Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 252120
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
320 PM CST THU DEC 25 2014

.SHORT TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 320 PM CST THU DEC 25 2014

FAIRLY COMPLEX FORECAST THROUGH FRIDAY NIGHT. THE MAIN FORECAST
CONCERNS ARE HOW FAST LOW CLOUDS MOVE IN FOR TONIGHT INTO
FRIDAY...THEN PCPN TYPE AND PCPN AMOUNTS FRIDAY THROUGH FRIDAY
NIGHT.

AN IMPRESSIVE TROUGH WAS OVER THE ROCKIES THIS MORNING. 12 HOUR
HEIGHT FALL MAX AT 500 MB WAS 210 METERS OVER SOUTHERN NEVADA. A
115 KNOT JET MAX WAS DIGGING SOUTHEAST ALONG THE CALIFORNIA COAST.
SHORT RANGE MODEL INITIALIZATION IN COMBINATION WITH WATER VAPOR
SATELLITE IMAGERY LOOP SHOWED A CLOSED LOW ALONG THE NEVADA/UTAH
BORDER AT MID AFTERNOON. SURFACE ANALYSIS AT 21Z SHOWED A COLD
FRONT CURVING FROM NORTHEAST MINNESOTA INTO NORTHEAST NEBRASKA
THEN INTO NORTHWEST KANSAS. THIS FRONT WILL PUSH SOUTHEAST
THROUGH ALL OF THE FORECAST AREA OVERNIGHT...TURNING WINDS TO THE
NORTHWEST OR NORTH. JUST HOW FAST LOW CLOUDS WILL FILL IN BEHIND
THE FRONT IS A CHALLENGE. 18Z NAM WAS USED MAINLY FOR THIS...BUT
BLENDED IN SOME OTHER GUIDANCE. THE RESULT IS A FORECAST THAT LOW
CLOUDS SHOULD MOVE INTO THE OMAHA AND LINCOLN AREAS IN THE EARLY
MORNING HOURS. FORCING AND MOISTURE DEPTH ARE NOT IMPRESSIVE
ENOUGH TO CREATE MUCH PCPN TONIGHT...BUT DID KEEP SOME LOW POPS
GOING IN ABOUT THE NORTHWEST HALF OF NORTHEAST NEBRASKA TONIGHT.

FRIDAY...THE CLOSED LOW AT 500 MB SHOULD BE OVER THE FOUR CORNERS
REGION AT 12Z...MOVE TO CENTRAL COLORADO BY 00Z SATURDAY THE KICK
NORTHEAST AND OPEN UP BY 12Z SATURDAY. BY THAT TIME...LIFT HAS
MOSTLY ENDED WITH PCPN SHIFTING OUT OF THE FORECAST AREA.

DURING THE DAY FRIDAY...MAINLY USED A BLEND OF THE 12Z GFS AND THE
12Z ECMWF FOR DETAILS. PCPN SHOULD INCREASE IN THE AFTERNOON OVER
ABOUT THE NORTHWEST HALF OF THE AREA...WITH SOME CHANCE OF LIGHT
RAIN...LIGHT SNOW OR FREEZING DRIZZLE FARTHER EAST. MODEL FORECAST
SOUNDINGS SHOW THAT PCPN TYPE WILL EVENTUALLY CHANGE TO ALL SNOW
AS THE COLD AIR DEEPENS. BULK OF THE ACCUMULATING SNOW FRIDAY
AFTERNOON IS EXPECTED IN NORTHEAST NEBRASKA. HEAVIEST PCPN STAYS
TO THE NORTHWEST OF OMAHA AND LINCOLN...IN A BAND WHERE MID LEVEL
LIFT AND LAYER MOISTURE ARE MAXIMIZED. SOME LIGHT PCPN MAY DEVELOP
AHEAD OF THE MAIN AREA OF SNOW...WHICH WOULD BE A MIX...AND BASED
ON SURFACE TEMPERATURES MAY FREEZE ON IMPACT. FOR NOW THAT DOES
NOT LOOK LIKE IT WILL CAUSE MANY ISSUES...BUT WILL NEED TO MONITOR
FOR POSSIBLE UPDATES.

BEST LIFT IN THE DEFORMATION ZONE STAYS OVER ABOUT THE NORTHERN
HALF OF THE FORECAST AREA FOR FRIDAY NIGHT. THEN LIFTS INTO
NORTHERN IOWA AND SOUTHERN MINNESOTA. SNOW AMOUNTS MAY REACH 1 TO
3 INCHES IN NORTHEAST NEBRASKA. SINCE WINDS DO NOT LOOK OVERLY
STRONG...OPTED TO NOT HAVE ANY HEADLINES AT THIS POINT.

THE PERIOD FROM SATURDAY INTO SUNDAY STILL LOOKS DRY...WITH WEAK
HIGH PRESSURE DOMINATING. A COLD FRONT WILL PUSH THROUGH DURING
THE DAY SUNDAY...AND THINGS WILL GET GRADUALLY COLDER FROM THAT
POINT ONWARD INTO MID WEEK. STRONG MID LEVEL RIDGE WILL BE IN
PLACE ALONG 130-140 DEGREES WEST LONGITUDE BY SUNDAY...AND A COLD
TROUGH WILL TAKE SHAPE OVER THE NORTHERN CONUS.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 320 PM CST THU DEC 25 2014

WILL KEEP SOME CHANCE OF LIGHT SNOW GOING FROM SUNDAY NIGHT INTO
MONDAY NIGHT AS AN ARCTIC AIRMASS DROPS DOWN OVER THE NORTHERN AND
CENTRAL PLAINS. BEST CHANCES FOR ACCUMULATING SNOW IN THOSE PERIODS
REMAINS OVER THE HIGH PLAINS WHERE THERE WILL BE A STRONGER UPSLOPE
FLOW COMPONENT. CENTER OF THE ARCTIC HIGH WILL BE OVER WYOMING ON
TUESDAY BUT DROP DOWN INTO NORTH TEXAS BY WEDNESDAY. THIS SHOULD
HELP ALLOW SLIGHTLY WARMER AIR TO MOVE IN LATER IN THE WEEK.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1124 AM CST THU DEC 25 2014

TIMING DETERIORATING CONDITIONS UPON COLD FRONTAL PASSAGE THE
MAIN AVN CONCERNS WITH THIS TAF ISSUANCE. LATEST SFC SHOWING SFC
LOW PRES CENTERED IN ERN CO WITH ATTENDANT COLD FRONT STRETCHING
FROM CNTRL MN TO NW KS. BNDRY HAS BEEN STAGNANT THE LAST SEVERAL
HOURS DUE TO RELATIVELY STRONG SOUTHERLY WINDS OVER THE CNTRL
PLAINS. THE BNDRY THOUGH SHOULD BEGIN MAKING A PUSH SWD BY EARLY
EVENING AND THROUGH ERN NEB OVERNIGHT. EXPECT MVFR CIGS TO
ACCOMPANY LEADING EDGE OF THE FRONT...AT KOFK AROUND 02Z...AND
KOMA/KLNK AROUND 05Z. IN ADDITION...HAVE DECIDED TO INTRODUCE
PROB30 GROUPS EARLY FRI MORNING FOR POSSIBLE -SN/IFR. AS FOR SN
ACCUM THRU 18Z FRI...LESS THAN AN INCH AT KOFK...LITTLE IF ANY AT
KOMA/KLNK.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$

SHORT TERM...MILLER
LONG TERM...MILLER
AVIATION...DEE



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