Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 270959
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
459 AM CDT WED AUG 27 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 459 AM CDT WED AUG 27 2014

ESPECIALLY IN TERMS OF THE DETAILS...WE ARE STARING AT ANOTHER
CHALLENGING 24 HOURS IN TERMS OF LOCATION/TIMING OF THE BEST
RAIN/THUNDERSTORM CHANCES...AND OF COURSE THE ASSOCIATED ISSUES OF
WHETHER OR NOT FLOODING/FLASH FLOODING COULD MATERIALIZE AT SOME
POINT...AND ALSO WHETHER OR NOT THIS AFTERNOON/EVENING COULD
FEATURE A BIT GREATER SEVERE WEATHER THREAT THAN THE PAST FEW DAYS
HAVE...ALTHOUGH THIS WOULD BE CONDITIONALLY TIED TO WHETHER
ENOUGH HEATING/DESTABILIZATION CAN MANAGE TO TAKE PLACE IN THE
WAKE OF EARLY DAY CONVECTION/WIDESPREAD CLOUDS. SO MANY QUESTION
MARKS...

BEFORE GOING ANY FARTHER...WANT TO COVER REASONING BEHIND THE
24-HOUR EXTENSION OF THE PREVIOUSLY ISSUED FLASH FLOOD WATCH FOR
MAINLY THE NORTHEAST QUADRANT OF THE CWA...WHICH NOW RUNS THROUGH
15Z/10AM THURSDAY. THERE WERE A FEW OPTIONS HERE. ONE OF THESE
OPTIONS WOULD HAVE BEEN TO CANCEL THE HEADLINE BASED ON LACK OF
APPRECIABLE RAIN IN THE WATCH AREA SO FAR THIS MORNING...WHILE
ANOTHER OPTION WOULD HAVE BEEN TO SIMPLY LET IT RIDE AS ORIGINALLY
SCHEDULED THROUGH 10AM THIS MORNING. HOWEVER...NEITHER OF THESE
OPTIONS APPEARED FAVORABLE AS THE FORMER MIGHT GIVE THE IMPRESSION
THAT ANY THREAT OF FLOODING IS ALREADY OVER FOR THE WEEK BEFORE
MUCH ADDITIONAL RAIN EVEN FALLS...WHILE THE LATTER WOULD HAVE MADE
IT APPEAR THAT THE "MAIN EVENT" MIGHT BE OVER BY MID-MORNING
TODAY. GIVEN THAT THERE IS AT LEAST DECENT POTENTIAL FOR LOCALLY
HEAVY RAIN EXTENDING WELL BEYOND THIS MORNING INTO TONIGHT/EARLY
THURSDAY...FELT IT WAS PRETTY MUCH UNAVOIDABLE TO EXTEND ANOTHER
24 HOURS AND ACKNOWLEDGE THAT FLOOD ISSUES COULD STILL OCCUR...AT
LEAST ON A LOCALIZED BASIS BUT OF COURSE NOT WITHIN THE ENTIRE
WATCH AREA. LAST BUT NOT LEAST...ANOTHER OPTION WAS TO TACK MORE
COUNTIES ONTO THE EXISTING WATCH. HOWEVER...GIVEN THAT OVERNIGHT
RAINFALL WITHIN THE WESTERN CWA (AT LEAST SO FAR) HAS NOT BEEN
OVERLY IMPRESSIVE WITH RADAR ESTIMATIONS AND LIMITED OBSERVATIONS
SUGGESTING THAT MOST AREAS HAVE ONLY OBSERVED ROUGHLY 1 INCH OR
LESS...WOULD RATHER LET THE NEXT FEW SHIFTS TAKE ANOTHER LOOK AT
RAINFALL POTENTIAL LATER TODAY/TONIGHT BEFORE MAKING THAT CALL. AT
ANY RATE...AT LEAST THE EXISTING WATCH COUNTIES (ESPECIALLY YORK)
ARE THE ONES THAT LIKELY FEATURE THE OVERALL MOST SATURATED
GROUND BASED ON RAIN THAT FELL MONDAY NIGHT.

