593
FXUS63 KFGF 240900
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
400 AM CDT Fri May 24 2024

.KEY MESSAGES...

- Will keep monitoring impacts of rain from Thursday and
  additional rain today for rises on area rivers.

- Temperatures today in Cando-Langdon areas from model data seem
  hard to believe as HRRR drops them into the mid 30s midday and
  aftn. Kept hourly temps a tad warmer upper 30s and rain in the
  fcst.

- Low temps below 36F possible in northeast ND late
  tonight/early Saturday. Confidence not yet high enough to
  issue any frost headlines.


&&

.DISCUSSION...
Issued at 340 AM CDT Fri May 24 2024

Upper low in northwest South Dakota with surface low east of
Hettinger ND at 08z. The upper low and sfc low will move
northeast today and be just west of Grand Forks at 18z and be
near Pembina ND at 00z. The initial area of rain and
thunderstorms has moved thru most of the the Red River valley
and now into south central Manitoba. Deformation rain band is
from SW Manitoba thru the Turtle Mountains, Minot to Dickinson
area into parts of western SD. Looking to our south another
surge of showers and a few t-storms is moving north-northeast
thru SW Minnesota and far eastern South Dakota. This area of
moisture will spread into the Red River valley and thru NW/WC MN
during the course of the day as rain wraps back around the
system into central ND.

A few things to consider today.

Track of upper low just west of GFK and surface low near GFK
early to mid afternoon will put the mid RRV in a favored spot
for potential low topped thunderstorms, Canadian GEM has about
500 mb MU CAPE into the Grand Forks area early this afternoon,
with GFS and other short term models a bit weaker more like
100-200 j/kg. Unless some sunny breaks occur and allow temps to
warm just east of the upper low early this aftn, unsure if
enough instability will be realized for low topped supercells.
May be more showers, weak t-storms. But with upper level low and
sfc low nearby and potentially a weak cold front swinging north
around the low, some sfc vorticity. This pattern does look like
prev patterns when funnels have occurred. Uncertainity is too
high to message this in social media, but worth mentioning in
this forecast discussion. I would peg the chance for conditions
favorable for funnels to be 40 pct.

Winds on the backside of the system will br near advisory
levels, with strongest mixing south central ND into central SD.
Though a period of potential wind gusts near 45 kts is possible
into SW fcst area 21z-00z period today. Coord with ABR and BIS
and for SE ND will not issue a wind adv at this time since
stronger wind potential is not til late today and the situation
can be evaulated further during the dayshift.

What has me scratching my head the most is model insistence that
temps will drop into the mid 30s in north central ND and parts
of Devils Lake/Langdon areas this aftn with rain mixing or even
changing to snow some models suggest. I have a tough time with
this degree of cooling as there is no source of that cold of an
airmass anywhere close and dew pt/temp differences are already
at 0-1C so not like there is evaporation cooling involved. HRRR
temps would be the coldest. NBM temps used in fcst would have
upper 30s and rain in that area. Something to monitor for sure.
If any place would get wet snow later today it would be higher
terrain of the Turtle Mountains. But also I always recall many
times the Langdon surprise as it cools there more than anywhere
else it seems.

Tonight....how cold will it get. There is no big high moving in
and potential for scattered clouds at least and some wind. NBM
lows showing 31 in Towner county seem too aggressive, so kept
coldest temp at 32 in NW fcst area. Frost tool gives no frost
due to cloud/wind potential. My confidence in lows below 35 in
Devils Lake-Langdon area is about 50 percent and for lows to 32F
about 20 percent. Just not enough confidence yet to issue any
frost advisory for areas with low temps below 36F at this time.
BIS agreed.

Saturday into Monday will feature a broad 500 mb east-west
trough over the area. Some weak embedded short waves with enough
sfc heating in the aftn to generate a few hundred CAPE and a
chance for a few showers each day.

Tues-Wed should see an upper ridge build in temporarily and
temps warm some, before a possible next 500 mb wave moves in
late next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1130 PM CDT Thu May 23 2024

VFR to MVFR conditions prevail outside of showers and
thunderstorms tonight, with IFR CIGs expected during showers and
embedded storms. Ceilings will slowly fall during the remainder
of the overnight period as an upper low traverses the region.
Some guidance brings ceilings as low as 600 feet heading into
Friday morning before a slow improvement takes shape during the
day. Winds are expected to be gusty along a strong pressure
gradient associated with the upper low, with sustained winds of
20 knots and gusts to near 30 knots at times. Shower activity
will remain in the forecast through at least midday Saturday
before slowly moving off to the north and east during the
afternoon and evening.

&&

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

&&

$$

DISCUSSION...Riddle
AVIATION...Lynch