Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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125
FXUS63 KOAX 221141
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
641 AM CDT FRI MAY 22 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 311 AM CDT FRI MAY 22 2015

...TIMING WET AND DRY PERIODS IS THE MAIN CHALLENGE...

LARGE SCALE PATTERN OVER NORTH AMERICA CONTINUES TO INCLUDE THE
BLOCKY RIDGE EXTENDING INTO NORTHWEST CANADA/ALASKA WITH SLOW
MOVING CLOSED LOWS AND SHORTWAVES DRIFTING SOUTH OF THE POSITIVE
HEIGHT ANOMALY AND INTO THE WESTERN US. THIS FLOW PATTERN IS
CONDUCIVE TO TRANSPORTING HIGH AMOUNTS OF WATER VAPOR FROM THE SUB
TROPICS INTO THE SOUTHERN US AND POTENTIALLY INTO THE PLAINS AND
ROCKIES. HOWEVER...RESIDUAL SURFACE HIGH PRESSURE IS CURRENTLY
ENTRENCHED OVER THE CENTRAL PLAINS REGION WITH A DRY AIRMASS IN
PLACE.

SENSIBLE WEATHER FROM THIS PATTERN WILL BE PERIODS OF FAIRLY
LIGHT RAIN THAT IS GENERATED BY THE SHORTWAVES TO OUR WEST AND
MOISTURE ADVECTION FROM THE SOUTH...BUT A THERMODYNAMICALLY STABLE
AIRMASS WILL LIMIT THUNDER POTENTIAL AND KEEP RAINFALL SOMEWHAT
LIGHT. THE CHALLENGE IS DETERMINING THE MOST LIKELY PERIODS OF
RAIN AND THE DRY GAPS BETWEEN THEM.

FIRST ROUND SHOULD BE TIED TO A WELL DEFINED SHORTWAVE CURRENTLY
MOVING THROUGH COLORADO PER WATER VAPOR LOOP. THERE IS ALREADY A
LARGE AREA OF RAIN ASSOCIATED WITH THIS FEATURE FROM COLORADO EAST
AND SOUTH WITH LEADING EDGE NEAR DODGE CITY...MOVING THIS
DIRECTION. INITIALLY THE DRY AIR IN PLACE OVER THE FORECAST AREA
WILL LIMIT RAIN UNTIL AIR BECOMES MORE SATURATED. MIGHT BE CLOSER
TO THIS EVENING BEFORE MOST OF THE AREA SEES RAIN REACHING THE
GROUND.

FRIDAY NIGHT INTO SATURDAY SHOULD BE PERIODS WITH THIS RAIN
MOVING THROUGH. BY EARLY SUNDAY MOST MODELS ARE IN AGREEMENT THAT
THE MAIN UPPER LOW WILL DRIFT NORTH THROUGH COLORADO AND
WYOMING...WHICH WILL PULL A DRY SLOT INTO THE PLAINS. IF THIS
HAPPENS...THE BULK OF THE RAIN SHOULD END FOR SUNDAY...ESPECIALLY
FOR NEBRASKA COUNTIES. IOWA COUNTIES MAY STILL SEE LINGERING
LIGHT SHOWERS MOVE THROUGH ON SUNDAY. AGAIN...MAINLY LIGHT RAIN IS
EXPECTED WITH RAINFALL TOTALS UNDER AN INCH FOR THE WEEKEND...AND
ALTHOUGH SOME ISOLATED THUNDERSTORMS MAY BE POSSIBLE...MUCH OF
THIS RAIN SHOULD BE SANS THUNDER.

SATURDAY TEMPERATURES SHOULD BE COOL WITH RAIN IN THE AREA...BUT
SUNDAY HIGHS WILL BE WARMER IF THE DRY SLOT BRINGS MORE SUNSHINE.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 311 AM CDT FRI MAY 22 2015

MONDAY THERE IS REASONABLY GOOD MODEL AGREEMENT ON THE POSITION OF
THE UPPER LOW NEAR THE SOUTH DAKOTA-MONTANA BORDER AREA...BUT
DISAGREEMENT ON QPF. ALL MODELS HINT AT SOME QPF DURING THE WEEK
AS MORE SHORTWAVES MOVE THROUGH THE PLAINS...SO WILL MAINTAIN THE
CHANCE FOR RAIN MONDAY AND INTO THE WEEK. LOWER CHANCES APPEAR TO
BE TUE AND WED SO REDUCED POPS A BIT THOSE DAYS.

&&

.AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 630 AM CDT FRI MAY 22 2015

VFR CONDITIONS ARE LIKELY THROUGH THE TAF PERIOD. CLOUDS WILL
INCREASE IN COVERAGE...WITH LOWERING CEILINGS THROUGHOUT THE
PERIOD. CEILINGS CLOSER TO 12Z MAY COME CLOSE TO HIGH-END MVFR
THRESHOLDS...BUT KEPT THEM AT VFR FOR NOW. ALSO COULD BE A PERIOD
OF RAIN AT ALL SITES MAINLY AFTER 00Z...BUT GIVEN LOWER
CONFIDENCE IN COVERAGE...HAVE OPTED TO KEEP MENTION OUT FOR NOW.
WINDS WILL INCREASE FROM LIGHT AND VARIABLE TO SOUTHWEST AT AROUND
10KT...THEN BACK TO SOUTHEASTERLY TONIGHT.

&&

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

$$

SHORT TERM...NIETFELD
LONG TERM...NIETFELD
AVIATION...MAYES



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