Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/05/20
Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
558 PM CDT Mon May 4 2020
Northeast winds at 20 to 25 knots with higher gusts will be
common until a couple of hours after midnight when winds will come
down to 10 knots or less. Winds will turn to the southeast and
south at DHT and GUY toward the end of this forecast. Skies are
expected to remain VFR.
.PREV DISCUSSION... /Issued 335 PM CDT Mon May 4 2020/
SHORT TERM...Tonight through Tuesday Night...
In the zonal flow aloft, a shortwave is progged to come through
the Panhandles tonight. While this can provide some uplift, models
are mostly dry except for the HRRR. Model soundings show very dry
air through the column and when moisture is present, there is
an inverted V. So for now have left out pops as thinking if the
one shower in the far northwest of Cimarron County does develop
like the HRRR suggests, it`s likely to just be virga and bring
gusty winds. Otherwise for tonight, the surface low has already
moved off to our east and the pressure gradient looks to tighten
up this evening, causing winds to increase through midnight. After
midnight the pressure gradient relaxes and winds ease as surface
high pressure settles in. With the northerly flow in place,
tomorrow will finally see cooler temps that will be more spring
like. As the high pressure slides eastward, winds return to
southerly flow which will help maintain overnight lows in the 40s.
LONG TERM...Wednesday through Sunday Night...
Weak high pressure south of the Four Corners area will provide
warm temperatures and northwest flow to the Panhandles. Wednesday
looks to be a dry day with highs in the upper 70s to mid 80s.
Models hint at increased 850-700mb moisture advection Wednesday
night into Thursday morning. That increase in low level moisture,
in conjunction with a shortwave under the northwest flow will aid
in possible lift to get some nocturnal storms overnight Wednesday
night into Thursday morning. That being said possible dryline
setup across the Panhandles in the afternoon, with the eastern
Panhandles in play for strong to severe storms. Areas east of the
dryline have plenty of CAPE/Shear/Helicity to work with to have
all hazards in play. However, not all models agree with this
solution, as some suggest the surface low will be further south
allowing for winds to be more out of the northeast. This will
likely shut down the severe weather threat, although there might
be a small chance with the incoming cold front Thursday night into
Cold front will bring temperatures back down into the 60s to lower
70s on Friday. Main upper level trof associated with this front
will be centered over the Great Lakes region. As this amplifies
over the eastern CONUS, high pressure will strengthen over the
western CONUS. This will bring increased northwest flow and warm
temperatures to the Panhandles through the weekend. Possible
northwest flow thunderstorm setup over the weekend. Will note that
a slight shift of the ridge to the east or west will play a
significant role on the highs being warmer or cooler, as the
Panhandles currently sits right between the two air masses.
Elevated Fire Weather across the extreme southern Panhandle,
mainly south of I-40 for the rest of the day. Cold front wind
shift out of the northeast expected this evening. Some areas might
see brief elevated conditions due to the increased winds, however
the relative humidity should recover quickly behind the front.
18Z Issuance...All sites look to remain VFR through the period.
Northerly winds will remain through the next 24 hours. Expecting
gusts of 20-30kts during the afternoon hours then increasing to
30-40kts from 02Z to around 08Z. Winds should die off after that
to AOB 15kts.
Area Forecast Discussion
National Weather Service Caribou ME
1206 AM EDT Tue May 5 2020
Low pressure will slowly exit into the Maritimes through
Tuesday. High pressure builds into the area Wednesday into
Thursday. Areas of low pressure will cross the region Friday
.NEAR TERM /THROUGH TUESDAY/...
1210 AM Update: Snow is falling across the St. John Valley down
into NE Aroostook County as temps fall into the lower 30s. The
latest HRRR was doing per the radar trends and obs. Precip
pinwheeling around the upper low and will continue overnight
across the northern and eastern areas. Kept precip chances high
across these areas given that the best convergence and forcing
situated across these areas. Could see a coating of snow w/up to
1/2 of an inch of snow in the higher terrain overnight, mainly
in grassy areas. Hrly temps/dewpoints were adjusted matching the
latest obs. Loaded in the ADJLAV through the overnight period
as this guidance was matching up closely to reality.
