Severe Thunderstorm Warning 175, NWS Hastings, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1258 AM CDT TUE AUG 4 2009

.AVIATION...06Z KGRI TAF. THE BIG ISSUE OF THE NIGHT IS A GROUP OF
STORMS HEADING SOUTHEAST TOWARD THE TERMINAL. THINK THIS DESERVES
A FROM GROUP...WITH AN OUTSIDE SHOT AT SOME STRONG WIND AND
PERHAPS SOME HAIL. ANOTHER ROUND OF CONVECTION IS ONCE AGAIN
POSSIBLE TUESDAY EVENING.

&&

.PREV DISCUSSION... /ISSUED 606 PM CDT MON AUG 3 2009/

AVIATION...TRICKY FORECAST FOR THE 00Z WITH THE MAIN ISSUE BEING
WHETHER OR NOT THUNDERSTORMS WILL MOVE INTO KGRI DURING THE
PERIOD. A COUPLE OF DIFFERENT THINGS COULD TRY TO SPARK A FEW
THUNDERSTORMS TONIGHT. A WEAK FRONTAL BOUNDARY ACROSS SOUTHERN
NEBRASKA IS ONE SUCH FEATURE...WHILE AN UPPER LEVEL DISTURBANCE
MOVING ACROSS SOUTHERN SOUTH DAKOTA IS ANOTHER. SHORT RANGE MODEL
SOLUTIONS ARE ALL OVER THE PLACE IN REGARDS TO WHETHER OR NOT ANY
STORMS MAY REACH KGRI...AND IN THE END HAVE OPTED TO PLAY THE ODDS
AND GO WITH THE 15Z SREF WHICH KEEPS THE CHANCE OF RAIN AT KGRI
AT LESS THAN 20 PERCENT THROUGH THE PERIOD. WILL KEEP IT DRY AT
KGRI FOR NOW...AND WATCH HOW THINGS PROGRESS TONIGHT. THAT BEING
SAID...GENERALLY THINK THE BEST CHANCE OF THUNDERSTORMS FOR KGRI
WOULD COME IF STORMS CAN DEVELOP ACROSS NORTHERN NEBRASKA AND
THEN MOVE SOUTHEAST TOWARDS KGRI. WINDS WILL PRIMARILY BE FROM
THE EAST/NORTHEAST THROUGH THE PERIOD.

PREV DISCUSSION... /ISSUED 323 PM CDT MON AUG 3 2009/

SHORT TERM...THROUGH TUESDAY NIGHT. HARD FORECAST TO REALLY PIN
DOWN JUST WHAT MAY HAPPEN OVER OUR CWFA WITH SUCH WARM AIR ALOFT
IN PLACE. CURRENTLY WEAK FRONTAL BOUNDARY IS LOCATED ALONG THE
KANSAS/NEBRASKA BORDER AREA. DEWPOINTS/MOISTURE HAVE INCREASED
SUBSTANTIALLY AGAIN TODAY ON THE TOP SIDE OF THE FRONT...AND ARE
AROUND 70 DEGREES. WEAK MID LEVEL INSTABILITY CONTINUES TO LINGER
OVER THE FAR NORTHERN CWFA...LIKELY NEAR THE SHARP H7 THERMAL
GRADIENT. WAVE IMAGERY CONTINUES TO DEPICT A SOLDI SHORTWAVE IN
THE BLACK HILLS...AND MOVING EAST SOUTHEAST.

AS MENTIONED...THE DIFFICULTY OF THE FORECAST IS JUST WHERE AND
WHEN STORMS MAY DEVELOP. ONE AREA OF CONCERN IS ALONG THE FRONT...
ALTHOUGH CONVERGENCE IS WEAKISH AND CAPPING STRONG. STILL THAT
KEEPS THE SOUTHERN/SOUTHEAST CWFA IN PLAY. ONE MORE LIKELY SCENARIO
IS THE WAVE TO THE NORTHWEST SPARKING STORMS WEST OF VALENTINE...
WHICH WOULD MOVE EAST SOUTHEAST...AND MAY BE ABLE TO MIGRATE INTO
THE NORTHERN CWFA. UNFORTUNATELY...WITHS SUCH EXTREME INSTABILITY
AROUND...ANY STORMS IN THE WOULD BE SEVERE FOR A TIME. HAVE KEPT
20 TO 30 PERCENT RAIN CHANCE IN THERE FOR THE CWFA TO MAKE SURE
ALL BASES ARE COVERED.

