Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 280236
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
936 PM CDT WED AUG 27 2014

.UPDATE...
ISSUED AT 919 PM CDT WED AUG 27 2014

WENT AHEAD AND EXPANDED THE FLASH FLOOD WATCH TO INCLUDE ALL BUT A
FEW COUNTIES ON THE FRINGES OF THE FORECAST AREA THROUGH THURSDAY
MORNING...AS PERSISTENT HEAVY RAINFALL IS DEVELOPING ACROSS
PORTIONS OF NORTH CENTRAL KANSAS THIS EVENING AND SLOWLY SPREADING
NORTHEASTWARD. EXPECT THE LLJ TO ONLY ENHANCE THIS ACTIVITY
THROUGH THE LATE EVENING HOURS...WITH HEAVIER RAINFALL BECOMING
MORE WIDESPREAD AFTER MIDNIGHT. PER LATEST MODEL DATA AND
MESOSCALE PRECIPITATION DISCUSSION...EXPECT THE POTENTIAL FOR
HOURLY RAINFALL IN EXCESS OF 2 INCHES ALONG WITH ISOLATED RAINFALL
TOTALS OF 4 TO 6 INCHES NOT OUT OF THE QUESTION...SPREADING RIGHT
ACROSS THE HEART OF THE LOCAL FORECAST AREA OVERNIGHT. THE GOOD
NEWS IS THAT WHILE FLOODING POTENTIAL IS INCREASING...SEVERE
THUNDERSTORM THREAT IS DECREASING.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 328 PM CDT WED AUG 27 2014

THE PRIMARY FORECAST CONCERN WILL CENTER AROUND THE THREAT OF
THUNDERSTORMS WITH HEAVY RAIN AND AN OUTSIDE CHANCE OF A FEW
SEVERE THUNDERSTORMS.

AN UPPER LEVEL TROUGH OF FAIRLY IMPRESSIVE STRENGTH FOR AUGUST IS
CURRENTLY CENTERED OVER THE SALT LAKE CITY AREA AND WILL SLOWLY
TRACK OUT INTO THE HIGH PLAINS DURING THE OVERNIGHT HOURS.
LOW LEVEL MOISTURE IS ABUNDANT OUT AHEAD OF THIS UPPER SYSTEM
ACROSS THE CENTRAL PLAINS WITH DEW POINTS IN THE 70S FOR MOST
AREAS. THERE IS ESSENTIALLY LITTLE TO NO MID LEVEL CAP ALLOWING
SHOWERS AND THUNDERSTORMS TO FORM RATHER EASILY IN BANDS OUT AHEAD
OF THE APPROACHING SYSTEM. EXPECT THESE BANDS OF THUNDERSTORMS
WILL CONTINUE TO EXPAND IN COVERAGE AND STRENGTH THROUGH THE
EVENING HOURS WITH THE GREATEST COVERAGE LIKELY BETWEEN SUNSET AND
MIDNIGHT.

SEVERE WEATHER THREAT...INSTABILITY IS MODEST...BUT HAS BEEN
HAMPERED BY EXTENSIVE CLOUD COVER...WHICH IS NOT EXPECTED TO
CHANGE. THE UPPER WAVE IS RESULTING IN INCREASING WIND SHEAR WITH
EFFECTIVE DEEP LAYER SHEAR VALUES AROUND 35 KTS ACROSS OUR KANSAS
ZONES. THE COMBINATION OF INSTABILITY AND SHEAR IS SUFFICIENT FOR
A FEW SEVERE THUNDERSTORMS...BUT GIVEN THE EXPECTED EXPANSIVE
COVERAGE OF CONVECTION...THERE WILL BE A LOT OF COMPETITION FOR
THE AVAILABLE INSTABILITY AND EXPECT INSTABILITY WILL BE THE
LIMITING FACTOR. CONSEQUENTLY...THE THREAT OF SEVERE WEATHER WILL
BE FOCUSED ACROSS OUR SOUTHWESTERN ZONES...SOUTH AND WEST OF THE
TRI CITIES WHERE INSTABILITY IS THE GREATEST.

