National Weather Service Raw Text Product

109 
FXUS63 KOAX 280522
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1122 PM CST SUN JAN 27 2013

.AVIATION...06Z TAFS FOR KOFK...KLNK AND KOMA.

IFR/LIFR CIGS/VSBYS ARE FORECAST THROUGH ABOUT 18Z AT ALL EASTERN
NEBRASKA TAF SITES...THEN MVFR CIGS/VSBYS THEREAFTER. AREA OF LOW
CLOUDS WILL SLOWLY ERODE FROM WEST TO EAST THROUGH 12Z...BUT IN
THE CLEARING AREA BEHIND CLOUDS...WIDESPREAD FOG BELOW A HALF
MILE IS FORECAST. LIGHT SOUTHEAST WINDS BETWEEN 15Z AND 18Z WILL
SLOWLY ERODE SOME OF THE LOW LEVEL MOISTURE...BUT MVFR CIGS/VSBYS
WILL PERSIST THROUGH THE REST OF THE TAF PERIOD.

DERGAN

&&

.PREV DISCUSSION... /ISSUED 805 PM CST SUN JAN 27 2013/ 

UPDATE...
EXPANDED DENSE FOG ADVISORY TO INCLUDE KNOX...CEDAR...PIERCE AND
ANTELOPE COUNTIES IN OUR FAR NORTHWEST CWA. LIGHT WESTERLY WINDS
BEHIND WEAK FRONTAL BOUNDARY HAVE IMPROVED VISIBILITIES ACROSS
THE WESTERN HALF OF THE CWA. HOWEVER LOW LEVEL MOISTURE IS NOT
BEING SCOURED OUT...AND VISIBILITIES UNDER CLEAR SKIES IN CENTRAL
NEBRASKA HAVE DROPPED TO A QUARTER MILE. SO IF CLOUD CAN ERODE
FROM THE WEST...EXPECT DENSE FOG TO DEVELOP AS WINDS DECREASE. BUT
EXPECT CLOUDS TO HOLD FIRM ACROSS MOST OF OUR CWA. AND WITH
TRAPPED LOW LEVEL MOISTURE COMBINED WITH LIGHT SOUTHEAST WINDS
RETURNING AFTER MIDNIGHT...VISIBILITIES SHOULD TANK IN THIS
SCENARIO AS WELL. THUS VARIABLE VISIBILITIES THIS EVENING ARE
EXPECTED TO DROP TO OR BELOW A QUARTER MILE ALL AREAS.

DERGAN

PREV DISCUSSION... /ISSUED 539 PM CST SUN JAN 27 2013/ 

AVIATION...00Z TAFS FOR KOFK...KLNK AND KOMA.

IFR/LIFR CIGS/VSBYS ARE EXPECTED THROUGH MONDAY MORNING AS LOW
LEVEL MOISTURE CREATES AREAS OF DRIZZLE AND FOG UNDER A LIGHT WIND
REGIME. A WEAK FRONT MOVING EAST THROUGH THE AREA THIS EVENING
WILL LIKELY IMPROVE VSBYS TO MVFR/VFR FOR ABOUT 3 OR 4 HOURS...BUT
AS WINDS DIE DOWN LATER IN THE EVENING...EXPECT LIFR CONDITIONS
SOCK BACK IN. LIGHT SOUTHEAST FLOW ON MONDAY MORNING WILL KEEP
CIGS/VSBYS RELATIVELY LOW...WITH ONLY MODEST IMPROVEMENT AFTER
18Z.

DERGAN

PREV DISCUSSION... /ISSUED 356 PM CST SUN JAN 27 2013/ 

SHORT TERM...TONIGHT THROUGH WEDNESDAY.

