FXUS63 KOAX 272102
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
302 PM CST THU JAN 27 2011
.SHORT TERM...TONIGHT THROUGH SUNDAY.
ONLY MINOR CHANGES MADE THROUGH SUNDAY...MAIN ONE WAS TO INCLUDE
A SMALL SNOW CHC NRN ZONES SAT AFTN. NWRLY UPPER FLOW TO PERSIST
INTO FRIDAY BEFORE IT FLATTENS OUT SOME AS ONE STRONGER SHORTWV
TROUGH DROPS TWD GREAT LAKES REGION LATE FRIDAY AND ANOTHER WEAKER
ONE TRACKS ACROSS SD ON SAT.
LEAD SHORTWV WILL SEND SFC LOW SEWD ALONG U.S. CANADIAN BORDER
TOMORROW BUT BACKING SFC WINDS IN ADVANCE WILL NOT ARRIVE TILL
LATE TNGT. THIS WILL PROBABLY ALLOW ENOUGH OF A DECREASE IN WINDS
THAT WITH CURRENT SNOW COVER IN PLACE WILL BOTH SEND MANY LOWS
BELOW GUIDANCE/CURRENT FORECAST AND ALSO POSSIBLY ALLOW PATCHY FOG
TO DEVELOP. MADE THOSE ADJUSTMENTS. ON FRIDAY...ALTHOUGH
TEMPERATURES NEAR AND ABOVE H9 INCREASE MOST AREAS OVER TDAS
LVLS...MIXING SERN 1/2 OR SO MAY NOT BE QUITE AS GREAT AS TDA AS
12Z GFS/ECMWF JOINED NAM IN NOT MOVG SFC TROUGH ACROSS THAT AREA
UNTIL AFT 18Z. THUS DECIDED TO GO WITH A MORE PERSISTENCE TYPE OF
FORECAST SOUTH COUNTING ON THE WARMING LOWER PART OF THE SOUNDING
OVERCOMING LACK OF MIXING. NRN ZONES COULD SEE A DEG OR TWO
INCREASE FRIDAY OVER TDA IF NAM/ECMWF ARE CORRECT IN NOT ALLOWING
STRONGER COOL ADVCTN TO ARRIVE UNTIL FRI NGT. THIS COOLER AIR
CONTINUES FILTERING SWD ON SATURDAY BUT SINCE IT WAS MODEST AT
BEST...MAV/MET GUIDANCE APPEARS TO HAVE A GOOD HANDLE ON TEMPS AND
FIT PREV FCST VERY WELL. THUS LTL/NO CHANGES MADE TO TEMPS SAT.
HOWEVER...WITH SECOND SHORTWV TROUGH MOVG TWD NERN NEBR BY 00Z
SUN...INCREASING ISENTROPIC UPGLIDE/FORCING FROM THIS TROUGH
BEGINS PROVIDING LIFT IN DENDRITIC LAYER NERN NEBR SAT AFTN WHICH
COULD BE ENOUGH TO OVERCOME DRY AIR IN H85-H7 LAYER. THUS ADDED
THE SMALL SNOW CHC NRN ZONES SAT AFTN.
AS THIS WAVE PASSES ANOTHER PUSH OF EVEN COLDER AIR SHOULD SPREAD
OVER THE CWA ON SUNDAY. AGAIN CURRENT FORECAST LOOKED PRETTY
GOOD...THIS TIME A BIT ABOVE GUIDANCE...AS MORE SHORTWAVE ENERGY
MOVG ACROSS ROCKIES SHOULD HOLD UP THE COLDEST AIR TILL AFTER THE
SUN NGT/MON SYSTEM ROLLS THROUGH. LEFT IN SMALL SNOW CHCS NRN
ZONES AS LIFT BEGINS IN ADVANCE OF THIS SYSTEM WHICH HAD 12Z
GFS/ECMWF SUPPORT.
.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY
THE EXTENDED FORECAST CONTINUES TO BE DOMINATED BY NORTHWEST FLOW
ALOFT AND WELL BELOW NORMAL TEMPERATURES. THE MAIN STORM SYSTEM TO
AFFECT THE FORECAST AREA IN THE EXTENDED IS SUNDAY NIGHT THROUGH
MONDAY NIGHT. THE 12Z ECMWF IS NOT NEARLY AS BULLISH WITH THE SNOW
FOR MONDAY AS IT WAS YESTERDAY...HOWEVER THE 12Z GFS DID TREND
TOWARD MORE SNOW FOR SUNDAY NIGHT AND MONDAY. SUNDAY NIGHT...THE
00Z ECMWF AND 12Z GFS ARE FAIRLY CLOSE IN THEIR LARGE SCALE FEATURES
OF A MID TROPOSPHERIC CLOSED LOW OVER NEVADA AND CALIFORNIA...WITH A
NORTHERN STREAM TROF SWINGING THRU THE NRN ROCKIES AND NRN
PLAINS...WHICH IS ROTATING AROUND THE CANADIAN VORTEX. A BAND OF
SNOW IS PROGGED TO DEVELOP WITH THE COLD CANADIAN HIGH...THIS SNOW
EXTENDS FM MONTANA AND WYOMING SOUTHEAST INTO THE
DAKOTAS/NEBRASKA/IOWA SOUTHEASTWARD. THE 00Z ECMWF HAS LITTLE IN
THE WAY OF SNOW AMTS...WITH THE GFS A LITTLE HIGHER WITH A BAND OF
1-3 INCHES. THE GEM IS SIMILAR TO THE GFS...HOWEVER THE QPF AMOUNTS
ARE QUITE BIT HIGHER AND DISPLACED NORTHWARD 150-200 MILES. THE 12Z
ECMWF HAS LIGHT AMOUNTS ACRS THE CWA AND BETTER AMOUNTS IN SOUTH
DAKOTA INTO IOWA. FOR THIS FORECAST...USED A BLEND OF THE ECMWF/GFS
AND RAISED POPS FOR THE SUNDAY NIGHT INTO THE MONDAY PD. LOOKS LIKE
A VERY COLD PD WITH THE 1045MB HIGH BUILDING IN. WE ARE CURRENTLY
FORECASTING TEMPERATURES 10 TO 20 DEGREES BELOW NORMAL MON-WED.
TEMPERATURES DON/T APPEAR TO WARM UP TO NORMAL UNTIL AT LEAST
THURSDAY.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
VFR CONDITIONS ARE EXPECTED THRU MUCH OF THE TAF PERIOD. LOW LEVEL
RH IS FORECAST TO INCREASE OVERNIGHT WHICH COULD BRING LOWER
VISIBILITIES AND/OR AN INCREASE IN STRATUS. DID BRING IN A TEMPO
GROUP DURING THE EARLY MORNING HOURS TO DROP VISIBILITIES TO 3 MILES
AND INCLUDED A SCT STRATUS DECK.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
CHERMOK/ZAPOTOCNY/KERN