Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/12/20
Area Forecast Discussion
National Weather Service Caribou ME
913 PM EDT Mon May 11 2020
A low pressure system will cross the Downeast region overnight
and exit across the Maritimes through Tuesday. High pressure
will build toward the region Wednesday through Thursday. Low
pressure will approach on Friday then move east Saturday.
.NEAR TERM /THROUGH TUESDAY/...
9:13 pm update: Low pres is visible on satellite pictures along
the southern Maine/NH border. The low is expected to track
along or very near the Downeast coast overnight and should be in
the vicinity of Eastport by 12Z Tue morning. Precipitation will
continue to overspread the FA late this evening, and as colder
air presses into northwest Maine the rain will change to snow,
The progression from rain to snow will push east across far
northern Maine after midnight. No significant changes are
planned at this time.
As the low lifts up across the state this evening, it should
tend to track along a frontal boundary. The NAM and RAP show
this taking the low further to the south along the coast. The
last 2 runs of the HRRR match closer to the GFS which track just
a bit further n which would allow for warmer to hold in longer.
So, the timing of the changeover to snow and how much snow
accumulates are the challenges for this forecast.
The 12Z UA showed the upper trof sharpening up as a jet core
and colder air dives down the back side of the trof. This will
lead to the trof going negative tilt tonight and eventually
closing off southern ME and then lifting ene overnight. Given
the placement of the upper low moving across eastern ME,
thinking is that the sfc low will be tracking closer to the
coast. Therefore, following blend of the NAM/RAP and HRRR,
decided on tracking the low closer to the coast, and leaning a
bit colder, which means a bit more snow across the northern
areas. There appears to be a sharp cutoff as one moves eastward.
Decision was to bring northern Piscataquis County into the
Winter Weather Advisory w/the potential for 3-6 inches of snow.
Across northeast Aroostook County, a couple of inches expected
due to the sharp cutoff. Precip will start off in the form of
rain this evening and then gradually mix and change over to snow
across the nwrn areas as temps drop off quickly into the upper
20s and lower 30s overnight. Further to the east, the rain will
hang in a bit longer given temps holding in the upper 30s and
lower 40s. Further s, precip will be all rain and there could
be a period of heavy rainfall as the strong jet core from
850-700mbs lifts to the ne. Total rainfall/QPF is expected to be
about 0.50 to 0.75 inches. Some areas along the Downeast and
coast could see close to an inch of rainfall from this event. No
flooding issues are expected w/this latest event. Some ponding
of water on roads can be expected.
The low will lift quickly into New Brunswick on Tuesday w/the snow
and rain tapering off to a showery activity as the winds come
around to the NNW behind the exiting low. The upper level trof
will be hanging back w/some llvl convergence noted along the
northern and eastern Maine border. Daytime temps will be some
10-20 degrees colder,especially across the northern areas. Given
the cold temps(below 0C right down to 1000 ft, there is the
potential for some leftover snow showers across the higher
terrain during the day.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Moisture lingering on the back side of the departing low over
eastern Canada and a second weak shortwave trough swinging
through will lead to some flurries and a slight chance of a snow
shower across eastern Aroostook County early Tuesday night.
There is a chance of a frost or freeze where the growing season
has begun across Downeast areas, particularly those sheltered
from the wind. However, will hold off on any headlines at the
moment due to active winter weather headlines and some
uncertainty if coverage of below freezing temperatures will
suffice for freeze headlines. Wednesday through Thursday will be
a transition period as the deep trough departs and an upper
level ridge approaches. Rising heights will correspond with
rising low and high temperatures. Expect plenty of sunshine with
dry air aloft and just some diurnally forced cumulus. Both
Wednesday and Thursday will be breezy, with gusts up to around
25 to 35 mph suggested by momentum transfer as mixing heights
reach well above 850mb.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The next significant storm system will approach Thursday night,
bringing rain to the forecast area. Initially temperatures will
drop overnight with the ridge axis moving overhead leading to
light winds and mostly clear skies. Later overnight, increasing
clouds will cause temperatures to steady or moderate with a
chance of virga or showers as a warm front approaches. Patchy
freezing drizzle is possible across northern sheltered
locations, but confidence was not sufficient for inclusion in
the grids at this point. Rain and showers continue through
Friday night as the low occludes over Maine. Saturday will be
mainly dry and feature near normal temperatures, with just a
stray convective shower possible. Upper level ridging will crest
over the area Sunday morning, with model solutions diverging
more significantly after that. In general, the unsettled May
pattern will continue with multiple chances for showers and near
to below normal temperatures through early next week.