HEAVY RAIN THREAT...RAIN WILL BE HEAVY AT TIMES THIS
EVENING...WITH THE HEAVIER RAIN MOVING INTO OUR FLASH FLOOD WATCH
AREA BY LATER EVENING...PRIMARILY AFTER DARK. THERE IS SOME
QUESTION IF THE RAIN RATES WILL BE HIGH ENOUGH TO PRODUCE FLASH
FLOODING...BASICALLY WILL IT RAIN HARD AND FAST ENOUGH TO PRODUCE
FLASH FLOODING. SO THAT IS THE ASPECT THAT WILL HAVE TO BE WATCHED.
THERE IS NOT MUCH QUESTION ABOUT THE RAIN...IT SHOULD AT LEAST
RAIN...ITS JUST HOW MUCH AND HOW FAST. THEREFORE...WILL ALLOW THE
FLASH FLOOD WATCH TO CONTINUE THROUGH THE OVERNIGHT HOURS.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 328 PM CDT WED AUG 27 2014

ALOFT: THE SLOW-MOVING LOW OVER UT WILL CONT E AND OPEN UP AS IT
CROSSES THE CNTRL PLAINS THU-FRI. BY 00Z/SAT THE TROF AXIS WILL BE E
OF THE FCST AREA. THE MULTI-DAY 500 MB EC/GFS/GEM ENSEMBLE MEANS
AGREE THAT THE LONGWAVE WRN USA TROF/ERN USA RIDGE IS HIGHLY
PROBABLE AND WILL CONT THRU THIS FCST PERIOD AND LIKELY BEYOND THRU
THE NEXT 10-14 DAYS. THE TROF CURRENTLY MOVING THRU THE ALEUTIANS
WILL MOVE ONSHORE FRI AND CARVE OUT THE NEXT WRN USA TROF SAT-SUN.
THIS WILL TRANSITION THE FLOW HERE BACK TO SW SUN. THE TROF WILL
TRANSITION INTO THE PLAINS MON-TUE. WHILE THERE IS HIGH CONFIDENCE
IN THIS SCENARIO AMONGST THE LAST 3 CYCLES OF EC/UKMET/GEM/GFS
...THE TROF LOOKS BROAD WHICH MEANS IT WILL BE IMPOSSIBLE TO
PINPOINT SPECIFICS UNTIL WE GET CLOSER.

SURFACE: WEAK LOW PRES AND ITS ASSOCIATED WEAK FRONTS WILL DRIFT E
OF THE REGION THU-FRI. WEAK HIGH PRES WILL BE OVERHEAD AT DAYBREAK
SAT...BUT HEAD E WITH A NEW LEE TROF DEVELOPING AHEAD OF THE COOL
FRONT PROGRESSING THRU THE INTERMOUNTAIN W. THIS FRONT WILL MOVE
THRU SUN NIGHT FOLLOWED BY HIGH PRES MON-TUE.

OVERALL THIS PATTERN WILL FAVOR TEMPS AT OR COOLER THAN NORMAL WITH
A ONE-DAY SPIKE ABOVE NORMAL SUN. THEN ITS BACK TO AT OR COOLER THAN
NORMAL MON-TUE. THE THREAT FOR TSTMS/RAIN WILL DECREASE...BUT LOOK
FOR THE FRONT TO LIGHT UP SUN EVE.

HAZARDS: SOME POTENTIAL FOR SEVERE TSTMS THU. THE TSTM THREAT
DECREASES FRI WITH NO SEVERE. SUN HAS THE POTENTIAL TO BE A BIG
SEVERE WX DAY. STAY TUNED...

POPS THU-SAT WERE A 50-50 BLEND OF THE 03Z/09Z SREF...THEN TEMPERED
WITH AN EVEN BLEND OF THE 00Z/06Z/12Z NAM AND COLLABORATED WITH
SURROUNDING OFFICES. THIS SHOULD PROVIDE A GOOD DEPICTION IN THE
HOURLY WX GRAPHS ONLINE.

THE DAILY DETAILS...

THU: SREF QPF PROBABILITIES SUGGEST THAT TONIGHT`S MCS WILL BE
DEPARTING THE REGION AT DAYBREAK. THE BEST CHANCE FOR AFTERNOON/EVE
TSTM REDEVELOPMENT WILL BE S AND E OF THE TRI-CITIES. THESE STORMS
WILL THEN EXIT TO THE S AND E OVERNIGHT.

THE MCS OCCURRING N OF THE FCST AREA AND THE DRY SLOT MOVING IN WILL
ALLOW FOR INSOLATION/DESTABILIZATION. THE APPROACH OF THE UPR TROF
WILL MAINTAIN A FAVORABLE ENVIRONMENT FOR SCATTERED TSTMS ANY TIME
DURING THE DAY...BUT BEST CHANCE DURING/AFTER PEAK HEATING. MLCAPE
2500 J/KG. 0-6 KM SHEAR 20-25 KTS. SEVERE MULTICELLS COULD OCCUR.

