Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 280551
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1251 AM CDT TUE JUL 28 2015

.UPDATE...
ISSUED AT 1250 AM CDT TUE JUL 28 2015

WILL HOPEFULLY HAVE A BETTER HANDLE ON THINGS BY THE TIME OF THE
MAIN MORNING DISCUSSION ISSUANCE AROUND ROUGHLY 4 AM...BUT AT
LEAST TO STATE THE OBVIOUS FOR NOW...AS OF 0530Z/1230 AM...THE
ENTIRE CWA HAS THUS FAR REMAINED STORM-FREE TONIGHT WITH ALL
ONGOING STRONG-SEVERE CONVECTION REMAINING 50-100 MILES NORTHWEST
OF THE CWA IN THE SANDHILLS. IN SHORT...VARIOUS MODELS SUCH AS THE
LATEST RAP13 HAVE CERTAINLY STRUGGLED WITH CONVECTIVE CHANCES SO
FAR TONIGHT...INITIATING THINGS OVER THE LOCAL AREA TOO EARLY AND
TOO AGGRESSIVELY. CERTAINLY TWO LIMITING FACTORS THUS FAR HAVE
LIKELY BEEN 1) RATHER WARM MID LEVEL TEMPS EVIDENT BY 700MB VALUES
IN THE 13-15C RANGE AND 2) LACK OF LARGE-SCALE LOW-MID LEVEL
CONVERGENCE...AS DESPITE THE PRESENCE OF A STOUT 850MB LOW LEVEL
JET OVERHEAD (40-50KT) THERE IS THUS FAR LITTLE TO NO SPEED
CONVERGENCE OVER THE LOCAL AREA. AS THE NIGHT WEARS ON THOUGH INTO
THE FIRST PART OF THE DAYLIGHT HOURS...LARGE SCALE FORCING WILL
INCREASE FROM THE WEST...AND IT REMAINS QUITE POSSIBLE (ESPECIALLY
AFTER 08Z/3AM) THAT AT LEAST ISOLATED TO SCATTERED STORMS WILL
INITIALLY DEVELOP WITHIN THE NORTHWEST CWA AND THEN EXPAND EAST
AND POSSIBLY SOUTHEAST INTO THE DAYLIGHT HOURS. WHILE RATHER WARM
MID LEVEL TEMPS MAY CONTINUE TO POSE A LIMITING FACTOR FOR MORE
WIDESPREAD CONVECTIVE COVERAGE...SAW NO REASON TO REDUCE THE GOING
20-40 POPS ACROSS THE CWA LATE TONIGHT INTO THE FIRST PART OF THE
DAYLIGHT HOURS...KEEPING THE HIGHEST VALUES IN THE NORTH. AS FOR
SEVERE POTENTIAL...ALTHOUGH FORECAST SOUNDINGS SUGGEST MOST STORMS
SHOULD BE RATHER ELEVATED...CANNOT RULE OUT AT LEAST AN ISOLATED
THREAT FOR PRIMARILY SEVERE HAIL...GIVEN MUCAPE UP TO AROUND 2000
J/KG IN THE 850-700MB LAYER...ALONG WITH MODEST DEEP LAYER SHEAR
OF GENERALLY 20-30KT. A SEVERE WIND THREAT WOULD SEEMINGLY BE LESS
LIKELY...UNLESS AN ORGANIZED SURGING COLD POOL CAN GET GOING. WILL
BE INTERESTING TO SEE HOW MUCH (OR HOW LITTLE?) CONVECTION
DEVELOPS OVER THE CWA DURING THESE NEXT SEVERAL HOURS...

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 312 PM CDT MON JUL 27 2015

THE AREA CONTINUES TO SIT UNDER SWRLY FLOW IN THE UPPER LEVELS
THIS AFTERNOON...WITH BROAD RIDGING OVER THE SRN CONUS WHILE A
STORM SYSTEM IS WORKING ITS WAY THROUGH THE NRN ROCKIES. SITTING
IN THE WAKE OF THIS MORNINGS SHORTWAVE DISTURBANCE WHICH BROUGHT
RAIN TO MAINLY WRN/SRN PORTIONS OF THE OF THE CWA...ALONG WITH
WARM MID LEVEL TEMPS KEEPING THINGS CAPPED...THE AFTERNOON HOURS
HAVE BEEN DRY ACROSS THE CWA. AT THE SFC...A WEAKER PATTERN THIS
MORNING BROUGHT LIGHT/VARIABLE WINDS...BUT AS THE DAY AS PASSED
AND THAT NEXT STORM SYSTEM HAS SHIFTED CLOSER TO THE PLAINS...LOW
PRESSURE HAS DEEPENED OVER THE HIGH PLAINS...RESULTING IN MORE
SRLY FLOW...WITH GUSTS THIS AFTERNOON CLIMBING INTO THE 20 TO 25
MPH RANGE.

