976
FXUS63 KLBF 291742
AFDLBF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1242 PM CDT THU JUL 29 2021
UPDATE
ISSUED AT 1215 PM CDT THU JUL 29 2021
NDOR CAMERAS SHOW SMOKE FROM SD IS BEGINNING TO DRIFT INTO NCNTL
NEBRASKA. A FORECAST UPDATE IS IN PLACE FOR AREAS OF SMOKE.
A CHECK ON THE 12Z RAP AND HRRR MODEL NEAR SURFACE SMOKE
FORECASTS SUGGESTS THE THICK PLUME OF TRAPPED NEAR SFC SMOKE
ACROSS ERN SD WILL DROP SOUTH INTO NORTHERN NEBRASKA THIS
AFTERNOON, TONIGHT AND POSSIBLY REMAIN IN PLACE DURING THE DAY
FRIDAY. THE MODELS PROVIDE A 48 HOUR FORECAST AND SUGGEST THE
SMOKE WILL PARTIALLY MIX OUT FRIDAY. THE SMOKE IS TRAPPED IN AN
INVERSION LAYER BELOW 700MB.
SHORT TERM
(TODAY THROUGH FRIDAY)
ISSUED AT 414 AM CDT THU JUL 29 2021
FORECAST CONCERNS FOCUS ON HIGH HEAT ACROSS PORTIONS OF THE AREA.
THEN, ATTENTION TURNS TO INCOMING DISTURBANCE EXPECTED TO BRING A
PERIOD OF RAIN AND THUNDERSTORMS TO THE AREA INCLUDING THE THREAT
FOR ISOLATED STRONG TO BRIEFLY SEVERE THUNDERSTORMS.
MORNING RADAR AND SATELLITE ANALYSIS DEPICTS A SURFACE COOL FRONT
BISECTING MUCH OF NEBRASKA. THIS BOUNDARY WILL CONTINUE TO DRIVE
SOUTH AS LOW-LEVEL FLOW CONTINUES TO PUSH IT THROUGH THE AREA. WE'VE
SEEN A FEW ECHOES DEVELOP ALONG AND IMMEDIATELY BEHIND THE INITIAL
WIND SHIFT LINE WITH MORE SUSTAINED CONVECTION OCCURRING WELL EAST
OF THE AREA. THOUGH AN ISOLATED SHOWER OR WEAK THUNDERSTORM CANNOT
BE RULED OUT THROUGH SUNRISE, BELIEVE THIS THREAT IS TOO LOW TO
WARRANT MAINTAINING POPS. AS SUNRISE APPROACHES AND KINEMATICS
DIMINISH, EXPECT THIS FRONTAL BOUNDARY TO STALL GENERALLY AROUND OR
JUST NORTH OF THE I-80 CORRIDOR. THIS WILL LEAD TO A DIVIDE ACROSS
THE LOCAL AREA WILL NEAR-SEASONABLE TEMPERATURES TO THE NORTH AND
CONTINUED HEAT AND HUMIDITY TO THE SOUTH. THE HOTTEST TEMPERATURES
WILL ONCE AGAIN REACH THE UPPER 90S TO NEAR 100 DEGREES AND COMBINED
WITH AFTERNOON DEW POINTS IN THE 60S, HEAT INDEX VALUES APPROACHING
ADVISORY LEVELS WILL AGAIN BE SOMETHING TO WATCH. MOISTURE POOLING
ALONG THE BOUNDARY MAY ENHANCE A SMALL AREA OF MOISTURE QUALITY AND
LEAD TO A BRIEF PERIOD OF HEAT INDICES APPROACHING OR TOUCHING 100
DEGF, HOWEVER, THIS IS LIKELY TO BE CONFINED TO PERHAPS AN HOUR OR
TWO IN THE EARLY AFTERNOON AND WITH THE POTENTIAL FOR CONVECTION AND
CLOUD COVER, CONFIDENCE WAS TOO LOW IN SEEING ANYTHING PROLONGED
ENOUGH TO WARRANT ANY HEADLINES. NEVERTHELESS, HIGH TEMPERATURES IN
THE MID TO UPPER 90S ARE NOTHING TO SCOFF AT AND THOSE WITH PLANS
THAT INCLUDE PROLONGED EXPOSURE TO THE HEAT SHOULD EXERCISE CAUTION
AND TAKE APPROPRIATE MEASURES TO KEEP THEMSELVES SAFE IN THE
ELEMENTS. FOR AREAS NORTH OF THE BOUNDARY, COOLER EASTERLY FLOW FROM
AN APPROACHING CANADIAN HIGH PRESSURE SYSTEM SHOULD KEEP
TEMPERATURES MUCH COOLER THAN WHAT WAS SEEN WEDNESDAY, EVEN THOUGH
HIGH TEMPERATURES ARE STILL FORECAST TO BE IN THE UPPER 80S TO LOW
90S WHICH IS NEAR TO SLIGHTLY ABOVE NORMAL FOR LATE JULY.