STARTING WITH THE HERE AND NOW AS OF 0930Z/430 AM...A FAIRLY
EXPANSIVE AREA OF SHOWERS/NON-SEVERE STORMS CONTINUE A SLOWLY BUT
STEADY EAST-NORTHEAST PROGRESS OUT OF THE WESTERN CWA INTO THE
HIGHWAY 281 CORRIDOR COUNTIES...WHILE FAR EASTERN COUNTIES HAVE
LARGELY BEEN LEFT HIGH AND DRY THUS FAR. IN THE MID-UPPER
LEVELS...THE BIG PICTURE STILL FEATURES ACTIVE SOUTHWESTERLY FLOW
OVER THE LOCAL AREA...WELL OUT AHEAD OF A PARENT CLOSED LOW
EVIDENT AT 500 MILLIBARS CHURNING SLOWLY EASTWARD ACROSS UT. OUT
AHEAD OF THIS MAIN LOW...A SERIES OF LOW AMPLITUDE DISTURBANCES
ARE TRACKING EAST-NORTHEAST INTO THE CENTRAL PLAINS...WITH ONGOING
CONVECTION LARGELY TIED TO THE LEADING EDGES OF ONE OF THESE
SHORTWAVES CURRENTLY PASSING THROUGH THE CO/KS/NEB BORDER
AREA...ALONG WITH HELP FROM A MODEST LOW LEVEL JET AT 850
MILLIBARS AND INCREASING MID LEVEL ISENTROPIC LIFT/SATURATION
EVIDENT ON THE 310K SURFACE. THUNDERSTORM INTENSITY OVERNIGHT HAS
BEEN HELD IN CHECK BY LIMITED ELEVATED INSTABILITY GENERALLY ONLY
500-1000 J/KG IN THE PRESENCE OF FAIRLY TALL/NARROW CAPE PROFILES
IN THE PRESENCE OF RATHER POOR MID LEVEL LAPSE RATES. AT THE
SURFACE...APART FROM CONVECTIVE INFLUENCES GENERALLY EASTERLY
BREEZES OF 56-10 MPH PREVAIL TO THE NORTH OF THE MAIN EAST-WEST
QUASI-STATIONARY FRONT LOOSELY DRAPED NEAR THE I-70 CORRIDOR IN
KS. LOW TEMPS THIS MORNING ARE ON TRACK TO BOTTOM OUT IN THE 65-70
RANGE MOST AREAS.

LOOKING AHEAD INITIALLY INTO THE MORNING HOURS...WILL MAINTAIN A
GENERIC MENTION OF NON-DENSE PATCHY FOG UNTIL SHORTLY PAST SUNRISE
WITHIN NORTHEAST COUNTIES AHEAD OF THE MAIN BATCH OF
CONVECTION...BUT THIS MAY BE DROPPED AHEAD OF SCHEDULE ON THE NEXT
UPDATE AS CONVECTION MOVES IN AND STIRS OUT ANY LIGHT FOG THAT
MIGHT EXIST. OTHERWISE...IN THE BIG PICTURE THROUGH THE DAYLIGHT
HOURS...THE SLOW-MOVING SHORTWAVE TROUGH CURRENTLY CENTERED
SLIGHTLY WEST OF THE CWA WILL CONTINUE LIFTING SLOWLY EAST-
NORTHEAST OVER THE AREA...WHILE THE MAIN LOW TO THE WEST REACHES
THE NORTHWEST CO AREA BY SUNSET. AS WAS THE CASE LAST NIGHT...HAVE
RELIED MORE HEAVILY THAN USUAL ON THE HIGHER-RES SIMULATED
REFLECTIVITY PROGS OF MODELS SUCH AS THE 00Z 4KM WRF-NMM AND NSSL
4KM WRF FOR HOW THINGS PLAY OUT TODAY. VERY GENERALLY
SPEAKING...EXPECT FAIRLY WIDESPREAD COVERAGE OF SHOWERS/NON-SEVERE
THUNDERSTORMS TO OVERSPREAD THE AREA THROUGH THIS MORNING...BUT
WITH AREAL COVERAGE OF PRECIP GRADUALLY DECREASING FROM SOUTHWEST
TO NORTHEAST BEHIND THE MAIN BAND. THAT BEING SAID...AT LEAST
RANDOM SPOTTY RE-DEVELOPMENT CANNOT BE RULED OUT AT ANY POINT
TODAY...AND THUS HAVE MAINTAINED AT LEAST 40-50 POPS FOR THIS
AFTERNOON IN THE WAKE OF THE HIGHER LIKELY POPS THIS MORNING. BY
THE MID-LATE AFTERNOON HOURS...THE NEXT ISSUE BECOMES WHETHER OR
NOT ENOUGH DESTABILIZATION CAN TAKE PLACE PRIMARILY WITHIN THE
SOUTHERN CWA TO PROMOTE AT LEAST A LIMITED SEVERE WEATHER
RISK...WITH THE 06Z NAM SUGGESTING UP TO AROUND 2000 J/KG MIXED-
LAYER CAPE IN THE PRESENCE OF UP TO AROUND 35KT OF DEEP LAYER
SHEAR. CERTAINLY WITH BETTER LARGE SCALE FORCING EXPECT A GREATER
COVERAGE OF LATE AFTERNOON/EARLY EVENING CONVECTION THAN SEEN THE
PAST FEW DAYS...BUT AM CURRENTLY QUESTIONING JUST HOW MUCH
DESTABILIZATION MIGHT REALLY TAKE PLACE. CANNOT ARGUE TOO MUCH
WITH THE SPC DAY 1 SLIGHT RISK AREA FOR NEARLY THE ENTIRE
CWA FOR HAIL/WIND POTENTIAL...BUT HAVE DOUBTS THAT TORNADIC
DEVELOPMENT WILL BECOME MUCH OF AN ISSUE UNLESS SOMETHING TRACKS
DIRECTLY ALONG THE SURFACE FRONT MAINLY NEAR/WITHIN OUR
SOUTHWESTERN CWA. OBVIOUSLY DAY SHIFT WILL GET A BETTER HANDLE ON
WHETHER THIS IS MORE OF A LIMITED OR POTENTIALLY SOMEWHAT MORE
ROBUST THREAT AS MESOSCALE DETAILS PLAY OUT. TEMP-WISE...AGAIN
TOOK A FAIRLY LOW-CONFIDENCE STAB USING A BLEND OF MODEL
GUIDANCE...WHICH ACTUALLY WORKED REASONABLY WELL FOR YESTERDAY.
THIS YIELDS A RANGE FROM MID 70S NORTH...80S NEAR THE STATE LINE
AND NEAR 90 FAR SOUTH.

