314
FXUS63 KGID 130905
AFDGID
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
405 AM CDT TUE AUG 13 2013
...COOLER THAN NORMAL PATTERN CONTS WITH MORE CHANCES FOR
SPOTTYBUT BENEFICIAL RAINFALL THRU FRI THEN A PLEASANT AND DRY
WEEKEND APPEARS IN THE OFFING...
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 405 AM CDT TUE AUG 13 2013
ALOFT: A LGWV RIDGE WAS OVER THE ROCKIES...WITH A LGWV TROF
DOWNSTREAM OVER THE ERN USA. THIS PATTERN WILL CHANGE LITTLE THRU
TNGT. WV IMAGERY REVEALED A SUBTLE SHRTWV TROF LIFTING INTO WY.
GIVEN THAT MID-LVL WIND FIELDS ARE WEAK...THIS TROF SHOULD REMAIN
OVER SRN WY TODAY AND BEGIN EDGING INTO THE NEB PANHANDLE AND
NERN CO BY DAYBREAK WED.
SFC: FAIRLY STRONG 1024 MB HIGH PRES WAS OVER MANITOBA AND
EXTENDED S INTO THE NRN-CNTRL PLAINS. THIS HIGH WILL SLOWLY
TRANSITION INTO IA BY DAWN WED. THIS HIGH WILL MAINTAIN E-SE
UPSLOPE FLOW.
AS ANTICIPATED BY PRIOR SHIFTS...SHWRS/TSTMS HAVE ERUPTED OVER
THE SANDHILLS AND WERE MOVING SSE TOWARD S-CNTRL NEB. THESE
STORMS DEVELOPED WITHIN A LOW-LVL THETA-E RIDGE. BETWEEN 02-04Z
WINDS IN THE 3-5K FT LAYER ABRUPTLY VEERED TO S-SSE ON THE LNX
88D WIND PROFILE AND ULTIMATELY INCREASED TO AROUND 25 KTS...
SUGGESTING A NARROW LLJ.
A FEW ISOLATED SHWRS HAVE ATTEMPTED TO DEVELOP OVER S-CNTRL NEB
BUT COULD NOT BE SUSTAINED WITH AN APPARENT LACK OF INSTABILITY.
A 70-80 KT ULJ INCREASE VENTING ALOFT TODAY. THIS SHOULD CREATE A
FAVORABLE ENVIRONMENT FOR SCT SHWRS/TSTMS TO CONTINUE...DESPITE
THE LOSS OF THE LLJ.
CURRENT EXPECTATION IS THAT THE SHWRS/TSTMS WILL PROPAGATE SSE
ALONG THE INSTABILITY GRADIENT...MOSTLY REMAINING W OF HWY 281.
THE CURRENT CIRRUS SHIELD WILL BE MOSTLY E OF THE FCST AREA BY
SUNRISE. SO AS THE MRNG WEARS ON...EXPECT DESTABILIZATION TO
OCCUR. THIS COULD MAINTAIN THE SHWRS/TSTMS THRU THE DAY WITH SOME
WEAKENING NOTED ONCE MIXING ELIMINATES THE LLJ. TSTMS COULD
REDEVELOP OR INTENSIFY ALONG THE OUTFLOW BOUNDARY THIS AFTN.
MID-LVL LAPSE RATES ARE POOR AND E WINDS WILL CONTINUE TO
MAINTAIN LOWER DWPTS THAN IN PRVS DAYS...ESPECIALLY N AND E OF
THE TRI-CITIES. SO AT WORST MLCAPE WILL BE NO MORE THAN 1200
J/KG. WHILE SOME SMALL HAIL AND GUSTY WINDS WILL BE POSSIBLE WITH
THE STRONGEST STORMS...AM NOT EXPECTING ANY SVR.
TODAY: P/SUNNY BUT WITH A PERIOD OF SHWRS/TSTMS MAINLY W OF HWY
281 THIS MRNG. DEPENDENT UPON THE DEGREE OF CLOUD COVER...A FEW
ADDITIONAL TSTMS COULD ERUPT OR WHAT/S LEFT COULD REINTENSIFY
THIS AFTN. AREAS ALONG AND E OF HWY 281 WILL REMAIN DRY FOR MOST
IF NOT ALL DAY.
