Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 302050
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
350 PM CDT THU JUL 30 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 349 PM CDT THU JUL 30 2015

MAIN ISSUE WILL BE DETERMINING CHANCES FOR PRECIPITATION.

AT THE SYNOPTIC SCALE...THE UPPER LEVEL SUBTROPICAL HIGH WILL SHIFT
WEST NORTHWEST...EXTENDING INTO THE GREAT BASIN...PUTTING US WITHIN
GENERALLY WEAK WEST NORTHWEST FLOW BY TONIGHT/FRIDAY. THERE IS AN
OUTSIDE CHANCE OF A STRAY SHOWER/THUNDERSHOWER CREEPING INTO THE
WESTERN/NORTHWESTERN CWA AS A FEW SHORT TERM MODELS INDICATE
THIS...LIKE THE HRRR/RAP/WRF ARW. A CONSIDERABLE CU FIELD HAS
DEVELOPED OVER THE SANDHILLS AND THUNDERSHOWERS HAVE ALREADY
DEVELOPED...SIGNALING THAT SOME MODELS HAD A CLUE ON THIS
DEVELOPMENT. THIS WILL BE ENOUGH TO STICK A VERY SMALL CHANCE OF
THUNDERSTORMS THROUGH THIS EVENING IN OUR WEST/NORTH. ANY OF THIS
CONVECTION THAT FIRES WILL LIKELY DIE OFF IN THE EVENING AS THIS
WOULD BE LARGELY DIURNALLY DRIVEN. WE COULD ALSO GET SOME

ANOTHER COMPLICATION COMES OVERNIGHT AS WE COULD POTENTIALLY BE IN
THE REAR RIGHT QUADRANT OF AN 80+ KT UPPER LEVEL JET
STREAK...ESPECIALLY IN THE NORTHEASTERN CWA. AS THETA-E ADVECTION
INCREASES...THIS COULD ADD TO OUR CHANCES. THE WRF ARW PLACES A
THUNDERSTORMS FAIRLY CLOSE TO THE NORTHEASTERN CWA...BUT NOT QUITE
WITHIN OUR BORDERS. THIS IS ENOUGH FOR ME TO KEEP A SLIGHT CHANCE OF
THUNDER INTO THE OVERNIGHT IN OUR NORTH. ANY LEFTOVER CONVECTION MAY
BE GIVEN A CHANCE TO LIVE A FEW MORE HOURS INTO THE OVERNIGHT WITH
THE HELP OF THE POSITION OF THE UPPER LEVEL JET STREAK.

WITH FRIDAY COMES MORE UNCERTAINTY. I EXPECT CAPE TO INCREASE TO
1500 TO 2500 J/KG WITH MODERATE SHEAR AND A COLD FRONT (ALTHOUGH
RATHER WEAK) HEADING SOUTH INTO THE CWA THAT COULD BE THE FOCUS OF
CONVECTION. SMALL CHANCES OF PRECIPITATION WILL FOLLOW THE FRONT AS
IT MOVES SOUTH. ALTHOUGH THE SREF PAINTS DEEP LAYER SHEAR IN THE 30
TO 40 KT RANGE TOMORROW...IT IS ABOUT 10 KTS TOO HIGH TODAY...SO MY
GUESS IS THAT SHEAR WILL BE MORE IN THE 20 TO 30 KT RANGE FOR
FRIDAY...CLOSER TO 30 KTS IN OUR NORTH. FOR LOWS TONIGHT...I WENT
WITH CONSRAW...WHICH KEEPS US PRETTY CLOSE TO THE PREVIOUS FORECAST.
FORECAST HIGHS MAY BE A BIT HIGHER THAN THE PREVIOUS FORECAST AS I
USED A COMBINATION OF NAM/BCCONSRAW/HI RES FOR FRIDAY MAXIMUMS.


.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 349 PM CDT THU JUL 30 2015

FCST CONFIDENCE IN THE OVERALL PATTERN IS ABOVE NORMAL. TEMPS ARE
AVERAGE CONFIDENCE...BUT HAVE THE POTENTIAL TO BUST TOO HIGH
DEPENDING ON HOW TSTMS PLAY OUT. TSTM/RAINFALL POTENTIAL IS LOW
CONFIDENCE.

