FXUS63 KOAX 180826
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
326 AM CDT WED MAY 18 2011
.DISCUSSION...
THE MAIN CONCERNS THROUGH THE ENTIRE PERIOD WILL CONTINUE TO BE
THE TIMING OF THE PRECIPITATION AND TEMPERATURES.
THE OMEGA BLOCK OVER THE U.S. HAS WEAKENED WITH THE TWO LARGE
CLOSED MID TROPOSPHERIC LOWS OVER THE WESTERN AND EASTERN U.S.
BEGINNING TO BREAK DOWN THE RIDGE/MERGE. THROUGH THE WEEKENDED THE
WESTERN U.S. CLOSED LOW WILL MEANDER FROM OREGON TO UTAH...LIFTING
NORTH INTO WYOMING AND MONTANA...THEN SHIFTING EAST INTO THE
DAKOTAS SATURDAY AND MINNESOTA SUNDAY. THIS PATTERN WILL PRESENT
SEVERAL CHANCES FOR RAIN FROM NOW THROUGH SATURDAY.
DESPITE DEWPOINT TEMPERATURES ONLY IN THE 30S AND 40S...A BAND OF
RAIN WITH EMBEDDED THUNDERSTORMS PER THE WSR-88D MOSAIC HAS
DEVELOPED FROM NORTHWEST TO SOUTHEAST FROM WESTERN SOUTH
DAKOTA...THROUGH WEST CENTRAL NEBRASKA INTO CENTRAL KANSAS AND
OKLAHOMA. LOW LEVEL AND MID LEVEL WARM AIR ADVECTION IS UNDERWAY
AND THERE IS A NEGATIVELY TILTED SHORTWAVE TROUGH OVER WRN
NEBRASKA. IN ADDITION...THERE IS UPPER LEVEL SUPPORT RELATED TO
THE NOSE OF THE 100+KT JET AND RESULTANT UPPER LEVEL DIVERGENCE IN
WESTERN NEBRASKA. NORTH PLATTE/S SOUNDING WAS MOIST FROM H70 TO
H75. THE CONVECTION IS MOST INTENSE OVER SOUTH CENTRAL NEBRASKA
AND THE SHORT RANGE MODELS AT 06Z WERE PEGGING AN AREA A BIT
FARTHER TO THE NORTHWEST TO BE STRONGER...ALTHOUGH THE GENERAL
AREA OF THE PRECIPITATION WAS ON TRACK. THIS MORNING THE SHORTWAVE
WILL CONTINUE TO SWING NORTHEAST...MEANWHILE...THE MID LEVEL WARM
AIR ADVECTION WILL BE STRONGER TO THE WEST AND SOUTH. THE SHORT
RANGE MODELS (RUC/NAM/ECMWF/GFS) BRING THE PRECIPITATION INTO THE
WESTERN ZONES AND THEN WEAKEN IT. THIS SEEMS REASONABLE AS THE
OMEGA WEAKENS AFTER 12Z AND THE UPPER LEVEL SUPPORT WHILE STRONG
INITIALLY...WEAKENS AFTER 12Z AS WELL. HAVE BROUGHT LIKELY POPS
INTO THE WEST...THEN TREND DOWNWARD EAST WITH CHC AND THEN SLIGHT
CHC AND DRY FROM THE MISSOURI RIVER EASTWARD.
THIS AFTERNOON AND TONIGHT...THE THETA-E ADVECTION INCREASES OVER
KANSAS AND SPREADS NORTHWARD INTO NEBRASKA AND SOUTHWEST
IOWA...MEANWHILE SFC LOW PRESSURE DEEPENS OVER EASTERN COLORADO
AND THE LOW LEVEL JET STRENGTHEN ACROSS KANSAS INTO NEBRASKA. MUCH
DEEPER MOISTURE IS PULLED NORTHWARD. WILL HAVE SOME CHC POPS IN
THIS AFTERNOON...BUT THINK THERE WILL BE A BETTER CHANCE LATER
TONIGHT ACRS THE SOUTH.
