404
FXUS63 KGID 131153
AFDGID
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
653 AM CDT MON JUL 13 2020
SHORT TERM
(TODAY THROUGH TUESDAY NIGHT)
ISSUED AT 507 AM CDT MON JUL 13 2020
MAIN FOCUS IS THE POTENTIAL FOR SEVERE THUNDERSTORMS, INCLUDING
DAMAGING WIND GUSTS, THIS EVENING INTO OVERNIGHT.
EXPECT DRY CONDITIONS THROUGH MID AFTERNOON. SRLY WINDS WILL INCR BY
LATE AM IN RESPONSE TO TIGHTENING PRESSURE GRADIENT AS SFC RIDGING
QUICKLY SHIFTS E INTO MID MS VALLEY, AND LEE TROUGHING DEEPENS OVER
THE HIGH PLAINS. WAA, GOOD MIXING, AND PLENTIFUL SUNSHINE WILL HELPS
HIGHS CLIMB WELL INTO THE 90S, WITH NEAR TRIPLE DIGITS NOT OUT OF
THE QUESTION FOR FURNAS, PHILLIPS, AND ROOKS COUNTIES.
A SEASONABLY STRONG UPPER LOW WILL MIGRATE E ACROSS S CANADA THRU
THE DAYTIME, LEADING TO HEIGHT FALLS/MID LEVEL COOLING SUCH THAT
TSTMS WILL LIKELY INITIATE ACROSS HIGHER TERRAIN OF WY/CO BY EARLY
TO MID AFTN IN THE MIDST OF STEEP LOW LEVEL LAPSE RATES. THIS
ACTIVITY WILL LIKELY BECOME ORGANIZED MID TO LATE AFTN AS IT SHIFTS
EASTWARD COINCIDENT THE SOUTHERN FRINGES OF A 50-60KT H5 SPEED MAX
OVER WY/SD, AND ENCOUNTERS AN INCREASINGLY MOIST AND UNSTABLE BL
WITH ML CAPE VALUES IN EXCESS OF 3000 J/KG OWING TO TDS IN THE 60S
TO NEAR 70F AND STEEP LOW TO MID TROPOSPHERIC LAPSE RATES. A
SOUTHWARD SINKING COLD FRONT WILL PROVIDE ADDITIONAL LIFT AMIDST THE
STRONG INSTABILITY AND WEAKENING CIN, IN THE PRESENCE OF A LARGE
RESERVOIR OF DCAPE VALUES 1500-2000 J/KG AHEAD OF THE FRONT, SUCH
THAT UPSCALE GROWTH INTO A LINE OR BROKEN LINE WITH INCREASING
DAMAGING WIND THREAT IS QUITE LIKELY. MODELS KEEP THIS ACTIVITY JUST
W OF THE CWA THRU 22Z-23Z, THEN SURGE IT E/NE IN THE 00Z-06Z TIME
FRAME. THIS WILL LIKELY BE THE TIME FRAME OF GREATEST SEVERE RISK,
WITH DAMAGING WIND GUSTS OF 60-70MPH THE MAIN THREAT. THE HIGH END
OF THE SEVERE RISK (I.E. WIND GUSTS UP TO 80MPH) AS WELL AS THE
LONGEVITY (AND THUS EASTWARD EXTENT OF SEVERE RISK WITH TIME), WILL
DEPEND ON MESOSCALE FEATURES SUCH AS COLD POOL STRENGTH AND TO WHAT
DEGREE A LIKELY MCV CAN MODULATE THE MID LEVEL KINEMATIC FIELDS.
WOULD ALSO EXPECT A DEVELOPING LLJ TO PLAY A ROLE, BUT MODELS ARE
NOT IN GREAT AGREEMENT W/ MAGNITUDE/ORIENTATION, WHICH ADDS
UNCERTAINTY. CAMS ARE IN PRETTY GOOD AGREEMENT WITH A WSW-ENE
MOVEMENT OF TSTMS, WHICH ALIGNS WELL W/ LOW TO MID LEVEL SHEAR
VECTORS INITIALLY, BUT WITH TIME, CORFIDI AND 1-3KM SHEAR VECTORS
TURN AND WOULD ARGUE FOR MORE S/SE DEVELOPMENT LATER ON.
SOME CAMS (SUCH AS HRRR/HRRRX) DEVELOP ADDITIONAL ELEVATED
TSTMS, MAINLY AFTER 05Z, ATOP THE COLD POOL LAID DOWN BY INITIAL
ACTIVITY. THIS COULD POSE A MARGINAL HAIL RISK IF SUFFICIENT
ELEVATED CAPE REMAINS AS CLD BEARING SHEAR WILL REMAIN STRONG.
HOWEVER, THIS IS LIKELY CONDITIONAL UPON LLJ DEVELOPMENT AND
EVOLUTION WHICH, AGAIN, REMAINS UNCERTAIN.
