FXUS63 KOAX 062125
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
ISSUED BY NATIONAL WEATHER SERVICE HASTINGS NE
325 PM CST THU JAN 6 2011
.DISCUSSION...THE PRIMARY FORECAST CONCERN WILL CENTER AROUND
SNOWFALL CHANCES FRIDAY MORNING AND THEN AGAIN SATURDAY NIGHT
THROUGH MONDAY NIGHT.
THE FIRST CHANCE OF SNOW COMES FROM A SHORT WAVE CURRENTLY OVER
SOUTHERN CANADA...THAT WILL DIVE SOUTH AND TRACK THROUGH WESTERN
IOWA FRIDAY MORNING. MOST OF THE ENERGY/FORCING WITH THIS THIS
SYSTEM WILL BE FOUND ACROSS CENTRAL IOWA...BUT CAN NOT COMPLETELY
RULE OUT SCATTERED SNOW SHOWERS ACROSS OUR IOWA ZONES BETWEEN
MIDNIGHT TONIGHT AND FRIDAY AFTERNOON. NOT REALLY EXPECTING MUCH
SNOW WITH THIS OUTSIDE OF MAYBE A TRACE TO LIGHT DUSTING. DEBATED
PUTTING FLURRIES IN THE FORECAST FOR OMAHA DURING THIS SAME
PERIOD...BUT FINALLY DECIDED THAT THE MOST LIKELY SCENARIO WOULD
KEEP THE SNOW JUST EAST OF THE OMAHA METRO AREA. HOWEVER...WOULD
ALSO NOT BE TOTALLY SURPRISED IF A FEW FLURRIES DID HAPPEN TO WORK
ACROSS THE RIVER INTO FAR EASTERN NEBRASKA TOMORROW. ALL IN ALL
THIS SHOULD NOT BE TO BIG OF A DEAL.
THE NEXT SYSTEM WILL LIKELY BE MUCH MORE OF A PROBLEM FOR
MOST OF OUR FORECAST AREA. A STRONG SHORT WAVE WILL COME ASHORE
OVER THE PACIFIC NORTHWEST FRIDAY EVENING AND THEN DIVE SOUTH INTO
THE CENTRAL ROCKIES BY SATURDAY NIGHT. A PROLONGED PERIOD OF
ISENTROPIC LIFT AND FAVORABLE JET DYNAMICS WILL ALLOW SNOW TO
REALLY GET GOING ACROSS A RATHER LARGE SWATH OF THE CENTRAL PLAINS
BY SUNDAY INTO MONDAY. THIS WILL BASICALLY BE A PROLONGED LIGHT
SNOW EVENT. UNCERTAINTY STILL REMAINS DUE TO THE REALITY THAT THIS
STORM SYSTEM IS CURRENTLY OUT OVER THE PACIFIC OCEAN AND SEVERAL
DAYS AWAY.
HOWEVER...THERE ARE AN INCREASING NUMBER OF FACTORS THAT ARE
LEADING TO INCREASED CONFIDENCE IN SEEING A SNOW EVENT FOR OUR
AREA. THE GREATEST OF THESE FACTORS IS GENERAL MODEL
CONSENSUS...WHICH IS CURRENTLY PLACING THE HEAVIEST SNOW BAND
SOMEWHERE BETWEEN CENTRAL AND EASTERN NEBRASKA. THE 12Z RUNS OF
THE GFS...ECMWF...GEM...AND 15Z SREF ENSEMBLES ALL INDICATE A
RATHER HIGH PROBABILITY OF ACCUMULATING SNOW ACROSS OUR FORECAST
AREA...ESPECIALLY OUR EASTERN NEBRASKA ZONES. NUMEROUS FORECAST
MODELS ARE EVEN SHOWING THE POSSIBILITY OF SEEING OVER 6 INCHES OF
SNOW IN THESE MORE FAVORED AREAS OVER A 60HR PERIOD RUNNING FROM
SATURDAY NIGHT THROUGH MONDAY NIGHT. PREDICTING SNOWFALL TOTALS
THIS FAR OUT FROM AN EVENT IS RATHER DIFFICULT AND SUBJECT TO
CHANGE IN THE COMING DAYS. HOWEVER...IF CURRENT MODEL TRENDS
CONTINUE THEN WE REALLY COULD BE LOOKING AT A DECENT 3 TO 6 INCH
SNOW EVENT ACROSS MUCH OF OUR FORECAST AREA AND MAYBE EVEN MORE
THAN THAT IN SOME PLACES. WILL HAVE TO CLOSELY MONITOR ANY CHANGES
IN STORM TRACK ONCE THE SYSTEM COMES ASHORE OVER THE PACIFIC
NORTHWEST AS SLIGHT TRACK VARIATIONS CAN HAVE RATHER PRONOUNCED
IMPACTS ON SNOWFALL AMOUNTS.
THERE IS REALLY NO STRONG SFC LOW PRESSURE SYSTEM ASSOCIATED WITH
THIS SYSTEM SO THE PRESSURE GRADIENT IS NOT OVERLY IMPRESSIVE.
CONSEQUENTLY...SFC WINDS SHOULD NOT BE TOO TERRIBLY STRONG WITH
THIS STORM SYSTEM ALTHOUGH IT STILL MIGHT BE A BIT BREEZY TOWARDS
THE CONCLUSION OF THE EVENT MONDAY NIGHT. VERY COLD AIR IS
EXPECTED TO SETTLE IN BEHIND THE STORM WITH HIGH TEMPERATURES ONLY
IN THE SINGLE DIGITS AND LOWER TEENS ON TUESDAY AND WEDNESDAY.
WIND CHILL VALUES MAY APPROACH -15 TO -25 IN SOME AREAS MONDAY
NIGHT AND TUESDAY NIGHT.
&&
.AVIATION...18Z TAF CYCLE. STRATUS ACROSS PARTS OF WESTERN IOWA MAY
AT TIMES CLIP KOMA THIS AFTERNOON...BUT SHOULD MOVE FAR ENOUGH EAST
BY LATE AFTERNOON TO GO PREDOMINATELY VFR IN THE TAF. A COLD FRONT
WILL MOVE ACROSS THE REGION TONIGHT INTO EARLY FRIDAY WHICH WILL
BRING INCREASING WINDS TO THE TAF SITES. H85 WINDS ALSO INCREASE
QUITE A BIT OVERNIGHT...AND CONTINUED TO MENTION THE POSSIBILITY OF
LLWS IN THE TAF WITH WINDS AROUND 2KFT FORECAST TO BE NEAR 50KTS.
THERE ARE SOME SIGNS IN THE MODELS THAT MVFR LEVEL CIGS MAY APPROACH
KOMA AND KOFK OVERNIGHT...SO MAINTAINED THAT IN THE LATEST
FORECAST.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
DISCUSSION...WESELY
AVIATION...KING