Cold upper level low will continue to pivot over the region
overnight. The added lift and forcing has produced some showers
and isolated thunder this afternoon. There was also a report of
pea sized hail near Oxbow, ME with one cell with a trace
Expect forcing and cold air aloft to move south and produce
isolated thunder potential as surface temps remain warm near 60F
amid breaks in the cloud cover Downeast. The environment will
stabilize this evening, with a few scattered showers overnight.
Across the north, temperatures have remained a bit cooler as
cloud cover has remained in place today. Temperatures will fall
to around freezing tonight, especially across higher elevations,
resulting in some snow showers. A dusting can`t be ruled out in
locations that cool the quickest and transition earlier.
Upper low will slowly begin to exit through Tuesday. Some
residual moisture will be in the region, and the chance for
showers again increases Tuesday afternoon.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Upr lvl low wl be ejecting twd the Maritimes Tue night with cyclonic
flow continuing acrs the northern areas Tue evening. Showers wl
diminish drg the late evng hours as upr lvl ridge begins to build in
fm the west. Slight gradient wl allow winds to rmn up drg the
overnight hours with a fairly nice day on tap for Wednesday. Upr lvl
ridging wl dominate the region drg the day with some high clouds
drifting thru the area at times. Max temps wl be just blo normal
acrs the north with nr normal temps for Downeast.
By Wed evening H5 low wl thru the the mid-Atlantic states with sfc
low positioned just off of the Virginia Capes by 00z Thu. It wl move
into the Atlantic drg the overnight hours with ridge of high
pressure preventing much in the way of rain fm the coastal low
impacting our area with the exception of far srn zones. With the upr
trof linger over rmndr of the area expect that isold-sctd showers
could develop at anytime Thu aftn with a little bit of diurnal
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Models begin to go off the rails at the start of the long term due
to upr lvl pattern. 12z EC much more progressive with the upr low
ovr the northeast over the weekend with GFS hanging it back until
later Sunday. At the sfc this leads to strong low pressure crossing
the NY Bight Fri evening with GFS keeping it offshore and only
bringing pcpn onto Downeast coast Fri night into Sat morning.
Meanwhile latest EC brings 984mb sfc low thru srn Maine by 12z
Saturday bringing pcpn into the entire area Fri night and Saturday.
Due to the discrepancies have capped pops at 50% but cannot rule out
wintry pcpn, mainly at higher elevations on Saturday morning. Still
plenty of time to make adjustments as model come more into line with
one another over the week. Upr trof wl continue to swing thru the
northeast part of the U.S. with chc pops continuing thru the end of
the long term. Blo normal temps wl continue into early next week and
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Northern TAF sites with rain showers will transition
to a mix of rain and snow this evening and overnight. FVE will
continue to go in and out of MVFR/IFR ceilings before trending
towards MVFR after midnight. KCAR and KPQI will also see some
snow mix in as ceilings go low MVFR or IFR tonight. Further
south, precip will remain rain with BGR and BHB expected to
remain VFR with winds increasing from the NW.
VFR at the Downeast terminals Tue with MVFR at the northern Taf
sites in Aroostook County, with brief IFR possible in any
Tue night...MVFR in the evening at Downeast terminals improving
to VFR after midnight. Northern terminals remaining MVFR thru
daybreak Wed. NW 5-10kts.
Wed-Thu....Mainly VFR at all terminals. N 5-10kts gusting to
15kts Wed afternoon becoming light N Wed night then N 5-10kts
Thu night...VFR dropping to MVFR by Fri morning at all
terminals. Lgt winds.
