FXUS63 KOAX 292152
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
352 PM CST SAT JAN 29 2011
.SHORT TERM...TONIGHT THROUGH TUESDAY.
SEVERAL CONCERNS IN THE SHORT TERM AS A PROLONGED SNOW EVENT WILL
BRING PERIODS OF LIGHT SNOW TO THE FORECAST AREA STARTING IN THE
NORTH MONDAY NIGHT AND SPREADING ACROSS THE FORECAST AREA MONDAY
THROUGH TUESDAY NIGHT. IN ADDITION THERE MAY BE A MIX EARLY ON OF
SLEET OR FREEZING DRIZZLE OR FREEZING RAIN IN THE SOUTH EARLY
MONDAY BEFORE CHANGING TO SNOW.
AT MIDDAY...THE MID TROPOSPHERIC WEATHER PATTERN HAD A SHORT-WAVE
TROUGH MOVING ACROSS SOUTH DAKOTA INTO IOWA WITH A BAND OF LIGHT
SNOW ASSOCIATED WITH THE UPWARD VERTICAL MOTION AND MID LEVEL WARM
AIR ADVECTION. MEANWHILE ARCTIC HIGH PRESSURE WAS BUILDING IN WITH
MUCH COLDER TEMPERATURES IN THE SINGLE DIGITS AND TEENS ACROSS THE
DAKOTAS. TEMPERATURES THIS AFTERNOON WERE IN THE 20S IN THE NORTH
AND CLOSE TO 40 IN THE SOUTH. ALTHOUGH CLOUDS COVERED MUCH OF SOUTH
DAKOTA...THEY WERE MORE VARIABLE IN EASTERN NEBRASKA AND SOUTHWEST IOWA.
TONIGHT AND SUNDAY...SHALLOW COLD AIR WILL CONTINUE TO PUSH SOUTHWARD
TONIGHT AND COULD SEE SOME FLURRIES IN THE BOUNDARY LAYER.
ALTHOUGH THE CLOUDS WILL BE VARIABLE...WILL MENTION MOSTLY CLOUDY
OVERNIGHT. LOW TEMPERATURES SHOULD DROP BACK INTO THE SINGLE
DIGITS NORTH TO TEENS SOUTH. SUNDAY...HIGH PRESSURE WILL CONTINUE
TO DOMINATE THE FORECAST WITH SOME VARIABLE CLOUDS. HIGHS WILL
ONLY TOP OUT IN THE TEENS AND 20S.
THE OVERALL LARGE SCALE PATTERN SHOWS A TRANSITION FROM NORTHWEST
FLOW ALOFT TO SOUTHWEST FLOW ALOFT SUNDAY EVENING AS SPLIT ENERGY
FROM A PAIR OF MID LEVEL TROUGHS (ONE NEAR MONTANA AND A SECOND
CLOSED OFF OVER SRN NEVADA) BEGIN TO MOVE EASTWARD. MONDAY...THE
TROUGH OVER MONTANA BECOMES DEEPER WHILE THE SRN TROF WEAKENS OVER
NEW MEXICO. SOME OF THE MODELS CLOSE THE 500 MILLIBAR LOW OVER
WYOMING (NORTH AMERICAN MESOSCALE MODEL) OR UTAH (EUROPEAN CENTRE
FOR MEDIUM RANGE FORECAST MODEL) (ECMWF)). WHILE THE GLOBAL
FORECAST SYSTEM MODEL (GFS) REMAINS OPEN AND TRY TO RETROGRADE IT
SOUTHWEST. ALL THREE OF THE MODELS TRANSLATE THE SOUTHERN STREAM
ENERGY AHEAD OF THE RETROGRADING TROUGH TUESDAY. ALL THREE MODELS
CLOSE THIS LEAD SHORTWAVE CLOSES OFF AT 500 MILLIBARS OVER ILLINOIS
BY 12 UNIVERSAL COORDINATED TIME (UTC) WEDNESDAY. AN AREA OF LIGHT
SNOW SHOULD DEVELOP NORTH OF OUR FORECAST AREA SUNDAY AND SHOULD
START TO MOVE INTO NORTHEAST NEBRASKA SUNDAY NIGHT.
