000
FXUS63 KOAX 221810
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
110 PM CDT WED MAY 22 2013

.AVIATION...
18Z TAFS FOR KOMA...KLNK...KOFK.

AREA EXPECTED TO REMAIN UNDER THE INFLUENCE OF CLOSED UPPER LOW
OVER NORTH CENTRAL IOWA THROUGH 06Z AS IT TRACKS SLOWLY SOUTHEAST
TOWARD THE OHIO VALLEY. MVFR CIGS ARE EXPECTED TO IMPROVE TO VFR
DURING THE 18Z-00Z PERIOD THEN RETURN TO MVFR AFTER 02Z AS WINDS
DIMINISH AND LOW LEVEL MOISTURE LINGERS THROUGH MUCH OF THE NIGHT.
DRIER AIR AND VFR CONDITIONS RETURN TO THE AREA AFTER 12Z AS
UPPER SYSTEM MOVES OFF AND HIGH PRESSURE BUILDS INTO THE UPPER
MIDWEST.

&&

.PREV DISCUSSION... /ISSUED 328 AM CDT WED MAY 22 2013/

.DISCUSSION...
COOL UPPER-LEVEL LOW CONTINUES TO ROAM ACROSS THE NORTHERN PLAINS.
SUBJECTIVE 00Z UPPER AIR ANALYSIS INDICATES UPPER LOW CENTERED IN
SOUTHEAST SD...WITH RIDGING OVER THE ROCKIES...AND AN UPPER-LEVEL
LOW COMING ASHORE IN THE PACIFIC NORTHWEST.  115KT UPPER-LEVEL JET
STREAK AHEAD OF THE LOW EXTENDED FROM CENTRAL OK THROUGH EASTERN NEB
TO NORTHEAST WI.  850MB LOW WAS CENTERED IN CENTRAL MN...WITH COLD
FRONT EXTENDING FROM THERE THROUGH CENTRAL IA/WESTERN MO/EASTERN OK.
COLD POCKET OF TEMPS COVERED MUCH OF THE DAKOTAS INTO NEB...WITH
COLDEST 850MB TEMP OF 4C AT KBIS/KRAP. HIGHER 850MB MOISTURE OF
8C+ WAS CONFINED TO AREAS AHEAD OF THE COLD FRONT AND SOUTH OF THE
WARM FRONT...THOUGH TEMPERATURE/DEWPOINT SPREADS WERE AT OR BELOW
A DEGREE FROM EASTERN NEB THROUGH THE DAKOTAS AND MN. NOT
SURPRISINGLY...EXTENSIVE STRATUS DECK COVERS THE AREA AT 07Z...
WITH SPOTTY SPRINKLES OR LIGHT SHOWERS IN EASTERN SD/NORTHEAST
NEB/NORTHWEST IA/SOUTHERN MN.

MAIN FORECAST CONCERNS INCLUDE COOL TEMPERATURES AND SHOWERS
TODAY...THEN A PERIOD OF MILD WEATHER BEFORE ACTIVE PATTERN RETURNS
FOR THE WEEKEND.  LINGERING IMPACTS OF UPPER-LEVEL LOW TODAY INCLUDE
COLD AIR ADVECTION...STRATUS...AND OCCASIONAL SPRINKLES OR LIGHT
SHOWERS...AS THE LOW IS IN NO HURRY TO EXIT THE AREA.  HAVE GONE
MORE PESSIMISTIC WITH SKY COVER ALL THE WAY THROUGH TONIGHT...AS
AREA REMAINS IN SATURATED CYCLONIC FLOW.  ALSO COOLED TEMPS A BIT
FOR TODAY AS TEMPERATURES SHOULD STRUGGLE TO RISE UNDER CLOUDY SKIES
AND COLD AIR ADVECTION.  DO THINK POTENTIAL FOR SHOWERS WILL
DIMINISH THIS AFTERNOON AS LOW BEGINS TO PULL AWAY...BUT IN THE
MEANTIME...HAVE INCLUDED ISOLATED TO SCATTERED SHOWERS ACROSS THE
AREA. SKIES SHOULD CLEAR ON OR AROUND THURSDAY MORNING...BUT
EASTERLY LOW-LEVEL FLOW WILL NOT AID WARMING MUCH...AND HAVE SHAVED
A COUPLE DEGREES OFF THE TEMPERATURE FORECAST FOR THURSDAY.  QUIET
WEATHER WILL CONTINUE INTO THURSDAY NIGHT AS LOW-LEVEL JET FOCUSES
WELL SOUTHWEST OF THE AREA...THOUGH A FEW CLOUDS MAY START TO SNEAK
INTO THE SOUTHWEST CWA.

WARM AIR ADVECTION WILL COMMENCE ON FRIDAY...WITH UPPER-LEVEL RIDGE
BECOMING ESTABLISHED OVER THE CENTRAL PLAINS...AND SOUTHERLY 850MB
WINDS BRINGING WARM/MOIST AIR ADVECTION INTO THE AREA.  SHOULD SEE
SHOWERS DEVELOP DURING THE DAY UNDER WARM AIR ADVECTION AND
ISENTROPIC LIFT...THOUGH DID KEEP THUNDER MENTION OUT OF THE MORNING
WITH ONLY ISOLATED MENTION IN THE AFTERNOON AS SOUNDINGS LOOK RATHER
STABLE AND SREF INDICATES LITTLE OR NO MUCAPE.  BY LATE
EVENING/OVERNIGHT...BETTER INSTABILITY SHOULD BEGIN TO SLIP INTO THE
CWA...WITH SHOWERS LIKELY TO CONTINUE THROUGH FRIDAY NIGHT.

FROM SATURDAY THROUGH WEDNESDAY...FORECAST UNCERTAINTY INCREASES.
UPPER-LEVEL RIDGE WILL SLOWLY FLATTEN THROUGH THE WEEKEND...THEN
SLIDE EASTWARD EARLY IN THE WORK WEEK...ALLOWING SOUTHWESTERLY UPPER-
LEVEL FLOW ACROSS THE CENTRAL US.  THE SPEED OF THIS TRANSITION
VARIES AMONG MODELS AND MODEL RUNS...AND ALSO...THE TIMING OF
TRANSIENT WAVES AROUND THE RIDGING AND THROUGH THE SOUTHWESTERLY
FLOW ALSO VARIES FROM MODEL TO MODEL.  OVERALL...THE PERIOD APPEARS
ACTIVE...BUT DETERMINING WHICH PERIODS WILL BE MORE LIKELY TO SEE
SHOWERS AND THUNDERSTORMS IS A LITTLE HIT OR MISS RIGHT NOW.  THINK
THAT EARLY IN THE PERIOD...DEVELOPMENT MAY FOCUS IN THE HIGH
PLAINS...WITH MORE OF A NOCTURNAL STORM THREAT AS CONVECTION MOVES
OFF THE HIGH PLAINS.  AS THE PATTERN TRANSITIONS...THE DEVELOPMENT
REGION WOULD TRANSITION EASTWARD...WITH A LATE AFTERNOON/EVENING
THUNDERSTORM RISK AND LIKELY A GREATER RISK FOR SEVERE WEATHER.
FOR NOW...HAVE PAINFULLY KEPT SLIGHT CHANCE TO CHANCE POPS
SPRAYED THROUGHOUT THE EXTENDED FORECAST.

MAYES

&&

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

$$

FOBERT