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: VFR this evening for all terminals from BGR north,
but conditions will deteriorate to MVFR and IFR for all
terminals by later tonight. Even LIFR conditions can be
expected. The northern terminals, especially n of KHUL will be
seeing some accumulating snow into Tuesday morning. Improvement
to MVFR is expected by late morning for KBGR and KBHB. It will
take a while longer for the northern terminals. SSW winds will
become ENE overnight at 10 knots and shift to the NNW on
Tuesday behind the departing low and will become strong and
gusty with gusts to 25 to 30 knots.
Tuesday night to Thursday night: VFR. NW winds gusting to
around 30 knots during the day.
Friday to Friday night: MVFR with periods of rain and rain
showers. SSE winds becoming NNW late Friday night.
Saturday: VFR south and MVFR north with modestly breezy NW
NEAR TERM: No headlines are expected attm, although SSW winds
are going to pick up overnight ahead of the apchg low. Decided
attm to keep winds below 25 kts. Highest gusts will be across
the outer zones. Seas will gradually build overnight to 4-5 ft.
Winds will swing around to the NW on Tue w/sustained speeds of
15-20 kts. Some gusts to 25 kts are expected as colder air hits
the waters. Decided to keep the gusts just below 25 kt, but the
midnight crew will need to monitor the winds as the outer zones
could see gusts hitting 25 kts for >2 hrs during the afternoon.
SHORT TERM: NW winds behind a cold front will likely gust to
small craft Tuesday night into Wednesday with wave heights
around 3 to 4 feet over the outer waters. Winds diminish
slightly to just below small craft Wednesday night through
Friday morning. A long period swell will approach Friday night
into Saturday with potential for small craft wave heights.
ME...Winter Weather Advisory from 2 AM to 10 AM EDT Tuesday for
Winter Weather Advisory until 9 AM EDT Tuesday for MEZ001-003-
Area Forecast Discussion
National Weather Service Green Bay WI
1044 PM CDT Mon May 11 2020
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Tuesday
Issued at 252 PM CDT Mon May 11 2020
The latest RAP analysis and satellite/radar imagery show the state
of Wisconsin positioned between low pressure over New England and
high pressure over the Plains into central Canada. A reinforcing
cold front combined with flow off Lake Superior and steep low
level lapse rates have contributed to the formation of convective
cloudiness with the heat of the day. Clouds have been more
widespread of central to northeast WI so far today. Meanwhile,
plenty of clear skies upstream over the northern Plains and into
Canada. As the large high pressure system moves towards the
western Great Lakes, low temperatures and frost/freeze headlines
are the main forecast concerns.
Tonight...The surface high will slide southeast into the northern
Mississippi Valley by late tonight. Conditions will be more
favorable for radiational cooling unlike last night where clouds
and a modest wind persisted. Should see clear skies once the
convective clouds dissipate early this evening. Have some concern
that winds may not completely decouple over northeast WI where air
remains coming off Lake Superior. Statistical guidance insists on
winds becoming calm over central and north-central WI, which will
be favorable for a hard freeze/frost. Regardless, temps again are
expected to fall to or below freezing at all locations according
to the top performing guidance, so will issue another freeze
Tuesday...After a frosty start, high pressure and a dry airmass
will lead to sunny skies. Low level temps moderate some, so should
see highs a few degrees warmer than today, and range from the
upper 40s to middle 50s.
