FXUS63 KOAX 112105
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
305 PM CST THU NOV 11 2010
.SHORT TERM...TONIGHT THROUGH SUNDAY.
SOMEWHAT DIFFICULT FORECAST THE NEXT FEW DAYS. MODELS ARE NOT IN VERY
GOOD AGREEMENT WITH RESPECT TO QPF AND THERMAL PROFILES. OF THE 12Z
MODELS...THE GEM (CANADIAN) MAY BE THE BEST FOR TONIGHT AND FRIDAY
BUT AFTER THAT IS APPEARS IT MOVES PCPN TOO FAR EAST FOR FRIDAY
NIGHT AND SATURDAY. THE 00Z ECMWF SEEMED TO BE A DECENT COMPROMISE
FOR FRIDAY NIGHT AND EARLY SATURDAY.
500 MB CHART FROM THIS MORNING DID NOT SHOW MUCH FOR HEIGHT FALLS
WITH SYSTEM OVER THE SOUTHWESTERN U.S. THIS MORNING. MODELS SUGGEST
THAT THERE MIGHT HAVE BEEN 12 HOUR HEIGHT FALLS OF UP TO 30 METERS
IN EASTERN CALIFORNIA AND PARTS OF ARIZONA. AT 300 MB...THERE WAS A
LONG STRETCH OF WINDS OF 100 KTS OR MORE THAT STRETCHED FROM ARIZONA
INTO MINNESOTA. SOME 850 MB MOISTURE WAS OVER THE SOUTHERN PLAINS...
AND THAT EXTENDED INTO THE GREAT LAKES. SOME OF THOSE HIGHER 850 MB
DEWPOINTS WILL MAKE IT INTO OUR SOUTHERN ZONES FOR TONIGHT.
PCPN SHOULD SPREAD ACROSS ALL OF THE FORECAST AREA DURING THE NIGHT
AS LIFT AND MOISTURE INCREASE IN THE 295-305K LAYER. KEPT MENTION OF
ISOLATED TSTMS WITH ELEVATED INSTABILITY FOR PARTS OF SOUTHEASTERN
NEBRASKA AND SOUTHWEST IOWA TONIGHT. THERMAL PROFILES WILL BE
CRITICAL IN REGARDS TO PCPN TYPE OVERNIGHT AND THEN AGAIN FOR FRIDAY
NIGHT. SOME SNOW APPEARS POSSIBLE ACROSS NORTHEAST NEBRASKA WITH MID
TROPOSPHERIC FRONTOGENESIS. KEPT AMOUNTS UNDER AN INCH FOR NOW...BUT
EVENING SHIFT WILL HAVE TO MONITOR. EXPECT LOWS TONIGHT IN THE 30S
AND HIGHS FRIDAY MOSTLY FROM AROUND 40 TO THE MID 40S.
SURFACE LOW PRESSURE CENTER SHOULD MOVE INTO EASTERN KANSAS BY
FRIDAY EVENING...THEN TRACK TO THE NORTHEAST...CROSSING IOWA
SATURDAY. SOME SNOW IS POSSIBLE ON THE WESTERN FLANK OF PCPN SHIELD
IF COLD AIR CAN BE TAPPED. UNKNOWNS AT THIS POINT INCLUDE...WILL
THERE BE ENOUGH COLD AIR IN THE BOUNDARY LAYER TO ALLOW FOR SNOW TO
BECOME THE PREVAILING PCPN TYPE AND WILL SURFACE TEMPERATURES BE
COLD ENOUGH FOR ANY ACCUMULATION ON THE GROUND. AT THIS POINT A
GENERAL BLEND OF MODELS WAS USED. 12Z NAM APPEARED TO HAVE SURFACE
LOW TOO FAR WEST...WHILE THE 12Z GFS WAS PROBABLY TOO FAR EAST.
TROWAL STRUCTURE SEEMS TO SETUP WITH SYSTEM FRIDAY NIGHT AND INTO
SATURDAY MORNING. AT THIS POINT...HEAVIEST SNOW EXPECTED IN NORTHERN
IOWA AND SOUTHERN MINNESOTA.
SATURDAY NIGHT AND SUNDAY SHOULD BE DRY.
.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY.
