FXUS63 KOAX 190831
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
331 AM CDT FRI AUG 19 2011
.DISCUSSION...
MAIN CHALLENGES WITH THIS FORECAST DEAL WITH POTENTIAL FOR HEAVY
RAINFALL TONIGHT AS WIDESPREAD SHOWERS AND STORMS DEVELOP IN KANSAS
AND LIFT NORTHWARD INTO MAINLY SOUTHEASTERN NEBRASKA.
TODAY - SATURDAY:
THE NAM AND TO A LESSER EXTENT THE GFS DEVELOP PRECIPITATION THIS
AFTERNOON AS A SUBTLE UPPER WAVE TRACKS THROUGH THE NORTHWESTERLY
FLOW. THE WAVE IS DIFFICULT TO DETECT BUT WATER VAPOR IMAGERY SHOWS
SOME DRYING MOVING THROUGH WYOMING EARLY THIS MORNING AND THIS SEEMS
TO CORRESPOND TO WHAT THE MODELS ARE LATCHING ONTO. CONFIDENCE IS
NOT VERY HIGH ON THE COVERAGE OF PRECIPITATION BUT IT APPEARS THE
NORTHERN HALF OF THE FORECAST AREA...GENERALLY NORTH OF INTERSTATE
80 HAS AT LEAST A SLIGHT CHANCE OF SEEING PRECIPITATION THIS
AFTERNOON. THICKER CLOUD COVER...ASSOCIATED WITH THE UPPER WAVE
AND SHOWER/STORM ACTIVITY AS WELL AS NORTHEASTERLY SURFACE WINDS
SHOULD KEEP TEMPERATURES ACROSS THE NORTHERN FORECAST AREA
SOMEWHAT COOL WITH HIGHS IN THE UPPER 70S TO LOWER 80S EXPECTED.
SOUTH OF INTERSTATE 80 TEMPERATURES WILL BE CLOSER TO NORMAL OR
PERHAPS A BIT ABOVE NORMAL WITH HIGHS IN THE UPPER 80S EXPECTED.
THE BETTER CHANCES FOR PRECIPITATION WILL COME LATE THIS EVENING AND
ESPECIALLY OVERNIGHT AS VERY STRONG ISENTROPIC ASCENT IN ROUGHLY THE
310K TO 315K LAYER DEVELOPS ACROSS KANSAS AND SPREADS INTO SOUTHERN
NEBRASKA. A STRONG LOW LEVEL JET WILL ADVECT QUITE A BIT OF MOISTURE
INTO KANSAS AND SOUTHERN NEBRASKA AND AS A RESULT HAVE PLACED THE
HIGHEST POPS IN OUR SOUTHERN ZONES. THE COPIOUS MOISTURE FLUX INTO
THE REGION COUPLED WITH THE STRONG ASCENT WILL LEAD TO THE POTENTIAL
FOR FAIRLY HIGH PRECIPITATION AMOUNTS ACROSS OUR SOUTHERN ZONES.
WIDESPREAD AMOUNTS OF .5 TO .75 INCHES SEEM LIKELY WITH SOME AREAS
VERY LIKELY SEEING HEAVIER AMOUNTS. THIS WIDESPREAD POTENTIALLY
HEAVY RAIN MAY LEAD TO ISOLATED FLOODING IN OUR SOUTHERN ZONES
ALTHOUGH THE BETTER CHANCES FOR FLOODING RAINFALL SHOULD STILL BE TO
OUR SOUTH IN KANSAS WHERE THE BEST LIFT AND MOISTURE FLUX WILL
RESIDE.
PRECIPITATION SHOULD LAST INTO A PORTION OF SATURDAY...MAINLY IN
SOUTHEASTERN NEBRASKA BUT THE HEAVIEST RAIN SHOULD SHIFT AWAY FROM
THE REGION THROUGH THE DAY AS THE STRONGEST ASCENT AND MOISTURE FLUX
GETS FOCUSED ACROSS NORTHERN MISSOURI AND SOUTHERN IOWA. CLOUD
COVER...PRECIPITATION AND CONTINUED EASTERLY WINDS WILL LEAD TO
ANOTHER COOL DAY ACROSS THE REGION WITH HIGHS RANGING FROM THE MID
70S TO AROUND 80 DEGREES.
SUNDAY - MONDAY:
THE NORTHWESTERLY FLOW ALOFT WILL PERSIST THROUGH THIS TIME FRAME
BUT AS HIGH PRESSURE MIGRATES ACROSS THE REGION SUNDAY IT SHOULD
BRING A TEMPORARY BREAK TO THE PRECIPITATION CHANCES. HOWEVER AS THE
HIGH MOVES TO THE EAST AND SOUTHERLY FLOW RETURNS TO THE AREA
PRECIPITATION CHANCES WILL ONCE AGAIN RETURN TO THE FORECAST AREA
FOR SUNDAY NIGHT INTO MONDAY. WILL KEEP POPS RELATIVELY LOW AT THIS
POINT GIVEN SOME UNCERTAINTY WITH TIMING ANY UPPER WAVE THAT WOULD
HELP INITIATE THINGS AND WILL ONLY CARRY SLIGHT CHANCE POPS AT THIS
TIME.
TUESDAY - THURSDAY:
MEDIUM RANGE MODELS ARE IN DECENT AGREEMENT KEEPING THE UPPER RIDGE
POSITIONED IN THE SOUTHWEST AND TROUGHING OVER SOUTHEASTERN CANADA
AND THE NORTHEAST. THIS WILL PERPETUATE THE NORTHWESTERLY FLOW
ACROSS THE REGION WHICH MEANS WE'LL LIKELY HAVE SOME PERIOD OF
PRECIPITATION IN THE EXTENDED. GIVEN THE HIGH UNCERTAINTY WITH
TIMING ANY WAVE IN THIS PATTERN WILL KEEP THE EXTENDED DRY.
CDB
&&
.AVIATION...
FOR THE 06Z TAFS...
IN THE WAKE OF PAST EVENINGS STORM COMPLEX...RECENT RAIN WITH MAINLY
CLEAR SKIES AND LIGHT AND VARIABLE WINDS WILL BE FAVORABLE FOR IFR
CIGS/VSBYS FOR ALL TAF SITES FOR THE 11Z-15Z PERIOD. WILL MONITOR
GOING TAFS FOR DEVELOPMENT. AFTER MORNING FOG/STRATUS LIFTS AFT
15Z...VFR CONDITIONS EXPECTED. SFC WINDS TO GENERALLY BE LIGHT
NORTHEAST AOB 10KTS. TSRA MAY WORK BACK INTO TAF SITES AFT 00Z/20TH
AS A DISTURBANCE ALOFT APPROACHES. WILL CONSIDER INCLUSION IN 12Z
TAFS.
ROBERG
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$