ALOFT: WNW FLOW WILL PREVAIL THRU THE FCST...WITH A RIDGE IN THE W
AND A TROF IN THE E. THE SUBTROPICAL HIGH WILL BE PARKED OVER THE
DESERT SW. HEIGHTS ARE FCST TO FALL OFF THE W COAST THIS WEEKEND
WITH CYCLOGENESIS ENSUING. WHILE THERE IS MODEL SPREAD...THERE ARE
INDICATIONS THAT THE E PAC TROF WILL APPROACH THE W COAST WED-THU.
THIS WOULD NUDGE THE WRN USA RIDGE TOWARD THE E AND A LITTLE CLOSER
TO THE FCST AREA.

THE MAIN BAND OF WESTERLIES WILL REMAIN WELL N OF THE FCST AREA...
WHICH MEANS LITTLE IN THE WAY OF SYNOPTIC FORCING. THAT LEAVES OUR
SENSIBLE WX TIED TO SMALL SCALE FEATURES WHICH ARE ESSENTIALLY
IMPOSSIBLE TO ACCT FOR IN THE LONG-TERM FCST.

EVERY ONCE IN A WHILE...THE EC/GFS TRY TO BRING A WEAK VORT MAX THRU
HERE...BUT THESE ARE GENERATED BY MODELED CONVECTION...HAVE LITTLE
OR NO CONSISTENCY AND THEY MOST LIKELY WILL NOT BE REALITY. THE
PROBLEM IS THAT THIS INCREASES FCST UNCERTAINTY EVEN MORE.

SURFACE: THE COOL FRONT THAT SAGS INTO NEB FRI WILL LIFT BACK N AS A
WARM FRONT SAT AS LOW PRES DIVES SE ALONG THE FRONT INTO SD. THIS
FRONT WILL REMAIN QUASI-STATIONARY ACROSS MT-SD-IA AND THEN E INTO
THE OH VALLEY THE NEXT SEVERAL DAYS. IT WILL OSCILLATE SOME AS
MULTIPLE LOWS TRACK SE ALONG IT...AND AT TIMES IT WILL DROP INTO
NEB. ITS LOCATION WILL ALSO BE MUDDIED BY TSTM OUTFLOWS.

SEVERE: THERE IS SOME POTENTIAL FOR A SEVERE TSTM OR TWO SAT...BUT
IT`S CONDITIONAL ON IF TSTMS DEVELOP OR MOVE INTO THE FCST AREA AT
ALL. CONFIDENCE IS LOW...BUT IF SOMETHING FIRES 4PM-10PM...THERE IS
POTENTIAL FOR SVR WITH MLCAPE OF 2000-3000 J/KG AND SHEAR OF 40 KTS
IN THE CLOUD-BEARING LAYER.

TEMPS WILL EDGE A LITTLE HOTTER EACH DAY THRU MON...SLOWLY CLIMBING
FROM NEAR NORMAL SAT...TO ABOVE NORMAL SUN-MON. WHILE WE HAVE
INDICATED A COOL-DOWN INTO THE 80S OVER S-CNTRL NEB TUE-THU...AM NOT
COMPLETELY SOLD ON THIS. IT COULD BE DUE MODELED CONVECTION...WHICH
IS FAR FROM RELIABLE. HOWEVER...WE CONT TO SEE HINTS THAT THE FRONT
COULD SAG DOWN TO I-70 TUE...DUE TO SOME MODEST AMPLIFICATION OF THE
TROF OVER THE GREAT LAKES. 4 OF THE LAST 5 EC RUNS HAVE BEEN
CONSISTENT ON THIS AND NOW THE 06Z/12Z GFS ARE ON BOARD. IF THIS
DOES OCCUR...IT WOULD ENHANCE THE RISK FOR MCS ACTIVITY WHICH COULD
HOLD TEMPS DOWN.

&&

.AVIATION...(FOR THE 18Z KGRI/KEAR TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1251 PM CDT THU JUL 30 2015

VFR CONDITIONS ARE FORECAST WITH A COUPLE OF CAVEATS. THERE IS
SOME MID-LEVEL CU DEVELOPING TO THE NORTHWEST OF THE
TERMINALS...BUT ANY THUNDERSTORM DEVELOPMENT SHOULD STAY TO THE
NORTHWEST OF THE TERMINALS AS ANY CONVECTION THAT DEVELOPS OVER
THE SANDHILLS SHOULD DIE OUT BEFORE THEY REACH THE TERMINALS...AS
THIS IS LARGELY DIURNALLY DRIVEN. MORE THUNDERSTORMS ARE POSSIBLE
BY FRIDAY AFTERNOON AS A COLD FRONT DROPS SOUTH...PROBABLY JUST
AFTER THE END OF THIS FORECAST.


&&

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

$$

SHORT TERM...HEINLEIN
LONG TERM...HALBLAUB
AVIATION...HEINLEIN


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