SEVERAL FORECAST CONCERNS IN THE SHORT TERM...FOG AND DRIZZLE FOR
THE OVERNIGHT HOURS AND NEED FOR DENSE FOG ADVISORY...THEN
LOCATION OF WARM FRONT AND LINGERING FOG AND TEMPERATURES FOR
MONDAY...CHANCE OF PRECIPITATION AHEAD OF AND BEHIND THE COLD
FRONT IN NORTHEAST NEBRASKA MONDAY THROUGH TUESDAY
MORNING...REINFORCING COLD FRONT TUESDAY NIGHT AND WEDNESDAY.

MOST OF THE FORECAST AREA RECEIVED .05 TO .35 OF AN INCH OF 
RAINFALL.  ELEVATED SURFACES MAY HAVE BECOME SLICK NEAR THE SD/NE 
BORDER WITH REPORTS NEAR YANKTON...AND UTE IN MONONA COUNTY REPORTED 
A COUPLE OF HOURS OF FREEZING RAIN BEFORE SWITCHING OVER TO 
RAIN/DRIZZLE. THE BULK OF THE PRECIPITATION HAD MOVED OUT OF THE 
AREA BY 18Z. 
 
THE LATEST WSR-88D RADAR MOSAIC HAD THE AREA OF PRECIPITATION 
ASSOCIATED WITH THE SHORTWAVE TROF FROM MINNESOTA INTO WISCONSIN AND 
ILLINOIS...WITH EVEN A FEW LIGHTNING STRIKES SHOWING UP OVER 
SOUTHERN WI AND NORTHERN IL. SATELLITE IMAGERY AND METARS SHOWED A 
HEALTHY AREA OF LOW CLOUDS AND AT 3PM FOG WAS STILL REDUCING 
VISIBILITIES TO 1 TO 3 MILES WITH SOME PATCHY DENSE FOG AT BEATRICE. 
TEMPERATURES WERE IN THE 30S NORTH AND IN THE 40S SOUTH AND TO THE 
WEST WHERE CIGS WERE HIGHER.

TONIGHT WILL NEED TO SEE HOW THE WINDSHIFT MOVING THROUGH AFFECTS 
THE WINDS AND THE DEWPOINTS.  DEEP MOISTURE IS IN PLACE AND ALTHOUGH 
THE WIND SHIFT COULD PROVIDE SOME DRYING...THE LOW LEVEL MOISTURE 
DOES NOT APPEAR TO GET SCOURED OUT AND THE FLOW WEAKENS AFTER 06Z.  
RAP/NAM/HRRR SHOWING POTENTIAL FOR WIDSPREAD DENSE FOG DUE TO THE
WEAK FLOW AND HIGH DEWPOINTS. IN ADDITION...SOME LOCATIONS MAY BE
BELOW FREEZING/LOW DEWPOINT SPREADS COULD CREATE SOME RIMING ON
SURFACES. BASED ON THE ABOVE AND THE TIME OF YEAR...HAVE DECIDED
TO GO WITH A DENSE FOG ADVISORY FM 03Z-16Z FOR MUCH OF THE
FORECAST AREA AND CAN ADJUST AS NEEDED TONIGHT. LOWS TONIGHT
SHOULD RANGE FROM AROUND 30 NORTH TO NEAR 40 SOUTH.