Fri-Sat...Very low confidence in this period with vsby
restrictions expected Friday into Friday night in -ra or light
NEAR TERM: Wave heights will remain below SCA criteria, but NW
winds will gust around 25 kts late tonight through Tuesday
morning and a small craft advisory is in effect for the coastal
SHORT TERM: Winds and seas below SCA levels through the period.
May see swell move in later Friday ahead of potential low
pressure system over the outer waters.
MARINE...Small Craft Advisory until 11 AM EDT Tuesday for ANZ050-051.
Area Forecast Discussion
National Weather Service Wilmington NC
815 PM EDT Mon May 4 2020
Low pressure approaching from the west will track over a remnant
front, to produce morning showers across the area. A stronger
front will cross the coast Wednesday, opening the door to cool
Canadian high pressure Thursday into Friday. Another cold front
arriving Friday night will bring even cooler air this weekend.
No significant changes as yet, convection will increase late
tonight as an impulse approaches, teaming up with a remnant
surface boundary, which it will pull northward as well, over
the area into early Tuesday, mainly from 4am-9am before moving
north and east of the area, including the remnant front. Will
retain TSTMs as instability aloft will be present, and the
added contribution from low-level frontal convergence. Outside
of convection, low level winds relatively light, so any severe
threat, would remain localized early Tuesday.
.NEAR TERM /THROUGH TUESDAY NIGHT/...
Dry cold front continues to push south across SC this afternoon but
it is expected to stall by this evening. HRRR has consistently shown
scattered showers and a few tstms moving across primarily the
northern zones overnight into Tuesday morning. This activity is
likely a result of an impulse aloft coupled with the lingering H925-
850 boundary expected to be draped across the forecast area. Have
bumped POPs upward in these areas during this time as a result. The
warm front may struggle moving quickly to the north during Tue with
a wedge-like pattern in place across NC but will likely make a
better push to the north as low pressure moves from the western
Carolinas to the eastern Carolinas by Tuesday night. Decent spread
between MAV/MET numbers given positioning/timing of the warm front.
Currently favor a blend toward the warmer MAV numbers.
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Cold front poised to push offshore Wed AM, commencing a period of
cooling and drying. Wed may end up being a relatively nice day.
Although the front moves offshore in the morning the cold advection
does not ramp up until Wed evening, when the 5h trough arrives. Once
the cold air arrives it will do so with authority. Temps near climo
Wed will tumble Wed night. Lows will end up some 12 to 15 degrees
below climo, even with northerly winds 10 to 15 mph. Cold advection
shuts off on Thu, but not even the high May sun angle will help.
Highs will struggle to hit 70 with most areas 10 to 12 degrees below
climo. Air mass starts to modify Thu as surface high, west of the
area, shifts southeast. Temps Thu night still end up well below
climo, but weak return flow setting up may be enough to take the
edge off the cold. Skies will be clear, but a bit of southerly wind
will keep radiational cooling from being maximized. Lows will once
again end up in the mid 40s, 10 to 15 degrees below climo.
.LONG TERM /FRIDAY THROUGH MONDAY/...
High pressure off the coast Fri will setup a brief period of warm
advection, with highs approaching climo. The warm up will be short
lived with a strong cold front crossing the area Sat night,
accompanied by scattered showers and possibly an isolated
thunderstorm. High pressure will follow the front building into the
region Sat, moving overhead Sat night and Sun, then offshore for Mon.
- Only rainfall chances will be Fri evening, ahead of Fri night
- Temperatures well below climo for the weekend with potential
for lows in the 30s in places Sun morning.
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Brief period MVFR ceilings possible 9z-15z, coincident with
warm front showers lifting to the north and east, clearing
trends aft 16z. Veering winds today, but 12 kt or less overall.
Isolated TSTMs possible embedded in showers, some could be
strong. NE winds 4-9 kt tonight near end of TAF cycle.
Extended Outlook...MVFR ceilings Wednesday. VFR returns
Thursday and holds into the upcoming weekend.
