FXUS63 KOAX 102029
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
329 PM CDT TUE MAY 10 2011
.SHORT TERM...TONIGHT LOW CONFIDENCE IN FORECAST OVERNIGHT...WITH
SHOWERS AND THUNDERSTORMS POSSIBLE BUT BY NO MEANS CERTAIN.
SUBJECTIVE 12Z UPPER AIR ANALYSIS INDICATES MAIN UPPER LOW
CENTERED IN SOUTHWEST UT/NORTHEAST AZ...WITH EJECTING LOW SEGMENT
IN NORTHEAST WY/SOUTHEAST MT. CENTRAL PLAINS REMAINS IN
SOUTHWESTERLY MID- AND UPPER-LEVEL FLOW. 850MB LOW AT 12Z WAS
CENTERED IN NORTH CENTRAL SD...WITH COLD FRONT TRAILING THROUGH
CENTRAL NEB/WESTERN KS AND SOUTHWESTWARD. MOISTURE WAS FLOWING OFF
THE GULF OF MEXICO INTO TX/OK...AND MOISTURE HAD POOLED AHEAD OF
THE 850MB LOW FROM NEB/DAKOTAS EAST INTO THE GREAT LAKES. SURFACE
LOW AT 19Z WAS CENTERED IN SOUTHEAST CO...WITH ANOTHER LOW IN
SOUTHWEST ND ASSOCIATED WITH THE EJECTING LEAD WAVE. NEARLY
STATIONARY FRONT EXTENDED FROM THE SD/MN BORDER THROUGH EASTERN
NEB /FROM KLCG TO KHJH/ AND SOUTHWESTWARD TOWARD THE CO LOW. EAST
OF THAT BOUNDARY...TEMPERATURES AGAIN HAVE JUMPED INTO THE LOWER
TO MID 90S...WITH DRY DEWPOINTS MIXING EASTWARD FROM THE BOUNDARY
AS MIXING DEEPENS. WEST OF THAT BOUNDARY...TEMPERATURES WERE IN
THE 80S...WITH DRIER DEWPOINTS THROUGHOUT THE DAY.
MAIN FORECAST CONCERN IS WHETHER STORMS WILL DEVELOP THIS
EVENING...AND WHETHER MORE WIDESPREAD PRECIP WILL DEVELOP
OVERNIGHT. MODELS ARE PROVIDING A RATHER LARGE ENVELOPE OF
SOLUTIONS...FROM THE HRRR/RUC THAT KEEPS THE CWA DRY THROUGH AT
LEAST 12Z...TO THE 4KM WRF THAT POPS A FEW THUNDERSTORMS IN THE
EVENING THAT DISSIPATE BY 06Z AND HAS NO PRECIP 06-12Z...TO THE
ECMWF THAT HAS NO CONVECTION PRIOR TO 06Z BUT DEVELOPS WIDESPREAD
PRECIP ALONG THE BOUNDARY FROM 06-12Z...TO THE GFS/NAM OPERATIONAL
RUNS THAT HAVE BOTH EVENING STORMS AND OVERNIGHT FRONTAL
PRECIP...AND TO THE SREF THAT INCLUDES MEMBERS THAT FOLLOW VIRTUALLY
ALL OF THESE SCENARIOS. IN SHORT...CONSIDERABLE UNCERTAINTY
TONIGHT. HAVE LOWERED POPS TONIGHT BEFORE 06Z...AS ANY STORMS THAT
CAN DEVELOP LIKELY WILL BE ISOLATED TO SCATTERED. THINK DEEP-LAYER
SHEAR IS TOO WEAK TO SUPPORT SEVERE CONVECTION...THOUGH WITH STEEP
700-500MB LAPSE RATES IN THE AREA THIS EVENING...WOULD NOT BE
SURPRISED BY AN ISOLATED NEAR-SEVERE HAILER. THINK THAT THIS
ACTIVITY /IF IT DOES DEVELOP/ WILL INDEED WEAKEN BY AROUND 06Z AS IT
LIFTS NORTHEASTWARD INTO NORTHWEST IOWA. SECOND WAVE OF PRECIP IS
PROGGED AS THE LOW-LEVEL JET IMPINGES ON THE BOUNDARY IN THE LATE
OVERNIGHT HOURS /06-12Z/. INCREASES POPS HERE TO CHANCE CATEGORY IN
THE NORTHERN CWA...BUT STILL HAVE LOW CONFIDENCE IN PRECIP
DEVELOPMENT AND...SHOULD IT DEVELOP...ITS EXTENT. BUMPED UP
OVERNIGHT TEMPS IN THE WARM SECTOR AS TEMPS STRUGGLED TO FALL BELOW
70F LAST NIGHT...THOUGH DID KNOCK A COUPLE OF DEGREES OFF COMPARED
TO READINGS LAST NIGHT IN CASE AIR IS PRECIP-COOLED.