TURNING TO THE EVENING/OVERNIGHT HOURS...DECENT/INCREASING LARGE
SCALE FORCING CONTINUES AS THE INITIAL SHORTWAVE DISTURBANCE FROM
TODAY GRADUALLY DEPARTS NORTHEAST...WHILE THE MAIN LOW OVER CO
EDGES EVER-CLOSER TO THE LOCAL AREA. COMPARED TO THIS MORNING...A
STRONGER LOW LEVEL JET IS ANTICIPATED ALTHOUGH THE NOSE OF THIS
JET APPEARS TO AIM INCREASINGLY NORTH AND EAST OF THE CWA AS THE
NIGHT GOES. VERY GENERALLY THEN...AND AGAIN LEANING ON SIMULATED
REFLECTIVITY PROGS...EXPECT FAIRLY WIDESPREAD SHOWER/STORM
COVERAGE DURING THE EVENING WITH SOME POTENTIALLY STRONG TO SEVERE
EARLY ON...BEFORE CONVECTION GRADUALLY DIMINISHES IN COVERAGE
AND/OR DEPARTS MORE TO THE NORTH/EAST OF THE AREA LATER IN THE
NIGHT. THAT BEING SAID...CERTAINLY CANNOT RULE OUT ANY LOCATION
SEEING A PASSING SHOWER/STORM AT ANY POINT IN THE NIGHT...SO KEPT
AT LEAST 50 POPS ALL AREAS. HAVE LITTLE DOUBT THAT SOME AREAS
COULD EASILY RECEIVE 1-2+ INCHES OF RAIN IN A SHORT TIME FROM LATE
THIS AFTERNOON INTO TONIGHT ON TOP OF WHAT FALLS EARLY TODAY...BUT
AS MENTIONED EARLIER THE SITUATION JUST DOES NOT SEEM OMINOUS
ENOUGH FOR WIDESPREAD HEAVY RAIN TO JUSTIFY AN EXPANSION OF THE
CURRENT FLASH FLOOD WATCH AREA. MADE VERY LITTLE CHANGE TO LOW
TEMPS...EXPECTING MOST AREAS TO BOTTOM OUT BETWEEN 64-68.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 459 AM CDT WED AUG 27 2014

CONVECTION COULD EASILY BE ONGOING TO START THE DAY ON THURSDAY IN
GOOD LIFT/WAA AHEAD OF AN UPPER LOW PRESSURE SYSTEM MOVING OUT OF
COLORADO ONTO THE HIGH PLAINS.  THE GFS/12Z ECMWF CLOSE OFF THE
CIRCULATION ON THURSDAY...WHEREAS THE NAM/00Z ECMWF ARE MORE
PROGRESSIVE AND KEEP THE SYSTEM AS AN UPPER WAVE. THE DEEPER SLOWER
TROUGH SOLUTION WILL MAINTAIN PCPN CHCS LONGER ACROSS OUR REGION
THAN THE MORE PROGRESSIVE/OPEN TROUGH SOLUTIONS.  GIVEN THE MODEL
SOLUTIONS...HAVE GENERALLY WENT WITH A MODEL BLEND.

