FXUS64 KOUN 051628
AFDOUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
1028 AM CST SAT DEC 5 2009
.UPDATE...
DEEPENING SURFACE LOW PRESSURE TO THE LEE OF THE ROCKY MOUNTAINS
IS RESULTING IN GUSTY SOUTHERLY WINDS ACROSS ALL BUT THE FAR
NORTHWEST PORTION OF THE CWA...WHICH IS IN A COMPARATIVELY WEAK
PRESSURE GRADIENT CLOSER TO THE LOW CENTER. THE FORECAST HAS THIS
WELL COVERED. EARLIER...THE SKY GRID FOR THIS AFTERNOON WAS UPDATED
TO DECREASE CLOUD COVER...AND HOURLY TEMPERATURES WERE UPDATED TO
GET A BETTER HANDLE ON HOURLY WIND CHILL TEMPS. NO FURTHER UPDATES
ARE PLANNED TO THE FORECAST THROUGH THIS AFTERNOON.
TAYLOR
&&
.PREV DISCUSSION... /ISSUED 519 AM CST SAT DEC 5 2009/
AVIATION...
12Z TAFS... VFR WITH CIRRUS THICKENING OVER TIME AS IT SPREADS E
ACROSS THE AREA. S WINDS INCREASING THIS MORNING TO 17-22G27-32KT
THEN REMAINING MODERATELY GUSTY MOST AREAS OVERNIGHT IN MOST
AREAS. EXCEPTION IN NW OK WHERE FRONT/WINDSHIFT WILL APPROACH KGAG
AND KWWR TOWARD 12Z WITH WINDS GOING LIGHT. GUIDANCE HINTS AT
LOWER CIGS INTO NW OK NEAR FRONT BUT HAS HAD A TENDENCY TO
OVERFORECAST THESE LATELY. HIGHER CHANCE OF LOWER CIGS MORE LIKELY
TO BE AFTER 12Z SUNDAY.
PREV DISCUSSION... /ISSUED 256 AM CST SAT DEC 5 2009/
DISCUSSION...
STRENGTHENING UPPER RIDGE OVER EPAC IS FORECAST BY ALL MODELS TO
FORM AN OMEGA BLOCK WITH A NEAR-580 500-MB HIGH NEAR THE AK COAST BY
SUNDAY. THUS WE ARE DESTINED TO REMAIN IN A PREVAILING COLD PATTERN
FOR MOST OF THE FORECAST. WEAKENING IS INDICATED IN THE RIDGE AND
A MORE ZONAL FLOW EVOLVES BY LATE WEEK. THIS SHOULD HELP US WARM
BACK UP CLOSER TO CLIMATOLOGY BY DAY 7.
1056-MB ARCTIC HIGH IS LOADING UP AND CHILLING DOWN OVER W CANADA
AND WILL MIGRATE SE INTO THE AREA EARLY NEXT WEEK. IN THE
MEANTIME... STRENGTHENING LEE TROUGH WILL CRANK UP THE S WINDS
TODAY. IT WILL NOT BE AS COLD AS FRIDAY... BUT WILL LIKELY FEEL WORSE
AS THE WINDS ADD A BITE TO THE COOL AIR. WILDFIRE POTENTIAL WILL GO
UP SOME TODAY DUE TO THE WINDS AND DRY AIR ALONG WITH DORMANT
VEGETATION... BUT TEMPS/RH WILL NOT BE LOW ENOUGH FOR FIRE WX
HEADLINES. WE WILL MAINTAIN SOME LOW POPS MAINLY N AND E FOR SUNDAY
AND SUNDAY EVENING AS A LEAD WAVE CROSSES THE AREA... FOLLOWED BY
ANOTHER S-WARD PUSH OF CANADIAN AIR ACROSS THE AREA SUNDAY NIGHT AND
MONDAY.
MAIN FORECAST CHALLENGE THIS MORNING IS WHAT TO DO WITH THE STRONGER
SYSTEM PROGGED TO AFFECT THE AREA AROUND TUESDAY. THE AIR IS NOT
TERRIBLY COLD NOW OVER CANADA... BUT THE STRENGTH OF THE SFC HIGH
SUGGESTS THAT THIS WILL BE ONE OF THOSE SHALLOW COLD AIR MASSES THAT
CAN BE HARD TO GET RID OF ONCE THEY MOVE IN. MODELS APPEAR TO BE
GETTING BETTER HANDLING THIS STUFF... BUT STILL SEEM TO USUALLY ERR
ON THE SIDE OF BEING TOO SLOW TO MOVE IT IN AND TOO QUICK TO MOVE IT
OUT. ON THIS BASIS WE ARE LEANING TOWARD A MORE SOUTHERN TRACK OF
THE SFC LOW ACROSS CENTRAL OR S OK TUESDAY AND TUESDAY EVENING...
MORE LIKE THE ECMWF VS THE FARTHER-N OPERATIONAL GFS. GFS ENSEMBLE
MEAN... AND MOST OF THE INDIVIDUAL MEMBERS... ALSO SUPPORT A SFC LOW
A LITLE FARTHER S THAN THE OPERATIONAL RUN. ECMWF AT 00Z IS FARTHER
N THAN ITS 12Z RUN AND MAY BE A LITTLE TOO FAR N AND TOO STRONG. KEY
ISSUE HERE IS THAT A MORE SOUTHERN TRACK WOULD KEEP N OK ON THE COLD
SIDE OF THE SYSTEM AND THUS MAINTAIN A HIGHER CHANCE OF APPRECIABLE
WINTER PRECIP ACROSS N OK... ALONG WITH BLOWING SNOW ON THE BACK
SIDE. LIMITED MOISTURE AND RAPID MOVEMENT LIKELY TO KEEP ANY AMOUNTS
ON THE LOW SIDE AS FAR SOUTH AS N OK... BUT MIGHT NOT TAKE MUCH OF A
S-WARD SHIFT IN THE TRACK TO CHANGE THAT. FARTHER S... BREEZY AND
MILDER IN THE DRY SLOT ON THE S SIDE OF THE SYSTEM ACROSS S OK AND N
TX. ANOTHER SHOT OF CANADIAN AIR ARRIVES BEHIND THIS SYSTEM FOR
MIDWEEK.
&&
.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK 49 33 49 26 / 0 0 10 10
HOBART OK 46 30 47 24 / 0 0 0 0
WICHITA FALLS TX 52 34 56 31 / 0 0 10 10
GAGE OK 47 20 34 14 / 0 0 10 0
PONCA CITY OK 47 31 41 21 / 0 0 20 10
DURANT OK 46 32 44 31 / 0 0 30 20
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&
$$
03/30