KEPT THE REMAINDER OF THE AFTERNOON HOURS DRY...BUT THUNDERSTORM
CHANCES WILL PICK UP THIS EVENING/OVERNIGHT. SEEING SOME ACTIVITY
ALREADY STARTING TO DEVELOP OVER THE HIGH PLAINS...AND INCREASING
LARGER SCALE LIFT WITH APPROACHING SYSTEM TO THE WEST...ALONG WITH
A HEALTHY LLJ DEVELOPING /MODELS GENERALLY ARND 50KTS/ WILL HELP
DRIVE THESE CHANCES. UNFORTUNATELY EVEN AT THIS TIME...THERE ARE
SOME DIFFERENCES BETWEEN MODELS WITH WHERE THE BETTER CONVERGENCE
WITH THE LLJ SETS UP AND WITH THE OVERALL COVERAGE...SOME SHOW
ACTIVITY PLOWING RIGHT THROUGH MUCH OF THE CWA...WHILE OTHERS SHOW
THE NWRN THIRD OR SO WITH THE BEST CHANCES...AND QUICKLY
DIMINISHING FURTHER EAST AND SOUTH. KEPT THE 50 POPS IN PLACE
ACROSS THE WRN CWA THIS EVENING...BUT LEFT 20 TO 40 POPS
ELSEWHERE...WILL JUST HAVE TO SEE HOW THINGS EVOLVE OVER THE
COMING HOURS. THE INSTABILITY/DEEPER LAYER SHEAR COMBO KEEPS THE
POTENTIAL FOR STRONG/SEVERE THUNDERSTORMS AS A CONCERN...WITH THE
CWA SITTING IN THE SPC DAY 1 MARGINAL/SLIGHT RISK AREAS. WIND/HAIL
REMAIN THE PRIMARY HAZARDS.

THE MAIN UPPER LEVEL SYSTEM SHIFTS EAST...AND AT 12Z TOMORROW
MORNING IS EXPECTED TO BE LOCATED OVER NERN PORTIONS OF MONTANA.
AN ACCOMPANYING SFC COLD FRONT WILL ALSO BE MAKING ITS WAY
E/SE...AND MODELS ARE NOT IN TOO BAD OF AGREEMENT SHOWING THE
FRONT AT 12Z ACROSS THE NWRN CORNER OF THE CWA. BECAUSE THIS FRONT
HAS A BETTER THAN USUAL FOR THIS TIME OF YEAR PUSH FROM THE UPPER
LEVEL SYSTEM...IT SHOULD MAKE GOOD PROGRESS THROUGH THE CWA. BY
18Z MODELS SHOW THE FRONT ALREADY OVER THE SERN THIRD OF THE CWA.
THIS FRONT WILL START TO USHER IN MUCH WELCOME DRIER DEWPOINTS
FROM NW/SE...THOUGH THE MORE WIDESPREAD DROP IS LIKELY JUST AFTER
THE END OF THIS FORECAST PERIOD/...AND FORECAST HIGHS ARE EXPECTED
TO RANGE FROM THE MID 80S NW TO LOWER 90S IN THE SE.

KEPT SOME 20-30 POPS ACROSS MUCH OF THE CWA DURING THE MORNING
HOURS TO ACCOUNT FOR ANY LINGERING ACTIVITY FROM THE OVERNIGHT
HOURS /THOUGH SOME MODELS SUGGEST THERE WONT BE ANY POST
12Z/...BUT ONCE THAT PASSES OFF TO THE EAST...ANY POPS WOULD BE
CONFINED TO AREAS NEAR THE SFC COLD FRONT ACROSS SERN AREAS.
ACTUALLY TRIMMED A LITTLE BIT MORE OFF THE NWRN PORTIONS OF THE
INHERITED POPS FOR THE AFTERNOON HOURS...AND IF THE FRONT CAN PUSH
FAR ENOUGH SE LIKE SOME MODELS SUGGEST...THOSE POPS COULD BE
REMOVED.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 312 PM CDT MON JUL 27 2015

MAIN ISSUE WILL BE DETERMINING TIMING AND CHANCES OF
PRECIPITATION.

THE MAIN FEATURE FOR OUR SYNOPTIC WEATHER WILL BE THE UPPER LEVEL
HIGH ALONG THE SOUTHERN TIER OF THE UNITED STATES THAT WILL
BUILD WEST INTO THE SOUTHWESTERN UNITED STATES DURING THE WEEK
GIVING US WEST NORTHWEST UPPER LEVEL FLOW. THE UPPER JET AXIS WILL
REMAIN NORTH OF THE CWA...BUT THE NORTHERN PERIPHERY OF THE
SUBTROPICAL HIGH WILL BE IN OUR VICINITY AND WILL ALLOW LOW-
AMPLITUDE PERTURBATIONS TO POTENTIALLY GIVE US A SMALL SHOT AT
SHOWERS AND THUNDERSTORMS FROM TIME TO TIME DURING THE LONG
TERM...WITH NO PARTICULAR TIME THAT STANDS OUT AS HAVING MUCH
HIGHER CHANCE OF RAIN OVER OTHERS...OTHER THAN PERHAPS THURSDAY
NIGHT WITH CONSIDERABLE THETA-E ADVECTION IN OUR WEST/SOUTHWEST.