TUESDAY IS TRICKY...NOT KNOWING JUST WHAT/IF ANY CONVECTION WILL
BE AROUND...OR IF THE CWFA WILL BE INFLUENCED BY CONVECTIVE
OUTFLOW. MUCH OF THE DAY LOOKS DRY IN GENERAL BEFORE THE NEXT
WAVE COULD TRIGGER MORE STORMS TUESDAY NIGHT FROM THE WEST.

LONG TERM...12Z WEDNESDAY THROUGH MONDAY.  MAIN FORECAST CONCERN LIES
WITH PRECIPITATION CHANCES EARLY ON...THEN TO THE WARM UP
EXPECTED LATER ON IN THE LONG TERM PERIOD.

BEST CHANCES FOR SHOWERS AND THUNDERSTORMS ACROSS THE CWA STILL LOOK
TO BE CONFINED TO THE WEDNESDAY THROUGH THURSDAY NIGHT TIMEFRAME.
NO SIGNIFICANT CHANGES WHEN LOOKING AT THE UPPER LEVEL PATTERN
COMPARED TO THE LAST SEVERAL DAYS...WITH THE MAIN RIDGE AXIS
REMAINING ANCHORED OVER THE ROCKIES THROUGH MOST OF THE DAY ON
THURSDAY.  LATER IN THE DAY AND INTO THURSDAY NIGHT...MODELS IN
PRETTY GOOD AGREEMENT SHOWING THE UPPER LEVEL LOW PRESSURE SYSTEM
WHICH HAD BEEN OFF THE WEST COAST CONTINUING TO SHIFT EAST ACROSS
CALIFORNIA...SHIFTING THE RIDGE AXIS FURTHER EAST ONTO THE PLAINS.
FLOW OVER THE CWA STARTS OFF NORTHWESTERLY AND GRADUALLY BECOMES
MORE ZONAL...AND HAS BEEN THE CASE...ADDITIONAL WEAK MID/UPPER LEVEL
WAVES ARE EXPECTED TO CROSS THROUGH THE REGION.  AT THE
SURFACE...MODELS CONTINUE TO SHOW LOW PRESSURE DEVELOPING OVER THE
HIGH PLAINS/ESP OVER WNW KS...WITH A FRONTAL BOUNDARY DRAPED TO THE
EAST.  STILL SOME UNCERTAINTIES WITH THE EXACT PLACEMENT OF THE
BOUNDARY...BUT WITH IT IN THE AREA AND WITH ANY UPPER LEVEL WAVES
PASSING OVERHEAD...COULDNT COMPLETELY RULE OUT PRECIPITATION
CHANCES.  KEPT POPS ON THE LOW SIDE UNTIL MORE CONFIDENCE CAN BE
GAINED...AND IS LOOKING TO BE MORE SCATTERED IN NATURE VS ANYTHING
WIDESPREAD.

HAVE DRY FORECAST GOING FOR FRIDAY AND ON INTO EARLY NEXT
WEEK...WITH A TRANSITION FROM ZONAL TO SOUTHWESTERLY FLOW ACROSS
THE REGION IN THE UPPER LEVELS.  UPPER LEVEL LOW/TROUGH SYSTEM
CONTINUES TO SHIFT EAST FROM THE WEST COAST...THUS PUSHING THE RIDGE
AXIS FURTHER EAST ACROSS THE COUNTRY.  THE MAIN SHIFT OF THE RIDGE
AXIS LOOKS TO COME FRIDAY...AND BY THE TIME THE WEEKEND ROLLS AROUND
SITS EAST OF THE MO RIVER.  THIS LOOKS TO BE THE GENERAL IDEA
THROUGH THE REST OF THE WEEKEND AND INTO MONDAY...AND MODELS IN
DECENT AGREEMENT.  THERE IS SOME HINT AT PRECIPITATION DEVELOPING ON
SUNDAY WITH A MID LEVEL WAVE MOVING INTO THE AREA...BUT WITH IT
BEING DAY 6 DECIDED TO KEEP DRY TO SEE IF THIS IS A PERSISTENT
FEATURE.

AS FAR AS TEMPERATURES GO...WARMING TREND WELL AGREED UPON BETWEEN
MODELS.  WIDESPREAD HIGH TEMPERATURES WELL INTO THE 90S EXPECTED BY
THE END OF THE WEEKEND AND INTO THE WEEKEND...QUITE A CHANGE FROM
THE PAST FEW WEEKS...WITH LOWER 100S CURRENTLY FORECAST ACROSS THE
SOUTH.  AS THIS TIME GETS A LITTLE CLOSER...WILL CONTINUE TO MONITOR
POTENTIAL NEED FOR SOME KIND OF HEADLINE AS HEAT INDICES IN THE
LOWER/MID 100S LOOK POSSIBLE.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

AVIATION...HEINLEIN

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