A cold front will stall across the SC waters this evening, then lift
northward during Tuesday through early Wednesday as low pressure
migrates from the western Carolinas to off the VA/NC coasts. As a
result, veering winds are expected around 10 knots with seas 3 ft or
less with the boundary stalled nearby. Speeds will increase again
from the SW with warm frontal passage with potential Small Craft
Advisory thresholds met Tuesday night in a SW fetch with choppy 4-6
ft seas. Scattered showers and a few tstms are possible, especially
for the Cape Fear waters Tuesday morning. Additional chances of
showers/tstms as the warm front lifts northward later Tuesday and as
low pressure moves across eastern NC Tuesday night before shifting
Cold front moves east of the waters early Wed with offshore flow in
place Wed and Thu. Cold air is delayed until Wed night, with speeds
Wed running 10 to 15 kt. Once the cold air arrives the offshore flow
will pick up with potential for period of solid 20 kt at times Wed
night and Thu. Surface high passes south of the area Thu night with
light return flow Fri morning. Southwest winds will increase during
Fri ahead of next cold front, crossing the waters late Fri night.
Offshore flow sets up Sat as high builds in behind the front.
Although cold advection is significant, gradient is rather weak.
Offshore flow will be on the low end of the 10 to 15 kt range but
could see gusts in excess of 20 kt at times. Seas 3 to 4 ft Wed
build to 3 to 5 ft Wed night and Thu as offshore flow ramps up. Seas
drop to 3 to 4 ft Fri and 2 to 3 ft Sat as wind speeds drop off.
Area Forecast Discussion
National Weather Service Blacksburg VA
1008 PM EDT Mon May 4 2020
Warm air riding over the top of high pressure wedging down east of the
mountains will bring widespread rainfall to the Appalachians and
central mid Atlantic region late tonight and Tuesday. High pressure will
then bring cool but quiet conditions to locations east of the Blue
Ridge through midweek, but conditions in the mountains will remain
chilly and unsettled with a chance of showers just about each
day through Friday.
.NEAR TERM /THROUGH TUESDAY/...
As of 1008 PM Monday...
Made a few adjustments in temperatures for tonight into Tuesday
morning. This evening 00z rnk sounding showed a very dry airmass
in place with pwat 0.35 ins. Low temperatures overnight will
vary from the upper 30s in the mountains to the lower 50s along
the southern Blue Ridge mountains. Moisture will slowly increase
tonight as high pressure wedges down the eastern slopes of the
Appalachians. Have the onset of the rain showers around 2 to 3
am Tuesday morning in the west and then spread rain east across
forecast area. The Day 2 Convective Outlook highlights a
marginal threat of severe for portions of the western
mountains. The main threats will be gusty winds, hail and
locally heavy rains. The latest HRRR and NAM still support the
potential for a thunderstorm basically west of I77. Questions
remain whether clouds and rain will hinder instability and
thunderstorm development. High temperatures Tuesday will range
from the mid 40s in the cool wedge to around 60 degrees in
As of 805 PM Monday...
Made some minor adjustments in temperatures for this evening
into tonight utilizing the latest surface obs, their trend and
blended in the NBM. Low temperatures overnight will range from
the upper 30s in the mountains to the lower 50s along the
southern Blue Ridge mountains. Moisture will slowly increase
tonight as high pressure wedges down the eastern slopes tonight
into Tuesday morning. Kept the onset timing of rain Tuesday
morning,then spread it eastward during the day. More later
As of 155 PM EDT Monday...
After a pleasant evening, our brief period of pleasant weather will be
coming to an end late tonight as high pressure wedges down east of the
mountains and strong isentropic lift over the wedge generates
widespread rainfall from the predawn hours into Tuesday. Can not rule
out some elevated convection producing a rumble or two of thunder as
well. It currently looks like the rainfall amounts will be spread out
over a long enough period of time to limit potential hydro issues, so
will not issue any headlines and monitor later guidance closely.