.LONG TERM...Tuesday Night Through Monday
Issued at 252 PM CDT Mon May 11 2020
Potential frost/freeze headlines Tuesday night, elevated fire
weather conditions over northern WI on Wednesday, precipitation
trends, and warming temperatures will be the concerns for the
Have lowered the model blended temperatures Tuesday night, as
models have slowed down the arrival of cloud cover, and winds will
be light. Would expect that we will need another round of frost
or freeze headlines, though the coldest temperatures will occur
over northern WI, where frost/freeze headlines do not start until
Stayed close to the previous forecast for Wednesday, with
scattered showers only making it into the western half of the
forecast area during the afternoon. Daytime mixing ahead of the
the precipitation should allow relative humidity to drop to near
critical levels in far northern WI again. Highs should reach the
upper 50s and lower 60s away from Lake Michigan. Southeast winds
will gust to 20 to 25 mph by afternoon.
Strong return flow is expected to develop Wednesday night, as the
surface high shifts into the eastern Great Lakes and a 40 knot
low-level jet develops. This will bring a swath of showers
through the forecast area. The showers should diminish somewhat
overnight as the low-level jet weakens and veers west.
Models offer differing solutions with precipitation trends on
Thursday. The GFS brings a stronger surface low through the
region, and generates significant QPF over most of the region
Thursday afternoon. The ECMWF is weaker, with only light showers
during the morning. Due to the uncertainty, we stayed close to
the blended model pops during this period. Milder temperatures in
the 60s are anticipated, though if the GFS verifies, widespread
showers would likely hold temperatures back several degrees.
Late Thursday night through Friday night looks like a dry period,
as high pressure moves through the region. With abundant sunshine,
highs on Friday should approach 70 degrees in the typical warm
It appears there will be a period of showers over the weekend, but
timing is very questionable. The GFS brings precipitation through
the region Saturday afternoon and evening, while the ECMWF is
much slower; late Saturday night into Sunday morning. Once again,
will stay with the model blend until this gets sorted out.
Dry and warmer conditions are expected to start the next work
week, with highs reaching the lower to middle 70s on Monday.
.AVIATION...for 06Z TAF Issuance
Issued at 1044 PM CDT Mon May 11 2020
VFR conditions and good flying conditions can be expected through
this TAF issuance. Winds are expected to remain light. Otherwise,
eastern TAF sites will likely end up seeing a wind shift Tuesday
afternoon as the lake breeze shifts inland late Tuesday afternoon.
Winds will calm down early in the evening.
Issued at 252 PM CDT Mon May 11 2020
Elevated fire weather conditions will continue on Tuesday, with
relative humidities dropping into the 15 to 25 percent range in
the sandy soil regions. The threat should shift to northern WI on
Wednesday, where humidities should drop to around 25 percent, and
southeast winds will be on the increase.
Freeze Warning until 8 AM CDT Tuesday for WIZ020-022-030-031-
Area Forecast Discussion
National Weather Service Pocatello ID
132 PM MDT Mon May 11 2020
.SHORT TERM...Tonight through Wednesday night.
A low pressure system off the Pacific Northwest coast will send
moisture through central and eastern Idaho through midweek. Showers
and thunderstorms will be possible mainly during the afternoon and
evening and especially across the high country. Overnight showers is
possible during the short term as well. Gusty winds and small hail
are possible, mainly this afternoon into the evening because we have
the most heating and instability this afternoon. Cooler temperatures
and more stability arrive Tuesday and Wednesday. The best chance for
showers in the short term is Wednesday when the low sends a stronger
push of moisture into the region. Breezy conditions will accompany
the cooler temperatures for Tuesday and Wednesday with lake wind
advisories possible for the American Falls Reservoir both days.