EXPECT CONVECTION TO BE LARGELY E OF THE CWA BY 12Z TUE. ATTENTION
THEN TURNS TO A STRONG COLD FRONT MOVING IN FROM THE N. 1015-1018MB
SFC HIGH PRESSURE NOSING S FROM BLACK HILLS INTO NEB. PANHANDLE WILL
AID IN A SURGE OF UNSEASONABLY COOL AIR DURING THE AFTN. HAVEN'T
GONE WITH A NON-DIURNAL TEMP TREND IN THE N YET, BUT THESE AREAS
MAY NEED ONE GIVEN MAGNITUDE OF CAA AND POTENTIAL FOR SEVERAL HRS
OF STRATUS ASSOCIATED W/ MOISTURE STUCK BELOW A STRONG FRONTAL
INVERSION. GOING HIGHS IN THE N ARE ONLY MID 70S. FURTHER S,
SLOWER ARRIVAL OF FRONT AND COMPRESSIONAL HEATING WILL PROBABLY
LEAD TO A QUICK WARMUP FROM BELOIT TO HEBRON. AS FOR TSTM CHCS
ALONG THE FRONT, VERY WARM MID LEVEL TEMPS (15-16C AT H7) LOOKS TO
KEEP THINGS CAPPED OFF, AND THE BETTER MOISTURE WILL PROBABLY
POOL FURTHER SE CLOSER TO COMPOSITE FRONT/OUTFLOW FROM MON NIGHT
ANOTHER DISTURBANCE IN THE ZONAL FLOW WILL ROLL E OFF THE
ROCKIES/CENTRAL HIGH PLAINS TUE NIGHT. INCREASING LLJ/CONVERGENCE
INVOF PROBABLY LEAD TO SOME SORT OF WSW TO ENE MOVING MCS, ALONG AN
ELEVATED FRONTAL ZONE. MUCAPE NEAR 2000 J/KG AMIDST 35-40KT OF
EFFECTIVE SHEAR AND COOL SFC TEMPS COULD LEAD TO SOME MARGINAL
HAILERS, MAINLY ALONG AND S OF THE NE/KS STATE LINE. POOLING
MOISTURE COULD ALSO LEAD TO IMPRESSIVE RAIN RATES, BUT THESE AREAS
MAY EASILY MISS OUT ON TONIGHT'S CONVECTION, AND SOIL IS NOT OVERLY
SATURATED EITHER, THUS NOT EXPECTING SIGNIFICANT HYDRO ISSUES.
LONG TERM
(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 507 AM CDT MON JUL 13 2020
TEMPERATURES ARE THE MAIN FORECAST CONCERN IN THE EXTENDED.
NOT MUCH TIME SPENT IN THE EXTENDED GIVEN CONVECTION CONCERNS IN THE
SHORT TERM. EXPECT CONTINUED COOL CONDITIONS WED WITH LINGERING
CLDS/PCPN CHCS IN THE MORNING, THEN ANOTHER 1015-1018MB SFC RIDGE
AXIS THAT WILL LIMIT MIXING. ASSUMING THE CLDS CLEAR OUT, WED AFTN
COULD BE VERY NICE BY MID JULY STANDARDS, ESP NE ZONES, W/ PLEASANT
TEMPS AND LOW HUMIDITY.
DETERMINISTIC AND ENSEMBLES ARE IN GOOD AGREEMENT SHOWING A STRONG
WARMING TREND FOR THE SECOND HALF OF THE WEEK. COULD SEE SOME TSTMS
THU WITHIN WAA REGIME, BUT THIS IS LOW CONFIDENCE. WIDESPREAD 90S
ARE FORECAST FRI, WITH EVEN WARMER UPPER 90S TO LOW 100S ON SAT.
WILL NEED TO KEEP AN EYE ON FORECAST TD TRENDS FOR POSSIBLE HEAT
ADVISORY LEVEL HEAT INDICES. EC/GFS VARY ON WINDS/MIXING/SFC
MOISTURE FIELDS, BUT EVAPOTRANSPIRATION ALONE THIS TIME OF YEAR
COULD LEAD TO MID TO UPPER 60S TDS, LOCALLY 70, ESP. E HALF OF CWA.
SUN COULD BE ANOTHER HOT ONE BEFORE POTENTIALLY COOLER AIR ARRIVES 7-
8 DAYS FROM NOW, THOUGH THERE IS CONSIDERABLE SPREAD IN ENSEMBLE
OUTPUT BY THEN.
AVIATION
(FOR THE 12Z KGRI/KEAR TAFS THROUGH 12Z TUESDAY)
ISSUED AT 650 AM CDT MON JUL 13 2020
SIGNIFICANT WX: STRONG-SEVERE TSTMS WITH DAMAGING WIND GUSTS POSS
THIS EVE.
TODAY: VFR. ANY LINGERING LLWS WILL QUICKLY MIX OUT W/IN NEXT HR
AS SRLY SFC WINDS INCR. GUSTS UP TO 25KT EXPECTED. MAY SEE A FEW
CU AND CIRRUS THIS AFTN. CONFIDENCE: HIGH.
TONIGHT: TSTMS ARE EXPECTED TO ROLL IN FROM THE WEST IN THE 02Z TO
04Z TIME FRAME. SEVERE W-NW GUSTS AND BRIEF MVFR VSBY/CIG
REDUCTIONS ARE POSSIBLE WITH THIS LINE, BUT THIS IS NOT YET
REFLECTED COMPLETELY IN THE TAF OWING TO SOME UNCERTAINTY IN
COVERAGE AND EXACT TIMING, AND KEPT VCTS FOR NOW. FUTURE TAFS CAN
REFINE THIS. MOST ACTIVITY SHOULD BE DONE BY AROUND 06Z, BUT SOME
HI-RES MODELS REDEVELOP SOME WEAKER, ELEVATED TSTMS, SO WILL
CONTINUE VCTS A BIT LONGER AS WINDS BACK TO THE E OR SE IN
RESPONSE TO WAKE LOW. MVFR CIGS ARE POSSIBLE LATE IN THE PERIOD.
CONFIDENCE: MEDIUM.
GID WATCHES/WARNINGS/ADVISORIES
NE...NONE.
KS...NONE.
SHORT TERM...THIES
LONG TERM...THIES
AVIATION...THIES
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