FXUS63 KOAX 190255
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
955 PM CDT WED MAY 18 2011
.DISCUSSION...
GOING FORECAST IN FAIRLY GOOD SHAPE TONIGHT. MAY SOME SMALL
CHANGES TO THE POPS OVERNIGHT AND INTO THE DAY ON THUR BASED ON
THE LATEST GUIDANCE. EVENING UPPER AIR ANALYSIS INDICATED DEEP
UPPER LEVEL TROUGH OVER THE WESTERN US ASSOCIATED WITH A 135 KT
300 MB JET ACROSS THE DESERT SOUTHWEST. HEIGHT FALLS WERE NOT
OVERLY IMPRESSIVE WITH AN AREA OF 50 M 12-HR HEIGHT FALLS OVER
AZ/NM. SEASONABLY STRONG MOISTURE RETURN WAS NOTED OVER THE
SOUTHERN PLAINS WITH A GOOD AREA OF +15 C 850 MB DEWPOINTS INTO
CENTRAL OKLAHOMA. THIS LOW-LEVEL MOISTURE WAS BEING CAPPED BY
REALLY VERY POOR MID LEVEL LAPSE RATES WITH 500 TO 700 MB DELTA-T
VALUES OF 15 TO 19 C ACROSS THE PLAINS.
DIURNAL LOW LEVEL JET WILL INCREASE LATER THIS EVENING FROM
OKLAHOMA THROUGH KANSAS AND ALLOW FOR STRONG MOISTURE RETURN INTO
SOUTHEAST NEBRASKA BY 12Z ON THURSDAY. MASS CONVERGENCE AT THE
NOSE OF THE LOW-LEVEL JET AND WEAK CAPPING SHOULD LEAD TO AN
EXPANDING AREA OF SHOWERS AND THUNDERSTORMS OVER CENTRAL KANSAS
LATER THIS EVENING...AND THIS SHOULD SPREAD TOWARD SOUTHEAST
NEBRASKA BY EARLY MORNING. STILL NOT EXPECTING ANYTHING SEVERE IN
OUR AREA GIVEN THE SUBSTANDARD LAPSE RATES...BUT SOME SMALL HAIL
WILL BE POSSIBLE. HAVE BACKED OFF ON TIMING OF POPS
OVERNIGHT...BUT STILL HAVE CAT POPS IN THE SOUTH AFTER 09Z.
THE SHOWERS AND THUNDERSTORMS ARE LIKELY TO CONTINUE INTO THE
MORNING HOURS ACROSS EASTERN NEBRASKA AND SOUTHWEST IOWA DUE TO
CONTINUED WARM AIR ADVECTION...BUT SHOULD TEND TO DIMINISH BY
AFTERNOON AND HAVE LOWERED AFTER POPS OVER MOST OF THE AREA. WILL
LIKELY AGAIN SEE AN INCREASE IN ACTIVITY TOMORROW EVENING...BUT AT
LEAST A SMALL BREAK BETWEEN ROUNDS OF ACTIVITY SEEMS PROBABLE. OTHER
FORECAST ELEMENTS SEEM ON TRACK AND NO OTHER CHANGES PLANNED.
UPDATED OUT BY 10 PM.
BOUSTEAD
&&
.PREV DISCUSSION... /ISSUED 345 PM CDT WED MAY 18 2011/
DISCUSSION...
ACTIVE WEATHER PATTERN EXPECTED THROUGH THE MIDDLE OF NEXT WEEK.