FRI: THE HIGHEST PROBABILITIES FOR TSTM INTITIATION WILL BE ENTIRELY
S AND E OF THE FCST AREA. HOWEVER...A FEW TSTMS COULD PRIMARILY S
AND E OF THE TRI-CITIES. MLCAPE NO MORE THAN 1000 J/KG. WEAK WIND
FIELDS WILL RESULT IN 0-6 KM SHEAR 10-15 KTS. PULSE TYPE STORM MODE
SUGGESTS LITTLE RISK OF SEVERE.

SAT: DRY WITH SEASONABLE TEMPS AND COMFORTABLE HUMIDITY. EXCELLENT
FOR OUTDOOR ACTIVITIES.

SAT NIGHT: LOTS OF UNCERTAINTY. THE LLJ WILL DEVELOP. THE QUESTION
IS CONVECTIVE INITIATION. THE GFS AND ITS ENSEMBLES /PROBABILITIES
FOR .05" QPF IN 12 HRS/ ARE ROBUST WHILE THE EC AND ITS ENSEMBLES
SAY NO. MAINTAINED A 20% POP FROM THE 4 AM FCST.

DIFFERENTIAL ADVECTION FROM THE LLJ WILL ADVECT A STOUT ELEVATED
MIXED LAYER /EML/ OVER TOP RICH LOW-LVL DEWPOINTS. THIS WILL RESULT
IN MODERATE INSTABILITY SUN.

SUN: WARM SECTOR WITH A LATE DAY/EVE COOL FRONTAL PASSAGE.

DEPENDS ON IF WE HAVE TO DEAL WITH THE EXITING REMNANTS OF NOCTURNAL
TSTMS. THE LOCATION OF AFTERNOON/EVE TSTMS WILL DEPEND ON THE
LOCATION OF THE FRONT. THIS COULD END UP BEING A SIGNIFICANT SEVERE
EVENT WITH A NEGATIVE TILT TROF AND COUPLED JET STRUCTURE ALOFT. WE
HAVE SEEN THE SPC OUTLOOK FOR DAY 5 WHICH IS A 30% PROB. SO THE
GRAPHICAL HWO HAS BEEN UPDATED WITH AN ELEVATED RISK OF SEVERE.

HIGH TEMPS WERE NUDGE UP 2-3F OVER N-CNTRL KS WITHIN LOW-LVL THERMAL
RIDGE.

MON-WED: FAIR AND DRY. FANTASTIC WX.

MON NIGHT: NOT SURE WHY THE FCST INITIALIZATION HAD 20 POPS IN THE
FCST. THE FRONT WILL BE OVER SRN KS ALONG WITH THE RICH LOW-LVL
MOISTURE. COORDINATED WITH SURROUNDING OFFICES TO DROP THESE POPS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 647 PM CDT WED AUG 27 2014

DETERIORATING CONDITIONS ARE EXPECTED AT THE TERMINALS AS
PREVAILING VFR CIGS WILL LOWER OVER THE NEXT FEW HOURS AND BECOME
MVFR OR WORSE THROUGH THE REMAINDER OF THE PERIOD. EXPECT TO SEE
SHOWERS AND THUNDERSTORMS ACROSS NORTHERN KANSAS AND WESTERN
NEBRASKA WORK THEIR WAY TOWARDS THE LOCAL AREA OVER THE NEXT FEW
HOURS...WITH CIGS DROPPING TO NEAR OR BELOW 1500 FT AGL. IN
ADDITION...WITH ELEVATED DEW POINTS...COULD SEE SOME BR
DEVELOP AS TEMPERATURES DROP OFF...BUT DO NOT EXPECT ANYTHING
DENSE AS WINDS WILL BE NEAR 8 KTS OVERNIGHT. OTHERWISE...DID NOT
TRY AND TIME ANY THUNDERSTORM ACTIVITY AS THEY WILL BE IN THE AREA
FOR AT LEAST THE NEXT 24 HOURS...SO KEPT A VCTS THROUGH THE
ENTIRE FORECAST.


&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...FLASH FLOOD WATCH THROUGH THURSDAY MORNING FOR NEZ039>041-
     046>049-061>064-073>077-082>086.

KS...FLASH FLOOD WATCH THROUGH THURSDAY MORNING FOR KSZ005>007-017-
     018.

&&

$$

UPDATE...ROSSI
SHORT TERM...WESELY
LONG TERM...HALBLAUB/WESELY
AVIATION...ROSSI



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