FXUS63 KOAX 090407
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1007 PM CST TUE DEC 8 2009
.DISCUSSION...
GOING FORECAST IN GOOD SHAPE TONIGHT AND ONLY UPDATES WERE TO
REPLACE THE WNTR STRM WRNG WITH THE SCHEDULED BLIZZARD WRNG. 991 MB
SFC LO NOW IN NE MO WL CONT TO WORK NEWD THRU THE NIGHT. PRES IS
STARTING TO INCREASE OVR THE FA AND SHLD QUICKLY INCREASE OVERNIGHT
WITH 8-9 MB RISES BY LATE TONIGHT. STG LO LVL CAA IS OCCURRING FM
THE NW...AND THIS COMBINED WITH THE PRES RISES SHLD ALLOW FOR STG
WIND GUSTS OVERNIGHT. LATEST RUC BUFFER DATA INDCS 50 KT WINDS AT
THE TOP OF THE MIXED LAYER AND THIS SHLD LEAD TO GUSTS UP TO 40 KT
BY LATE TONIGHT. ALTHOUGH THE HEAVIEST OF THE SNOW IS WINDING DOWN
WITH THE BEST PRES ADVECTION ON THE 1.5 PVU SFC SHIFTING EWD INTO
IA...SHLD SEE SOME -SN CONT THRU THE NIGHT AS AT LEAST LARGE-SCALE
FORCING FOR ASCENT CONTS OVR THE CWA. ACCUM SN IS PRETTY MUCH OVR IN
THE NW AND THE SW....BUT THE BNSN WL CONT. ADDITIONAL ACCUM WL
GENERALLY BE LESS THAN 2 INCHES AND MAINLY OVR SW IA.
NEW ZFP/WSW/GRIDS HAVE BEEN SENT.
BOUSTEAD
&&
.PREV DISCUSSION... /ISSUED 312 PM CST TUE DEC 8 2009/
SHORT TERM...TONIGHT THROUGH FRIDAY.
POTENT WINTER STORM IS ONGOING ACROSS THE PLAINS THIS AFTERNOON.
MAIN UPPER SYSTEM WAS DIGGING THROUGH NEW MEXICO INTO THE TEXAS
PANHANDLE...INDUCING SURFACE CYCLOGENESIS ACROSS MUCH OF THE
SOUTHERN PLAINS. BROAD 6 TO 9MB 3-HOUR PRESSURE FALLS WERE NOTED
FROM THE TEXAS PANHANDLE NORTHEAST THROUGH MISSOURI AND ILLINOIS.
SHORT TERM RUC INDICATES LOW FORMING OVER SOUTHWEST MISSOURI WILL
BECOME DOMINANT FEATURE BY EARLY EVENING...AND WAS POINTING TO
LOWER PRESSURES THAN 12Z NAM/GFS MODELS. MAIN IMPACTS HERE DUE TO
THOSE LOWER PRESSURES WILL BE INCREASE IN POTENTIAL WIND SPEEDS AS
THE LOW STARTS MOVING OUT...AND ADDITIONAL MOISTURE FROM THE
SOUTHERN PLAINS AND THE MISSISSIPPI VALLEY WRAPPING AROUND THE
LOW BACK ACROSS SOUTHERN IOWA INTO OUR CWA...WHICH WOULD SUGGEST
SLIGHTLY HIGHER SNOW TOTALS THAN PREVIOUS FORECASTS. ALSO TO
NOTE...CONVECTIVE-LOOKING CLOUDS ACROSS NORTHEAST TO SOUTH CENTRAL
KANSAS WERE ROTATING NORTHEAST TOWARD SOUTHEAST NEBRASKA THIS
AFTERNOON...SUGGESTING MID LEVEL INSTABILITY WILL IMPACT THE
SOUTHERN PART OF OUR CWA WITH MORE INTENSE BANDS OF SNOW. CROSS
SECTIONS FROM RUC/NAM ALSO SHOW THIS INSTABILITY IN THE 700-500MB
LAYER OWING TO NEGATIVE EQUIVALENT POTENTIAL VORTICITY. WIND
POTENTIAL IS OF CONCERN AS WELL. 12Z MODELS WERE PAINTING 25KT
SUSTAINED WINDS ACROSS THE CWA BY MIDNIGHT...BUT LOWER PRESSURES
TO OUR EAST WILL INCREASE PRESSURE GRADIENT MORE THAN MODEL
FORECASTS. THUS EXPECT 30+ SUSTAINED WINDS WITH GUSTS OVER 40 MPH
AS WE HEAD TOWARD MIDNIGHT. SO...WITH CONTINUED SNOW DURING THE
EVENING AND WINDS INCREASING ABOVE 30 MPH...HAVE UPGRADED OUR
WINTER STORM WARNING TO A BLIZZARD WARNING FOR ALL THE CWA.
HAVE ALREADY RECEIVED REPORTS OF ROAD CREWS HAVING A DIFFICULT
TIME KEEPING ROADS OPEN IN PARTS OF SOUTHEAST NEBRASKA...AND THE
STRONG WINDS HAVE NOT HIT THEM YET.
SNOW AMOUNTS WILL BE VERY TRICKY TO DEDUCE GIVEN STRONG WINDS. BUT
ALREADY GETTING REPORTS OF 6 TO 8 INCHES OVER OUR SOUTHERN
CWA...WITH 4 IN THE FAR NORTHWEST. AM EXPECTING ADDITIONAL AMOUNTS
TO RANGE FROM 2 TO 4 IN THE NORTH...TO 6 TO 8 IN THE SOUTH WHERE
MOISTURE/INSTABILITY WILL BE GREATEST. THIS PUTS STORM TOTAL
AMOUNTS IN THE 6 TO 8 INCH RANGE IN THE NORTH...TO CLOSE TO 14 OR
A LITTLE MORE IN THE SOUTH. ALONG INTERSTATE 80 AM EXPECTING A
RANGE OF 9 TO 12.
