FXUS63 KGID 052346 AAA
AFDGID
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HASTINGS NE
546 PM CST SAT DEC 5 2009
.AVIATION...FOR THE 00Z KGRI TAF. CHALLENGING AVIATION FORECAST
EXPECTED FOR THE LATTER HALF OF THE PERIOD AS A SMALL BUT POTENT
UPPER DISTURBANCE SLIDES THROUGH THE REGION. INITIALLY FOR
TONIGHT...A BROKEN MID TO HIGH CEILING WILL GRADUALLY LOWER
THROUGH THE NIGHT BUT REMAIN IN A VFR RANGE. NORTH WINDS WILL
INCREASE SLOWLY DURING THIS TIME PERIOD IN RESPONSE TO A DEEPENING
AREA OF LOW PRESSURE ACROSS THE HIGH PLAINS BUT LOOK TO REMAIN
UNDER 12-15 KNOTS. CONDITIONS THEN BEGIN TO TAKE A NOSE DIVE ON
SUNDAY WITH CEILINGS THE FIRST TO GO DURING THE MORNING HOURS AS
THEY LOWER QUICKLY TO AROUND 1-2 KFT AGL. DEEP LIFT THEN ARRIVES
WITH THE UPPER DISTURBANCE DURING THE AFTERNOON HOURS WITH THE
THREAT FOR LIGHT SNOW APPEARING BY EARLY TO MID AFTERNOON.
&&
.PREV DISCUSSION... /ISSUED 313 PM CST SAT DEC 5 2009/
SHORT TERM...TONIGHT THROUGH MONDAY MORNING. MAIN CONCERN THIS
TIME FRAME CONTINUES TO BE CHANCE FOR SNOW ON SUNDAY.
CURRENT WATER VAPOR IMAGERY AND WIND PROFILER DATA SHOWS ONE UPPER
LOW SPINNING OVER THE NORTHERN GREAT LAKES AND A SECOND LOW DIGGING
SOUTH ALONG THE ROCKIES AND CURRENTLY OVER SOUTHERN IDAHO. PROFILER
NETWORK CURRENTLY DEPICTING A 300 MB JET OF 100 KTS OVER NORTHERN
NEB. VISIBLE IMAGERY SHOWS CLEAR SKIES OVER MUCH OF NEB WITH HIGHER
CLOUDS STREAMING ACROSS KS. SURFACE LOW PRESSURE CONTINUES TO
SLOWLY PUSH ACROSS THE CWA WITH NW WINDS NOW ACROSS THE WESTERN HALF
OF THE CWA AND SW IN THE EASTERN HALF.
MODELS IN GOOD AGREEMENT WITH FIRST SHORTWAVE TROUGH EJECTING OUT
FROM THE WESTERN LOW AND INTO OUR CWA ON SUNDAY. WILL HAVE SOME JET
DYNAMIC HELP HAS WE WILL SIT BETWEEN THE RIGHT ENTRANCE AND LEFT
EXIT REGIONS FOR A WHILE ON SUNDAY. 500-300 MB Q VECTORS SHOW BROAD
SCALE LIFT BEGINNING MID MORNING SUNDAY AND CONTINUING INTO SUNDAY
EVENING BEFORE WAVE MOVES EAST SUNDAY OVERNIGHT. SPEED OF SYSTEM
STILL LOOKS FAST ENOUGH TO KEEP US FROM GETTING DUMPED ON. SHOULD
BE MORE OF A FLUFFY SNOW WITH COBB METHOD SHOWING A 15 OR 20 TO 1
RATIO AND ROEBBER METHOD CONFIRMING THIS. PREVIOUS THINKING OF 1 TO
3 INCH SNOW STILL SEEMS ON TRACK WITH HIGHER AMOUNTS IN THE NORTH OF
HIGHWAY 6 IN THE EAST. ONLY CHANGE I WILL MAKE IS TO PUSH BACK
TIMING JUST A LITTLE WITH LIGHT SNOW STARING IN THE WEST AROUND 9 AM
SUNDAY AND ENDING BETWEEN 9 PM AND MIDNIGHT IN THE EAST.
