611
FXUS63 KFGF 020832
AFDFGF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
332 AM CDT FRI JUN 2 2023
SHORT TERM
(TODAY THROUGH SATURDAY)
ISSUED AT 140 AM CDT FRI JUN 2 2023
KEY MESSAGES...
- SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP ONCE AGAIN
THIS AFTERNOON. THE PROBABILITY FOR BOTH SEVERE WEATHER AND
FLASH FLOODING IS LOW BUT NON-ZERO.
- HOT TEMPERATURES WILL CONTINUE WITH HIGH TEMPERATURES IN THE 90S
TODAY AND SATURDAY.
DISCUSSION....
SURFACE ANALYSIS ACROSS THE NORTHERN PLAINS INDICATE NO REAL
PROMINENT SURFACE FEATURES WITHIN THE VICINITY OF OUR CWA AT THIS
TIME EXCEPT FOR SOME SUBTLE PRESSURE TROUGHS ACROSS NORTHEASTERN
SOUTH DAKOTA, PRIMARILY ATTACHED TO THE SURFACE LOW OVER IN
EASTERN WYOMING. LARGE SCALE RIDGING CONTINUES TO RETROGRADE
TOWARDS OUR AREA FROM THE EAST PER WATER VAPOR SATELLITE.
PERSISTENCE CONTINUES TO BE THE PRIMARY DRIVING FORCE FOR TODAYS
FORECAST. HIGH TEMPERATURES THIS AFTERNOON SHOULD BE A FEW DEGREES
COOLER THAN TODAY THANKS TO 2 C LOWER 850MB TEMPERATURES AND VERY
LOW CONVECTIVE TEMPERATURES. REGARDLESS OF COOLER TEMPERATURES,
EXPECT AT LEAST 88 TODAY, WITH THE RED RIVER VALLEY EXCEEDING 90.
SCATTERED SHOWERS AND THUNDERSTORMS WILL OCCUR ONCE AGAIN THIS
AFTERNOON THANKS TO LOW CONVECTIVE TEMPERATURES AND STRONG
BOUNDARY LAYER HEATING. THE STRONGEST SHOWERS AND THUNDERSTORMS
WILL HAVE THE POTENTIAL TO PRODUCE ISOLATED SEVERE STORMS AND
ISOLATED FLASH FLOODING.
FOR THE SEVERE THREAT, MLCAPE VALUES HAVE TENDED TO APPROACH
1500-2500 J/KG THROUGH THE LAST FEW DAYS. WITH A SIMILAR AIRMASS OVER
US, THAT APPEARS TO BE THE MOST LIKELY SOLUTION ONCE AGAIN DESPITE
SOME CAMS CONTINUING TO UNDERESTIMATE MLCAPE. MID-LEVEL LAPSE
RATES CONTINUE TO BE MOSTLY CONDITIONALLY UNSTABLE TO NEAR STABLE, SO
MOST OF THE INSTABILITY WILL COME FROM WITHIN THE MIXED LAYER.
COMBINE THAT WITH VERY WEAK FLOW ALOFT, RESIDENCE TIME WITHIN THE
HAIL GROWTH ZONE MAY BE EXTENDED JUST ENOUGH TO PRODUCE UP TO
QUARTER SIZE HAIL. WITH THE LACK OF EFFECTIVE BULK SHEAR TO REALLY
DEVELOP ANY MEANINGFUL MESOCYCLONES (OUTSIDE A RANDOM OUTFLOW
BOUNDARY DEVELOPING PRODUCING A STORM SCALE ENVIRONMENT FOR
SUPERCELLS), THE STRONGEST SEVERE STORMS COULD PRODUCE UP TO
QUARTER SIZE HAIL, AND THIS WOULD BE A VERY ISOLATED THREAT.
ADDITIONALLY, WITH THE DEEP VERTICAL MIXING AND THE HIGH
PRECIPITABLE WATER VALUES, DOWNBURST WINDS APPEAR POSSIBLE DUE TO
ENHANCED WATER LOADING DESPITE DCAPE VALUES GENERALLY BEING IN THE
700-1100 RANGE. WHILE NOT A SLAM DUNK BY ANY MEANS, THERE IS THAT
POTENTIAL ONCE AGAIN.
AS STATED ABOVE, FLASH FLOODING MAY CONTINUE TO POSE A RISK TODAY.
HIGH PW VALUES APPROACHING THE 95TH PERCENTILE AND HIGHER WILL
CONTINUE TO LINGER ACROSS THE AREA THANKS TO CONTINUED SOUTHERLY
FLOW. EFFICIENT RAINFALL RATES ARE LIKELY TO CONTINUE, WITH RATES
POTENTIALLY EXCEEDING AN INCH PER HOUR AT TIMES, ALTHOUGH THE
RESIDENCE TIME AT ANY PARTICULAR POINT IS VERY UNCERTAIN AND HAS A
VERY LOW PROBABILITY FOR STICKING AROUND LONG ENOUGH AT ANY ONE
SITE TO PRODUCE SIGNIFICANT RAINFALL ACCUMULATIONS. REGARDLESS,
HEAVY RAINFALL RATES MAY POSE ISOLATED FLASH FLOODING RISK AS
MOTION OF THESE STORMS WILL BE FAIRLY MINIMAL AND RESIDENCE TIME
WILL GENERALLY BE AT THE MERCY OF THE ORDINARY THUNDERSTORM LIFE
CYCLE.