SNOW WILL LIKELY TAPER AS WE GO PAST MIDNIGHT. HOWEVER AM ALSO
EXPECTING A LITTLE LONGER DURATION THAN MODELS ARE INDICATING AS
DEFORMATION ZONE SETS UP ACROSS THE NORTHERN PART OF THE
CWA...GENERALLY NORTH OF INTERSTATE 80.
TEMPERATURES CURRENTLY ARE IN THE MIDDLE TEENS IN THE NORTH TO
NEAR 30 IN SOUTHEAST NEBRASKA...WITH TEMPERATURES IN THE SINGLE
DIGITS IN EASTERN SOUTH DAKOTA. COLD AIR WILL PLUNGE SOUTH AS
SURFACE LOW PULLS EAST LATE TONIGHT...SO CURRENT FORECAST OF
SINGLE DIGITS FOR MOST OF THE CWA LOOKS ON TRACK...WITH NEGATIVE
SINGLE DIGITS IN THE FAR NORTHWEST. THESE TEMPERATURES COMBINED
WITH WINDS NEAR 30 MPH AT 6 AM PUT WIND CHILLS IN THE MINUS 15 TO
MINUS 25 RANGE. AND TEMPERATURES SHOULD NOT MOVE MUCH DURING THE
DAY WEDNESDAY GIVEN CONTINUED COLD ADVECTION...FRESH SNOW COVER
AND LINGERING CLOUDS.
WINDS SHOULD BEGIN TO DIE DOWN AFTER NOON WEDNESDAY...BUT WILL NOT
REALLY SLACK OFF UNTIL SUNSET. CLOUDS SHOULD ALSO DECREASE
WEDNESDAY EVENING...ALLOWING A DECENT RADIATIONAL COOLING EVENT TO
SET UP FOR THURSDAY MORNING. HAVE LOWS WELL BELOW ZERO IN MOST OF
THE CWA THEN.
SOUTHWEST WINDS AND SUNSHINE WILL TRY TO WARM THINGS UP A BIT ON
THURSDAY...BUT TEENS WILL BE ALL WE CAN MUSTER. RELATIVELY LIGHT
WINDS CONTINUE THURSDAY NIGHT AND FRIDAY...WITH AN INCREASE IN
CLOUDS FRIDAY AFTERNOON. SO NO BIG WARMUP EXPECTED THEN EITHER.
DERGAN
LONG TERM...FRIDAY NIGHT THROUGH TUESDAY.
MAIN UPPER LEVEL PATTERN WILL FEATURE A BROAD TROUGH OVER CANADA
WITH RELATIVELY ZONAL OR SHALLOW TROUGH FLOW OVER THE CENTER PART
OF THE COUNTRY. A COUPLE OF OPEN WAVES WILL ROLL THROUGH THAT FLOW
SATURDAY MORNING THEN AGAIN SUNDAY BEFORE NEXT MORE POTENT WAVE
SETTLES INTO THE PLAINS TUESDAY. THE SYSTEM SUNDAY WILL HAVE
MOISTURE TO WORK WITH SO HAVE INSERTED A CHANCE FOR SNOW THEN.
THE SYSTEM TUESDAY LOOKS TO KEEP MOISTURE OVER THE SOUTHERN
PLAINS...SO HAVE KEPT FORECAST DRY THEN. TEMPERATURES START THE
LONG TERM PERIOD WARMER...WITH HIGHS SATURDAY IN THE 20S. HOWEVER
COLDER AIR FILTERS INTO THE REGION BEHIND EXITING SHORTWAVE AS
ARCTIC HIGH SETTLES OVER THE REGION. SNOW COVER AND LIGHT WINDS
SHOULD ALLOW TEMPS TO APPROACH ZERO. NO REAL END IN SIGHT FOR THE
COLD TEMPERATURES AFTER THAT.
DERGAN
AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
VERY PESSIMISTIC TAFS WERE WRITTEN WITH LIFR CONDITIONS THRU MOST OF
THE PERIOD DUE TO FALLING SNOW INITIALLY...WITH WINDS 10 TO 15 KTS.
HOWEVER...CONDITIONS COULD BRIEFLY IMPROVE TO MVFR AT TIMES AS HEAVY
SNOW SHOWERS MOVE IN/OUT OF THE AREA...BUT NOT NECESSARILY TIMED IN
THE TAF FORECAST. BY 00-02Z...WINDS BECOME 340-360 AND SUBSTANTIALLY
INCREASE TO SUSTAINED 23KTS WITH GUSTS EO 34KTS...AND INCREASING BY
06-10Z SUSTAINED 27 TO 29KT WITH GUSTS TO 36S...CREATING WIDESPREAD
VISBYS AOB BELOW 1/2MILE. BY 08Z AT KOFK/KLNK...CIGS SHOULD IMPROVE
TO MVFR...AND POSSIBLY BY 12-13Z AT KOMA.
DEWALD
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...BLIZZARD WARNING UNTIL NOON CST WEDNESDAY FOR NEZ011-012-015>018-
030>034-042>045-050>053-065>068-078-088>093.
IA...BLIZZARD WARNING UNTIL NOON CST WEDNESDAY FOR IAZ043-055-056-069-
079-080-090-091.
&&
$$
