Severe Thunderstorm Warning 182, NWS Hastings, NE

SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION...
NATIONAL WEATHER SERVICE HASTINGS NE
258 PM CDT SUN AUG 15 1999

...POPS STILL MAIN CHALLENGE THROUGH WED...

ELEVATED CONVECTION DEVELOPED LAST NIGHT AROUND 09Z OVER ERN PART OF
CWFA...AIDED BY 50 KNOT LOW LEVEL JET.  THE 00Z ETA RUN FROM LAST
EVENING DID NOT CATCH THIS...BUT THE 00Z NGM AND THE 12Z NGM FROM
YESTERDAY DID PREDICT IT.  SCENARIO FOR TONIGHT IS SOMEWHAT SIMILAR
WITH SOME FACTORS POINTING TO NOCTURNAL CONVECTION...AND THE
NGM/RUC/MM5 CALLING FOR PRECIP BUT THE ETA/AVN ARE DRY.

18Z SURFACE ANALYSIS HAS TROF TRYING TO ENTER WRN ZONES WITH MID 60S
DEWPOINTS AHEAD OF TROF...WITH THE LOW OVER NRN SD AND COLD FRONT
TRAILING.  MAIN ENERGY WITH DAKOTAS SYSTEM...BUT THERE ARE HINTS OF
WEAK SHORTWAVES RIDING THROUGH THE RIDGE AND THROUGH THE SUBTROPICAL
PLUME WHICH WOULD PROVIDE SOME LIFT.  IN ADDITION...THE H25 JET
DROPS SLIGHTLY SOUTH WITH CWFA UNDER WEAK-MDT DIVERGENCE TONIGHT.
THE SURFACE BOUNDARY SHOULD PROVIDE A FOCUS FOR CONVERGENCE.  THUS
IT IS DIFFICULT TO PIN DOWN THE MAGNITUDE OF VERTICAL MOTION TONIGHT
BUT GIVEN THE ADEQUATE AMOUNT OF MOISTURE TO WORK WITH AND A FEW
WEAK MECHANISMS...WILL GO WITH CHANCE POPS ALL OF CWFA TONIGHT...
AS ADVERTISED BY NGM/MM5/RUC.  MOST ACTIVITY SHOULD BE LATE...
HOWEVER LATEST VISIBLE IMAGERY SHOWING AC/CU RAPIDLY DEVELOPING OVER
NW KS/NE CO/SW NEBRASKA SO PERHAPS SOME EVENING ACTIVITY IS POSSIBLE
IN SW COUNTIES.  THIS IDEA SOMEWHAT SUPPORTED BY SPC SWODY1
DISCUSSION.

AFTER TONIGHT THE MODEL OF CHOICE IS LESS CLEAR AND ALL MODELS ARE
SIMILAR WITH FRONTAL PLACEMENT FROM ERN NEBRASKA INTO CENTRAL OR WRN
KS AREA BY 18Z MON.  THIS SEEMS TO BE ABOUT AS FAR SOUTH AS THE
UPPER WINDS WOULD ALLOW IT TO GO...THEN MON NT AND TUE IT SHOULD
WEAKEN AND MOST LIKELY DRIFT BACK NORTH AS UPPER RIDGE TRIES TO
REBUILD.  THE VAGUE LOCATION OF THIS FRONT AND LACK OF ANY DEFINED
LIFTING MECHANISMS MAKE THE QPF PLACEMENT DIFFICULT AT BEST.  WILL
CARRY LOW POPS MON NT WITH THE FRONT AND POSSIBLY EVEN TUE IN NRN
COUNTIES.  THIS IDEA SOMEWHAT SUPPORTED BY DAY2 QPFPFD.  THE AVN
SHOWS A FAST MOVING WAVE SLIDING DOWN INTO NE NEBRASKA TUE NT ON TOP
OF THE RIDGE...SO WILL NEED TO MONITOR THIS FEATURE WITH TIME.

GID ALREADY UP TO 90 AT THIS TIME...SO GUIDANCE HIGH TEMPERATURES OF
AROUND 90 AND 90-95 KS LOOK REASONABLE FOR MON AND TUE.  OVERALL THE
EXTENDED LOOKS QUIET WITH SEASONAL TEMPERATURES.

.GID...NONE.

NIETFELD