FXUS63 KOAX 191524
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
924 AM CST SUN DEC 19 2010
.UPDATE...
UPDATED FOR WEATHER TRENDS.
&&
.DISCUSSION...
UPDATED FOR WEATHER TRENDS AS A SNOW BAND MOVES ACROSS THE CWA. WV
IMAGERY AND 1.5 PVU PRESSURE ANALYSIS INDICATE A SHORTWAVE IS
DROPPING THROUGH SD...AND ENHANCEMENT IN SNOW BAND IN NWRN IA/SERN
SD IS LIKELY A RESULT OF THE APPROACHING WAVE. BAND IS SLIDING
EAST PROGRESSIVELY...AND HAVE CLEARED MEASURABLE POPS IN THE WRN
CWA...WITH A FLURRY MENTION LINGERING THIS MRNG. WILL NEED TO
WATCH THE AREA FOR FZDZ LATER TODAY...BUT KEPT MENTION OUT FOR
NOW. CONTINUED OVERCAST SKIES THROUGH THE DAY AS WELL...WITH LOW-
LEVEL RH LOCKED IN AND WEAK WINDS NOT ALLOWING MIXING. ALSO
TWEAKED TEMPS TO LOWER A TOUCH IN THE SRN CWA...DESPITE WARMER
START IN THE UPPER 20S...AS HEATING WILL BE MINIMAL UNDER OVERCAST
SKIES AND SHORT DAYLIGHT.
UPDATED GRIDS/ZFP ALREADY SENT.
&&
.PREV DISCUSSION... /ISSUED 337 AM CST SUN DEC 19 2010/
DISCUSSION...
PRECIPITATION CHANCES AND TYPES OVER THE NEXT COUPLE OF DAYS ARE
THE PRIMARY FORECAST CONCERNS.
BAND OF LIGHT SNOW WAS DRIFTING EAST ACROSS SOUTHEAST NEBRASKA THIS
MORNING IN AREA OF ISENTROPIC UPGLIDE AHEAD OF WEAK MID LEVEL WAVE
MOVING EAST THROUGH NORTHERN NEBRASKA. MORE LIGHT SNOW WAS NOTED
NEAR THIS WAVE IN NORTH CENTRAL NEBRASKA. BOTH AREAS SHOULD CONTINUE
MOVING EAST ACROSS OUR CWA THIS MORNING...BUT INTENSITY WILL REMAIN
QUITE LIGHT FOR THE MOST PART AND SHOULD MOVE TO THE EAST IN THE
AFTERNOON. ADDITIONAL SNOW AMOUNTS ARE EXPECTED TO BE LESS THAN AN
INCH.
THE NEXT SYSTEM TO AFFECT OUR AREA WAS APPROACHING THE OREGON AND
NORTHERN CALIFORNIA COAST THIS MORNING AND WAS CLEARLY DEFINED ON
WATER VAPOR LOOPS. THIS LOW/WAVE WILL MOVE INTO THE PLAINS MONDAY
AFTERNOON USHERED EAST BY 150KT UPPER JET. STRONG FLOW AND DPVA WILL
INDUCE LOWERING SURFACE PRESSURE IN THE HIGH PLAINS...WHICH IN TURN
WILL INCREASE LOW LEVEL WARM ADVECTION ACROSS MUCH OF MID AMERICA.
ISENTROPIC UPGLIDE REALLY INTENSIFIES AFTER MIDNIGHT TONIGHT AS LOW
LEVEL JET EXCEEDS 35KTS. HOWEVER FORECAST SOUNDINGS AND LAYER
HUMIDITY AND CONDENSATION VAPOR PRESSURE PROGS SUGGEST SATURATION
FOR PRECIPITATION WILL FOCUS WELL NORTH OF OUR CWA. MAJORITY OF
MODELS HAVE BEEN CONSISTENT WITH THIS NORTHERN TRACK...AND THE
FARTHEST SOUTH SOLUTIONS OF THE GFS HAVE BEEN DRIFTING NORTH WITH
EACH SUCCESSIVE RUN OVER THE PAST COUPLE OF DAYS. THUS HAVE BOUGHT
THE TREND THIS MORNING AND REDUCED POPS ACROSS THE CWA FOR THIS
EVENT. WILL HAVE SLIGHT CHANCES FOR SNOW IN NORTHEAST NEBRASKA BY
MIDNIGHT...WITH THAT SPREADING SOUTHEAST TOWARD INTERSTATE 80 BY
MONDAY MORNING. WARM AIR SURGING NORTH WILL PLAY HAVOC WITH
PRECIPITATION TYPES AFTER 12Z...BUT PRECIP SHOULD BE LIFTING NORTH
AT THE SAME TIME. SOUNDINGS AND PARTIAL THICKNESS PROGS SHOW A
MIX ACROSS ALL THE CWA BY NOON MONDAY. BEST CHANCE FOR
ACCUMULATING SNOW WILL BE IN THE NORTHEAST CWA WHERE MAYBE AN INCH
OR SO OF SNOW COULD ACCUMULATE BEFORE SWITCHING OVER. ENDING
PRECIP LOOKS QUICKER THAN EARLIER RUNS WITH SURFACE LOW PUSHING
EAST BY LATE MONDAY AFTERNOON. SO WILL NOT CONTINUE PRECIP PAST
MONDAY AFTERNOON.
NEXT CHANCE FOR PRECIP COMES WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
WITH STRONG SHORTWAVE DROPPING INTO THE REGION. GFS AND ECMWF HAVE
BEEN PRETTY CONSISTENT WITH THIS FEATURE...SO HAVE NUDGED POPS UP A
BIT. MENTION OF SNOW NORTH AND RAIN OR SNOW SOUTH STILL LOOKS
OKAY...BUT COLD AIR SLIPPING UNDER WARMER TEMPS ALOFT SUGGESTS
ANOTHER MIX OR FREEZING RAIN EPISODE IS POSSIBLE. WILL HAVE TO FINE
TUNE THIS ONE WITH TIME.
TEMPERATURES TODAY AND MONDAY WILL REBOUND INTO THE 30S WITH SOME
40S POSSIBLE SOUTH ESPECIALLY MONDAY AS MIXING INCREASES BEHIND
EXITING SYSTEM. COOLER 20S ARE FORECAST ON TUESDAY BEHIND
SYSTEM...THEN 30S WEDNESDAY AND THURSDAY BEFORE DRASTIC COOL DOWN
LATE IN THE WEEK BEHIND STRONG THURSDAY SYSTEM.
DERGAN
AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
SHARP DELINEATION IN CIGS ACROSS THE AREA EARLY THIS MORNING WITH
IFR CIGS AND VSBYS ORIENTED NW-SE JUST W AND S OF TAF SITES IN
850-700MB WARM ADVECTION ZONE. KLNK AND KOMA APPEAR TO HAVE BEST
CHANCE FOR A PERIOD OF IFR CONDITIONS NEAR AND AFTER 12Z. FORECAST
SOUNDINGS SUGGEST LIMITED PERIOD OF DENDRITIC LAYER SATURATION FOR
KLNK WHERE IT APPEARS BEST CHANCE OF A LITTLE LIGHT SNOW OR FLURRIES
TO PRODUCE MVFR VSBYS. OTHERWISE EXPECT VARIABLE CONDITIONS AFTER
18Z AS BETTER FORCING DEVELOPS WEST AND NORTH OF SITES.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
MAYES