FXUS63 KOAX 171023
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
423 AM CST FRI DEC 17 2010
.DISCUSSION...
SNOW CHANCES SUNDAY AND MONDAY ARE THE PRIMARY FORECAST CONCERNS.
HANDLING OF CLOUDS AND THEIR AFFECTS ON TEMPERATURES TODAY AND
SATURDAY IS ALSO A PROBLEM.
PESKY BAND OF STRATUS EXTENDING FROM MONTANA THROUGH EASTERN
NEBRASKA WAS PLAYING HAVOC ON TEMPERATURES THIS MORNING. TEMPS ARE
HOLDING IN THE 20S UNDER THE CLOUDS...BUT DIP QUICKLY INTO THE TEENS
WHERE SKIES CLEAR ALONG NORTHERN EDGE OF CLOUDS IN OUR NORTHERN CWA.
CLOUD AXIS WAS SLIPPING SOUTH...BUT SOUTHEAST SURGE FROM CENTRAL
SOUTH DAKOTA SUGGESTS CLEARING TREND WILL END THIS MORNING. THEN
QUESTIONS IS WHETHER WE WILL BREAK OUT LATER TODAY. SURFACE HIGH
PRESSURE IS FORECAST TO REMAIN OVER OUR AREA WHICH WILL LIMIT
MIXING...AND NOT SEEING ANYTHING ALOFT IN WATER VAPOR IMAGERY THAT
WILL SCOUR OUT LOW LEVEL MOISTURE. THUS AM EXPECTING LOTS OF CLOUDS
ACROSS THE CWA TODAY...HOLDING TEMPERATURES TO A CATEGORY OR TWO
ABOVE SUNRISE TEMPERATURES.
IF CLOUDS STICK AROUND TODAY...SEE NO REASON THEY WILL GO ANYWHERE
TONIGHT. SO HAVE BUMPED OVERNIGHT LOWS UP A BIT FROM GOING FORECAST.
MOST SPOTS SHOULD DIP INTO THE TEENS. THEN MUCH OF THE SAME ON
SATURDAY WITH HIGHS BACK INTO THE 20S.
NEXT CHANCE OF PRECIPITATION COMES SATURDAY NIGHT AND SUNDAY AS A
WEAK MID LEVEL WAVE SHIFTS INTO THE REGION FROM THE WEST. LOW AND
MID LEVEL WARM ADVECTION SHOULD PROVIDE LIFT BEGINNING AFTER
MIDNIGHT SATURDAY NIGHT OVER MOST OF THE CWA...WITH THAT AREA MOVING
EAST AFTER NOON ON SUNDAY. GFS IS MOST AGGRESSIVE WITH THIS
POTENTIAL ROUND OF PRECIP AND WAS GENERALLY FOLLOWED.
MOISTURE...ESPECIALLY IN THE LOWER LEVELS...MAY INHIBIT SNOWFALL
INITIALLY...BUT SEVERAL HOURS OF TOP DOWN SATURATION SHOULD ALLOW
LIGHT SNOW TO AFFECT MUCH OF THE CWA. GARCIA METHOD CALCULATIONS
ALONG 295K THETA SURFACE SUGGESTS A TWO INCH MAXIMUM SNOW IS
POSSIBLE...BUT WILL CUT THAT IN HALF GIVEN DRY LOW LEVELS...WITH
AXIS OF HIGHEST TOTALS NEAR AND NORTH OF THE PLATTE RIVER IN
NEBRASKA INTO WEST CENTRAL IOWA.
AN EVEN STRONGER MID LEVEL WAVE WILL ENTER THE PLAINS ON SUNDAY
NIGHT AND MONDAY. QG FORCING IS MORE ROBUST WITH THIS SYSTEM THUS
LOW LEVEL WARM/MOIST ADVECTION IS MORE PRONOUNCED. SOME QUESTION ON
TRACK WITH THIS SYSTEM. GFS PAINTS AXIS OF HIGHEST QPF ACROSS
SOUTHERN SOUTH DAKOTA...BUT GIVEN 850 BAROCLINIC ZONE AND TRACK OF
700MB LOW ALONG THE KANSAS BORDER...THINK PRECIP WILL LINE UP A
LITTLE FARTHER SOUTH...PERHAPS OVER NORTHERN NEBRASKA. GARCIA
CALCULATIONS WITH THIS SYSTEM SUGGEST THREE INCH MAXIMUM FROM AROUND
MIDNIGHT SUNDAY NIGHT INTO EARLY MONDAY AFTERNOON. HAVE PAINTED 2 TO
3 INCHES IN THE NORTHERN CWA...TAPERING TO ABOUT AND INCH IN THE
OMAHA METRO.
TEMPERATURES SUNDAY AND MONDAY COULD REBOUND INTO THE LOWER 30S EACH
DAY WITH EACH OF THESE SYSTEMS. THEN TEMPERATURES LOOK TO MODERATE
SOME NEXT WEEK AS UPPER RIDGE TRIES TO BUILD INTO THE REGION.
HOWEVER UPPER FLOW IS MORE NORTHWESTERLY OVER OUR AREA WITH RIDGE
AXIS TO THE WEST. THIS SUGGESTS A WIDE RANGE OF TEMPERATURES IS
POSSIBLE DEPENDING ON JUST HOW FAR EAST RIDGE AXIS SHIFTS. WILL KEEP
FORECAST UNCHANGED FOR NOW WITH HIGHS MAINLY IN THE 30S THROUGH NEXT
WEEK.
DERGAN
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
BAND OF MVFR CIGS DRIFTING SOUTH ACROSS AREA AT 06Z WITH BKN TO OVC
CONDITIONS EXPECTED TO PREDOMINATE THROUGH 18Z. AREAS OF MVFR VSBY
IN FOG ALSO POSSIBLE WHERE CLOUDS DO SCT OR CLEAR FOR A TIME. VFR
CONDITIONS EXPECTED TO DEVELOP ACROSS THE AREA AFTER 18Z AS SURFACE
HIGH BUILDS INTO THE AREA AND STRONGER CYCLONIC FLOW SHIFTS
NORTHEAST.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$