THE COMPLEX STORM SYSTEM OVER COLORADO WILL CONTINUE TO PROVIDE
PERIODS OF SHOWERS AND THUNDERSTORMS THURSDAY AND THURSDAY NIGHT.
THE MORE ORGANIZED PRECIPITATION SHOULD LIFT NORTH FRIDAY AS THE
CLOSED LOW LIFTS NORTH INTO WYOMING. THE MODELS (NAM/GFS/ECWMF)
ALL SUGGEST SHORTWAVE TROUGH ENERGY LIFTING NORTH DURING FRIDAY
AFTERNOON AND FRIDAY NIGHT AND THIS INTENSIFIES THE SHOWER AND
THUNDERSTORM COVERAGE ACROSS THE FORECAST AREA. SEVER WEATHER
WISE...THE MU CAPE IS GENERALLY 500J/KG OR LESS THRU
THURSDAY...AND THEN INCREASES THURSDAY NIGHT THRU FRIDAY EVENING
TO 1000-3000J/KG. THE LOW LEVEL AND DEEP LAYER SHEER ARE FAVORABLE
FOR MOST OF THE TIME THUNDERSTORMS ARE EXPECTED. THUS...UPDRAFTS
MAY NOT BE AS SUSTAINABLE FOR SEVERE STORMS EARLY ON...WITH A
BETTER CHANCE FOR SEVERE STORMS WHEN THE INSTABILITY IS GREATER.
THE STORM PREDICTION CENTER HAS PARTS OF THE AREA IN THE GENERAL
THUNDER FOR THE DAY 1 OUTLOOK AND THE SOUTHWEST CORNER OF THE
FORECAST AREA IN THE DAY 2 SLIGHT RISK OUTLOOK AND MUCH OF THE
SRN TWO THIRDS OF THE AREA FOR DAY3 SLIGHT RISK OUTLOOK. THIS
SEEMS TO FIT WITH THE ABOVE MENTIONED BETTER PERIODS OF
INSTABILITY.
ALTHOUGH WE ARE STARTING OUT DRY WITH PRECIPITABLE WATER AROUND .5
INCH...THIS WILL INCREASE TO 1.5 INCHES THURSDAY AND REMAIN HIGH
THROUGH SATURDAY MORNING. THROUGH SATURDAY MORNING...SOME SPOTS
MAY PICK UP 1 TO 3 INCHES OF RAIN.
ALTHOUGH WE MAY GET A BREAK IN THE WEATHER LATER IN THE
WEEKEND...IT STILL LOOKS LIKE A WET PATTERN FOR EARLY NEXT WEEK.
TEMPERATURES ARE EXPECTED TO BE CLOSES TO NORMAL FRIDAY THRU WEDNESDAY.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
A NW TO SE LINE OF CONVECTION THAT EXTENDED FROM SW NEBRASKA INTO
CENTRAL KS EARLY WEDNESDAY WILL CONTINUE WORKING EWD TODAY BUT IS
EXPECTED TO WEAKEN AS IT MOVES INTO ERN NEBRASKA. HOWEVER...AS
PRECIP AREA SHIFTS EWD...MID LEVEL MOISTURE WILL BE INCREASING AND
THIS SHOULD BRING CEILINGS TO KLNK/KOFK THIS AFTERNOON AND TO KOMA
BY EVENING. CURRENT INDICATIONS ARE THAT ANY CEILINGS SHOULD REMAIN
ABOVE 4K FT TODAY. WITH LOW LEVEL DRY AIR IN PLACE INTO THIS
EVENING...NO MENTION OF PRECIP WAS MADE AT TAF SITES WITH 18Z/06Z
TAF ISSUANCE. THAT SAID...SOME LIGHT PRECIP CAN NOT BE RULED OUT AT
KLNK/KOFK AFT 18/21Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
ZAPOTOCNY/CHERMOK