000
FXUS63 KTOP 250529 AAB
AFDTOP
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TOPEKA KS
1229 AM CDT SAT MAY 25 2013
.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 338 PM CDT FRI MAY 24 2013
TONIGHT THROUGH SATURDAY...
THIS AFTERNOON AN UPPER LEVEL RIDGE PROGRESSED FURTHER EASTWARD INTO
THE CENTRAL CONUS. A WARM FRONT EXTENDING FROM A SURFACE LOW OVER
FAR NORTHERN MONTANA STRETCHED SOUTHWARD ACROSS WESTERN
NEBRASKA...WESTERN KANSAS AND INTO OKLAHOMA. REGIONAL RADAR WAS
PICKING UP ON SOME LIGHT REFLECTIVITIES ALONG AND EAST OF THIS
BOUNDARY ACROSS NORTH CENTRAL KANSAS AND SOUTH CENTRAL NEBRASKA LATE
MORNING INTO THIS AFTERNOON...BUT LIKELY NOT SEEING MUCH OF THIS
REACHING THE GROUND AS SOUNDINGS SHOWED A SHALLOW DRY LAYER STILL IN
PLACE NEAR THE SURFACE. MID-LEVEL CLOUD COVER WAS ADVANCING EASTWARD
ACROSS THE AREA THIS AFTERNOON...BUT WITH THE BREEZY SOUTHEASTERLY
WINDS AFTERNOON TEMPERATURES WERE ABLE TO RISE INTO THE LOWER TO
MIDDLE 70S.
MAIN AREA OF UNCERTAINTY IN THE SHORT TERM IS WITH REGARDS TO THE
TIMING AND LOCATION OF ANY PRECIPITATION TONIGHT AND SATURDAY.
MODELS SHOW A WEAK EMBEDDED SHORTWAVE DEVELOPING ALONG THE NORTHERN
EDGE OF THE RIDGE OVER NEBRASKA AND NORTHERN KANSAS...WITH THE WARM
FRONT LOOKING TO PIVOT NORTHWARD TOWARD THE KANSAS/NEBRASKA BORDER
THROUGH THE DAY ON SATURDAY. OVERNIGHT...THE BEST CHANCES FOR
SHOWERS AND THUNDERSTORMS LOOK TO BE ACROSS WESTERN KANSAS AND INTO
SOUTHERN NEBRASKA WHERE BETTER FORCING IS PRESENT NEAR THE
BOUNDARY...WHICH ALSO COINCIDES WITH THE LOCATION OF THE
SOUTHWESTERLY LLJ. AS THE WARM FRONT LIFTS NORTHWARD ACROSS THE AREA
AND THE EMBEDDED SHORTWAVE SHIFTS JUST NORTH AND EAST OF THE CWA BY
THE AFTERNOON...COULD SEE SOME SHOWERS AND THUNDERSTORMS DEVELOP
OVER NORTHEASTERN KANSAS AND ALONG THE KANSAS/NEBRASKA BORDER. HAVE
INCREASING CHANCE POPS OVER THIS AREA SATURDAY AFTERNOON INTO THE
EVENING HOURS.
AS FOR TEMPERATURES...SOUTHERLY FLOW WILL KEEP OVERNIGHT LOWS WARMER
TONIGHT IN THE UPPER 50S/LOWER 60S. THESE SOUTHERLY WINDS WILL BE
BREEZY THROUGH THE DAY ON SATURDAY AS THE PRESSURE GRADIENT TIGHTENS
OVER THE REGION...RESULTING IN GOOD WAA BOOSTING AFTERNOON
TEMPERATURES INTO THE LOWER 80S.
.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 338 PM CDT FRI MAY 24 2013
THE MAIN TROUGH REMAINS ACROSS THE PACNW WITH SW FLOW SPREADING
EASTWARD INTO THE PLAINS. SHORTWAVES EMBEDDED WITHIN THE SW FLOW
WILL PROGRESS THROUGH THE CENTRAL AND NORTHERN PLAINS THROUGH THE
WEEKEND. ON SATURDAY NIGHT MODEL CONSENSUS IS THAT A WAVE WILL PASS
NORTH OF THE AREA. THEREFORE THE PRIMARY FOCUS FOR CONVECTION WILL
BE NEAR AND NORTH OF A WARM FRONT ALONG THE MO RIVER VALLY OVERNIGHT
SATURDAY. CONVECTION ON SATURDAY NIGHT COULD LEAVE AN OUTFLOW
BOUNDARY NEAR OR ACROSS THE FORECAST AREA WHICH MAY BE THE FOCUS FOR
THUNDERSTORM DEVELOPMENT SUNDAY DURING THE DAY. INSTABILITY WILL BE
HIGH ACROSS THE REGION AND DEEP LAYER SHEAR WILL BE AROUND 30 KTS SO
COULD NOT RULE OUT A FEW STRONG ISOLATED STORMS IF THE CAP CAN
WEAKEN. THE STRENGTH OF THE CAP VARIES WHICH EACH MODEL SOLUTION.
LOCALLY HEAVY RAINFALL MAY ALSO BE POSSIBLE SUNDAY AND SUNDAY
NIGHT WITH PWAT VALUES AROUND 1.5 INCHES. ON MONDAY THE BETTER
CHANCES FOR STORMS LOOKS TO BE NORTH AND EAST OF THE AREA WITH NOT
MUCH CHANGE IN THE OVERALL LARGE SCALE PATTERN.
