Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 040000
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
700 PM CDT MON AUG 3 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 315 PM CDT MON AUG 3 2015

FOCUS WILL BE ON THE POTENTIAL FOR THUNDERSTORMS TONIGHT/TOMORROW.
MAIN CHANGES TO THIS FORECAST WERE THE DECREASE IN
THUNDERSTORM/RAINFALL POTENTIAL THIS AFTERNOON AND EVENING...WHICH
INVOLVED COMPLETELY REMOVING AFTERNOON RAINFALL POTENTIAL.
OTHERWISE...TEMPERATURES WILL BE CLOSE TO NORMAL DURING THE SHORT
TERM PERIODS.

ALTHOUGH AMPLE INSTABILITY IS IN PLACE OVER THE FORECAST AREA...WE
LACK FORCING TO INITIATE THUNDERSTORMS THIS AFTERNOON SO OPTED TO
REMOVE ALL POPS TODAY. EVEN IF THUNDERSTORMS WERE TO DEVELOP...ALL
VARIABLES POINT TO SUB SEVERE THUNDERSTORMS. AT THIS TIME IT IS
UNLIKELY ANY THUNDERSTORMS DEVELOP BEFORE 00Z ANYWAY. BETWEEN 00Z
AND 12Z THE CHANCES FOR THUNDERSTORMS INCREASE...BUT THESE CHANCES
SHOULD BE CONFINED TO NORTH/NORTHEASTERN PORTIONS OF THE FORECAST
AREA. THIS IS EVIDENT AFTER 00Z WITH THE NAM AND THE FOLLOWING
SIMULATED REFLECTIVITY MODELS: HRRR...ARW AND NMM. THEREAFTER...IT
LOOKS LIKE WE WILL HAVE A LULL UNTIL TUESDAY AFTERNOON CONVECTION
DEVELOPS. THE NAM AND BOTH THE NMM/ARW SHOW CONVECTION DEVELOPING
TOMORROW AFTERNOON. MUCAPE VALUES AROUND 1500 TO 2000 J/KG ARE
PROGGED FOR TOMORROW AFTERNOON. HOWEVER...SHEAR VALUES ARE WEEK
TOMORROW. I WOULD NOT EXPECT ANY STRONG ROTATING UPDRAFTS TO
DEVELOP...SO WIDESPREAD SEVERE THUNDERSTORMS LOOK UNLIKELY...BUT
CANNOT RULE OUT A STRONG THUNDERSTORM TOMORROW AFTERNOON. THERE WILL
BE A WARM FRONT DRAPED ACROSS THE FORECAST AREA TOMORROW...AND THIS
SHOULD BE THE FOCUS FOR INITIATION AS A SURFACE LOW TRACKS TO OUR
NORTH ACROSS SOUTH DAKOTA. DEPENDING ON WHERE THIS BOUNDARY ENDS UP
WILL DETERMINE COVERAGE ACROSS THE FORECAST AREA FOR
THUNDERSTORMS.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 315 PM CDT MON AUG 3 2015

STARTING WITH THE BIG PICTURE ON TUESDAY EVENING...SHOULD HAVE
TROUGHING IN THE NORTHEAST CONUS WITH RIDGING IN THE CENTRAL PART OF
THE COUNTRY AND ANOTHER TROUGH MOVING ONTO THE SW CANADIAN COAST.
IT APPEARS THE CENTRAL U.S. RIDGE WILL BE UNDERCUT BY A NEGATIVE
TILTED SHORTWAVE TROUGH THAT WILL EXTEND FROM EASTERN MONTANA TO
SOUTHEAST KANSAS. AT THE SURFACE...A LEE TROUGH OF LOW PRESSURE
SHOULD BE LOCATED FROM SW SDAK TO WEST TEXAS...WITH A WARM FRONT
EXTENDING FROM THE SDAK LOW INTO EASTERN NEB. COULD HAVE ONGOING
SCATTERED THUNDERSTORMS NEAR THE WARM FRONT WHICH AT THIS TIME WOULD
FAVOR THE NORTHERN HALF OF OUR CWA.  COLD ALSO SEE SOME OVERNIGHT
CONVECTION MOVE IN FROM THE WEST AS THE MID LEVEL AND SURFACE
TROUGHS NOTED ABOVE ADVANCE EASTWARD. NAM AND GFS DIFFER SOMEWHAT ON
INSTABILITY WITH GFS SHOWING HIGHER CAPE EXTENDING OVER MUCH OF THE
CWA IN THE 00-03Z TIME FRAME WHILE NAM GENERATING HIGHEST CAPE
CLOSER TO THE WARM FRONT IN THE NE. BOTH MODELS AGREE THAT DEEP
LAYER SHEAR IS BETTER ACROSS THE SW CWA AT 30-40 KT...WHILE ONLY 10-
15 KT IN THE NE. AT PRESENT...HAVE 30-40 PERCENT POPS GOING FOR
TUESDAY NIGHT AND DONT SEE MUCH REASON TO ALTER FROM THIS AT THIS
TIME. INSTABILITY AND SHEAR PARAMETERS NOT LINING UP ALL THAT WELL
BUT CANNOT RULE OUT ISOLATED SEVERE ANYWHERE IN THE CWA.

COULD BE SOME LINGERING PRECIP WED MORNING BUT MOST OF THE DAY
APPEARS DRY WITH MID LEVEL WAVE PASSING TO THE EAST AND SHORTWAVE
RIDGING OVERHEAD. BY THURSDAY THE PATTERN IS PROGGED TO HAVE RIDGING
OVER THE DESERT SOUTHWEST AND AND DECENT TROUGH OVER THE NORTHWEST
U.S. AND SW CANADA. THAT TROUGH WILL SLOWLY MOVE EAST AND ALLOW
SHORTWAVES TO MOVE EAST OVER THE NORTHERN PLAINS. THE QUESTION THEN
BECOMES WILL THE FORCING EXTEND FAR ENOUGH SOUTH TO GIVE US
ADDITIONAL CHANCES FOR THUNDERSTORMS. CHECKING 700MB PROGS...WOULD
THINK WE HAVE A FEW SHOTS FOR ADDITIONAL RAIN.  DIFFICULT TO TRY AND
TIME BEST RAIN CHANCES BUT AT PRESENT LOOKS LIKE THURS
AFTERNOON/EVENING AND THEN AGAIN SOMETIME OVER THE WEEKEND. HOWEVER
CAN ALREADY SEE CONVECTIVE FEEDBACK PROBLEMS WITH THE GFS FOR FRIDAY
NIGHT JUST TO OUR WEST...SO AT THIS TIME WONT GET TOO CARRIED AWAY
WITH POPS.

&&

.AVIATION...(FOR THE 00Z KGRI/KEAR TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 700 PM CDT MON AUG 3 2015

SOME MODELS ARE SHOWING SOME REDUCED VISIBILITY...BUT CONFIDENCE
IS NOT HIGH.

&&

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

$$

SHORT TERM...GUERRERO
LONG TERM...EWALD
AVIATION...HEINLEIN


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