As Tuesday wears on, some deeper convection may develop outside of the
wedge to our west where some surface based instability will develop.
This convection will then start pushing into the region early Tuesday
evening and may have a small amount of unstable air to work with in our
neck of the woods to present a severe threat as it encounters enhanced
shear along the western periphery of the wedge. Confidence is not high
that the convection will maintain itself as it pushes in and believe
the greater threat will reside just a bit further upstream as indicated
in the SPC day 2 outlook. Nevertheless, will be monitoring later runs
of meso guidance closely to see if the situation changes.
Lows tonight will generally be in the 40s. Temperatures Tuesday will be
well below normal in the wedge with some locations in the heart of the
wedge simply remaining in the 40s throughout the day, but low/mid 50s
down around the VA/NC line and lower 60s far west.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 155 PM EDT Monday...
Precipitation will remain ongoing for the start of this forecast
period with a trough`s surface front exiting the area early
Wednesday morning. As discussed in the near term discussion, with
little remaining instability left, its not likely that deeper
convection will persist into this period and make it beyond the far
SW mountains, but confidence in this is not absolute.
While the front will be gone, showers will remain possible for the
west Wednesday as the trough pivots over the region. As the day goes
on, moisture will become more confined to just the far NW slopes.
With dropping temperatures behind this system, don`t be surprised to
see a few flakes in the higher elevations before moisture shuts off.
Thursday remains cool as sunshine and dry weather return with
continued NW winds. For now, temperatures will remain above
freezing, meaning no freeze warning needed for the west. Likewise,
the wind will help scrap any formation of frost. That said, look for
average to below average temperatures through the period with ample
cloud cover, showers, and NW winds.
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 155 PM EDT Monday...
The cool weather pattern that starts mid work week is set to remain
in place with continued pattern amplification. A trough arriving
late Thursday will bring a first shot of rain for the period through
Friday. This trough looks to be the deepest digging at the moment,
bringing the coolest temperatures. That said, has the saying changed
to, "May snow showers bring June flowers"? It looks like
temperatures should drop fast enough as moisture lingers to bring
more widespread snow showers for those west of the BLue Ridge Friday
night into Saturday AM. Accumulation amounts are foggy at this
point, but presumably any accumulation will remain confined to the
western slopes at higher elevations, and even there accumulations
will be low. With the snow will likely come freeze headlines as
temperatures will drop below freezing west of the Blue Ridge.
Continued NW flow Saturday into Sunday will keep temperatures well
below average. Guidance suggests that winds will die off as PGF
decreases, meaning that a widespread frost/freeze is of concern.
Heading out of the weekend and into the work week, continued
unseasonal pattern amplification means more chances for rain and
cooler than usual weather. However, Monday looks to bring some
warming recovery with it thanks to a SW wind setting in ahead of a
new disturbance that will arrive outside of the forecast period
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 735 PM EDT Monday...
Expect VFR conditions all sites through 06z Tuesday. Late
tonight into Tuesday morning, conditions will trend to MVFR/IFR
toward daybreak as low clouds and precipitation develop
courtesy of warmer air running over high pressure wedged down
east of the mountains. IFR/LIFR conditions in low clouds,
rain, and some fog will prevail Tuesday into Tuesday night.
An Isolated thunderstorm may be possible west of I77.
Winds will diminish with loss of heating this evening into
tonight. Will start to see northeasterly flow pick up toward
daybreak especially east of the mountains at KLYH and KDAN.
High confidence in ceilings, visibilities and winds during the
Extended Aviation Discussion...
Unsettled weather lingering into at least Tuesday night, with
sub-VFR cigs/vsbys and rain. Anticipate scattered showers across
the mountains and foothills into Wednesday with sub-VFR likely
in the mountains through Wednesday evening. High pressure
arrives Wed night-Thu for VFR before front moves in with more
shower chances Friday though mostly expecting VFR with some MVFR
in the mountains. Drier weather is expected Saturday.