TNGT: P-M/CLOUDY. A MODEST 20-25 KT LLJ WILL DEVELOP AGAIN OVER
THE HIGH PLAINS. THIS WILL RESULT IN RENEWED SHWR/TSTM
DEVELOPMENT. UNCERTAINTY ON WHERE AND IF THEY PROPAGATE INTO THE
FCST AREA. THE BEST QPF CLUSTERING SUGGESTS SHWR/TSTM ACTIVITY
REMAINS N AND W OF THE FCST AREA...EXCEPT FOR THE GEM WHICH
HAMMERS US WITH BIGTIME QPF.
TEMPS WILL BE ABOUT 5F COOLER THAN NORMAL TODAY-TNGT. USED BIAS
CORRECTED BLEND OF 2M TEMPS AND THE PRVS GID FCST. WINDS AND
DWPTS ARE CONSENSUS OF ALL GUIDANCE...EXCEPT WIND SPEEDS ARE BIAS
CORRECTED TNGT.
.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 405 AM CDT TUE AUG 13 2013
MAIN CHALLENGE WILL BE DETERMINING CHANCES OF PRECIPITATION.
THE UPPER WAVE PATTERN WILL INCLUDE A TROUGH IN THE EAST AND
RIDGE IN THE WEST. THE PATTERN WILL BE AMPLIFIED AND IS EXPECTED
TO FURTHER AMPLIFY THROUGH THE REST OF THE WORK WEEK INTO THE
WEEKEND. THIS WILL LAND US WITHIN NORTHWEST FLOW...WHICH WILL
CONTINUE TO PLAY HAVOC ON THE PREDICTABILITY OF CHANCES OF
PRECIPITATION.
WE COULD BE IN STORE FOR AT LEAST A SMALL CHANCE OF SHOWERS AND
THUNDERSTORMS FOR MOST OF THE LONG TERM WITH THIS TYPE OF
PATTERN. THE BEST CHANCE OF DRY WEATHER COMES OVER THE WEEKEND
WHEN THE RIDGE SNEAKS OVER TO THE EAST...BUT BY SUNDAY NIGHT AND
MONDAY...THE RIDGE IS EXPECTED TO DEAMPLIFY AND ALLOW FOR THE
POSSIBILITY OF MORE RAIN. SEVERE WEATHER IS NOT OUT OF THE
QUESTION...BUT SHEAR WILL GENERALLY BE LOW...SO WE WILL DEPEND
LARGELY ON INSTABILITY DURING THE LATE AFTERNOONS AND
EVENINGS...WHICH IS RATHER DICEY AS WELL.
TEMPERATURES WILL GENERALLY BE A BIT ON THE COOL SIDE...EXCEPT
SEASONABLE OVER THE WEEKEND WHEN THE RIDGE MAKES ITS WAY TO THE
EAST A BIT. DEPENDED HIGHLY UPON RECENT MODEL PERFORMANCE FOR
TEMPERATURES.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1241 AM CDT TUE AUG 13 2013
REST OF TNGT: VFR THRU 10Z WITH OCCASIONAL CIGS AROUND 5K FT. THEN
SOME MVFR FOG IS POSSIBLE 11Z-12Z. LIGHT E WINDS.
TUE: VFR WITH SCT SHWRS AND POSSIBLE THUNDER. TIMING OF ANY PCPN
IS UNCERTAIN GIVEN ITS SCT NATURE. SO IT'S BEEN HANDLED WITH VCSH
FOR NOW. WATCH FOR POSSIBLE AMENDMENTS TO UPGRADE TO TSRA. ESE
WINDS LESS THAN 10 KTS.
TUE EVNG: VFR WITH SOME MISC DEBRIS CLOUDS AROUND 8K AND 25K FT.
WINDS WILL BECOME LIGHT AND VARIABLE.
CIG CONFIDENCE: MEDIUM
VSBY CONFIDENCE: MEDIUM
WIND CONFIDENCE: HIGH
WX CONFIDENCE: MEDIUM
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM...HALBLAUB
LONG TERM...HEINLEIN
AVIATION...HALBLAUB