591
FXUS63 KFGF 100002
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
702 PM CDT Tue Jul 9 2024

.KEY MESSAGES...

- Isolated thunderstorms across the region through the evening.
  Severe storms are not expected.

- Risk for heat related impacts Friday through Sunday.

&&

.UPDATE...
Issued at 702 PM CDT Tue Jul 9 2024

Isolated showers and thunderstorms continue to form primarily
from the Red River Valley and points west. Most activity thus
far has been brief, with observations of heavy rain and gusty
winds approaching 50 mph. Look for this to diminish gradually
through the remainder of the evening as temperatures fall below
convective temps and cause low level lapse rates to fall.


&&

.DISCUSSION...
Issued at 256 PM CDT Tue Jul 9 2024

...Synopsis...

Ensemble guidance in decent agreement with evolution of the
larger scale pattern through the next week - depicting a
building western CONUS ridge with the main storm track across
Canada. The main uncertainty exists with the speed and track of
individual upper waves and how they will affect the ridging.
After surface ridging Wednesday into Thursday, there will be
periods of instability and forcing leading to thunderstorms, but
not sure how far south and/or severe risk (especially strength
of deep layer bulk shear). CWASP and CSU machine learning both
indicate periods of marginal severe risk this weekend into next
week.

...Isolated thunderstorms this evening...

Water vapor imagery indicates an upper wave approaching the
region from the north, with the cu field building across the
region. Radar imagery indicates showers/thunderstorms
developing. Deep layer shear is weak, so most storms will
effectively kill themselves. However, given steep lapse rates in
a decently mixed boundary layer, wouldn`t be surprised to see
stronger storms produce gusts 40-50 mph. Additionally, stronger
storms may produce brief heavy downpours resulting in local
amounts around 1 inch and minor flood impacts in more
susceptible spots.

...Risk for heat related impacts this weekend...

As the upper ridge builds across the western CONUS and gradually
shifts east a much warmer and moist airmass propagates across
the region, especially Friday through Sunday. NBM MaxT 25-75
percentiles range from ~90F to ~98F during this period (across
the southern CWA at least), and with crops nearing peak
Evapotranspiration Td each day should be ~70F. Heat index values
would be >100F if the temperatures were able to reach upper 90s,
but that is still a low probability outcome. At this point most
likely (80% chance) heat index values each afternoon will be in
the mid to upper 90s, which is below advisory criteria. However,
the new NWS heat risk product (which accounts for duration of
heat including both daytime and nighttime temperatures as well
as if those temperatures pose an elevated risk of heat related
impacts based on data from the CDC) indicates a moderate risk
of heat related impacts Friday into Saturday with a major risk
of heat related impacts on Sunday.

www.wpc.ncep.noaa.gov/heatrisk

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 633 PM CDT Tue Jul 9 2024

VFR conditions prevail through the period at all TAF sites.
Isolated showers and thunderstorms remain possible through
around 03Z, which could include brief gusty winds. Otherwise,
winds remain light and variable through Wednesday morning, then
increase slightly, but generally remain less than 10 knots
heading into the midday hours.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.

&&

$$

UPDATE...Lynch
DISCUSSION...TG
AVIATION...Lynch