WITH THE UPPER LOW GRADUALLY MOVING EAST ACROSS THE CENTRAL PLAINS
THURSDAY THROUGH FRIDAY...GOOD CHANCES FOR CONVECTION REMAIN FOR OUR
REGION.  INSTABILITY DECREASES FROM THURSDAY TO FRIDAY AND SHEAR
PARAMETERS ARE UNDER 30KTS...SO WHILE THUNDERSTORM DEVELOPMENT IS
EXPECTED...SEVERE WEATHER LOOKS MORE HIT OR MISS.  HEAVY RAINFALL
REMAINS A CONCERN WITH PRECIPITABLE WATER VALUES AVERAGING AN INCH
AND A HALF TO TWO INCHES AND CURRENT PRECIPITABLE WATER VALUES ARE
AROUND 150 PERCENT OF NORMAL. THE POTENTIAL FOR ADDITIONAL HEAVY
RAINFALL ON SATURATING/SATURATED GROUND MAY LEAD TO LOCALIZED
FLOODING.

THE UPPER LOW PRESSURE SYSTEM DEPARTS TO THE EAST FRIDAY NIGHT AT
THE LATEST WITH THE FORECAST DRYING OUT W/E BEHIND THE EXITING
TROUGH. THE PATTERN ALOFT TRANSITIONS MORE ZONAL OVER THE WEEKEND
WITH TEMPS TRENDING BACK UP NEAR/ABOVE SEASONAL NORMALS.
UPSTREAM...ANOTHER TROUGH WILL REACH THE PACIFIC NORTHWEST AND
TRANSLATE EASTWARD TOWARD/ACROSS THE PLAINS LATE IN THE WEEKEND AND
EARLY NEXT WEEK. FOR THE OUTER PERIOD THERE ARE SOME DIFFERENCES IN
THE STRENGTH/TIMING OF THE TROUGH AND DID NOT DEVIATE FM THE
EXTENDED INIT ATTM WITH A CHANCE FOR STORMS RETURNING AROUND THE
SUNDAY OR SUNDAY NIGHT TIME FRAME AND CONTINUING INTERMITTENTLY NEXT
WEEK.

&&

.AVIATION...(FOR THE 06Z KGRI/KEAR TAFS THROUGH 06Z WEDNESDAY)
ISSUED AT 127 AM CDT WED AUG 27 2014

ANOTHER CHALLENGING 24 HOURS AWAITS FORECAST-WISE...WITH PLENTY
OF UNCERTAINTY IN NOT ONLY CEILING/VISIBILITY TRENDS...BUT ALSO
THUNDERSTORM COVERAGE. IN THE MOST BASIC SENSE...THE BIGGEST
CHANGES FROM THE PREVIOUS TAF ISSUANCE IS THAT THUNDERSTORM
POTENTIAL WAS DELAYED SEVERAL HOURS...AND CEILING TRENDS WERE MADE
MORE PESSIMISTIC WITH AT LEAST PATCHY IFR CEILING AND MVFR
VISIBILITY IN LIGHT FOG ALREADY SHOWING THEIR HAND ACROSS THE
AREA OUT OF THE GATE. THERE IS PLENTY OF UNCERTAINTY ON HOW LONG
THESE LOWER CEILING/VISIBILITY MIGHT LAST INTO THE DAYTIME
HOURS...AND AT LEAST FOR NOW HAVE PREVAILING VFR CONDITIONS
RETURNING FROM 16Z ONWARD. AS FOR SHOWER/THUNDERSTORM
CHANCES...THE BOTTOM LINE IS THAT ITS ALMOST IMPOSSIBLE TO RULE
OUT ACTIVITY AT ANY POINT DURING THE PERIOD BEYOND THE FIRST FEW
HOURS...AND THUS HAVE A LONG-FUSE MENTION OF A GENERIC VICINITY
THUNDERSTORM (VCTS). IN THE SHORTER TERM...MAINTAINED A TEMPO
GROUP FOR STEADIER THUNDERSTORM ACTIVITY THIS MORNING BUT DELAYED
THIS UNTIL THE 09Z-13Z TIME FRAME. AS FOR SURFACE WINDS...OUTSIDE
OF ANY POSSIBLE CONVECTIVE INFLUENCES THEY SHOULD NOT BE MUCH OF
AN ISSUE WITH DIRECTION GENERALLY REMAINING SOME COMPONENT OF
EASTERLY AND SPEEDS LARGELY AVERAGING AROUND 10KT OR LESS. IN
CLOSING...STAY TUNED FOR PLENTY OF FINE-TUNING OF VARIOUS
ELEMENTS OVER THE NEXT FEW DAYS AS THE PRIMARY LOW PRESSURE SYSTEM
WORKS ITS WAY OUT OF THE ROCKIES AND ACROSS THE CENTRAL PLAINS.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...FLASH FLOOD WATCH THROUGH THURSDAY MORNING FOR NEZ039>041-
     046>049-062>064-075-076.

KS...NONE.
&&

$$

SHORT TERM...PFANNKUCH
LONG TERM...FAY
AVIATION...PFANNKUCH


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