.LONG TERM...Thu through next Mon night. The coast low starts its
onshore movement and actually comes through Thu night Fri, which
allows one dry day and evening this week, on Sat. By Sat night,
another low drops into nearly the same location as the current upper
level low, producing another period of showers and thunderstorms.
Right now, it appears as though this closed upper level low may move
faster than the current one, but computer models are notoriously bad
at predicting closed lows in the spring and fall, so don`t bank on
anything quite yet. Messick
.AVIATION...Moisture and instability being pumped in from the
southwest by a coastal low. Expect TSRA at least in the vicinity of
the airdromes. Using the HRRR spread over several runs, have put in
tempo groups when there is some definite time periods. There is a
trough that is pushing things from west to east as well as a
clearing line that starts showing up around 12/00Z at KSUN and
spreads southward and eastward, getting last to KDIJ. KDIJ, KPIH,
and KBYI appear most open to TSRA actually on station. A mid-level
CIG develops late tonight and moves through during the morning hours
Tue. This appears to delay the onset of convection by a few hours,
with most shower activity for Tuesday not actually occurring
until 13/00Z. Messick
Area Forecast Discussion
National Weather Service Shreveport LA
1014 PM CDT Mon May 11 2020
A quiet night going for us here in the four state area with lots
of cirrus overhead from distant thunderstorms in W TX. The HRRR is
still liking some light QPF working into SE OK by 09-12Z and then
more so into the I-30 corridor during the new day. This is well
covered with our afternoon package. The current forecast lows are
a healthy range of 50s with lower in the East and warmer West
with a SE component to the return flow. These numbers are hard to
argue with being right in the neighborhood with guidance numbers.
No changes needed to the forecast at this time. /24/
.PREV DISCUSSION... /issued 645 PM CDT Mon May 11 2020/
For the ArkLaTex terminals VFR is expected to continue at least
for another full cycle, but showers could change that into
midweek. Meanwhile, our winds are E/SE this afternoon and may back
to E 5-10KT overnight, before veering back to S/SE 5-15KT with
some higher gusts for Tuesday. Cigs will lower, but should keep
VFR until we get some precip in the area toward Wednesday. /24/
PREV DISCUSSION... /issued 242 PM CDT Mon May 11 2020/
SHORT TERM.../Tonight through Tuesday night/
Look for temperatures tonight to once again be below average, as
surface ridging with light east winds will allow temperatures to
remain low behind the now passed cold front. Surface ridging
begins to break down during the overnight hours, and a weak
shortwave is expected to move through the area during the day
tomorrow. Look for a rather sharp temperature gradient tomorrow,
as the cold-front retrogrades north in the form of a warm-front.
Temperatures in our northern zones will be in the low 70s, with
temperatures in our southern zones reaching the low 80s.
Showers and thunderstorm will develop and expand into the
afternoon hours on Tuesday, as that weak upper level disturbance
fires convection along the warm front in Southeast OK and
Southwest AR. While most of the activity tomorrow will be general
thunder, a severe thunderstorm or two can`t be completely ruled
out. Modest deep-layer shear is present over the area, and CAPE
values into the afternoon may reach 1500 J/Kg in our E. Texas
counties. This would be the area most likely to see any severe
weather, in the event a storm were to become severe. Damaging
winds and large hail would be the primary threat with these
LONG TERM.../Wednesday through Sunday Night/
Disturbed zonal flow pattern and warm/moist airmass in place
Wednesday will continue to keep chances for sct convection in the
fcst through Friday. Despite cloud cover/convection, temps look to
run several degrees above seasonal normals.
Late Friday into Saturday, a piece of energy in the generally weak
zonal flow will become cut off and drift ewd across TX. More
widespread coverage of convection is expected as the upper low moves
across our region through Sunday night, tapping abundant moisture
from the Gulf of Mexico. The slow-moving nature of this system will
bear watching over the next few days, as it may have the potential
to bring heavy rainfall/flooding. /12/
.PRELIMINARY POINT TEMPS/POPS...