ONE OTHER CONCERN IS THE POSSIBILITY OF FREEZING DRIZZLE IN THE
SOUTHERN PART OF THE CWA SUNDAY MORNING. BOTH NAM AND GFS HAVE A DRY
LAYER FROM 750 TO 500 MB WITH PROFILE SATURATED BELOW THAT. HOWEVER
TEMPS LOOK TO BE FROM -6 TO -9C SO TOUGH TO SAY IF WE DO GET PRECIP
THERE IN THE MORNING WHETHER IT WILL BE FREEZING DRIZZLE...OR SOME
LIGHT SNOW. FOR NOW WILL KEEP LIGHT SNOW GOING AND LET LATER SHIFTS
ADJUST IF NEED BE.
LONG TERM...12Z MONDAY THROUGH SATURDAY. BIGGEST FORECAST CHALLENGE
CONTINUES TO BE SNOW AMOUNTS FOR MONDAY NIGHT THROUGH TUESDAY NIGHT
ASSOCIATED WITH A POTENT WAVE MOVING THROUGH.
FOR MONDAY...WE SHOULD GET A LULL IN ACTIVITY WITH SHORTWAVE RIDGING
MONDAY MORNING...BUT IT WILL NOT TAKE LONG FOR ISENTROPIC LIFT TO
START PRODUCING SOME LIGHT SNOWFALL/FLURRY ACTIVITY...ESPECIALLY IN
THE SOUTHWESTERN CWA BY LATE AFTERNOON. THIS SHOWS UP WELL ON THE
275 K LEVEL. ISENTROPIC LIFT AND MOISTURE INCREASE SIGNIFICANTLY
MONDAY NIGHT
MONDAY NIGHT THROUGH TUESDAY NIGHT...GOOD INSENTROPIC LIFT OCCURS AT
THE 275/280K LEVEL MONDAY NIGHT. THERE IS WIDESPREAD AGREEMENT AMONG
MODELS THAT THIS WILL OCCUR...AND WITH COLD TEMPERATURES LENDING TO
HIGHER SNOW RATIOS...WE COULD PICK UP A GOOD 2 TO 4 INCHES FROM
MONDAY NIGHT ALONE. MODELS ADVERTISE STRONG ISENTROPIC LIFT TUESDAY
MORNING INTO EARLY AFTERNOON BEFORE MODERATE TO STRONG SYNOPTIC LIFT
TAKES OVER LATER IN THE AFTERNOON INTO THE EVENING. THERE IS
WIDESPREAD AGREEMENT AND CONSISTENCY AMONG MODELS THAT A CLOSED 700
MB LOW WILL CROSS TO THE EAST NOT TOO FAR FROM THE STATE LINE. I
GENERALLY INCREASED SNOW AMOUNTS A COUPLE OF INCHES IN THE SOUTH AS
MODELS CONTINUE TO FIRM THEIR STANCE ON HIGHER QPF AMOUNTS TO THE
SOUTH. DIFFICULT TO TELL WHERE EXACTLY THE BEST FRONTOGENETIC BAND
OR BANDS WILL SET UP ON TUESDAY...BUT IT GENERALLY LOOKS LIKE
CHANCES ARE BETTER TO THE SOUTH. PUSHED TOTAL SNOW AMOUNTS UP TO
ABOUT 10 INCHES IN OUR SOUTHEAST. STRONG NORTH WIND LOOKS LIKE A
GOOD BET ON THE BACKSIDE OF THE SURFACE LOW...ALTHOUGH MODELS HAVE
TRENDED A BIT FARTHER SOUTH WITH THIS LOW...THUS I EASED OFF WIND
SPEEDS FROM YESTERDAY BY A COUPLE OF MPH.
FOR TEMPERATURES...I GENERALLY WENT BELOW GUIDANCE VALUES...AND WENT
REALLY COLD FOR WEDNESDAY WITH HIGHS STRUGGLING TO MAKE TEENS WITH
FRESH SNOW PACK AND COLD 850 MB TEMPERATURES...AND THURSDAY MORNING
NEAR ZERO AS THE CENTER OF THE SURFACE HIGH WILL BE NEARBY.
TEMPERATURES WILL CONTINUE TO BE ANOMALOUSLY COLD FOR THE ENTIRE
LONG TERM PERIOD.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