.LONG TERM...WEDNESDAY THROUGH TUESDAY.
SEVERAL ACTIVE WEATHER DAYS SHAPING UP FOR FORECAST AREA WEDNESDAY
AND THURSDAY FOLLOWED BY BLUSTERY AND COOLER WEATHER INTO THE
WEEKEND.
FOR WEDNESDAY/WEDNESDAY NIGHT...SOUTHERN TROUGH ENERGY STILL FORECAST
TO CLOSE-OFF OVER EASTERN COLORADO ON WEDNESDAY KEEPING AT LEAST
ONE BOUNDARY SOMEWHERE IN THE FORECAST AREA AS LOW LEVEL MOISTURE
BEGINS SPREADING NWWD TOWARD NWRN ZONES. A POSSIBLE COMPLICATING
BEGINNING TO THE DAY IS WHETHER OR NOT CONVECTION...ESPECIALLY
MORE WIDESPREAD CONVECTION...WILL BE ONGOING. 12Z OPERATIONAL
MODELS...ESPECIALLY NAM...INDICATED THIS SCENARIO...WHILE 4KM WRF
WAS MOSTLY ABSENT QPF. GIVEN TROUGH WILL STILL BE ORGANIZING
PRETTY FAR WEST OF US AND SURFACE CONVERGENCE WILL BE WEAK OPTED
TO LEAN MORE TOWARD A DRIER START TO THE DAY ALTHOUGH KEPT IN
SLIGHT CHANCE IN THE MORNING AS THERE WAS SOME CONVERGENCE NEAR
H85. BECAUSE OF EXPECTED LACK OF MORNING CONVECTION ALSO OPTED
TOWARD AND A BIT ABOVE HIGHER GUIDANCE VALUES FOR MAX TEMPS SERN
2/3RDS OR SO. COMBINATION OF HEATING AND FALLING UPPER HEIGHTS BY
LATE AFTERNOON SHOULD ENABLE CONVECTION TO DEVELOP WITH MAIN AREAS
LIKELY ALONG/NW OF SURFACE FRONT THAT SHOULD BE NEAR A COLUMBUS
TO WAYNE LINE IN THE AFTERNOON AND ALSO NEAR POSSIBLE SECOND
BOUNDARY/WARM FRONT NEAR KS BORDER. THUS KEPT HIGH POPS MOST
AREAS BUT TRIMMED BACK ECNTRL IA ZONES WHICH WILL BE FARTHER
REMOVED FROM EITHER BOUNDARY. IF EARLY DAY CONVECTION IS MORE
WIDESPREAD MANY ASPECTS OF FORECAST WILL NEED ADJUSTING. SEVERE
POTENTIAL REMAINS IN PLACE THROUGH THE EVENING WITH LOW LEVEL
BOUNDARIES IN THE VICINITY...0-6KM SHEAR INCREASING AND
INSTABILITY/CAPE MODESTLY HIGH. BUFKIT SOUNDINGS FROM NAM NOT MUCH
USE HOWEVER DUE TO CONTAMINATION FROM /POSSIBLY/ TOO MUCH EARLY DAY
PRECIP. GFS HODOGRAPHS MORE SUPPORTIVE...ALTHOUGH CAPPED THROUGH
06Z THURSDAY FARTHER REMOVED FROM NE TO SW FRONT THAT IT FORECAST
OVER NWRN FORECAST AREA.