EXTENDED FORECAST GENERALLY ENTAILS A BROAD UPPER TROUGH OVER THE
CENTRAL U.S. WITH BELOW NORMAL HEIGHTS AND MIGRATORY EMBEDDED
SHORTWV TROUGHS BRINGING PDS OF WARMING AND THEN SUBSEQUENT
COOLING. BASIC MODEL AGREEMENT ON THIS SCENARIO BETWEEN 12Z GFS/00Z
ECMWF WITH GFS ENSEMBLE MEAN...AS EXPECTED...A MODERATING REFLECTION
OF OPERATIONAL GFS. I.E. A LTL WARMER ON COOL ADVCTN DAYS AND COOLER
DURING WARM ADVCTN PDS. THIS FORECAST WAS GENERALLY BASED ON A
MONDAY BEING A NEUTRAL RECOVERY DAY AS A WEAK WAVE TRAILS WEEKEND
STORM...WARM ADVCTN ON TUES AHEAD OF NEXT CLIPPER...COLD ADVCTN
BEHIND IT ON WED AND THEN WARM ADVCTN AHEAD OF NEXT ONE FOR DAY
7...ALTHOUGH THIS TIMING COULD MOST LIKELY CHANGE WITH LATER RUNS.
TEMPERATURE FORECAST WAS BASED ON PREMISE THAT LTL/NO SNOW
ACCUMULATION WOULD OCCUR INTO SATURDAY OR IF IT DID...IT WOULD BE
MOSTLY GONE BEFORE MONDAY. THUS MAIN TEMPERATURE ADJUSTMENT WAS TO
BOOST READINGS ON TUESDAY AHEAD OF FIRST EXTENDED CLIPPER WITH LTL
CHANGES OTHER PDS. FOR THE NEW DAY 7 GENERALLY TRENDED A FEW
DEGREES ABOVE THE 12Z MEX GUIDANCE WHICH APPEARED A LTL TOO GIVEN
CONDITIONS OFTEN WARM A BIT MORE THAN EXPECTED AHEAD OF THESE
SYSTEMS. A FEW PDS OF LIGHT PCPN CANNOT BE RULED OUT WITH EACH
SUBSEQUENT WAVE...BUT TIMING AND MOISTURE AVAILABILITY QUESTIONABLE.
LEFT FORECAST DRY UNTIL MODELS BECOME MORE CONSISTENT IN
TIMING/STRENGTH OF ANY FUTURE WAVE.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
A STORM SYSTEM FROM THE DAKOTAS EXTENDING SOUTHWEST TO THE FOUR
CORNERS REGION WILL SHIFT EASTWARD THROUGH 18Z AND WILL RESULT IN
WIDESPREAD PRECIPITATION DEVELOPING. INITIALLY...MID AND HIGH
CLOUDS WILL THICKEN AS RH INCREASES AND H7 WAA/MID LEVEL UVV
INCREASES. PRECIPITATION WILL BECOME MORE WIDESPREAD AS THE EVENING
WEARS ON AS A STRONG BAROCLINIC ZONE DEVELOPS WITH RAIN AT ALL THREE
TAF SITES OVERNIGHT. TSRA MAY DEVELOP IN SOUTHEAST NEBRASKA. WHEN WE
HAVE A BEEN HANDLE ON THE TIMING MAY HAVE TO EXPAND NORTHWARD AND
INCLUDE IN THE TAFS. RAIN MIXED WITH OR CHANGING TO SNOW WILL BE
POSSIBLE DUE TO THE STRONG LIFT IN THE SATURATED/DENDRITIC LAYER...
AND INSTABILITY ABOVE THE FRONTOGENTIC ZONE. THE THERMAL PROFILE
WILL DETERMINE IF/HOW MUCH SNOW DEVELOPS AND FOR NOW HAVE A MIX IN
AT KOFK WITH IFR CIGS/VSBYS. VFR CIGS AND VSBYS WILL LOWER TO
MVFR/IFR BTWN 06Z AND 09Z AND THE PRECIPITATION IS FORECAST TO LAST
THROUGH FRIDAY MORNING.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
SHORT TERM...MILLER
LONG TERM....CHERMOK
AVIATION...ZAPOTOCNY