MEANWHILE...AND INVERTED SURFACE TROUGH WILL DEVELOP NORTHWARD
FROM THE SURFACE LOW OVER NORTHEAST TEXAS...WITH 925 MILLIBAR AND
850 MILLIBAR FLOW INCREASING FROM THE SOUTH. THIS INCREASING LOW
LEVEL FLOW SHOULD MOISTEN UP THE LOW LEVELS MONDAY MORNING AND
THERE COULD BE SOME FREEZING DRIZZLE OR SLEET DEVELOP OVER
SOUTHEAST NEBRASKA. MONDAY THERE IS BROAD SYNOPTIC LIFT WITH THE
ATMOSPHERE BECOMING SATURATED OVER A LARGE DEPTH WITH LIGHT SNOW
DEVELOPING OVER THE FORECAST AND CONTINUING INTO MONDAY NIGHT AND
TUESDAY. ALTHOUGH THE SNOW AMOUNTS ARE MOSTLY LIGHT 1 TO 3 INCHES OVER
EACH 12HR PD...THEY CAN ADD UP OVER A 36 HOUR PERIOD. ANOTHER
FACTOR IS THAT THE SNOW RATIO INITIALLY WILL BE 10 OR 12:1...THEN
15 OR 20:1 BY TUESDAY. IN ADDITION NORTH WINDS ARE EXPECTED TO
STRENGTHEN TUESDAY INTO THE 20 TO 30KTS SUSTAINED RANGE AND THIS
WILL LEAD TO BLOWING SNOW. AT THIS TIME DO NOT HAVE ANY
HEADLINES...ALTHOUGH EXPECT TO CONTINUE TO HIGHLIGHT THIS STORM
SYSTEM IN THE HAZARDOUS WEATHER OUTLOOK AND WILL NEED TO CONSIDER
WATCH/ADVISORY POTENTIAL WITH FUTURE FORECASTS.
.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY.
WEATHER SYSTEM WILL BE DEPARTING THE REGION AT THE BEGINNING OF
THE PERIOD. HIGH PRESSURE MOVES IN BEHIND THE DEPARTING
LOW...WHICH WILL RESULT IN A VERY VERY COLD MORNING ON
WEDNESDAY...WITH READINGS 10 TO 15 BELOW IN NORTHEAST NEBRASKA.
WEDNESDAY SHOULD REMAIN VERY COLD WITH GENERALLY POOR MIXING AND A
FRESH SNOWPACK WITH COLD HIGH PRESSURE OVERHEAD... WITH HIGHS ONLY
IN THE SINGLE DIGITS. THE HIGH PRESSURE CENTER DOES SHIFT EASTWARD
THOUGH...WHICH COULD RESULT IN ANOTHER SUB ZERO NIGHT WEDNESDAY
NIGHT...WITH SLOWLY MODERATING TEMPERATURES THROUGH THE REMAINDER
OF THE WEEK AS WEST SOUTHWEST FLOW RETURNS. ANOTHER SURFACE TROUGH
APPEARS TO MOVE THROUGH THE REGION ON FRIDAY...WHICH SHOULD HELP
TO WARM THINGS A LITTLE MORE WITH A NORTHWESTERLY DOWNSLOPING
COMPONENT...BUT WILL KEEP THE FORECAST DRY AT THIS TIME AS BEST
FORCING AND MOISTURE APPEAR TO REMAIN TO THE NORTH ACROSS THE
DAKOTAS.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
MAIN AVN CONCERN IS PROLONGED LOW LEVEL CIGS SETTLING IN OVER
EASTERN NEB. AREA OF LOW LEVEL MOISTURE PRESENTLY CONCENTRATED OVER
THE DAKOTAS WILL QUICKLY SPREAD SOUTHWARD THIS AFTN WITH CIGS GOING
IFR AROUND 29/20Z...THEN PREVAILING THROUGH AT LEAST 30/12Z.
CEILINGS THEN IMPROVING A BIT AND EXPECT MVFR CIGS BETWEEN
30/12Z-18Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
ZAPOTOCNY/DEWALD/DEE