AS UPPER LOW TRACKS INTO NCNTRL KANSAS BY LATE AFTERNOON
THURSDAY...GOOD AGREEMENT BETWEEN GFS/NAM/ECMWF IN THIS ASPECT...
EXPECT CLEARING/SOME DRYING AHEAD OF IT IN ERN 2/3RDS OR SO AND
TEMPERATURES WERE RAISED TOWARD THE WARM END OF GUIDANCE.
STRONG/SEVERE STORMS AGAIN POSSIBLE AS UPPER LOW APPROACHES...MOSTLY
NEAR AND EAST OF MISSOURI RIVER WHERE A BIT BETTER SURFACE-H85
MOISTURE/INSTABILITY WAS FORECAST...BUT ALSO POSSIBLY TIED CLOSER
TO UPPER LOW IF LOW LEVEL MOISTURE HANGS BACK A BIT MORE THAN
FORECAST.
SEVERAL BLUSTERY AND COOL DAYS THEN FRIDAY THROUGH SUNDAY WITH GFS
SUGGESTING A LOT OF CLOUDS EVEN ABSENT PRECIP...GENERALLY TRIMMED
BOTH MAX TEMPS AND MINS. LINGERING PRECIP FRIDAY...ESPECIALLY
EARLY ERN ZONES OTHERWISE LEFT WEEKEND DRY. GFS HAS CHANGED A BIT
IN DUMB-BELLING CURRENT WRN ND LOW BACK SOUTH ACROSS NEBRASKA ON
SUNDAY AS UPPER RIDGE BUILDS OVER CANADA. SINCE IT HAD LITTLE/NO
SUPPORT FROM 00Z GFS ENSEMBLE MEAN...AND 12Z ECMWF KEPT LOW WELL
TO OUR NORTH BEFORE BEING INGESTED BY LARGE WEST COAST LOW...WILL
NOT MENTION PRECIPITATION ON SUNDAY. HOWEVER...WILL KEEP
TEMPERATURES COOL ALLOWING FOR SOME GFS-TYPE INFLUENCE SINCE IT
WAS NOTED GEM WAS SIMILAR IN DROPPING LOW SWD OVER NEBRASKA.
MODERATING TEMPERATURES STILL ON TRACK MON/TUESDAY PER 12Z ECMWF
AND 00Z GFS ENSEMBLE MEAN...MORE SO THAN 12Z GFS WHICH WAS NOT
ACCEPTED JUST YET IN EXTENDED PERIODS DUE TO ITS CHANGE FROM
EARLIER RUNS AND GENERAL LACK OF SUPPORT FROM EARLIER MEAN.
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
LOW CONFIDENCE FORECAST...ESPECIALLY AFTER AROUND 03Z. THINK A FEW
THUNDERSTORMS MAY DEVELOP IN EASTERN NEB...WITH KLNK MOST LIKELY OF
THE TAF SITES TO BE NEAR STORMS. EVOLUTION OF STORMS THROUGH THE
NIGHT IS STILL VERY QUESTIONABLE...WITH POSSIBLE SOLUTIONS RANGING
FROM DRY TO A WIDE SWATH OF SHOWERS AND THUNDER POSSIBLY AFFECTING
KOFK/KOMA. FOR NOW...KEPT PRECIP AND THUNDER OUT OF TAFS. WINDS
ARE ALSO UNCERTAIN WITH A FRONT LINGERING IN THE AREA...THOUGH
SHOULD BE MAINLY NW TO NE AT KOFK AND SW TO SE AT KOMA/KLNK.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
SHORT TERM/AVIATION...MAYES
LONG TERM...CHERMOK