AT MIDDAY...THE MAIN LONG WAVE TROF WAS OVER THE WESTERN U.S.
WITH SOUTHWEST FLOW ALOFT INTO THE CENTRAL PART OF THE COUNTRY.
THE SURFACE WIND SHIFT HAS MADE IT INTO NW MISSOURI AND RETURN
FLOW IS BEGINNING TO SET UP IN THE WESTERN PLAINS. DURING THE DAY
MONDAY...SURFACE LOW STRENGTHENS AND VERY WARM H85 TEMPS ARE DRAWN
BACK NORTHWARD INTO NEBRASKA. THE LINGERING LOW CLOUDS AND FOG
NORTH OF THE FRONT AND THE WARM FRONT WILL MAKE MONDAY/S HIGHS
QUITE A CHALLENGE. FOR NOW HAVE MOST LOCATIONS IN THE
40S...WITH 50S AND 60S ACROSS SOUTHEAST NEBRASKA INTO SOUTHWEST
IOWA. THE NAM IS HINTING AS SOME LIGHT PRECIPITATION WITH THE
STRONG WARM AIR ADVECTION MONDAY AND MONDAY NIGHT AND DO HAVE SOME
SMALL CHANCES IN THERE. A STRONG 55KT JET NOSING INTO MISSOURI MONDAY
NIGHT COULD SPARK SOME TSRA...HOWEVER THESE APPEAR TO BE SOUTH OF
THE FORECAST AREA. MEANWHILE...THE LONGWAVE TROF MOVES INTO THE
PLAINS AND HAS A COLD FRONT...DECENT MID LEVEL FRONTOGENESIS AND
STEEP LAPSE RATES WITH IT. CONTINUE A SMALL CHANCE FOR RAIN IN
THE NORTH MONDAY AFTERNOON...THEN RAIN OR SNOW CHANGING TO SNOW
IN THE NORTH WHERE A BAND OF LIGHT SNOW COULD SET UP MONDAY INTO
TUESDAY. THE LIFT SEEMS TO WEAKEN DURING THE DAY TUESDAY...HOWEVER
THIS WILL NEED TO BE ASSESSED WITH EACH SHIFT. REINFORCING COLD
AIR ARRIVES TUESDAY NIGHT INTO WEDNESDAY AND DO MENTION FLURRIES
WITH THE ARCTIC AIRMASS AND COLDER HIGHS IN THE TEENS/20S/30S.

ZAPOTOCNY

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY. 

AS THE UPPER LEVEL FLOW TURNS NORTHWEST EARLY IN THE PERIOD AN 
ARCTIC COLD FRONT WILL MOVE THROUGH THE CWA ON WED NIGHT. THIS WILL 
LEAD TO SEASONABLY COLD AIR TO FILTER INTO THE AREA FOR A SHORT 
TIME. THE COLD AIR WILL CONTINUE TO BE MODIFIED BY THE LACK OF SNOW 
COVER ACROSS THE FA AND THUS THE GOING FORECAST OF HIGHS IN THE 
TEENS AND LOWS IN THE SINGLE DIGITS ABOVE ZERO SEEM REASONABLE. THE 
COLDEST MORNING IS LIKELY TO BE FRI MORNING AS THE SURFACE HIGH 
PRESSURE RIDGE SHIFTS ACROSS THE FA. THE COLD WEATHER WILL BE SHORT-
LIVED HOWEVER AS THE UPPER LEVEL RIDGE TO THE WEST STARTS TO EXPAND 
EASTWARD ON FRI ALLOWING FOR A WARM FRONT TO MOVE THROUGH...AND A 
COMBINATION OF PACIFIC AIR AND DOWN-SLOPE FLOW WILL WARM 
TEMPERATURES BACK ABOVE NORMAL. THE GLOBAL MODELS ARE IN DECENT 
AGREEMENT THAT A BACK-DOOR COLD FRONT WILL ATTEMPT TO WORK INTO THE 
AREA LATE SAT THAT MAY LEAD TO A BIT OF COOLING IN THE NORTH AND 
EAST FOR SAT NIGHT...BUT THIS FRONT SHOULD LIFT QUICKLY BACK OUT OF 
THE AREA WITH CONTINUED ABOVE NORMAL HIGHS FOR SUNDAY. 

BOUSTEAD

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...DENSE FOG ADVISORY UNTIL 10 AM CST MONDAY FOR NEZ011-012-015>018-
     030>034-042>045-050>053-065>068-078-088>093.

IA...DENSE FOG ADVISORY UNTIL 10 AM CST MONDAY FOR IAZ043-055-056-069-
     079-080-090-091.

&&

$$