REGARDING THE THUNDERSTORM POTENTIAL...THE AFOREMENTIONED SURFACE
BOUNDARY WILL STALL NEAR THE I-80 CORRIDOR. FORECAST SOUNDINGS
INDICATE DEEP MIXING...UP TO AROUND H6...ACROSS SOUTHWEST NEBRASKA
WITH DRIER AIR ARRIVING FROM THE NORTH OF THE HIGHWAY 20 CORRIDOR.
THIS PLACES MUCH OF OUR CENTRAL ZONES, STRETCHING FROM THE EASTERN
PANHANDLE THROUGH THE SANDHILLS INTO PORTIONS OF CENTRAL NEBRASKA IN
LOW-LEVEL EASTERLY FLOW AND THUS A NARROW CORRIDOR OF HIGHER
HUMIDITY WITH THE GREATEST MOISTURE QUALITY BEING NORTH OF THE
BOUNDARY. THOUGH FLOW ALOFT IS RATHER WEAK, THE ORIENTATION OF NEAR
EASTERLY SURFACE WINDS AROUND 10 TO 15 KNOTS AND WESTERLY FLOW ALOFT
(AROUND 10 TO 15 KNOTS IN THE H5-H4 LAYER) WILL BE SUFFICIENT ENOUGH
TO LEAD TO DEEP LAYER SHEAR OF AROUND 20 TO POTENTIALLY 30 KNOTS.
NWP GUIDANCE IS IN GOOD AGREEMENT IN DEVELOPING 2000-3000 J/KG
MLCAPE ALONG A NARROW CORRIDOR FOLLOWING THE PLATTE RIVER VALLEY.
WHILE THIS IS MORE THAN ADEQUATE, SOME LIMITING FACTORS INVOLVE A
MODEST WARM NOSE NEAR H5 WHICH LIMIT MORE FAVORABLE LAPSE RATES FROM
DEVELOPING. THIS MAY INHIBIT UPDRAFTS SLIGHTLY BUT SHOULD ONE
DEVELOP AND SUSTAIN ITSELF, ISOLATED HAIL UP TO 1" WILL BE POSSIBLE.
DAMAGING WIND GUSTS UP TO 60 MPH WOULD ALSO BE POSSIBLE WITH
INVERTED-V FORECAST SOUNDINGS AND DCAPE VALUES EXCEEDING 1000 J/KG.
LIFT WILL BE RATHER WEAK WITH ONLY A WEAK PERTURBATION AT H5
EXPECTED TO APPROACH THE AREA AND MID-LEVEL HEIGHTS NEARLY
STAGNANT...THEREFORE THINKING COVERAGE WILL BE LIMITED TO ISOLATED
AND PERHAPS WIDELY SCATTERED WITH DECREASING POTENTIAL HEADING INTO
THE EVENING HOURS. IDEAS GENERALLY LINE UP WITH THE LATEST SPC DAY 1
MARGINAL RISK FOR THE PANHANDLE STRETCHING EAST TO HIGHWAY 83.
POPS WILL DECREASE THROUGH THE EVENING HOURS FOR AREAS SOUTH OF
HIGHWAY 2, BUT WILL INCREASE FOR AREAS NORTH AS THE MID-LEVEL RIDGE
BEGINS TO FLATTEN WITH THE APPROACH OF A MODEST SHORTWAVE AT H5.
BOTH THE NAM AND GFS INDICATE STRONG POTENTIAL VORTICITY ADVECTION
GRAZING THE NORTHERN ZONES OF THE LOCAL AREA. THIS WILL LEAD TO LEE-
CYCLOGENESIS ACROSS NORTHEAST COLORADO WITH AN INVERTED SURFACE
TROUGH BEGINNING ACROSS THE NEBRASKA PANHANDLE, TRACKING SOUTH
THROUGH THE AREA THROUGH THE DAY FRIDAY. PRECIPITATION CHANCES WILL
BE GREATEST TO THE NORTH, CLOSER TO THE PV ANOMALY WITH GRADUAL
SOUTHWARD EXPANSION MORE CLOSELY TIED TO THE DEVELOPING LOW-LEVEL
FGEN. SPC HAS OPTED TO REMOVE THE DAY 2 MARGINAL RISK FROM THE LOCAL
AREA AND AGREE WITH THIS AS THE GREATEST CORRIDOR OF INSTABILITY
LOOKS TO REMAIN ACROSS EASTERN NEBRASKA. GIVEN HIGH PRECIPITABLE
WATER VALUES EXCEEDING 1.75" IN SPOTS, BELIEVE LOCALLY HEAVY RAIN
PRIMARILY ACROSS NORTH CENTRAL NEBRASKA WILL BE POSSIBLE AND THIS
LINES UP WELL WITH THE WPC DAY 2 ERO MARGINAL RISK. WITH STRONG
FORCING FROM THE MID-LEVEL DISTURBANCE, WIDESPREAD RAIN EXCEED 0.5"
APPEARS LIKELY WITH A FEW LOCATIONS POTENTIALLY TOPPING 1.5" THROUGH
LATE FRIDAY NIGHT. DAYTIME HIGHS ON FRIDAY WILL RANGE FROM THE UPPER
70S FOR AREAS EXPECTED TO SEE MORE WIDESPREAD RAIN AND THUNDERSTORMS
TO UPPER 90S ONCE AGAIN FOR MUCH OF SOUTHWEST NEBRASKA WHERE HEAT
INDEX VALUES WILL AGAIN CLIMB INTO THE UPPER 90S TO NEAR 100 DEGF.
