROSS OUR FAR SOUTHEAST
CWA IS WARM ENOUGH FOR A RAIN EVENT...WITH MORE OF A MIX EXPECTED
INTO NEBRASKA AS DENDRITIC MOISTURE IS INTERMITTENT AT TIMES WITH
THE PCPN BANDS. OUR FAR NORTH SHOULD REMAIN AS ALL SNOW. SNOW
ACCUMULATIONS WEDNESDAY MAY REACH 1 TO 4 INCHES WITH THE HIGHER
AMOUNTS IN NEBRASKA. AGAIN WILL NEED TO CONTINUE TO KEEP AN EYE ON
THE THERMAL PROFILE WITH THE EC SHOWING SOME WARMING TRENDS WHICH
WOULD ALTER PCPN TYPE AND SNOWFALL AMOUNTS.
BY WEDNESDAY NIGHT AS THE UPPER LOW MOVES ACROSS THE SOUTHERN
PLAINS...THE SURFACE LOW DEEPENS IN EASTERN KANSAS. WINDS WILL
INCREASE FROM THE NORTH TO 25 TO 35 MPH AND GUST WELL OVER 40 MPH.
THE SURFACE GRADIENT REMAINS TIGHT THROUGH FRIDAY LEADING TO A
PROLONGED PERIOD OF HIGH WINDS. AS THE UPPER LOW LIFTS NORTH...THE
DEFORMATION AND WRAPAROUND PCPN SHIFT ACROSS CENTRAL AND EASTERN
NEB/KS AND SIGNIFICANT SNOWFALL ACCUMULATIONS ARE EXPECTED. THE
SNOWFALL COMBINED WITH THE HIGH WINDS MAY RESULT IN WHITE OUT OR
BLIZZARD CONDITIONS AND WILL UPGRADE OUR CURRENT WINTER STORM WATCH
TO A BLIZZARD WATCH FROM 06Z THURS TIL 18Z FRIDAY. THE SNOW SHOULD
COME TO AN END SOMETIME ON FRIDAY. HAVE RANGED PRELIMINARY SNOWFALL
TOTALS FROM AROUND 9 TO 10 INCHES ACROSS NC KANSAS OUR WESTERN NEB
COUNTIES...TO AMOUNTS OF 12 TO 14 INCHES ACROSS OUR EASTERN NEB
ZONES.
HAVE WENT WITH DRY CONDITIONS FOR FRIDAY NIGHT BUT IF MODELS SLOW
FURTHER...MAY NEED TO INCLUDE SOME LIGHT SNOW POTENTIAL. THE
FORECAST REMAINS DRY ON SATURDAY WITH COLD TEMPS FOLLOWING THE STORM.
LOOKING BEYOND THE WINTER STORM TO SUNDAY AND MONDAY...LITTLE
CHANGE TO HPC FORECAST WITH DRY WEATHER AS RIDGING BUILDS IN
BEHIND THE DEPARTING SYSTEM. THE 12Z GFS DEPICTS ANOTHER WAVE
ZIPPING ACROSS THE SOUTHERN PLAINS AS EARLY AS MONDAY WITH A
CHANCE FOR LIGHT SNOW INTO PARTS OF THE CWA...BUT THE 12Z ECMWF
IS SLOWER AND WEAKER WITH THIS FEATURE...AND ANY IMPACT FROM THIS
WAVE WOULD LIKELY BE DELAYED UNTIL TUESDAY. THERE WILL BE PLENTY
OF TIME TO LOOK AT THIS IN THE COMING DAYS...CONSIDERING ALL OF
THE ISSUES BETWEEN NOW AND THEN. HIGHS SUNDAY AND MONDAY LOOK TO
BE IN THE 20S...WITH LOWS IN THE SINGLE DIGITS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...BLIZZARD WATCH FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY MORNING
FOR NEZ039>041-046>049-060>064-072>077-082>087.
WINTER STORM WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY
EVENING FOR NEZ039>041-046>049-060>064-072>077-082>087.
KS...BLIZZARD WATCH FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY MORNING
FOR KSZ005>007-017>019.
WINTER STORM WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY
EVENING FOR KSZ005>007-017>019.
&&
$$
