000
FXUS63 KGRR 262051
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
351 PM EST Mon Feb 26 2024

.KEY MESSAGES...

- Threat of Severe Weather Continues Tonight and Tuesday
  evening

- Colder Temperatures, Snow, and Gusty Winds Wednesday

- Dry Stretch and Gradually Warming Thursday into Monday

&&

.DISCUSSION...
Issued at 345 PM EST Mon Feb 26 2024

- Threat of Severe Weather Continues Tonight and Tuesday
  evening

We are still expecting two rounds of thunderstorms both with a
risk of severe weather. The first occurs tonight with the
initial surge of moisture and instability. The threat tonight is
centered in the 1am to 7am time frame and for the most part
will be a hail threat. Tonight`s storms will fire on a 50 knot
low level jet and be working on 1,000-2,000 j/kg of MUCAPE. A
weak shortwave at 500mb is the impetus for convection. Based on
the HREF showing multiple runs now of storms firing overnight
and sweeping east late, we feel this is the likely morphology
with this initial event. The updraft helicity swaths within the
HREF tell the story that enough shear is present (40 knots) for
rotating updrafts centered between 1am-7am or maybe even 8am.
The area of concern will be the southeast CWA from GRR to the
south and east. Given the shear and instability severe hail is
certainly possible with the stronger updrafts.

The second round of storms looks to potentially be the more
impactful. We continue to lean on the HREF for guidance as it us
usually always the best convective guidance we have. It
continues to show a severe threat Tuesday evening from at the
earliest maybe around 600pm in far Southern Lower Michigan to
2am or 3am Wednesday morning before the convection sweeps off to
the east. All severe weather hazards are in play with wind and
hail being the main threats but we cannot rule out an isolated
tornado as well.

As a deep trough swings through the plains another shortwave
aloft will move through our area Tuesday evening. A low will be
working northeast through the area moving from IL to northern
Lake Huron by Wednesday morning. Models have remained steadfast
that this will be a formidable low reaching mid 980s mb depths
by 7am on Wednesday. As such significant moisture levels will be
pulled into far Southern Lower Michigan by February standards.
Surface dew points will reach the mid 50s F and 850mb dew points
will be at similar values. These values are very elevated
obviously for February. That moisture combined with strong wind
fields will set the stage for a round or two of convection
Tuesday evening. MUCAPE values in the HREF reach 2,000 j/kg.
2,000 MUCAPE values is strong almost any time of the year, but
when combined with the wind fields of a deepening February
system the concern level is raised. 40-60 knot low level jet
winds and similar values in the mid levels will provide rotating
storms. 0-6km shear values are strong near 60 knots. A 200 knot
jet core in the Plains will put us in the left exit region of
the jet streak providing strong lift for updrafts.

As for the details of the Tuesday evening threat we expect
storms to break out in the late afternoon to our south and
southwest and sweep northeast through the area during the
evening and overnight. Linear bows and lines will have the
potential to produce wind damage and the strong updrafts will
also be capable of hail to severe levels. HREF updraft helicity
swaths are strong and have values capable of all hazards. In
regard to the tornado threat it will likely come down to where
the warm front is around 6pm-10pm time frame as the low moves
northeast pushing the warm front with it. If storms interact
with that boundary an isolated tornado cannot be ruled out.

Temperatures plunge overnight Tuesday night after the convection
goes east. Precipitation will be switching over to snow as the
temperature plunge commences.

- Colder Temperatures, Snow, and Gusty Winds Wednesday

The upper level trough with the vorticity maximum and surface front
move through Wednesday morning. This will bring plenty of lift along
with a surge of cold air. 925mb temps quickly fall to around -10C
behind the front with a transition to all snow expected early
Wednesday morning. Winds also increase behind the front with
northwest winds gusting around 30 to 40 mph. The combination of
falling temperatures, snow, and gusty winds will likely impact the
Wednesday morning commute. There is some uncertainty in exact
snowfall amounts at this time as seen within the ensembles and
probabilistic fields. Amounts range generally in the 25th to 75th
percentiles of amounts less than an inch to around an inch to 3
inches with the highest amounts along the lakeshore and along and
north of M-20. Dry conditions look to return Wednesday evening with
winds gradually becoming lighter Wednesday night into Thursday.

- Dry Stretch and Gradually Warming Thursday into Monday

Upper level ridging and subsidence move in for Thursday and continue
into the beginning of next week. The only hiccup we`ll have to watch
is a shortwave that moves through Friday that could bring some rain
to the area. Within the ridge temperatures warm once more with highs
starting in the mid to upper 30s Thursday, reaching the mid to upper
50s by Friday, and then 60s once more for Sunday and Monday.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1217 PM EST Mon Feb 26 2024

VFR conditions are expected through this evening. There will be
a period where isolated to scattered showers and thunderstorms
will be possible tonight into Tuesday morning from 6-14Z. There
is a potential for these storms to be strong with hail as the
primary concern.

South to southwest winds will be gusting to 20 to 30 knots
overnight aided by the low level jet causing some low level wind
shear. Ceilings overnight into Tuesday are expected to gradually
lower to low MVFR values and lift back to VFR values by the
afternoon.

&&

.MARINE...
Issued at 345 PM EST Mon Feb 26 2024

We have an ongoing Small Craft Advisory which continues through
300pm on Tuesday. This timing looks good, although it may go an
hour or two longer in length. We will monitor this. Right now
the Muskegon Buoy and Southern Lake Michigan buoy are only
showing 1-2 footers. The strongest winds and therefore largest
waves should be tonight though based on BUKFIT overviews. Winds
in this advisory will be 15-25 knots with waves of 3-5 feet.

The bigger event which may reach gale force will occur Tuesday
overnight through Wednesday midday. At this point not enough
confidence to issue a Gale Watch in the nearshore waters but it
will be close. Models are indicating winds in the 30-35 knot
range which is right on the fence for a Gale Watch/Warning. Very
strong cold air advection occurs with these northwest winds so
waves are going to jump. Waves look to peak Wednesday morning in
the 9 to 13 foot range.

&&

.CLIMATE...
Issued at 312 AM EST Mon Feb 26 2024

Record high maximums and minimums are possible Tuesday.

GRR      LAN      MKG      AZO
High Maximum   67-1976  64-1867  62-1976  67-1976
High Minimum   37-3128  38-3128  35-1999  43-1987

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 3 PM EST Tuesday for LMZ844>849.

&&

$$

DISCUSSION...DUKE/RAH
AVIATION...RAH
MARINE...DUKE
CLIMATE...04

NWS GRR Office Area Forecast Discussion