BROAD TROUGH CENTERED OVER UTAH WILL VERY SLOWLY SHIFT EASTWARD
OVER THE NEXT FEW DAYS...FINALLY BECOMING CENTERED OVER CENTRAL
PLAINS BY FRIDAY AFTERNOON. MEANWHILE...SURFACE LOW PRESSURE OVER
THE SOUTHEASTERN PLAINS BECOMES MORE ORGANIZED AND DEEPENS OVER
WESTERN KANSAS TONIGHT. SCATTERED SHOWERS AND THUNDERSTORMS WILL
PERSIST MAINLY ACROSS EASTERN NEBRASKA THIS EVENING AS A STRONG
PUSH OF WARM AIR ADVECTION WORKS ACROSS THE AREA. SHOWERS AND
THUNDERSTORMS WILL BECOME WIDESPREAD BY LATE TONIGHT AS UPPER
LEVEL SUPPORT INCREASES LATE TONIGHT AND MUCH OF THURSDAY WITH A
80KT JET MAX TRACKING INTO THE REGION. ELEVATED THUNDERSTORMS
COULD CONTAIN MARGINALLY SEVERE HAIL ON THURSDAY AFTERNOON AND
EVENING...PARTICULARLY ACROSS SOUTHEAST NEBRASKA NEAR THE
APPROACHING JET MAX. WIDESPREAD PRECIPITATION WILL PERSIST INTO
THURSDAY NIGHT AND EARLY FRIDAY WITH A DEEPER POOL OF MOISTURE
SPELLING THE POTENTIAL FOR MODERATE/HEAVY RAINFALL AMOUNTS.
AGAIN...MARGINALLY SEVERE STORMS WILL BE POSSIBLE DURING THIS TIME
FRAME.
THE SLOW MOVING UPPER LOW TURNS NORTHWARD ON FRIDAY AND WOBBLES
INTO NORTH DAKOTA BY SATURDAY...THEN TOWARDS LAKE SUPERIOR ON
SUNDAY NIGHT. AS A RESULT SEVERAL WEAK WAVES ROTATING AROUND THE
PARENT LOW WILL KEEP THE AIRMASS VERY UNSTABLE AND ALLOW RAIN
CHANCES TO REMAIN IN THE FORECAST THROUGH AT LEAST THE WEEKEND.
DRY SLOTTING WILL BRING SOME BREAKS TO THE SHOWERS BUT OVERALL
PATTERN WILL BE WET THROUGH SATURDAY. TEMPERATURES WILL BE MILD
WITH HIGHS EXPECTED PRIMARILY IN THE 70S. RIDGING MAKES A BRIEF
RETURN ON MONDAY...BUT GUIDANCE SUGGESTS THAT ANOTHER BROAD TROUGH
WILL BRING ENCROACHING ON THE PLAINS AS EARLY AS TUESDAY.
AVIATION...
CONDITIONS WILL LIKELY REMAIN VFR FOR MUCH OF TONIGHT...BUT THEN
THINGS BEGIN TO CHANGE. A LARGE UPPER LOW TO THE WEST WILL SPIN OFF
SHORT WAVE ENERGY WHICH WILL LIKELY BEGIN TO AFFECT OUR SOUTHERN
ZONES SHORTLY BEFORE SUNRISE. THE QG FORCING IS ACTUALLY STRONGEST
IN WESTERN NE THURSDAY MORNING...BUT A LOBE OF IT WILL MOVE
NORTHWARD ACROSS OUR AREA. THEREFORE RAIN WILL BECOME INCREASINGLY
LIKELY MOVING FROM SOUTH TO NORTH LATE TONIGHT AND THURSDAY
MORNING...WITH MVFR CONDITIONS PREVAILING IN MUCH OF THE RAINFALL.
THERE IS ALSO A RISK THAT OUR SOUTHERN ZONES MAY EXPERIENCE SOME IFR
CEILINGS AS THURSDAY MORNING PROGRESSES. THE BEST CHANCES FOR A FEW
THUNDERSTORMS TO EMBED WITH THE RAINFALL WILL BE FROM ABOUT A
COLUMBUS TO OMAHA LINE AND SOUTHWARD THURSDAY MORNING. NORTH OF THAT
LINE...THUNDERSTORM CHANCES BECOME INCREASINGLY MORE DIFFICULT DUE
TO STABILITY...BUT AGAIN RAINFALL IS CERTAINLY A THREAT IN OUR
NORTHERN ZONES.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$