FOR SATURDAY, EXPECT MORE OF THE SAME, WITH HIGH TEMPERATURES
APPROACHING THE 90S AND SCATTERED SHOWERS AND THUNDERSTORMS. AS
THE RIDGE CONTINUES TO PUSH SLOWLY WESTWARD, THE SPATIAL EXTENT OF
SHOWERS AND STORMS MAY BECOME LESS AND LESS, ALTHOUGH CONFIDENCE
IS TOO LOW TO SAY THAT WITH ANY CERTAINTY. FOR NOW JUST EXPECT
CONTINUED CHANCES FOR SHOWERS AND STORMS WITH ISOLATED STRONG TO
SEVERE STORMS POSSIBLE.
LONG TERM
(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 140 AM CDT FRI JUN 2 2023
-ABOVE AVERAGE TEMPERATURES CONTINUE SUNDAY INTO MONDAY, WITH A
PATTERN SHIFT THAT MAY ALLOW FOR TEMPERATURES TO BE MORE IN LINE
WITH SEASONAL RANGES.
-THERE CONTINUES TO BE CONDITIONAL RISK FOR ISOLATED STRONG TO
SEVERE THUNDERSTORMS DURING THE AFTERNOON AND EVENING PERIODS SUNDAY
INTO MONDAY. UNSETTLED PATTERN CONTINUES THROUGH THE END OF NEXT
WEEK, HOWEVER THE PROBABILITY FOR SEVERE IS LOWER.
LARGE SCALE RIDGE IS STILL SHOWN TO BE IN PLACE OVER OUR CWA SUNDAY
INTO MONDAY BEFORE FINALLY SHIFTING WEST WHILE TROUGHING DEEPENS
OVER HUDSON BAY. DUE TO THE INFLUENCE OF THE RIDGE WE SEE SIMILAR
CONDITIONS AND CONCERNS AS THE PREVIOUS DAYS WILL WELL ABOVE AVERAGE
TEMPERATURES AROUND 90, AND DIURNALLY FOCUSED THUNDERSTORM ACTIVITY
(PRIMARILY DRIVEN BY CONVECTIVE TEMPS, MODEST INSTABILTY AND WEAK
SURFACE CONVERGENCE). THE PREDICTABILITY OF ACTUAL COVERAGE/IMPACTS
IS LOW DUE TO THE LACK OF SYNOPTIC/ORGANIZED FORCING, BUT AS WITH
PREVIOUS DAYS WE SHOULD HAVE DAILY AFTERNOON/EVENING RISKS FOR A FEW
STRONG OR SEVERE STORMS (ML CAPE STILL IN THE 1500-2500 J/KG WITH
LOW SHEAR). HAIL AROUND 1 INCH, LIMITED MICROBURST POTENTIAL (GUSTS
AROUND 60 MPH), AND LOCALIZED HEAVY/EXCESSIVE RAIN RISK (DUE TO HIGH
PWATS).
AS THE RIDGE TRANSITIONS WEST TUESDAY INTO THE LATER PART OF NEXT
WEEK, THE INFLUENCE WANES AND WE SEE NORTHERLY FLOW START TO BUILD
BACK INTO OUR CWA, WITH CLUSTERS SHOWING SOME SEPARATION IN THE
DEPTH OF MID LEVEL TROUGHING TO THE NORTHEAST THAT WOULD INFLUENCE
THE DEGREE OF CAA AND FORCING DUE TO ANY PROGRESSIVE MID LEVEL
SHORTWAVES WITHIN THE NORTHERLY FLOW. THIS CREATES LARGER UNCERTAINTY
ON TEMPERATURES, BUT ALSO ON IMPACTS/COVERAGE OF STORMS. THESE
PROGRESSIVE FEATURES ALLOW FOR MORE ORGANIZED FORCING "WHEN" THE
PASS, BUT THERE IS LARGER SPREAD ON DETAILS. THIS LARGE SCALE
PATTERN WILL ALSO TEND TO TRANSLATE TO THE BL WITH DRIER FLOW ACROSS
MUCH OF OUR CWA LOWERING POTENTIAL INSTABILTY OR AT LEAST CREATING A
LARGE GRADIENT WEST TO EAST (HIGHER INSTABILTY/PWATS WEST TO LOWER
IN THE EAST).
IF THAT MOIST/UNSTABLE AIR MASS REMAIN OVER PARTS OF OUR CWA WHEN
THOSE SHORTWAVES ARRIVE THERE MAY BE ORGANIZED PERIODS OF SEVERE
(NOT CURRENTLY SHOWN BY MACHINE LEARNING/ANALOGUES). IF THAT AXIS IS
WEST THEN WE WOULD ONLY BE LOOKING AT PERIODS OF SHOWERS AND NON
SEVERE STORMS WHEN THEY PASS.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1133 PM CDT THU JUN 1 2023
VFR CONDITIONS NOW AND THROUGHOUT THE PERIOD AS CONVECTION
DISSIPATES. HIGH CLOUDS THROUGH MOST OF THE OVERNIGHT AND INTO
TOMORROW. WINDS WILL BE MOSTLY FROM THE SOUTHEAST IN THE 5 TO 12
KT RANGE.
FGF WATCHES/WARNINGS/ADVISORIES
ND...NONE.
MN...NONE.
SHORT TERM...PERROUX
LONG TERM...DJR
AVIATION...JR
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