LONG TERM
(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 414 AM CDT THU JUL 29 2021
BEGINNING 00Z SATURDAY. DEEPER TROUGHING ACROSS THE NORTHEAST CONUS
WILL BEGIN TO RETROGRADE SLIGHTLY WITH A FEW IMPULSES DROPPING
THROUGH THE MERIDIONAL FLOW ALOFT. THIS DISTURBANCES LOOK TO REMAIN
WELL EAST OF THE AREA, HOWEVER, WITH SURFACE HIGH PRESSURE BUILDING
INTO THE GREAT LAKES BY LATE SUNDAY. THIS WILL LARGELY SHUNT THE
GREATEST MOISTURE SOUTH AND WEST OF THE LOCAL AREA, LIMITING
PRECIPITATION CHANCES OVER THE WEEKEND AND BRINGING IN COOLER THAN
NORMAL TEMPERATURES FOR SATURDAY AND SUNDAY. PRECIPITATION CHANCES
WILL BE LIMITED TO THE PANHANDLE REGION INTO FAR SOUTHWEST NEBRASKA
WITHIN UPSLOPE REGIMES. HOW FAR EAST THIS ACTIVITY CAN MAKE IT
REMAINS IN QUESTION BUT WILL LEAVE INHERITED POPS FROM THE MODEL
BLEND AS IS FOR NOW WHICH KEEPS THINGS GENERALLY LIMITED TO 25% OR
LESS FOR ANY ONE PARTICULAR LOCATION. AS THE SURFACE HIGH PRESSURE
SLOWLY SHIFTS SOUTH AND EAST EARLY NEXT WEEK, LOW-LEVEL SOUTH TO
SOUTHWESTERLY FLOW WILL REDEVELOP LOCALLY WHICH WILL HELP
TEMPERATURES MODERATE HEADING INTO THE MIDDLE OF NEXT WEEK WHILE
REINTRODUCING MOISTURE ADVECTION AND THUS MORE WIDESPREAD POPS FOR
TUESDAY AND WEDNESDAY WHEN HIGHS ALSO RETURN TO THE MID TO UPPER
80S. A FEW MORE DISTURBANCES LOOKS TO TRACK THROUGH THE PLAINS FOR
THE LATTER HALF OF NEXT WEEK WHICH WILL KEEP THE FORECAST FROM BEING
DRY. THOUGH ENSEMBLE OUTPUT VARIES A BIT ON TEMPERATURES, BOTH THE
GEFS AND EPS ADVERTISE A RETURN TO ABOVE NORMAL TEMPERATURES AROUND
THE FIRST WEEKEND OF AUGUST, TO WHAT DEGREE REMAINS MORE
UNCERTAIN.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1242 PM CDT THU JUL 29 2021
SOME UNCERTAINTY LIES IN THE AVIATION FORECAST, MAINLY VISIBILITY
FROM WILDFIRE SMOKE AND THE PROSPECTS OF THUNDERSTORMS. FIRST THE
SMOKE, LATEST IMAGERY SHOWS AN EXPANSIVE PLUME OF CANADIAN SMOKE
DROPPING SOUTH ATOP THE PLAINS. THE LATEST HRRR SMOKE IS CORRECTLY
PROJECTING MUCH OF THIS SMOKE IMPACTING TERMINALS WITH 1SM
VISIBILITY AT TIMES. WHILE THE BRUNT OF THE SMOKE IS PORTRAYED TO
DRIFT OFF TO THE EAST OF OUR TWO TAF SITES, ENOUGH MAY IMPACT KVTN
AND POSSIBLY KLBF. QUESTION HOW LOW VISIBILITY WILL FALL, SO WILL
START WITH 5SM AT KVTN AS WE ARE EXPECTING A GLANCING BLOW, BUT
MAY NEED UPDATES. FOR KLBF, WILL KEEP THE PREVAILING AT P6SM, BUT
MONITOR. AS FOR THE CONVECTIVE ELEMENT, ISOLATED STORMS CANNOT BE
RULED OUT, BUT WITH A LACK OF A CLEAR FOCUS, TIMING AND LOCATION
IS MUDDLED. THE LATEST CAMS SUGGEST BEST CHANCES ACROSS THE
PANHANDLE, SO WILL KEEP THE FORECAST VOID OF TS AT BOTH KVTN AND
KLBF FOR NOW.
LBF WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...CDC
SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...JACOBS
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