THE LONG TERM FORECAST REMAINS A BIT TRICKY REGARDING THE TIMING OF
WEAK IMPULSES THAT WILL AFFECT THE AREA AND THEIR IMPACT ON
THUNDERSTORM POTENTIAL. MID/LONG RANGE MODELS ARE CONSISTENT IN
SLOWLY BUT SURELY SHIFTING A LONG WAVE TROUGH EAST INTO THE
PLAINS...KEEPING THE FORECAST AREA UNDER SOUTHWESTERLY FLOW ALOFT
FOR THE MAJORITY OF NEXT WEEK WITH MOIST SOUTHERLY FLOW AT THE
SURFACE. THIS WILL RESULT IN A RATHER UNSTABLE AIRMASS IN PLACE
THROUGH THE ENTIRE WEEK ALTHOUGH ALSO EXPECT THE INSTABILITY TO BE
FIRMLY CAPPED DURING THE AFTERNOON HOURS OF TUESDAY AND MUCH OF
WEDNESDAY. EVEN DURING THIS PERIOD...STILL SEE SOME POTENTIAL FOR
OVERNIGHT THUNDERSTORMS AS THERE SHOULD BE ELEVATED INSTABILITY
ABOVE THE CAPPING INVERSION AND PERIODS OF CONVECTION MOVING EAST
OFF OF THE HIGH PLAINS AS THE WEAK DISTURBANCES EJECT FROM THE MAIN
TROUGH. AT THIS TIME...ACTUALLY FEEL RATHER CONFIDENT IN A DRY
FORECAST ON TUESDAY...AND ONLY SLIGHT CHANCES IN CENTRAL KS WITH DRY
ELSEWHERE ON WEDNESDAY GIVEN THE CAP STRENGTH...BUT WITH AT LEAST
SOME SMALL THUNDERSTORM CHANCES OVERNIGHT EACH NIGHT. THE MODERATE
TO STRONG INSTABILITY WILL BE OFFSET BY RATHER WEAK SHEAR PROFILES
AND DO NOT ANTICIPATE A WIDESPREAD SEVERE WEATHER THREAT FROM MONDAY
NIGHT THROUGH WEDNESDAY.
BY THURSDAY AND FRIDAY...THE MID/LONG RANGE MODEL GUIDANCE REMAINS
FAIRLY CONSISTENT IN EJECTING THE STRONGEST PART OF THE WESTERN
TROUGH AS A NEGATIVELY TILTED WAVE ON THURSDAY. MODEL DIFFERENCES
ARISE IN THE DEPTH OF THIS FEATURE AS THE ECMWF DIGS THE STRONG WAVE
INTO NORTHERN NEW MEXICO BEFORE LIFTING IT NORTH INTO THE DAKOTAS
WITH A STRONGER MERIDIONAL FLOW COMPONENT IN EASTERN KANSAS WHILE
THE GFS MAINTAINS A STRONG ZONAL UPPER FLOW REGIME WITH THE
NEGATIVELY TILTED TROUGH TRACKING FROM WYOMING INTO THE DAKOTAS.
BOTH MODEL SOLUTIONS SUGGEST AT LEAST THE POTENTIAL FOR A SEVERE
WEATHER EVENT ON THURSDAY AFTERNOON REGARDLESS OF THE DETAILS...
ALTHOUGH THE MAGNITUDE OF SEVERE POTENTIAL WILL SURELY DEPEND ON
THOSE DETAILS. IT WOULD ALSO APPEAR THAT SEVERE POTENTIAL CONTINUES
INTO FRIDAY...BUT WILL BE DEPENDENT UPON THE EVOLUTION OF THE UPPER
TROUGH AND ITS EFFECT ON SURFACE FRONTAL POSITION. THE BOTTOM LINE
WITH THIS FORECAST IS TO KEEP AN EYE ON THE PERIODS FROM WEDNESDAY
EVENING THROUGH FRIDAY EVENING FOR SEVERE WEATHER POTENTIAL.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1228 AM CDT SAT MAY 25 2013
STILL EXPECTING CONVECTION TONIGHT TO REMAIN NORTH OF THE
TERMINAL SITES OVERNIGHT. HOWEVER...STRATOCU DECK AT 2500-3500
FEET HAS STEADILY INCREASED TO THE WEST AND SOUTH OF THE
TERMINALS AND SPREAD AND LOWER INTO ALL TERMINALS BY 08Z BEFORE
SCATTERING BACK OUT AFTER 14Z. WINDS 8-10 KTS WILL VEER FROM
SOUTHEAST TO SOUTHERLY DURING THIS SAME TIMEFRAME. THEY WILL THEN
REMAIN SOUTHERLY EARLY SATURDAY MORNING BEFORE INCREASING AGAIN
AFT 14Z WHEN GUSTS OVER 20KTS AREA THEN EXPECTED AS WARM FRONT
LIFTS NORTHWARD. BETTER FOCUS FOR ANY CONVECTION TO FORM NEAR
TERMINALS SATURDAY/SATURDAY EVENING REMAINS NORTH OF THE AREA
AND CONFIDENCE REMAINS TOO LOW TO INSERT INTO TERMINAL FCST AT
THIS TIME.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HENNECKE
LONG TERM...BARJENBRUCH/SANDERS
AVIATION...63