FOR TUESDAY NIGHT...A COLD FRONT ASSOCIATED WITH A SHORTWAVE
TROUGH SHOULD BE WELL SOUTHEAST OF THE AREA BY THE TIME TUESDAY
NIGHT ROLLS AROUND. MOST OF ANY CONVECTION SHOULD BE SOUTHEAST OF
THE CWA...ALTHOUGH THERE COULD BE SOME LINGERING CONVECTION IN THE
SOUTHEASTERN CWA...DEPENDING UPON HOW MUCH ELEVATED POST-FRONTAL
CONVECTION WE MAY GET IN THE EVENING.

WEDNESDAY WILL BE THE MOST COMFORTABLE DAY IN THE LONG TERM
FORECAST. SIGNIFICANTLY LOWER DEWPOINTS IN THE 50S ARE EXPECTED
WITH HIGHS IN THEM MID 80S...WHICH HAS SUPPORT FROM ENSEMBLES.

BY THURSDAY...RETURN FLOW RETURNS AND A STEADY RISE IN DEWPOINTS
WILL ENSUE INTO THE WEEKEND AS WELL AS WARMING TEMPERATURES WITH
HIGHS IN THE 90S FOR THE WEEKEND. THERE WILL BE SMALL CHANCES OF
SHOWERS AND THUNDERSTORMS AS LOW-AMPLITUDE WAVES MOVE ALONG THE
PERIPHERY OF THE UPPER HIGH...BUT THERE WILL NOT BE ANY SIZABLE
WAVES IN THE FORECAST TO GIVE US ANYTHING MORE THAN A 20 TO 30
PERCENT CHANCE OF PRECIPITATION. NOTHING PARTICULARLY STANDS OUT
FOR SEVERE POTENTIAL AS WELL.

&&

.AVIATION...(FOR THE 06Z KGRI/KEAR TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1250 AM CDT TUE JUL 28 2015

ALTHOUGH VFR CEILING/VISIBILITY ARE STILL EXPECTED TO PREVAIL
THROUGH THE PERIOD...THERE ARE AT LEAST FOUR CAVEATS AND/OR
ISSUES TO CONSIDER DURING THE PERIOD. STARTING OFF WITH THESE
FIRST 6-9 HOURS OR SO...THE TWO PRIMARY ISSUES INCLUDE THE
POSSIBILITY OF THUNDERSTORM DEVELOPMENT AND ALSO THE CONTINUANCE
OF LOW LEVEL WIND SHEAR (LLWS) STRONG ENOUGH FOR TAF MENTION. AS
FOR THE STORM CHANCES...THEY SHOULD PRIMARILY BE CONFINED TO THE
08Z-13Z TIME FRAME...AND GIVEN THAT CONFIDENCE IN OCCURRENCE AT
THE TERMINALS IS STILL RATHER SHAKY...HAVE MAINTAINED ONLY A
VICINITY THUNDERSTORM (VCTS) MENTION FOR NOW. SHOULD STORMS
DEVELOP...AT LEAST BRIEF HEAVY RAIN/SMALL HAIL/GUSTY WINDS ARE ALL
POSSIBLE. CONFIDENCE IS CERTAINLY MUCH HIGHER IN LOW LEVEL WIND
SHEAR PERSISTING THROUGH AROUND 12-13Z...THANKS TO A ROUGHLY
30-35KT DIFFERENCE IN SHEAR MAGNITUDE BETWEEN THE SURFACE AND
ROUGHLY 1500 FT AGL...WHERE SOUTH-SOUTHWEST WINDS AT THAT LEVEL
SHOULD MAX OUT ROUGHLY 45KT. GETTING INTO THE DAYLIGHT
HOURS...CANNOT COMPLETELY RULE OUT A LINGERING ROGUE
SHOWER/THUNDERSTORM BUT PROBABILITY APPEARS TOO LOW FOR EVEN A
VCTS MENTION. ATTENTION THEN TURNS TO THE PASSAGE OF SEASONABLY-
STRONG COLD FRONT (BY JULY STANDARDS)...AS THE SOUTHERLY BREEZES
EARLY THIS MORNING TRANSITION RATHER ABRUPTLY TO A NORTHERLY
DIRECTION BY MID-LATE MORNING WITH GUST POTENTIAL INTO THE 20-25KT
RANGE. THIS NORTHERLY DIRECTION WILL REMAIN IN PLACE THROUGH THE
REMAINDER OF THE PERIOD...ALTHOUGH SPEEDS SHOULD SUBSIDE TO
NEAR/BELOW 10KT BY THE LATE AFTERNOON/EVENING HOURS. LAST BUT NOT
LEAST...THERE APPEARS TO BE AT LEAST A 3-6 HOUR WINDOW OF
OPPORTUNITY FOR A HIGH-END MVFR OR LOW-END VFR CEILING DURING THE
DAY IN THE WAKE OF THE PASSING COLD FRONT. FOR NOW WILL LEAN
OPTIMISTICALLY TOWARD THE LOWER-END VFR SCENARIO...BUT THIS WILL
NEED MONITORED.

&&

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

$$

UPDATE...PFANNKUCH
SHORT TERM...ADP
LONG TERM...HEINLEIN
AVIATION...PFANNKUCH


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