SHV 56 81 64 84 / 0 10 20 20
MLU 52 81 63 84 / 0 10 10 10
DEQ 51 71 59 80 / 20 60 30 20
TXK 52 75 62 80 / 0 40 30 20
ELD 51 78 61 81 / 10 20 10 20
TYR 58 79 65 84 / 10 40 20 20
GGG 57 81 64 84 / 0 30 20 20
LFK 59 83 65 87 / 0 20 10 20
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Tuesday)
Issued at 359 PM CDT Mon May 11 2020
A weak mid-level perturbation along with isentropic lift has
contributed to widespread cloud cover across the state today, with
showers mainly across central and southeast KS. Radar has been
detecting light and spotty showers throughout the CWA, but much of
this has struggled to reach the ground thus far due to the dry air
mass associated with the surface ridge. Generally speaking, models
continue to slowly bring showers from south to north this evening
and lasting through Tuesday morning before exiting to the east by
the afternoon. This is consistent with forecast soundings remaining
dry the rest of the afternoon before saturating in the low levels by
the early evening at Emporia, then mid to late evening toward
Topeka. Areas in far northeast KS will likely see very little
rainfall or may stay entirely dry, as soundings for the Marysville
area struggle to saturate and if they do, it is only for a brief
period during the overnight hours. Lift associated with this wave
should move out of the area by Tuesday afternoon with a short break
before the next possible precipitation chance.
Aside from on and off rain showers, temperatures will fall back to
near 40 degrees across the CWA by morning. Some WAA, although weak,
will allow temperatures to become slightly warmer than today in the
50s tomorrow afternoon. With less rainfall compared to the rest of
the area, northeast KS is expected to reach the upper 50s while
other parts of the CWA will likely stay in the low to mid 50s.
.LONG TERM...(Tuesday night through Monday)
Issued at 359 PM CDT Mon May 11 2020
Late Tuesday night into Wednesday morning, WAA increases as well as
low-level winds, which looks to bring another round of showers and
possibly some elevated thunderstorms. With a strong low-level
inversion in place, any convection that occurs would be elevated
above 850 mb, but MUCAPE between 500-1000 J/kg could result in
morning storms mainly south of I-70. However, if enough
destabilization occurs in the afternoon after this moves out,
there could be potential for severe thunderstorms Wednesday
afternoon and evening ahead of a deepening low in the Rockies with
an approaching dryline in central KS. Any surface-based storms
would be hard to come by with a strong cap in place, but large
hail and damaging wind are possible given 35-40 kts of bulk shear.
A frontal boundary will move across the CWA Thursday, bringing
another chance of thunderstorms with another possibility of severe
weather as a sharp instability gradient forms along the boundary.
This boundary moves south of the area Thursday night, but looks to
move back north on Friday and hovers around the area through the
weekend. This along with disturbances within the flow will continue
to bring chances of showers and thunderstorms the rest of the week,
which could result in heavy rainfall, particularly in east central
KS south of I-70.
By Sunday night into Monday, a high-amplitude ridge will keep
conditions dry and give us a break from the rainfall. High
temperatures will be in the 70s and 80s through much of the area for
the extended period.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 633 PM CDT Mon May 11 2020
VFR cigs at KTOP/KFOE/KMHK will gradually lower within the next
few hours as light showers continue to spread east, eroding the
dry layer below 7 kft. This leads to some uncertainty in cloud
bases overnight with most models not handling the dry layer and
therefore bringing IFR stratus in quicker. KMHK would be most
probable to see IFR, however confidence is overall not high enough
to mention based on latest trends and observations. For now,
sided closer to the HRRR model with MVFR stratus overnight as
showers gradually diminish. With increased low level moisture
advection tomorrow, MVFR stratus persists through the afternoon.